利用有限单元伽勒金法反求非线性流情况下砾石层的渗透系数

地下水流问题的数字计算机的应用,现虽处于高度发展阶段,但在采用这种数学物理模型时,首先要知道含水层的导水性能。过去利用水位观察资料或抽水试验资料计算水文地质参数的方法,只能适用于简单的含水体系,由于高度复杂的地质体并且间隙水流为非线性的这类参数如何确定还没有解决,如果利用近期发展起来的有限单元法来反求参数是一种理想的选择,特别是与古典的伽勒金法结合起来,既可简化数学处理过程,并有利于解非线性流问题。古典的伽勒金法原来只能适用于简易的分析域,而且要求介质为均一,但与空间离散的有限单元法结合起来,还便于解非均质而且边界不规则的问题。     

在层状非均质含水层中完整潜水井涌水量计算的新方法——分层计算法

本文中所指的层状含水层是由几层透水性不同的岩层所组成的非均质含水层,而任何两个岩层的交界面都是水平的。计算在层状含水层中完整潜水井涌水量是水文地质计算中常遇到的问题。例如计算在层状含水层中作供水用的完整潜水井涌水量。又例如当用钻孔进行设在层状岩层上的建筑场地疏干时,为了决定所需钻孔数目和其分布位置必须事先精确地计算每     

综合指数法在河流相储层非均质性研究中的应用

在储层建筑结构划分、测井多参数处理结果的基础上,根据熵的原理,应用熵权法定量计算了胜坨油田二区沙河街组二段3砂层组4小层（简称沙二段34）河流相储层的非均质综合指数,按照不同的开发时期详尽分析了储层的层间、层内、平面非均质性特征,并阐述了储层非均质性的主要影响因素,结果表明：沙二段34储层层内、层间及平面非均质性中等—较强,随着注水开发的进行,非均质性有继续增强的趋势,平面非均质性较之层内和层间非均质性要更强烈一些。同一小层及韵律层在不同开发时期的非均质程度有明显的差异。建筑结构控制储层非均质程度,成岩作用使非均质性复杂化,注采井网不完善加剧了非均质性的差异性。研究成果为剩余油挖潜提供了一种可行方法。     

双变法测验折光率的回顾及变温盒的设计

引言透明矿物有均质体与非均质体之分,测验矿物的折光率是鉴定矿物的一种重要标准。均质体矿物有玻璃质和等轴系晶体,只有一个折光率,不随视察的方向不同而发生变异。非均质体矿物有一轴晶和二轴晶。一轴晶矿物如正方系、六方系,有两个折光率,一个平行于 C 轴,称为ε。     

倾斜的隔水层上潜水运动的计算的新方法

在倾斜的平面状的隔水层上的均质的土中流动着的潜水或不承压水,它的流量的计算方法有多种多样。这反映了这个命题,在生产实践上,具有相当大的意义。例如计算水库的渗漏时,如果库岸的地层是倾斜的,那末就需要运用这些方法。     

潜水蒸发系数分析

潜水蒸发系数是潜水蒸发量与水面蒸发量的比值,是水资源评价估算中常用的参数之一。在缺乏实测潜水蒸发量资料的地区,可利用潜水蒸发系数计算潜水蒸发量,但潜水蒸发系数的地区差异性较大,现根据收集到的国内各地潜水蒸发资料,进行初步分析。     

X-射线粉末图测低对称造岩矿物晶胞参数的计算方法

用X-射线粉末图计算低对称晶胞参数的方法,自六十年代中期以后,国外已有所进展。1963-1973年间所逐步完善的美国的9214程序,就可作为这一进展的标志。但其语言均未见公开发表,尚难普遍借鉴。另一方面,据有关文献所透露的计算方法看来,它们也还并未能达到完善的程度,有些问题还有待进一步探索。     

塔里木河中游沿岸地区的水文地质条件及生荒地的开垦

概况根据初步的估计,塔里木河中游沿岸地区有几百万亩可以开垦的生荒地,在第二及第三个五年计划期间内将在这里建立国营农场群。数年之后,这里将成为新疆主要的植棉基地之一。为了给垦荒工作提供科学论据,近两年来,新疆水利厅阿克苏河流域规划勘测队及新疆生产建设兵团勘测队,正逐步地对冲积层中的表层潜水进行调查。     

均质潜水含水层抽、灌水实验测求参数的对比

本文设计了在室内均质潜水含水层抽、灌地下水的实验，对实验准备工作和实验过程进行了规划，使用观测的实验数据分别对水文地质参数进行了对比计算和规律分析。最后对实施人工回灌的具体工作进行了归纳总结。     

对《二元混合体系的端元Sm-Nd模式年龄计算方法》的商榷

Nd模式年龄的地质解释有多解性(Arndt et al 1987s Jahn et al., 1990),杨晓松等(1993)在《二元混合体系的端元Sm-Nd模式年龄计算方法》一文(下简称杨文)中提出端元模式年龄的概念和计算方法,试图解决模式年龄的多解性问题.公式推导基本正确,但在公式的内涵、适用性和应用条件等方面尚存在一些值得商榷之处。     

多尺度有限单元法求解非均质多孔介质中的三维地下水流问题

应用多尺度有限单元法模拟非均质多孔介质中的三维地下水流问题。与传统有限单元法相比，多尺度有限单元法的基函数具有能反映单元内参数变化的优点，所以这种方法能在大尺度上抓住解的小尺度特征获得较精确的解。在介绍多尺度有限单元法求解非均质多孔介质中三维地下水流问题的基本原理之后，对参数水平方向渐变垂直方向突变的非均质多孔介质中的三维地下水流和Borden实验场的三维地下水流分别用多尺度有限单元法和传统等参有限单元法进行了计算，结果表明在模拟高度非均质多孔介质中的三维地下水流问题时，多尺度有限单元法比传统有限单元法有效，既节省计算量又有较高的精度；在模拟非均质性弱的多孔介质中的三维地下水流问题时，多尺度有限单元法虽然也能在大尺度上获得较为精确的解，但效果不明显。     

有限单元法在地质力学中的应用

地质构造体和岩体是一种岩性和结构高度变化的非连续而且非均一的介质,在压力(包括岩体中的间隙水压力)和温度的作用下所产生的变形和破坏现象,不仅为非线性关系,并随空间和时间而变化。对某一点而言,这种关系会由于作用力的大小和时间的长短,由弹性过渡到塑性或粘性状态。对整体而言,在同一时间内,却会在不同的部位出现不同的应力状态和变形的程度。     

A hybrid approach to flow net generation

By following a simple set of rules, a flow net can be manually constructed to obtain a graphical solution to the Laplace equation for simple two‐dimensional (2‐D) flow problems. With the advent of numerical solutions such as the finite difference and finite element methods, it is more common to generate a flow net automatically using the nodal head and flow values output by the computer program. Two methods have been published for automatically generating flow nets from finite element solutions: the stream‐function method and the particle‐tracking method. The stream‐function method works well for many cases, but it does not work for problems with holes in the mesh or internal sources or sinks. The particle‐tracking method works for all cases, but previously published algorithms that utilize this method do not result in the properly sized flow channels. A new approach is presented in this paper that is a hybrid of the stream‐function and particle‐tracking approaches. This method works for all cases and generates the properly sized flow channels. Copyright © 2001 John Wiley & Sons, Ltd.     

Symmetric tangential stiffness formulation for non-associated plasticity

A numerical scheme is proposed in which the response of a material with non-associated flow rule is made equivalent to that of a material with associated flow rule and a modified stress/strain direction dependent hardening/softening rule. The scheme has obvious computational advantage since finite element programs with tangential stiffness formulations can be used without resort to non-symmetric equation solution routines.     

Numerical modelling of large deformations associated with driving of open‐ended piles

This paper presents a ‘Eulerian‐like’ finite element technique to simulate the large accumulated displacements of piles subjected to multiple hammer blows. For each hammer blow, results are obtained using a standard small strain finite element model and, at the end of each hammer blow, material flow is taken into account with reference to a fixed finite element mesh. Residual stresses calculated at the Gauss integration points of the deformed finite element mesh are mapped on to the fixed finite element mesh, and these stresses are used as initial stresses for the next hammer blow. At the end of each hammer blow, stiffness and mass matrices are recalculated for the volume of material remaining inside the fixed finite element mesh. Results obtained with and without allowing material to flow through the fixed mesh are compared for several hammer blows. Build up of residual stresses, soil flow and yielded points around the pile are presented for plugged, partially‐plugged and unplugged piles. Using the new finite element technique, the driving of a pile from the soil surface is studied. The ability to analyse this and other large deformation problems is the main advantage of the new finite element technique. Copyright © 2000 John Wiley & Sons, Ltd.     

Analysis of cylindrical cavity expansion in a strain weakening material

A numerical technique is suggested that allows a prediction of the behaviour of a single phase, strain softening material during the expansion of a long cylindrical cavity. The method provides the entire pressure-expansion relationship, including the identification of the limit pressure at large deformations.The numerical solutions, obtained using the finite element technique and allowing for finite deformations, show very good agreement with closed form answers that are available for a restricted class of material models. Results are also presented for the more general, dilatant (or collapsing), strain softening materials for which closed form solutions do not exist. The importance of the rate of dilation and rate of softening in determining the behaviour during cavity expansion is illustrated.     

油藏多相渗流的面向对象有限元程序设计

近年来,面向对象的编程技术越来越受到人们的重视,并用来解决和模拟各种物理问题和工程问题,特别是在有限元方法编程和模拟中得到了广泛地应用。介绍了面向对象的程序设计方法和它与有限元程序相结合的原理和优点。在此基础上提出了面向对象有限元方法在油藏多相渗流中的应用实例,并按照面向对象的程序设计方法,基于Windows XP平台采用Visual C++.NET语言,建立了有关描述多相渗流的有限元模型的类,给出了类的描述和它的实现方法。建立的相关类及其实现方法主要包括处理矩阵计算的类、节点类、单元类、材料类、形函数类等。据此编制了油藏多相渗流的有限元分析的数值计算程序,并给出了一个数值实例。     

The effect of pore-fluid compressibility on failure loads in elasto-plastic soil

The influence of pore-fluid compressibility on failure loads in certain soil mechanics problems is investigated. The results are tested using a finite element approach treating the soil as an elasto-plastic material. A limiting value for the pore-fluid compressibility to give satisfactory solutions and numerical stability is suggested.     

Slipping strip analysis of reinforced earth

Reinforced earth in plane strain is idealized as a homogeneous material with the strips attached to the elastic soil matirx by a conceptual shear zone. A ‘no-slip’ finite element model is derived by assigning a large shear modulus to the shear zone. Relaxation of this modulus using a tangential stiffness algorithm in conjunction with a Mohr–Coulomb strip-slip criterion allows slipping to be simulated. The finite element formulation is validated and the finite element discretization assessed by comparisons against exact solutions for a simple test problem. An idealized reinforced earth wall example is used to demonstrate the feasibility of the method and to answer the question: ‘is slipping significant?’ The method is shown to be potentially useful, and slipping is shown to be significant.