Centrifuge Modeling of Rock Slopes Susceptible to Block Toppling

Summary This paper presents the results of centrifuge tests that were aimed at validating the Goodman-Bray method for rock slope toppling analysis. The Goodman-Bray method was extended by the authors to accommodate non-persistent basal planes of rock columns. Two gypsum column models, with and without anchors were used to represent the failure modes. Measured critical centrifuge accelerations were in agreement with the results obtained from numerical modeling. A background of the toppling slope failures associated with a large hydropower project in China instigated the need for the centrifuge study. The centrifuge model tests used an artificial rock. The observed failure mode did not follow a straight failure plane as proposed by Goodman and Bray. The failures revealed a bi-planar slip surface with a deep-seated portion near the toe of the slope. The outcomes of the centrifuge tests illustrated the need to search for the critical failure surface when performing a toppling analysis. The search technique is similar to that usually performed in a conventional sliding analysis.     

Evaluating assumptions for seismic assessment of existing buildings

This paper evaluates the American FEMA 356 and the Greek GRECO (EC 8 based) procedural assumptions for the assessment of the seismic capacity of existing buildings via pushover analyses. Available experimental results from a four-storeyed building are used to compare the two different sets of assumptions. If the comparison is performed in terms of initial stiffness or plastic deformation capacities, the different partial assumptions of the procedures lead to large discrepancies, while the opposite occurs when the comparison is performed in terms of structural performance levels at target displacements. According to FEMA 356 assumptions, effective yield point rigidities are approximately four times greater than those of EC 8. Both procedures predicted that the structure would behave elastically during low-level excitation and that the structural performance level at target displacement for a high-level excitation would be between the Immediate Occupancy and Life Safety performance levels.     

Nonlinear seismic response analysis of arch dam-foundation systems- part II opening and closing contact joints

A time-domain method for the analysis of arch dam-foundation rock dynamic interaction during earthquake was proposed, and the dynamic relaxation technique was adopted to obtain the initial static response for dynamic analysis by [Du et al. (2005). The paper has been contributed to Bulletin of earthquake engineering]. In this paper, a nonlinear explicit method in time domain considering the opening and closing effect of contact joints on arch dam during earthquake is further proposed by introducing the dynamic contact force model into the method. The simulation accuracy of dynamic contact force model is verified by comparing its calculation result and test result of scale model on shaking table. Finally, the influence of joints on the seismic response of Xiaowan arch dam is studied by the proposed method and some conclusions are given.     

3D裂隙网络随机模拟及其工程应用研究

岩体中存在的大量随机分布的裂隙对岩体的工程性质及稳定性有着极其重要的影响。传统的工程地质研究方法难以客观地描述其空间分布特征。应用概率与统计学的理论 ,通过统计分析得到裂隙的分布规律性 ,采用随机模拟的方法实现与统计分布相适应的裂隙网络是研究随机裂隙宏观特征的有效途径。通过模拟所得的 3D裂隙网络 ,进一步研究了裂隙的连通特征及工程开挖面上的稳定分析与加固措施优化的方法     

南水北调西线雅砻江调水工程温波引水枢纽坝址径流计算的研究

南水北调西线雅砻江调水工程（简称西线调水）是从长江的一级支流雅砻江上游区引水至黄河源头地区的跨流域调水工程，是补充黄河水资源不足与解决我国西北和华北部分地区干旱缺水的重大战略措施，由于引水枢纽坝址缺乏实测水文资料，我们依据附近孜水文站实测资料，采用一些非确定性的数理统计模型来计算温波引水坝址的设计年径流量，并对计算成果进行了合理性分析，结果表明，上述计算成果基本反映了温波引水坝址径流变化的客观情况，从而为南水北调西线雅砻江调水工程缺乏实测水文资料地区的水文计算提供了科学依据。     

Micro-sheeting of granite and its relationship with landsliding specifically after the heavy rainstorm in June 1999, Hiroshima Prefecture, Japan

Certain types of granite in mountainous areas are microscopically sheeted to a depth of 50 m due to unloading under the stress field that reflects slope morphology. Micro-sheets generally strike parallel to major slope surfaces and gently dip downslope, forming cataclinal overdip slopes. The cataclinal overdip slope accelerates creep movement of micro-sheeted granite, which in turn loosens and disintegrates granite via the widening or neoformation of cracks, probably in combination with stress release, temperature change, and changes in water content near the ground surface. The surface portion of micro-sheeted granite is thus loosened with a well-defined basal front, which finally slides in response to heavy rain. Innumerable landslides of this type occurred in Hiroshima Prefecture, western Japan, following the heavy rainstorm of 29 June 1999. Following such landslides, the weathering of micro-sheeted granite exposed on the landslide scar recommences, setting the stage for future landslide.     

关于大地电磁的静校正问题

本文从理论上严格地论述了大地电磁测深曲线静态位移的原理,简单介绍了目前国内外所采用的静校正方法,并着重分析了我们所用的压制表层电性不均匀干扰的办法及其效果。     

岩石节理粗糙度系数的分形特征

岩石节理粗糙度系数JRC是估算节理抗剪强度和变形指标最重要的参数。通过对简易纵剖面仪获取的节理表面轮廓曲线的分形研究,讨论了节理表面轮廓曲线的自相似性和JRC的自相似性,并根据实测统计资料的分析,指出了分形理论研究JRC的适用条件和有效的使用方法。由实测统计资料的JRC尺寸效应自相似性分析,认为JRC尺寸效应具分形结构。本文介绍了一种确定JRC尺寸效应分维数D的方法,由此确定的分维数D具有明确的物理意义。     

Development and validation of a metallic haunch seismic retrofit solution for existing under‐designed RC frame buildings

The feasibility and efficiency of a seismic retrofit solution for existing reinforced concrete frame systems, designed before the introduction of modern seismic‐oriented design codes in the mid 1970s, is conceptually presented and experimentally investigated. A diagonal metallic haunch system is introduced at the beam–column connections to protect the joint panel zone from extensive damage and brittle shear mechanisms, while inverting the hierarchy of strength within the beam–column subassemblies and forming a plastic hinge in the beam. A complete step‐by‐step design procedure is suggested for the proposed retrofit strategy to achieve the desired reversal of strength hierarchy. Analytical formulations of the internal force flow at the beam–column‐joint level are derived for the retrofitted joints. The study is particularly focused on exterior beam–column joints, since it is recognized that they are the most vulnerable, due to their lack of a reliable joint shear transfer mechanism. Results from an experimental program carried out to validate the concept and the design procedure are also presented. The program consisted of quasi‐static cyclic tests on four exterior, ? scaled, beam–column joint subassemblies, typical of pre‐1970 construction practice using plain round bars with end‐hooks, with limited joint transverse reinforcement and detailed without capacity design considerations. The first (control specimen) emulated the as‐built connection while the three others incorporated the proposed retrofitted configurations. The experimental results demonstrated the effectiveness of the proposed solution for upgrading non‐seismically designed RC frames and also confirmed the applicability of the proposed design procedure and of the analytical derivations. Copyright © 2006 John Wiley & Sons, Ltd.     

曙光雷达数据处理软件系统

针对岩土工程探测对象的隐蔽性与复杂性,开发了曙光雷达数据处理软件系统,实现了不同类型雷达数据的共享数据处理、分形处理、偏移、联合反演、小波变换等功能;现场验证及试用结果表明,该软件系统可以改善地下目的物探测的分辨率和真实度,可为岩土工程施工提供较准确的地下障碍物资料。