RISK PREDICTION OF GROUND FISSURES IN SU-XI-CHANG CITIES BASED ON MULTI-FACTOR OVERLAY METHOD

The cities of Suzhou, Wuxi and Changzhou(the Su-Xi-Chang Cities) have ground fissures in some regions due to the long-term over exploitation of groundwater. Although groundwater extraction in this area has been prohibited for more than ten years, some ground fissures are still active. The development of ground fissures is affected by many factors and the mechanism is still not clear. In order to find out the influence factors of ground fissures, and then to determine the influence of each factor, the potential risk of ground fissures in the Su-Xi-Chang area is predicted based on multi-factor overlay method. This prediction is on the basis of the current status of ground fissures in the Su-Xi-Chang cities. Eight influencing factors are considered. They are bedrock depth, bedrock slope, cumulative land subsidence, subsidence slope, the second confined aquifer thickness, the second confined aquifer thickness gradient, hydraulic head reduction at the second confined aquifer, and quaternary sedimentary facies. The prediction results show that the ground fissures are prone to occur in the northern part of the Su-Xi-Chang cities, and the potential of ground fissures occurring in the southeast is relatively small. The results are primarily coincident with field investigations on ground fissures at the study area, which verifies the validity of the method. The predicted results of ground fissure risk are helpful for the planning of groundwater exploitation and urban construction.