Abstract:Accompanying with the acceleration of urbanization, urban rail transit has developed rapidly in Ji'nan city in recent years, and subway has become one of the main directions of future traffic construction . As a spring city, karst is an important channel for spring water recharge and runoff. It is widely developed in Ji'nan area, but it is also a difficult problem in subway construction. Therefore, it is very important to identify the degree of karst development under Metro lines. Comparing with the "big size" of karst in south China, the karst size in Ji'nan area is much smaller. It is mostly honeycomb-like and fissure-like, and there is no obvious rule to follow in space. Thus, higher requirements have been put forward in the resolution of geophysical prospecting work. The research area is the section from Renjiazhuang Station to Lashan Station along Liuchangshan Road on Metro Line 2. After preliminary exploration, there are many karsts in this area and the line is located in the downtown area, with large traffic flow and complex pipelines. In order to study the karst development in this area. In this paper, electromagnetic wave CT technology has been used to detect the karst in this area. By studying the difference of electromagnetic wave absorption coefficient beta of geological medium in this area, and comparing with drilling data, the value range of absorption coefficient in karst area is deduced. Finally, the deduced karst area is drilled. The coincidence degree between geophysical prospecting and drilling is verified. This method has achieved good results in karst exploration, and provides a reliable basis for the design and construction of Ji'nan Metro.
