长江三角洲南部地面沉降与地裂缝

Land subsidence and land fissures in the southern Yangtze River Delta

过量开采地下水导致长江三角洲南部产生严重的地面沉降和地裂缝,造成巨大的经济损失。地面沉降和地裂缝的发生和发展在时空上与地下水开采具有密切联系,在地下水开采高峰期,地面沉降速率明显增加,在地下水位稳定期和回升期,地面沉降速率显著减小,甚至出现少量回弹。平面上,地面沉降分布形态与主采层地下水位分布形态具有很强的关联性;垂向上,地面沉降分布形态与沉降层、主采层及土层的厚度、压缩性等有关,弱透水层和含水层都可能成为主要沉降层。开采地下水条件下土层的变形与其经历的地下水位变化过程有关,不仅弱透水层存在塑性和粘塑性变形,在一定水位变化条件下含水砂层也存在塑性和粘塑性变形。地面沉降是地表下所有受影响土层的变形之和,为了控制地面沉降和地裂缝的发展,应限制地下水的开采量,尤其是避免出现地下水位低于土层历史上曾经达到的最低水位。

Excessive exploitation for groundwater can cause serious land subsidence and land fissures in the southern Yangtze River Delta,resulting in huge economic losses.The occurrence and development of land subsidence and land fissures are closely related to the exploitation of groundwater in time and space,with the rate of land subsidence increasing obviously at the peak of groundwater exploitation and reducing significantly and even rebounding slightly during the stable or recovery periods of groundwater.Horizontally,the distribution pattern of land subsidence has strong correlation with that of groundwater level in the main mining layers;vertically,to the thickness of the main mining layers,soil layers and compression property.Both aquitard and aquifer can be main subsidence layers.The deformation of soil layers,triggered by exploitation for underground water,is closely related to the change process of groundwater level;plastic and visco plastic deformation occurs not only in aquitard but in water-bearing sand layers even under the condition of certain water level change.Land subsidence is accumulative effect of deformation of various subsurface layers.In order to control the development of land subsidence and land fissures,it is suggested in this study that exploitation amount of groundwater should be restricted,especially avoid the water level from reaching the lowest level occurring in the history of the soil layers.