Investigations of Large Scale Sinkhole Collapses, Laibin, Guangxi, China

The study area is a typical fengcong and fenglin karst area with isolated and dissolved hills and valleys. The unconsolidated sediments above bedrock are Quaternary alluvium and colluvium. Quaternary deposits consist of silty clay, clay containing gravels, and clay. Karst bedrock units belong to the middle Carboniferous Huanglong Formation (C2h) and Nandan Formation (C2n). Rock types include thick light-gray limestone, gray fossiliferous limestone, dolomite limestone, siliceous and fossiliferous limestone, limestone containing gravels, Abstract A series of sinkholes collapsed at Jili village and Shanbei village, Laibin Guangxi, China in June 2010. A large underground stream exists in the north-south transect of the study area and passes the collapse site. Preliminary investigations revealed that extremely heavy rainfall between May 31 and June 1 2010 may have triggered this collapse event. The precipitation, as high as 469.8 mm within one day, was a record high in the study area. A long period of drought in 2009 followed by extremely heavy rainfall along with cave roof collapse may have caused the collapse event on June 3 2010. The “water hammer” effect and collapsetriggered earthquakes caused severe ground failure and fractures in residential houses and Jili Dam. Several collapse events were caused by extreme weather conditions in Guangxi over the past few years. Further studies of the relationship between extreme weather events and sinkhole collapses will help minimize the damage or impact to human infrastructure by avoiding areas susceptible to collapse or by designing infrastructure to better withstand subsidence.