| Tongren was affected by continuous severe convective weather and heavy rain,and several catastrophic landslides occurred in the area,In 2022.The most typical example is the catastrophic landslide in Songtao,Guizhou Province on June 3,2022.Previous studies believe that heavy rainfall is an important factor to induce landslides,which usually induces a large number of shallow soil landslides.Theoretically,it is difficult to accurately explain the formation of deep soil landslides.The investigation shows that Xiangshuidong landslide is a typical deep soil landslide,the starting area is located in the front of landslide,and has typical zoning characteristics.Based on the detailed field investigation of Xiangshuidong landslide,this paper systematically studies the deformation and failure characteristics and mechanism of landslide by means of engineering geological analogy,theoretical calculation,physical model test and numerical simulation.The results of the paper are as follows:(1)Xiangshuidong landslide developed on stepped slope.The sliding body is mainly composed of strong weathered gravel layer with relatively high clay content.The slippage bed is silty mudstone where the slippage zone in the overlying stratum.The average thickness of landslide accumulation body is about 6.5m,the landslide area is about 16621m~2,and the landslide volume is about 6.6×10~4m~3.(2)Xiangshuidong landslide has multi-stage zonal deformation and failure.Xiangshuidong landslide can be divided into four failure zones:the starting zone of landslide front(Ⅰzone),the failure type is swelling failure;Traction failure zone(zoneⅡ,zoneⅢ,zoneⅣ),the failure form is plunge failure.(3)The direct inducement factor of landslide is groundwater.The original dual structure of rock and soil provides basic conditions for the formation of landslides,and highway catchment and drainage of irrigation channels are induced conditions for the formation of landslides.The special rock and soil mass structure affects the seepage direction of groundwater.Continuous heavy rainfall,road catchment and drainage of irrigation channels increased the slope groundwater seepage.The seepage flow of groundwater into the landslide area increases,and the drainage capacity of groundwater in the front of the landslide area is limited.As a result,groundwater accumulates in the front slope of the landslide area,which eventually leads to collapse and failure at the foot of the front slope of the landslide area.After the collapse,the water pressure dissipates quickly and a free surface is formed.Subsequently,the deformation and failure areasⅡ,ⅢandⅣof the landslide were destroyed to the open surface successively under the action of traction,forming the Xiangshuidong landslide.(4)Through physical model phenomenon test and Comsol three-dimensional numerical simulation software,the process of groundwater action on slope was quantitatively evaluated,and the"conceptual model"of formation mechanism of Xiangshuidong landslide was further verified.Darcy’s seepage calculation,strength reduction calculation and groundwater pressure calculation verify the sequence of landslide failure under the action of groundwater:the through plastic zone appears first in the landslide front and the failure occurs first,followed by the failure zone of landslideⅡ,landslideⅢ,and the last failure zone of landslideⅣ.Based on excavation calculation,it is verified that the key to the instability of rock mass in the middle and rear of traction is the formation of frontage and the rapid decline of pore water and pore water pressure.(5)Under the action of recharge groundwater,the slopes with special dual structure usually form large deep soil landslides.Underground water forms"underground DAMS"inside the slopes.Under the influence of"dam"effect,this kind of landslide has the characteristics of leading-edge swelling failure,trailing edge falling failure and middle drift failure.The landslide scale is obviously controlled by the dominant seepage channel of groundwater,and the landslide may have the characteristics of zonal failure due to the change of seepage direction of groundwater.(6)Based on the consolidation of deformation and failure characteristics of Xiangshuidong landslide and the stability evaluation,the identification criterion of similar landslide and the calculation method of similar landslide stability evaluation are obtained.The identification of similar landslide should be analyzed against the background of groundwater recharge,diameter and discharge.Among them,it is necessary to focus on whether the slope has groundwater pressure conditions.The effect of groundwater uplift pressure on slope should be fully considered in stability calculation. |
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