地裂缝场地施工降水对地表沉降和地层应力的影响研究

地裂缝是西安市典型的城市地质灾害，地下水位的变化是诱发地裂缝活动的重要因素。以西安地铁六号线暗挖段施工降水为研究背景，基于有限元数值模拟计算，分析了地裂缝场地施工降水引起的地表沉降规律和地层应力变化特征。计算结果表明:当地下水位下降时，地表沉降量上盘大于下盘，地裂缝带两侧地表存在差异沉降的现象，最大差异沉降量与地下水位下降深度近似呈直线关系；不同位置处地表的横向沉降呈现出"Z"形的变化特征，差异沉降区随地裂缝位置的变动而变化，且差异沉降量与横向地表位置近似呈二次函数曲线关系；地层竖向应力随着地下水位下降而增大，地裂缝位置处地层应力存在突变现象，上下盘应力影响区与地层深度近似呈三次函数曲线关系；基于分层总和法计算了地下水位下降时地表沉降量的解析解，并与数值模拟结果进行对比，发现两种方法计算结果基本一致，得到了计算地表最大沉降量的经验公式。研究结果可为地裂缝场地地铁隧道及其他地下工程安全施工提供科学指导。      

浙江湖州地区膨胀土特征探讨

文章通过膨胀土的分布、成因类型、成分和结构特征及物理、力学性质的分析 ,证实膨胀土并非是理想的持力层     

A new scheme for numerical modelling of flow and transport processes in 3D fractured porous media

The objective of this work is to develop a new numerical approach for the three-dimensional modelling of flow and transient solute transport in fractured porous media which would provide an accurate and efficient treatment of 3D complex geometries and inhomogeneities. For this reason, and in order to eliminate as much as possible the number of degrees of freedom, the fracture network, fractures and their intersections, are solved with a coupled 2D–1D model while the porous matrix is solved independently with a 3D model. The interaction between both models is accounted for by a coupling iterative technique. In this way it is possible to improve efficiency and reduce CPU usage by avoiding 3D mesh refinements of the fractures. The approach is based on the discrete-fracture model in which the exact geometry and location of each fracture in the network must be provided as an input. The formulation is based on a multidimensional coupling of the boundary element method-multidomain (BEM-MD) scheme for the flow and boundary element dual reciprocity method-multidomain (BE-DRM-MD) scheme for the transport. Accurate results and high efficiency have been obtained and are reported in this paper.     

Mantle process beneath Philippine Sea back-arc spreading ridges: A synthesis of peridotite petrology and tectonics

Abstract In order to obtain a general view of the mantle process beneath a back‐arc basin spreading ridge, the diversity of peridotite petrology and tectonic occurrences in two back‐arc basin spreading ridges from the Philippine Sea were examined: the Parece Vela Rift and the Mariana Trough. The Parece Vela Basin spreading ridge (Parece Vela Rift) was a physically fast/intermediate‐spreading ridge, although many tectono‐magmatic features resemble those of slow‐ to ultraslow‐spreading ridges. Two unusual features of the Parece Vela Rift further demonstrate the uniqueness of the ridge: full‐axial development of oceanic core complexes and exposure of mantle peridotite at segment midpoints. The Parece Vela Rift yields a lithological assemblage of residual but still fertile lherzolite/harzburgite, plagioclase‐bearing harzburgite and dunite; similar assemblages are reported from the equatorial Mid‐Atlantic Ridge at the Romanche Fracture Zone and the ultraslow‐spreading ridges from the Indian and Arctic Oceans. The tectono‐magmatic characteristics of the Parece Vela Rift suggest that diffuse porous melt flow and pervasive melt–mantle interaction were the important mantle processes there. Globally, this ‘porous melt flow‐type’ mantle process is likely to occur beneath a segment midpoint of the ridge having a thick lithosphere, typically an ultraslow‐spreading ridge. In contrast, the Mariana Trough is a typical slow‐spreading ridge, exposing mantle peridotite at segment ends. The Mariana Trough yields a lithological assemblage of residual harzburgite and veined harzburgite, a common assemblage among the global abyssal peridotite suite. The tectono‐magmatic characteristics of the Mariana Trough suggest that channeled melt/fluid flow and limited melt–mantle interaction are the important mantle processes there, because of the colder wall‐rock peridotite in the segment end. This ‘channeled melt flow‐type’ mantle process is likely to occur in the shallow lithospheric mantle at the segment ends of any spreading ridges.     

淮河流域(河南段)第四纪地层沉积规律

本文详细介绍了第四纪地层划分原则,确定了第四纪下限与各世内分的时间,对河南段各个时期地势、各统的沉积规律进行了阐述,确定了含水层主流相与边缘相.     

复杂地层暗挖隧道穿越人行天桥施工技术

以正在建设中的北京地铁十号线双井一劲松区间工程暗挖隧道为例，叙述了浅埋隧道穿越人行天桥的施工技术，并通过监控量测对该技术进行了检验。     

应用深层平板载荷试验选择桩端持力层

深层平板载荷试验是一种新兴的原位测试方法。通过安阳某工程人工挖孔扩底灌注桩深层平板载荷试验的现场实践,确定了不同土层地基土的承载力特征值,为设计单位选择持力层提供数据,并为甲方节省了大量建设资金。     

A computational method for approximating a Darcy–Stokes system governing a vuggy porous medium

We develop and analyze a mixed finite element method for the solution of an elliptic system modeling a porous medium with large cavities, called vugs. It consists of a second-order elliptic (i.e., Darcy) equation on part of the domain coupled to a Stokes equation on the rest of the domain, and a slip boundary condition (due to Beavers–Joseph–Saffman) on the interface between them. The tangential velocity is not continuous on the interface. We consider a 2-D vuggy porous medium with many small cavities throughout its extent, so the interface is not isolated. We use a certain conforming Stokes element on rectangles, slightly modified near the interface to account for the tangential discontinuity. This gives a mixed finite element method for the entire Darcy–Stokes system with a regular sparsity pattern that is easy to implement, independent of the vug geometry, as long as it aligns with the grid. We prove optimal global first-order L ² convergence of the velocity and pressure, as well as the velocity gradient in the Stokes domain. Numerical results verify these rates of convergence and even suggest somewhat better convergence in certain situations. Finally, we present a lower dimensional space that uses Raviart–Thomas elements in the Darcy domain and uses our new modified elements near the interface in transition to the Stokes elements.     

红外仪激电仪超前探水技术研究

在１００号矿体工程的斜井开拓中,用构造推断及红外仪激电仪进行超前探水预测预报,经过现场实测、跟踪监测及含水曲线的研究分析,准确预报了前方含水构造部位,防止了水害,加快完成了该矿体的开拓,取得了明显的经济效益。     

Comparison of Galerkin-type discretization techniques for two-phase flow in heterogeneous porous media

A comparison of Standard Galerkin, Petrov-Galerkin, and Fully-Upwind Galerkin methods for the simulation of two-phase flow in heterogeneous porous media is presented. On the basis of the coupled pressure-saturation equations, a generalized formulation for all three finite element methods is derived and analysed. For flow in homogeneous media, the Petrov-Galerkin method gives excellent results. But this method fails miserably for problems with heterogeneous media. This is because it is not able to capture correctly processes that take place at interfaces when, for instance, the capillary pressure-saturation relationship after Brooks and Corey is assumed. The Fully-Upwind Galerkin method is superior to the Petrov-Galerkin approach because it is able to give correct results for flow in homogeneous and heterogeneous media for the two models of van Genuchten and Brooks-Corey. The widely used formulation which is correct for the homogeneous case cannot be used for heterogeneous media. Instead the straightforward approach of gradp_c in combination with a chord-slope technique must be utilized.