ISSN: 1945-7545
CODEN: GTJODJ
Published Online: 14 May 2003
Page Count: 7

An Evaluation of Geometric Factors Used in the Two-Stage Borehole Test (ASTM D6391-99) Using the Finite Element Method

Ratnam, S
Research Student, Cambridge University Engineering Department, Cambridge,

Soga, K
Senior Lecturer, Cambridge University Engineering Department, Cambridge,

(Received 25 May 2001; accepted 28 June 2002)

Abstract

Geometric or shape factors are constants used in the interpretation of in-situ hydraulic conductivity tests, such as the Two-Stage Borehole (TSB) test in ASTM D6391-99. The finite boundary condition shape factors used with the TSB test are an extension of those derived by Hvorslev (1951) for infinite boundary conditions. The accuracy of this extrapolation is investigated here, using the finite element method (FEM) as a tool for deriving shape factors for finite boundary conditions. The utilized FEM has been validated against closed-form solutions for other test geometries. The resulting errors from the incorrect use of shape factors with the TSB test are discussed, and new shape factors derived from the FEM are presented in the form of a chart.

Keywords:
two-stage borehole test, shape factor, finite element method, in situ testing, hydraulic conductivity, clays, Hvorslev, permeability, geometric factor

Paper ID: GTJ11323J
DOI: 10.1520/GTJ11323J
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