砂性土边坡稳定性离心模型试验研究

借助于西南交通大学TLJ-2型离心机,具体研究了不同含水率下三组砂性土边坡模型的稳定及破坏情况,并分析了砂性土边坡的破坏机理和破坏特征。试验结果表明:含水量是影响砂性土边坡稳定的重要因素。从边坡模型破坏后情况分析,对于有着多级平台的砂性土边坡,滑面较浅,沿各级平台后缘拉裂而坍塌,其破坏类型属于牵引式滑动。     

水平多向荷载下桩-土相互作用初探

利用香港科技大学离心机双向振动台,进行了群桩基础模型的水平单向和双向振动试验;振动过程中的桩身弯矩响应表明,群桩基础在单向振动中表现出的对称性在双向振动下不复存在;并进行了桩-土相互作用的颗粒流数值模拟,初步探寻了试验观测到的“垂向加载效应”的产生机制;同时通过简单的推导,指出了当前桩-土相互作用分析方法的局限性。在试验、数值和理论分析方面对水平多向荷载下的桩-土相互作用进行了初步研究,为今后的进一步研究提供了重要参考。     

Numerical modeling of centrifuge cyclic lateral pile load experiments

To gain insight into the inelastic behavior of piles, the response of a vertical pile embedded in dry sand and subjected to cyclic lateral loading was studied experimentally in centrifuge tests conducted in Laboratoire Central des Ponts et Chaussées. Three types of cyclic loading were applied, two asymmetric and one symmetric with respect to the unloaded pile. An approximately square-root variation of soil stiffness with depth was obtained from indirect in-flight density measurements, laboratory tests on re...     

非饱和土渗流与变形耦合问题的有限元分析

基于多孔介质力学原理,建立能模拟非饱和土两相流动与变形耦合问题的理论模型。利用Galerkin法对控制方程进行离散,得到控制方程的有限元计算格式。在此基础上,自主开发了有限元计算程序U-DYSAC2,并对Liakopoulos两相流动试验这一经典算例以及重非亲水相流体（DNAPL）在饱和多孔介质中迁移的离心模型试验进行了数值模拟。计算结果表明,理论预测与试验结果基本吻合,验证了所提出的分析方法在模拟非饱和土渗流以及变形问题时的有效性,从而为定量研究饱和-非饱和渗流以及变形问题提供了一条有效途径。     

群桩扭转非线性模型

建立了一个非线性数学模型来分析群桩扭转问题。该模型利用非线性荷载传递曲线来模拟桩的非线性响应,采用Mindlin解计算各桩水平力间的相互作用,用Randolph解析解分析得到各桩间扭矩对水平力的影响。在各单桩中引入经验性的耦合系数,分析桩身水平变形引起的土体反力对该桩扭转承载力的影响。对比计算结果与离心机模型试验数据,表明该模型能够模拟群桩扭转中主要的桩-土-桩相互作用和荷载耦合作用,较好地反映了实际情况。     

地震作用下自由场中饱和砂土的应力-应变推导

水平自由场地震响应分析是岩土地震工程实践的重要内容之一。利用香港科技大学土工离心机上的双向振动台,进行了饱和砂土自由场在水平双向地震作用下的动力模型试验。根据应力和应变的定义以及达朗贝尔原理,由试验观测的土体加速度、位移和孔隙水压力数据直接推导得到不同深度处砂土的应力和应变,揭示了振动过程中饱和砂土的应力路径和应力-应变关系演化过程,以及与超静孔隙水压力发展的联系。     

黄土边坡开挖与支护效应的离心模拟试验研究

黄土边坡在开挖卸载过程中的稳定性分析及其防护在边坡工程中占有重要地位。采用西南交通大学土工离心机进行了1组非支护边坡和2组土钉支护边坡的离心模型试验,研究了开挖卸载过程中黄土边坡的变形特性、稳定性变化规律及土钉的加固效应。离心模型试验研究表明,土钉能够显著提高黄土边坡的稳定性。土钉支护的边坡土体,因土钉的锚固效应,边坡的变形范围更大,但变形量较小,最大变形量并不在坡面,而是发生在坡面下的锚固区域内,非支护黄土边坡的潜在滑移面产生于距坡顶约40 cm处,土钉支护后,黄土边坡基本不会发生破坏。对于抵抗边坡发生变形而言,不等长土钉支护的效果要优于等长土钉支护,研究成果为黄土边坡的开挖与防护提供了参考。     

Influence of model type,bias and input parameter variability on reliability analysis for simple limit states in soil–structure interaction problems

ABSTRACT

A general closed-form solution for the true probability of failure of a simple limit state function with one load term and one resistance term is derived. The formulation considers contributions due to model type, uncertainty in method bias values, bias dependencies, uncertainty in estimates of nominal values for correlated and uncorrelated load and resistance terms, and average margin of safety expressed as the operational factor of safety. Example calculations are presented using different load and resistance models for the pullout internal stability limit state of steel strip reinforced soil walls together with matching bias data reported in the literature.     

Characterising soil property in an area with limited measurement: a Bayesian approach

The Bayesian approach has been proved useful to geotechnical engineering especially when project-specific data/measurements are very limited. In this paper, we introduced a new Bayesian algorithm to estimate soil properties at each location of a study area, with very limited project-specific data. In addition to the proposed methodology and algorithms, we also conducted a model application to estimate soil permeability for each of the 64 locations within a 4-by-4 m² area, based on very limited project-specific data, that is, one measurement from each location.