波浪导致的海床边坡稳定性分析

利用Biot二维固结理论,计算出波浪引起的海床应力场;在假设海床土体的粘聚力不受波浪作用影响的条件下,推导出了波浪导致弱粘性土或粉土海床失稳的破坏准则,丰富了波浪导致海床失稳的判别方法。并把这一破坏准则用于黄河三角洲埕岛油田海域的海床底坡稳定性分析,讨论了50年一遇和5年一遇两种海况条件下,土体粘聚力对该地区波浪导致海床破坏深度的影响,计算结果表明,土体粘聚力对海床稳定性影响明显。     

渗透破坏若干问题的解析解及机理分析

讨论了柱坐标下不同介质有限区域内用分离变量法求解Laplace 方程的问题。通过一系列计算试验,给出了柱坐标下Laplace 方程在不同介质有限区域内用分离变量方法求的解,并用该解对渗透破坏现象进行了讨论和实例验证。认为渗透系数分布不均匀是发生渗透破坏的根本原因,渗透破坏朝着渗透系数差异较大的方向发展,并对管涌的复杂机理进行了引申阐述。该工作对于流土、管涌机理的更深入研究具有重要的意义。     

基于严格平衡的安全系数统一求解格式

在边坡稳定性分析中宜采用严格极限平衡条分法,特别是对于任意形状滑动面。由于条间力假设的不同,产生了不同的边坡稳定安全系数求解格式,既造成计算及应用的不方便,又掩盖了各自方法的优劣。首次将现有严格极限平衡条分法对条间力的假定表示成统一形式,根据力和力矩的平衡,导出简单明了的条间力递推方程和条间力矩递推方程。根据这2个方程,通过Newton-Raphson法建立了传统意义下基于严格平衡的安全系数统一求解格式。所需有关导数均可用递推公式计算,其性质为解析解,因而计算格式具有良好的稳定性与收敛性。所有公式均为代数式,便于在工程中推广应用。     

考虑固结效应的溶质传输研究

传统的孔隙介质水动力学采用对流-扩散方程,研究溶质在流体中的迁移。在这个过程中,孔隙介质被认为是不变形的,因而是一个稳态问题。针对二维情况下孔隙介质变形对溶质传输的影响,给出了考虑孔隙介质固结效应的溶质传输方程,并且探讨了该类问题的求解方法。     

中国森林生态系统的植物碳贮量及其影响因子分析

利用中国第四次(1989~1993年)森林资源清查资料,指出中国森林植被的总碳贮量和碳密度分别为 3 778.1Tg(1Tg = 10¹² g)和41.321 Mg/hm²(1 Mg= 10⁶ g),其分布很不均衡,东北和西南各省的碳贮量和碳密度较大。中国森林碳贮量约占世界的1.1%,森林碳密度低于世界平均水平,但中国森林以中、幼龄林为主,占80%以上,表明中国森林植被具有巨大的固碳潜力,对全球碳循环具有重要作用。同时,采用多元线性回归模型、标准系数法定量分析了气候因子对森林植被碳贮量的影响程度,指出气温对森林植被碳贮量的贡献大于降水。     

加筋效应对群桩相互作用系数的影响

群桩相互作用系数通常是采用平面应变模型进行分析,其研究方法具有较多的近似性。基于更为严格的虚拟桩模型,应用群桩相互作用的积分方程解答,以两桩相互作用的基本模型为例,研究加筋效应对群桩相互作用的影响。与弹性理论法和Mylonakis & Gazetas解答的对比表明,加筋效应对群桩相互作用系数有着较为明显的影响,并指出Mylonakis & Gazetas基于剪切位移法所得解答中存在的一些主要问题。     

温度效应对盐岩力学特性影响的试验研究

对经历不同温度后盐岩的力学性能进行了试验研究,分析了盐岩应力-应变曲线、峰值应力、峰值应变、弹性模量等的变化情况。分析结果表明,温度对盐岩的物理力学特性影响较大,随着温度的升高,盐岩的力学性能劣化明显,峰值应力和弹性模量降低,峰值应变增加;峰值应力可以表示成围压与温度的函数,并从盐岩弹性模量随温度的变化规律入手,导出了热损伤演化方程和一维TM耦合损伤本构方程。     

填充沟屏障远场被动隔振三维分析

把填充沟看作存在于弹性半空间的异质体,运用瑞利波散射的积分方程,对填充沟连续屏障远场被动隔振进行了三维分析,详细讨论了影响隔振效果的几个主要参数。研究表明,刚性材料比柔性材料具有更好的隔振效果,在隔振设计时应选择刚性屏障材料;填充沟的深度在一倍瑞利波波长内对隔振效果有较大影响,并且与宽度一起决定其隔振效果,但当屏障深度超过一倍瑞利波波长后,屏障深度对隔振效果的影响很小。     

Integral equation solution for three-dimensional heat transfer in multiple-fracture enhanced geothermal reservoirs

For the prediction of energy production from multiple-fractured geothermal reservoirs, previous models basically focused on the one-dimensional conduction in the rock containing evenly distributed fractures of equal scale. Here, a novel model is described to numerically investigate the three-dimensional heat transfer in geothermal reservoirs with unevenly spaced disc fractures of various sizes including the aperture and radius. In terms of the water flow through each fracture, an approximate analytical solution is obtained on the assumption that the water pressure disturbances, induced by the fracture margin and extraction (injection) operation, at the injection (extraction) well center and at different locations within the injection (extraction) well range were approximately equal. By the integral equation scheme for two-dimensional planar fractures, the three-dimensional problem of heat exchange is simulated without the reservoir discretization. The singular integral is analytically calculated in polar coordinates whereas the nonsingular integrand is numerically estimated by the Gaussian quadrature method in Cartesian coordinates. Compared with the one-dimensional simplification, the three-dimensional heat conduction remarkably alters the prediction of extraction temperature. In addition, the reservoir temperature field is also significantly influenced by the spacings and dimensions of fractures. The present model may be used for the estimation, design, and optimization of a geothermal reservoir.     

Axisymmetric interaction of a rigid disc with a transversely isotropic half‐space

A theoretical formulation is presented for the determination of the interaction of a vertically loaded disc embedded in a transversely isotropic half‐space. By means of a complete representation using a displacement potential, it is shown that the governing equations of motion for this class of problems can be uncoupled into a fourth‐order partial differential equation. With the aid of Hankel transforms, a relaxed treatment of the mixed‐boundary value problem is formulated as dual integral equations, which, in turn, are reduced to a Fredholm equation of the second kind. In addition to furnishing a unified view of existing solutions for zero and infinite embedments, the present treatment reveals a severe boundary‐layer phenomenon, which is apt to be of interest to this class of problems in general. The present solutions are analytically in exact agreement with the existing solutions for a half‐space with isotropic material properties. To confirm the accuracy of the numerical evaluation of the integrals involved, numerical results are included for cases of different degrees of the material anisotropy and compared with existing solutions. Further numerical examples are also presented to elucidate the influence of the degree of the material anisotropy on the response. Copyright © 2009 John Wiley & Sons, Ltd.