INFLUENCE OF STRESS-DEPENDENT ELASTIC-MODULI ON STRESSES AND STRAINS AROUND AXISYMMETRIC BOREHOLES

Porous or clastic rocks often have elastic moduli which are not constant but increase with increasing minor principal stress. To illustrate these effects, solutions are developed for axisymmetric excavations in infinite media having power law and exponential variations of elastic modulus with minor principal stress. The maximum stress concentrations do not occur at the excavation boundaries and are less than the constant value of 2.0 given by constant modulus elasticity. When modified slightly to allow for test boundary conditions, the theory gives predictions that are consistent with aspects of the results obtained in hydrostatic compression tests on thick walled cylinders of three sedimentary rocks.