INSITU STRESS MEASUREMENT BY A METHOD USING ORIENTED CORE

A borehole was drilled in granodiorite rockmass at Fangshan, Beijing, China. The depth of the borehole is 301m with diameter of 110mm. From about 30m to 301m, all cores were oriented by cement end cap method. AE Kaiser effect tests on oriented core at depth of 294m were carried out. The rock specimens are the cylinders with 30mm diameter and 75mm height. In vertical direction, the vertical stress estimated by AE Kaiser effect tests is 7.7 MPa. The lithostatic pressure at the depth of 294m in granodiorite rockmass is 7.9 MPa. Both of them are almost same. In horizontal plane, for four directions rock specimen, AE Kaiser effect tests were carried out and their corresponding normal stresses were gotten. The horizontal maximum and minimum principal stresses are 21.2 MPa and 12.1 MPa respectively. The orientation of horizontal maximum principal stress is about the NStrending. Comparing the result of AE Kaiser effect tests with hydrofracturing shows that they are consistent fundamentally.