From in situ stress and discontinuities to the strength of granites: comparison and case study

摘要

The distinctive weathering profile and discontinuity of granites, dipping slightly at shallow depths and steeply in larger depths, are regarded as being due to their physical and geo-mechanical properties. This paper compares vertical stress (Sv) and overlain weight (γh) drawn from different kinds of in situ stress measurements, as well as coefficients of lateral stress. Stress trends are connected with discontinuities (joints and dykes), which reveal their relationships in space and dip angles of joints and dykes are compared in space, together with shear plane plunges and the strength of rocks from laboratory tests. As a result, it was found that the relict structural geostress contributes to maximum horizontal stress, especially at shallow depths. The most common feature is the high coefficient of lateral stress, which is mostly attributed to unloading in shallow depths and stress concentration at a certain depth after the erosion of overlain beds and the exposure of granites at the ground surface. Therefore, the weathering profiles and weathered capsule of granites could be interpreted from this viewpoint. One of the two main features of this paper is the connection of the extraordinary values of the lateral coefficient of in situ stress with unloading and the typical weathering profile at shallow depths. Another is the comparison of the shear stress and strength from in situ and laboratory tests, with a series of data from the same location and depth.