Risk of geohazards caused by karst processes in the Erlangmiao area, Wushan County, Three Gorges reservoir region

Abstract：Karst recently discovered during relocation of migrants in the Three Gorges reservoir region is an important engineering geological problem. The Erlangmiao area in the new city of Wushan County is a geohazard monitoring and early-warning demonstration area. In the area, limestone of the Triassic Jialingjiang Formation underwent strong karstification due to the special climatic, hydrological and geological conditions, so the rock mass structure becomes very complex and massive limestone has been turned into layered, fractured rock masses, karst breccia, argillaceous bands and eluvial breccia layers. There are different features and intensities of karstification in different geomorphological zones. Generally, karstification increases from west to east and from the bottom of the section upward. Among other things, the zones of transition from the steep to gentle topography and the lower part of gullies are the strongest karstification zones. Karstification gave rise to an assemblage framework of various microlandforms and special rock masses. With karstification, the mechanical intensity and stability of rock masses decrease progressively, which, together with other natural processes and human activities, may cause geohazards such as uneven subsidence, ground cracks, landslides, avalanches, mudflows and ground collapses. Great attention must be paid to these problems in the process of migrants resettlement and future town construction.