| The total length of the route"G0711 Urumqi-Juli highway"SJ-1 section is approximately 49km.It is located in the foothills of the Tianshan Mountains in the Urumqi County of Xinjiang Uygur Autonomous Region.The investigation section belongs to the high altitude,high latitude and high intensity region.The route spans various landforms,and the collapse and debris flow geological disasters are developed.It seriously threatens people’s life and property safety and the construction and operation of the expressway.Investigation and evaluation of geological disasters along the line have important practical significance.The author went deep into the site to conduct investigations and read a large number of relevant literature at home and abroad,investigated and analyzed the distribution laws and control factors of collapse,debris flow disasters in the area,and then used relevant methods and models to conduct risk assessments of geological hazards and proposed targeted prevention,in order to provide reference for highway design and construction and prevention of geological disasters along this section.The main contents and results of this study are as follows:(1)The research section belongs to the Tianshan structural belt and there are 4fractures.The survey area spans various landforms,from north to south,they can be divided into hills,floodplain plains,low mountain and hilly areas,eroded tectonic mountains,and mountain break basins.The overall topography is higher at the North and lower at the South and mainly reveals the following stratum:(1)Quaternary strata.It is mainly alluvial and diluvial,which is distributed along the lower reaches of urumqi river.The corresponding highway section is about K1-K30.(2)Jurassic strata,the lithology is mainly sandstone,and some of them are covered with thin-bedded mudstone.(3)Carboniferous strata,mainly composed of gray-black tuffs;(2)Along the line,there are altogether 30 developmental collapse and 20 debris flows.The distribution and development characteristics are as follows:In terms of time,from June to September is high-incidence season of geological disasters.Spatially,the collapse occurred in the erosion structure at mountain area and faulted basin areas,with 21 sites and 9 sites respectively;from the collapse height relative to the river,the maximum is 50-100m,a total of 14 sites;the smallest are 200-250m and350-400m,each has 1 site;In terms of the slope of the collapse zone,there are 12places in total that distributed between 40oand 60o,and there are respectively 9collapses between 20o-40oand 40o-80o;In terms of the collapse scale,there are 18small sizes,10 medium-sized ones,and 2 large-sized ones.The collapse can be divided into dumping,slipping,and crashing by instability.The debris flow is distributed in hills and erosion structure at mountain area,and there are 18 sites and 2sites respectively;from the type of debris flow,they can be divided into Slope debris flow and gully debris flow,with 14 sites and 6 sites respectively;from the debris flow scale,there are three medium-sized and 17 small-sized ones.(3)Statistical analysis of the influencing factors of geological disasters,including intrinsic factors(topography,formation lithology,geological structure,slope type and river system)and external factors(climatic factors,freeze-thaw effects,and Human activities),and through the ArcGIS platform,the contribution rates of various factors to the development distribution of geological disasters are analyzed,and the best factor combination conducive to the occurrence of geological disasters is summarized.The results show that:(1)In hard rock,the slope sensitivity is the strongest when the elevation is 2000-2400m,slope is 40oto 60o,the distance is 1500m from the fault,and the rock structure is disintegrated.(2)In loose rock,the debris flow sensitivity is the strongest when slopes are 20oto 40o,and elevations are 1600-2000m.(4)Construct a risk assessment system and use the AHP-CF combination method to calculate the deterministic weights of the collapse and debris flow hazards.ArcGIS is used to assess and categorize the geological hazards in the study area and classify it as four dangerous levels,they are extremely low risk area,low-risk area,middle-risk area,and high-risk area.The area of extremely low risk area is 82.76 km~2,no disasters have been developed;the area of low risk area is 92.13km~2,no disasters have been developed;Medium-risk area is 48.13km~2,there are 18 debris flows and 4 collapses;the area of high risk area is 34.28 km~2,there are 2 debris flows and 26 collapses.The ROC curve was used to test the rationality of the evaluation model.The AUC value was 83.21%,indicating that the accuracy of the model evaluation was very high,and it could be applied to the geological disaster risk assessment in the study area.(5)For different types of geological disasters,combined with their characteristics and actual conditions,the prevention and control measures are analyzed and discussed,and corresponding suggestions are proposed.The measures suitable for the prevention and control of the collapse disaster along the route include route avoidance,active network protection,support protection,spray anchor protection,and shed hole structure,passive nets and stone wall structures and the removal of dangerous rock.For debris flows,biological measures and engineering measures are combined to prevent and treat them. |
