内蒙古二连盆地额仁淖尔凹陷断裂系统特征

额仁淖尔凹陷位于华北板块与西伯利亚板块的缝合带上,张扭作用下,正断层系与变换断层系构成了复杂的断裂系统.剖面上,断裂系统可分为深部伸展断裂系统和浅部张扭断裂系统,并呈现出典型的"花状"断裂组合样式.平面上,断裂呈左阶雁行状排列,断裂分段连接特征明显,变换构造发育.断裂活动可划分为4期:阿尔善组初始断陷期,腾一段张扭裂陷期,腾二段强烈裂陷期和赛汉组断拗转换期.     

基于显式时间积分的球颗粒DDA计算方法

非连续变形分析方法（DDA）是一种平行于有限元法的新型数值计算方法,该方法基于最小势能原理,把每个离散块体的变形、运动和块体之间的接触统一到平衡方程中进行隐式求解。然而,传统DDA方法在计算过程中需组装整体刚度矩阵并联立求解方程组,在用于大型岩土工程问题的三维数值模拟时占用内存较大、耗时较长、计算效率极低。因此,提出一种基于显式时间积分的三维球颗粒DDA方法。该方法在求解过程中不需要组装整体刚度矩阵,在求解加速度时,由于质量矩阵为对角矩阵,可存储为一维向量占用内存较少,且可分块逐自由度求解,效率较高,在接触判断上采用最大位移准则简化了接触算法,采用较小的时步,保证了计算的精确性;通过几个典型算例验证了该方法的准确性及计算效率。     

一种改进步长自调的非连续变形分析法

非连续变形分析（DDA）是一种针对块体系统变形和位移求解的数值计算方法。引入Newmark方法于结构动力学微分方程中,考虑惯性力和阻尼力作用,改进时间步长自动调节,并实现DDA求解程序;比较研究Newmark方法中的线性加速法、常加速法和平均加速法在DDA程序中计算的收敛速度,讨论块体系统动力学计算过程中DDA方法对惯性力和阻尼力的添加和删除,并提出根据计算精度要求的误差控制实现方案。将改进的DDA方法模拟一个典型的煤与瓦斯突出过程,取得了满意的计算结果,该改进算法为DDA方法处理动力学问题提供新的途径     

基于统一强度理论分析不连续面对岩体强度的影响

基于统一强度理论,对含有结构面的岩体,在平面形式下引入材料统一强度参数ct,φt,推导了含单个节理裂隙岩体材料的统一强度公式,即考虑中间主应力的岩体破坏强度公式,并分析了其有效范围。运用硅藻质软岩和石膏的三轴试验结果,验证了所建立的公式的正确性,并分析了具有不连续面岩体的强度随中间主剪应力作用系数b的变化。结果表明,岩体强度随b值的增大而增大。根据岩土材料统一强度参数的确定方法,计算并分析了b值对强度参数的影响,从而说明强度参数随着b值的变化而变化。     

碰撞带倾角和摩擦系数对陆-陆碰撞变形的影响

借助一个简单的大陆与大陆碰撞模型,即把两个大陆的碰撞简化为两个粘弹性块体的碰撞,两个块体之间的不连续变形面对应两个大陆之间的碰撞断裂带,运用三维粘弹性拉格朗日非连续变形有限元(LDDA)方法,通过分析模型中不连续变形面的存在对两个粘弹性块体碰撞变形的影响,探讨了大陆碰撞断裂带的倾角和摩擦系数对两个大陆碰撞变形影响的一般规律,给出了大陆碰撞变形的一些显著的特点。尽管运算模型的几何尺寸、边界条件等参考了印度和欧亚大陆碰撞的实际特征,但所得结果适用于更一般的情况。研究结果表明,碰撞断裂带倾角和摩擦系数对陆-陆碰撞变形有着重要的影响。当断裂带倾角在15~30°时,两个大陆板块碰撞导致的仰冲板块一侧隆升高度相对更大,利于形成高大的山脉,其中以15°倾角对应的仰冲板块一侧隆升最高;当断裂带倾角在30~45°时,两个大陆板块碰撞导致的俯冲板块的俯冲深度相对更深,利于形成深陷的盆地,其中以45°倾角对应的俯冲陆块一侧俯冲最深;当断裂带倾角≥75°时,两个大陆板块之间的相对俯冲和仰冲作用变得不明显。碰撞断裂带摩擦系数越小,碰撞过程中两个大陆板块之间相对俯冲和仰冲作用越强,形成高大的山脉和深陷的盆地要求碰撞断裂带摩擦系数≤0.2。从大陆与大陆碰撞变形构造特征看,除发育前陆盆地-山脉系统外,在仰冲陆块一侧靠近造山带后缘还发育呈不对称结构的挤压性凹陷,当两个大陆板块碰撞断裂带倾角在15~30°时,该类型凹陷更容易形成,其中以30°倾角对应的凹陷最深,反映其形成可能是大陆碰撞过程中陆块之间相对俯冲和仰冲运动的综合结果。     

滑坡运动过程仿真分析

滑坡是一个动态过程，滑坡体的运动是一个集滑动，转动，拉张等运动方式的复杂运动过程，传统的极限平衡和计算和有限元分析均无法描述滑坡的运动学特点和运动过程。非连续变形分析（DDA）是最近发展起来的一种新的离散数值分析方法。该方法基于块体的运动学理论及数值分析，可以开展块体的静力和动力学计算。应用非连续变形分析方法对长江三峡区新滩滑坡的运动全过程进行了数值模拟研究，模拟方案充分依据该滑坡的地质，地形特征，按不同岩土体和地质结构面类型进行块体单元的划分，共划分成504个块体单元。模拟结果表明，新滩滑坡是以斜坡中部姜家坡一带的局部破坏为其运动的开始阶段，并进一步牵引上部滑体和推动下部滑体。代表性块体单元的位移变化曲线和滑动速度变化曲线反映了滑动过程中滑坡体块体系统的变形是非连续的，各处块体的动态形态各异，从而很好地再现了新滩滑坡的整个动态过程，揭示了滑坡的运动机制。     

Boundary Element based Discontinuous Deformation Analysis

A Boundary Element based Discontinuous Deformation Analysis (BE‐DDA) method is developed by implementing the improved dual reciprocity boundary element method into the open close iterations based DDA. This newly developed BE‐DDA is capable of simulating both the deformation and movement of blocks in a blocky system. Based on geometry updating, it adopts an incremental dynamic formulation taking into consideration initial stresses and dealing with external concentrated and contact forces conveniently. The boundaries of each block in the discrete blocky system are discretized with boundary elements while the domain of each block is divided into internal cells only for the integration of the domain integral of the initial stress term. The contact forces among blocks are treated as concentrated forces and the open–close iterations are applied to ensure the computational accuracy of block interactions. In the current method, an implicit time integration scheme is adopted for numerical stability. Three examples are used to show the effectiveness of the algorithm in simulating block movement, sliding, deformation and interaction of blocks. At last, block toppling and tunnel stability examples are conducted to demonstrate that the BE‐DDA is applicable for simulation of blocky systems. Copyright © 2016 John Wiley & Sons, Ltd.     

构造环境对煤矿区地表环境灾害的控制作用

在不同构造环境下,同样强度的地下采矿活动在地表所造成的环境灾害现象是有明显差异的。在不同构造条件的煤矿区,地质环境的抗扰动能力不同,因而对地下开采的承载能力也就不同。抗扰动能力强的煤矿区可以承受较大的开采强度,而抗扰动能力差的煤矿区,同样强度的地下开采,就会导致严重的地表损害甚至环境灾害。从这个意义上说,与地下采矿有关的煤矿区地表环境灾害,源于采动,但其形式与发展受控于构造环境。      

Removing irregular frequencies by a partial discontinuous higher order boundary element method

The phenomenon of irregular frequencies is a puzzle in the course of calculating the interaction of waves and structures by the boundary element method. To remove the irregular frequencies, the modified integral domain method is adopted, and continuous higher order elements and partial discontinuous higher order elements are used for discretization. By these means, the effects of the irregular frequencies are effectively removed. Effective strategies have been adopted to deal with singular integrals and nearly singular integrals at different situations. The numerical results of the horizontal wave force on a uniform cylinder in the first order and second order diffraction problems show that the present method has a good validity. At the same time, the influence of collocation parameter on accuracy of numerical results is examined in detail.     

Local discontinuous Galerkin method for far-field underwater explosion shock wave and cavitation

The shock wave and cavitation are main effects in the far-field underwater explosion, which could cause serious damage to marine structures. In this paper, the fluid mechanical behavior of blast load is described by the propagation of pressure wave. The acoustic pressure caused by far-field explosion is determined by solving the wave equation, where a strongly discontinuous axisymmetric numerical model is established with the local discontinuous Galerkin (LDG) method. The model can calculate the dynamic pressure in the fluid field and capture the high-resolution shock wave. The pressure cutoff model is employed to deal with the cavitation effect due to the reflection of the shock wave. The numerical model is verified by comparing with the analytical solution of the cavitation effect near the structure in one dimension. With the same mesh discretization, the present model shows higher precision than the results calculated by the acoustic finite element method. In addition, the propagation of shock wave in the cylindrical water column is studied. Finally, the formation, growth and collapse of the cavitation region near the free surface are simulated. The LDG model can remove the spurious oscillations behind the shock front and it’s more accurate than the results of the acoustic finite element method, in terms of capturing the sharpness of shock wave and calculating the shock and cavitation loading. And the present model can be applied to calculate the structural damage caused by shock wave in three dimensions.