High pressure K₀ creep experiment and the anisotropy of microstructure of deep buried clay

The high pressure creep equipment was designed to study the horizontal ground stress of shaft lining in Juye mine area of Shandong province where the thickness of alluvium was nearly 700 m.The maximum consolidation pressure of the equipment could exceed 20 MPa.Six undisturbed clay samples taken from depth of 300～600 m in Juye coal field were used in K0 consolidation tests.The consolidation pressures were 6,8,10,12,14,16 MPa in these tests.The coefficients of lateral pressure K0 of the samples were obtained and the variation of K0 with depths were analyzed.The SEM tests of one clay sample under different consolidation pressure were performed and the microstructure was scanned.The variation of anisotropy of microstructure was analyzed with computer image analysis.It was shown that the anisotropy of microstructure of clay increased obviously with the increase of depth and consolidation pressure.The essential reasons of the macro variation of coefficients of lateral pressure K0 in consolidation tests were analyzed based on the microstructure characteristics.