Dissertations / Theses on the topic 'Soil nailing'

COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
A utilização de inclusões passivas para reforços de solos, técnica comumente conhecida como solo grampeado, vem tendo aceitação crescente junto a profissionais de engenharia civil, em especial no Rio de Janeiro. Esta técnica, porém, carece de um estudo detalhado sobre a influência dos parâmetros relevantes na deformabilidade de maciços grampeados. Os grampos são inclusões rígidas, instaladas suborizontalmente, sem tensão ou trecho livre, pois as barras de aço são introduzidas em um furo preenchido com calda de cimento. As forças axiais nos grampos são obtidas através da descompressão lateral causada pela escavação do solo. O grampeamento é feito na massa de solo à medida que escavações são executadas em etapas, obtendo se uma zona reforçada que atua como suporte da massa de solo posterior, sem reforço. A face frontal da escavação é usualmente protegida por concreto projetado, sem funções estruturais. Esta pesquisa objetiva avaliar a influência dos diversos parâmetros geotécnicos e geométricos no comportamento tensão deformação de escavações grampeadas com face vertical e superfície do terreno horizontal. A análise paramétrica foi realizada pelo FLAC (Fast Lagrangian Analysis of Continua) que é um programa computacional baseado no método das diferenças finitas. Este programa simula o comportamento bidimensional de estruturas reforçadas, constituídas de solo e ou rocha, que possam ser submetidos a escoamento plástico quando o limite de resistência é atingido. Os resultados mostram que o módulo de Young (E) e a coesão do solo (c) são de grande relevância para o projeto de estruturas grampeadas. Adicionalmente, as análises indicam que a resistência ao cisalhamento na interface solo-grampo (qs) é também um parâmetro importante, particularmente nos casos com grampos de comprimento (L) inferior a 80 por cento da profundidade de escavação (H) (L/H < 0,80). Recomenda-se que o valor de qs seja determinado diretamente a partir de ensaios de arrancamento no campo. No que se refere à inclinação dos grampos, os resultados mostram que não há diferenças significativas nos deslocamentos do maciço reforçado para lambda menor ou igual a 10 graus. Estes resultados são particularmente interessantes do ponto de vista de execução, pois inclinações da ordem de 10 graus facilitam os procedimentos de injeção no campo. Os resultados obtidos nesta pesquisa indicam o uso de comprimentos de grampos maiores que 70 por cento da altura de escavação (L/H > 0,70) na técnica do solo grampeado.
The use of passive inclusion for soil reinforcements, technique usually known as soil nailing, has been gaining growing acceptance within civil engineering professionals,especially in Rio de Janeiro. However this technique lacks a more detailed study on the elevant parameters influencing the deformability of soil nailed masses. The nails are rigid inclusions, sub horizontally positioned, without tension or free space between the nail and the surrounding soil mass. The axial forces on the nails are developed due to lateral decompression caused by soil excavation. As the excavation stages proceed, the nails are successively being installed, producing a reinforced zone, which acts as a support for the soil mass. The frontal face of the excavation is usually protected by shotcrete, and has no structural functions. This research aims at evaluating the influence of the various geotechnical and geometric parameters on the stress strain behavior of nailed excavations, with vertical face and horizontal soil surface. The parametric analysis was performed using FLAC (Fast Lagrangian Analysis of Continua), which is a computer program based on the finite difference method. This program simulates bi dimensional behavior of reinforced structures of soils and or rocks,which may be submitted to plastic flow when the strength limit is reached. The results show that the Youngs modulus (E) and soil cohesion (c ) have a very significant influence on the displacement of a soil nailing structure. The analysis also indicates that the mobilized shear strength at the soil nail interface (qs) is also an important parameter, particularly for nail lengths (L) smaller than 0,80 of the excavation height (H) (L/H < 0,80). It is therefore recommended that qs be directly determined by pullout in situ tests. Regarding nail inclination the results suggests no significant influence on the reinforced soil mass displacement for alpha less or equal than 10 degrees. These results are particularly relevant for engineering practice, because a 10 degrees inclination facilitates grouting injections in the field. The results in this research indicates the use of nail lengths (L) greater than 0,70 of the excavation height (H) (L/H greater than 0,70) in soil nailing technique.

This dissertation is concerned with a study of soil nailing, in particular the interaction mechanism between the soil and a nail and the failure mechanism and suitable design procedure for nailed slopes in sand. The interaction mechanism of a nail was studied by carrying out a number of pull-out tests, direct shear tests of nailed sand and interface tests using two uniform sands. Major parameters of the tests were flexibility, surface roughness and diameter of a nail. From the tests, it was found that: (1) flexibility of a nail significantly influences the interaction mechanism. Both the interaction parameter and apparent friction coefficient differ between a flexible and a stiff nail. Theoretical consideration indicates that the mobilization of nail forces is dominated by the relative stiffness between soil and nail. (2) a smooth-surface nail produces smaller bond friction than the critical state friction angle and mineral-to-mineral angle of the soil. This is due to the very thin rupture surface developed around the nail. On the other hand, a rough-surface nail was observed to produce two to four times larger bond friction than the direct shear friction angle of sand, due to the thick rupture surface developed and the dilatancy of the soil. (3) increasing the diameter of a nail produces a smaller apparent friction coefficient. Restrained dilatancy was found to play an important role. (4) the pull-out test, direct shear test of nailed sand and interface test produce different values of apparent friction coefficient , due to the different amount of restrained dilatancy effect around the nail (or reinforcement). The overall behaviour of nailed slopes was studied by carrying out a comprehensive series of centrifuge tests. Excavation of soil was simulated by draining water from two rubber bags in front of the facing wall. The centrifuge tests have provided much useful information on the mechanics of soil nailing. From the tests, it was found that: (1) draining of the water significantly influences both the earth pressure on the facing wall and the displacements of the nailed slope. Horizontal displacements of the facing wall were decreased by increasing the length and/or friction (bond) of the nail. (2) earth pressures on the facing wall do not exhibit a simple hydrostatic distribution. The deviations of the earth pressure are not negligible especially near the top and bottom of the facing wall. (3) roughness and bending stiffness of the facing wall considerably influence the stability and displacement of the nailed slope, respectively. (4) the observed failure surfaces were well described by a logarithmic spiral passing through the toe of the facing wall. (5) fairly good predictions for the failure acceleration were made using stability analysis of the nailed slopes based on the limit equilibrium method, provided an accurate friction angle for the sand and pull-out resistance of each nail could be determined. The factor of safety F5 of the nailed slopes was estimated by comparing the total available force and the total required force based on the observed failure surfaces.

Past studies on soil nailing have a common assumption that a soil nail could be simplified as a single material solid cylinder. However, a soil nail is a composite material and consisted of the following basic components: steel bars, cement grout, PVC centralizers, steel couplers, and a plastic hose, etc. They are combined and work together to keep the fundamental functions in soil reinforcement. Since these components are made by various constituent materials, the physical and mechanical properties of them are greatly different, making the deformations through soil nail diverse. The different deformations could be incompatible, which has significant effects on the soil nail integrity and performance due to the intrinsically existing vulnerable areas. One critical issue is the key component cement grout sleeve, functioning as the adhesive to transfer stress between the ground and steel bar, may encounter tensile failure on the out-layer surface or along the interface between steel bar and itself. The consequence would be cracking and detachment of cement grout and then malfunction of soil nails. Therefore, it is of great importance to examine the mechanical behavior of soil nails by taking into account the behavior of the different components. In this research extensive laboratory tests have been carried out to examine and quantify the mechanical properties of soil nail’s each component as well as their simple combinations. Based on this, a series of physical modeling of soil nail in tension and bending tests are designed to simulate the deformation of soil nail under loading. The characteristics of soil nail’s overall behavior and cracking initiation/propagation in cement grout are observed and interpreted. Besides, two soil nail’s component replacement trials based on the conventional design are conducted with attempt to enhance the overall soil nail strength and facilitate the installation procedure. A new concrete mix design with fine aggregates (sands) is adopted to substitute the neat cement grout for minimizing the local failure in cement column. Optimum sand ratio which is sound for postponing the cracking is evaluated as well. Another trial is the application of hollow core steel bar in place of the solid one. Compared to the traditional drill-and-grout soil nailing method, this new technology has advantages of fewer installation steps through a self-grout method. Similar laboratory tests are done to exam the impact on soil nail’s capacity from this change and preliminarily evaluate the feasibility of using of hollow core steel bar in practice.
published_or_final_version
Civil Engineering
Master
Master of Philosophy

COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
Deformabilidade e estabilidade de taludes em solo grampeado são aspectos relevantes na utilização deste sistema de reforço de taludes naturais ou resultantes de processo de escavação. A concepção do projeto envolve a escolha do comprimento, ângulo de instalação, espaçamento e resistência dos grampos. O dimensionamento, usualmente baseado na teoria do Equilíbrio Limite, não consegue prever deformações no interior da massa grampeada, assim como a redistribuição de esforços nos grampos ao longo das diversas etapas de escavação. Estas informações podem ser obtidas por modelagem computacional com o auxílio do programa FLAC, de forma a definir critérios de projeto para massas grampeadas em solo residual. Para escavações de baixa altura (inferiores a 5m), a razão entre comprimento do grampo e altura da escavação deve ser superior a 0,7 e a razão entre espaçamento vertical e comprimento do grampo inferior a 50%. Para escavações maiores, a razão entre espaçamento vertical e comprimento do grampo deve ser inferior a 25%. Para estas condições não é observada uma configuração de colapso do talude em solo grampeado. O ângulo de rotação da face da escavação é um parâmetro importante no projeto. Adicionalmente verifica-se que uma pequena variação na geometria, condições de contorno, modelo constitutivo e parâmetros do solo e do grampo causam mudanças expressivas nos valores de deslocamento, tensões iniciais e esforços axiais nos grampos. Uma pequena variação da inclinação do talude pode acarretar reduções de até 70% nos deslocamentos finais. Os esforços axiais máximos, mobilizados em cada grampo durante o processo de escavação, são maiores nos taludes mais íngremes.
Deformability and stability of slopes supported by soil nailing are relevant aspects in the utilization of this reinforcement system during excavation. The project concept involves choosing the installation angle, spacing, and resistance of the soil nails. The parameters, usually determined from Limit Equilibrium Theory, cannot predict the deformation of the reinforced mass or the redistribution of stresses on the nails throughout the excavation stages. This information was obtained through computer modeling using the FLAC Program, which defined the performance of soil nailing masses in residual soil. For shallow excavations (H < 5m), the ratio between length and excavation height must be a minimum of 0.7, the ratio between spacing and length up to a maximum of 0.5. For higher excavations, the ratio between spacing and length has to be reduced to 0.25. The rotation angle of the excavation s face is an important parameter. Additionally, small variations in the geometry, boundary conditions, constitutive model, and soil and nail parameters, can cause large changes in the deformations, initial tensions and axial stresses in the nails. Regarding the slope inclination, a small variation can cause reductions of up to 70% in the final deformations. The maximum axial stresses mobilized in each nail during the process of excavation are larger in steeper slopes.

Thesis (M.S.)--West Virginia University, 2007.
Title from document title page. Document formatted into pages; contains xii, 86 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 80-82).

The subject of this thesis is the design of a local road cut off in the resort Hálův mlýn located in the cadastral of municipality Lažánky, Brno-venkov district, South Moravian Region. The thesis contains static calculation and design documentation.

The research described in this thesis focussed on the bond resistance of grouted soil nails in clay. Physical modelling took the form of large scale element tests in the laboratory of drilled and grouted nails in a stiff clay. Nails were installed under different boundary stresses; testing was conducted at different constant rates of pull-out and also under sustained load conditions. Observed behaviour was compared with that predicted by measurements of interface shear resistance obtained in a conventional shear box. Numerical modelling was carried out in an attempt to improve understanding of the effects of installation processes on nail performance, and to investigate the trends in behaviour observed during laboratory tests. For this purpose, a one-dimensional finite element computer program was developed to include the effects of consolidation and the out-of-plane soil displacements associated with nail axial loading. The physical modelling showed that the loading rate has a significant effect on bond resistance. This has consequences for the interpretation of data from constant rate of displacement pull-out testing, the conventional method of verifying bond resistance in the field. It is suggested that this type of testing is inappropriate in low permeability soils, because capillary suctions develop which lead to increased bond resistance. Results from laboratory sustained load tests show that lower values of bond resistance are mobilised under the static load conditions more likely to exist in a real soil nailed structure. The numerical modelling confirms the behaviour observed during the laboratory tests, and shows that the mechanisms by which bond is mobilised are complex, depending critically on the dilation and consolidation characteristics of the soil. Nail installation procedures are modelled, and grout pressures are shown to strongly influence bond resistance. Interface tests show trends in behaviour similar to those observed during pull-out testing. However, difficulties exist in the qualitative use of interface test data to predict nail bond resistance.

Dentre as técnicas de reforço de solos, o solo grampeado têm se destacado em âmbito mundial devido a sua versatilidade e eficiência na estabilização de taludes de escavação por meio do reforço do solo \"in situ\", através da introdução de gramposno meio a ser estabilizado. A resistência ao cisalhamento na interface solo-grampo é um dos parâmetros mais importantes a serem analisados. Esta pode ser obtida por meio de ensaios de arrancamento. No entanto, como estes ensaios devem serexecutados durante a execução das obras, existe uma grande aplicação de estimativas da resistência por atrito lateral, baseada em correlações empíricas. Este trabalho realiza a previsão da resistência ao cisalhamento da interface solo-calda quefoi avaliada experimentalmente por meio de ensaios de cisalhamento direto realizados em laboratório. Estes ensaios permitiram uma análise dos parâmetros de resistência dos solos (c e \'fi\') e das interfaces solo-calda. Adicionalmente, foramelaborados traços alternativos de caldas solo-cimento de modo a avaliar sua aplicabilidade na técnica de solo grampeado. Os resultados permitiram constatar que o uso de solo-cimento em substituição a calda de cimento convencional é viável, vistoque os resultados apresentaram um ganho de resistência ao cisalhamento de interface. Os valores de resistência de interface obtida em laboratório apresentaram resultados próximos aos valores de campo, obtidos a partir da realização dos ensaiosde arrancamento em obras distintas.
Among the techniques to enhance soil, the nailing soil have been highlighted in the world due to its versatility and efficiency in the stabilization of excavation\'s slopes by means of the strengthening of the soil in situ by the introduction ofnails in the environment that it wanted to stabilize. The shear strength at the interface soil-nailed is one of the most important parameters to be analyzed. This can be obtained by pullout testing. However, these tests should be performedduring the construction activities, there is a great application of estimates of resistance by lateral friction, based on empirical correlations. This study evaluates the prediction of the strength to shear in the soil-grout interface which was experimentally evaluated by means of direct shear tests performed in the laboratory. These tests allowed an analysis of the parameters of resistance of the soils and of the soil-grout interfaces. Additionally, it was developed alternative batches of soil-cement grouts to assess its applicability in the technique of soil nailing. The outcomes allowed conclude to the use of soil-cement in place of the conventional cement grout is feasible, because the results presented aconsiderable gain in shear strength of interface. The values resistance of the interface obtained in the laboratory showed similar results to the values of the field, obtained from the pullout testing in different construction sites.

[ES] La técnica de "Soil Nailing" es un procedimiento de refuerzo del terreno utilizado continuamente en la estabilización de taludes y cortes del terreno en proyectos de ingeniería geotécnica. Esta técnica se aplica con frecuencia en la ciudad de Quito (Ecuador) para el refuerzo del terreno, mejorando la estabilidad de los taludes, durante el proceso de excavación de varios niveles de sótanos. Estas excavaciones de gran profundidad son habituales en proyectos inmobiliarios importantes de la ciudad, en los que el "Soil Nailing" se emplea con algunas variantes que la ajusten a los recursos constructivos disponibles en el medio. Pese a lo extendido de su uso, esta técnica, que ha resultado ser efectiva para estabilizar las excavaciones durante los procesos constructivos de estructuras de sótano en los suelos de la ciudad de Quito, actualmente dispone de pocas investigaciones locales, ya sean teóricas, numéricas o experimentales, basadas en las propiedades geotécnicas de los suelos volcánicos característicos de la ciudad. Esta Tesis Doctoral que contó con el soporte del Laboratorio de Ingeniería Geotécnica y el Laboratorio de Estructuras del Instituto de Ciencia y Tecnología del Hormigón (ICITECH) de la Universitat Politècnica de València presenta un estudio experimental y numérico del comportamiento de dos excavaciones reforzadas con la técnica de "Soil Nailing" para la construcción de las estructuras de sótano de dos importantes edificios ubicados en la zona centro-norte de la ciudad de Quito. Tanto el estudio experimental como el numérico se enfocan principalmente en la evolución de las fuerzas de tensión en las barras de acero de los "Soil Nails", el análisis de desplazamientos horizontales de las pantallas y el análisis de asentamientos en el terreno que se encuentra detrás de las pantallas y que fueron inferidos por la construcción de cada nivel de sótano. Como parte del análisis numérico a través de elementos finitos se han considerado diferentes modelos constitutivos de suelo, cuyos parámetros se determinaron detalladamente de acuerdo a los ensayos de laboratorio del estudio de caracterización geotécnica de esta investigación. Por tanto, esta Tesis Doctoral constituye una de las primeras investigaciones completas de la región encaminada a explicar el comportamiento experimental y numérico de excavaciones mediante la técnica de "Soil Nailing" y respaldada con un completo trabajo de caracterización geotécnica, llevado a cabo a propósito como parte de este estudio.
[CA] La tècnica de "Soil Nailing" és un procediment de reforç del terreny utilitzat contínuament en l'estabilització de talussos i talls del terreny en projectes d'enginyeria geotècnica. Esta tècnica s'aplica ben sovint en la ciutat de Quito (Equador) per al reforç del terreny, millorant l'estabilitat dels talussos, durant el procés d'excavació de diversos nivells de soterranis. Estes excavacions de gran profunditat són habituals en projectes immobiliaris importants de la ciutat, en els que el "Soil Nailing" s'empra amb algunes variants que l'ajusten als recursos constructius disponibles en el mig. A pesar d'allò que s'ha estés del seu ús, esta tècnica que ha resultat ser efectiva per a estabilitzar les excavacions durant els processos constructius d'estructures de soterrani en els sòls de la ciutat de Quito, actualment disposa de poques investigacions locals, ja siguen teòriques, numèriques o experimentals basades en les propietats geotècniques dels sòls volcànics característics de la ciutat. Esta Tesi Doctoral que va comptar amb el suport del Laboratori d'Enginyeria Geotècnica i el Laboratori d'Estructures de l'Institut de Ciència i Tecnologia del Formigó (ICITECH) de la Universitat Politècnica de València presenta un estudi experimental i numèric del comportament de dos excavacions reforçades amb la tècnica del "Soil Nailing" per a la construcció de les estructures de soterrani de dos importants edificis ubicats en la zona centre-nord de la ciutat de Quito. Tant l'estudi experimental com el numèric s'enfoquen principalment en l'evolució de les forces de tensió en les barres d'acer dels "Soil Nailing", l'anàlisi de desplaçaments horitzontals de les pantalles i l'anàlisi d'assentaments en el terreny que es troba darrere de les pantalles i que van ser inferits per la construcció de cada nivell de soterrani. Com a part de l'anàlisi numèrica a través d'elements finits s'han considerat diferents models constitutius de sòl, els paràmetres de la qual es van determinar detalladament d'acord amb els assajos de laboratori de l'estudi de caracterització geotècnica d'esta investigació. Per tant, esta Tesi Doctoral constituïx una de les primeres investigacions completes de la regió encaminada a explicar el comportament experimental i numèric d'excavacions per mitjà de la tècnica del "Soil Nailing" i protegida amb un complet treball de caracterització geotècnica, dut a terme a propòsit com a part d'este estudi.
[EN] The "Soil Nailing" technique is a ground reinforcement procedure used consistently to stabilize slopes and land sections in geotechnical engineering projects. This technique is frequently used in the city of Quito (Ecuador) to reinforce the ground and improve slope stability during the excavation process for various underground parking levels. Such deep excavations are common in the city's most important real estate projects, in which "Soil Nailing" is used with different variations that are adjusted in accordance with the construction resources available in the particular environment. Despite its widespread use, this technique which has proven to be so effective in stabilizing excavations during the construction of underground structures in the soils of the city of Quito, currently suffers from a lack of local theoretical, numerical or experimental research based on the geotechnical properties of the city's characteristic soils. This Doctoral Thesis was supported by the Geotechnical Engineering Laboratory and the Structures Laboratory of the Concrete Science and Technology Institute (ICITECH) of the Universitat Politècnica de València. It presents an experimental and numerical study of the behavior of two excavations reinforced with the Soil Nailing technique for the construction of the basement structures of two important buildings located in the north-central area of the city of Quito. Both the experimental and the numerical study focus mainly on the stress of tension forces exerted on the steel bars of the "Soil Nails", analysis of horizontal wall displacements and analysis of settlements of the ground behind the walls, which were induced by the construction of each underground level. As part of the numerical analysis through finite elements, different constitutive soil models were considered, the parameters of which were determined in detail in accordance with laboratory testing from the geotechnical characterization study for this research. This Doctoral Thesis, therefore, constitutes one of the first complete studies in the region aimed at explaining the experimental and numerical behavior of excavations through the Soil Nailing technique, supported by complete geotechnical characterization work which was carried out for the purpose of forming part of this study.
Capa Guachón, VE. (2021). Estudio experimental y numérico del comportamiento de excavaciones ejecutadas mediante la técnica de suelo claveteado (soil nailing) en suelos de la ciudad de Quito (Ecuador) [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/164174
TESIS

O uso de sistemas de faceamento flexíveis com malhas metálicas é uma alternativa viável ao uso do concreto projetado como faceamento em sistemas de solo grampeado. Vários modelos de malhas são empregados hoje para este uso, sendo classificados pela resistência à tração no sentido longitudinal. Mesmo que relevante, segundo Cala et al., (2012), somente este dado é insuficiente para o correto dimensionamento destas soluções. A presente pesquisa busca identificar quais os parâmetros de resistência são necessários para o dimensionamento de um faceamento em malha metálica. Para tanto foram avaliadas duas metodologias desenvolvidas especificamente para as malhas aplicadas junto com a solução de solo grampeado, os métodos Ruvolum e Macro1. Foram então desenvolvidos equipamentos, similares aos utilizados por Roduner (2011) e Cala et al. (2012), para caracterizar 4 diferentes modelos de malhas, avaliando a resistência das mesmas frente aos esforços considerados nos modelos de cálculo investigados, tração e o cisalhamento no contato malha/grampo. Deste modo, foram utilizados resultados de ensaios em escala real com a simulação de um talude em solo tratado com as 4 malhas, para a validação dos métodos de dimensionamento, e para investigar quais os parâmetros de resistência da malha são mais importantes. Como resultado foram determinadas as resistências das malhas avaliadas, sendo a de tração no sentido longitudinal entre 50 e 140 kN, e a resistência no contato malha/grampo, que variou entre 10 e 30 kN. Por fim foi realizada uma análise paramétrica com o método Ruvolum a fim de verificar a influência na variação da coesão, espessura instável e ângulo de atrito, dados nem sempre bem definidos em projeto. Os resultados mostram, como era esperado, a grande sensibilidade da variação nos resultados frente aos efeitos da coesão, sendo então recomendado, como em qualquer análise de estabilidade cautela no uso deste parâmetro. A análise destes resultados permite concluir que o método mais adequado para modelar um talude em solo grampeado com face em tela foi o Ruvolum, com previsões que se aproximaram das medições reais dos ensaios de campo.
The use of flexible facing systems with steel meshes is a viable alternative to the use of shotcrete as facing in soil nailing systems. Currently several different models meshes are being used today for this purpose, being classified only by the tensile strength in the longitudinal direction of the mesh. Even though this parameter is quite relevant, alone it cannot be used to design the flexible facing systems. So this research aims to identify which steel mesh strength parameters are really needed for the correct dimensioning of such solutions. In order to do so two calculation methodologies, specially developed for steel meshes design, were investigated. The design models are called Ruvolum and Macro1 Equipments were developed, similar to those presented in Cala et al. (2012), to investigate four different models of mesh, in order to find the strength parameters presented on the studied calculation models, being than tensile and shear. Thus, to validate the investigated design methodologies, field tests results were compared to the models predictions. As product of the research it was possible to determine the tensile strength of the 4 meshes models, being then ranging from 50 and 140 kN. Also it was possible to define the shear resistance in the nail head/mesh contact, which ranges from 10 to 30 kN. The last step of the research was a parametric analysis, performed with the Ruvolum method to evaluate the influence on the variation of cohesion, unstable thickness and friction angle in the predictions, since this data aren’t always available in ordinary projects. These analysis have showed that the most influent parameter is cohesion, one that is very hard to determine. Also it was found by the results analysis that the appropriate calculation model to simulate a slope stabilized with soil nail and steel meshes facing is the Ruvolum, due the closeness of the predictions to the real field data.

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The use of soil nailing technique can be an important alternative for the stabilization of a slope or an excavation. Nails are retaining elements that reinforce soil masses acting passively, requiring strains to mobilize their resistance. The mechanical behavior analysis of a structure with soil nailing technique can be made using limit equilibrium methods, being represented by loads applied to reinforcing layers or sub-horizontal slices of a slope. The slice has its base crossed by a reinforcing action line and the reinforcing nail is treated as a concentrated point load acting on the base point of intersection of a slice with the line of action. Thus, through analytical and numerical calculations, this dissertation studied the design of soil nailing structure considering variations of suction, which influences the soil resistance, simulating suction profiles of a typical soil of the Brazilian Midwest region. This study was conducted determining strength parameters on nail-soil interface by tests in the field, i.e. nail pullout tests, and soil strength and hydromechanical parameters determined in the laboratory. For this, two separate suction sections were studied, and in each case, numerically analyzed in soil nailing structures, obtaining the dimensions of the structure through a pre-sizing phase, and then analyzing the factor of safety of the structure using computer programming considering the Bishop method. In the first case, the distribution of suction was numerically simulated for the soil profile studied in a critical condition of rainfall in Goiania region. Then, the suction field profile was obtained for comparison with the first case. With the results of this research, it was possible to understand the increasement of resistance and safety fator of the structure when considering the suction effects at the design of soil nailed structures in a typical soil of Goiânia region.
A utilização de contenções em solo grampeado pode ser uma importante alternativa para a estabilização de um talude ou de uma escavação. Os grampos ou tirantes passivos são elementos de contenção ou de reforço de massas de solo que agem passivamente, requerendo deformações para mobilizar sua resistência. A análise do comportamento mecânico de uma estrutura onde existe solo grampeado pode ser feita através de métodos de equilíbrio limite, sendo representada por cargas de reforço aplicadas a camadas ou fatias sub-horizontais de um talude. A fatia tem a sua base atravessada por uma linha de ação de reforço e a carga de reforço é tratada como uma carga pontual concentrada agindo no ponto de intersecção da base de uma fatia com a linha de ação. Assim, através de cálculos por ferramentas analíticas e numéricas, o presente trabalho estudou o dimensionamento da estrutura de solo grampeado considerando a variação de sucção, que influencia a resistência do solo, simulando perfis de sucção de um solo típico da região do centro oeste brasileiro. Esse estudo foi realizado determinando parâmetros de resistência na interface grampo-solo por ensaios realizados em campo, como ensaios de arrancamento de grampo, e parâmetros de resistência e hidromecânicos do solo não saturado determinados em laboratório. Para isso, foram estudados dois perfis de sucção distintos e, para cada caso, analisou-se numericamente a estrutura de contenção em solo grampeado, obtendo-se as dimensões da estrutura através de um pré-dimensionamento, e, a seguir, analisando o fator de segurança da contenção utilizando programação computacional considerando o método de Bishop. No primeiro caso foi simulada numericamente a distribuição do perfil de sucção do solo estudado para uma condição de precipitação crítica na região de Goiânia. No segundo, foi obtido o perfil de sucção de campo para comparação com o primeiro caso. Com os resultados desta pesquisa, foi possível compreender o aumento da resistência e do fator de segurança da contenção ao considerar os efeitos de sucção no dimensionamento de uma estrutura de contenção em solo grampeado típico da região de Goiânia.

Solo grampeado é uma alternativa eficiente utilizada em obras de reforço de solos. É resultante da inclusão de reforços, denominados grampos, em um maciço em corte. A resistência ao cisalhamento da interface solo-grampo é um dos parâmetros mais importantes para fins de projeto. Este parâmetro é determinado a partir da experiência dos projetistas e se baseia principalmente no tipo de solo e em ensaios de campo (arrancamento, sondagens a percussão e pressiométricos). Neste contexto, a realização de ensaios de arrancamento in situ é extremamente importante para a quantificação deste parâmetro e, conseqüentemente, para a elaboração de projetos mais econômicos e seguros. A execução de ensaios de arrancamento em laboratório permite verificar condições muitas vezes não encontradas em campo. Este trabalho apresenta os resultados de ensaios de arrancamento de grampos realizados em laboratório. Também foi analisada a evolução da força nos grampos e dos deslocamentos do solo. Os grampos foram instalados em um protótipo de solo grampeado sobre o qual se aplicou uma sobrecarga de 50 kPa através de uma bolsa de ar comprimido. Os ensaios de arrancamento permitiram quantificar valores de resistência ao cisalhamento de interface da ordem de 145 kPa, mobilizados com pequenos deslocamentos dos grampos. O arrancamento de grampos instrumentados indicou que cerca de 90% do comprimento total dos grampos foi solicitado. Ao final dos ensaios de arrancamento, os grampos foram extraídos completamente do maciço de solo o que permitiu comprovar a sua integridade física. Os deslocamentos do solo foram máximos próximo ao topo do protótipo e na direção horizontal. Os resultados demonstram a viabilidade de estudar o comportamento do maciço reforçado a partir do comportamento do protótipo de solo grampeado construído em laboratório.
Soil nailing is an efficient soil reinforcement technique which uses inclusions, namely nails, in soil slopes. Unit skin friction is one of the most important parameters used in soil nailing design. The definition of this parameter is commonly based on local experience and correlations to some in situ tests. This work presents the results obtained from the pullout test carried out in a soil nailed wall prototype built in laboratory. Forces acting in nails were measured by strain gage instrumentation. Soil displacement was measured in short and long terms. The pullout tests were carried out after the application of a uniform surcharge given by a compressed air bag. The results showed that unit skin friction was about 145 kPa, mobilized with little nail displacements. About 90% of nail length were solicited during pullout tests, according to tests performed in strain gage instrumented nails. Nail extraction showed a high level of nail integrity. Soil displacements were higher close to the wall top, near the face. These results demonstrate the feasibility of using of laboratory prototype studies to investigate the geotechnical behavior of soil nailing structures.

ABSTRACT THE EFFECT OF GROUP BEHAVIOR ON THE PULL-OUT CAPACITY OF SOIL NAILS IN HIGH PLASTIC CLAY Ak&
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lmaz September 2009, 161 pages Soil nailing technique is widely used in stabilizing roadway and tunnel portal cut excavations. The key parameter in the design of soil nail systems is the pull-out capacity. The pull-out capacity of the soil nails can be estimated from the studies involving similar soil conditions or can be estimated from the empirical formulas. Field verification tests are performed before the construction stage in order to confirm the parameter chosen in the design of soil nailing system. It is reported in the literature that, the pull-out resistance of a soil nail in sand should be reduced for the nails installed closer than a specific minimum distance, whereas no such requirement have been discussed for nail groups in clays. v In this study, the pull-out resistance of nails in high plastic clay are tested to investigate the influence of nail spacing in group applications. The laboratory set-up for the pull-out tests is composed of an aluminum model box (300mm (w) x 300mm (h) x 500 mm (l)), soil sample, reinforcements, pull-out device, overburden pressure applicator and monitoring device. A series of pull-out tests has been carried out on single nails and group of nails with spacings 2 and 6 times the diameter of a nail in order to observe the group effect on the pullout capacity of the nails. The nails are located into their positions during the placement of clay into the box. Within the limitations of this study, it is observed that, there is a reduction in the pull-out capacity of the central nail in 2Ø
spaced group. The pull-out capacity of the central nail in nail group with 6Ø
spacing, is not affected from the neighboring nails. In all tests, the plots of pull-out load on nail versus nail displacement show that, the peak value of load is followed by a sharp reduction. The peak pull-out load is mobilized at first few millimeters of the nail displacements. A 3D finite element program is used for numerical analyses of the experiments. The measured pull-out capacity of the soil nails are compared by the results of simulated forces obtained from these analyses. By and large, the agreement between the tests and the numerical analyses is observed to be satisfactory. The details of the numerical models are briefly presented in order to give insight into numerical modeling of soil nails in real applications.

Os métodos de equilíbrio limite comumente utilizados no dimensionamento de estruturas de solo grampeado não oferecem informação sobre as tensões e deformações na estrutura. No entanto, o êxito da técnica pressupõe deslocamentos para que a resistência dos grampos seja mobilizada. Portanto, seria desejável conhecer: os deslocamentos que a estrutura. sofre durante e depois de realizado o processo da escavação; os esforços mobilizados nos grampos; e a distribuição de tensões atrás da parede da escavação. A importância deste estudo é maior em situações em que a previsão do comportamento é a responsável por garantir a segurança de construções e de instalações de serviço público próximas às escavações grampeadas. Análises bidimensionais e tridimensionais de tensão-deformação com elementos finitos foram realizadas para um melhor entendimento do comportamento da estrutura. As comparações dos resultados das modelagens numéricas permitiram conhecer várias vantagens e desvantagens de um e de outro tipo de modelagem. Realizaram-se também comparações entre resultados de modelagens numéricas que utilizaram os seguintes modelos constitutivos: elasto-plástico (com critério de ruptura de Mohr-Coulomb), hiperbólico e elástico-linear, sendo que para este último realizou-se uma análise incremental. Para a aplicação do modelo elástico-linear foi necessária a divisão do maciço em regiões em função do tipo de trajetória de tensão. Essas comparações permitiram concluir que, desde que com a correta especificação dos parâmetros elásticos, a modelagem baseada na Teoria da Elasticidade pode representar bem o comportamento de escavações grampeadas.
The limit equilibrium methods that are frequently used for design of soi nailing structures do not provide information about the structure\'s stress and strain. However, the technique\'s success depends on the displacements that mobilize the nails strength. Therefore it is desirable to predict the structure\'s displacement, during and after the excavation; the forces avting on nails; and the stress distribution behind the excavation wall. This study has its importance increased in situations in which the prediction of the behavior is needed to guarantee the safety of adjacent buildings and municipal installations near to the excavation. Three dimensional and two-dimensional fine element stress-strain analyses were carried out for a better understanding of the behavior of the structure. Comparisons of the results of different numerical models led to a clear picture of advantages and disadvantages of different approaches. Numerical comparisons were also carried out between analyses with different constitutive models: elasto-plastic (Mohr-Coulomb), hyperbolic and incremental linear elastic. Application of the linear elastic model required the division of the soil mass in regions, according to stress path. Those comparisons led to the conclusion that, given correctly specified elastic parameters, Theory of Elasticity is able to correctly model the behavior of nailed excavations.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
The adoption of the soil nailing technique in the project of slope stability once or excavations it is being more and more frequent. This with it is reguire a larger number of studies about the estimate of the the pullout resistance (qs) in function of parameters of field tests for the most varied types of Brazilian soils.The objective of this research was to propose correlations for the qs resistence in function of field tests, and also to compare the results also found in the pullout test with dear in existent formulations. The study was accomplished in a slope of young gneissic residual soil, Viçosa - MG.In the field test they occurred the standard penetration test (SPT), Menard pressuremeter test (PMT), Marchetti dilatometer test (DMT) and pullout test in twelve nails, only made with no injection procedures. The assembly of the pullout test system was different from the proposal for other authors and it was shown effective.The qs values obtained in the pullout tests and the correlations found for each nails were compared using appropriate statistics for each analysis. The parameters of the field test used in the proposed correlations Nspt, PL, and P0, were certain for the average of your magnitudes along the nails. The pullout resistance found for each nails and the parameters obtained in the field tests they were plotted in dispersion graphs us which lineal and no-lineal regressions were applied in the intention of to evaluate which mathematical model was adapted better to each proposition. For the correlation qs x Nspt the logarithmic model presented larger correlation coefficient (R2) and significance (p <0,05), in the relationship qs x p0 the quadratic form obtained larger R2, however the behavior of the curve was not suitable with the one of the soil, being accomplished the option by the logarithmic model that was highly significant (p <0,01). The correlation qs X PL didn't show any statistically significant and the choice of the format of the lineal curve was based on the behavior of the soil, same not presenting the largest value of R2. In the case to to the proposed correlations it s possible to conclude that they can be used as initial estimate of project being indispensable the execution of pullout tests to prove the safety with relationship to the values of adopted qs.
A adoção da técnica de solo grampeado no projeto de contenção de taludes ou escavações vem sendo cada vez mais freqüente, com isto se faz necessário um maior numero de estudos sobre a estimativa da resistência ao arrancamento (qs) em função de parâmetros de ensaios de campo para os mais variados tipos de solos brasileiros. O objetivo desta pesquisa foi propor correlações para a estimativa de qs em função de ensaios de campo, e também comparar os valores encontrados nos ensaios de arrancamento com estimados em formulações existentes. O estudo foi realizado em um talude de solo residual jovem de origem gnáissica, Viçosa MG. No campo efetuaram-se os ensaios de penetração (SPT), sondagem pressiometrica de Ménard (PMT), sondagem dilatometrica de Marchetti (DMT) e ensaios de arrancamento em 12 grampos, confeccionados somente com a bainha. A montagem do sistema de arrancamento foi diferente da proposta por outros autores e se mostrou eficaz. Os valores de qs obtidos nos ensaios de arrancamento e os encontrados pelas correlações existentes para cada grampo foram comparados através de estatísticas adequadas para cada análise. Os parâmetros dos ensaios de campo utilizados nas correlações propostas Nspt, PL, e p0, foram determinados pela média de suas magnitudes ao longo dos grampos. As resistências ao arrancamento encontrada para cada grampo e os parâmetros obtidos nos ensaios de campo foram plotados em gráficos de dispersão nos quais se aplicaram regressões lineares e não-lineares no intuito de avaliar qual modelo matemático se adequou melhor a cada proposição. Para a correlação qs x Nspt o modelo logarítmico apresentou maior coeficiente de correlação (R2) e significância estatística (p<0,05), na relação qs x p0 a forma quadrática obteve maior R2, porém o comportamento da curva não foi condizente com o do solo, sendo realizada a opção pelo modelo logarítmico que se mostrou altamente significante (p<0,01). Já a correlação qs X PL não apresentou nenhum modelo estatisticamente significante e a escolha do formato da curva linear foi baseada no comportamento do solo, mesmo não apresentando o maior valor de R2. Quanto às correlações propostas conclui-se que podem ser utilizadas como estimativa inicial de projeto sendo imprescindível a execução de ensaios de arrancamento para comprovar a segurança quanto aos valores de qs adotados.

Italy is a country susceptible to various and numerous natural disasters; landslide hazard is certainly one of the most important topics here, so the research for innovative and cost-effective solutions for landslide stabilization has great scientific and socio-economic relevance. This PhD fits the context by studying and developing a new technique for the stabilization of landslides, called “floating anchor”, both in theoretical and applied aspects. The technique involves the installation of passive nails in the landslide body, cemented along the entire profile with a sufficient foundation in the deep stable soil. The anchors fit the slope according to a discontinuous geometry without a continuous facing. Each anchor head connects only to a small concrete plate (the “floating” element), which may be bored in the soil. The reinforcements absorb by frictional contact a portion of the shear stress induced by the moving landslide, slowing down its evolution process until it completely stops. It is a modular and flexible technique; the system fits the soil deformations without losing effectiveness. The PhD work analyses all the components of the system in order to assess the geotechnical and structural behaviour. A comparison with the techniques commonly used for landslide stabilization highlights the main advantages of the floating anchors, both in efficiency and cost terms. An important part of the research focuses on the experimental analysis in a 1g scale physical model of the behaviour of floating plates as a function of their shape. An equation for the calculation of the bearing capacity of the floating plate with the introduction of specific shape and volume factors has been determined. A FEM analysis provides a numerical model calibration based on the experimental results and highlights the influence of the plate on the soil stress-strain state. Specific guidelines for the design of floating anchors are proposed according to two physical-mathematical configurations: one “static” short-term approach and one long-term approach, assuming a non-linear viscous behaviour of the soil. At last, some applications complete the research: the development of a particular enhanced anchor bar (the “composite anchor”), and the design and execution of some stabilization works with floating anchors in four real landslides activated in North-Eastern Italy in conjunction with the exceptional rainfall that affected the area in autumn 2010. The monitoring of the stabilized slopes proves the viability and technical efficiency of the method.
Il territorio italiano è soggetto per sua conformazione ad una diffusa presenza di fenomeni franosi. La ricerca di soluzioni e tecnologie innovative ed economicamente vantaggiose per la stabilizzazione dei movimenti franosi si rivela quindi un problema di grande attualità scientifica. Il presente Dottorato di Ricerca si inserisce in questo contesto con l’obiettivo di studiare e sviluppare dal punto di vista teorico e applicativo una tecnica innovativa per la stabilizzazione di movimenti franosi, denominata “ancoraggio flottante”. La tecnica prevede l’installazione di ancoraggi passivi nel corpo di frana, cementati al terreno e con adeguata fondazione nel terreno stabile profondo, posizionati secondo una geometria discontinua senza un rivestimento continuo del versante, ma con la sola applicazione di una piastra (l’elemento flottante) di ridotte dimensioni collegata alla testa di ciascuna barra. I rinforzi assorbono per attrito parte degli sforzi tangenziali indotti dal movimento franoso, rallentandone il processo evolutivo fino al completo arresto. Si tratta di una tecnica modulare e flessibile in quanto il sistema si adatta alle deformazioni del versante senza perdere di funzionalità. Il lavoro svolto nel corso del Dottorato di Ricerca ha consentito un’analisi delle varie componenti del sistema al fine di valutarne il comportamento geotecnico e strutturale. Un confronto iniziale con le tecniche di stabilizzazione di frane comunemente utilizzate evidenzia i principali vantaggi degli ancoraggi flottanti in termini di efficienza e di costo. Una parte importante della ricerca ha riguardato l’analisi sperimentale in modello fisico in scala 1g del comportamento delle piastre flottanti in funzione della loro geometria, e ha consentito di determinare un’equazione per il calcolo della capacità portante della piastra flottante con l’introduzione di specifici fattori di forma e di volume. Con analisi FEM è stato calibrato un modello numerico sulla base dei risultati sperimentali per poter meglio evidenziare l’influenza della piastra sullo stato tenso-deformativo del terreno. Si sono inoltre proposte delle specifiche linee guida per la progettazione degli interventi con ancoraggi flottanti secondo due schemi fisico-matematici: un approccio “statico” a breve termine e un approccio a lungo termine nell’ipotesi di comportamento viscoso non lineare del terreno. Completa la ricerca una parte applicativa, con lo sviluppo di una particolare barra di ancoraggio potenziata (ancoraggio composito), e con la progettazione ed esecuzione di alcuni interventi con ancoraggi flottanti in quattro frane reali attivatesi in provincia di Vicenza in concomitanza con le piogge eccezionali che hanno colpito tutto il nord-est italiano e in particolare la regione Veneto nell’autunno 2010. Il monitoraggio degli interventi appare comprovare la validità e l’efficacia tecnica del metodo.

Apesar do largo emprego da técnica de solo pregado em nosso país, pouquíssima pesquisa foi realizada sobre a resistência ao cisalhamento de interface solo-reforço (qs) e sobre a importância deste parâmetro no desempenho desta técnica de reforço in situ de taludes e escavações. Busca-se com esta tese, avaliar experimentalmente, a influência de diferentes metodologias executivas do chumbador (número de injeções) neste parâmetro. As informações para o desenvolvimento deste trabalho foram obtidas a partir de ensaios de arrancamento realizados em chumbadores construídos em duas obras nas cercanias da cidade de São Paulo, ou seja, em escala real. De forma complementar, também foi construído uma estrutura de solo pregado em laboratório. A partir dos ensaios realizados, observaram-se melhorias significativas na resistência ao cisalhamento de interface a partir das injeções do chumbador e estabelecer equações que relacionam o valor de qs com o volume injetado de calda de cimento, sendo uma importante ferramenta para analisar o desempenho do chumbador. O monitoramento ao longo do ensaio permitiu analisar os mecanismos de distribuição das cargas. Por fim, é apresentada uma proposta de metodologia para a realização do controle de qualidade do chumbador.
Besides the soil nailing technique being common practice in Brazil, there is little research on the shear strength of the soil-reinforcement interface (qs) and on the importance of this parameter on the performance of this in situ reinforcement technique of slopes and excavations. Accordingly, this study has the objective to experimentally evaluate the influence of different executive methodologies of the nail (i.e. number of grout injections) on the parameter qs. Data were obtained from in situ, full scale pullout tests performed on nails built in two construction sites near Sao Paulo city. Additionally, a soil nailing structure was built in laboratory. The results show that significant improvement is achieved on the soil-nail interface shear strenght by the number of grout injections. Moreover, the pullout tests on the nails provided quantification of this improvement. Consequently, it was possible to establish equations that relate the value of qs to the volume of cement grout injected, which is as important tool to evaluate the performance of the nail. Monitoring of the instrumentation during execution of the pullout tests allowed evaluation of the mechanisms of load distribution along the nails. Finally, a methodology is proposed for a quality control procedure on soil-nailed walls.

Résumé de la thèse en français : Le clouage des sols est une technique de soutènement d’excavations développée en France dans les années 1970. En pratique aujourd’hui, les parements de tels ouvrages sont souvent dimensionnés pour reprendre les efforts de traction admissibles dans les renforcements. De manière générale, dans la profession il est notoire qu’au parement les efforts de service dans les renforcements sont en fait plus faibles que calculés, et ce d’autant plus à proximité du pied de parement en raison du phasage de construction de ces ouvrages, du haut vers le bas. En 2015 la Commission de Normalisation Française Justification des Ouvrages Géotechnique (CNJOG) a engagé une révision de la norme NF P 94 270, notamment pour clarifier la justification du parement. Dans ce contexte, cette thèse vise à améliorer les connaissances sur le fonctionnement des massifs de sol cloué en place et en particulier sur la mobilisation du parement. Les travaux réalisés ont comporté une étude paramétrique expérimentale sur modèle physique réduit en centrifugeuse géotechnique (trois longueurs de clous), complétée par une analyse par modélisation numérique en déformations. Sur le modèle réduit, la mobilisation des efforts dans les clous était observée à plusieurs niveaux à l’aide de fibres optiques munies de réseaux de Bragg, situées à l’axe neutre des clous. Les réseaux de Bragg étaient distants de 5 mm, soit 25 cm dans l’ouvrage réel modélisé. Les déplacements au sein du massif ont été suivis à l’aide d’une technique d’imagerie de type Particle Image Velocimetry (PIV), par suivi de motifs de grains de sables au travers d’une paroi latérale transparente du modèle physique à échelle réduite. Les essais ont montré une nette influence de l’élancement des ouvrages sur l’amplitude des déplacements et le profil des efforts mobilisés. Parallèlement, un modèle numérique tridimensionnel de calcul par éléments finis et respectant le phasage de construction a été développé sous CESAR-LCPC. Les clous ont été modélisés par des éléments linéiques partageant leurs nœuds avec les éléments volumiques par l’intermédiaire d’un degré de liberté supplémentaire, correspondant au déplacement relatif sol-clou. Le comportement en déformations du sol a été représenté par le modèle Hardening Soil Model (HSM). La comparaison des résultats expérimentaux et des simulations numériques a permis de mettre en avant l’influence de l’élancement sur le comportement du mur mais a souligné les limites de l’utilisation des éléments finis, et en particulier la forte sensibilité aux raideurs du sol et de l’interface sol-clou. Cette comparaison a également permis de proposer une amélioration du dimensionnement des sols cloués. Le logiciel PROSPER réalise ce dimensionnement en choisissant une courbe de rupture le long de laquelle le déplacement du sol mobilise la réaction des clous. Ce déplacement est généralement considéré homogène mais les résultats de ce travail permettent d’en proposer une allure. Des abaques ont été établis donnant cette distribution en fonction du rapport d’élancement. Cette approche du calcul des efforts au parement dans les renforcements a été mise en œuvre dans le cas d’un ouvrage expérimental
Soil nailing is technique developped in France during the 70s for the retaining of excavations. Today, the facing of such structures is often designed to support the maximal tensions admissible in the reinforcements. The professionals generally admit that the service loads in the reinforcements are smaller than the calculated ones. Especially at the facing foot because of the construction phasage, from top to bottom. In 2015, The French Standardization for Geotechnical Structures Verification launched a revision of the standard concerning soil-nailing, especially about the facing design. In this context, this thesis aims at a better knowledge of soil-nailed walls behaviour and especially about the mobilization of the facing. The works consisted of a parametrical study on a centrifuge model (three nail lengths) and of a numerical modelling. On the centrifuge model, the nail tensions were observed, at each level, using Bragg grated optic fibers, placed at the core of the nails. The Bragg networks were placed 5 mm from each other (25 cm on the real wall). The displacements inside the soil were followed by a Particle Image Velocimetry like technique. The grains patterns were observed through a lateral translucid face. The experiments have shown a strong influence of the structure slenderness on displacements amplitude and on tensions allures. A 3D numerical model was also developped with CESAR-LCPC. It was realized with Finite Elements Method and the building phasage was respected. Nails were modelized by lineic elements whose nodes where shared with volumic elements. In order to simulate the friction law, an additional degree of freedom was introduced : the relative displacement between soil and nail. The deformation behaviour of the soil was simulated using Hardening Soil Model. The comparison of experimental and numerical results highlighted the influence of slenderness on wall behaviour as well as the limits of Finite Elements Method. In particular, the results are strongly dependant on the stiffness of soil and of the interface between soil and nail. This comparison also allowed to propose an improvement of the soil-nailing design. The PROSPER software choses a failure surface along which the displacement of soil mobilizes the reaction of the nails. This displacement is generally considered as homogenous but the results of the present work allow to propose an allure. Abacus have proposed for the distribution of this displacement and this design approach has been tested on an experimental wall

Partout où la pierre est facilement disponible, on trouve des constructions en maçonnerie de pierre. Suivant les coutumes et les usages, les blocs de pierres sont assemblés bruts, simplement ébauchés ou parfaitement taillés, avec ou sans l'ajout d'un liant. Supplantée par le béton dans les constructions neuves depuis le milieu du XX} siècle, les ouvrages en maçonnerie demeurent majoritaires dans le patrimoine bâti français, un patrimoine qu'il convient d'entretenir rationnellement. L'objectif de ce travail de thèse est de poursuivre l'élaboration d'un cadre scientifique rigoureux et opérationnel afin de donner aux décideurs et aux gestionnaires les outils nécessaires pour mener à bien leur mission. Nous proposons ici deux outils d'évaluation de la stabilité d'ouvrages de soutènement en maçonnerie basés sur l'utilisation conjointe du calcul à la rupture avec des méthodes d'homogénéisation. Dans un premier temps, nous mettons d'abord au point un outil analytique permettant de dimensionner des ouvrages neufs ou d'évaluer la stabilité d'ouvrages peu déformés. Cet outil permet également de dimensionner des solutions de renforcement par clouage lorsque cela est jugé nécessaire. Dans un deuxième temps, nous implémentons cet outil dans un code numérique afin de lui donner la souplesse nécessaire à l'étude d'ouvrages non-conventionnels, de grandes taille ou fortement pathologique. Enfin, nous mettons en oeuvre plusieurs campagnes expérimentales qui nous fournissent les données nécessaires à la validation de ces modèles de calcul
Wherever stone is readily available, we encounter stone masonry buildings. Depending on customs or dedicated use, the blocks are used raw, lightly faced or perfectly cut, with or without the use of mortar. Althougth concrete has replaced masonry in new construction for some decades, the better part of the French built heritage is made of masonry, an heritage we are responsible for. This works aims at contributing to create a reliable scientific frame for that purpose. This thesis uses the yield design theory alongside with homogenisation techniques to study the stability of stone masonry earth retaining walls. First, we provide an analytical tool suitable for designing new structures or assessing the stability of existing ones that are still in good shape. Should it be needed, this tools allows for the design of a strengthening solution based on soil-nailing. Then, we implement it in a finite element code to give it the versatility required to study unconventionnal structures or structures badly damaged. We then present several experimental campaigns aiming at validating the proposed tools

The diploma thesis deals with the construction project of the new building of the primary school in Bobrová. The main goal of the thesis is to propose a suitable implementation procedure in relation to the specific place of the site. The thesis deals with the time schedule of the main object, itemized budget, major building machines and mechanisms, project of site equipment, study of the construction realization, material resources plan, technical report, time schedule and financial plan of the main object and also with the situation of the construction. It focuses in detail on the stage of earthworks, including the reinforcement of the walls of the building pit using soil nailing. For this stage a technological regulation and a control and test plan have been developed.

碩士
淡江大學
土木工程學系
87
The purpose of this research is to simulate the behavior of soil nailing structure during excavating procedure, define the destroyed area in earth based on experimental result, and to compare the result with those of current method. The experiment is to simulate two excavations of 1.0m and 0.7m high in two sandboxes of 1.8m * 0.82m * 1.5m and 1.0m * 0.345m * 1.0m respectively. Nails are buried in five levels with obliquity of 0°, 15°, and 30° in order to test influence of different nail obliquity. Two kinds of boards with thickness of 1.5mm and 3mm, help analyze influence of different board thickness strength. Fail area of earth is measured by calculating relative movement of rubber net in both sides of sandboxes on different spots before and after excavating procedure. The nail strength of each excavating procedure is measured directly from the strain gages attached on nails. Experimental result shows that: (1) The ratio of horizontal board movement and excavated height of big sandbox rises with increment of nail obliquity; but result is opposite with small sandbox for the ratio of horizontal board movement and excavated height decrease while nail obliquity increase. (2) Distortion of board is related with the board strength. Position of maximum board movement moves down to the lower part of the wall while board strength increases. (3) Axial strength of nail near boards increases with increasing depth in big sandbox while the maximum axial strength occurs in the forth level in small sandbox. The value of axial strength in both sandboxes is apt to be fixed in different depth. (4) After excavating procedure, tensile stress of upper level nail is close to at-rest lateral earth stress, tensile stress of lower level is close to Rankine active lateral earth stress. (5) In situation of shallow base excavation or lesser earth pressure, and due to possible fail area is closer to straight line, failure hypothesis of German design is close to that observed in model tests.

Soil nailing is a soil stabilization technique which is used as a remedial measure in order to treat the unstable natural or artificial soil slopes. This technique is also used in order to allow the safe over-steepening of new or existing soil slopes. In this method of slope stabilization, a relatively slender reinforcing element is driven into the soil slope. Reinforcing elements generally used in this technique generally consists of HYSD steel bars or steel hollow tubes depending upon the requirement. The nails used for soil nailing are generally driven into the slope at an angle of 100 to 200 with horizontal plane. Due to the application of surcharge load by various means, the backfill material starts deforming which in turn passively produces the tensile stresses in the nails. The method of installation is different for solid and hollow bars. Solid bars are generally installed into the pre-drilled holes. These bars are grouted into place simultaneously using separate grout line. Hollow bars are drilled and grouted simultaneously with the help of sacrificial drill bit. When bars are inserted into the soil slope by using drilling technique ,then they are fully grouted and are installed at a slight downward inclination. Centralizers are used in order to keep the nails at its exact position. In order to provide the stability a rigid facing usually of pneumatically applied concrete (shotcrete) is applied. In some cases isolated nail head plates can be also used for this purpose. In few cases a flexible reinforcing mesh is held against the soil slope face under the head plates. In case if environmental conditions are not adequate, then rabbit proof wire mesh and environmental erosion control fabrics are used in addition with flexible mesh facing.

碩士
淡江大學
土木工程學系
88
The purpose of this research is to research the board stiffness on the behavior of soil nailing wall during excavation procedure. The experiment is to simulate excavation of 1.0m high in sandbox of 1.8m*0.82m*1.5m. the length of nails are 0.7m and buried with horizontal space of 27.5cm and vertical space of 20cm. There are three rows of nails. Every row has five nails. Using three kinds of boards with thickness of 1.5mm, 2mm and 3mm, and three kind of nail obliquity of 00, 150 and 300 to analyze. The experimental result shows that: (1) The ratio of horizontal board movement divided by depth of excavation is 1.88%、1.51%、0.49% when thickness of board is 1.5mm、2mm、3mm. It is linearity decreasing. (2) The maximum axial strength is 92.10 N、124.60 N、95.48 N and the maximum bending moment is -0.471 N.m、-0.472 N.m、0.233 N.m when thickness of board is 1.5mm、2mm、3mm. (3) Thickness of board is insensitive to the trend of the maximum of tensile stress on the top closed to Rankine active lateral earth stress when nail obliquity is 0 degree. The maximum of tensile stress at the depth of 0.7m and 0.9m is close to apparent earth-stress proposed by Terzaghi and Peck. (4) The value of bending moment near board is between 0.325 N.m and —0.472 N.m and that at the end of soil nailing is near 0. (5) The ratio of axial strength by pre-buried method is 2.19%~15.24%, and the ratio of bending moment by pre-buried method is 17.31%~-57.73%.

碩士
中華科技大學
土木防災工程研究所
101
Deep-excavation construction method can be sorted into two mechanic type: internal bracing method and tie-back method. The former doesn’t cause any infringement issues of boundary, but the process is more complex, with staggered construction moving lines and long operating time. And the later possesses the opposite advantages and disadvantages. Soil nail is a commonly used technology of tie-back method. This research is aim to investigate the influence factors of using soil nails on sandy stratum with numerical analysis. In the research, different strengths of ground modification are given on non-excavated area. Through these environmental variable scenarios, the changing of the horizontal displacements on the excavated surface could be observed. The results indicated that the concept of soil nails deep-excavated construction method is to strengthen the soil with soil nails and ground modification, and create a stable gravity-typed retaining structure. Different from the traditional method, which the maximum displacement lays in the excavating of the bottom area, the maximum displacement of the soil nails construction method occurred mostly in the area of middle depth. If conduct ground modification on non-excavated area, when modified strength increases, the displacement of the deep excavation wall decreases. But when the modified strength rises above 150kPa, increasing modified strength does limited effect on the suppression of the displacement. Considering economic benefits, conducting 150kPa ground improvement at 1/3 of the region near the bottom of the excavated depth performs the best wall-displacement suppression effect.

碩士
朝陽科技大學
營建工程系碩士班
93
The gravel slope design of the South Highway 3, vegetation belt pavement method and thin layer hydrograsser method slope protection methods were used. When it rains, the slope corrodes easily, and form ditches that drains the fine topsoil. As a result, during the dry season in southern Taiwan, it is difficult for plant life to grow, and does not achieve the necessary effect. The goal of this research is to suggest which method is more suitable for the existing gravel slopes, and carry out a discussion on the stability of the gravel slope. First, an on-site experiment on the feasibility and serviceability of Wei-Feng Zheng (2003) gravel slope soil nailing method. This research continues with FLAC 4.0 simulation observation point, and analyzes gravel slope with different soil nailing + ecromat failure model and mechanism; research scope soil protection methods (thin layer hydrograsser method) on (Ku-Kang interchange to Mei-Shan interchange) and three slope experiments with different methods (without soil nailing + ecromat, press type soil nailing + ecromat and put type soil nailing + ecromat), and a thorough result appraisal on the safety, economical, and ecology efficient of the three different methods. Lastly, to establish a gravel slope monitoring system that conforms to the South Highway 3. This finding shows that: (1) Failure on all existing gravel soil slope are due to shallow slipping. (2) Soil nailing can effectively reverse failure surface on gravel soil slope. (3) Know the three kinds of conditions for different analysis, the most powerful influence factor heavy rainfall condition that influence slope stability. (4) Data of difference site monitor and simulation monitor in site monitor instrumental error scope therefore may know the normal conditions of gravel slope stability analysis when condition using the supposition parameter of reasonable value. (5) Know from the analysis of gravel slope stability, the conditions of gravel slope with soil nailing system after heavy rainfall and slope failure model belongs to circular rotational failure. (6) Know from the result appraisal of gravel slope, put type soil nailing + erocomat is the safest, economical and ecological efficient method. (7) Finally according to the indirect model (FLAC 4.0 simulations analyses) and the experience model (Japan experiences) to establish the gravel slope monitoring system on the South Highway 3.

碩士
中華科技大學
土木防災工程研究所
100
Theoretically, the soil of sandy stratum doesn’t possess the qualification of operating soil nails deep-excavation construction method because of the lack of cohesion. However, it could be feasible if given appropriate target strength using ground modification method on non-excavated area to provide sufficient cohesion and balance the un-braced gneiss, then followed up by operating soil nails and shotcrete process to stabilize the excavated acting surface. This research is aim to investigate the influence factors of using soil nails on sandy stratum with numerical analysis. In the research, different target strengths are given to the ground improvement on non-excavated area. Through these environmental variable scenarios, the changing of the horizontal displacements on the excavated surface could be searched. The results indicated that instead of inhibiting the displacement of the gneiss with high-stiffness retaining wall, the concept of soil nails deep-excavated construction method is to strengthen the soil with soil nails and ground modification, and increase the stability on the entire non-excavated gneiss in order to create a stable gravity-typed retaining structure. Different from the traditional method, which the maximum displacement lays in the excavating of the bottom area, the maximum displacement of the soil nails construction method occurred mostly in the area of middle depth. When the excavated depth increase, obvious displacement increments could still been seen obviously on the surface where soil nails were placed. And with the depth gained, the displacement increment increased progressively. In practice, inclinometer tube in soil is often used to monitor the stimulating lateral horizontal displacement of the excavated surface. The analyzed result shows that it would underestimate the lateral horizontal displacement under most circumstances, and the phenomena got more notable with the excavated depth increased.

Il territorio italiano è soggetto per sua conformazione ad una diffusa presenza di fenomeni franosi. La ricerca di soluzioni e tecnologie innovative ed economicamente vantaggiose per la stabilizzazione dei movimenti franosi si rivela quindi un problema di grande attualità scientifica. Il presente Dottorato di Ricerca si inserisce in questo contesto con l’obiettivo di studiare e sviluppare dal punto di vista teorico e applicativo una tecnica innovativa per la stabilizzazione di movimenti franosi, denominata “ancoraggio flottante”. La tecnica prevede l’installazione di ancoraggi passivi nel corpo di frana, cementati al terreno e con adeguata fondazione nel terreno stabile profondo, posizionati secondo una geometria discontinua senza un rivestimento continuo del versante, ma con la sola applicazione di una piastra (l’elemento flottante) di ridotte dimensioni collegata alla testa di ciascuna barra. I rinforzi assorbono per attrito parte degli sforzi tangenziali indotti dal movimento franoso, rallentandone il processo evolutivo fino al completo arresto. Si tratta di una tecnica modulare e flessibile in quanto il sistema si adatta alle deformazioni del versante senza perdere di funzionalità. Il lavoro svolto nel corso del Dottorato di Ricerca ha consentito un’analisi delle varie componenti del sistema al fine di valutarne il comportamento geotecnico e strutturale. Un confronto iniziale con le tecniche di stabilizzazione di frane comunemente utilizzate evidenzia i principali vantaggi degli ancoraggi flottanti in termini di efficienza e di costo. Una parte importante della ricerca ha riguardato l’analisi sperimentale in modello fisico in scala 1g del comportamento delle piastre flottanti in funzione della loro geometria, e ha consentito di determinare un’equazione per il calcolo della capacità portante della piastra flottante con l’introduzione di specifici fattori di forma e di volume. Con analisi FEM è stato calibrato un modello numerico sulla base dei risultati sperimentali per poter meglio evidenziare l’influenza della piastra sullo stato tenso-deformativo del terreno. Si sono inoltre proposte delle specifiche linee guida per la progettazione degli interventi con ancoraggi flottanti secondo due schemi fisico-matematici: un approccio “statico” a breve termine e un approccio a lungo termine nell’ipotesi di comportamento viscoso non lineare del terreno. Completa la ricerca una parte applicativa, con lo sviluppo di una particolare barra di ancoraggio potenziata (ancoraggio composito), e con la progettazione ed esecuzione di alcuni interventi con ancoraggi flottanti in quattro frane reali attivatesi in provincia di Vicenza in concomitanza con le piogge eccezionali che hanno colpito tutto il nord-est italiano e in particolare la regione Veneto nell’autunno 2010. Il monitoraggio degli interventi appare comprovare la validità e l’efficacia tecnica del metodo.

In the present thesis, studies on the response of soil nail walls subjected to static and seismic conditions using finite element based numerical simulations and the principle of reliability analysis have been performed. The basic methodology constitutes the study of various aspects of soil nail walls such as analyses of important external, internal and facing failure modes, development of axial forces, and displacement observations by considering various typical and prototype cases. For better understanding and presentation, subject matter of the thesis is organised in the following ten chapters. Chapter 1 of the thesis provides an introduction to the soil nailing technique and highlights some of its applications, advantages, and limitations. Chapter 2 provides a detailed review of existing literature on the soil nailing technique. Chapter 3 provides a detailed overview the various methodologies adopted in the thesis for the analyses and response study of the soil nail walls. Chapter 4 deals with the important aspects related to the plane strain finite element based numerical simulations of soil nail walls. In particular, addresses the implications of the use of advanced soil models and the consideration of bending stiffness of soil nails on the overall response of the soil nail walls. Chapter 5 presents finite element simulations based appraisal of the conventional design methodology of soil nail walls, and studies the response of typical soil nail walls under static and seismic conditions. Chapter 6 presents a reliability based study of the important failure modes of soil nail walls subjected to the variability in in-situ soil parameters, and highlights the importance of reliability analysis in context of soil nail walls. Chapter 7 proposes load and resistance factor design (LRFD) methodology in context of soil nail walls, and highlights the need in advancement of the existing conventional design methodology for soil nail walls. Chapter 8 illustrates the use of factorial design of experiment methodology in developing regression models for stability criteria analysis of soil nail walls. Chapter 9 proposes methods for assessing the adequacy of field pullout tests performed in accordance with the prevalent soil nailing guidelines. Further, a reliability based methodology is proposed for the evaluation and various applications of field pullout tests results have been illustrated. Chapter 10 summarises the various studies reported in the thesis and provides a few important conclusions. It is believed that the various studies reported in the thesis contribute to the enhancement of the existing knowledge on soil nailing technique, advancement in the analysis and design methods, and in general, are useful to the soil nailing practice.

In the present thesis, studies on the response of soil nail walls subjected to static and seismic conditions using finite element based numerical simulations and the principle of reliability analysis have been performed. The basic methodology constitutes the study of various aspects of soil nail walls such as analyses of important external, internal and facing failure modes, development of axial forces, and displacement observations by considering various typical and prototype cases. For better understanding and presentation, subject matter of the thesis is organised in the following ten chapters. Chapter 1 of the thesis provides an introduction to the soil nailing technique and highlights some of its applications, advantages, and limitations. Chapter 2 provides a detailed review of existing literature on the soil nailing technique. Chapter 3 provides a detailed overview the various methodologies adopted in the thesis for the analyses and response study of the soil nail walls. Chapter 4 deals with the important aspects related to the plane strain finite element based numerical simulations of soil nail walls. In particular, addresses the implications of the use of advanced soil models and the consideration of bending stiffness of soil nails on the overall response of the soil nail walls. Chapter 5 presents finite element simulations based appraisal of the conventional design methodology of soil nail walls, and studies the response of typical soil nail walls under static and seismic conditions. Chapter 6 presents a reliability based study of the important failure modes of soil nail walls subjected to the variability in in-situ soil parameters, and highlights the importance of reliability analysis in context of soil nail walls. Chapter 7 proposes load and resistance factor design (LRFD) methodology in context of soil nail walls, and highlights the need in advancement of the existing conventional design methodology for soil nail walls. Chapter 8 illustrates the use of factorial design of experiment methodology in developing regression models for stability criteria analysis of soil nail walls. Chapter 9 proposes methods for assessing the adequacy of field pullout tests performed in accordance with the prevalent soil nailing guidelines. Further, a reliability based methodology is proposed for the evaluation and various applications of field pullout tests results have been illustrated. Chapter 10 summarises the various studies reported in the thesis and provides a few important conclusions. It is believed that the various studies reported in the thesis contribute to the enhancement of the existing knowledge on soil nailing technique, advancement in the analysis and design methods, and in general, are useful to the soil nailing practice.

碩士
國立臺灣海洋大學
河海工程學系
92
Abstract Due to the merits of rapid construction, uncomplicated construction method and low cost, soil nailing has been popular in western countries. Recently years in Taiwan, soil nailing is quite an accomplishment in dealing with the unstable slopes problems. However, the research and development in seismic resistance of nailed slopes can’t synchronize the real situation in constructing, and always explore the design of seismic resistance of nailed slopes in certain cohesion conditions. In this thesis, not the seismic resistance design of nailed slopes will be discussed but the relationship in seismic resistance between different cohesion and nailed slopes will be explored. The FDM program FLAC is used. Results of numerical analyses shows that the optimum nail length would probably shorten by increasing of the soil cohesion. The seismic resistance effects on changing the nail inclination of cohesion slopes make a little effort during c=50kpa~150kpa. There are obvious improvement with the ability of the seismic resistance in slopes when the c value increase eventually. It is shown that c=60kpa make a significant suppression in the max. horizontal displacement of slopes. The effect on suppressing the max. horizontal displacement in slopes appears the best way to against horizontal displacement while c value increase to 100kpa. When c value rise from 50kpa to 150kpa, the deformation pattern will be different from slide deformation, translational slides deformation and falls deformation. keywords: cohesion, soil nailing, nailed slope, seismic resistance, deformation pattern, finite difference program