地下水开采导致总应力变化对地面沉降的影响

地下水开采引起总应力的变化特征取决于所采地下水所处的层位。本文以抽取典型多层含水层系统不同层位的地下水为例,分别计算出了潜水含水层、弱透水层和承压含水层中总应力的表达式,得出了抽取不同层位地下水总应力的变化规律,并且根据有效应力原理,分析不同层位的有效应力变化特征,最后结合有效应力与地面沉降量计算之间的关系式,归纳出抽取不同层位地下水时总应力的变化对地面沉降的影响。通过分析得出,抽取承压含水层地下水(仍处于承压状态下),总应力不随抽水发生变化;而抽取潜水层的地下水,总应力是变化的。本文最后通过数值试验的方法验证了抽取潜水含水层中的地下水,总应力随着抽水时间逐渐减小,地面沉降量也会随着总应力的下降而减小。并且计算得出在600天的模拟时期内,总应力变化较总应力不变的情况下,累积沉降量要小将近30%。

The influence of the variation of total stress caused by extracting the groundwater on ground subsidence

The variation of total stress caused by extracting the groundwater depends on the groundwater stratum. The paper takes extraction of groundwater from different layers for example, separately calculates the expression of the total stress of the unconfined aquifer, aquitard and confined aquifer, and leading to the rule of total stress variation, then according to the principle of effective stress, analyses variation features of the effective stress, finally combines the relationship of effective stress and the ground settlement, summarizes how the variable total stress has influence on the surface subsidence when extracting groundwater of different layers. Through the above analysis, we draw the following conclusions： extracting the groundwater from the confined aquifer, it concludes that total stress has no change with the pumping; while the condition is opposite with the unconfined aquifer. Finally, numerical method has been used to prove that the total stress and ground settlement reduce gradually when pumping from the unconfined aquifer; and the results show in 600 days of simulation period, the cumulative settlement is nearly 30% smaller with the variable total stress than calculated values with the constant one.