山东省枣庄市十里泉、丁王庄一带地面塌陷的成因及防治对策

Genetic analysis and countermeasures for surface collapse in Shiliquan and Dingwangzhuang areas, Zaozhuang city,Shandong province

十里泉和丁王庄是枣庄市两个最大的水源地。区内第四系覆盖层厚５～１０ｍ，其结构上细下粗，下伏的奥陶系灰岩岩溶裂隙发育。大量抽取地下水使地下水位波动的幅度增大，从而潜蚀作用增强。当地下水位降至基岩面以下时，又使上覆土层的浮托力减小，同时在岩溶洞穴中产生真空，对土层的吸力增大。上述各种作用均能影响土层结构，使其强度减弱，最终导致地面塌陷的产生。对塌陷拟采取以下防治对策：（１）采用大流量大降深抽水的方法，把地下水位控制在基岩面以下，使土层始终位于包气带之中免遭地下水各种作用的破坏，同时还可增加地下水的可采资源量。（２）兴建建筑物时，应先进行详细的工程地质勘探，避开岩溶裂隙发育地段。若无法避开，则应对地基作加固处理。（３）对已经发生塌陷的地段，要及时进行工程治理。

Shiliquan and Dingwangzhuang areas are the two largest groundwater sourcelands of Zaozhuang City.The quaternary overburden of this areas is 5～10 meters thick and composed of sandy clay,fine sands and sand gravel layer.The underlying bedrock consists mainly of Ordovician limestones in which karst fissures are well developed.Due to the extensive pumping of groundwater, the range of phreatic fluctuation was enlarged and the suffosion was enhanced.When the groundwater level dropped lower than the surface of the bedrock,the buoyancy in covering soil is decreased.Meanwhile the vacuums occurred in carvities and their attraction force to soil was increased.All the factors mentioned above resulted in the change of soil texture that the strength of soil layer weakened,and eventually the surface collapse took place.The way for prevention and control of collapse are proposed as follows:(1)The groundwater table must be controlled below the surface of the bedrock by using pumping and drawdown.As a result,the covering soil layer will always be in the zone of aeration and may not be destroyed by the groundwater.(2)The detailed engineering geologic investigation should be done before building in order to avoid the zone of the karst fissures.Reinforcement of foundation is necessary when the fissure zone can't be avoided.(3)Engineering measures should be taken in time in the collapse areas.