THE INFLUENCE OF JOINT-PLANES ON THE MASS STRENGTH OF HONG-KONG SAPROLITIC SOILS

Saprolitic soils containing relict joint-planes are common throughout Hong Kong in areas of in situ weathering of granites and volcanic rock s. A series of shear box tests on both the joints and the matrix soil of saprolitic soils is reported. The results reaffirm that the shear s trength of the relict joints is much lower than that of the matrix soi l, though the difference may diminish as decomposition advances. Relic t joint-planes cannot therefore be ignored in assessing the mass stren gth for slope design in saprolitic soils, especially in the relatively less decomposed zones.