Study On Prevention And Control Of Construction Disaster Of Deep Foundation Pit Of Metro In Karst Development Area

With the increasing importance of urban rail transit in our daily life,more and more areas need to build urban rail,including some areas with complex geological conditions.As a city with high karst development,Kunming is deeply troubled by karst development in the process of urban rail construction.However,at present,the research on Karst problems is mainly focused on karst collapse.Few scholars have conducted relevant research on the impact of karst development on the construction process,especially on the excavation of foundation pit.Therefore,this paper takes the deep foundation pit of Metro at No.1 shaft between Juhua station and East passenger station of Kunming Metro Line 6 as an example to study the treatment of karst in the field area and the karst development Relevant analysis of the impact of foundation pit excavation process mainly includes the following contents:(1)Through core drilling and CT scanning,the specific development of karst in the site area(inside the foundation pit)is analyzed,mainly the specific growth range of karst;(2)To study the karst fillings,analyze their source type,filling state and filling degree,and give the above analysis results,and put forward the targeted treatment scheme of karst in this area;(3)The influence of different karst locations and sizes on the construction process of foundation pit is simulated respectively.Through the maximum displacement of support structure after the completion of construction,the scope of Karst Treatment in the field area is determined.The results show that the karst development of rock strata in the study area is remarkable,and it is relatively broken,mostly in the form of fragments;the karst filling material is colluvium filling material,which is in the state of half filling,and the filling degree m is32%.The pre grouting method is the most suitable method for Karst Treatment;for the karst with different diameters at the bottom and outside of the foundation pit,it will produce in the process of foundation pit construction within a certain distance from the ground and side of the foundation pit Therefore,it is necessary to carry out pre grouting treatment.The conclusion of this paper can provide theoretical reference for the prevention and control of foundation pit construction disaster in karst.