基于分层监测的北京天竺地面沉降、地下水位与孔隙水压力变化规律

Study on the variation law of land subsidence,groundwater level and pore water pressure in Tianzhu,Beijing,based on stratified monitoring

为揭示天竺地面沉降监测站102 m以浅地层分层沉降规律,对天竺分层监测数据进行了分析。研究发现:①地面沉降主要发生在粘性土层,地面沉降发育情况与粘性土含量成正比,粘性土层在有效应力持续增大的作用下被压缩。②季节性变化特征方面,在一个水文年内,地面沉降所表现出的季节性形变特征与地下水位动态变化趋势有较高的相关性,丰水期地面沉降速率减缓,枯水期地面沉降速率明显增大。③不同深度土层变形量及其在总沉降量中比重构成的变化与相应的含水层水位变化幅度密切相关,现阶段北京地面沉降区浅部土体压缩减缓,中深部土体多以较快的速度持续压缩。不同埋深的粘性土体存在弹性变形、塑性变形和蠕变变形,具有显著的粘弹塑性;天竺站浅部水流从第Ⅰ粉土层向第Ⅰ中砂层越流,中部水流从第Ⅱ细砂层向第Ⅱ粘土层越流,深部水流从第Ⅲ粉质粘性土层向第Ⅱ细砂层越流。

In order to reveal the subsidence rule of shallow stratification at the depth of 102 meters in Tianzhu land subsidence monitoring station,the monitoring data of layers are analyzed.Research find that:①Land subsidence mainly occurs in clayey soil layer vertically,the development of land subsidence is proportional to the content of clayey soil,and the stratum of clayey soil is compressed under the action of continuous increase of ground stress.②In terms of seasonal variation characteristics,there is a high correlation between the seasonal deformation characteristics of land subsidence and the dynamic change trend of groundwater level in a hydrological year.The rate of land subsidence slows down in the high water period and increases obviously in the low water period.③The changes of soil deformation at different depths and its proportion in the total settlement are closely related to the corresponding variation range of aquifer water level.The compression of shallow soil in Beijing ground subsidence area slows down at present.Most of the soil in the middle and deep parts continue to compress at a faster speed.The cohesive soil with different buried depth has elastic deformation,plastic deformation and creep deformation,which has significant viscoelastoplastic.the shallow flow in Tianzhu station flows from the first silty layer to the first middle sand layer,and the middle flow flows from the second fine sand layer to the second fine sand layer.the deep water flows from the third silty clay layer to the second fine sand layer.