Study On The Formation Mechanism Of Loess Landslide Induced By Irrigation

Loess is widely distributed in China.In recent years,with the intensification of human engineering activities such as diversion and irrigation,coupled with the water sensitivity of the loess,the mechanical properties of the soil have been significantly reduced after encountering water.Irrigation-induced landslides have become one of the main factors that cause the instability of the loess slopes in addition to natural factors such as rainfall and earthquakes,which poses a huge threat to the normal life and safety of local residents.Therefore,accurately revealing the formation mechanism of this type of landslide is of great significance to the carry out of disaster prevention and mitigation work and the maintenance of social development and stability.In this paper,based on the field survey of Heifangtai and the collection of related data,taking Luojiapo landslide in Dangchuan Village as an example,by sampling the undisturbed loess buried in the back wall of the landslide at the depth of 5m,10 m and 18 m behind the landslide and conducting indoor tests.The relevant physical and mechanical properties of the soil are obtained,and then the Geo-Studio simulation software is used to simulate the changes of the internal seepage field and slope stability of the Luojiapo landslide under irrigation conditions.Finally,combining the results of field investigations,laboratory tests and numerical simulations,the formation mechanism of loess landslide under irrigation conditions was revealed.The main research results are as follows:(1)Based on the field investigation and the collection of relevant data,the topography,stratum lithology,geological structure and other environmental geological conditions of the study area and the deformation and destruction characteristics of the landslide were obtained.(2)By carrying out conventional physical and mechanical properties tests,triaxial shear tests and ring shear tests on loess with different sampling depths,the changes in physical and mechanical properties of loess under different water content,different sampling depths and different shear rates were obtained.(3)Through numerical simulation,the stability coefficient of the slope decreases continuously with the increase of irrigation time.At the same time,because the slope surface matrix near the shoulder of the slope has the largest suction,a "negative pore water pressure ring" is formed inside the soil.With the increase of irrigation time,the "negative pore water pressure ring" is constantly approaching the slope surface,and the saturated soil near the slope foot continues to increase.(4)Combining the results of field investigation,laboratory test data and numerical simulation results,the formation mechanism of loess landslides under irrigation conditions is as follows: The effect of irrigation water increases the internal weight load of the soil body and reduces its strength.At the same time,the material migration caused by irrigation infiltration makes the strength of the lower soil body more affected by the water content,making the original joint cracks in the loess continue to expand.In addition,The seepage force generated by the infiltration of irrigation water pointing out of the slope exacerbates the deformation development process of the slope.When the anti-sliding force of the slope is less than the sliding force,the discontinuous potential fracture surface will develop into a continuous failure surface,resulting in a landslide The destruction occurred.