Numerical simulation of the undrained stability of slopes in anisotropic fine-grained soils     

Sergi Conesa  Miguel Mánica  Yu Huang 《Geomechanics and Geoengineering》2019,14(1):18-29

The undrained stability of slopes in anisotropic fine-grained soils is studied in this paper using the finite element method (FEM). A constitutive model is presented, able to account for the observed variation of undrained strength with loading direction. The model is able to encompass the different strength distributions observed in normally, slightly overconsolidated and heavily overconsolidated soils. A series of stability analyses have been performed to explore the effect of the type of undrained strength anisotropy on the stability and failure mechanisms of slopes of different inclinations. In addition, a real case study of the failure of an underwater slope is analysed with the numerical approach presented. It suggests that, by considering undrained strength anisotropy, the failure can be satisfactorily explained.  相似文献   

1920年海原8.5级地震震中区地电阻率各向异性研究     

刘元生  吴子泉  陈惠云  姜早峰 《华北地震科学》2005,23(3):9-12

通过海原8.5级地震震中区环行电测深研究,发现在断层破碎带有明显的电阻率各向异性,垂直断层走向呈现明显的高电性,断层走向呈现明显的低电性.根据电性差异讨论了断层地表的变形特征.研究结果表明：环形电测深工作,对研究地面附近地层物性变化有重要意义.  相似文献   

瞬变电磁快速成像解释系统研究   总被引：14，自引：2，他引：12       下载免费PDF全文

郭文波  李貅  薛国强  宋建平  顾林生 《地球物理学报》2005,48(6):1400-1405

为了提高瞬变电磁测深法对地探测的垂向分辨能力,文中研究了磁偶源瞬变电磁法快速成像的方法.详细讨论了电磁波与地震波在介质中的传播规律,分析了磁偶源瞬变电磁场在远区的响应特性.根据磁偶源瞬变电磁场与反射地震波的传播规律的相似性,提出了TEM资料拟地震快速成像解释的思路.理论模型正、反演计算结果表明方法理论是可行的,野外实测资料处理结果进一步说明了该方法是有效的.  相似文献   

一个变泥质岩包体样品的系统热磁试验及其矿物学意义   总被引：6，自引：2，他引：4       下载免费PDF全文

刘庆生  刘振东  刘青松  刘勇胜  高山 《地球物理学报》2005,48(4):876-881

利用一件采自河北汉诺坝周坝地区变泥质岩包体样品,结合系统的低温和高温磁性测量结果,探讨了应用热磁实验鉴别样品中所含原生磁性矿物的多解性问题. 结果表明, 饱和等温剩余磁化强度（SIRM）在室温～250℃以及280℃～380℃的降低分别由高钛钛磁铁矿的剩磁解阻过程（一种物理过程）以及由磁赤铁矿转换成赤铁矿（一种矿物相变）引起.样品在500℃以后磁化率的升高则是由磁铁矿从钛磁赤铁矿中出溶所致.因此,κ T（即磁化率随温度变化）曲线中呈现约580℃居里点是由加热过程中次生的磁铁矿引起,而并非代表原始（即加热前）样品中的磁铁矿成分.  相似文献   

Modeling the Effects of Heterogeneity and Anisotropy on the Excavation Damaged/Disturbed Zone (EDZ)   总被引：2，自引：0，他引：2  

S. H. Wang  C. I. Lee  P. G. Ranjith  C. A. Tang 《Rock Mechanics and Rock Engineering》2009,42(2):229-258

Summary  When modeling the mechanical behavior of underground excavations, it is necessary to include the influence of the rock mass characteristics on the Excavation Damaged/Disturbed Zone (EDZ). In this paper, the Realistic Failure Process Analysis code, RFPA, is used to model the extent of the EDZ. The inhomogeneous characteristics of rock at the mesoscopic level are included by assuming that the material properties of the constituent elements conform to a Weibull distribution; the anisotropy is incorporated as a transversely isotropic medium; the non-elastic characteristic is simulated via an elastic damage-based constitutive law. A finite element program is adopted as the basic stress analysis tool. In this study, a notable feature is that no a priori assumptions need to be made about where and how fracture and failure will occur – cracking can take place spontaneously and can exhibit a variety of mechanisms when certain local stress conditions are met. The deformation and failure process of anisotropic rock around excavations of different geometries is analyzed, and compared to experimental tests, showing similar fracture patterns. Additionally, the effect of confining stress and of different material layers is modeled and discussed. It is found that the model clearly illustrates that fracturing, both initiation and propagation, occurs as a combination of the stress concentrations and weakness planes introduced via the transverse anisotropy – which could represent either foliations or ubiquitous joint sets. Correspondence: Dr. Shuhong Wang, Box 265, School of Resource and Civil Engineering, Northeastern University, Shenyang 110004, P.R. China  相似文献   

Elastic Solution for Deep Tunnels. Application to Excavation Damage Zone and Rockbolt Support   总被引：1，自引：1，他引：0  

A. Bobet 《Rock Mechanics and Rock Engineering》2009,42(2):147-174

Summary  A new formulation is presented for deep circular tunnels in rock with cylindrical anisotropy. The formulation is an exact solution since it satisfies equilibrium, strain compatibility, and the anisotropic constitutive model. Complete solutions have been found for two scenarios: tunnel with excavation damage zone, and tunnel with rockbolt support. The solution is based on the assumption of a deep, circular tunnel in a medium with two homogeneous zones: an inner zone surrounding the tunnel, which is either isotropic or anisotropic, and an outer zone, for the remainder of the medium, which is isotropic. Plane strain conditions, elastic response of rock, rockbolts and support, and simultaneous excavation and support installation are also assumed. For tunnels surrounded by an excavation damage zone with reduced rock properties, the tangential stresses and the radial deformations at the tunnel wall are very sensitive to both the magnitude of stiffness reduction of the damaged rock and the size of the damaged zone. The effect of the rockbolts on the rock is approximated by treating the rockbolt-rock composite as a material with cylindrical anisotropy with stiffnesses related to the properties of the rock and rockbolts, and spacing of the rockbolts. Comparisons between the analytical solution and a numerical method show small differences and provide confidence in the approach suggested.  相似文献   

Crustal anisotropy in southwest Ireland from analysis of controlled source shear-wave data     

P.W. Readman  F. Hauser  B.M. O'Reilly  V.C. Do   《Tectonophysics》2009,474(3-4):571-583

Results from a travel-time analysis of three-component shear-wave (S-wave) data recorded in southwest Ireland during a controlled source seismic experiment have been used to investigate the magnitude of crustal anisotropy. The data used were recorded from 20 in-line shots on three-component short-period stations deployed at approximately 1-km spacing along two parallel profiles. Analysis of the travel-time differences between vertically and horizontally polarised S-waves recorded on vertical, radial and transverse seismometer components was undertaken using seismic phases travelling near the Earth's surface (S_g) and reflected from the Moho (S_mS). Travel-time differences between the components for both phases scatter largely within the range ± 0.2 s, which is about the uncertainty in the measurements, with no observed coherent variation with shot-receiver offset. Synthetic S-wave seismograms were also computed from 1-D S-wave velocity models with varying degrees of anisotropy in the upper and in the lower crusts. Travel-time differences of S_g and S_mS phases picked from these synthetic seismograms confirm that for anisotropies with probable symmetries of magnitude 1–2% in either the upper or lower crust should result in an observable variation of the travel-time differences between the transverse and radial, and transverse and vertical components with source–receiver offset. The study shows that crustal anisotropy does not contribute significantly to the marked anisotropy recently deduced from SKS and SKKS measurements in Ireland, which is therefore confirmed to reside at sub-crustal and deeper mantle levels.  相似文献   

现今的地幔流动及其与板块构造的相互作用:从观测证据得到的推论     

高祥林 《地球物理学进展》2004,19(3):560-567

地震波速度结构层析成像和地震各向异性分析,是推测现今地幔流动的主要观测依据．从已有研究结果看,全球尺度的地幔流动的两个主要边界驱动力是顶部的冷却和底部的加热,地幔的密度和粘度控制流动速率．沿海沟由消减板带动的地幔下沉,和沿热点下面幔柱及洋中脊的地幔上升,是地幔垂直向流动的表现．GPS等测量显示的全球板块运动在一定条件下反映地幔顶部的水平流动．地幔柱可能有不同的根源深度,沿幔柱上升的地幔流在200—350km深度转变为水平流动．消减带附近有复杂的地幔流动格局,表明局部构造条件对地幔流动的影响．大陆下一般出现两个地幔各向异性层,较深的可能反映地幔流动,并与大陆根的状态有关．在不同构造环境下,地幔流动与板块构造之间有不同形态的相互作用关系,它可能驱动板块运动,也可能对板块运动产生阻力。  相似文献   

有明黏土各向异性固结特性的试验研究     

加瑞  雷华阳 《岩土力学》2019,40(6):2231-2238

由于大多数黏土矿物是片状的,在沉积和随后的固结过程中黏土颗粒和组构单元趋向水平定向排列,使天然沉积黏土呈现各向异性的固结特性。通过垂直切和水平切试样的恒应变速率固结试验研究了日本有明黏土的各向异性固结特性。试验结果表明,水平切试样的先期固结压力pch与垂直切试样的先期固结压力pcv的比值在0.5～1.0之间,主要是因为天然沉积黏土各向异性的屈服轨迹以及垂直切和水平切试样所经历的应力路径不同;在正常固结阶段,水平切试样的固结系数ch与垂直切试样的固结系数cv之比约为1.43,水平切试样的渗透系数kh与垂直切试样的渗透系数kv之比约为1.40,水平切试样的体积压缩系数mh与垂直切试样的体积压缩系数mv基本相等。因此,有明黏土固结系数的各向异性主要是因为渗透系数的各向异性,而渗透系数的各向异性本质上是因为其微观结构的各向异性。  相似文献   

焦石坝地区页岩各向异性及其影响的分析研究     

李文成  扶喆一 《物探与化探》2019,(2):266-272

黑色富含有机质页岩由于沉积方式的特殊性,一般具有较强的各向异性。但现有大部分研究是基于各向同性理论开展页岩储层预测工作,这与页岩的实际地质特点不符。文中联合利用实验室岩石力学测试数据以及各向异性参数经验公式计算焦石坝地区页岩的各向异性参数,并进一步探讨了各向异性对页岩岩石速度、储层AVO响应特征以及岩石力学参数计算的影响。结果表明,各向异性对页岩速度、脆性指数预测结果影响较大,在地层倾角较大时进行速度分析及页岩可压性预测时应考虑各向异性参数的影响;同时,AVO正演结果表明地震反射入射角小于40°时,各向异性算法与各向同性算法计算的页岩AVO响应差异较小,利用各向同性叠前反演方法进行页岩储层预测具有可行性。  相似文献