Landslides On Soil Reservoir Bank Under Combined Action Of Intensive Rainfalls And Successive Waves

It is an important topic in the research of flood characteristics and mitigation technology to analyze scientifically and objectively the mechanism of landslides on soil reservoir bank and the law of sediment transport in the reservoir area.This thesis is to analyze the process of the reservoir bank landslides and study the influence of the waves on them by using independently designed and manufactured portable mobile push-plate wave maker,multi-nozzle down spray rainfall simulator,and the laser topography meter invented by the predecessors and rocker arm to carry out the model test of reservoir bank landslides under the intensive rainfall.The research mainly focuses on the following aspects:(Ⅰ)The double soil tank test is designed,and the control test can be formed under a single rainfall.A portable mobile push-plate wave maker and multi-nozzle down spray rainfall simulator were designed and made to perform,with combined action of heavy rainfall and waves,the sliding process of the reservoir bank under different water levels.The self-designed wave maker transforms the rotary motion of the servo motor into the linear motion of the wave making plate through the precision mechanical instrument of roller screw,producing waves with a period of 1-4s and a maximum wave height of 20cm.The height of the rainfall device is3.5m,the rainfall height is 2.5m,the rainfall area is 3 m×3 m,and the rainfall uniformity can reach 80%.The total length of the water tank is 3 m long and wide and 1.2 m deep,separated by a board.The bank slope consists of a gully slope of 70°,a suspended slope of 40°and a gentle slope of 3°.Horizontal projection length of a single model is 3.0m,width is 1.5m and height is 1.9m.(Ⅱ)When the reservoir water level is high,waves have a significant effect on the volume of bank reservoir landslides,but the mechanism of waves on gravity erosion is not clear.When the reservoir water level is low,the influence of waves on the volume of bank reservoir landslides is not significant.When it is at a higher water level of the reservoir,the secondary gravity erosion amount of the test group affected by waves was 31.75×10~3cm~3,while that of the test group not affected by waves was 144.42×10~3cm~3,showing a difference of 78%.Gravity erosion is the main way of reservoir bank soil erosion,when the reservoir water level is high,the total amount of secondary gravity erosion of the test groups affected by waves accounts for 72.5%of the total amount of erosion,although that of the test group not affected by waves only accounts for 42.5%of the total.However,in the single rainfall with gravity erosion,gravity erosion accounted for 54.8%of the total single rainfall erosion.(Ⅲ)Collapse is the most common gravity erosion event in landslides of reservoir bank.The number of collapses is 106 times at a low water level,accounting for 88.3%of the total gravity erosion.When the water level of the reservoir is high,the number of collapses is 30,accounting for 90.9%of the total gravity erosion.The number of gravity erosion is 120 times when the water level of the reservoir is low,which is far greater than the 33 times when the water level of the reservoir is high,and landslides in former condition is more frequent.(Ⅳ)There is always a linear correlation between the landslide volume and the landslide projected area of the soil reservoir bank under heavy rainfall.The R~2 of the test groups affected by waves and not affected by waves are 0.94 and 0.99.The growth rates of fractures area and width affected by rainfall is 115 times and 110 times of that at the stage of reservoir water immersion.The growth rate of fractures area in 15 minutes after rainfall is 81 times and 0.7times of that in reservoir water immersion and rainfall,and the growth rate of fractures width is 74 times and 0.67 times of that in reservoir water immersion and rainfall.(Ⅴ)This paper analyzes the main factors of landslides on soil reservoir bank,and consider the characteristics of soil bank,and finally puts forward the prevention and control methods according to the interaction of different interacting factors,which has a certain reference value for the establishment of reservoir bank landslide prediction system.