强度参数对初始随机缺陷岩样全部变形的影响

在单轴平面应变压缩条件下, 采用FLAC模拟了初始内聚力及内摩擦角对具有随机材料缺陷岩样轴向、侧向、体积变形及由侧向应变及轴向应变计算得到的泊松比的演变的影响。采用编写的FISH函数于试样内部规定随机缺陷并计算其全部变形特征。密实的岩石服从莫尔库仑剪破坏与拉破坏复合的破坏准则, 破坏之后呈现应变软化—理想塑性行为。随着强度参数(初始内聚力及内摩擦角)的增加, 应力峰值及对应的侧向应变的值提高, 体积应变的峰值增加, 应力峰值所对应的计算得到的泊松比稍有增加。由于被剪切带所分割的毗邻块体之间的相对滑动, 纵然扩容角为零, 试样在峰后的变形阶段, 仍然可以观察到体积膨胀现象, 这与作者的理论分析结果一致。当强度参数降低时, 侧向应变—轴向应变曲线、体积应变—轴向应变曲线及计算得到的泊松比—轴向应变曲线的峰前非线性部分变得短暂。剪切带倾角的数值解的上限低于Coulomb理论, 下限在Roscoe理论附近波动, Arthur理论的预测结果与本文剪切带倾角的数值解更接近.      

Damping formulation for nonlinear 1D site response analyses

Measurements and observations of ground shaking during large earthquakes have demonstrated the predominant role of site effects in the response of infrastructure during a seismic event. Despite significant efforts to model the hysteretic response and nonlinearity of soils due to medium and large ground motions, the most widely accepted nonlinear site response methods are not able to represent simultaneously the changes of stiffness and energy dissipation (damping) observed in both laboratory tests and during earthquake events. This paper presents two new soil damping formulations implemented in nonlinear one-dimensional site response analysis for small and large strains. The first formulation introduces an approach to construct a frequency-independent viscous damping matrix which reduces the over-damping at high frequencies, and therefore, the filtering at those frequencies. The second formulation introduces a reduction factor that modifies the extended Masing loading/unloading strain–stress relationship to match measured modulus reduction and damping curves simultaneously over a wide range of shear strains. A set of examples are introduced to illustrate the effect of using the two proposed formulations, separately and simultaneously, in nonlinear site response analyses.     

A modified parallel IWAN model for cyclic hardening behavior of sand

A modified parallel IWAN model, which includes a cyclic hardening function, is proposed and verified. The proposed model consists of elasto-perfect plastic and isotropic hardening elements. The model is able to predict cyclic hardening behavior through the adjustment of the internal slip stresses of its elements beyond the cyclic threshold, and satisfies Bauschinger's effect and the Masing rule with its own behavior characteristics. The cyclic hardening function is developed based on the irrecoverable plastic strain (accumulated shear strain) of dry sand during shearing, which is assumed to be a summation of shear strain beyond the cyclic threshold. Symmetric-limit cyclic loading and irregular loading tests were performed to determine model parameters and to verify the behavior of the proposed model. Finally, a one-dimensional site response analysis program (KODSAP) is developed by using the proposed model. The effects of cyclic hardening behavior on site response are evaluated using KODSAP.     

四分量钻孔应变观测资料的换算和使用

水平四分量钻孔应变仪观测的是地表附近一点的水平应变变化. 但是其直接记录并非应变变化,应根据互检条件先进行实地相对标定(计算元件校正系数),然后用理论固体潮进行实地绝对标定(计算探头校正系数),才能进行应变换算,给出可作为应变变化使用的数据. 因为钻孔应变仪观测的是应变变化,所以实地标定和应变换算都需要用增量. 对于精确的研究,这些校正系数都可能随时间变化,因而需要根据具体问题按特定时间段对校正系数进行计算. 该文比较系统地说明了四分量钻孔应变观测资料换算和使用的基本步骤和具体方法,并以姑咱台的观测资料为例,给出了具体分析结果.     

地壳形变深井综合观测技术的新进展

简要讨论了国内外钻孔应变观测技术近10年来的发展动态,分析了美、日技术的特点,然后,介绍了作者依据自身的技术积累,研制新型深井综合观测系统取得的进展。所研制的RZB型深井地壳形变宽频带综合观测系统采用数字化电容式位移传感器,具有噪声低、动态范围大的特点;基于井下数据总线技术,使得按不同要求进行观测系统集成非常灵活;通过完善井下探头安装工艺,提高了深井安装的质量。最后,对北京百善和福建漳州两个深井地壳形变综合观测实验站的建设及观测数据进行了讨论。     

Metamorphism and Tectonics in Southern Madagascar: An Overview

The scope of this paper is to briefly summarize the general tectonic pattern and the metamorphic evolution of the continental crust from southern Madagascar. After a presentation of the main geophysical features of the Malagasy crust, the brittle and the ductile strain patterns are established at a crustal scale. The Pan-African metamorphic zonation is discussed and interpreted through a tectonic model related to a transpressive regime.     

汶川大震时福建四种观测系统的体应变响应分析

采用福建省有关观测点的井水位、地震仪、体应变仪与伸缩仪的分钟值观测资料对福建地区对2008年5月12日四川汶川8．0级大震的体应变响应进行了计算．计算结果表明．由井水位、体应变仪与伸缩仪所得到的对汶川大震的体应变响应的振幅为10^-7～10^-8,而由地震仪所得到的体应变响应要比前者大1个数量级;并对此差异进行了分析。     

中国大陆现今水平形变动态特征

2001~2004大陆水平应变场大致沿玉树、阿尼玛沁、鲜水河、小江等断裂带形成一条由东西走向转为南北走向的应变高值带.2004~2007高值带向局部收缩,并维持前期高值.新疆于田M_S7.3、四川汶川M_S8.0分别位于该高值带的东段、西段剪应变梯度带上,具备大尺度形变背景.分析认为昆仑山M_S8.1对青藏高原内部块体、川滇块体的相对运动产生重大影响,导致震中两侧一系列断裂带附近区域水平差异运动处于较高水平,印尼M_S8.7地震则有利于上述区域应变能进一步积累.此外,2001~2004、2004~2007应变分布特征总体从无序趋向有序,体现构造应力场经历调整与再积累过程.现阶段太平洋板块、菲律宾板块俯冲作用可能有所增强.     

Strain and kinematic vorticity analysis: An indicator for sinistral transpressional strain-partitioning along the Lancangjiang shear zone,western Yunnan,China

This work deals with the preliminary relationship between strain path and strain partitioning pattern in a sinistral transpressional zone,Lancangjiang shear zone,located to the southeast of Tibet.Various ductile rocks provide an opportunity to investigate quantitative finite strain(Rs),kinematic vorticity values(Wm),and proportions of simple and pure shear components.The mean kinematic vorticity values(Wm) were evaluated based on three methods,such as Rs-θ,prophyroclast hyperbolic distribution method(PHD),a...