Research Of The Karst Development Law From Dabanqiao To Changshui Airport In Kunming

Dissolved rocks are widely distributed in the world.In China,especially in Southwest China,carbonate rocks are widely distributed,the climate is hot and humid,and the geological structure is complex,and karst is widely developed.With the implementation of the "Western Development" strategy and the advancement of the "One Belt,One Road" construction,various engineering construction activi t ies have increased sharply,and karst engineering geology problems in enginee r i ng construction activities have become more prominent;Therefore,it is of great theoretical and practical significance to find out the characteristics,laws and mechanisms of karst development and use them to guide the enginee r i ng construction in karst areas.Up to now,the research on the law of karst development has mainly focused on the influence of geological structure,stratigraphic lithology and hydrogeological conditions on karst development,However,insufficient attent io n has been paid to the effect of red clay in direct contact with soluble rock in the karst zone on the interaction mechanism between groundwater and soluble rock in the carbonate unsaturated zone;In addition,the research on karst negative terrain is mostly limited to the analysis of its spatial distribution and morphology,and there is a lack of comprehensive analysis of the causes of negative terrain.This paper takes the carbonate rock distribution area along the Dabanq iaoChangshui Airport line as the research object.Comprehensive use of on-site investigations,indoor tests,analysis,multi-scale observations and comprehens i ve analysis of borehole survey data;the natural geographic environment and engineering activities of the study area,the geological structure environment at different scales,and regional stratigraphic lithology are ascertained,The structur a l deformation of the stratum,the hydrogeological characteristics,and the development characteristics of surface and underground karsts.Furthermore,the karst development law and mechanism in the study area,especially the role of red clay in the expansion of karst space and the cause of karst negative formation are scientifically studied.The main conclusions obtained are as follows:(1)The study area is located in a large-scale imbricate structure system in the eastern part of Dianchi Lake.In addition,the study area itself is part of the wide southeast-east wing of the Tu'erguan-Dongdalongtan-Q ibuchang-Lint a ng anticline.They are the background structures for karst development in the study area,and they control the spatial distribution and production status of carbonate rocks in the area.(2)In area A,especially in the baoxianghe valley where the tuergua n dongdalongtan qibuchang Lintang anticline axis,Baiyi transverse thrust fault zone,nappe F3 and baoxianghe fault meet,the tectono deformation is strong.The clast ic rocks sandwiched by carbonate rocks in the area make the groundwater in the area converge to one side of the clastic rocks.In addition,there are many ways of karst water supply in the area,with large amount of supply and concentrated supply.It is easy to converge into "flood" at the boundary of carbonate rock and clastic rock and develop large-scale karst pipelines.The amount of groundwater recharge is also the controlling factor of strong karst in Baoxiang River Valley.Controlled by the special development pattern in the area,the development depth of pipeline karst in Baoxiang River Valley in area A may reach 70 m or even greater.(3)The results of field investigation show that the structural deformation of B1 area is weak,the dip angle of rock is small,even nearly horizontal;howeve r,the steep dip structural planes of rock mass are developed in the area,and these structural planes also become the basis of karst spatial development in the unsaturated zone of carbonate rock in B1 area.(4)The karst space developed on the basis of steeply dipping struct ura l planes will still expand on its own after being filled and blocked by red clay,indicating that the karst development in the unsaturated zone should follow a new mechanism different from the dissolution of carbonate rocks by liquid water-Saprolite-type karst.Based on the analysis of the field survey results,the sequent i a l(synchronous)cycle of "carbonate rock transformed into saprolite","saprolite is dissolved by infiltration of water" and "red clay squeezed in" is the core mecha ni s m of saprolite-type karst occurrence.(5)The lower hydraulic gradient and the occurrence of saprolite karst in the unsaturated zone of carbonate rock indicate that the karst water in the saturated zone of bedrock in Block B receives the highly discrete planar recharge in time and space,and the small-scale bedding plate karst space is developed in the saturated zone of carbonate rock.Combined with a large number of drilling data,the development depth of the pipeline karst in most areas of B1 area should be about50 m.The analysis of the development environment,spatial distribution,spatia l distribution form and geometric form of karst negative terrain in specific area shows that most of the karst negative terrain in area B1 should be caused by the collapse of the near horizontal plate karst space roof developed in the saturated zone.