综合物探方法在南宁地铁溶洞探测中的应用

Application of integrated geophysical method to Karst cave exploration of metro engineering in Nanning

随着城市化进程的加速,城市轨道交通得以快速发展.地铁成为未来城市主要交通建设方向之一.溶洞的地质特征又是地铁施工中的难点.本次研究区位于南宁市境内,地铁线路将穿越邕江堆积、河谷阶地区、溶蚀残丘谷地区和侵蚀、剥蚀丘陵区.经初步勘察发现研究区有多处溶洞且该段地处市中心,车流量较大、地下管线较复杂,以商业和居住为主.为了查明研究区溶洞发育情况,结合当地地质构造条件且考虑到地球物理存在多解性的特点.采用高密度电法与地质雷达相结合对研究区内的溶洞进行探测,其中地质雷达用来填补高密度电法勘探效果不理想的区域(例如沥青或混凝土路面).两种方法相互结合达到研究区全面覆盖的目的.进而对研究区的溶洞性质和溶洞空间发育形态进行确定,再通过钻孔对比验证取得了良好效果.物探方法共推断9处溶洞的研究结果表明地质雷达可以较好的填补高密度电法勘探效果不理想的区域.使这种综合物探方法针对溶洞探测获得了较好的效果.最终为工程设计及施工提供了可靠的依据.

Urban rail transits have developed rapidly,with the acceleration of the urbanization process. Among all these transits,subway become apromising direction of the city ＇s major traffic construction. However,the geological characteristics of the Karst caves are the difficulties in the subway construction. The study area is located in Nanning City,Guangxi Province,China. The subway lines will pass through a complicated area, which contains Yongjiang accumulation,the terrace in river valley area,dissolve residual valley area,erosion and denudation hilly areas. A preliminary survey found that there were many caves in the study area. What＇s more,the section was located in the city center with large traffic flow,complex underground pipelines and business and residence areas mainly. In order to find out the development of cave in the study area, combined with the local geological structure conditions and taking the geophysical existence of the characteristics of multi-solutioninto account,the high density resistivity method and geological radar were used to detect the caves. Geological radar was used to cover the area where the results of high density resistivity method was not ideal（ Such as asphalt or concrete pavement）. The two methods are combined with each other to achieve the full coverage of the study area,and then the karst character of the study area and the spatial development of the cave were determined.Moreover,borehole results proof the reliability of this study. The results of the nine cave studies show that the geological radar can better fill the area where the high-density electrical method is not ideal for exploration. This combination of geophysical methods for the 9 cases obtained a better effect in the Karst caves areas,and ultimately provides a reliable basisfor the engineering design and construction.