为研究在降雨入渗条件下的膨胀岩（土）渠坡土-水相互作用机理及滑坡成因，在河南新乡南水北调中线工程潞王坟试验段裸坡试验区对不同坡比的 2 个膨胀岩渠坡进行人工降雨试验，试验中跟踪观测渠坡下渗强度、含水率、吸力及水平位移对降雨的响应规律。对观测成果进行分析后认为，在供水强度大于渠坡下渗能力的情况下，降雨强度及坡度对下渗强度没有影响；裂隙发育深度以内土层受降雨影响最为严重，其含水率在干湿循环过程中大幅波动；不论是陡坡还是缓坡，滞水层的存在均使浅层吸力大幅下降；水分入侵只是膨胀岩（土）渠坡滑动破坏的一个诱发因素，干湿循环所引起的裂隙发育与强度衰减才是其根本原因。

In order to study the soil-water interaction mechanism and the cause of landslide of a swelling rock slope under precipitation infiltration, an artificial rainfall test was conducted on two bare swelling rock slopes with different gradients in the Luwangfen test section of the Middle-route of the S-N Water Transfer Project, the responses of infiltration intensity, water content, suction and horizontal displacement of the slope to the rainfall were monitored. The study from the monitored data proves as follows ∶① The gradient of slope and the rain intensity have no influence to the infiltration intensity when the water supply intensity exceeds the infiltration ability of slope. ② In the slope, the soil stratum is affected most severely by rainfall inside the depth of fissures, where the water content fluctuates widely in the course of wetting and drying cycles. ③ The matric suction of the superficial layer will be greatly decreased owing to the existence of backwater zone. ④ The invasion of water is only one inducement of the failure of a gentle swelling rock slope, while the development of fissures and the weakening of the shearing strength caused by wetting and drying cycles is the essential cause.