针对南水北调工程膨胀岩，选取典型的河南新乡黏土岩，采用 GDS 非饱和直剪仪进行控制吸力条件下的非饱和直剪试验。试验结果表明：非饱和黏土岩的强度随着基质吸力的增加而增大，基质吸力对抗剪强度的贡献率随着净法向应力的增大而增加。黏土岩在剪切过程中存在着剪胀现象，由于原生裂隙、软弱面和铁锰氧化物胶结的影响，黏土岩的剪胀性随基质吸力而增加的规律性不明显。

The shear strength characteristics of a typical expansive rock taken out from Xinxiang City, Henan Province were studied by performing suction controlled direct shear tests using the GDS unsaturated direct shear test system. The test results show that the shear strength of the unsaturated clay rock increases with an increase of the matric suction. The contribution ratio of matric suction on the frictional resistance increases with an increase of the net normal stresses. Dilatancy of the clay rock was observed during the shear stage. Owing to the existence of primary fissures and weak surfaces and the cementation effect of the iron and manganese oxides, the rule between the dilatancy of the clay rock and the applied suction was not clearly.