Based on the fast shear test of the invaded and natural collapsible loess, the shear strength of the invaded collapsible loess was significantly lower than that of the natural collapsible loess,and the variation laws of the shear strength was related to the soil type. For the silty collapsible loess under the invaded and natural states, the variations of the shear strength were similar with different pressures,and the variation of the shear strength was mainly due to the reduction of the cohesive strength, which can be up 92%. Furthermore,the variations of the shear strength were divided into two stages based on the variations of pressures: the rapid change stage and slow change stage. According to different levels of collapsibility of the loess, the initial pressures for the rapid change were also different. The variation of the internal friction angle decreased with the decreasing of the coefficient of collapsibility,whereas the cohesive strength was related to the collapsible degree and the compressive coefficient of the soil sample.%通过侵水前后湿陷性黄土的快剪试验,发现侵水后土样的抗剪强度明显低于天然状态下土样的抗剪强度,且抗剪强度的变化规律与土的类别有关.粉土类湿陷性黄土侵水前后的抗剪强度在各级压力下变幅相当,并且抗剪强度的变化主要表现在黏聚力的降低上,降幅达92％；侵水前后粉质黏土类湿陷性黄土的抗剪强度变化随压力变化分为快速变化和缓慢变化两个阶段,根据土的湿陷程度不同抗剪强度发生快速变化的起始压力也不同,其中内摩擦角的变化随湿陷系数的降低而减小,黏聚力的变幅与土的湿陷程度以及压缩系数有关.
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