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1
Chan, Sze Ho. "Negative skin friction on piles in consolidating ground /". View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202006%20CHAN.
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2
Gencoglu, Cansu. "Numerical Assessment Of Negative Skin Friction Effects On Diaphragm Walls". Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615444/index.pdf.
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Within the confines of this study, numerical simulations of time dependent variation of downdrag forces on the diaphragm walls are analyzed for a generic soil site, where consolidation is not completed. As part of the first generic scenario, consolidation of a clayey site due to the application of the embankment is assessed. Then two sets of diaphragm walls, with and without bitumen coating, are analyzed. For comparison purposes, conventional analytical calculation methods (i.e., rigid-plastic and elastic-plastic soil models) are also used, the results of which, establish a good basis of comparison with finite-element based simulation results. Additionaly, the same generic cases are also analyzed during the stages of excavation, when diaphragm walls are laterally loaded. As the concluding remark, on the basis of time dependent stress and displacement responses of bitumen coated and uncoated diaphragm walls, it was observed that negative skin friction is a rather complex time-dependent soil-structure and loading interaction problem. This problem needs to be assessed through methods capable of modeling the complex nature of the interaction. Current analytical methods may significantly over-estimate the amount of negative skin friction applied on the system, hence they are judged to be over-conservative. However, if negative skin friction is accompanied by partial unloading as expected in diaphragm walls or piles used for deep excavations, then they may be subject to adverse combinations of axial load and moment, which may produce critical combinations expressed in interaction diagrams. Neglecting the axial force and moment interaction may produce unconservative results.
3
Lee, Cheol-Ju. "The influence of negative skin friction on piles and in pile groups". Thesis, University of Cambridge, 2001. https://www.repository.cam.ac.uk/handle/1810/272078.
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4
Lam, Sze Yue. "Effects of axial load, shielding and shape on negative skin friction on piles /". View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202006%20LAM.
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5
Sharif, Ali. "Negative skin friction on single piles in clay subjected to direct and indirect loading". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0013/MQ39977.pdf.
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6
Toma, Tahsin Munir. "A model study of negative skin friction on a fixed base pile in soft clay". Thesis, Heriot-Watt University, 1989. http://hdl.handle.net/10399/919.
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In this research programme, a small-scale laboratory test was carried out to investigate the phenomenon of negative skin friction through studying the interaction between a pile and the surrounding soil and to obtain, by means of an instrumented 50mm diameter model pile, an expression for the magnitude and distribution of negative skin friction for an end-bearing pile in soft clay. The programme included measurements of pore water pressures using miniature piezometers, both vertically along the pile shaft and laterally from it, as the pattern of dissipation of this pressure controls the distribution of negative skin friction along pile length at any given time. Two testing programmes were conducted. Each testing programme consisted of applying load increments on the soil up to 90 kPa as surcharge pressures. Pore pressures, settlements and pile loads were monitored until 90% consolidation had been achieved. From test results, expressions relating the surcharge pressure and soil shear strength with the developed negative skin friction have been established. The study has been extended to include predictions of negative skin friction and pore water pressures by the use of Numerical Methods such as the Finite Element Method and the Finite Difference Method. Results obtained by these methods have been compared with those measured.
7
Sears, Brian Keith. "Pile Downdrag During Construction of Two Bridge Abutments". BYU ScholarsArchive, 2008. https://scholarsarchive.byu.edu/etd/1918.
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Two steel pipe piles in place in abutments for two different bridge constructions sites were instrumented with strain gauges to measure the magnitude of negative skin friction. The piles were monitored before, during and up to 19 months after construction was completed. The load versus depth and time in each pile is discussed. Maximum observed dragloads ranged from 98 to 127 kips. A comparison with two methods for calculating dragloads is presented. Both comparison methods were found to be conservative, with the Briaud and Tucker (1997) approach more closely estimating the observed load versus depth behavior.
8
Jha, Pravin. "ANALYSIS OF THE EFFECTS OF HEAVILY LOADED MAT FOUNDATION ON ADJACENT DRILLED SHAFT FOUNDATION". OpenSIUC, 2015. https://opensiuc.lib.siu.edu/dissertations/1121.
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Construction of heavily loaded shallow foundations adjacent to deep foundation is generally avoided in common geotechnical engineering practice to minimize additional loads on deep foundations. However, with the growing trend of urbanization leading to a demand of new construction, it is not always possible to avoid such situation where a heavily loaded shallow foundation will be right next to the infrastructure resting on deep foundations. When this situation cannot be avoided, influence of soil pressures and deformations in soil, created by shallow foundation on adjacent deep foundation, must be evaluated. The study of interaction between deep foundations has been carried out by several researchers in terms of pile-soil-pile interaction. Similarly, there are many published studies on interaction between closely spaced shallow foundations in terms of bearing capacity and settlement. However, not much published literature is available for practicing engineers to analyze and design deep and shallow foundations when they are constructed adjacent to each other. Construction of heavily loaded mat adjacent to drilled shafts would cause complex interaction between the foundations. However, lateral stress and drag forces on the shafts resulting from the heavy load on the mat foundation are the two major factors that would affect the design and performance of shafts. Since there is not much literature and guidance available to analyze and design such kind of situation, a preliminary investigation was first carried out where magnitude of the drag forces and lateral forces on drilled shafts were estimated using simple geotechnical engineering principles. The limitations of preliminary analysis led to the need of more sophisticated analysis using finite element techniques. As a part of this research, a detailed parametric study using finite element techniques has been performed to better understand stress and deformation distributions, and develop simplified methods to analyze this type of problems. A stress bulb for lateral stresses under a uniformly loaded square foundation, similar to the pressure bulb for vertical stresses which is widely used in the geotechnical engineering practice, has been proposed, which provides a significant tool for practicing engineers to understand lateral stress distribution below a uniformly loaded square area and estimate lateral stresses on nearby deep foundations. Similarly, a deformation bulb under a uniformly loaded square foundation is proposed. A new term “Isodefers” has been proposed to refer the lines of equal deformation. Isodefers are also a significant tool for practicing engineers to understand vertical deformation distribution below a uniformly loaded square area and estimate drag forces on nearby deep foundations. A case study emerging from similar real life scenario has also been analyzed and results are discussed with suitable recommendations.
9
Korff, Mandy. "Response of piled buildings to the construction of deep excavations". Thesis, University of Cambridge, 2013. https://www.repository.cam.ac.uk/handle/1810/244715.
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Trends in the construction of deep excavations include deeper excavations situated closer to buildings. This research provides insight into mechanisms of soil-structure interaction for piled buildings adjacent to deep excavations to be used in the design and monitoring of deep excavations in urban areas. Most methods to assess building response have originally been developed for tunnelling projects or buildings with shallow foundations. Monitoring data of the construction of three deep excavations for the North South metro Line in Amsterdam, The Netherlands have been used to validate these methods specifically for piled buildings. In all three of the Amsterdam deep excavations studied, the largest impact on the ground surface and buildings is attributed to preliminary activities instead of the commonly expected excavation stage. The in situ preliminary activities caused 55-75% of the surface settlement and 55-65% of the building settlements. Surface settlements measured behind the wall were much larger than the wall deflections and reached over a distance of 2-3 times the excavated depth away from the wall. The shape of the surface settlements found resembles the hogging shape as defined by Peck (1969). For the excavation stage only, the shape of the displacement fits the profile proposed by Hsieh and Ou (1998). Most prediction methods overestimate the soil displacement at depth. An analytical method has been established and tested for the behaviour of piled buildings near excavations. This method includes the reduction of pile capacity due to lower stress levels, settlement due to soil deformations below the base of the pile and development of negative (or positive) skin friction due to relative movements of the soil and the pile shaft. The response of piles in the case of soil displacements depends on the working load of the pile, the percentages of end bearing and shaft friction of the pile, the size and shape of the soil settlements with depth and the distribution of the maximum shaft friction with depth. A method is derived to determine the level for each pile at which the pile and soil settlement are equal. Buildings in Amsterdam built before 1900 and without basement are most sensitive to soil displacements. For all other buildings, the pile settlement depends mainly on the working load. The actual damage experienced in buildings depends also on the relative stiffness of the building compared to the soil. Cross sections in Amsterdam have been evaluated and it is concluded that the Goh and Mair (2011) method provides a realistic, although rather large range of possible modification factors for the deflection of buildings next to excavations, deforming in hogging shape. For the incidents that happened at Vijzelgracht some well known damage indicators have been evaluated.
10
Lusvardi, Cameron Mark. "Blast-Induced Liquefaction and Downdrag Development on a Micropile Foundation". BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8747.
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Frequently, deep foundations extend through potentially liquefiable soils. When liquefaction occurs in cohesionless soils surrounding a deep foundation, the skin-friction in the liquefied layer is compromised. After cyclical forces suspend and pore pressures dissipate, effective stress rebuilds and the liquefied soil consolidates. When the settlement of the soil exceeds the downward movement of the foundation, downdrag develops. To investigate the loss and redevelopment of skin-friction, strain was measured on an instrumented micropile during a blast-induced liquefaction test in Mirabello, Italy. The soil profile where the micropile was installed consisted of clay to a depth of 6m underlain by a medium to dense sand. The 25cm diameter steel reinforced concrete micropile was bored to a depth of 17m. Pore pressure transducers were placed around the pile at various depths to observe excess pore pressure generation and dissipation. Soil strain was monitored with profilometers in a linear arrangement from the center of the 10m diameter ring of buried explosives out to a 12m radius. Immediately following the blast, liquefaction developed between 6m and 12m below ground. The liquefied layer settled 14cm (~2.4% volumetric strain) while the pile toe settled 1.24cm under elastic displacement. The static neutral plane in the pile occurred at a depth of 12m. From 6m to 12m below ground, the incremental skin-friction was 50% compared to pre-liquefaction measurements. The decrease in residual skin-friction is consistent with measurements observed by Dr. Kyle Rollins from previous full-scale tests in Vancouver, BC, Canada, Christchurch, New Zealand, and Turrel, Arkansas.
11
Chen, Jiunn-Rong y 陳俊融. "Negative Skin Friction of Pile Group". Thesis, 1998. http://ndltd.ncl.edu.tw/handle/37618515661382497340.
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碩士國立中央大學
土木工程學系
86
Both self-weight consolidation of a soft soil and excessive withdrawal of groundwater may cause the severe ground subsidence. Pile foundations located in the subsidence area will be subjected to negative skin friction forces (NSF) caused by the downward movements of the soil relative to the pile. These down drag forces may not only increase the axial load in the pile, even damage the structure integrity of the pile body itself, but also cause additional settlement of the structure resting on the pile.The main purpose of the study is to investigate the NSF developing on the instrumented model piles in a pile group due to ground settlements caused both by self- weight consolidation and drawn-down of ground-water tables with a series of centrifuge model piles tests at an acceleration of 50 g. The test package developed herein was capable of regulating the elevation of groundwater by manually controlling the air pressure in the air-water tank rotated at 50 g. Therefore, groundwater withdrawal and recharge processes can be modelled in the centrifuge easily. The instrumented model piles, PPTs, and LVDTs were used to measure the distribution of axial forces along a pile situated at different positions in a pile group, pore water pressures at different elevations, the surface settlements, and pile head settlement in the model tests, respectively. The NSF was continuously measured in the stages of self-weight consolidation and drawdown of ground- water table. The more settlement a pile head, the higher elevations of the neutral point in a pile, and the less NSF developed. The efficiency of pile groups on the NSF was discussed in detail. The NSF developed on a pile in the pile group decreased with the decreasing of pile spacing and with the increasing of numbers of piles. The inner pile developed less amount of NSF than the outer pile in a pile group. However, the efficiency of pile groups may disappear in the case of the pile spacing larger than six times of pile diameter. The predicted values of NSF using a concept of effective numbers of pile compared reasonably well with NSF measured in the model tests. A factor of efficiency of pile groups is proposed and it may be applicable for estimating the total amount of NSF for the different arrangement of pile groups in engineering practice. Recoveries from ground water table will remarkably relief the negative friction induced by the draw-down of ground water table before.
12
Mashhour, Ibrahim. "Negative skin friction on single piles in collapsible soil". Thesis, 2009. http://spectrum.library.concordia.ca/976675/1/MR67251.pdf.
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Collapsible soil is known as problematic soil, which possesses considerable strength when it is dry and loses its strength and experience excessive settlement when inundated. Geotechnical engineers face a great challenge when they build on/in collapsible soil. Inundation of collapsible soil may take place due to surface running water or raising the groundwater level. In case of surface water, the amount of settlement varies, depending on the extent of the wetting zone and the degree of saturation in the soil. The case of rising groundwater will produce full saturation in the ground and accordingly, the maximum settlement of the foundations. In the literature, there is lack of sufficient and reliable methods for predicting drag force on piles embedded in collapsible soils. These difficulties stem from the fact modeling collapsible soil analytically is difficult at best, while collapsible soil is governed by the collapse potential of the soil and method of inundation. In this thesis, the results of an experimental investigation on a single end-bearing pile embedded in collapsible soil will be presented. The objective of this experimental investigation was to measure the soil collapse and the associated settlement and accordingly the negative skin friction on the pile's shaft for a given soil and pile conditions due to soil inundation. Empirical formula is presented to estimate the negative skin friction on these piles for a given soil/pile condition.
13
Shih, Yu-an y 施昱安. "Numerical analysis of negative skin friction in pile foundations". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/43836670404546274919.
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碩士國立中央大學
土木工程研究所
98
This research uses finite difference program FLAC2D to observe negative skin friction behavior of a single pile. The numerical soil model consists of two layer soils, the upper compressible soft clay and the lower gravel bearing layer. The aim of this research is to find the differences of negative friction behavior between friction and end-bearing piles, and to clarify the influences of different loading patterns and bearing conditions. The result shows that the downdrag force of a pile and neutral point location depend on the relative displacement in the interface of pile and soil. Increasing loading magnitude and area will cause more dragload and settlement, while the neutral point moves down in the meantime. Compared with friction pile, end-bearing pile has more dragload and smaller settlement, it is necessary to check the buckling potential of pile material. By varying the stiffness ratio between compressible and bearing layers, the larger the stiffness of bearing layer, the less the pile settlement and the more the pile dragload within 10 times stiffness ratio, but there is no obvious variation when the stiffness ratio is greater than 10. Moreover, applying axial loading then surcharge will have larger dragload than the reverse loading sequence but with similar pile settlement. Therefore, changing loading sequence might be chosen to be one of the ways to reduce dragload.
14
Wang, Wei-Han y 王維漢. "The Behavior Research of Negative Skin Friction acting on Single". Thesis, 1997. http://ndltd.ncl.edu.tw/handle/92012366583640388011.
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碩士國立中央大學
土木工程學系
85
Over pumping groundwater will cause different degree of ground subsidence, and will cause downdrag force to the pile in soil. It is so-called "negative skin friction." It not only increases the settlement of the foundation and the structure rested on the pile, but also increases the axial load of the pile, even damages the pile body and makes it destruct. In order to measure the variation of the axial forces in the pile, the self-designed instrumental model pile made of stainless steel was used in this research. There were five self- designed load cells at the different locations inside the pile. The centrifuge model bed was prepared with the remolded silt in the larger consolidation cell under 1g, and then situated the pile in the center of the soil bed. Besides, five PPTs were located at the different elevations on the wall of model box, and four LVDTs were located at the different positions on the ground surface as well. After reaching 50g and the self- weight consolidation having completed, the groundwater lowering process was simulated by manual controlling the air pressure in the air-water tank. This caused the settlement of the soil bed, and then the negative skin friction occurred. The settlement of the pile itself, the settlement of the soil, the changes of the axial forces of the pile at the different depth, and the variation of pore water pressure were all continuously monitored during the experimental progress. In addition, the value and variation of the skin friction along the pile could be calculated indirectly. This research focused on the negative skin friction occurred due to the settlement of soil around pile. The settlement developed because of the self-weight consolidation and the lowering of the groundwater. The most important was to explore the variation of the skin friction and the position of the neutral point during the whole experimental progress. Besides, numerical or empirical predictive and analytical models were also used in this research. The effective stress methods, the total stress methods, the empirical parameter methods, or other prediction methods were all arranged to establish the analytical model of this research (such as the friction ratio method, the pile-soil spring method, the rigid- plastic method, the elastic-plastic method, etc.). By this way we could predict the value of the negative skin friction and the axial forces of the pile. In addition, we could compare the numerical results with the experimental data of centrifuge model test, recognize the application, and obtain rational provability and explaination. The results of this research show that the compatibility is perfect, this proves that centrifuge is a useful and powerful tool in research of geotechnical engineering.
15
Chen, Chi-ting y 陳紀廷. "A study of negative skin friction developing in point bearing pile and friction pile". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/6z2bj5.
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碩士國立中央大學
土木工程研究所
96
Negative skin friction is one of the most common problems in the design of pile foundations in soft soils, which is governed by soil slip behavior at the pile-soil interface, and highly depends on friction coefficient of interface, surface loading, and axial load. The research designed two types of long-term model pile tests under working load situation, point bearing pile and friction pile, to discuss the mechanism of negative skin friction in different kinds of end bearing layers when its surrounding ground consolidated in multi-stage, which is cyclically added on the ground surface. From the research results, the neutral plane of point bearing pile appears at about 85-90% of the compressible layer, and the incremental axial force of pile rises to 50kg when the surcharge increases to 1kg/cm2. In case of friction pile, the settlement of pile is larger than the one of point bearing pile. The neutral plane obviously moves downward as the surcharge and compact time increases, the location of which ranges between 30 to 50% of the pile length. The incremental axial force of pile rises to 14kg when the surcharge increases to 1kg/cm2. Due to negative skin friction highly developing in point bearing pile, it is suggested to adopt fiction pile for lowering construction cost when the construction only needs low demand of bearing capacity.
16
HSU, HAO-SHIANG y 許皓翔. "Numerical analysis on negative skin friction of pile group with cap". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/31628911188456180320.
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碩士國立中央大學
土木工程學系
101
Since 1960, negative skin friction (NSF) is one of the common problems in the design of pile foundations. In the past, several literatures reports can be found regarding the NSF on single pile and group piles in a compressible clay. NSF induces additional vertical load on the pile and pile settlement. it must to reduce the safety of the structure. The objective of research is to investigate the dragload and downdrag on friction and end-bearing single pile with the finite different package FLAC3D. The simulation results of FLAC3D were compared with the results of FLAC2D to examine their difference. Group piles analysis considers the influence of various parameters including pile group configuration, position of piles in the group, surface loading and pile cap. The group effect are significantly influenced axial force and soil settlement. Finally, using FLAC3D to simulate the NSF of bridge foundations at High Speed Railway when the ground water was dropdown from the ground table to the lower elevation. Based on the results and the comparisons from the analysis for group piles the following conclusions can be drawn: (1)Group effect causes reduction of soil settlement and dragload significantly on pile groups for the relatively small surcharge. The maximum reduction of dragload is obtained in central pile. (2)The magnitude of surface loading increases the group effect decreases. (3) Additional vertical load on friction corner piles was caused by fix-head cap.(4) In the THSR analysis case, when the ground water table was dropdown from the ground table to the depth of 52 meters, NSF would be limit stated to cause the maximum dragload on group piles. It might reduce the bearing capacity of the pile foundations seriously.
17
Kakoli, Sarah Tahsin Noor. "Negative skin friction induced on piles in collapsible soils due to inundation". Thesis, 2011. http://spectrum.library.concordia.ca/7030/1/Kakoli_PhD_S2011.pdf.
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Collapsible soils experience significant volume decrease due to the increase of soil moisture content, with or without an increase in the in-situ stress level. These soils form large parts of North and South America, Eastern Europe, China, Central Asia, Northern and Southern Africa, Russia, Egyptian western dessert, and the continuous deposit from North China to South-East England. As human activities continue to increase in these regions, geotechnical engineers must learn how to deal with these problematic soils. Foundations on collapsible soils suffer from sudden settlement, which may contribute to serious damage or catastrophic failure due to inundation. For relatively light structures, the use of shallow foundations combined with soil replacement or treatment may constitute economical designs. For heavy structures, pile is perhaps the best of alternative available types of foundation.
This subject of significant practical interest has received little attention from the researchers mainly due to the complexity in conducting experimental study. Furthermore, numerical modeling is difficult at best due to the complexity associated in describing the behavior of collapsible soil during inundation. Analytical modeling is not suitable in this respect, as soil grains in collapsible soil undergo radical rearrangements during inundation. In the literature, no design theory can be found to predict the negative skin friction on pile foundation due to inundation of collapsible soil.
Present study presents a numerical model, which is capable to incorporate the effect of inundation of collapsible soil on an axially loaded vertical pile. It employs the theories of unsaturated soil mechanics; including the Soil-Water Characteristic Curve (SWCC) to include the effect of soil suction reduction resulted from the progressive inundation, from two different aspects: change in soil properties, and irrecoverable soil volume change. The proposed numerical model is used to predict negative skin friction exerted on the pile during inundation of collapsible soil surrounding the pile. The numerical model is validated by comparing the numerical results and the experimental data from the literature. Moreover, another numerical modeling procedure is also proposed to design the pile (i.e., length and diameter) in collapsible soil, provided that the indirect load due to negative skin friction is known. An extensive numerical investigation is carried out to identify the parameters (e.g., collapse potential, radius of wetting, pile roughness, etc.) influencing the negative skin friction acting on a pile during inundation. Based on the numerical results, analytical models that can be directly used to predict the indirect load due to negative skin friction are established for both directions (i.e., from bottom and top) of inundation.
Design procedures that can provide adequate positive skin friction and pile capacity in accommodating indirect load due to negative skin friction, are proposed to design the length and diameter of a single pile in collapsible soil subjected to inundation. Present study is useful in reductions in the costs of construction, litigation and remediation in geotechnical engineering practice.
18
Hoque, Mohammad Azizul. "Coupled consolidation model for negative skin friction on piles in clay layers". Thesis, 2006. http://spectrum.library.concordia.ca/8785/1/MR14247.pdf.
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Piles driven in clay are often subjected to indirect loading as a result of the surcharge applied on the surrounding area. During the drained period, both the pile and the soil undergo downward movements caused by the axial and the surcharge loading, respectively. Depending on the relative movement of the pile/soil system, positive and negative skin friction develop on the pile's shaft. Negative skin friction is the drag force that may be large enough to reduce the pile capacity and/or to overstress the pile's material causing fractures or perhaps structural failure or possibly pulling out the pile from the cap. A numerical model was developed to simulate the case of a single pile driven in soft clay layer overlying a deep deposit. Coupled consolidation method of analysis is adopted to predict time/settlement/skin friction distribution relationships. The model is an axisymmetric that uses the finite element technique combined with the soil responses according to Mohr-Coulomb criteria. The model was first tested against the results predicted by the classic theories for bearing capacity of pile foundations on clay. Furthermore, the model was validated with the results of three full scale field tests available in the literature
19
Lai, Kun-cheng y 賴坤成. "A study of influencing factors of negative skin friction by model test". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/66318986026573570796.
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碩士國立中央大學
土木工程研究所
98
This research is mainly to simulate behavior of negative skin friction by applying surface loading on the soft soil layer. The type of pile foundation is end bearing pile. By varying different test parameters and loading sequence. The factors influencing negative friction development have been observed. The research put focus on four influencing factors which are the pre-consolidation stress of clay, the area of loading, the order of applied loading and the existence of thin clay layer. Based on the test results, the surface settlement and the negative skin friction of NC clay are greater than those of OC clay. In case of loading of finite area, the neutral plane is more close to ground surface and the negative skin friction is smaller than that of one dimensional loading. The negative skin friction for the case of loading pile first and then applying surface load is larger than the case in a reverse loading order. The existence of thin clay layer above the bearing layer is more easily to develop negative friction and its value is dependent on the strength of soil layer above the thin clay layer.
20
Habib, Md Ahsan. "Numerical analysis of pile groups in multi-layered soil subjected to negative skin friction". Thesis, 2006. http://spectrum.library.concordia.ca/8738/1/MR14246.pdf.
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Several linear elastic and nonlinear slip models are reported in the literature for predicting negative skin friction on piles and pile groups in consolidating soils. They often produce significantly different results. Moreover, these models are either complex and unfeasible in practice or not capable of taking soil stratification into account, especially in pile groups. These make it difficult for practicing engineers to select appropriate method for predicting negative skin friction. In this thesis, after critically reviewing the existing methods of analysis and examining the inherent mechanisms involved in pile-soil interaction process, a numerical method is proposed for analysis of the negative skin friction on piles and pile groups. The soil response along the depth of the pile is represented by a number of hyperbolic load transfer relationships, each of which relates the load mobilized to the pile at a particular depth and the corresponding relative soil displacement. The method uses conventional laboratory soil test data as input and incorporates nonlinear load transfer mechanism into an iterative finite element framework. A computer program is developed in " Mathematica " programming code to perform this analysis, based on the flowchart developed herein. The results obtained by the proposed procedure compare well with the recent studies and available field data. It is concluded that an iterative finite element approach, coupled with the nonlinear load transfer model, provides a simplified and practical procedure which is capable of predicting the dragload on single or group piles with reasonable accuracy
21
Lin, Tsang-bin y 林滄彬. "Influence of Negative Skin Friction Induced from Liquefaction Settlement on the Piles of a Bridge". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/92790499364192764842.
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碩士逢甲大學
土木工程所
95
In Taiwan, there is a spectial landform where the rivers have a western/eastern trend. It has brought about that the River-Bridge always in meridian trend for connected the highroad. This paper is study for the River-Bridge place in liquefaction area which caused settlement compression on the piles. Base on the way we searched into the drilling records for the Chung Sha Bridge of National Freeway No.1, the Zih-chaing bridge of Taiwan Highway NO.19, and the Chungchang Bridge of Taiwan Highway NO.17 which can be evaluated for soil liquefaction potential and Negative Skin Friction of the piles to compare with the bearing load of the piles. This paper make use of the design earthquake magnitude Mw=7.894 of the Chingshui-Changhua fault rocked anew. In addition, the paper adopted three types of simple computation methods proposed by Seed (1996), Tokimatsu & Yoshimi (1983) and Japan Road & Bridge Association (JRA) (1983), where the three ways are being to be analysed for evaluating influence of Negative Skin Friction induced from liquefaction settlement on the piles. The results acquired from this research show that (1) the bridge foundation of the Chung Sha Bridge of National Freeway No.1 is been effected maximally by soil liquefaction settlement. The Zih-chaing bridge of Taiwan Highway NO.19 is the next. The major reason is that the areas are very easy to incure liquefaction by liquefaction potential evaluation, wherefrom calculation the Negative Skin Friction is 0.46~1.67 times the allowable bearing load. (2) The Chungchang Bridge of Taiwan Highway NO.17 where calculated the Negative Skin Friction is 0.02~0.47 times the allowable bearing load. (3) As show by study, the high soil liquefaction zones engender huge negative effect with the piles of River Bridge. The piles of bridge has rather degree structure harm which inspired by soil liquefaction settlement. Therefore, it is suggested to conduct Negative Skin Friction of from soil liquefaction settlement into the piles design considerations.