| Bazhou District of Bazhong City is located in the northeast of Sichuan Basin,the west of Dazhou,and the southern foot of Micang Mountain.Under the action of geological environment and rainfall,geological disasters of landslide and collapse occur frequently in the district,which has a great impact on the development of local society and economy.The risk assessment of geological disasters considers the information of geological disasters and disaster-bearing bodies,and the results are of great reference value for the prevention and control of geological disasters,economic construction and urban planning.On the basis of field investigation and regional basic geological data collection,this paper analyzes and summarizes the types,characteristics and spatio-temporal distribution of geological disasters in Bazhou District.Based on GIS technology,the information content method is used to evaluate the risk of geological disasters.The analytic hierarchy process(AHP)and comprehensive vulnerability index model are used to evaluate the risk of geological disasters.Based on the two evaluation results,the disaster risk expression of "risk = hazard ×vulnerability" is combined with the risk evaluation grade matrix to evaluate the geological hazard risk.The main contents and achievements are as follows:(1)Through field investigation and collection of regional basic geological data,the types,development characteristics and distribution rules of geological disasters in Bazhou District of Bazhong City are obtained.The results show that there are 1002 geological disasters in Bazhou,including landslide and collapse,among which landslide is the main geological disaster in 906,accounting for 90.42% of the total disasters.Landslide geological disasters were distributed in all towns in Bazhou district,with Pingliang Town having the largest number of 80 disasters,accounting for 8.83% of the total.The main material type of landslide is rock landslide with 897 sites.The main plane form of landslide is lingual,with 444 places.The length and width of the landslide are mainly in the range of 10-200 m and 20-600 m,accounting for 96.14% and 93.27% of the total,respectively.The landslide bed is mainly the underlying bedrock,and the lithology is Jurassic(J)and Cretaceous(K)sand-mudstone interbed,mudstone interbedded with sandstone and sandstone intermudstone.The slip zone is usually composed of silty clay containing gravel and clay mixed with gravel,and is generally between 0.1 and 0.5m thick.In Bazhou District,collapse geological disasters were also distributed in all towns and townships,with Liangyong Town and Shuining Si town being the most,accounting for 10.41% of the total.The material composition of the collapse disaster is rock,and the formation mechanism is mainly falling type,with a total of 81;The development elevation of the collapse is between 370-1100 m,and the main range is 400-600 m.There are altogether 66 places.The maximum collapse drop range is 10～60m,the main range is 10～30m,a total of 72 places;There are 56 places in which the farthest distance of rock fall ranges from2 to 70 m and the main distance ranges from 2 to 20 m.In terms of time,most geological disasters occur in the rainy season from June to September.In terms of space,geological disasters are mainly distributed in areas with intensive human engineering activities,on both sides of roads and near rivers.(2)Using the information content model,slope,topographic curvature,engineering geological rock group,slope structure,distance from water system,distance from road,vegetation coverage and rainfall were selected as evaluation factors to evaluate the geological hazard.The results show that the information content model has an evaluation accuracy of0.641,which can better evaluate and predict the geological hazard of Bazhou District.Bazhou District is divided into five levels: high,medium,medium,medium and low.The high risk areas are mainly distributed on both sides of rivers and roads,and the middle and high risk areas are distributed on the edge of the high risk areas and in the areas where human engineering activities gather.The middle danger areas are mainly distributed in the areas where the river is still high and the distance from the river system and roads is relatively far or near some tributaries,and the distribution is sparse overall.The low-risk areas and mediumlow risk areas are mainly distributed in the mountainous areas around Bazhou District,with high elevation,large slope,few settlements,far from water systems and roads,and high vegetation coverage.(3)With grid as evaluation unit,population density,building density and road density as evaluation indexes,AHP was used to determine the index weight,and the comprehensive vulnerability model was used to superimpose the single vulnerability evaluation results to get the geological disaster vulnerability evaluation results in Bazhou District.The results show that the vulnerability of geological disasters in Bazhou district can be divided into five levels:high,medium,medium,low and low.The high-vulnerable area,medium-high vulnerable area,medium-vulnerable area and medium-low vulnerable area are scattered in Huifeng,Dongcheng,Xicheng,Gangliang,Shixin and Xingwen in the northwest,while the lowvulnerable area occupies most of the area.(4)On the basis of the evaluation results of geological hazard and vulnerability,the " risk =hazard × vulnerability " model was used to evaluate the geological hazard risk,and the evaluation results were graded by the risk grade judgment matrix to get the geological hazard risk evaluation map of the study area,and the risk of the study area was divided into five grades: high,medium,medium,low and low.Among them,low-risk areas and medium-low risk areas are mainly distributed in places with low road density,population density and building density and far away from roads and water systems,while medium-risk areas are distributed in places with medium road density,population density and building density and relatively close to roads and water systems.Middle-high risk areas and high-risk areas are mainly distributed in areas with high road density,population density and building density,and close to roads and water systems.(5)The results of geological disaster risk assessment in Bazhou District can provide reasonable reference basis for the risk control and management of geological disaster in Bazhou District.Based on the four risk control principles of "avoiding and optimizing the layout","people-oriented","prioritizing and urgent",and "synchronizing with economic development",combined with the risk assessment results of Bazhou District,Different risk zones are divided into corresponding control zones of different levels.Among them,the high risk area is the key control area,the medium-high risk area and the medium-low risk area are the secondary key control area,and the low risk area and the medium-low risk area are the general control area. |
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