重力码头地震旋转与滑动耦合运动下的残余位移简易算法

预测重力码头的地震残余位移是码头工程地震设计的关键,而码头墙后回填砂土因地震引起的超静孔隙水压力发展水平对码头墙体运动具有一定的影响。引用液化度概念考虑超静孔隙水压力影响来修正Mononobe-Okabe拟静力法计算的动主动土压力和回填土地震孔隙水产生的动水压力;同时考虑水平和竖向地震载荷,采用Steedman的旋转块体法,根据力与力矩极限平衡确定码头的滑动与旋转门槛加速度系数,分别对码头滑动先开始与倾斜先开始两工况下的耦合运动模式进行详细分析,修正码头因耦合运动影响的滑动与旋转门槛加速度系数,计算码头耦合运动下的地震残余位移计算。选用正弦脉冲的地震运动特征,应用该计算方法对码头耦合运动的残余位移的闭合解进行了推算,分析了码头残余位移随着液化度变化的规律。     

地震作用下可液化土的数值模拟与试验验证

将有限差分法程序用于可液化土的地震响应分析,采用动力和流体的流固耦合理论分析了振动过程中土体孔隙水压力的产生、扩散与消散,并对液化场地桩-土-结构相互作用体系振动台试验进行了三维数值模拟;通过与振动台试验数据的对比分析,验证了计算模型的可靠性和合理性。结果表明：采用的方法能较好地模拟可液化土的动力特性,所得结论为液化场地土-结构相互作用体系动力分析提供了参考。     

高心墙堆石坝地震反应复合模型研究

高土石坝抗震分析得到国内外学者的极大关注。采用土工离心机振动台模型试验和动力数值模拟技术相结合的复合模型方法 来 研究高心墙堆石坝地震反应特性。 首先对不等比尺的离心模型试验结果进行数值模拟,以验证数值计算模型和确定计算参数,然后用数值方法对离心模型试验结果进行拓展和外延,推广到等比尺和原型情况。对比分析了 高心墙堆石坝地震加速度放大系数、地震残余变形、防渗墙动应力和破坏模式。计算值与试验值变化规律一致, 表明复合 模型是研究高心墙堆石坝地震反应特性一种行之有效的方法,（ 40 ～ 50 ） g 离心机振动台模型试验基本上可以反映高土石坝的地震反应特性。     

钢框架结构整体抗震性能试验研究

拟动力试验方法最早是由日本学者于1971年提出的,它综合了拟静力试验、振动台试验和时程反应数值分析的特点,以实际模拟结构的非线性行为.文中通过对一刚性连接钢框架l/3比例模型的拟动力试验和地震反应分析,研究此类结构在地震作用下的整体动力响应;另外根据实测结果建立了一个预测钢框架结构在地震作用下弹塑性性能的理论分析模型,理论计算和试验结果基本吻合;试验结果和计算分析均表明钢框架结构具有良好的抗震性能.     

液化场地桩-土-桥梁结构动力相互作用振动台试验模型相似设计方法

当今，模拟振动台试验是研究工程抗震能力与破坏机理的重要手段之一。模型相似设计是确保振动台试验能够尽可能真实地反映原型动力性状的关键之一。基于目前广泛应用的Bockingham π定理，主要采用量纲分析方法，并且结合考虑模型与原型之间的材料变形应力-应变本构关系及桩-土接触边界动力响应相似性，求解液化场地桩-土-桥梁结构动力相互作用振动台试验的模型设计相似关系，同时提出人工质量问题的解决办法。     

大型沉箱式码头岸壁地震反应分析

在１９９５年１月１７日本阪神大地震中，大量沉箱式码头岸壁遭到严重破坏。为了探讨地震时岸壁的破坏机理，进行了非线性动力有效应力分析。计算中以应变空间的多重剪切机构塑性模型为本构关系。用神户市港岛地下３２ｍ深处实测的地震加速度作为输入波形，同时考虑了地基、结构与流体的相互作用。计算结果表明，沉箱顶部最大水平残余位移为３．４１ｍ，最大沉降１．５６ｍ，沉箱倾斜角为３．２°。有效应力的预测结果与地震后实测结果基本一致。计算结果还表明，沉箱背后回填土的液化和沉箱下部置换砂中超静孔隙水压力的升高对沉箱岸壁抗震性能有重要影响。此外，还探讨了地基处理对地震下沉箱变形的影响。     

液化场地-群桩基础-结构体系动力响应分析—大型振动台模型试验研究

进行了液化场地-结构体系动力相互作用大型振动台试验,对土体和桩基的加速度反应、饱和砂土层的孔压反应等进行了测试。重点阐述了土体和群桩基础的加速度地震响应特征和饱和土体的孔压发展规律,并对土体侧向变形规律进行了分析。试验研究结果表明：0.05g拍波输入时,土体和桩基对加速度反应有着明显放大作用,土体各处孔压比增长幅度不大,土体侧向位移较小;0.3g汶川地震卧龙台地震记录输入时,桩基加速度反应规律与土体反应基本一致,土体孔压比增长明显,上部土体完全液化;土体水平侧向变形较大。本文成果可为液化场地-群桩基础动力相互作用研究做对比分析和验证数值模拟工作提供参考。     

基于地震变形控制的隧道地基注浆抗液化加固效果评价

 目前理论上主要有两种液化防治思路：一种是限制超孔隙水压力的产生与发展;另一种是减少液化产生的过大变形。目前,基于前一种设计思想的液化处理方法和研究较多,而对基于变形控制的处理方法实施效果的研究则相对有限。从后一种思路出发,基于Biot固结理论,利用循环弹塑性本构模型,通过数值模拟方法,对上海某电厂取排水隧道的地震液化问题进行模拟,建立一种平面应变条件下隧道地震液化变形的数值模拟方法,以评估其注浆预防液化的加固效果。其中重点分析了地震作用下加固前后该隧道地基的位移、加速度、超孔隙水压力等动力反应。结果表明,采用适当的抗液化处理措施可以较好地抑制地基液化变形,这为工程场地抗震设计及液化防治提供了科学依据,对类似工程的可液化场地处理具有良好的借鉴作用。     

坝坡地震永久变形分析

结合大坝工程实例,根据堆石料的大型动三轴试验结果,确定了坝料的残余体应变和残余剪应变模式,特别是非饱和料的残余体应变模式.在所建立的面板坝三维非线性动力反应有限元法基础上,结合孔隙水压力扩散和消散的计算,建立了一套同时计入残余体应变和残余剪应变的面板堆石坝地震永久变形的计算方法.最后,结合案例进行了地震永久变形的计算,分析了坝体地震永久变形的量值和分布情况,为大坝的抗震设计提供了有力的技术依据.     

地震液化离心机振动台模型试验与LEAP研究进展

离心机振动台模型试验是研究地震液化问题的重要手段,一方面可重现场地地震响应和揭示液化致灾规律,为发展工程设计方法提供依据;另一方面可以作为特定边值问题的标准模型试验数据,验证数值方法与土体本构模型及其参数选取的合理性。介绍了离心机振动台模型试验的试验原理,回顾了离心机振动台模型试验在地震液化领域的主要研究进展。围绕由中国、美国、日本和英国等国家高校与研究所联合开展的国际合作项目“液化试验与分析”（LEAP）,重点介绍了若干为提高离心机振动台模型试验可重复性而发展的物理模拟新技术,包括离心机振动台的台面振动控制技术、模型土体弹性波速测试技术和基于图像分析的动态位移监测技术等。最后针对地震液化领域的若干工程和研究需求,探讨了离心机振动台模型试验领域的发展趋势。     

Observations of dynamic and non-dynamic interactions between a quay wall and partially stabilised backfill

The dynamic and non-dynamic interactions between a gravity-type quay wall and a backfill ground were investigated by centrifuge model testing, considering cases in which a rigidly cement-stabilised ground existed at varying distances from the quay wall. In conducting the centrifuge tests, the performance of the instrumentation applied to measure the pressure from granular soils was critically assessed. At non-dynamic states, the backfill confined between the quay wall and the rigidly stabilised soil block exerted smaller earth pressure at deeper locations, at both apparently active and transient states. The calculation, based on perfect plasticity and considering friction arching, was useful in explaining these results. A similar feature was also observed during the steady-state oscillations, in the case of dry sand backfill, and was associated with the system’s increased seismic stability. In underwater cases, the pore water fluctuations in the backfill dominated the total earth pressure behaviour, with the active pressure being smaller again from a confined fill than from a fully extending one. Despite the reduced active pressure, placing the stabilised soil in the proximity of the quay wall increased the wall’s permanent seaward movement, unless the two bodies were in direct contact. This ostensible association of smaller active pressure with greater instability in the underwater cases cannot be explained by the conventional, simplified conception of the active earth pressure as a unilateral cause of instability. The evaluation of such unconventional backfill conditions seems to require rigorous consideration of the simultaneous soil–water-structure interactions.     

地震作用下饱和回填砂土重力式挡土结构滑动与转动位移分析

 预测地震作用下重力式挡土结构的位移是基于位移抗震设计方法的关键。基于Newmark滑动理论、超孔隙水压力应力模型和累积损伤原理,建立饱和回填砂土中超孔压比时程计算模型,以及墙体滑动和转动临界加速度时程计算模型。基于所建立的模型,提出用于计算饱和回填砂土重力式挡土结构滑动和转动位移的计算方法。采用该方法,分析土体参数和地震动参数对墙体滑动及转动位移的影响,并对墙体滑动与转动的耦合作用进行研究。结果表明,填土不发生液化的情况下,滑动位移对土体相对密度和墙体与地基土间的摩擦角十分敏感;转动位移对输入地震的震级、水平加速度和竖向加速度、填土的内摩擦角、墙背摩擦角和相对密度均较为敏感。超孔隙水压力对墙体滑动和转动位移的影响不可忽视。在地震作用下墙体与墙后填土破坏土楔体共同运动的假设条件下,墙体滑动与墙体转动相互抑制。     

Seismic response of precast reinforced concrete wall subjected to cyclic in-plane and constant out-of-plane loading

This paper provides insight into the seismic behavior of a full-scale precast reinforced concrete wall under in-plane cyclic loading combined with out-of-plane loading replicated by sand backfill to simulate the actual condition of basement walls. The tested wall exhibited flexural cracks, owing to the high aspect ratio and considerable out-of-plane movement due to lateral pressure from the backfill. The wall performed satisfactorily by exhibiting competent seismic parameters and deformation characteristics governed by its ductile response in the nonlinear phase during the test with smaller residual drift. Numerical analysis was conducted to validate experimental findings, which complied with each other. The numerical model was used to conduct parametric studies to study the effect of backfill density and aspect ratio on seismic response of the proposed precast wall system. The in-plane capacity of walls reduced, while deformation characteristics were unaffected by the increase in backfill density. An increase in aspect ratio leads to a reduction in in-plane capacity and an increase in drift. Curves between the ratio of in-plane yield capacity and design shear load of walls are proposed for the backfill density, which may be adopted to determine the in-plane yield capacity of the basement walls based on their design shear.     

Negative Pore Air Pressure Generation in Backfill of Retaining Walls During Earthquakes and its Effect on Seismic Earth Pressure

In order to investigate the seismic behavior of conventional type and geosynthetic-reinforced soil retaining walls, 1-g model shaking tests were conducted. Model walls having a height of about 50 cm were placed on a subsoil layer and backfilled with a layer of dense dry Toyoura sand. They were subjected to several steps of horizontal irregular excitations. As a result, generation of negative pore air pressure in the backfill was observed. The maximum amplitude of the negative pore air pressure during each shaking step increased with the base acceleration. Based on analyses of the measured data, it was inferred that such negative pore air pressure was caused by outward wall displacement relative to the backfill and not by dilative behavior of the backfill. It would cause a reduction in the seismic earth pressures exerted from the backfill. This feature suggests an advantage of a rigid full-height facing for reinforced soil walls over the segmental types of facing. A simplified numerical procedure to evaluate earth pressure was applied while considering the effects of the negative pore air pressure, and it could qualitatively simulate the measured behavior in terms of the seismic earth pressure and the angle of failure plane in the backfill.     

Behavior of Sheet Pile Quay Wall Stabilized by Sea-Side Ground Improvement in Dynamic Centrifuge Tests

Sea-side ground improvement is one of the techniques used for increasing seismic stability of sheet pile quay wall. A series of centrifuge shaking table test is conducted to investigate the seismic behavior of sheet pile quay wall stabilized with sea-side cement deep mixing (CDM). At 50 g centrifugal acceleration, the clay ground is consolidated and four to five stages of shaking are applied to the quay wall. The recorded input-output accelerations, deflection of the quay wall, earth pressures along depth and pore pressures were used to evaluate the behavior of the stabilized sheet pile quay wall. The results indicated that an improved area provides significant resistance against seismic loading. The ground improvement can reduce 30% to 60% bending moment during the seismic loading. The horizontal deflection of the quay wall decreases rapidly with increase in area of the CDM until it reaches a certain limit. Prediction by the numerical model agrees fairly well with the results of centrifuge model tests.     

Numerical analysis of consolidation behavior of soil-bentonite backfill in a full-scale slurry trench cutoff wall test

The stress state of the SB backfill in a full-scale cutoff wall test during the construction and consolidation was simulated by a finite-element model. The applicability of the model was demonstrated by good agreements between modeled and field monitored earth pressures and pore pressure in the backfill. Based on the analyzed results, the backfill consolidation process can be described as a four-staged cycle of load transfer: (1) the effective stress of the backfill increases due to the dissipation of excess pore pressure caused by self-weight consolidation of the backfill; (2) the increased effective stress results in settlement of the backfill and an increase of sidewall friction between the backfill and the sidewall interface; (3) the increased sidewall friction results in the transfer of backfill weight to the sidewalls and a decrease of the consolidation stress on the backfill; and (4) the decreased consolidation stress attenuates the decrease of excess pore pressure, influencing the subsequent consolidation. The cycle from (1) to (4) continues until the consolidation is completed.     

地震时地下连续墙围束效应与围束土壤超孔隙水压力之探讨

以三维有限元程序仿真研究受地下连续墙围束土壤其受震时之反应。以1995年阪神地震波为输入条件,土体为中紧密度砂土及疏松砂土时发现:随着地震方向地下连续墙位置之靠近,围束体内部的土体最大水平向位移将跟着减少,其中又以在中紧密度砂的效果明显于松砂之效果;在松砂中之超孔隙水压生成速度明显比中紧密砂快;中紧密砂中之超孔隙水压于受激发过程会因土体剪胀之故,局部期间有下降现象;中紧密砂之液化因地下连续墙围束效应明显降低。     

加筋挡土墙在二维超静孔压下的稳定分析

当加筋挡土墙后填土为粘性土时,在其中可能会产生超静孔隙水压力.超静孔压的存在使其土压力的大小及分布、潜在滑裂面的位置都有所改变.一维孔压分布情况下朗肯理论仍能适用.但在二维孔压分布情况下,用朗肯理论进行计算就不合适.本文推荐采用图解法计算墙后土压力,用圆弧滑动法进行稳定校核.对二维正孔压分布和基坑支护结构上负孔压分布的情况都做了探讨.     

强地震荷载作用下临水挡土墙的拟动力法稳定性分析

 假设墙后填土破坏面为曲面,用正弦波模拟地震加速度时程曲线,采用拟动力法对临水挡土墙进行稳定性分析,确定了挡土墙和墙后填土所受的阻尼力和惯性力,获得地震荷载作用下挡土墙的被动土压力、抗滑和抗倾覆稳定性系数的封闭形式解析解。定量分析地震加速度、放大系数、墙后填土的物理力学参数和动水压力对挡土墙的滑动位移、挡土墙的抗滑和抗倾覆稳定性系数的影响,得出当地震加速度、放大系数越大,水位越高,内摩擦角越小,临水挡土墙的稳定性越差。