Seismic Earth Pressure Exerted on Retaining Walls Under a Large Seismic Load

In recent years, serious damage has been done to retaining structures because of large earthquakes. In order to establish practical methods for evaluating the seismic earth pressure, which is one of the important external forces acting on retaining structures during large earthquakes, a series of shaking table tests was conducted on retaining wall (RW) models. The experiments revealed that the seismic active earth pressure was considerably smaller than that obtained by the Mononobe-Okabe theory, particularly under a large seismic load. Furthermore, it was demonstrated that the seismic earth pressure had an upper limit, which was determined by the force equilibrium of the soil wedge at the critical state when the RW lost its stability. On the basis of the test results, a new method to evaluate the seismic earth pressure for practical designs under a large seismic load has been suggested. This proposed method provides a reasonable earth pressure as well as an angle of failure plane, those of which depend on the seismic stability of the retaining wall. It has been confirmed that earth pressure obtained by the proposed method agrees well with the measured seismic earth pressure exerted on several retaining walls with different degrees of stability.     

一种考虑主应力偏转的平移挡墙地震土压力算法

遵循 Mononobe-Okabe理论,考虑墙后破裂体内的主应力偏转,并假设小主应力偏转迹线形状为圆形下段部分的一段,通过转动挡土墙的解析模型,再结合库伦土压力的相关概念得到地震主动破裂角。采用微分薄层法,对墙后滑裂微元体进行应力解析,推导得到平移模式(T模式)下的地震主动土压力的计算公式,并分析了土中各参数以及地震动系数对地震土压力的影响情况。本文旨在改进地震土压力算法,不仅在计算中考虑了主应力的偏转,而且大大简化了地震土压力的计算过程。最后将计算值与前人方法及试验数据进行对比,结果显示本文算法得到的地震主动土压力分布与模型试验数据更为吻合。     

支护结构施工动态参数反演及变形预测

基于Powell寻优反演分析的方法,利用施工过程中上一施工工况的变形监测值反演下一工况的土体m值、支护结构刚度及支撑刚度,进而对施工过程中支护结构变形量的准确预报,实现对整个施工过程的动态优化设计。通过具体工程实例中结构变形量实测值与预测值的对比分析,验证反分析方法在支护结构设计和施工过程中的合理可行性且具有较高的精确度。     

挡土墙地震主动土压力的解析解

地震主动土压力公式用微分薄层法来推出,填土料为黏土,挡土墙竖直,填土面水平,填土和墙背有粘聚力c和内摩擦角φ作用,墙后破坏体存在竖直和水平两个方向的加速度,目前所见的地震和非地震的主动土压力都是这个公式的特例。对以上条件下的挡土墙用过墙踵的破坏体作静力平衡分析(如朗肯分析),获得的总土压力与文中微分薄层法获得的总土压力一样,但微分法作用点位置显著增高。因此在设计抗震和非抗震挡土墙时要特别注意。     

上填下挖高挡墙的新型处理方法

实际工程中常遇到上填下挖的高挡墙,此种高挡墙由于各种因素限制,按传统的全挖或全填的支挡方式处理均不合理且不经济。结合一工程实例采用排桩支护与加筋土挡墙结合的复合式挡土墙很好地解决了上填下挖高挡墙的问题。此种支护方式将传统的挖方区支护结构与填方区支护结构结合起来,不仅施工方便,而且工程造价较传统支护方式偏低。此外由于仅是把传统的两种支护方式结合,实际工程中计算和施工不存在新的困难。     

刚性挡土墙土压力与位移关系试验研究

通过室内模型试验,实测了挡墙绕墙底转动模式下土压力的相关数据,绘制出土压力沿墙高的分布曲线,研究挡土墙位移对土压力的影响,并比较分析了土压力与位移之间的关系。     

加筋土挡墙的抗震性能研究现状

首先,简述了加筋土挡墙比天然地基及普通挡土墙具有更好的抗震性能,对加筋土挡墙抗震性能的主要影响因素进行了综述,包括:筋材长度和筋材层间距、回填土性质、地震系数等。同时也指出,加筋土挡墙在地震烈度较大时也会发生破坏。最后,根据对加筋土挡墙抗震性能研究的结果指出,可以通过进一步的研究来定量评价加筋土挡墙的抗震能力,同时了解地震过程中的筋土耦合问题,综合考虑水平地震加速度(ah)和竖向地震加速度(av)对加筋土抗震性能的影响。     

非均匀地震作用下隧道位移反应分析

根据多点地震动合成方法,考虑地震波的随机性和行波效应,生成非均匀多点地震动加速度时程曲线,在此基础上,运用FLAC3D分析隧道在非均匀性地震荷载作用下的响应特征及其影响因素。引入非均匀影响系数η和最大最小位移比Φ描述地震作用下隧道位移反应规律。分析结果表明,隧道的位移反应和地震的空间非均匀性对隧道位移的影响随埋深、侧压系数增加而减小;随地震动振幅的增加而增加;随地震动卓越频率的增加而减小;随地震动持时的增加而增加。非均匀影响系数η和最大最小位移比Φ表现出和位移相同的变化趋势。     

Response and Modeling of Cantilever Retaining Walls Subjected to Seismic Motions

Abstract:   A series of nonlinear, explicit finite difference analyses were performed to determine the dynamic response of a cantilever retaining wall subjected to earthquake motions. This article outlines the calibration and validation of the numerical model used in the analyses and comparisons are presented between the results from the finite difference analyses and results from simplified techniques for computing dynamic earth pressures and permanent wall displacement (i.e., Mononobe-Okabe and Newmark sliding block methods). It was found that at very low levels of acceleration, the induced pressures were in general agreement with those predicted by the Mononobe-Okabe method. However, as the accelerations increased to those expected in regions of moderate seismicity, the induced pressures are larger than those predicted by the Mononobe-Okabe method. This deviation is attributed to the flexibility of the retaining wall system and to the observation that the driving soil wedge does not respond monolithically, but rather responds as several wedges. Additionally, it was found that the critical load case for the structural design of the wall differed from that for the global stability of the wall, contrary to the common assumption made in practice that the two load cases are the same .     

挡土墙土压力非线性分布的计算方法研究

基于数学方法对斜单元体进行力和力矩的平衡分析, 得到了墙背粗糙且填土坡面倾斜情况下的土压力解析解, 并进一步分析了填土坡面倾角对土压力的影响。对比分析表明: 经典朗肯土压力理论可看作是解析解在墙背光滑、填土坡面水平情况下的特例; 在填土内摩擦角一定时, 挡土墙墙后滑动楔体的极限破裂角随着填土坡面倾角或墙土之间摩擦角的增大而减小。基于解析解得到的土压力分布呈现明显的非线性特征, 且在填土面水平情况下挡土墙墙脚处的土压力为0, 这与实测数据取得了很好的一致。分析还表明, 随着填土坡面倾角的增大, 墙脚处的土压     

Simplified Procedure to Evaluate Earthquake-Induced Residual Displacement of Geosynthetic Reinforced Soil Retaining Walls

Based on a series of shaking table model tests, it was found that the effects of 1) subsoil and backfill deformation, 2) failure plane formation in backfill, and 3) pullout resistance mobilized by the reinforcements on the seismic behaviors of the geosynthetic reinforced soil retaining walls (GRS walls) were significant. These effects cannot be taken into account in the conventional pseudo-static based limit equilibrium analyses or Newmark's rigid sliding block analogy, which are usually adopted as the seismic design procedure. Therefore, this study attempts to develop a simplified procedure to evaluate earthquake-induced residual displacement of GRS walls by reflecting the knowledge on the seismic behaviors of GRS walls obtained from the shaking table model tests. In the proposed method, 1) the deformation characteristics of subsoil and backfill are modeled based on the model test results and 2) the effect of failure plane formation is considered by using residual soil strength after the failure plane formation while the peak soil strength is used before the failure plane formation, and 3) the effect of the pullout resistance mobilized by the reinforcement is also introduced by evaluating the pullout resistance based on the results from the pullout tests of the reinforcements. By using the proposed method, simulations were performed on the shaking table model test results conducted under a wide variety of testing conditions and good agreements between the calculated and measured displacements were observed.     

钢骨联肢剪力墙抗震性能试验研究

为进一步研究钢骨混凝土剪力墙在不同轴压比下的各项抗震性能,明确其受力机能、破坏状态、耗能机理,为工程设计人员提供合理有效的设计参数,为将来进一步的研究提供基础,本研究以三个联肢钢骨剪力墙试件的伪静力抗震试验为基础,从强度、变形和能量等三个方面判别和鉴定各试件的抗震性能。同时利用多种方法计算试件的承载力,计算结果表明,利用现有规范计算钢骨剪力墙抗剪承载力是精确可靠的。     

动参数对三维洞室动态特性的影响分析

尝试用FLAC有限差分软件对横震动荷载下三维洞室的一些动态影响因素(幅值、频率、持续时间等)进行了模拟,并进行了三维动力特性分析,初步了解不同影响因素地震动荷载下的洞室动态特性规律。同时初步分析结果表明,在横震荷载作用下,洞室位移随振幅、持续时间的增加而增大,洞室位移随频率的增加先增加后减小。分析有助于我们增加对动荷载下地下洞室围岩的变形和破坏机制的认识。     

土钉墙桩排组合支护基坑土压力和变形分析

土钉墙和桩排组合支护是基坑工程中一种新的挡土形式,其上部的土钉墙和下部的桩排协同作用,使得它受到的土压力和发生的变形既不同于土钉墙,也不同于桩排支护。针对这种组合支护一基坑实例,用三维数值模拟实验方法,探讨了空间受力与变形的特征。分析结果表明,这种组合支护: (1)实际受到的土压力与由郎肯理论确定的土压力不相同,文中给出了修正系数。与单纯的桩排支护相比,它的被动土压力增加约20%,而土钉墙面层最大土压力则减少了近50%; (2)发生的最大变形与本文提出的组合支护无量纲整体刚度系数相关。相同地质条件下,当整体刚度系数从4 000增加到5 000时,组合支护变形有明显减少的趋势。     

单边加载下的深基坑水平位移分析

为分析和预判桩锚支护下的深基坑在单边加载状态下的顶部水平位移情况,采用有限差分法对基坑三维受力和变形状态进行模拟.结合某高层住宅施工过程中的深基坑监测项目进行实例验证,将模拟分析结果与实际监测成果进行对比.通过对比证明,在参数设置准确的情况下,有限差分模拟计算能较好地预测基坑边变形趋势,为安全监测项目方案的制定、指导施...     

Simplified Method for Calculating Active Earth Pressure Against Rigid Retaining Walls for Cohesive Backfill

Soil Mechanics and Foundation Engineering - The horizontal slice element method for calculating active earth pressure against rigid retaining walls has been extended to the cohesive backfill. The...     

基于位移延性的剪力墙抗震设计

本文介绍了不同轴压比的剪力墙在往复水平荷载作用下的试验结果,研究了轴压比对剪力培受力性能的影响;建立了剪力场考虑约束边缘构件的位移延性比的计算方法;通过理论计算,研究了轴压比、高宽比、约束边缘构件的长度及其含特征值对位移延性的影响;提出了基于位移延性的剪力场抗震设计建议以及确定约束边缘构件长度及其配箍的计算方法。     

地震力作用角度对短肢剪力墙抗震性能的影响

通过低周反复试验研究了加载角度对"一"字形截面钢筋混凝土短肢剪力墙抗震性能的影响,加载角度为0°,25°,45°。记录了试件由开裂、屈服到破坏的整个过程,观察到不同角度加载造成的剪力墙不同的破坏模式,可以发现,短肢墙的破坏形式由弯剪破坏到弯曲破坏变化。定量分析试件的恢复力曲线(即滞回曲线和骨架曲线)、延性、耗能能力等指标发现,随着加载角度的增大,构件的极限承载力变小,极限位移、延性、耗能能力增大。     

利用支护桩水平监测位移确定桩身弯矩的方法

利用现场监测资料确定支护桩的截面弯矩对判断桩的安全状态和完善深基坑设计方法具有重要价值,但目前的确定方法不仅监测过程复杂,而且间接换算出的弯矩也可能与实际相差较大。本文将支护桩的水平监测位移看作三次样条函数,建立了一个确定桩身截面弯矩的计算方法。将该方法应用于某实际工程的结果表明,它不仅能够较为准确地确定支护桩的最大截面弯矩,而且也可以较好地反映整个桩身的弯矩分布。     

嵌岩护坡桩设计计算方法探讨

目前对于嵌岩灌注桩受水平荷载的受力分析及设计计算方法研究的还比较少。本文根据嵌岩护坡桩入岩段深度,分三种情况讨论其破坏情形和设计计算方法,同时探讨了桩距、桩径对土桩力的影响和防止桩沿不连续体破坏的两种形式的计算方法。