THE INFLUENCE OF TEST PLATE FLEXIBILITY ON THE RESULTS OF CABLE JACKING TESTS

Plate loading tests which use surficial loading of a rock mass are employed quite extensively for the determination of in situ deformability characteristics of rock masses. The cable jacking method is essentially a surficial plate load test in which the test load is provided by reaction against a cable anchored at some depth below the rock surface. The results of the test are usually evaluated within the framework of the classical theory of elasticity to generate estimates for the bulk deformability properties of the rock mass. In the conventional evaluation of this test it is assumed that the test plate is rigid and that the embedded anchor load has no influence on the test plate settlement. The purpose of this paper is to examine the possible influences of the plate flexibility and the anchor load location on the effective settlement of the test plate. The variational estimates presented in the paper are valid for moderately flexible test plates which are characterized by a relative rigidity parameter. Numerical results are developed in the form of correction factors that should be applied to the cable jacking results to arrive at the deformability characteristics of the tested rock mass. For the covering abstract of the symposium see TRIS 452576. (Author/TRRL)