Study On The Characteristics Of The Beiguo Loess Landslide And Its Reactivated Causes In Heyang County

The reactivated landslides in the loess tableland area has caused a continuous retreat of the loess tableland surface and a reduction in the arable land area,as well as a serious threat to the lives and property of the local people.This paper selects the Beiguo landslide in Heyang County,which is a relatively active landslide on the loess tableland,as the subject,and combines the methods of physical geography and geology to study landslides.Through historical image data and unmanned aerial vehicle field surveys,the field reformed dynamic cone penetration experiments have conducted research on the temporal and spatial characteristics of landslides and soil characteristics;the main inducing factor of landslides is rainfall,and numerical simulation analyzes the stability of landslides in different rainfall scenarios.The results show:(1)The loess of the Beiguo landslide is mainly coarse silt,with extremely low content of cohesive soil particles,low degree of cementation between the loess particles,poor firmness,and the structure of the soil is easily damaged,prone to landslides or collapses.The experiment of reformed dynamic cone penetration shows that the deep undisturbed loess at the top of the tableland has good homogeneity;The degree of compaction of loess in the erosion gully from the top of the erosion gully to the bottom of the erosion gully after the erosion of the landslide shows a decreasing trend,which shows that the erosion of the ditch bottom at the back of the landslide is more damaged by erosion This corresponds to the feature that the swallow hole in the erosion gully are more densely distributed in the middle and lower part of the erosion gully;The new landslide body shows a trend of increasing loess degree of compaction from the top of the slope to the foot of the slope,indicating that there is a disturbance after the loess slides on the edge of the tableland.The degree of compaction is more serious in the lower part of the new landslide,and the degree of compaction of loess is larger.There is stretching of the loess in the upper part of the new landslide,and the degree of compaction of the loess is smaller.(2)The resurrection of the Beiguo landslide did not happen suddenly,but the unstable area inside the old landslide gradually developed slowly,and it continued to develop and accumulate in the early stage;at the same time,it also shows that the resurrection of landslide is conducive to the landscape remodeling phenomenon that the slope changes from instability to regional stability.The analysis of topographic features before and after the resurrection of the landslide shows that the erosion area and the accumulation area caused by the new landslide are basically the same,but the erosion volume is 1.44 times the accumulation volume.This difference is mainly caused by the excavation and transportation of the slope toe.Leveling and rebuilding the lotus pond will restore the original land,but it also brings huge safety hazards to the stability of the slope.(3)The analysis of factors that may induce landslide resurgence revealed that the sudden increase in rainfall in 2017 was the main triggering factor for landslide triggering.Based on indoor experiments,numerical stability simulations of the Beiguo landslide under different rainfall scenarios were conducted.Under different rainfall intensity scenarios,the overall pore water pressure in the landslide body gradually increases with increasing rainfall intensity,and the strength-discounted stability analysis of the slope shows that the maximum equivalent plastic strain value at the time of landslide instability also gradually increases,while the safety factor of the landslide body gradually decreases.Under different rainfall time scenarios,with the continuation of rainfall time,the infiltration of rainwater makes the soil saturated,and the overall pore water pressure in the landslide body gradually becomes larger.The analysis of the strength reduction stability of the slope shows that the equivalent plastic strain gradually increases,and the foot of the landslide on the loess side first yields,and then develops into a plastic channel upwards in the direction of the slope face,while the safety factor of the landslide body gradually becomes smaller.