Study On Stability And Treatment Design Of Bank Slope And Cemented Soil Cavity Soaked In Reservoir Water For A Long Time,a Cultural Relic Protection Site In Sichuan Province

The protection of stone relics has always been a difficult problem recognized by researchers at home and abroad.Natural factors,geological factors and human engineering activities may cause irreparable damage to the existence of stone cultural relics.The maijishan grottoes had a large area of collapse due to the earthquake.The May 12,2018 earthquake in sichuan province caused a large number of cultural relics in need of rescue protection,and the qiuci grottoes buried a large number of holes due to the landslide.Human engineering activities such as the impoundment of the three gorges reservoir area,a total of 1,087 cultural relics are listed as objects of protection,including the white crane beam in fuling,known as the "world's first hydrological station".The stability of stone cultural relics is becoming more and more serious.Therefore,this article with her honey haired flat crossing the cave sites,for example,with a solid geological investigation and the basis of the detailed geological data,using aerial drones,high-density electrical prospecting,geophysical prospecting methods such as seismic surface wave method,to clarify her honey haired flat cross cave sites ontology(cave)and carrier(slopes)of formation structure and formation causes,especially the rhythm of cave sites accumulation layer formation and structure features.The mineral composition,chemical composition,genetic and structural characteristics of calcareous consolidated soil were elucidates by hydrochemical analysis,optical microscope,XRD and XRF test methods.Numerical simulation,physical simulation and reliability analysis were used to comprehensively analyze the influence of reservoir water level variation,rock and soil parameter heterogeneity,earthquake and rainfall conditions,and cave cave structure on the stability and deformation of the cave site.Finally,the "cofferdam type external support and internal support structure" management plan and system monitoring project are put forward to ensure the long-term survival of the cave site in jiaopingdu underwater.Through the above systematic research work,the following main understandings are obtained:(1)the accumulation layer of the cave in the site is mainly composed of colluvial boulders,slope gravel and breccia.Under the action of multiple periods of water flow,the rhythmic layer is formed.There are as many as 10 layers,which have the characteristics of multi-layer,multi-sequence,different degree of cementation,out-slope of downdip,mixed lithology,developed unloading fissures and salty substances.The bedrock at the cave is dominated by anti-dip phyllite,SLATE and dolomite.The cave is composed of 7 independent caves and 3 holes,which are arcuate in the plane.(2)calcareous consolidated soil is a key rock mass occurring in caves and belongs to continental clastic rocks.The clastic material comes from the three rock types of upper slope,namely gabbro,dolomite,phyllite and SLATE.Its mineral composition is calcite(carbonate minerals),cementation type is basement cementation.Water-rock environment is the main reason for the cementation of calcareous soil.High salinity water quality,hot and dry climate,porosity and connectivity are the bonding conditions.(3)according to the rock triaxial experiment,the strength change characteristics of the calcareous consolidated soil after different soaking time were obtained.The cohesion C decreased sharply,from 3.6mpa to 0.5mpa,with a decrease rate of 86.1%.The loss of calcite,dolomite and other substances in calcareous consolidated soil is the reason for the decrease in strength,and the anion loss is related to HCO > SO > Cl.The cationic loss is related to Mg > Ca.The reason for the loss is the leaching and cation exchange between calcareous cement soil and solution water.(4)regardless of rainfall,earthquake and other conditions,the rising water level of the reservoir directly causes instability and destruction of the cave site.There are three types of instability failure: first,the slope front instability,the maximum instability of the leading edge of the sliding surface shear entrance from the slope shoulder about 30 m,the bottom shear outlet for the slope near the foot;Secondly,the rhythmic layer of two layers of rubble with weak cementation,good penetrability and maximum deformation plays a controlling role in displacement.Thirdly,with the increase of soaking time,the cementing strength of calcareous consolidated soil is further weakened,and the accumulation body of the site slides along the overburden interface.(5)under the design concept that stability is the premise,the principle of minimal intervention and the principle of reversibility,the governance design scheme of "cofferdam type external support and internal support structure" is proposed to achieve the design goal of "solid slope(carrier of cultural relics protection)" and "cave protection(body of cultural relics protection)" under water for a long time.Systematic monitoring works should be set up to catch abnormal information when there are signs of possible deformation and failure,and necessary engineering measures should be taken to the slope in time.