Study On Rainfall-Seepage Response And Instability Mechanism Of Panzhihua12# Landslide

Due to the special topography and geological environment conditions in the southwest region,it has caused problems for local engineering construction,especially the construction of the airport is of difficulty.Panzhihua Airport is one of the representative airports.During its construction and after its completion,it has developed geological hazards of different sizes,which threaten the safety of life and property of the airport and surrounding residents.Numerous scholars at home and abroad have made a comprehensive and multi-angle analysis of the causes,and believe that rainfall is one of the foremost inducing factor of its landslide.In order to further study the major factors affecting the landslide caused by the filling slope of the alpine airport construction site in Southwest China,this paper selects the most typical Panzhihua Airport 12# landslide as an example,taking the rainfall of the centrifugal model experiment as the research core,The centrifugal model experiment of the Panzhihua 12# landslide was constructed by a large-scale geotechnical centrifuge(500gt)of the State Key Laboratory of Chengdu University of Technology,and the effects of rainfall and seepage on the instability of the slope were studied.The main research results are as follows:(1)The errors in the centrifugal model experiments related to the previous rainfall-seepage response are studied and analyzed.The main influencing factors include: the selection of the model box,the composition of the rainfall device,the pedestal of the model,and the gradation of the packing.For this experiment,different solutions were designed for the above possible errors,and a reasonable solution was adopted.The main solutions are as follows: select the appropriate closed model box;develop a rain device that can be disassembled and assembled;redesign and manufacture the base of the model,and determine its various indicators;the gradation of the packing is based on the permeability coefficient on the basis of the prototype,and the permeability coefficient has increased by 100 times;reasonably change direction has been determined by experiments to avoid the runoff phenomenon on the surface of the slope,that is,the use of the non-slip mat B can significantly reduce the surface runoff of the slope;reasonable improvements have been made to other possible errors.(2)A centrifugal model was fabricated based on the original profile based on the similarity ratio N=130.The main design includes several aspects: according to the core rainfall and slope seepage response,the water storage tank and the water tank are designed to collect and simulate the groundwater and rainfall;considering the seepage of the slope,the permeability coefficient is the main factor,and the sandstone material and the high permeability grade are used to increase the permeability coefficient;the pore water pressure sensor and the earth pressure sensor were used to monitor the change of the model in the experiment process in real time;six rainfalls were carried out,and the regression period was 2 years which simulated the rainfall of the slope during the rainy and dry seasons.(3)According to the changes of the earth pressure sensor and the pore water pressure sensor data,combined with the actual video and photos taken during the experiment,the three main stages of slope instability during the experiment were determined as follows: 1.Consolidation compaction Stage 2.Cracking-Sliding surface incubation phase 3.Slope(slow)sliding phase.Through physical experiments and mechanical experiments,the changes of gradation after the test of the slope filler were analyzed.It was pointed out that the top of the slope was the stress concentration part,and the particles from the slope foot to the top of the slope gradually became thicker,and the unevenness coefficient gradually became larger.The mechanism of the instability of the landslide is mainly: the slope-slip effect of the soft rock layer,the slope-induced deformation caused by rainfall,and the long-term coupling of groundwater.(4)Use Geostudio's seep module and sigma module as the main numerical simulation research methods.Models based on the original section and models based on the experimental section were established.The calculations of seepage field,stress field and strain field were carried out for these two models,and the corresponding conclusions were drawn.The two models were compared with the actual centrifugal model experiments,and the parts and time points of the common phenomenon were pointed out.The differences between the three were also analyzed.It is concluded that the numerical simulation can reflect the changing trend of the experimental model,and the most sensitive part of the seepage response is located at the base interface and the filling body.