Drained solution for cylindrical cavity expansion in modified Cam clay soil under constant vertical stress

Abstract

Cavity expansion is a fundamental theoretical problem in geomechanics. For the cylindrical cavity expansion problem, derivations of solutions are usually based on the assumption that the soil is subject to the plane strain condition. However, this is untrue for cavity expansion in pressuremeter tests. This study first derived the equilibrium equation for cylindrical cavity expansion under the constant vertical stress condition. Then, the equilibrium equation was solved for modified Cam clay soils with different overconsolidation ratios (OCRs). The solutions were compared with the responses in the same soils under the plane strain condition. It was found that the ratio of the limiting cavity pressure in the latter to that in the former ranged from 1.31 to 2.76 and increased with an increase in the OCR. Under the constant vertical stress condition, significant heaving occurred in the vicinity of the cavity, and volumetric strain evolved from contraction to dilation as the OCR increased. Significant differences were noted in the stress paths of the two different loading conditions. These results indicate that the assumption of the plane strain condition will lead to overestimation of the limiting cavity pressure and inaccurate prediction of the stress path in the pressuremeter test, especially for heavily overconsolidated soils.