非均匀饱和半空间的Lamb问题     

王立安  赵建昌  侯小强  刘生纬  王作伟 《岩土力学》2020,41(5):1790-1798

基于Biot多孔介质波动理论,建立孔隙率、密度、剪切模量和渗透系数相互耦合且同时沿深度变化的非均匀饱和半空间模型,引入量化的非均匀梯度表征地基非均匀程度。在柱坐标系下构建以土骨架位移和孔隙压力为基本未知量的三维动力控制方程,采用算子运算和Hankel积分变换求解控制方程,推导出简谐集中力作用下半空间地基振动响应的积分解。将所得结果分别退化到均匀饱和半空间和弹性半空间与经典Lamb解做了对比,验证了结果的正确性。利用已有研究结论,给出孔隙率、密度、剪切模量和渗透系数之间的耦合关系式,代入推导结果进行数值计算。分别对水饱和地基和气饱和（干土）地基的动力响应进行分析,给出两类地基在动力作用下的振动位移和孔隙压力分布,并对非均匀性的影响作出分析。结果表明：4参数沿地基深度耦连变化对地基的动力响应产生一定程度影响,振动位移和孔隙压力在地层中的衰减速度由此加快。由于水的黏滞性远大于气体,所以水饱和地基中的振动衰减更快。非均匀程度越高,耦合效应的影响越明显。  相似文献   

静压沉桩引起邻近隧道水平位移计算方法研究     

贺雷  张洋  马山青 《岩土力学》2020,41(11):3740-3747

静压沉桩过程中会产生强烈的挤土效应,使得桩周土及邻近的地下电缆隧道产生扰动变形,如果变形过大,可能破坏隧道的防水结构,造成隧道渗漏水,严重影响隧道的正常使用及安全。在圆柱孔扩张理论及基床系数法的基础上,研究了饱和软土地区静压沉桩作用下周边地层及邻近既有电缆隧道应力及水平位移的理论计算方法;考虑群桩效应,推导了单排群桩施工造成邻近既有电缆隧道水平位移的理论计算方法,并研究了群桩效应影响系数的取值范围;最后,开展了实际工程的理论计算和数值模拟。研究结果表明：提出的方法可方便计算出单桩及单排群桩施工造成的邻近既有电缆隧道的水平位移,计算结果与数值模拟结果吻合性良好。研究可为有邻近桩基施工时电缆隧道的扰动预测及保护提供参考。  相似文献   

Revegetation impacts on runoff generation processes in a typical loess catchment     

Hailong Pan  Qihua Ran  Sheng Ye 《水文研究》2024,38(2):e15092

Since 1999, large-scale ecosystem restoration has been implemented in the Loess Plateau, effectively increasing regional vegetation coverage. Vegetation restoration has significantly elevated the saturated hydraulic conductivity (Ks) of the near-surface soil layers and increased the vertical heterogeneity of the Ks profile. Many studies have examined the change of runoff due to revegetation, yet the impacts of Ks profile on the soil moisture distribution and runoff generation processes were less explored. In this study, numerical simulations were conducted to investigate how changes in the Ks profile caused by vegetation restoration influenced the hydrological responses at event scale. The numerical simulation results show that the increase of surface Ks caused by vegetation restoration can effectively reduce runoff at event scale. Moreover, the enhancement of vertical heterogeneity of Ks profiles can significantly change the vertical profile of soil water content, prompting more water to percolate into the deep soil layer. When rainfall exceeds a threshold, the accumulation of soil water above the relatively less permeable layer can cause short-term saturation in shallow soil layers, resulting in a transient perched water table. As a result, after the vegetation restoration in the Loess Plateau, though Horton overland flow is still the main runoff generation mechanism, there is a possibility of the emergence of Dunne overland flow under the high vegetation coverage (e.g., NDVI larger than 0.5). This emergence of new runoff generation mechanism, saturation excess runoff, in the Loess Plateau due to the vegetation restoration could provide scientific guidance for water and sediment movement, soil and water conservation practices, and desertification control in the Loess Plateau.  相似文献   

Closure to “anisotropic hydraulic conductivity and critical hydraulic gradient of a crushed sandstone–mudstone particle mixture”     

Zhen-Feng Qiu 《Marine Georesources & Geotechnology》2018,36(6):640-642

A closure is presented to the discussion of Anisotropic hydraulic conductivity and critical hydraulic gradient of a crushed sandstone–mudstone particle mixture by Salahou, Jiao, and Yousif (2017 Fener, M., and N. Yesiller. 2013. Vertical pore structure profile of a compacted clayey soil. Engineering Geology 166:204–15. doi:10.1016/j.enggeo.2013.08.001.[Crossref], [Web of Science ®] , [Google Scholar]). The relationship between the critical hydraulic gradient and the uniformity coefficient can be limited to two curves. The internal erosion mechanism of soils with different particle grade curves is different. The maximum diameter of fine particles of different particle grade curves can be calculated by a lot of methods. The density of the original paper is the average density. The anisotropic hydraulic conductivity is caused by uneven density distribution. The hydraulic conductivities are tested on the saturated soils. The saturated hydraulic conductivity can be regard as a constant value for a saturated soil.  相似文献   

Stiffness Degradation of Undisturbed Saturated Soft Clay in Yangtze Estuary under Complex Stress Conditions     

栾茂田  刘功勋  王忠涛  郭莹 《海洋工程》2010,(3):523-538

Stiffness degradation will occur due to the generation of accumulated pore pressure in saturated soft clays under cyclic loading. The soil static-dynamic multi-purpose triaxial and torsional shear apparatus in Dalian University of Technology was employed to perform different types of test on saturated soft marine clay in the Yangtze estuary. Undisturbed samples of the clay were subjected to undrained cyclic vertical and torsional coupling shear and cyclic torsional shear after three-directional anisotorpic consolidation with different initial consolidation parameters. Investigated were the effects of the initial orientation angle of the major principal stress, initial ratio of deviatoric stress, initial coefficient of intermediate principal stress and continuous rotation of principal stress axes on the stiffness degradation. It is found that the degradation index decreases (or degradation degree increases) significantly with increasing initial orientation angle of the major principal stress and initial ratio of deviatoric stress. Compared to the effects of the initial orientation angle of the major principal stress and initial ratio of deviatoric stress, the effect of initial coefficient of intermediate principal stress is less evident and this trend is more clearly reflected by the results of the cyclic torsional shear tests than those of the cyclic coupling shear tests. At the same cycle number, the degradation index obtained from the cyclic torsional shear test is higher than that from the cyclic coupling shear test. The main reason is that the continuous rotation in principal stress directions during cyclic coupling shear damages the original structure of the soil more than the cyclic torsional shear does. Based on a series of experiments, a mathematical model for stiffness degradation is proposed and the relevant parameters are determined.  相似文献   

某工程蚀变岩孔隙特征及其软弱程度研究   总被引：1，自引：0，他引：1  

杨根兰  黄润秋  王奖臻  林锋  付小敏  曹运江 《矿物岩石》2006,26(4):111-115

孔隙作为岩体的初始损伤,对岩体的强度及变形特性的影响尤为明显,而孔隙发育是研究区内一类力学性质较软弱岩石的显著特征。对蚀变岩孔隙特征的研究是了解蚀变岩的软弱程度及孔隙度对其软弱程度的影响的有效方法。针对此蚀变岩进行岩矿及铸体薄片分析得出蚀变岩孔隙有原生、浅表生及构造3种成因,其中以原生为主。从饱水蚀变岩的常规单轴压缩试验应力-应变全过程曲线上求取蚀变岩的饱和单轴抗压强度及割线模量,再与相应试样的孔隙度进行相关性分析,结果显示出蚀变岩的饱和单轴抗压强度及割线模量均随孔隙度的增加而减小,且呈幂函数关系。由于蚀变岩的饱和单轴抗压强度(R c)及割线模量(E s)作为软硬岩评判标准具有一致性,且两者与孔隙度(n)存在较好的相关性,以此将3者共同作为蚀变岩软弱程度的划分标准,并得出软硬岩分界处n为12%、R c为30 M Pa、E s为5 GPa。  相似文献   

平面S波在饱和多孔热弹性介质边界的反射问题研究          下载免费PDF全文

柳鸿博  周凤玺  郝磊超 《地震工程学报》2021,43(1):105-112

针对饱和多孔介质中热弹性波的传播特性问题,基于多孔介质理论和广义的热弹性模型,研究平面S波在饱和多孔热弹性介质边界上的反射问题.以考虑流-固耦合的饱和多孔介质波动方程和热-弹耦合的广义热弹性基本方程出发,建立饱和多孔介质的热-流-固耦合弹性波动模型.通过引入势函数并考虑自由透水和绝热的边界条件,经过理论推导最终给出在饱...  相似文献