Abstract:Cretaceous argillaceous siltstone in Changsha district is a kind of soft rock with the features of weak diagenetic process,and it is suspcetible to weathering and can be easily disintegrated. The potential bearing capacity of this rock is relatively higher,having softing coefficient less than 0.75 with low pore rate,water absorptivity,and inferior crack connection. Testing study is made on the basic mechanical property of this rock,which includes uniaxial compression,loading test and high pressure pressurementer test(PMT). Through the testing and analysis,it is found that the bearing capacity evaluated with “Code for Design of Building Foundation”(GB50007–2002) is lower than actual one. The problem—how to determine the total resistance of embedded section of argillaceous siltstone with various testing methods and different codes has been discussed. Determining the bearing capacity design value of rock,using the uniaxial compressive strength standard value under natural moisture,the coefficient of exertion is varied with different embedded depth-diameter ratios(hr/d). An improved formula is given to calculate the total resistence of embedded section. The study results which comparatively agree with the practice is instructive for design and further study.