The Response Law Of Groundwater Dynamics To Fluctuation Of Reservoir Water Level In Complex Landslide Structures And Its Application

More than 100 large old landslides have been revived after impoundment in the Three Gorges Reservoir.A large number of survey and monitoring data show that those old landslides in the TGR have the characteristics of diverse structure and varied activity mode.In this paper,the Zigui-Wanzhou section with the most intensive landslides in the TGR is taken as the research area,and those large old landslides in this section are taken as the research objects.Based on the structure of landslide and the systematic analysis of dynamic characteristics,this paper analyzes the response characteristics of underground water level to the fluctuation of reservoir water level and the deformation.As the monitoring data of landslide with the complex structure is scarce and fuzzy,it is difficult to analyze the relationship between the underground water level and the reservoir water level.A typical landslide is taken as a conceptual model,using numerical simulation method.The response law of underground water level to reservoir water level fluctuation and its mechanism in complex landslide are studied.Based on the viewpoint that groundwater is controlled by the permeability of slip zone and slip body,a classification scheme of landslide structure with the layer number of slip zone as the primary index and the permeability of slip body as the secondary index was proposed,and the landslide was divided into three categories and 39 subcategories.Through the systematic analysis of the survey data and long-term monitoring data of 60 large-scale landslides in Zigui-Wanzhou section of the TGR,it is concluded that those large-scale landslides in this section belong to seven categories,among which those landslides with single-layer sliding zone + weak permeability of sliding body are the most,and the number of the three-layer landslide is the least and only three.It is found that the response rate of the groundwater level to the reservoir water level is negatively correlated to the permeability of the slide body.The response law of the underground water level in the landslide with multi-layer structure is not obvious,which may be because groundwater monitoring is not accurate,and the underground water level obtained may be the mixed water level.The deformation of those seven kind of landslide is closely related to its structure,for example,The ?-3 and ?-9 cumulative displacement curve form is given priority to with a small oscillation shape;The ?-1 and ?-3 cumulative displacement curve form is given priority to with mutation ladder shape;?-6 cumulative displacement curve is given priority to with linear growth form.Based on the multi-step coupling numerical simulation,a systematic study on 15 conceptual landslide models with the same form and different structure was conducted.The response law of the rate of groundwater level to reservoir level is related to the permeability of slip body and the deformation of landslide is negatively related to the permeability of slip body.The response law of underground water level to the fluctuation of reservoir water level in a complex landslide is closely related to its structure,which is mainly manifested in five response forms.When the reservoir water level rises,the double-layer landslide has two forms of deformation due to different structures.the three-layer landslide has three forms of deformation due todifferent structures.When the reservoir water level drops,the double-layer landslide has two forms of deformation and the three-layer landslide has three forms of deformation in the same.