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Journal articles on the topic 'Muck pile'
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1
Schenk, F., A. Tscharf, G. Mayer, and F. Fraundorfer. "AUTOMATIC MUCK PILE CHARACTERIZATION FROM UAV IMAGES." ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences IV-2/W5 (May 29, 2019): 163–70. http://dx.doi.org/10.5194/isprs-annals-iv-2-w5-163-2019.
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<p><strong>Abstract.</strong> In open pit mining it is essential for processing and production scheduling to receive fast and accurate information about the fragmentation of a muck pile after a blast. In this work, we propose a novel machine-learning method that characterizes the muck pile directly from UAV images. In contrast to state-of-the-art approaches, that require heavy user interaction, expert knowledge and careful threshold settings, our method works fully automatically. We compute segmentation masks, bounding boxes and confidence values for each individual fragment in the muck pile on multiple scales to generate a globally consistent segmentation. Additionally, we recorded lab and real-world images to generate our own dataset for training the network. Our method shows very promising quantitative and qualitative results in all our experiments. Further, the results clearly indicate that our method generalizes to previously unseen data.</p>
2
Hidden, Scott, and Nariman Abar. "Predesign Foundation Load Test Program for US-17 (Wilmington) Bypass over Northeast Cape Fear River." Transportation Research Record: Journal of the Transportation Research Board 1736, no. 1 (January 2000): 19–23. http://dx.doi.org/10.3141/1736-03.
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The North Carolina Department of Transportation is currently conducting a predesign foundation load test for a new bridge over the Northeast Cape Fear River near Wilmington, North Carolina. The primary purpose of the load test program is to determine whether concrete piles can penetrate a very dense and cemented sand layer and what side friction and tip bearing capacities should be used for the design of the drilled piers. Significant cost savings could be realized if pile foundations instead of drilled piers could support the approach spans of the bridge. For this determination, three concrete piles will be installed 30 m into the ground. Significant cost savings could also be realized by making a more accurate determination of the drilled pier capacities. For this determination, the side friction and tip bearing capacities of the dense Peedee sands and the underlying hard marine clays will be determined with Osterberg cell tests on two 2130-mm-diameter drilled piers. The different subsurface layers (muck, alluvial sands, and Peedee sands) will also be tested laterally with both static and statnamic testing to assist in the foundation design. The load test program incorporates an NCHRP research program on pile groups. The program includes testing a reusable instrumented steel pile group and frame at various sites in various soil conditions around the United States. The load test program results to date, the effect of the results on the foundation design, and the construction, testing, and instrumentation of the drilled piers are described.
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Li, Xiang Long, Dian Shu Liu, Long Fa Luan, Yi Yang, and Zhi Yu Zhang. "Study on the High Bench Cast-Blasting Effects Influenced by Explosive Specific Charge." Advanced Materials Research 250-253 (May 2011): 3763–68. http://dx.doi.org/10.4028/www.scientific.net/amr.250-253.3763.
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Explosive specific charge is the key to the high level of casting blast. In order to study how the explosive specific charge affects the high bench cast blasting, theoretical analysis and experimental study were used in the Hei Dai-gou open pit cast blasting. Experimental study shows that: under the same engineering geological conditions and blasting parameters, the throw distance increases as the average explosives specific charge increases, and this trend slows down gradually. Settlement muck-pile height increases as explosives specific charge increases, and then gently muck-pile shape tends to be more conducive to the work platform dragline flat-field and inverted reactor efficiency. Whenq> 0.65 kg/m3, the cast percentage can reach more than 30%, as 0.67 kg/m3<q<0.70 kg/m3, the cast percentage increases with a significant effect as the explosives specific charge increases; whenq> 0.74 kg/m3, the increasing rate of the cast percentage with the increase of explosive specific charge decreases.
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Miao, Yusong, Yiping Zhang, Di Wu, Kebin Li, Xianrong Yan, and Jie Lin. "Rock Fragmentation Size Distribution Prediction and Blasting Parameter Optimization Based on the Muck-Pile Model." Mining, Metallurgy & Exploration 38, no. 2 (January 22, 2021): 1071–80. http://dx.doi.org/10.1007/s42461-021-00384-0.
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Bamford, Thomas, Filip Medinac, and Kamran Esmaeili. "Continuous Monitoring and Improvement of the Blasting Process in Open Pit Mines Using Unmanned Aerial Vehicle Techniques." Remote Sensing 12, no. 17 (August 29, 2020): 2801. http://dx.doi.org/10.3390/rs12172801.
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The current techniques used for monitoring the blasting process in open pit mines are manual, intermittent and inefficient and can expose technical manpower to hazardous conditions. This study presents the application of unmanned aerial vehicle (UAV) systems for monitoring and improving the blasting process in open pit mines. Field experiments were conducted in different open pit mines to assess rock fragmentation, blast-induced damage on final pit walls, blast dynamics and the accuracy of blastholes including production and pre-split holes. The UAV-based monitoring was done in three different stages, including pre-blasting, blasting and post-blasting. In the pre-blasting stage, pit walls were mapped to collect structural data to predict in situ block size distribution and to develop as-built pit wall digital elevation models (DEM) to assess blast-induced damage. This was followed by mapping the production blasthole patterns implemented in the mine to investigate drillhole alignment. To monitor the blasting process, a high-speed camera was mounted on the UAV to investigate blast initiation, sequencing, misfired holes and stemming ejection. In the post-blast stage, the blasted rock pile (muck pile) was monitored to estimate fragmentation and assess muck pile configuration, heave and throw. The collected aerial data provide detailed information and high spatial and temporal resolution on the quality of the blasting process and significant opportunities for process improvement. The current challenges with regards to the application of UAVs for blasting process monitoring are discussed, and recommendations for obtaining the most value out of an UAV application are provided.
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Cevizci, Halim. "COMPARISON OF COMPUTER AIDED IMAGE ANALYSIS METHODS WITH STANDARD PHOTO METHOD FOR DETERMINATION OF MUCK PILE FRAGMENTATION." Tecnologia em Metalurgia Materiais e Mineração 15, no. 4 (2018): 488–95. http://dx.doi.org/10.4322/2176-1523.20181409.
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Ma, Li, Jianguo Zhang, Chen Xu, Xingping Lai, Qiang Luo, Chendong Liu, and Kemin Li. "Comprehensive Evaluation of Blast Casting Results Based on Unascertained Measurement and Intuitionistic Fuzzy Set." Shock and Vibration 2021 (January 28, 2021): 1–14. http://dx.doi.org/10.1155/2021/8864618.
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In order to make a scientific and accurate evaluation of blast casting results, according to the characteristics of blast casting-dragline stripping system, effective casting rate, looseness coefficient, limit vibration velocity, powder factor, fragmentation distribution, muck pile shape, boulder generation, damage degree of coal seam step, and dust pollution are selected as the evaluation indicators of blast casting results, and a classification standard is established. The unascertained measure theory was adopted to determine the membership degree of influencing factor indicator, which expanded the expression method of fuzzy information of evaluation indicators. The Analytic Hierarchy Process was used to determine the subjective weight of indicators, the entropy weight method was used to determine the objective weight of indicators, and the intuitionistic fuzzy set was used to express the range of the comprehensive weights of indicators. An evaluation model of blast casting results was constructed based on unascertained measurement and intuitionistic fuzzy set. The measured and processed data of blast casting in Heidaigou Open-Pit Coal Mine were calculated by the evaluation model. Besides, the sensitivity of indicator weights to the evaluation result of blast casting results was also analyzed. The results show that the blast casting results are level III (well). The effective casting rate ranks first in terms of the influence on the evaluation result, followed by damage degree of coal seam step, muck pile shape, looseness coefficient, powder factor, dust pollution, limit vibration velocity, and boulder generation/fragmentation distribution, and it was proved that the weight fluctuation of the evaluation indicator has no obvious correlation with weight.
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Han, Ai Hong, and Hui Jun Zheng. "Elasto-Plastic Design of Piled Raft Foundation." Advanced Materials Research 446-449 (January 2012): 588–91. http://dx.doi.org/10.4028/www.scientific.net/amr.446-449.588.
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When the loading sustained by the foundation is large, employing piled raft foundation is one of the best solutions. In the elasto-plastic design of piled raft, piles could improve the differential settlement and reduce raft thickness. As the raft sustains high earth and water pressures, by reducing the span length of raft and excavation depth, one can get economic design. Using elasto-plastic property of the pile is a better method to avoid increasing the pile length and pile diameter and making full capacity of the piled raft foundation in design compared to normal piled raft. With adoption of few small diameter piles, the raft thickness could be reduced significantly. This makes it much better than raft foundation.
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Li, Zheming, Malcolm D. Bolton, and Stuart K. Haigh. "Cyclic axial behaviour of piles and pile groups in sand." Canadian Geotechnical Journal 49, no. 9 (September 2012): 1074–87. http://dx.doi.org/10.1139/t2012-070.
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Piled foundations are often subjected to cyclic axial loads. This is particularly true for the piles of offshore structures, which are subjected to rocking motions caused by wind or wave actions, and for those of transport structures, which are subjected to traffic loads. As a result of these cyclic loads, excessive differential or absolute settlements may be induced during the piles’ service life. In the research presented here, centrifuge modelling of single piles and pile groups was conducted to investigate the influence of cyclic axial loads on the performance of piled foundations. The influence of installation method was investigated and it was found that the cyclic response of a pile whose jacked installation was modelled correctly is much stiffer than that of a bored pile. During displacement-controlled axial load cycling, the pile head stiffness reduces with an increasing number of cycles, but at a decreasing rate; during force-controlled axial load cycling, more permanent settlement is accumulated for a bored pile than for a jacked pile. The performance of individual piles in a pile group subjected to cyclic axial loads is similar to that of a single pile, without any evident group effect. Finally, a numerical analysis of axially loaded piles was validated by centrifuge test results. Cyclic stiffness of soil at the base of pre-jacked piles increases dramatically, while at base of jacked piles it remains almost constant.
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Xie, Chun Ming, and Jun Yang. "Numerical Simulation of Highway Double Curved Arch Bridge Structure Blasting Demolition." Advanced Materials Research 255-260 (May 2011): 1706–10. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.1706.
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Comparative analyzing pre-cutting seam in size between 0.5 m and 0.8 m in the top of bridge arch, and vice-arch column blasting range between 1.6 m and 0.8 m , numerical simulations on typical highway double curved arch bridge structure blasting demolition process are carried out adopting common node separate reinforced concrete model. Simulation result indicates that, common node separate model can reflect mechanical properties difference of concrete and reinforcement through analysis on their loading process. Adopting 0.5 m in size of pre-cutting seam is sufficient to ensure the superposition and complete collapse of the bridge. The vice-arch blasting range by 1.6 m can make the bridge more complete disintegration, and it can also decrease the whole collapse time and the height of muck pile.
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Stupnik, Mykola, Vsevolod Kalinichenko, Mykhailo Fedko, Olena Kalinichenko, and Mykhailo Hryshchenko. "The study of the stress-strain state of the massif in mining uranium at “VOSTGOK” deposits." E3S Web of Conferences 166 (2020): 03005. http://dx.doi.org/10.1051/e3sconf/202016603005.
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Being one of the world’s largest uranium producers(about 2% of the world’s production), the state enterprise “Vostochnyi Mining and Processing Works” (“VostGOK”) provides about 40% of Ukraine’s nuclear power stations with uranium raw materials. Considering the conditions of uranium deposits exploitation (location in densely populated areas, protected sites etc.), to protect the environment from possible emissions of radioactive elements room mining is applied with subsequent backfilling of the dead area with consolidating mixtures. This technology is economically reasonable at deposits with the increased uranium content. To exclude a number of labour-consuming and environmentally dangerous operations from the production process, lean uranium-containing ores are reasonable to be mined applying underground block leaching. This enables reaching maximum values of mineral extraction and avoiding considerable material expenditures on backfilling mixture preparation and backfilling dead rooms, as they are almost completely backfilled with the muck pile, and on utilization of waste after the mined ore primary processing (barren rocks and off-balance ores) on the daylight surface.
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Mangnejo, Dildar Ali, and Naeem Mangi. "The Responses of an End-Bearing Pile to Adjacent Multipropped Excavation: 3D Numerical Modelling." Civil Engineering Journal 5, no. 3 (March 18, 2019): 552. http://dx.doi.org/10.28991/cej-2019-03091267.
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It is well recognised that superstructure load is transferred to surrounding soil through piled foundation. Consequently, the high stress regime (stress bulb) is generated surrounding of the pile. On the other hand, the excavation in the ground inevitably results in the ground movement due to induced-stress release. These excavations are sometimes inevitable to be constructed adjacent to existing piled foundations. This condition leads to a big challenge for engineers to assess and protect the integrity of piled foundation. This research presents three-dimensional coupled consolidation analyses (using clay hypoplastic constitutive model which takes account of small-strain stiffness) to investigate the responses of an end-bearing pile due to adjacent excavation at different depths in soft clay. The effects of excavation depths (i.e., formation level) relative to pile were investigated by simulating the excavation near the pile shaft (i.e., case S) and next to (case T). It was revealed that the maximum induced bending moment in the pile after completion of excavation in all the cases is much less than the pile bending moment capacity (i.e. 800 kNm). Comparing the induced deflection of the end-bearing pile in the case T, the pile deflection in case S is higher. Moreover the piles in cases of S and T were subjected to significant dragload due to negative skin friction.
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Vu, Anhtuan, Ducphong Pham, Tuonglai Nguyen, and Yu He. "3D Finite Element Analysis on Behaviour of Piled Raft Foundations." Applied Mechanics and Materials 580-583 (July 2014): 3–8. http://dx.doi.org/10.4028/www.scientific.net/amm.580-583.3.
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This paper highlights settlement behaviour of piled raft foundation by 3D finite element analysis through Plaxis 3D Foundation program. The effects of pile number, pile length, pile layout and pile spacing on the behaviour of piled raft foundation were studied. The numerical results show that: Piled raft foundation has much more efficency to reduce settlement than that of traditional raft foundation. The value of vertical defomation decreases as the result of the increase of pile number, pile length, pile spacing and vice versa. Pile layout has significant effect on both value and location of maximum settlement of piled raft foundation.
14
Pando, Miguel, George Filz, Carl Ealy, and Edward Hoppe. "Axial and Lateral Load Performance of Two Composite Piles and One Prestressed Concrete Pile." Transportation Research Record: Journal of the Transportation Research Board 1849, no. 1 (January 2003): 61–70. http://dx.doi.org/10.3141/1849-08.
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Composite piles use fiber-reinforced polymers (FRPs), plastics, and other materials to replace or protect steel or concrete, with the intent being to produce piles that have lower maintenance costs and longer service lives than those of conventional piles, especially in marine applications and other corrosive environments. Well-documented field loading tests of composite piles are scarce, and this lack of a reliable database may be one reason that composite piles are not in widespread use for load-bearing applications. The purpose of this research is to compare the axial and lateral load behavior of two different types of composite test piles and a conventional prestressed concrete test pile at a bridge construction site in Hampton, Virginia. One of the composite piles is an FRP shell filled with concrete and reinforced with steel bars. The other composite pile consists of a polyethylene plastic matrix surrounding a steel reinforcing cage. The axial structural stiffnesses of the prestressed concrete pile and the FRP pile are similar, and they are both much stiffer than the plastic pile. The flexurel stiffness of the prestressed concrete pile is greater than that of the FRP pile, which is greater than the flexural stiffness of the plastic pile. The axial geotechnical capacities of the test piles decreased in order from the prestressed concrete pile to the FRP pile to the plastic pile. The prestressed concrete pile and the FRP pile exhibited a similar response for lateral load versus deflection, and the plastic pile was much less stiff in lateral loading.
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Hemami, A. "AN APPROXIMATION OF THE WEIGHT OF THE LOADED MATERIAL DURING THE SCOOPING OPERATION OF A MECHANICAL LOADER." Transactions of the Canadian Society for Mechanical Engineering 18, no. 3 (September 1994): 191–205. http://dx.doi.org/10.1139/tcsme-1994-0011.
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As part of a study towards automation of the loading process in a mechanical loader, in excavation or a reclaiming operation from a muck pile, the forces involved in the scooping action must be analyzed. In the present approach, the cutting edge of a bucket is regarded as the tool point for a robot manipulator. The loader, itself, is considered to be a robot arm for which the relevant knowledge and state of the art in robotics can be utilized for automation of its operation. There are five forces at each instant during scooping that must be provided for the bucket by the actuators moving the bucket. These forces are: The weight of material to be moved; the force towards pushing, pressing and compacting the material; the friction forces; the digging or cutting force; and the dynamic or inertia forces for the motion. Analysis of these forces and formulating their variation during scooping needs a great deal of theoretical and experimental research. This work is confined to the first force, the weight of the loaded material. After a general description of all these forces, approximate expressions are derived for the calculation of this force in terms of the parameters of motion and dimensions of a loader bucket.
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Lu, Chen Yuan, Shu Na Lai, and Fan Li Meng. "Experiment Study of the Uplift Mechanism of Disk Piles." Advanced Materials Research 250-253 (May 2011): 1578–81. http://dx.doi.org/10.4028/www.scientific.net/amr.250-253.1578.
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Based on the analysis of the uplift mechanism theory of the disk piles, a model test device was designed to study the uplift bearing capacity and deformation behavior of the disk piles and to compare with the equivalent diameter piles. Uplift loading tests were carried out on the equivalent diameter pile, the single-disk pile and the double- disk pile respectively. Through the test, it was proved that the uplift bearing capacity of the disk piles was much better than the equivalent diameter pile. The bearing capacity of the single-disk piles was better than the double-disk piles in the test. This was mainly related to the embedded depth of the upper disk was not enough and the specific failure mode. So, a reasonable design was necessary.
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Jayasinghe, Laddu Bhagya, Daniele Waldmann, and Junlong Shang. "Impact of Pile Punching on Adjacent Piles: Insights from a 3D Coupled SPH-FEM Analysis." Applied Mechanics 1, no. 1 (February 21, 2020): 47–58. http://dx.doi.org/10.3390/applmech1010004.
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Pile punching (or driving) affects the surrounding area where piles and adjacent piles can be displaced out of their original positions, due to horizontal loads, thereby leading to hazardous outcomes. This paper presents a three-dimensional (3D) coupled Smoothed Particle Hydrodynamics and Finite Element Method (SPH-FEM) model, which was established to investigate pile punching and its impact on adjacent piles subjected to lateral loads. This approach handles the large distortions by avoiding mesh tangling and remeshing, contributing greatly high computational efficiency. The SPH-FEM model was validated against field measurements. The results of this study indicated that the soil type in which piles were embedded affected the interaction between piles during the pile punching. A comprehensive parametric study was carried out to evaluate the impact of soil properties on the displacement of piles due to the punching of an adjacent pile. It was found that the interaction between piles was comparatively weak when the piles were driven in stiff clays; while the pile-soil interactions were much more significant in sandy soils and soft clays.
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Qian, Shuang Bin, and Li Hua Zhang. "Research of Load-Bearing and Deformation Characteristics of Long-Short Pile Composite Foundation." Applied Mechanics and Materials 256-259 (December 2012): 592–95. http://dx.doi.org/10.4028/www.scientific.net/amm.256-259.592.
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Long-short composite pile is a widely used ground improvement technique. This study presents the results of finite difference analyzes using FLAC3D software to investigate the load-bearing and deformation behavior of long-short pile composite foundation under various load distributions. The pile-soil load-sharing ratio and stress ratio, axial force distribution in the piles, pile side friction resistance distribution, and settlement behavior are also studied. The results show that settlement is much more significantly affected by long-pile rather than short-pile. On the other hand, the load distribution between piles and subsoil is significantly affected by the cushion.
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Zhou, Ke Feng, and Yu Zhi Li. "Computer Modeling for the CFG Pile in Highway Soft Foundation." Applied Mechanics and Materials 84-85 (August 2011): 421–25. http://dx.doi.org/10.4028/www.scientific.net/amm.84-85.421.
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In past 10 years, composite foundations, especially multipile composite foundations have been extensively used. Multi-pile composite foundation is a method of ground improvement that involves using different pile types with different lengths and diameters beneath the same raft. The CFG piles are generally much stiffer than lime piles and they are used in a manner similar to that used for conventional piles; that is, to mobilize bearing capacity from the deeper soil strata. This paper presents the results of a series of three dimensional (3D) finite element analyzes on CFG–lime composite pile foundations. The parameters investigated are the spacing of CFG pile and cushion thickness.
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Wen, Xiao Gui, An Sun, Hui Ming Wu, and Wen Tao Wang. "Analysis of Relationship between Pile Quality and its’ Bearing Capacity." Advanced Materials Research 163-167 (December 2010): 3517–22. http://dx.doi.org/10.4028/www.scientific.net/amr.163-167.3517.
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Bored pile is one of the most widely used foundation forms in civil engineering. Relationship between pile quality and its’ bearing capacity is seldom been discussed. This paper introduces 8 bored piles in one storage tank project in Ningbo, of which 4 piles are done vertical load tests; the other four are done lateral load tests. Combined with their quality, the results reveal that when load is small, pile quality has much influence on pile bearing capacity. As soon as load is large enough to transfer to pile bottom, quality of concrete at pile bottom becomes the main factor that impacts pile vertical capacity, meanwhile pile horizontal bearing capacity mainly depends on pile length. Post-grouting is done to improve pile quality. It raises pile’s bearing capacity while reducing differential settlement at the same time.
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Hong, Y., B. He, L. Z. Wang, Z. Wang, C. W. W. Ng, and D. Mašín. "Cyclic lateral response and failure mechanisms of semi-rigid pile in soft clay: centrifuge tests and numerical modelling." Canadian Geotechnical Journal 54, no. 6 (June 2017): 806–24. http://dx.doi.org/10.1139/cgj-2016-0356.
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Previous studies on laterally loaded piles in clay have mainly focused on flexible and rigid piles. Little attention has been paid to semi-rigid piles (whose pile–soil stiffness lies somewhere between those of rigid and flexible piles), which may behave as either flexible piles or rigid piles, depending on the change in soil stiffness during cycling. This study aims to understand the cyclic lateral response of a repeatedly loaded semi-rigid pile in soft clay and the failure mechanisms of the soil around the pile, through a series of centrifuge model tests and three-dimensional finite element analyses using an advanced hypoplastic clay model. Numerical parametric studies were also performed to investigate the evolution of soil flow mechanisms with increasing pile rigidity. It is revealed that the semi-rigid pile behaved as if it were a flexible pile (i.e., flexural deformation dominated) during the first few cycles, but tended to behave like a rigid pile (i.e., rotational movement prevailed) during subsequent cycles, which progressively softened the surrounding soil. As a result, the mechanisms of soil flow around the semi-rigid pile exhibited an intermediate behaviour combining the mechanisms of both flexible and rigid piles. Three distinctive mechanisms were identified: a wedge-type mechanism near the surface, a full-flow mechanism (within the transverse sections) near the middle of the pile, and a rotational soil flow mechanism (in the vertical symmetrical plane of the pile) near the lower half of the pile. By ignoring the rotational soil flow mechanism, which has a much lower resistance than the full-flow mechanism, the American Petroleum Institute code (published in 2007) underestimated the cyclic bending moment and the lateral pile displacement by 10% and 69%, respectively. Application of jet grouting around the semi-rigid pile at shallow depth significantly altered the soil flow mechanism (i.e., it was a solely wedge-type mechanism around the grouted zone).
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Cao, Wei Ping, and Min Zhao. "Performance of Floating Piles for Supporting Embankments in Soft Soils." Applied Mechanics and Materials 105-107 (September 2011): 1433–37. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.1433.
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Reinforced concrete piles are often used to support highway embankments in soft soils. The performance of floating piles differs significantly from that of end-bearing piles. A numerical analysis was conducted to investigate the soil stress concentration ratio, pile and soil settlements, pile axial force, negative skin friction (NSF) and the location of the neutral plane (NP) during embankment filling and consolidation of soft soils when the soft soils is treated by using reinforced concrete floating piles. The results indicate that the pile axial force as well as negative skin friction is closely time dependent and increase much more quickly during the embankment filling than during the consolidation. The location of the NP exhibits a complicated variation as the pile head loads and the surcharge applied on the soft soils are varying with time. Most of the embankment load is born by pile for the existence of soil arch within the embankment.
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Du, Shengtao, and Bingchen Liang. "Comparisons of Local Scouring for Submerged Square and Circular Cross-Section Piles in Steady Currents." Water 11, no. 9 (August 31, 2019): 1820. http://dx.doi.org/10.3390/w11091820.
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The local scouring that occurs around submerged vertical piles in steady currents was studied experimentally in this paper. Three experiments were carried out for square cross-section (SC) piles and a circular cross-section (CC) pile with the same width. The key point scour depths, including the center of the upstream boundary point (KC) and the two upstream corners (KM), were observed over time. The two-dimensional profiles and the three-dimensional topography around each pile were measured using a Seatek. The different scouring characteristics of the SC and CC piles were investigated. The experiment results show that the scour depth at KC is much smaller than that of KM. The equilibrium scour depth of the CC pile is far less than that of the SC piles. The scour and deposition distributions were different between the CC and SC piles. The maximum scour depth was found at the lateral rear of the CC pile, and the maximum deposition was observed in sections of the SC piles. The evolutions of the scour depths at KM are predicted using a developed exponential equation.
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Li, Hong-Yuan. "Comparison and analysis of pile-soil separate calculation and composite foundation calculation method for gravel pile reinforcement." E3S Web of Conferences 237 (2021): 03010. http://dx.doi.org/10.1051/e3sconf/202123703010.
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This paper uses Indraratna seepage theory, Han pile-soil seepage theory and composite foundation theory to establish three plane strain models. Through finite element calculations, the changes in pore pressure and settlement are compared, and the following laws are found: (1) The model established by the composite foundation theory cannot reflect the objective laws of seepage and deformation; (2) In the case of multiple piles, there is no difference in settlement between Han pile-soil seepage theory considering the bearing characteristics of gravel piles and Indraratna seepage theory without considering the bearing characteristics of gravel piles. (3) The settlement value obtained by the principle of composite foundation is much smaller than the settlement value obtained by the separate calculation of pile and soil.
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SHAPOVAL, A. B., and M. G. SHNIRMAN. "SAND DENSITY AS SANDPILE DESCRIPTOR." International Journal of Modern Physics C 19, no. 06 (June 2008): 995–1006. http://dx.doi.org/10.1142/s0129183108012637.
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We investigate a collection of one-parametric families of isotropic sandpile models. The models involve the square lattice slowly accumulating the grains and quickly transferring them as the local piles become over-critical. The paper groups the sand-piles with respect to two features influencing the model dynamics. They are the value of the local transfer's stochasticity and the number of the transferred grains. Every pair generates one-parametric family of the sand-piles. The parameter reflects the relative height of an over-critical pile with respect to the incoming flow of sand. If the stochasticity disappears with the growth of the parameter, the families with the fixed number of the transferred grains have much in common with Bak et al.'s sand-pile [Phys. Rev. Lett.59, 381 (1987)], while the families, whose over-critical piles lose all their grains, tend to the Zhang sand-pile [Phys. Rev. Lett.63, 470 (1989)]. The families with non-disappearing variance give rise to new properties described in terms of the probability distribution of the pile heights.
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Fattah, Mohammed Y., Hussein H. Karim, and Makki K. M. Al-Recaby. "Investigation of the end bearing load in pile group model in dry soil under horizontal excitation." Acta Geotechnica Slovenica 18, no. 1 (2021): 79–106. http://dx.doi.org/10.18690/actageotechslov.18.1.79-106.2021.
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A series of 94 laboratory tests were conducted to measure the response of pile foundation when subjected to dynamic loads. Eight tests were conducted on single pile in dry soil at relative density 30 % (loose) and 50 % (medium); 66 tests on group of piles with different spacings and patterns. All tests were carried out under operating frequencies 0.5, 1 and 2 Hz under horizontal shaking. All tests were achieved with one embedment ratio (L/d = 30). These tests were grouped in three different numbers of piles; 2 piles in row and line patterns, 3 piles and 4 piles; and three pile spacing ratios (s/d = 3, 4 and 5). The results of dry soil indicating the mechanism of dynamic response of piles and soil subjected to dynamic horizontal shaking include the variation and distribution of acceleration with time in different states of soil in addition to the vertical and horizontal displacements, end-bearing load, peak acceleration and the peak velocity of foundation. It was concluded that for a dry soil bed, the acceleration amplitudes increase with frequency for both soil relative densities (loose and medium) and different pile patterns (number; single or group and different spacing ratios s/d). The maximum acceleration in the foundation is lower than in the soil bed for all operating shaking frequencies, pile spacing ratios and soil states. The decreasing of the maximum acceleration recorded in the foundation as compared to that in the soil bed is between 10-100 % for loose and medium state of soil, and the decrease in loose state is more than in medium state. This means that there is damping effect or attenuation of vibration waves. The amplitudes of recorded acceleration in the pile cap are much higher than in the soil bed for single pile and pile group with different pile spacing ratios, also these amplitudes are increasing with increase of shaking frequency and relative density of the soil.
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Qian, Shuang Bin, and Li Hua Zhang. "Research of Deformation Characteristics of Long-Short Pile Composite Foundation under Rigid Foundation." Applied Mechanics and Materials 638-640 (September 2014): 694–98. http://dx.doi.org/10.4028/www.scientific.net/amm.638-640.694.
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Long-short composite pile is a widely used ground improvement technique. This study presents the results of finite difference analyzes using FLAC3D software to investigate the deformation behavior of long-short pile composite foundation under rigid foundation. The pile penetration into cushion and displacement distribution in the piles and other parameters are also studied. The results show that settlement is much more significantly affected by long-pile rather than short-pile. On the other hand, long-pile pierce into cushion to bring foundation soil into full play, also makes the advantages of long-short pile composite foundation to be evident.
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Guo, Shao Zeng, and Run Liu. "Buckling Analysis of Pile during Hammer Placement." Applied Mechanics and Materials 256-259 (December 2012): 467–70. http://dx.doi.org/10.4028/www.scientific.net/amm.256-259.467.
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Large diameter and thin thickness are the main characteristics of the steel pipe piles in offshore engineering. Before piling a pile, heavy hammer will be placed on the top of it, which may emerge a serious risk in pile buckling. A three dimensional finite element model of pile and soil was established for a case study. The modified Riks method which can automatically search a suitable increment factor of loads is adopted to assess the stability of the pile, and the geometric nonlinearity and pile-soil interaction were both considered. The practical example shows that the critical load considering pile-soil interaction is much smaller than that in a fixed constraint.
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Xue, Jiang Wei, Yong Yang, Yi Zhao, and Xin Sheng Ge. "Three-Dimensional Analysis of the Partner of Laterally Loaded Variable Rigidity Pile (Pile Partner)." Applied Mechanics and Materials 256-259 (December 2012): 320–23. http://dx.doi.org/10.4028/www.scientific.net/amm.256-259.320.
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Concerning the stress and displacement of the partner under lateral load, reference on full-scale model tests on behavior of cast-in-place concrete pipe piles, two cases are analyzed by means of 3D finite element method, calculations show that in condition I, pile and cap rigid joint (pile foundation) plus partner, partner block the punching stress from pile top to cap continue to spread; and in condition II, the distance between pile top and pile cap is 200 mm, partner is in normal bending shear state; As the flexural rigidity of partner is much larger than the pile, if under earthquake or other rare action, partner may sacrifice firstly to keep pile perform well.
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Raongjant, Werasak, and Meng Jing. "Back-Analysis for Design Parameters of Large Diameter Bored Piles." Advanced Materials Research 671-674 (March 2013): 186–89. http://dx.doi.org/10.4028/www.scientific.net/amr.671-674.186.
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Field test data from three instrumented large diameter bored piles in Pattaya city of Thailand were analyzed to study the behavior of load transfer mechanism from the pile to soil. The pile load test data were obtained from conventional static load test. These bored piles used for conventional static load test have the same diameter of 0.80 m and different length in the range of 25 m to 32 m. Results from back-analysis found that the skin friction resistance, β, has the value between 0.20 and 0.64 and the bearing capacity at end of piles, Nq, which is in the range of 10 to150, is much lower than the theoretical values proposed by other researchers before.
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Zhang, Sifeng, Guojian Zhang, Xinyu Zhang, Luchuan Chen, and Shuai Zheng. "Influences on Antislide Piles Used for Slope Reinforcement: Numerical Simulation Based on the Soil Arching Effect." Mathematical Problems in Engineering 2020 (November 17, 2020): 1–15. http://dx.doi.org/10.1155/2020/7651080.
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This study explores the pile-soil interaction mechanism and the optimal use of antislide piles for slope reinforcement based on finite difference numerical modelling. The force and displacement principles of slopes and antislide piles are analysed. The influences of various factors are investigated, such as postpile filling parameters, pile embedding methods, and pile cross-sectional shapes. Numerical modelling is used to determine the optimal layouts of antislide piles for push and traction landslides. The findings indicate that the cohesive force of the fill has a greater influence on the piles and slope than the friction angle and is the primary control factor. Fully buried antislide piles provide a better antisliding effect than semiburied ones. With fully buried piles, the best controlling effect is obtained when the ratio of the length of the pile’s free section to the height of the sliding body is approximately 4/5. Moreover, stepped-cross-section piles provide better slope reinforcement than those with rectangular, T-shaped, or trapezoidal cross-sections. In practical applications, end-bearing arches can be utilized as the primary control structures, with friction arches used for secondary control to improve the soil arching effect as much as possible, thereby enhancing the stability of the piles and slope. To control landslides of various thrust forms, antislide piles should be set in the active section, the core sliding section, or both, as required. This paper provides guidance for improving the design of antislide piles.
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Krasiński, Adam, and Tomasz Kusio. "Pile Model Tests Using Strain Gauge Technology." Studia Geotechnica et Mechanica 37, no. 3 (September 1, 2015): 49–52. http://dx.doi.org/10.1515/sgem-2015-0032.
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Abstract Ordinary pile bearing capacity tests are usually carried out to determine the relationship between load and displacement of pile head. The measurement system required in such tests consists of force transducer and three or four displacement gauges. The whole system is installed at the pile head above the ground level. This approach, however, does not give us complete information about the pile-soil interaction. We can only determine the total bearing capacity of the pile, without the knowledge of its distribution into the shaft and base resistances. Much more information can be obtained by carrying out a test of instrumented pile equipped with a system for measuring the distribution of axial force along its core. In the case of pile model tests the use of such measurement is difficult due to small scale of the model. To find a suitable solution for axial force measurement, which could be applied to small scale model piles, we had to take into account the following requirements: - a linear and stable relationship between measured and physical values, - the force measurement accuracy of about 0.1 kN, - the range of measured forces up to 30 kN, - resistance of measuring gauges against aggressive counteraction of concrete mortar and against moisture, - insensitivity to pile bending, - economical factor. These requirements can be fulfilled by strain gauge sensors if an appropriate methodology is used for test preparation (Hoffmann [1]). In this paper, we focus on some aspects of the application of strain gauge sensors for model pile tests. The efficiency of the method is proved on the examples of static load tests carried out on SDP model piles acting as single piles and in a group.
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Chi, Wang, Yong Fu Xu, and Ping Dong. "Bearing Capacity of Concrete-Cored DCM Pile Composite Ground." Advanced Materials Research 712-715 (June 2013): 951–54. http://dx.doi.org/10.4028/www.scientific.net/amr.712-715.951.
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The concrete-cored DCM pile is an kind of composite pile by inserting the inner concrete pile into the DCM column socket. In two test sites, plate load test is used to measure bearing capacity of concrete-cored DCM pile composite ground. Vertical stress of surrounding soil and DCM column socket are measured by pressure cells. The axial force of precast core pile can be obtained by steel stressmeters which welded on the reinforcing steel along depth. The field tests results show that, the bearing capacity of concrete-cored DCM pile composite ground is much larger than that of original soil. The development degree of concrete-cored DCM pile bearing capacity in composite foundation increases steadily during the loading process. Both concrete-cored DCM piles and surrounding soils play an important effect on the bearing capacity of composite foundation.
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Wang, L. Z., K. X. Chen, Y. Hong, and C. W. W. Ng. "Effect of consolidation on responses of a single pile subjected to lateral soil movement." Canadian Geotechnical Journal 52, no. 6 (June 2015): 769–82. http://dx.doi.org/10.1139/cgj-2014-0157.
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Given extensive research carried out to study pile response subjected to lateral soil movement in clay, the effect of consolidation on the pile–soil interaction is rarely considered and systematically investigated. For this reason, four centrifuge tests were conducted to simulate construction of embankment adjacent to existing single piles in soft clay, considering two typical drainage conditions (i.e., drained and undrained conditions) and two typical pile lengths (i.e., relatively long pile and short pile). The centrifuge tests were then back-analyzed by three-dimensional coupled-consolidation finite element analyses. Based on reasonable agreements between the two, numerical parametric studies were conducted to systematically investigate and quantify the influence of construction rate and pile length on pile response. It is revealed that by varying drainage conditions, the piles respond distinctively. When the embankment is completed within a relatively short period (cvt/d2 < 2, where cv, t, and d denote the coefficient of consolidation, construction period, and pile diameter, respectively), the pile located adjacent to it deforms laterally away from the embankment. Induced lateral pile deflection (δ) and bending moment reduce with construction period. On the contrary, embankment constructed within a relatively long period (cvt/d2 > 200) leads the pile to deform laterally towards the embankment, with δ and bending moment increases with construction period. By halving the length of pile embedded in the drained ground, the maximum induced bending moment (BMmax) was slightly reduced (by 23%). On the other hand, shortening the length of the pile in the undrained ground is much more effective in reducing BMmax, i.e., halving pile length resulting in 78% reduction in bending moment. A new calculation chart, which takes various drainage conditions and pile lengths into account, was developed for estimation of BMmax.
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Ding, Wang, Zhang, Liang, Tian, and Qi. "The Recycling Torque of a Single-Plate Helical Pile for Offshore Wind Turbines in Dense Sand." Applied Sciences 9, no. 19 (October 1, 2019): 4105. http://dx.doi.org/10.3390/app9194105.
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The helical piles have been being treated as a kind of novel foundation for offshore wind turbines recently, due their fast installation, high uplift capacity, convenience for recycling, and other advantages. The recycling of the helical pile especially will reduce the cost significantly and protect the environment as much as possible. However, the research for this area is basically in infancy and there is no reference for predicting the recycling torque of a helical pile in sand. In order to predict the recycling torque of single-plate helical piles in dense sand: a theoretical model, which was inspired by the way to predict the installation torque of single-plate helical pile in sand, was developed, and a series of single gravity model tests were conducted to verify that theoretical model. The theoretical model can predict the recycling torque of single-plate helical pile considering the influences of the size of helix and the vertical force on the shaft. This model fills in the blank of predicting the recycling torque of a single-plate helical pile in sand and it is also useful guidance for the choice of suitable recycling equipment.
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Saragih, Deardo Samuel, Novdin Manoktong Sianturi, Virgo Erlando Purba, and Dermina Roni Santika Damanik. "The Potential Of Steel Wire As A Binder With Plates To Withstand Loads." TEKNIK 41, no. 3 (November 25, 2020): 219–24. http://dx.doi.org/10.14710/teknik.v41i3.29936.
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Road and bridge construction needs to be supported by a strong system, both in terms of material and connections between structural elements. A pile reinforcement connection system with slab support construction on it needs to be considered to work together in carrying the load. Therefore, research is needed to determine how much effect the steel wire has as a binding pile with a plate in resisting uniform loads on it. This research was conducted by testing the model in a laboratory on a test medium that was reinforced with the pile with the slab system. Pile joints are distinguished bound perfectly and unbound. A reduction settlement analysis is performed on the difference in settlement for bound and unbound piles. The results showed that the pile system's performance, which was bound with steel wires on the slab, was better at resisting loads. This is known from the reduction of settlement for bound and unbound piles, which is 11.43% for the time stage and 11.51% for the load stage. The system can work together so that the stability of construction is better maintained and more durable.
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Jiang, Xue Liang, Hui Yang, and Jun Fu. "An Improved Shearing Displacement Law for Analyzing Pile-Soil Interaction." Advanced Materials Research 639-640 (January 2013): 581–86. http://dx.doi.org/10.4028/www.scientific.net/amr.639-640.581.
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The Soil Improved shearing displacement law is used to analyze Pile-soil interaction and this method can consider stratified foundation, but can’t consider pile-soil slip. An improved shearing displacement law analyzing pile-soil interaction was proposed in this article which could think over pile-soil slip on interfaces and interaction of pile-soil on stratified foundation. Rock and soil’s parameter is very crucial in geological engineering, the soil parameters were determined by parameter back analysis theory and the stress and deformation characteristic for vertical loading piles were analyzed by the improved shearing displaces law. These process was simulated by my own program. The calculation results show that the axial force of pile decreases with pile depth and the pile tip axial force is zero. The pile bottom resistance increases with load and the soil’s resistance increases with the relative displacement between pile and soil. But,the frictional resistance growth rate with displacement is different in different soil. The silt’s growth rate is minimum and the medium-fine sand mixed mucky soil is maximum. The pile frictional resistance increases with load and depth. It has greater directive significance for the pile design.
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Peng, Hua, Xiao Qi Xiao, and Zhi Yong Dong. "Study on Deformation Influence of Deep Foundation Pit Pile-Anchor Supporting System Nearby Metro Structure." Applied Mechanics and Materials 638-640 (September 2014): 1190–94. http://dx.doi.org/10.4028/www.scientific.net/amm.638-640.1190.
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In the big cities, any construction nearby the metro structure become critical to the safety of the metro,especially for deep foundation pit engineering.In such case,Pile-anchor supporting system is normally used, however different deformation shape of the supporting wall will bring different deformation of the metro structure.This paper analysed the relations between the pile-anchor supporting system and the nearby metro structures and stated how to control the nearby metro structure deformation through the design of the Pile-anchor supporting system.The analysis showed the following conclusions:If the nearby metro structure is closer to the ground surface, it will be more sensitive to the deformation of the piles-anchor system;Shape 1 & 2 are better to control the metro structure deformation,Shape 3 will result bigger settlement;the metro structure above and in the middle of the foundation bottom level are very much influenced by the deformation of the piles;If the deformation of metro structure exceeds the allowable value, other measures should be considered.
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Wang, Xing Yun, Bin Peng, Xiao Chao Tang, and Lian Fan. "Study on the Friction Transfer Rule of Piles in the Slope under the Vertical Load." Applied Mechanics and Materials 423-426 (September 2013): 1296–300. http://dx.doi.org/10.4028/www.scientific.net/amm.423-426.1296.
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The pile friction regular pattern in the slope has much difference with piles in the ground. By using the finite-difference software FLAC3D,the pile friction under the vertical load is studied. The regular pattern and influence factors are analyzed. The results show that there is a significant difference contrasting the friction of both sides of the pile. For the point of value, the friction closed to the slope-side is smaller than the friction away from the slope-side. The average is 60% to 70%. For the distribution, the friction closed to the slope-side decreases rapidly with the depth of the pile. The friction away from the slope-side distributes relatively evenly. The slope ratio and the pile location have a great impact on the friction. The friction has a negative correlation with the slope ratio, and has a positive correlation with the pile distance.
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Sato, Takashi, Kazuo Konagai, Takaaki Ikeda, and Hiroaki Nishi. "Effect of surface layer freeze to soil-pile interaction." MATEC Web of Conferences 265 (2019): 05001. http://dx.doi.org/10.1051/matecconf/201926505001.
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To assess earthquake resistance of new or existing structures and predict earthquake damage of structures, it is important to properly evaluate the response of the structure at the time of the earthquake. In cold regions however, where the ground can freeze in winter, the dynamic soil-foundation interaction can change with the change in the density and stiffness of the frozen side soil. This paper examines in a quantitative manner, the influence of freezing of ground on the dynamic soil grouped piles interaction., It is shown herein that the grouped piles in the frozen ground tend to follow the motion of the ground over a wider range of frequency. Furthermore, it is shown that even when the freezing depth is much thinner than the characteristic length of piles determined by the stiffness ratio of the ground and the group pile, the pile cap stiffness at the time of freezing becomes noticeably large. It is confirmed that the freezing of the ground can greatly affect the interaction between the ground and the piles.
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Robertson, P. K., D. J. Woeller, and D. Gillespie. "Evaluation of excess pore pressures and drainage conditions around driven piles using the cone penetration test with pore pressure measurements." Canadian Geotechnical Journal 27, no. 2 (April 1, 1990): 249–54. http://dx.doi.org/10.1139/t90-029.
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Large-diameter steel pipe piles were driven as part of the foundations for the Alex Fraser Bridge near Vancouver, British Columbia. The piles penetrated through a normally consolidated marine clayey silt. As part of the geotechnical studies a multipoint piezometer was installed close to the pile group. A cone penetration test with pore pressure measurements (CPTU) was performed adjacent to one of the piles shortly after driving. During the CPTU through the clayey silt deposit, dissipation tests were performed to evaluate the pore pressures around the nearby pile. The CPTU results are compared with the pore pressures recorded at the multipoint piezometer, allowing for differences in radial distance from the piles. Excellent agreement was obtained between the CPTU and multipoint piezometer data, both showing large excess pore pressures around the piles. The CPTU dissipation data were also analyzed to evaluate the time required for dissipation of excess pore pressures around the piles. The upper half of the clayey silt deposit was inter bedded with thin sand and silt layers. The CPTU data showed that the thin sand layers were sufficiently large in extent to allow rapid dissipation of the pore pressures due to cone penetration but were not of sufficient extent to allow dissipation of the excess pore pressures from the much larger diameter piles. Key words: in situ, piles, pore pressures, CPT.
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Basu, Dipanjan, Rodrigo Salgado, and Mônica Prezzi. "A new framework for analysis of laterally loaded piles." Journal of Geo-Engineering Sciences 1, no. 1 (2013): 53–67. http://dx.doi.org/10.3233/jgs-13007.
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A new analysis framework is presented for calculation of the response of laterally loaded piles in multi-layered, heterogeneous elastic soil. The governing differential equations for the pile deflections in different soil layers are obtained using the principle of minimum potential energy after assuming a rational soil displacement field. Solutions for the pile deflection are obtained analytically, while those for the soil displacements are obtained using the finite difference method. The input parameters needed for the analysis are the pile geometry, soil profile and the elastic constants of the soil and pile. The method produces results with accuracy comparable to that of a three-dimensional finite element analysis but requires much less computation time. The analysis can take into account the spatial variation of soil properties along vertical, radial and tangential directions.
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Xie, Xin Ying, and Xin Sheng Yin. "The Finite Element Analysis of Plate's Distance on Push-Extend Multi-under-Reamed Pile." Advanced Materials Research 468-471 (February 2012): 2517–20. http://dx.doi.org/10.4028/www.scientific.net/amr.468-471.2517.
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In this paper ,it analyses the push-extend multi-under-reamed pile in use of elastic-plastic theory by the software ANSYS.It takes four push-extend multi-under-reamed piles which are the same except plates' distance.It introduces the realative theory to make the anlysis much more accuracy.The results which is taken by ANSYS are researched to find out the regularity and can certain the reasonable plate's distance to anlyze the bearing capacity of push-extend multi-under-reamed pile at the same time.
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KANG, MA, SUBHADEEP BANERJEE, FOOK-HOU LEE, and HE PING XIE. "DYNAMIC SOIL-PILE-RAFT INTERACTION IN NORMALLY CONSOLIDATED SOFT CLAY DURING EARTHQUAKES." Journal of Earthquake and Tsunami 06, no. 03 (September 2012): 1250031. http://dx.doi.org/10.1142/s1793431112500315.
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This paper examines the seismic response of clay pile-raft system with flexible and stiff piles using centrifuge and numerical studies. Centrifuge studies showed that interaction between pile-raft and clay will cause a significant softening in the clay adjacent to the pile-raft which produced a lengthening of resonance period in near-field soil compared to the far-field soil. The difference of response among the raft and the soil at both near- and far-field indicates that ground motion at both near- and far-field cannot be representative of raft motion. There is also significant difference between flexible and stiff pile response. It has been shown in a previous study that, for stiff pile, the soft clay acts as an inertial loading medium rather than a supporting medium. For this reasons, the bending moment diagram extends deep into the soft soil stratum. However, for flexible pile, the supporting effect of the surrounding clay is much more significant than in stiff pile. As a result, the bending moment envelope for flexible pile under earthquake shaking is very similar to the head-loaded test results, with an active length of pile below which no significant bending moment occurs.
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Maheshwari, Bal Krishna, Kevin Z. Truman, M. Hesham El Naggar, and Phillip L. Gould. "Three-dimensional finite element nonlinear dynamic analysis of pile groups for lateral transient and seismic excitations." Canadian Geotechnical Journal 41, no. 1 (February 1, 2004): 118–33. http://dx.doi.org/10.1139/t03-073.
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The effects of material nonlinearity of soil and separation at the soilpile interface on the dynamic behaviour of a single pile and pile groups are investigated. An advanced plasticity-based soil model, hierarchical single surface (HiSS), is incorporated in the finite element formulation. To simulate radiation effects, proper boundary conditions are used. The model and algorithm are verified with analytical results that are available for elastic and elastoplastic soil models. Analyses are performed for seismic excitation and for the load applied on the pile cap. For seismic analysis, both harmonic and transient excitations are considered. For loading on the pile cap, dynamic stiffness of the soilpile system is derived and the effect of nonlinearity is investigated. The effects of spacing between piles are investigated, and it was found that the effect of soil nonlinearity on the seismic response is very much dependent on the frequency of excitation. For the loading on a pile cap, the nonlinearity increases the response for most of the frequencies of excitation while decreasing the dynamic stiffness of the soilpile system.Key words: pile groups, plasticity, separation, dynamic stiffness, seismic response.
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Zhang, Yun, and Patrick Michel. "Tidal distortion and disruption of rubble-pile bodies revisited." Astronomy & Astrophysics 640 (August 2020): A102. http://dx.doi.org/10.1051/0004-6361/202037856.
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Context. In the course of a close approach to planets or stars, the morphological and dynamical properties of rubble-pile small bodies can be dramatically modified, and some may catastrophically break up, as in the case of comet Shoemaker-Levy 9. This phenomenon is of particular interest for the understanding of the evolution and population of small bodies, and for making predictions regarding the outcomes of future encounters. Previous numerical explorations have typically used methods that do not adequately represent the nature of rubble piles. The encounter outcomes and influence factors are still poorly constrained. Aims. Based on recent advances in modeling rubble-pile physics, we aim to provide a better understanding of the tidal encounter processes of rubble piles through soft-sphere discrete element modeling (SSDEM) and to establish a database of encounter outcomes and their dependencies on encounter conditions and rubble-pile properties. Methods. We performed thousands of numerical simulations using the SSDEM implemented in the N-body code pkdgrav to study the dynamical evolution of rubble piles during close encounters with the Earth. The effects of encounter conditions, material strength, arrangement, and resolution of constituent particles are explored. Results. Three typical tidal encounter outcomes are classified, namely: deformation, mass shedding, and disruption, ranging from mild modifications to severe damages of the progenitor. The outcome is highly dependent on the encounter conditions and on the structure and strength of the involved rubble pile. The encounter speed and distance required for causing disruption events are much smaller than those predicted by previous studies, indicating a smaller creation rate of tidally disrupted small body populations. Extremely elongated fragments with axis ratios ~1:6 can be formed by moderate tidal encounters. Our analyses of the spin-shape evolution of the largest remnants reveal reshaping mechanisms of rubble piles in response to tidal forces, which is consistent with stable rubble-pile configurations derived by continuum theory. A case study for Shoemaker-Levy 9 suggests a low bulk density (0.2–0.3 g cc−1) for its progenitor.
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Rui, Yi, Nicholas de Battista, Cedric Kechavarzi, Xiaomin Xu, and Mei Yin. "Distributed fiber optic monitoring of a CFA pile with a central reinforcement bar bundle." Frontiers of Structural and Civil Engineering 15, no. 1 (February 2021): 167–76. http://dx.doi.org/10.1007/s11709-020-0581-z.
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AbstractIn this paper, we present an application of distributed fiber optic sensor (DFOS) technology to measure the strain of a continuous flight auger (CFA) test pile with a central reinforcement bar bundle, during a static load test carried out in London. Being distributed in nature, DFOS gives much more information about the pile performance as compared to traditional point sensors, such as identifying cross-sectional irregularities or other anomalies. The strain profiles recorded along the depth of the piles from the DFOS were used to calculate pile deformation (contraction), shaft friction, and tip resistance under various loads. Based on this pile load test, a finite element (FE) analysis was performed using a one-dimensional nonlinear load-transfer model. Calibrated by the shaft friction and tip resistance derived from the monitored data, the FE model was able to simulate the pile and soil performance during the load testing with good accuracy. The effect of the reinforcement cage and central reinforcement bar bundle were investigated, and it was found that the addition of a reinforcement cage would reduce the pile settlement by up to 20%.
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Rui, Yi, and Mei Yin. "Investigations of pile–soil interaction under thermo-mechanical loading." Canadian Geotechnical Journal 55, no. 7 (July 2018): 1016–28. http://dx.doi.org/10.1139/cgj-2017-0091.
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Thermo-active piles that couple load bearing with ground source heat pump systems are one of the new technologies in geotechnical engineering. This paper investigates the pile–soil interaction behaviour of a thermo-active pile in overconsolidated London clay by conducting a thermo-hydro-mechanical finite element analysis using an advanced soil constitutive model. Negative and positive excess pore pressures are computed around the pile during cooling and heating, respectively. However, the difference in the radial effective stress acting on the pile–soil interface between the cooling and heating stages is small, and the pile–soil interaction is governed by the shear mobilization associated with thermally induced cyclic movements of pile expansion and contraction. During the first cooling stage, the shear stress at a small portion in the upper part of the pile reaches close to the yield values, which leads to an additional settlement about 3 mm from the original mechanical load–induced settlement of 2 mm. The shear stresses in subsequent heating and cooling cycles are much smaller than the ultimate shear stress values, because of the heavily overconsolidated nature of the London clay.
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Swanson, J., S. Morrison, O. Barrera, and S. Hill. "Piliation changes in transformation-defective gonococci." Journal of Experimental Medicine 171, no. 6 (June 1, 1990): 2131–39. http://dx.doi.org/10.1084/jem.171.6.2131.
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Recombination-dependent alterations of their expressed pilin gene (pilE) enable gonococci to synthesize a myriad of structurally/antigenically different pili and to reversibly switch their pilus production on and off. These changes have been ascribed both to DNA transformation and to intragenomic recombination between pilE and silent pilin genes (pilS). We examined the pilus changes in gonococci that are incompetent for transformation because of their DNA uptake deficiency (dud) mutation, pilus- (P-) phenotype, or both. Though incompetent for DNA transformation, dud cells displayed pilus antigenic variation and underwent reversible pilus variations much like their wild-type parent. Wild-type P- with a pilE nonsense mutation were also virtually nontransformable, but they reverted to P+ at high frequencies. The pilin mRNA sequence changes that accompanied pilus transitions in these nontransformable dud and P- gonococci represent insertion of pilS stretches into their respective pilE, apparently via intragenomic recombination.
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Goel, Rakesh K. "Evaluation of In-Ground Plastic-Hinge Length and Depth for Piles in Marine Oil Terminals." Earthquake Spectra 31, no. 4 (November 2015): 2397–417. http://dx.doi.org/10.1193/071813eqs207m.
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This investigation evaluated the current recommendations for plastic-hinge length and depth for piles in marine oil terminals considering nonlinear pile and soil behavior, as well as two seismic design levels: Level 1 and Level 2. It was found that the plastic-hinge length depends on seismic design level, whereas depth is independent of seismic design level. For pre-stressed concrete piles, the current plastic-hinge length recommendations were generally found to be adequate for seismic design Level 2, but provided much smaller plastic-hinge length for Level 1. For hollow-steel piles, the current plastic-hinge length recommendation was generally found to be adequate for sands, but provided much smaller plastic-hinge length for clays for both seismic design levels. Furthermore, the current recommendations lead to much shallower plastic-hinge depth than that found in this investigation.