黄土崩塌是延安地区较严重和常见的一种地质灾害，大量的现场调查和理论研究表明，降雨作用是延安地区黄土崩塌形成的主要因素之一。 本文以降雨作用下延安地区黄土崩塌形成的机理为主要研究内容。通过调查延安宝塔区典型黄土崩塌点，分析了延安地区黄土崩塌形成的主要影响因素；借助干湿循环作用下黄土的劣化试验，分析了干湿循环作用对黄土抗剪强度的影响和对黄土节理裂隙的影响；依据饱和-非饱和入渗理论以及非饱和土的抗剪强度理论，分析了降雨作用对非饱和黄土抗剪强度的影响；根据拉裂-滑移式黄土崩塌隐患体的稳定性计算公式，分析了降雨作用以及干湿循环作用对其稳定性系数的影响；使用Geo-Slope软件，分析了不同的降雨时长和降雨强度对拉裂-滑移式黄土崩塌形成的影响，以及降雨作用下节理裂隙对拉裂-滑移式黄土崩塌形成的影响。 通过分析得出以下主要结论：延安地区黄土崩塌形成的内因主要包括：土体性质、黄土节理、坡体形态，外因主要包括：降雨作用、冻融作用、人类工程活动；干湿循环作用导致黄土的粘聚力和内摩擦角减小，土体内部节理裂隙扩展延伸，并最终导致土体抗剪强度降低；基质吸力对黄土边坡的稳定性有贡献作用，降雨会降低非饱和黄土的基质吸力和抗剪强度，使得坡体的稳定性降低；随着降雨时间和降雨强度的增加，拉裂-滑移式崩塌隐患体的稳定性系数逐渐减小；节理裂隙的存在使得雨水沿着裂隙进入黄土坡体，雨水的作用使得土体的抗剪强度不断降低，节理裂隙不断扩展延伸，随着裂隙沿着软弱面贯通，拉裂-滑移式崩塌随之发生。

Loess Collapse is the most common and dangerous geotechnical hazard in Yan’an Area.According to scientific research,the rainfall infiltration is the main factor which induces the loess collapse hazard. The main research content is the formation mechanism of loess collapse induced by rainfall.Through the investigation of the loess collapse slope in yan’an are,the main influence factors of the loess collapse were researched.Based on the dry-wet circle experiment,the variation law of shear strength and loess fissures influenced by dry-wet circle was researched.According to the saturated-unsaturated seepage theory and unsaturated soil shear strength theory,the influence law of loess strength and loess slope stability induced by rainfall was researched.By the stability coefficient calculation formula of loess collapse ,the influence law of stability coefficient was discussed.Based on the Geo-Slope Software analysis,the loess collapse mechanism influenced by the rainfall intensity was researched.Through the scientific research,this paper achieved the following results. The internal factor of the loess collapse are the loess property,jont fissure and slope form.The external factor of the loess collapse are the rainfall infiltration,freeze-thaw action and the human engineering activity.Under the action of dry-wet circle,the cohesion and internal friction angle of loess decrease.The infiltration mechanical action of rainfall will decrease the shear strength of loess.By the increase of rainfall intensity and rainfall capacity, the loess matric saction,shear strength and slope stability will decrease.For the action of loess fissures,the shear strength of loess decrease which lead to the occurrence of loess collapse.