| The geological environment of Nanning City is complex,so in the subway construction will facing many engineering geological problems,one of which is the karst.Karst developped in some sections of Nanning Metro Line 4,in which drilling and geophysical exploration stage has revealed some caves.There are some hidden dangers duting the subway construction and operation stage.Therefore,it is not only of great theoretical significance,but also of practical significance for the project to find out the karst development situation of the planning route and have some acquaintance with the degree of karst development before construction.Based on the regional engineering geological environment in Nanning,this paper analyzes the mechanism and influencing factors of karst development,and summarizes the distribution characteristics of karst.Referring to the vertical zonation method of karst development intensity and classification of karst development degree and its index division method,The evaluation index of karst development intensity is selected by analogy,and the intensity grade of each index is divided,and the development intensity grade was evaluated on the three stations and three sections from Feilong Road station to Panjie station.And the engineering geological problems caused by karst are analyzed,the stability of the site and the stability of karst are mainly discussed.The main conclusions are as follows:(1)The karst development of Nanning Metro No.4 line is nonuniform banded distributed on the plane.Vertically,it is multi-layered,with 167 boreholes reveal more than 2 caves.Most of the individual caves are of small size.(2)The karst development intensity is very strong in the section from the Feilong Road Station to the Sports Center East Station.And the karst development in the section from the Sports Center East Station to Panjie Station is medium.The stability of the karst cave in the section from Feilong Road Station to the Sports Center East Station is poor,and the phenomenon of collapse and instability may occur in the construction of the project,and karst cave treatment is recommended for engineering construction. |
