Analysis Of Formation Mechanism And Environmental Effects Of Collapses And Landslides At Hanyuan-Tongjiezi In The Dadu River

The Hanyuan-Tongjiezi belongs to the middle reaches of the Dadu River.With the further implementation of the western development strategy,the urban construction keep expanding,the level of traffic facilities continue to improve,the water conservancy and the hydropower facilities are gradually completed and put into use at Hanyuan-Tongjiezi in the Dadu River.However,the collapses and landslides that distribute at the Hanyuan-Tongjiezi in the Dadu River threat to the infrastrtucture and the safety of people's life and property.Therefore,it has important realistic value and significance to study the collapses and landslides at the Hanyuan-Tongjiezi in the Dadu River.Through remote sensing and field investigation,the analysis of engineering geological conditions,the analysis of the mechanism of geological processes,the universal distinct element code,the analysis of sedimentary facies and sedimentary environment,we deeply study the development characteristics,formation mechanism and environmental effects of the collapses and landslides at the Hanyuan-Tongjiezi in the Dadu River.The main results are as follows:(1)According to the spatial properties of combination of different strata and river valley formation,the segmentation of slope structure on Dadu River Hanyuan-Tongjiezi is anlysed,and the results show that the main stream reaches are gently inclined bank slope of clastic rock and carbonate rock.(2)There are 32 collapses at the Hanyuan-Tongjiezi in the Dadu River.These collapses are beaded distribution along the main stream of the Dadu River,and are mainly distributed in the valley of the river.The slope shape of the most of collapse is convex,and the scale is mainly small collapse.(3)There are 61 landslides at the Hanyuan-Tongjiezi in the Dadu River.These landslides are linear distributed along the main stream of the Dadu River,and mainly distributed in the broad valley of the river.The planform of the most of landslides deposit is rectangular,the profile form of the most of landslides deposit is ladder,and the scale is mainly large landslide.(4)The collapses and landslides at the Hanyuan-Tongjiezi in the Dadu River aremainly affected by the river valley evolution,topography,lithology,slope structure and human engineering activities.Statistical analysis shows: the collapses are mainly distributed within the range of 550 m to 750 m and in the range of 50° to 80°,and the landslides are mainly distributed within the range 600 m to 980 m and in the range of24° to 36°.Collapses occur in hard rocks dominated by limestone,while landslides occur in soft rocks interbedded with sand and shale.The above influence factors determine that the formation mechanisemes of collapses is falling,accounting for56% of the total,and the formation mechanisemes of landslides is sliding-fracturing,accounting for 50.8% of the total.(5)The environmental effects caused by collapse and landslide disasters damming river are analyzed.The analysis shows that the collapse and landslide disasters at the Hanyuan-Tongjiezi in the Dadu River mainly in influence on the river valley landform,the influence on the traffic facilities,the formation of deep overburden layer and the reservoir caused serious influence.Taking Hetaoping landslide damming as an example,the above influences are analyzed and discussed.