用（DDA+FEM）方法数值模拟1975年海城、1999年岫岩地震发生的过程l

用非连续变形分析方法（DDA+FEM）， 数值模拟了华北地区各地块相互制约构造环境中发生的1975年海城地震及1999年岫岩地震的过程. 通过对岫岩前震及近期余震分布图象的研究， 以及前人对海城地震的研究， 提出了海城、 岫岩地震发震构造块体模型. 数值模拟结果给出了两次地震释放的主应力变化、 最大剪应力变化等值线图， 地震前后位移变化矢量图， 及发震断层滑移随时间的变化， 分别与相应地震的震源机制、 宏观等震线、 发震断层的走滑性质等的结果基本一致.      

Sphere-boundary edge and sphere-boundary corner contacts model in DDA for simulating particulate media in 3-D

In modelling particulate media, such as soils, using 3-D DDA, there are four types of contacts: sphere to sphere, sphere to boundary face, sphere to boundary edge, and sphere to boundary corner contacts. The first two were studied by the authors in a previous work (Beyabanaki and Bagtzoglou 2012). In this paper, we present a new contact model for sphere-boundary edge and sphere-boundary corner contacts in sphere-based 3-D DDA. The model includes a new algorithm to search for contacts, detect the contact types and calculate contact points. Moreover, formulas for contact sub-matrices are derived. The proposed contact model has been implemented into a sphere-based 3-D DDA program and three test cases are studied in order to verify the workability of the new contact model. The numerical results obtained demonstrate the capability of the model to deal with sphere-boundary interaction in particulate media.     

非连续变形分析（DDA）方法在高海拔高烈度地区公路边坡稳定性分析中的应用

分析了天山某公路边坡发育的工程地质特征,并结合高海拔高烈度地区公路冻融作用强烈的特征,引入了冻融折减系数,采用非连续变形分析(DDA)方法模拟了该段边坡变形破坏全过程。结果显示,在各种内外营力的综合作用下,目前该段边坡处于时效变形阶段,变形破坏主要集中于浅表部;DDA模拟结果表明,在天然状态下该段边坡处于基本稳定状态,但在地震工况及地震+冻融工况下易于发生浅表层的滑移式崩塌。结合以上边坡变形破坏特征,提出了采用清除坡表危岩+插别加固的综合治理措施。      

基于界面元法的向家坝重力坝深层抗滑稳定分析

重力坝的深层抗滑稳定分析多采用刚体极限平衡分析方法和非线性有限元法,但通常的刚体极限平衡法不能反映坝基岩体渐近失稳过程和破坏的力学机制,非线性有限元法则难以解决坝基中软弱结构面位移不连续问题。结合向家坝工程,建立了泄④坝段的计算模型,采用界面元法进行了大坝深层抗滑稳定分析,给出了坝基中破坏区的范围和分布,以及坝基的渐进破坏过程和可能滑体的抗滑稳定安全系数等成果,为坝基处理措施提供了重要的技术参考依据。研究结果表明,所建立的分析方法可以自然描述坝基岩体各种介质的错动、张开和滑移等不连续变形的特征,可用于重力坝坝基的深层抗滑稳定 分析。     

间断伽辽金法(DGM)求解弹性地基梁问题

间断伽辽金法使用节点位移一类未知数作为测试函数,削弱了内部单元边界上的一阶及n阶导数的连续性,大大降低了构造形函数的难度,特别适合控制方程为高阶微分方程问题的求解。基于间断伽辽金法的基本原理,推导了弹性地基梁四阶微分控制方程的积分“弱”形式,编制了计算程序,进行了数值计算和收敛性分析。计算结果表明：用间断伽辽金法求解弹性地基梁问题是十分有效率的。     

Approximation of Sahelian rainfall fields with meta-Gaussian random functions

For the purpose of numerically studying sahelian storm rainfields, a family of random functions is described with a characterization of its finite dimensional law. Some problems appearing when fitting its functional parameters are put forward and two solutions to bypass those problems are provided, according to the regularity properties of the marginal cumulative distribution function. An illustration of this method is implemented on a set of sahelian rainfields of event accumulation displaying a strong spatial intermittency.     

东江沙卵石河床浅滩-深潭序列水沙演变特征

东江是珠三角网河区入汇河流之一,属少沙河流,其上游浅滩-深潭序列密集分布,河床结构的演变特性尚不清晰。选取东江浅滩-深潭序列河段进行现场河床质与推移质测量,结合试验得到不同流量和坡降中水流与河床在无上游来沙补给中的互馈机理。试验结果表明：浅滩与深潭交替造成沿程平均流速不连续变化,浅滩中部在洪水流量的塑造下容易产生紊动能峰值。无上游来沙条件下,序列中粗化层的形成、破坏过程交替与循环发生,其中静态分选是主导因素且导致沿程级配不连续。流量与坡降的增大促进浅滩-深潭序列发育,同时使得深潭与浅滩的纵向长度缩短;有上游来沙条件下推移质输沙率增大,无来沙条件下输沙率减小。     

Modified predictor-corrector solution approach for efficient discontinuous deformation analysis of jointed rock masses

The high computational costs associated with the implicit formulation of discontinuous deformation analysis (DDA) have been one of the major obstacles for its implementation to engineering problems involving jointed rock masses with large numbers of blocks. In this paper, the Newmark-based predictor-corrector solution (NPC) approach was modified to improve the performance of the original DDA solution module in modeling discontinuous problems. The equation of motion for a discrete block system is first established with emphasis on the consideration of contact constraints. A family of modified Newmark-based predictor-corrector integration (MNPC) scheme is then proposed and implemented into a unified analysis framework. Comparisons are made between the proposed approach and the widely used constant acceleration (CA) integration approach and central difference (CD) approach, regarding the stability and numerical damping features for a single-degree-of-freedom model, where the implications of the proposed approach on open-close iteration are also discussed. The validity of the proposed approach is verified by several benchmarking examples, and it is then applied to two typical problems with different numbers of blocks. The results show that the original CA approach in DDA is efficient for the simulation of quasi-static deformation of jointed rock masses, while the proposed MNPC approach leads to improved computational efficiency for dynamic analysis of large-scale jointed rock masses. The MNPC approach therefore provides an additional option for efficient DDA of jointed rock masses.     

Modeling the interaction between fluid flow and particle movement with discontinuous deformation analysis (DDA) method

Coupled hydro‐mechanical processes in granular media represent the interaction between solid particles movement and fluid flow during external and/or internal loading. The processes attract attention in geotechnical engineering since they cause many disasters such as landslide, slope collapse, boiling/quicksand and soil liquefaction, etc. This study presents a numerical method combining discontinuous deformation analysis (DDA) for mechanical calculation and finite element method for fluid flow simulation to model the interaction between solid particles' movement and fluid flow from microscopic point of view. The term of hydraulic pressure was newly formulated and introduced to the original DDA. The simplified examples are given to verify the new method, and the computational results correlate well with the theoretical calculations, further development is also considered. Copyright © 2010 John Wiley & Sons, Ltd.