| Loess and loess-like soils are widely distributed in China, and its total area isapproximately640,000m2. Loess landslides occur frequently. The Features such as largescale, strong harm, difficult to predict and control, threat seriously to the safety of people’slives and property, and limite the economic and social development in loess region. Inaddition, the soil erosion in Loess Plateau mainly occurs from June to September duringwhich it rains a lot. This causes severe damage to the loess slope, and even leads todeterioration of the soil and water environment, soil nutrient loss, and reducing landproductivity. The destructive effect of water infiltration caused by Rainfall on the slope isobvious, as same as the slope erosion. So, in order to protect the safety of people’s lives andproperty further, this paper will carry out Experimental study about the impact of rainfall, themain incentive, on loess landslides and slope erosion. In this article, an artificial rainfalldevice was designed as needed, and an indoor model of loess slope was established. The loessmaterial is taken from Yangling, Shaanxi. The occurrence and development of loesslandslides and the change of slope pattern were observed through comprehensive monitoringwith moisture sensors, stress sensors, tracer point and digital photography et al. The maincontents and conclusions of the test are as follows:（1） Moisture sensors within the slope give the real-time moisture content, and throughplexiglass the wetting front can be observed. The results show that, the water infiltration rateis becoming slow, and water infiltration rate at slope top is always larger than that at the slopesurface. And the ratio of runoff to infiltration first increased and then dropped to steady levelwith the changes of time. Moisture content within the slope begins to increase successivelyfrom top to bottom, its value tends to be stable, being saturation, when increasing to a certainlevel. The maximum volumetric moisture content is about41%~44%when landslidehappens.（2） The stress values in different position is measured by miniature pressure stress testsystem buried in the60°slope model. We can see, the stress at a position is related to itsdepth, and the stress increase as the depth increasing. The development of stress is related tothe time. When cumulative time t=400min~700min, the stress fluctuations are the largest.Therefore, the landslides may be formed in that period of time. （3）The deformation-monitoring is conducted by observing the movement of spikespots, red flags, cotton et al, and the slope surface variation,such as cracks, is observed andrecorded too. It could be found that there are two-direction displacement （down andforward） in the body of slops. The angle between direction of displacement under the top ofslope and vertical is about0°~10°, and maximum displacement is about10cm. The anglebetween direction of displacement under the surface of slope and vertical is about30°~60°,and maximum displacement is about15cm. The through tension crack produce firstly at thetop of slope in the process of rainfall, and further penetration of water, small vertical cracksproduce partly in inter of slope..（4）The digital cameras are used to record the deformation of whole slope and thesurface form. Taking the45°model test as example, the slope erosion experiences the processof “sheer erosion-gully erosion-deep and lateral erosion in the slope of ditch”, ultimately thelarge-scale rill erosion is shaped and the gully bank collapse. The slope surface glided overallis caused by the erosion. Due to the rainfalls, the degree of saturation was higher relatively atthe toe of slope, and the small slump develops from the bottom to top. The position of slumpmoves upwards, and the large-scale slump occurrs ultimately. |
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