共查询到20条相似文献，搜索用时 23 毫秒
1.
Viscous fluid characteristics of liquefied soils and behavior of piles subjected to flow of liquefied soils 总被引：5，自引：0，他引：5
Jae-Ik Hwang Chang-Yeop Kim Choong-Ki Chung Myoung-Mo Kim 《Soil Dynamics and Earthquake Engineering》2006,26(2-4):313-323
Lateral movement of sloping ground due to flow liquefaction has caused many pile foundations to fail, especially those in ports and harbor structures. Several researchers have found and verified that the behavior of liquefied soils can be simulated appropriately by modeling the liquefied soils as viscous fluid. In this study, the influence of the lateral movement of liquefied sloping ground on the behavior of piles was analyzed on the assumption that the flow of liquefied soils can be treated as viscous fluid flow. Sinking ball tests and pulling bar tests were performed to measure the viscosity of liquefied Jumoonjin sand. Then, the behavior of a single pile installed in liquefiable infinite slopes consisting of sand was investigated by numerical analyses. The liquefied sand behaved as non-Newtonian fluid, whose viscosity decreased with increasing shear strain rate. Furthermore, the flow of liquefied soils had a crucial effect on the stability of piles installed in the sloping ground. 相似文献
2.
The present study aims to obtain p-y curves(Winkler spring properties for lateral pile-soil interaction) for liquefied soil from 12 comprehensive centrifuge test cases where pile groups were embedded in liquefiable soil. The p-y curve for fully liquefied soil is back-calculated from the dynamic centrifuge test data using a numerical procedure from the recorded soil response and strain records from the instrumented pile. The p-y curves were obtained for two ground conditions:(a) lateral spreading of liquefied soil, and(b) liquefied soil in level ground. These ground conditions are simulated in the model by having collapsing and non-collapsing intermittent boundaries, which are modelled as quay walls. The p-y curves back-calculated from the centrifuge tests are compared with representative reduced API p-y curves for liquefied soils(known as p-multiplier). The response of p-y curves at full liquefaction is presented and critical observations of lateral pile-soil interaction are discussed. Based on the results of these model tests, guidance for the construction of p-y curves for use in engineering practice is also provided. 相似文献
3.
MA Xingyu WANG Lanmin WANG Qian WANG Ping ZHONG Xiumei PU Xiaowu LIU Fuqiang XU Xiaowei 《中国地震研究》2020,34(4):469-481
Based on the dynamic triaxial liquefaction test of the loess samples which are taken from Shibei tableland, Guyuan City, Ningxia, China, the characteristics of dynamic strain, dynamic stress and pore water pressure are studied under cyclic loading. Triaxial shear test is conducted immediately after the sample reaches liquefaction point. During the test, the property of the liquefied soil is analyzed through fluid mechanics method, whereby the fluidity of the liquefied soil is represented by apparent viscosity.The results show that the fluidity of liquefied loess changes from "shear thickening" to "shear thinning" as the shear force continues, and the fluidity of liquefied loess is closely related to its structure. In addition, in the process of forming a new stable state, the apparent viscosity and deviant stress change with axial strain in a similar approach. When the sample reaches its stable state, it meanwhile shows a relatively stable apparent viscosity. According to the fluid mechanics and the law of conservation of energy, the slip distance of the liquefied soil is estimated, and the results are in good agreement with the field investigation results. 相似文献
4.
Chen Guoxing Zhou Enquan Wang Zhihua Wang Binghui Li Xiaojun 《Bulletin of Earthquake Engineering》2016,14(8):2185-2212
Liquefaction of saturated loose sand is a major cause of extensive damage to buildings and infrastructures during large earthquakes. A better understanding of the behaviour of liquefied soil is becoming increasingly necessary to mitigate earthquake damage, and the fluid method has become an increasingly popular means to study the behaviour of liquefied soils. The purpose of this study is to determine the fluid characteristics of liquefied fine sand. In this paper, the apparent viscosity was measured as an index of fluid characteristics using the shaking table tests of pre-liquefaction behaviour of saturated fine sand at approximately 45 % relative density; the relationship of apparent viscosity and shear strain rate on liquefying fine sand was indicated as a power-law shear-thinning non-Newtonian fluid; and liquefying fine sand has the alternating behaviour of shear dilatancy and compressibility during cyclic loading. Additionally, a series of a monotonic axial compression loading tests in an undrained manner were performed to measure the shear stress and excess pore pressure ratio relationship on the post-liquefaction saturated fine sand at approximately 50 % relative density. The fluid characteristics of post-liquefaction fine sand exhibits rate dependence and can be described by a combined fluid model of time-independent and time-dependent power-law functions; the time-independent viscous resistance is not relevant to the excess pore pressure ratio; but the time-dependent frictional resistance is closely related to the excess pore pressure ratio. Furthermore, the results of the verification tests demonstrate that the proposed fluid model has good applicability for the fluid behaviour of the post-liquefaction fine sand. 相似文献
5.
Compaction or densification of loose saturated soils has been the most popular method of reducing earthquake related liquefaction potential. Such compaction of a foundation soil is only economical when limited in extent, leading to a case of an ‘island’ of improved ground (surrounded by unimproved ground). The behavior of the densified sand surrounded by liquefied loose sand during and following earthquakes is of great importance in order to design the compacted area rationally and optimize both safety and economy. This problem is studied herein by means of dynamic centrifuge model tests. The results of three heavily-instrumented dynamic centrifuge tests on saturated models of side-by-side loose and dense sand profiles are discussed. The test results suggest the following concerns as relates to ‘islands’ of densified soil: (1) there is a potential strength degradation in the densified zone as a result of pore pressure increase due to migration of pore fluid into the island from the adjacent loose liquefied ground; (2) there is a potential for lateral deformation (sliding) within the densified island as the surrounding loose soil liquefies. 相似文献
6.
Cyclic shearing and liquefaction of soil under irregular loading: an incremental model for the dynamic earthquake-induced deformation 总被引：1，自引：0，他引：1
V. A. Osinov 《Soil Dynamics and Earthquake Engineering》2003,23(7):535-548
The paper presents a mathematical model for the deformation of soil under irregular cyclic loading in the simple-shear conditions. The model includes the possible change in the effective pressure in saturated soil due to the cyclic shearing, the reciprocal influence of the effective pressure on the response of the soil to the shear loading, and the pore pressure dissipation due to the seepage of the pore fluid. The hysteresis curves for the strain–stress relationship are constructed in such a way that they produce both the required backbone curve and the required damping ratio as functions of the strain amplitude. At the same time, the approach enables the constitutive functions involved in the model to be specified in various ways depending on the soil under study. The constitutive functions can be calibrated independently of each other from the conventional cyclic shear tests. The constitutive model is incorporated in the boundary value problem for the dynamic site response analysis of level ground. A numerical solution is presented for the dynamic deformation and liquefaction of soil at the Port Island site during the 1995 Hyogoken-Nambu earthquake. 相似文献
7.
采用多工况振动台实验研究液化对土层水平往返变形的影响.以干砂实验为参照,分析孔压增长与土层加速度和土层往返变形之间的关系.结果表明:液化将引起土表加速度显著降低,减小惯性力传递,但同时会引起土层往返剪应变明显增大.对往返变形而言,液化土层往返剪应变就可达到1%～5%的大变形状态,且液化土层往返剪应变沿深度呈下大上小分布.土层中孔压比0.4～0.8是往返变形出现放大的敏感段,在孔压比0.8左右而不是在1.0达到最大.作为其结果,土层液化将对刚性上部结构振动起减震作用,但同时增大的往返剪应变也易导致基础和地下结构破坏,特别是对液化层与下部非液化层交界处的构件更敏感. 相似文献
8.
J.R. Dungca J. Kuwano A. Takahashi T. Saruwatari J. Izawa H. Suzuki K. Tokimatsu 《Soil Dynamics and Earthquake Engineering》2006,26(2-4):287-295
This paper presents an experimental study on the lateral resistance of a pile subjected to liquefaction-induced lateral flow. To observe the soil surrounding the pile during liquefaction, it was modeled as a buried cylinder that corresponded to a sectional model of the prototype pile at a certain depth in the subsoil. In order to create a realistic stress condition in the model ground, the model was prepared in a sealed container and the overburden pressure was applied to the ground surface by a rubber pressure bag. The model pile was actuated back and forth through rods attached on each side by an electro-hydraulic actuator.This paper focuses on observing the deformation of the liquefied soil surrounding the pile when a large relative displacement between the pile and the soil is induced. The loading rate effect on the lateral resistance of the pile in the liquefied sand and the influence of the relative density are also investigated.Test results show that a larger resistance is mobilized as the loading rate becomes higher. When the loading rate is higher, the cylinder displacement required for the lateral resistance becomes smaller. It has been also observed that as the relative density of the soil increases, dilatancy of the soil in front of the pile also increases. 相似文献
9.
Mitsutoshi Yoshimine Hiroto Nishizaki Kei Amano Yasuyo Hosono 《Soil Dynamics and Earthquake Engineering》2006,26(2-4):253-264
This paper intended to evaluate the behavior of saturated sand and sloped ground subjected to flow failure with seepage of pore water in the ground after earthquake and the resultant liquefaction. Triaxial compression tests of sand with constant deviator stress but changing of pore pressure and volume of the specimens were conducted in this study. It was revealed that the relation between the volume change and the amount of shear strain during deformation depended on the initial density of the sand but it did not much depend on shear stress and initial confining stress levels. Based on this test results and numerical analysis of the seepage of pore water in liquefied ground, a methodology was proposed to predict the deformation of inclined ground due to liquefaction. 相似文献
10.
11.
Zhijian Qiu Ahmed Ebeido Abdullah Almutairi Jinchi Lu Ahmed Elgamal P. Benson Shing Geoffrey Martin 《地震工程与结构动力学》2020,49(4):375-393
Considerable bridge-ground interaction effects are involved in evaluating the consequences of liquefaction-induced deformations. Due to seismic excitation, liquefied soil layers may result in substantial accumulated permanent deformation of sloping ground near the abutments. Ultimately, global response is dictated by the bridge-ground interaction as an integral system. However, a holistic assessment of such response generally requires a highly demanding full three-dimensional (3D) model of the bridge and surrounding ground. As such, in order to capture a number of the salient involved mechanisms, this study focuses on the longitudinal seismic performance of a simpler idealized configuration, motivated by details of an existing bridge-ground configuration. In this model, a realistic multilayer soil profile is considered with interbedded liquefiable/nonliquefiable strata. The effect of the resulting liquefaction-induced ground deformation is explored. Attention is given to overall deformation of the bridge structure due to lateral spreading in the vicinity of the abutments. The derived insights indicate a need for such global analysis techniques, when addressing the potential hazard of liquefaction and its consequences. 相似文献
12.
Under seismic excitation, liquefied clean medium to dense cohesionless soils may regain a high level of shear resistance at large shear strain excursions. This pattern of response, known as a form of cyclic mobility, has been documented by a large body of laboratory sample tests and centrifuge experiments. A plasticity-based constitutive model is developed with emphasis on simulating the cyclic mobility response mechanism and associated pattern of shear strain accumulation. This constitutive model is incorporated into a two-phase (solid–fluid), fully coupled finite element code. Calibration of the constitutive model is described, based on a unique set of laboratory triaxial tests (monotonic and cyclic) and dynamic centrifuge experiments. In this experimental series, Nevada sand at a relative density of about 40% is employed. The calibration effort focused on reproducing the salient characteristics of dynamic site response as dictated by the cyclic mobility mechanism. Finally, using the calibrated model, a numerical simulation is conducted to highlight the effect of excitation frequency content on post-liquefaction ground deformations. 相似文献
13.
To understand the post-liquefaction behavior of liquefied ground, it is important to get a better understanding and a more suitable characterization of the variation of excess pore pressure after liquefaction. In this paper, the soil permeability is considered as one of the key soil parameters for clarifying the mechanism of post-liquefaction behavior of liquefied ground. For this reason, a series of shaking table tests were conducted for a Toyoura sand deposit with different soil permeability values. Polymer fluid was used in model tests to vary the permeability of sand deposits. Excess pore pressures and settlements were measured in each test. A basic mechanism in post-liquefaction behavior and the solidification phenomenon after liquefaction were discussed based on these test results. Also, a new method for predicting the dissipation of excess pore pressure was developed. This study provides evidence of the important effect of soil permeability on the velocity with which the solidification front moves upward in liquefied ground. It is suggested that the value of coefficient of permeability of liquefied sand can increase to about 4.0 times the initial value. This variation of permeability after liquefaction should be taken into account in post-liquefaction analysis. 相似文献
14.
Estimation of residual shear strength ratios of liquefied soil deposits from shear wave velocity 总被引：1，自引：1，他引：0
Pelinzener 《地震工程与工程振动(英文版)》2012,11(4):461-484
For sites susceptible to liquefaction induced lateral spreading during a probable earthquake, geotechnical engineers often need to know the undrained residual shear strength of the liquefied soil deposit to estimate lateral spreading displacements, and the forces acting on the piles from the liquefied soils in order to perform post liquefaction stability analyses. The most commonly used methods to estimate the undrained residual shear strength (Sur) of liquefied sand deposits are based on the correlations determined from liquefaction induced flow failures with SPT and CPT data. In this study, 44 lateral spread case histories are analyzed and a new relationship based on only lateral spread case histories is recommended, which estimates the residual shear strength ratio of the liquefiable soil layer from normalized shear wave velocity. The new proposed method is also utilized to estimate the residual lateral displacement of an example bridge problem in an area susceptible to lateral spreading in order to provide insight into how the proposed relationship can be used in geotechnical engineering practice. 相似文献
15.
《Advances in water resources》1998,21(5):351-362
Flow and displacement of non-Newtonian fluids in porous media occurs in many subsurface systems, related to underground natural resource recovery and storage projects, as well as environmental remediation schemes. A thorough understanding of non-Newtonian fluid flow through porous media is of fundamental importance in these engineering applications. Considerable progress has been made in our understanding of single-phase porous flow behavior of non-Newtonian fluids through many quantitative and experimental studies over the past few decades. However, very little research can be found in the literature regarding multi-phase non-Newtonian fluid flow or numerical modeling approaches for such analyses.For non-Newtonian fluid flow through porous media, the governing equations become nonlinear, even under single-phase flow conditions, because effective viscosity for the non-Newtonian fluid is a highly nonlinear function of the shear rate, or the pore velocity. The solution for such problems can in general only be obtained by numerical methods.We have developed a three-dimensional, fully implicit, integral finite difference simulator for single- and multi-phase flow of non-Newtonian fluids in porous/fractured media. The methodology, architecture and numerical scheme of the model are based on a general multi-phase, multi-component fluid and heat flow simulator — TOUGH2. Several rheological models for power-law and Bingham non-Newtonian fluids have been incorporated into the model. In addition, the model predictions on single- and multi-phase flow of the power-law and Bingham fluids have been verified against the analytical solutions available for these problems, and in all the cases the numerical simulations are in good agreement with the analytical solutions. In this presentation, we will discuss the numerical scheme used in the treatment of non-Newtonian properties, and several benchmark problems for model verification.In an effort to demonstrate the three-dimensional modeling capability of the model, a three-dimensional, two-phase flow example is also presented to examine the model results using laboratory and simulation results existing for the three-dimensional problem with Newtonian fluid flow. 相似文献
16.
17.
This paper presents the results of a large-scale shake table test at E-Defense facility on a pile group located adjacent to a gravity-type quay wall and were subjected to liquefaction-induced large ground displacements. Extensive liquefaction-induced large ground lateral spreading displaced the quay wall about 2.2 m and damaged the pile foundation. The pile foundation consisted of a six-pile group which supported a footing and a superstructure model. Large lateral soil displacements were measured by several sensors such as inclinometers and the results favorably agreed with the directly observed deformations. Soil lateral displacement decreased as the distance from the quay wall increased landward. The piles were densely instrumented and the measured bending strain records were able to explain the damage to the piles. Lateral pressures of the liquefied soil exerted on the piles were measured using earth pressure (EP) sensors. The application of two design guidelines (JRA [1] and JSWA [2]) for estimation of liquefaction-induced lateral pressure on piles is discussed and their advantages and shortcomings are addressed. Furthermore, two simplified methods (Shamoto et al. [3] and Valsamis et al. [4]) are employed to predict the extent of liquefaction-induced large ground displacements and they are compared to the measured deformations. Finally, their accuracy for predicting the liquefaction-induced lateral displacements is evaluated and practical recommendations are made. 相似文献
18.
Alexandros I. Valsamis George D. Bouckovalas Achilleas G. Papadimitriou 《Soil Dynamics and Earthquake Engineering》2010
This paper investigates the main parameters affecting the anticipated maximum surface displacements due to earthquake-induced lateral spreading of mildly sloping ground. The main tool used for this purpose is a numerical methodology employing a bounding surface plasticity model implemented in a finite difference code, which has been thoroughly validated against 16 published centrifuge lateral spreading experiments. This study shows that important problem parameters are the mean ground (surface) acceleration, the duration of strong shaking following the onset of liquefaction, the corrected SPT blowcount, the depth to the sliding plane, the inclination of the ground surface and the fines content of the liquefied soil layers. A new approximate multi-variable relation is proposed for the estimation of ground surface displacements due to lateral spreading in gently sloping ground, which includes the foregoing parameters. The form of the relation builds upon sliding block theory, but its final formulation is based on statistical analysis of the input data and the results from 120 parametric analyses performed with the validated numerical methodology. Comparison of the predictions of the proposed relation for ground surface displacement against pertinent field data (from 256 case histories) and centrifuge test measurements shows satisfactory accuracy. Furthermore, the variation of lateral displacements with depth is explored and distinct displacement patterns are proposed for uniform, 2-layer and 4-layer ground profiles. 相似文献
19.
砂土自由场地震响应的离心机试验研究 总被引：3，自引：1，他引：2
离心机模型试验是研究岩土地震工程问题的有效手段。本文使用层状剪切箱,通过干落法制备了均匀的砂土模型,进行了离心机振动试验;观测了振动过程中孔隙水压力的发展,土体的加速度响应、侧向变形以及竖向沉降。结果表明,土体的运动和变形与孔隙水压力的发展密切相关,但离心机中的试验现象和现场观测的现象存在显著区别。研究结果增强了对振动过程中土-水之间相互作用机理的理解,同时为自由场地震响应分析方法的验证提供了基础数据。 相似文献