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The radial jacking test consists of applying a radial pressure to the surface of a short length of tunnel and then measuring the resulting displacements that occur within the rock mass. These measured values are used to determine a load-displacement relationship suitable for the design of important structures. The method presented for obtaining this relationship is based on solving for stresses and displacements in an infinite elastic body which contains a circular hole loaded radially along a finite portion of its length. The solution is used to obtain data for a curve which can then be used to determine the deformation moduli indicated by a radial jacking test. Studies conducted indicate that small errors in determining Poisson's ratio do not seriously affect moduli calculations and that the optimum ratio of loaded length to diameter of opening is approximately unity. Curves are also presented which indicate how moduli calculations should be modified if tangential tensile stresses resulting from radial loads produce radial cracking in the material immediately around the tunnel.
rock mechanics, foundation investigation, dam foundations, design data, deformation modulus, data analysis
Research structural engineerPersonal member ASTM, Bureau of Reclamation, Denver, Colo.