摘要:

AbstractThere are many expressions proposed for the permeability of isotropic media based on flow channel and pore size distribution concepts, but there are no such expressions for anisotropic media. In this paper an expression for the permeability of an anisotropic medium is proposed, which has been verified in the laboratory.The mechanism behind fluid flow through soil was investigated using microscopic computer simulations to propose an expression for macroscopic permeability. The soil was assumed to be a spatially periodic porous medium, and the Navier‐Stokes equation was solved using the FEM with appropriate boundary conditions for several different arrangements of the porous medium. The basic variables influencing flow through soil at the microscopic level were identified as specific surface area, void ratio, particle shape, material heterogeneity and the arrangement of particles in a porous medium. A sensitivity analysis was carried out to obtain an expression for the permeability in terms of the above variables.The corresponding macroscopic variables for the above microscopic variables are average specific surface area, average void ratio, anisotropy, tortuosity due to material heterogeneity, and the arrangement of particles respectively. An expression for the directional permeability is proposed in terms of these variables for the most common occurrence of particles in a porous medium.For the verification of the proposed equation, the permeability values of a fine‐grained sand were measured at different void ratios and were compared with those predicted by the proposed equation. The results show that the predicted permeability values from the proposed equation are very close to the measured val

ISSN:0363-9061    

DOI:10.1002/nag.1610130602

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe paper is concerned with the solution and determination of the optimum shape of a retaining wall modelled by the co‐ordinates of a set of points which belongs to a certain permissible space.An optimum design method is formulated as a non‐linear multiobjective optimization problem. The following two objective functions, which are mutually conflicting and non‐commensurable with each other, are considered: (a) to minimize the total weight of the wall, (b) to maximize the structure stability.A set of Pareto optimum solutions is derived numerically by adopting a logical algorithm, and a Pereto optimum solution is obtained by investigating the trade‐off relationships among design obj

ISSN:0363-9061    

DOI:10.1002/nag.1610130603

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe problem of ill‐conditioning in anisotropic and heterogeneous flow regions using plane and axisymmetric conditions is studied. A new concept,conditioning ratio, which covers all the possible factors significantly affecting the problem of ill‐conditioning (e.g. aspect ratio, heterogeneity and anisotropy) is proposed. It has been shown that there is an upper limit for this conditioning ratio, beyond which the stiffness matrix of the modelled region will be ill‐conditioned. Using this limiting value and considering the fact that flow behaviour in a single fracture is, basically, independent of the value of permeability normal to the plane of the fracture,k1, a criterion is established to calculate the value ofk1for thin elements. By adopting this criterion the problem of ill‐conditioning could be avoided, regardless of the value of the aspect ratio. The reliability of the proposed criterion is examined by using thin elements with very large aspect ratio (up to 106) in modelling the pumping problem from a well fully intersecting a vertical fracture. The comparison of the numerical results with the available analytical solutions is found to be very satis

ISSN:0363-9061    

DOI:10.1002/nag.1610130604

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe stiffness characteristics of a packing of granules are influenced by the particle interactions at contacts, the void ratio, the co‐ordination number and the packing structure. A stress‐strain relationship for the packings of spheres is presented. The relationship explicitly includes the contact force‐displacement law and the parameters characterizing the packing structure. The initial moduli computed using this relationship are compared with experimental measurements and empirical equations for sands. The theoretical results are also compared with experimental results on packings of glass balls. Closed‐form solutions are derived for statistically isotropic packings under initial isotropic stress conditions. Numerical solutions for the stiffness properties are obtained for anisotropic initial stress conditions and anisotropic packing str

ISSN:0363-9061    

DOI:10.1002/nag.1610130605

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA boundary element approach for time harmonic axisymmetric problems using the complete space point load fundamental solution is presented. The fundamental solution is integrated numerically along the azimuthal co‐ordinate of each axisymmetric element. To increase the accuracy of the numerical integration a simple co‐ordinate transformation is proposed. The approach is applied to the computation of the dynamic stiffness functions of rigid circular foundations on layered viscoelastic soils. Three different sites are considered: a uniform half‐space, a soil layer on a half‐space, and a soil consisting of four horizontal layers and a compliant half‐space. The numerical results obtained by the proposed approach for surface circular foundations are very close to corresponding published results obtained by different p

ISSN:0363-9061    

DOI:10.1002/nag.1610130606

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThis paper presents the results of an investigation of the static earth pressure behind a gravity wall with dry cohesionless backfill. A comparison is made between the results of finite element analyses and those of several experimental studies on wall models. The results of the investigation indicate that current design methods do not account adequately for some parameters that may influence the magnitude and distribution of the earth pressure. The study shows also that the design of earth‐retaining structures should be based on the amount of displacement permitted in the structur

ISSN:0363-9061    

DOI:10.1002/nag.1610130607

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

ISSN:0363-9061    

DOI:10.1002/nag.1610130608

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

ISSN:0363-9061    

DOI:10.1002/nag.1610130609

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY

ISSN:0363-9061    

DOI:10.1002/nag.1610130601

出版商:John Wiley&Sons, Ltd    

年代:1989

数据来源: WILEY