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1.
岩体结构面的各向异性与尺寸效应特征对其力学性质影响较大,综合考虑两者之间的相互关系对工程岩体稳定性评价具有重要意义。全面分析不同尺度结构面的各向异性分布,提出考虑正交方向三维形貌参数的各向异性变异系数AVC3D。通过渐进覆盖法统计4组天然岩体结构面10种不同采样尺寸的各向异性变异系数及其尺寸效应规律。结果表明:各向异性变异系数均随结构面尺寸增大而减小至定值,其与结构面尺寸具有较好的负对数函数关系;通过归一化处理,各向异性变异系数与结构面尺寸呈现较好的线性函数关系,表明各向异性变异系数具有分形结构,分维数D可以实现其尺寸效应的规律统计。该方法揭示了影响结构面形貌特征方向性变化的最大有效倾角 和粗糙系数C的增长幅度会随采样尺寸增大趋于稳定的变化机制,体现了当结构面达到各向异性尺寸效应的阈值后,会呈现出稳定的各向异性规律。 相似文献
2.
博格达山地区二叠纪以来构造应力场解析及地质意义 总被引:1,自引:0,他引:1
博格达山是现代地质学研究的一个热点,但是大部分研究都集中在博格达何时隆升,对于其构造应力场的研究较少。作者通过对博格达山地区不同时代地层中岩墙、节理、褶皱和断层等构造进行分期配套以及构造要素测量分析,认为二叠纪以来博格达山及周缘地区具有较强构造变形,构造应力场可划分为3期:二叠纪末期最大主压应力方向为北西西向,可能与后碰撞伸展作用和乌拉尔碰撞带向东挤压的远程效应有关;侏罗纪末-早白垩世最大主压应力为近南北向,与欧亚板块和拉萨地块的碰撞有关;新近纪以来由于印度板块与欧亚板块相互碰撞的远程效应,博格达山地区最大主应力方向为NNE-NE向。这些结果表明,博格达山具有多期次的构造运动,主要受欧亚板块南缘不同时期小陆块碰撞的控制,并且这些构造应力场对周缘盆地油气成藏具有一定影响。 相似文献
3.
Joshua A. White 《国际地质力学数值与分析法杂志》2014,38(10):1036-1057
This work describes a constitutive framework for modeling the behavior of rough joints under cyclic loading. Particular attention is paid to the intrinsic links between dilatancy, surface degradation, and mobilized shear strength. The framework also accounts for the important effect of shear‐induced anisotropy. The resulting approach is fully three‐dimensional and is not restricted to plane‐displacement kinematics. Both the governing formulation and an algorithm for implicit numerical integration are presented. While the proposed methods are general, we also postulate a specific model that is compared with experimental data. It employs relatively few free parameters but shows good agreement with laboratory tests. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
4.
M. Fakharifar M. K. Sharbatdar Z. Lin A. Dalvand A. Sivandi-Pour G. Chen 《地震工程与工程振动(英文版)》2014,13(1):59-73
This paper presents a new FRP retrofi tting scheme to strengthen local beam-column joints in reinforced concrete(RC) frames.The new retrofi tting scheme was proposed following a preliminary study of four different existing retrofi tting schemes.A numerical simulation was conducted to evaluate the effectiveness of FRP-strengthened reinforced concrete frames by bridging behavior of local joints to the whole structure.Local confi nement effects due to varying retrofi tting schemes in the joints were simulated in the frame model.The seismic behavior factor was used to evaluate the seismic performance of the strengthened RC frames.The results demonstrated that the new proposed retrofi tting scheme was robust and promising,and fi nite element analysis appropriately captured the strength and global ductility of the frame due to upgrading of the local joints. 相似文献
5.
风积黄土垂直节理发育,在黄土塬边或岸边容易观测,受水环境变化影响极易诱发黄土灾害。以黄土垂直节理为研究对象,从黄土垂直节理细微观发育特征入手,总结了黄土垂直节理在横纵方向上发育规律,研究了黄土垂直节理在不同评价尺度上的展现形式、转换机制及形成垂直节理的微细观结构基础。从黄土的沉积动态出发,探讨了垂直节理的垂向发育机制。研究结果表明:垂直节理是黄土在历史沉积过程逐渐形成的,是成岩过程的产物,提出了黄土中存在的孔隙集中带及垂直管状通道是能够发育垂直节理的微细观结构基础,三维CT扫描试验结果为其提供了强有力的证据;其在不同评价尺度上的展现形式不同,在外部作用下(干湿循环作用及黄土堆厚)其垂直节理在微-细-中观是可以向上尺度(扩张特征)或者向下尺度(衰退特征)发育、发展转换的,即尺度转换机制;并借此提出了黄土垂直节理的垂向发育机制。 相似文献
6.
文章统计分析了金川矿区内地层和侵入体中的节理构造,对矿区内的共轭剪节理进行配套、分期,综合区域构造演化史后分析了矿区构造应力场。研究表明,金川矿区从新太古代到古生代至少受到4期古构造应力的作用。第一期构造应力场为NS向的挤压,由阴山陆块与鄂尔多斯陆块碰撞形成华北古陆西部陆块引起。第二期构造应力场为NE-SW向的挤压,与华北克拉通东、西陆块碰撞拼合并参与Columbia超大陆拼合事件有关;其后阿拉善陆块与华南陆块参与Rodinia超大陆拼合事件,应力场持续作用。第三期构造应力场为近NS向的挤压,由祁连洋不断向北俯冲引起。第四期构造应力场为NNE-SSW向的挤压,与祁连造山带发生的强烈造山运动有关。 相似文献
7.
UHTCC新型梁柱节点抗震性能试验研究 总被引:2,自引:0,他引:2
为研究超高韧性水泥基材料新型梁柱节点的抗震性能,进行了6榀缩尺比例为1/2的框架中节点的低周反复载荷试验,对不同轴压比和体积配箍率下梁柱节点的受力特点、裂缝开展形式、滞回特性进行了研究。结果表明,超高韧性水泥基材料能明显改善节点核心区的抗裂性能和剪切延性,具有更好的耗能能力,可部分或全部替代节点处箍筋的抗剪作用,具有良好的经济效益。 相似文献
8.
9.
Development of a notch at the base of a cliff reduces cliff stability and often induces a collapse. Pleistocene limestone coastal cliffs of elevation 5?m in Kuro‐shima, Ryukyu Islands, have a prominent notch with a depth of 3–4?m at their bases. Around these coastal cliffs, collapses different from previous studies of cliff collapses in the Ryukyu Islands were found; collapses in Kuro‐shima have a horizontal failure surface. The horizontal failure surface, situated at the height of the failure surface corresponding to the retreat point of the notch, is bounded by vertical joints cutting the whole cliff and the reef flat in front of the cliff. Two types of horizontal failure surface were found, triangular and quadrangular; the distinction appears to depend on the angle between the vertical joints and the front face of the cliff. Prior to collapse, these cliffs appear to have been separated from the adjacent cliffs by the development of vertical joints. Consequently, a cliff that will collapse can be identified in advance; cliff instability is strongly dependent on the development of a notch. To study the effect of notch development on cliff collapse, the notch depth at which collapse occurs was calculated using stability analysis. Instability of a cliff increases with notch depth; collapse occurs at the horizontal failure surface when the ratio of the notch depth to the seaward length of the cliff is approximately 0·5–0·7 for a triangular failure surface, and 0·7–0·9 for a quadrangular failure surface. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
10.
A nonlinear finite element model for earthquake response analysis of arch dam–water–foundation rock systems is proposed in this paper. The model includes dynamic dam–water and dam–foundation rock interactions, the opening of contraction joints, the radiation damping of semi‐unbounded foundation rock, the compressibility of impounded water, and the upstream energy propagating along the semi‐unbounded reservoir. Meanwhile, a new equivalent force scheme is suggested to achieve free‐field input in the model. The effects of the earthquake input mechanism, joint opening, water compressibility, and radiation damping on the earthquake response of the Ertan arch dam (240 m high) in China are investigated using the proposed model. The results show that these factors significantly affect the earthquake response of the Ertan arch dam. Such factors should therefore be considered in the earthquake response analysis and earthquake safety evaluation of high arch dams. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献