北京亦庄轻轨工程场地水位下降引起地面沉降量的评估方法探讨

地下水大量抽取所引起的地面沉降,是工程建设场地地质灾害危险性评估中最重要的地面变形灾种之一.由于场地情况各异,目前的定量评估尚无通用模式.一种基于区域水位下降量和相应地面沉降量拟合反演区域骨架成分弹性储水因子和非弹性储水因子的最小二乘方法已经提出.利用该方法反演出北京亦庄轻轨工程建设场地的代表性骨架成分弹性储水因子和非弹性储水因子.在此基础上,采用有效应力法对该场地的地面沉降趋势进行了预测评估.结果表明:如果未来地下水抽取状况不能得到实质性的控制,该场地东南部区域2006-2015年可能新增高达70～126 mm的地面沉降.

A method for estimating land subsidence induced by groundwater extraction and its application to site evaluation of Yizhuang light railway in Beijing

Land subsidence induced by groundwater extraction is one of the most serious geo-hazards to be investigated when evaluating a construction site. Because the geological and hydrological situations are usually quite different from site to site, there has been no a generalized method to qualify the estimation of land subsidence for all kinds of sites. A method using the least square method and the measured data set of groundwater decline and the corresponding subsidence to determine the storage coefficients of elastic and non-elastic aquifers of a site is introduced. With the method and data from the construction site of Yizhuang light railway in Beijing, the optimum values of the storage coefficients of elastic and non-elastic aquifers of the site are determined as Sske=(7.0±2.0)×10-7 and Sskv=(6.93±0.5)×10-5, respectively. Further, with the storage coefficients and an effective stress analysis method, the land subsidence tendency of the construction site of Yizhuang light railway is evaluated. The results show that the southeastern part of the construction site will subside as large as 70－126 mm in the next 10 years (2006 to 2015) if the situation of groundwater extraction is not improved.