Abstract:With the improved system from deep plate-bearing test,26 in-situ static load tests are performed on the strong weathered soft rock,medium weathered soft rock and slight weathered soft rock in typical eight fields of Yueyang region,Hunan Province. The curves of p-s,s-lgp and lgp-lgs were drawn as follows:(1) All settlements curves of foundation change with static load laxly,and the limit loads of proportion are not obvious. However,the second inflection point of s-lgp curve is more obvious,which can be used to determine the ultimate bearing capacity of soft rock foundation. (2) The ultimate bearing capacity of strong weathered soft-rock foundation is smaller and more discrete than the others and the corresponding maximum settlement is greater and more discrete. But it is just opposite for the medium weathered soft-rock foundation and is a favorable bearing stratum for pile foundation. (3) All rebounded deformations when unloading are smaller,which indicate that the elastic deformation stage of soft slate rock foundation is considerably short under loading;and the nonlinear elastoplasticity is notable at the beginning of deformation. So the constitutive relationship of nonlinear elastoplasticity is more suitable for theoretical calculation or numerical simulation of soft slate rock foundation. Experimental results show that the bearing capacity of medium weathered soft slate foundation from uniaxial compression strength of rock is much smaller than that from in-situ test. According to present codes,the suggestion value of reduction coefficient is put forward.