Numerical Analysis for Granular Ground Using the Advanced DEM

本研究的主要目的是证明DEM是一种检查岩土工程问题的有用方法，此外，还可以清除地面作为颗粒材料的行为。首先，为了达到这些目的，开发了弹塑性型DEM，它表达了单元接触引起的塑性能量耗散，并与固体骨架和孔隙水压力和流动相结合。然而，修正后的DEM的分析结果明显受到塑性常数值的影响。因此，采用单元刚度折减的方法来模拟具有随机孔隙的实体骨架的大变形和不可逆变形。在均匀圆单元的规则布置下，分析了固结和液化问题，并绘制了循环加载过程中孔隙水压力的e-log p曲线和变化。通过这些分析，验证了DEM在砂土地面上的适用性。其次，引入了分形维数分析，对节理面粗糙度进行了评价，并确定了应用于不连续岩体的DEM分析条件。对由数百个均匀矩形块体组成的岩质边坡进行了分析，其中不连续面简化为以下两种模式：‘间歇性’和‘交叉连续’。拟静力倾斜分析与动震分析的对比为探讨岩质边坡的稳定性提供了有效的数据。在此基础上，对沿越池镇海岸公路发生的岩质边坡破坏进行了DEM分析。通过与现场观测结果的比较，得出了边坡破坏的几种可能情景，为判断边坡真正的破坏原因和破坏行为提供了有用的信息。本研究所得结果均满足上述要求。在达到主要目的后，利用DEM的基本理论，提出了一种新的数值计算方法FLEM。FLEM有望成为分析大变形和大流动问题的有力方法。少

The main purposes of this investigation are to demonstrate that DEM is a helpful method in examining geotechnical problems, moreover, to clear the behavior of ground as granular material.First, for the attainment of these purposes, elasto-plastic type DEM was developed, which expressed plastic energy dissipations caused by elements contact, and coupled with solid skeletons and pore water pressures and flow. However, it had be come clear that analytical results of the modified DEM were too much influenced by the values of plastic constants. So large and irreversible deformations of solid skeletons with random generations of pore were modeled by the reduction of element stiffness. Consolidation and liquefaction problems were analyzed with regular arrangements of uniform circle elements, and e-log p curves and changes of pore water pressure during cyclic loading were illustrated. Through these analyses, The applicability of DEM to sandy soil ground was certified.Second, fractal dimensiona … More l analysis was introduced, which was intended to evaluate the roughness of the jointing surfaces and to determine the analytical conditions of DEM in applying to discontinuous rock mass. Analyses for rock slopes composed of hundreds of uniform rectangular blocks were carried out where discontinuities were simplified as following two patterns ; 'intermittent' and 'cross-continuous'. The comparison between pseudo-static inclination analysis and dynamic shaking analysis gave effective data in discussing the stability of rock slopes. After these fundamental colculations, DEM analyses were performed on a rock slope failure which happened along Echizen coast road. Some Probable scenarios of the slope failure were obtained, which may give useful information to judge the true cause and failure behavior by comparison with field observations.All the results obtained from this study fulfilled the requirements as mentioned above. After the accomplishment of the main purposes, a new numerical method named FLEM was expressed utilizing the basic theory of DEM. FLEM is expected to be a powerful method in analyzing large deformation and flow problems. Less