Development characteristics and formation mechanism of karst collapse geological disasters in the river valley terrace landform area of Gongcheng County,Guangxi,China
The river valley terrace geomorphological area is the high occurrence area of karst collapse disaster in Gongcheng County,Guangxi.Based on the project of Detailed Survey of 1:50,000 Geological Hazards in Gongcheng Yao Au-tonomous County,this study analyses the distribution pattern,influencing factors and development characteristics of karst sub-sidence in the river valley terrace landform area of Gongcheng County by integrating topography and geomorphology,geological structure,stratum lithology and meteorological conditions,and explores the causes of karst subsidence in the river valley ter-race landform area by integrating the example of subsidence in a certain place of Zhufeng Village of Liwu Town,Gongcheng County.Research shows:(1)The 42 cavities in the river valley terrace are all earth cave-type cavities,and the shapes of the crater openings are mainly irregular and circular,with individual openings being square,and the direction of the long axis of the openings is roughly the same as the direction of groundwater flow.(2)The inducing factors for the development of karst collapse are mainly natural factors,supplemented by man-made factors.From the administrative area,the town with the lar-gest number of collapse development is Li Mu Town,with a total of 9 collapse disaster sites,accounting for 22.70％of the to-tal number of karst collapse disasters;from the scale point of view,the karst collapses that have occurred in the study area are dominated by small collapses,and there is only 1 collapse with a volume size larger than 500 m3,11 karst collapses with a size of 100～500 m3,and 4 karst collapses with a size of 50～100 m3,with 26 collapses smaller than 50 m3.There are 11 karst collapses with a size of 100～500 m3,4 karst collapses with a size of 50～100 m3,and 26 collapses with a size of less than 50 m3.(3)Topography is one of the main controlling factors for the formation of karst collapse disasters.Karst collapse development is affected by the thickness of the overburden soil layer;the thinner the overburden soil layer is,the thinner the roof of the soil hole is,and the more prone to ground collapse.It is mainly distributed in D2 t and C1 yt strata,and concentrated in the area where the thickness of the overlying soil layer is 5～15 m;rainfall is one of the factors inducing the development of karst collapse in the area,but it is not a decisive factor.The results of the study are intended to provide a reference basis for karst collapse prevention and management in similar areas.
river valley terracekarst collapsedevelopmental characteristicgeological disaster
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