边坡大变形损伤破坏的高效无网格模拟

首先讨论了Lagrangian和Eulerian无网格近似的联系和区别,然后基于稳定节点积分和增量本构理论,建立了分析边坡静动力破坏的高效大变形无网格法,并给出了详细的计算流程。该方法采用弹塑性损伤耦合本构关系来模拟岩土类材料的破坏演化过程,其中屈服函数采用Drucker-Prager准则,损伤准则为基于应变的各项同性损伤函数。由于无网格近似和稳定节点积分具有非局部近似的特性,在保证空间离散稳定性和提高计算效率的同时,也可准确有效地模拟应变集中所形成的剪切带的发生与扩展,通过数值算例验证了方法的有效性。     

爆破震动灾害主动控制方法研究

在微差爆破工程中,用干扰降震法实现爆破震动灾害主动控制的关键在于确定合理的微差延期时间。由于所使用的普通雷管存在延期误差,设计或选择的延期微差时间往往与实际的有较大出入,影响了微差爆破的效果和顺利实施。确定微差爆破中的实际微差延迟时间对优化微差爆破效果、降低爆破地震效应具有很大的现实意义。用基于小波分析的时能密度法以及信号时-频域转换技术,从实测微差爆破震动信号中分离出各分段震波,通过比较各分段震波在不同延期时间下的叠加效果,得到了微差爆破的较优微差延期时间,实现了爆破震动灾害主动控制。该方法对研究爆破震动效应及其灾害的控制,具有较高的理论和应用价值,为系统开展爆破震动危害控制和预测研究奠定了理论和技术基础。     

锦屏一级左岸导流洞出口边坡开挖支护有限元模拟

锦屏一级水电站左岸导流洞出口边坡岸坡陡峻,层间挤压破碎带、顺坡卸荷裂隙及深部裂缝发育。边坡开挖将切除部分维持边坡稳定的坡脚岩体,从而对工程边坡及上部变形拉裂岩体的稳定性产生不利影响。基于锚固岩体弹塑性等效本构关系,采用弹塑性有限元法对边坡开挖、加固及地震作用进行了数值模拟,分析了开挖边坡的稳定性,并对初拟的“先锚后挖、边挖边锚”的施工程序的合理性进行了评价,提出了若干对工程建设具有一定指导意义的建议。     

不同建模假定下岩石损伤黏弹模型的参数转换关系探讨

将外界因素对岩石变形的影响考虑为瞬间弹性损伤和长期蠕变损伤,并根据加载瞬间弹性模量及蠕变模量的劣化分别对瞬间弹性损伤变量和蠕变损伤变量进行定义,由此建立了考虑损伤的kBurgers模型。在此基础上,通过假定泊松比和体积模量为常量分别得到了对应的模型三维表达式,并得到了不同建模思路下模型参数间的换算关系。最后结合实际算例,对常体积模量假定下模型参数随含水率变化的损伤演化规律进行了分析,获得了常体积模量假定下模型的瞬间弹性损伤和长期蠕变损伤演化方程,检验了模型参数换算关系的有效性。     

The deformation of overburden soil induced by thrust faulting and its impact on underground tunnels

Overburden soil beds situated above a fault are often deformed by propagation of bedrock thrusting from the fault during large earthquake. The deformed beds formed a triangular shear zone. This coseismic faulting often causes damage to underground tunnels located in the shear zone. The present research studies the deformation behavior of the overburden soil beds and the tunnel, the associated mechanism and the impact on the safety of tunnel linings induced by a large blind thrust slip. Based on sandbox experimental and numerical studies, it is found that results from numerical analysis are in agreement with the sandbox model tests with regard to growths of the shear zones within the soil beds, location of the tunnel in this shear zone and deformations of the tunnel. The potential major shear zone may be bent or bifurcated into two sub-shear zones owing to existence of a tunnel inside the shear zone. Furthermore, the occurrence of back-thrust faulting will threaten the safety of nearby structures. It was also identified that stiffness of the soil and the fault dip angles are among the major factors controlling the configuration of shear zones, the stresses within the soil, and the loads on tunnel linings. Based on the identified mechanisms, the strategies for hazard prevention are accordingly suggested and discussed.     

基于弹塑性理论的修正分层总和法

建议了土体的非线性弹性-塑性本构方程,其中弹性矩阵采用Duncen-Chang本构模型,塑性部分则采用修正剑桥模型;提出了基于弹塑性理论的修正分层总和法新理论;该理论既有常规分层总和法简单,便于理解运用的优点,又能考虑土体的弹性非线性以及塑性变形特性,同时还能考虑土体三向应力对其变形的影响。为基础变形计算提供了一种较为理想的算法。     

开采沉陷三维损伤有限元分析

针对上覆岩体结构的复杂性,将节理、裂隙及正交各向异性岩体视为损伤岩体,建立了裂隙损伤岩体三维动态有限元分析模型,给出了较详细的三维仿真模拟有限元实施格式,完成了可考虑多种工程因素且能在WINDOWS下运行的三维模拟软件。分析模拟结果显示,对岩体结构复杂性的处理方式是可行的,所研制软件是有效的。     

冻土与结构接触面循环剪切损伤模型

抗剪强度和压缩体应变是冻土与结构接触面的力学特性指标中最重要的两个参数,对冻土与结构接触面的力学分析至关重要。采用自行研制的大型多功能冻土-结构接触面循环直剪系统,开展了冻土与结构接触面力学性能及变形规律的试验研究,采用损伤力学理论,基于等应变分布假设、零弹性域假设、弹性应变无耦合假设,选择不可逆性体应变与最大不可逆性体应变的比值作为损伤因子,建立了用于描述冻土与结构接触面剪切行为的抗剪强度与压缩体应变损伤模型。通过相关试验对建立的损伤模型进行验证,结果表明,所建模型是准确、合理的。     

边坡落石运动轨迹计算新方法

考虑落石形状对落石运动轨迹的影响,将落石近似成椭圆形。根据落石运动的5种常见形式,即自由落体运动、斜抛运动、碰撞、滑动和滚动,分别得到了各种运动形式的运动速度计算公式。在碰撞阶段考虑了地面的弹塑性变形,得到了与碰撞前速度、落石形状和地面材料有关的恢复系数计算公式,并根据接触力学的有关理论得到了碰撞冲击力的计算公式,给出了落石连续滚动的判别条件。将理论公式应用于重庆万州首立山落石运动轨迹预测,验证了理论公式的可行性和有效性。     

An Overview of Some Significant Eastern Canadian Earthquakes and Their Impacts on the Geological Environment,Buildings and the Public

Numerous moderate to large earthquakes have occurred in eastern Canada. Some ofthese events had significant geological effects such as surface faulting, liquefaction,submarine slumping, rock avalanches, rock falls, landslides, railroad embankmentslides, and one tsunami. Some of these earthquakes caused considerable damage tobuildings with unreinforced masonry elements that were located on thick clay deposits. These events also had strong psychological and social impacts, mainly due to the unpreparedness of the population. To minimize these impacts, programs should be designed to map the land and offshore areas most susceptible to mass movements (Earth Sciences), to define buildings most at risk (Engineering) and to educate the public about mitigation actions (Education, science popularization).