Rainfall-loess Slope Hydrological Response Process Based On Distributed Monitoring

Water is the most active factor inducing loess landslide.It is the key to study the mechanism and establish early warning models of loess landslides to capture the information of soil moisture changes through monitoring,and to grasp the hydrological response process and migration laws of loess slopes.This paper relies on the National Key Research Planning Program(SQ2018YFC150072);Project of China Geological Survey(DD20189270)and the Loess Disaster Field Scientific Monitoring Station of the Ministry of Natural Resources,,carried out the distributed monitoring of the moisture field of the loess slope,explored the hydrological response law and seepage mechanism of the loess slope under the rainfall,and constructed the moisture spatial prediction models of different slope types and gradients.The main results are as follows:1.Constructed a distributed monitoring system for the moisture field of the loess slope.The monitoring objects was selected from the perspective of geometric controlling factors such as slope shape,gradient,height,etc;at the same time,in order to continuously and finely capture the response process of the loess slope moisture field to rainfall,a distributed monitoring system is selected and designed with a combination of high-density Electrical Resistance Tomography(ERT),Distributed Temperature Sensing(TDS),and TDR sensor network.3.Established the conversion relationship between physical properties and moisture content.The conversion relationship between the resistivity and moisture content,temperature and moisture content of loess was established through laboratory experiments and in-situ calibration and fitting.The calculated value is compared and analyzed with the measured TDR data,and it is found that the dynamic change of the slope moisture field obtained based on the high-density Electrical Resistance Tomography is more in line with the actual situation.4.Reveal the response process and infiltration law of moisture on the loess slope to rainfall.Based on the analysis of the electrical method profile and the water content profile obtained by the Electrical Resistance Tomography,during the short-term heavy rainfall period,the water infiltration mainly affects the spatial distribution of the water content near the surface of the loess slope.The effective infiltration depth and water content have a small increase in value,and they mainly occur on relatively gentle slopes,which have minimal impact on the hydrological process of the slopes with larger slopes.Under the action of long-term low-intensity rainfall,although the initial water infiltration depth and hydrological effects are small,the water infiltrates continuously under continuous rainfall replenishment,and the water field of each part of the slope changes.It even has hydraulic connection with the deep part of the slope,which acts on the dominant channels such as ground fissures.5.Constructed a spatial prediction model of moisture with different slope types and gradients.Numerical models of loess slopes with different gradientss and slope types were established.The Hydrus-2D software was used to simulate and analyze the spatial distribution and seepage changes of convex slopes and linear slopes(gradients of 30°,40°,50°,60°)under different rainfall intensity.And the results obtained are consistent with the above-mentioned in-situ monitoring and analysis results by constructed the corresponding moisture spatial prediction model.