Morphological Characteristics And Genetic Mechanism Of Negative Topography In Large Slab Bridge-small Sentinel Corridor Belt And Gejiu Karst Highland

Carbonate deep karst will produce a series of different near-surface manifestations or signs and evidences,which have more direct indications for the construction of a unified pattern of(near)surface-deep karst development.Combining these black box signs with the hydrogeological conditions of the karst development area,the distribution of fault structures.will help to construct a karst development model with sufficient theoretical basis and closer to the actual karst development,so as to make an assessment of the karst development degree closer to the actual And expected.The Dabanqiao-Xiaoshao wide and gentle corridor in the northeastern part of the Dianchi Basin and the Gejiu Tin Mine in the South China Fold System and its surroundings(Gejiu karst highlands)are all karst development areas underlayed by carbonate rocks,but the surface karst landscape It's quite different.Therefore,based on the identification of the natural geographical conditions,geological structure environment,and hydrogeological conditions of the two places,the exploration of the negative topographic features and distribution rules of the karsts in the two places is very important for understanding the special karst development mechanisms(models)of the two places.Based on the in-depth analysis of the Dabanqiao-Xiaoshao wide and gentle corridor belt and Gejiu karst highland geological survey,surveying and mapping,geographic information database and other data,combined with the on-site survey,it accurately identified the large and small corridors and their surrounding areas.Geographical conditions,geological structure environment,hydrogeological conditions.Establish a scientific and accurate karst negative topography database based on the Dabanqiao-Xiaoshao wide and gentle corridor zone and Gejiu karst highland DEM elevation data and field survey data,select parameters suitable for characterizing negative topography and spatial distribution characteristics,and use comparative analysis methods The difference and spatial distribution of negative topography between large and small corridors and Gejiu karst highlands are explored.Finally,according to the acquired drilling data,hydrogeological conditions,fault structure information,DEM data and other data,the genetic mechanism of the negative karst topography in the two places is explained.The main results are summarized as follows:1.The proportions of the first-level parameters such as the perimeter,projected area,and long axis of the karst negative terrain in the two places indicate that the small(micro)-scale negative terrain in the large and small corridors dominates the area,while the large-scale negative terrain in the Gejiu karst highland Negative terrain occupies control.2.In the case of similar negative terrain scales,the roundness coefficient of the negative terrain of the large and small corridors is higher,and the basic outline is nearly circular or elliptical,while the negative terrain roundness coefficient of the Gejiu karst highland is low,and the basic outline is elongated,Isometric.3.In the case of similar negative terrain scales,the convexity and boundary complexity coefficients of the negative terrain of the large and small corridors are low,the boundaries are rounder and more regular,the flatness is low and the proportion is high,the profile curvature is uniformly distributed,and the boundary contour characteristics are Transmissive in the vertical direction.The negative topography of the large and small corridors is rounded,small in scale,and closer to the shallow dish shape,while the negative topography of Gejiu karst highlands has high convexity and boundary complexity coefficients,and the boundary is irregular and severely tortuous,especially for large-scale negative topography.The topographic boundary has the highest degree of "tortuousness",and its shape is diversified.4.In terms of spatial distribution,the negative topography of large and small corridors is distributed evenly and densely,and the negative topography of Gejiu karst highlands is distributed in a regional aggregation type.Under the same spatial scale,the degree of aggregation between the negative topography of large and small corridors is higher than the negative topography of Gejiu karst highland.5.The control of the fault structure on the negative topography of the karst corridors is mainly reflected in the constraint of the long axis direction of the negative karst topography,while the control of the fault structure on the negative topography of the Gejiu karst highland is mainly reflected in the dual control of the shape and spatial distribution of the negative topography.6.The development and evolution of the negative topography of the large and small corridors is mainly controlled by the wide and long-distance karst water replenishment environment,the high water-holding,low-permeability residual layer(red clay)and the underlying carbonate rock with few fractures.The negative topography of Gejiu karst highland is mainly controlled by the high dip angle of the fault structure system and the huge height difference from the erosion base level of the Red River.