Influence of the intermediate principal stress and principal stress direction on the mechanical behavior of cohesionless soils using the discrete element method     

《Computers and Geotechnics》2017

In this paper, the Discrete Element Method (DEM) is employed to numerically explore the response of hollow cylinder specimens of granular soils under complex stress paths. Two series of numerical tests are conducted to clarify the effects of the principal stress direction α and the intermediate principal stress through the b-value on the mechanical response of granular materials. The effects of α and b-value on the non-coaxiality of the principal stress and the principal plastic strain increment directions are investigated. It is observed that b-value and α significantly affect the non-coaxial behavior of granular materials. Finally, the results are discussed and compared with those obtained from physical laboratory tests.  相似文献   

Dimensionless input parameters in discrete element modeling and assessment of scaling techniques     

《Computers and Geotechnics》2017

A set of dimensionless input parameters were defined for DEM using a characteristic time which is a function of density and elastic modulus of particles and an arbitrary characteristic length. Dimensionless strain rate and mass damping ratio are inversely proportional to the characteristic time, and stress is normalized by elastic modulus to give dimensionless stress. It was demonstrated that the response of a model in the dimensionless scale is invariant with the choice of density, elastic modulus and the characteristic length if dimensionless strain rate and mass damping ratio are kept constant. Small time step is a prohibitive aspect of DEM. Scaling techniques are widely employed to enlarge the time step. Using the dimensionless scheme, it was learned that density scaling is equivalent to the use of a higher strain rate, and stiffness scaling results in a higher strain rate and an elevated stress state in the dimensionless scale.  相似文献   

地震计阶跃标定自动处理算法研究   总被引：1，自引：0，他引：1  

朱小毅  林湛  陈阳  彭朝勇  杨桂存  李建飞  庄丹宁 《地震地磁观测与研究》2010,31(1):43-48

标定是监测运行中的地震计主要技术参数的有效手段,保证了观测数据的产出质量。本文介绍了一种新的地震计阶跃标定算法,旨在提高算法的稳定性和自动化程度,适合计算机自动的,成批的处理标定数据。  相似文献   

非等步长GM(1,1)模型在建筑物变形监测中的应用研究   总被引：1，自引：0，他引：1  

杜海燕  吴吉贤  张耀文 《高原地震》2010,22(1):46-49

将灰色系统理论应用于建筑物变形监测数据分析,针对观测周期的不确定性因素,提出使用非等步长GM(1,1)模型进行监测,并用最小二乘法求解模型参数,给出模型精度的检验方法,并以实际的建筑物的沉降观测数据为例说明应用此方法的全部过程,将分析和预测结果与传统GM模型进行比对,获得了更好的拟合数据和预测数据,且精度更高。  相似文献   

不等长工作面台阶区域覆岩运动诱冲机制及防治     

李杨杨  张士川  高立群  孔德志  孔贺 《岩土力学》2016,37(11):3283-3290

针对阳城煤矿不等长工作面台阶区域发生冲击地压灾害问题,基于工作面特殊布置方式及覆岩赋存特征,采用理论分析、数值模拟和现场实测等方法,分析了台阶区域覆岩结构运动特征和围岩应力演化规律,研究了台阶区域冲击地压诱发机制。研究结果表明：1304工作面台阶区域覆岩经历了“OX-S-C”型较为复杂的结构演变,覆岩空间结构由OX向S型转换时,顶板岩层大面积破断下沉,在台阶区域形成多个悬臂梁结构,越往高位,悬臂梁长度越大;受覆岩运动和采动应力场叠加影响,煤岩体形成高应力集中区,在顶板岩层动载冲击作用下,煤岩体弹性应变能突然释放,诱发冲击地压。采用COMSOL软件对不同卸压钻孔参数下煤体应变能分布特征进行模拟研究,优化了台阶区域卸压钻孔参数。根据模拟结果,随着钻孔孔径、孔深增大及间距减小钻孔卸压效果越明显,考虑工程实际,确定孔径为150 mm、孔深为30 m、间距为1 m为合理有效的卸压钻孔参数,并应用于1302工作面台阶区域的冲击地压防治,取得了较好的防冲效果。  相似文献   

求解模型对欧拉矢量的影响   总被引：1，自引：0，他引：1  

占伟  武艳强  丁晓光  王紫燕  刘志广  孟宪纲 《中国地震》2013,29(1):91-96

利用GNSS水平运动场求解欧拉矢量时,待估参数的个数会对欧拉矢量结果产生影响,针对该问题本文分别从理论推导和具体算例角度进行了分析.首先从理论上推导出不同的求解模型得到的欧拉矢量的差异;然后以2004 ～2007年中国大陆GNSS水平运动场为基础,选用两种常用的求解模型(块体整体旋转模型和块体的整体旋转与均匀应变模型),讨论了求解模型对欧拉矢量及后续研究的影响.结果表明,两种模型下块体整体旋转的差异最大可达2.60mm·a-1,是不能忽略的.因此认为选用不同的块体运动模型会得到不同的地壳水平运动图像,在地壳水平运动分析中对此需加以重视.  相似文献   

基于数字图像测量系统的三轴试样变形研究   总被引：1，自引：0，他引：1       下载免费PDF全文

王健  郭莹 《地震工程学报》2011,33(Z1)

基于亚像素角点检测的图像测量技术能够记录试样表面方块角点每一时刻的位移,从而获得试样的表面应变场。将基于试样表面6行方块分别计算的应变与基于全部6行方块的整体平均计算得到的结果进行比较,显示中间4行方块区域的变形基本不受端部约束影响。还对采用试样上、中、下三个部分与整个试样的测量结果获得的应力与应变特性进行了对比分析。该方法能够测量任意时刻试样的轴向应变场,通过轴向应变场的变化可以准确地描述试样剪切带的产生、发展以及完全形成的全过程。  相似文献   

青海地区各地震带强震活动基本状态探讨     

马玉虎  王培玲  刘文邦 《高原地震》2011,23(4):4-9

利用青海地区1900年以来5级以上强震目录探讨了省内各地震带地震活动的基本状态,结合累积应变能释放现象讨论了各地震带现今地震活动所处的状态。结果显示,青海地区4个地震带强震活动存在明显的平静与活跃的交替特征,这是普遍的宏观规律,但平静与活跃的特点具有差异性。伴随各地震带地震活动状态的不同,其累积应变能释放呈现加速或减速的特征。  相似文献   

磁暴主相多阶发展行星际起因的初步分析          下载免费PDF全文

佟亚男  刘四清  张效信  林瑞淋  龚建村 《地球物理学报》2011,54(6):1439-1456

本文利用1998～2006年与磁云有关的80起中强磁暴(Dst*≤-50 nT),对其主相期间不同发展阶数磁暴的行星际起因进行了统计分析.重点研究了鞘区磁场单独作用、磁云本体单独作用、鞘区与磁云共同作用以及其他复杂行星际结构在磁暴主相多阶发展中的相对重要性,并对导致磁暴主相增加一阶的行星际起因做了初步分析.统计结果表明...  相似文献   

On the lag time between internal strain and basement involved thrust induced exhumation: The case of the Colombian Eastern Cordillera     

《Journal of Structural Geology》2013

Thrust sheets accumulate internal strain before they start moving along discrete fault planes. However, there are no previous studies evaluating the time difference between initiation of strain and fault displacement. In this paper we use observations from the Eastern Cordillera of Colombia to evaluate this interval. We utilize multiple thermochronometers and paleothermometers to refine the timing of deformation. Based on these new data we build time-temperature path estimates that together with geometric outcrop-based structural analysis and fluid inclusions allow us to assign relative timing to features associated with strain, such as cleavage, veins and certain types of fractures, and compare that with the timing of thrusting. We find that cleavage was only formed close to maximum paleotemperatures, almost coeval with the onset of thrust-induced denudation by the Late Oligocene. The corresponding structural level of fold-related veins suggest that they were formed later but still when the country rocks were at temperatures higher than 160 °C, mostly during the Early Miocene and still coexisted with the latest stages of cleavage formation. Our data show that the main period of strain hardening was short (probably a few million years) and occurred before first-order basement thrusting was dominant, but was associated with second-order folding.  相似文献