上海城区地面沉降及其对地下水采灌量的响应

LAND SUBSIDENCE IN SHANGHAI CITY AND ITS RESPONSE TO GROUNDWATER EXPLOITATION AND REINJECTION

上海城区地面沉降主要是由超采地下水、松散沉积地层压实等因素共同作用导致的,并引发多种次生灾害。F4分层标监测数据指示的地面沉降情况,显示上海城区地面沉降表现为总体具有非线性变化的规律,特别是1980年代以来,表现出垂向逐渐增大的特点,在空间上也不断扩展,直至2001年才始有缓和的趋势。在不同时段,随地下水开采量及开采层次的变化,上海城区地面沉降表现出不同的特征。结合1990~2009年20年内第四含水层地下水采灌量数据,得出地面沉降对地下水采灌量的响应关系为：地下水开采量增加,地层沉降量增大;地下水开采量减少,地层沉降量减小,但地面沉降相对于地下水开采具有滞后性;随着逐年的回灌,地层沉降量减小,且地下水回灌效果与回灌层位有直接关系。

Land subsidence in the Shanghai City is mainly caused by the over exploitation of groundwater and loose strata compaction. Land subsidence has led to many secondary disasters. The monitoring data of F4 layerwise mark shows that land subsidence in the Shanghai City generally presented nonlinear variation. Especially since the 1980 s, the data showed gradual vertical increases and constant spatial expansion. This change was slowed down until the 2001. In different periods,with the changes of groundwater exploitation and mining level, land subsidence exhibited different characteristics. The 20years（1990–2009） fourth aquifer data showed the response of land subsidence to groundwater exploitation and reinjection：the land subsidence increased with intensified groundwater exploitation, and reduced with decreased groundwater exploitation, but the land subsidence relative to the groundwater exploitation lagged behind. The land subsidence amount reduced with the increase of the reinjection, and the effect of the groundwater recharge had a direct relationship with the recharged aquifer.