中文摘要：

在真三轴应力状态下建立了岩土材料内摩擦角与中主应力系数的函数关系，通过与砾石料、Q2黄土和SantaMonicaBeach砂的真三轴试验结果对比，探讨了基于DruckerPrager（D—P）系列屈服准则的内摩擦角与中主应力系数的关系。以及D—P系列屈服准则的适用性．结果表明：当中主应力系数取特定值时，D—P系列屈服准则中内摩擦角的理论值与试验值相等；在不同应力状态下，岩土材料应选用合适的DP系列屈服准则，以使内摩擦角的理论值与试验值基本吻合．

英文摘要：

The mathematical expressions of internal friction angle considering the influence of intermediate principal stress under true triaxial stress were deduced. After a comparison of the results of the true triaxi- al tests of gravel, Q2 loess and Santa Monica Beach sand, the relationships between internal friction angle and intermediate principal stress coefficient were studied based on DP yield criteria. The results show that the calculated values of internal friction angle with D-P yield criteria equal the testing results when the intermediate principal stress coefficient is suitable for the corresponding criterion. In order to obtain reasonable results, appropriate D-P yield criteria should be chosen for different materials.