抽灌引起的止水帷幕两侧地下水位差的形成机制与模型研究

A waterproof curtain (groundwater barrier) is often used to block groundwater seepage from surrounding soil strata during dewatering in excavation pits, so that drawdown outside of the excavation decreases and the corresponding surface settlement reduces. However, there is no method to calculate head difference at two sides of a suspended waterproof curtain during pumping-recharge at present. Aiming at the multi-aquifer system in coastal region of China, this research proposal investigates the mechanism of cutt-off barrier effect, and establishes the calculation theory to obtain head with barrier effect during pumping-recharge. Laboratory test, theoretical analysis, and numerical simulation will be employed to solve following scientific problems: i) to reveal the spatially and temporally distributon of head inside and outside of the excavation during pumping-recharge action; ii) to establish the calculation model among waterproof curtain, groundwater, soil, and well, and to propose an analytical method to calculate the head difference at two sides of waterproof curtain via considering waterproof curtain, pumping well parameters, soil parameters and recharge well parameters. This study is benefit to strengthen head distribution regularities and calculation method of head difference at two sides of waterproof curtain. It will provide scientific basis and theoretical support for controlling land subsidence, protecting the environment, and determining dewatering and recharge schemes in the regions with multi-aquifer-aquitard-system during exacavation dewatering.

悬挂式止水帷幕在基坑开挖降水过程中能有效减小坑外承压水位降深及降水引起的地表沉降，但现在没有可靠的方法预测计算降水与回灌时悬挂式止水帷幕两侧的地下水位差。本项目以中国沿海地区多层含水层体系为研究对象，拟探明基坑降水回灌过程中止水帷幕阻挡效应机制，建立止水帷幕阻挡效应的水位计算理论。通过室内试验、理论分析、数值模拟相结合的研究手段，解决如下关键科学问题：①探讨地下水抽灌作用下止水帷幕两侧水位差形成机制；②建立止水帷幕-水-土-井相互作用的计算模型，提出考虑止水帷幕深度、降水井参数、土性参数及回灌井参数的止水帷幕两侧水位差的计算方法。研究成果预期可以突破现有基坑开挖降水回灌时，止水帷幕两侧水位分布规律以及止水帷幕两侧水位差解析计算方法研究缺乏的现状，为多层含水层地区基坑开挖降水过程中减少地表沉降、保护环境，确定有效基坑降水及回灌方案提供科学依据与理论支撑。

本项目以中国沿海地区多层含水层体系为研究对象，通过室内试验、理论分析、数值模拟相结合的研究手段，探明基坑降水回灌过程中止水帷幕阻挡效应机制，建立了抽水和回灌作用下止水帷幕阻挡效应的水位计算理论。解决了如下关键科学问题：①抽灌作用下基坑内外的水位纵向分布规律；②地下水抽灌作用下止水帷幕两侧水位差形成机制；③提出了回灌作用下及抽水和回灌共同作用下考虑止水帷幕深度、降水井参数、土性参数及回灌井参数的止水帷幕两侧水位差的计算方法。研究成果可以突破现有基坑开挖降回灌时，止水帷幕两侧水位分布规律以及止水帷幕两侧水位差解析计算方法研究缺乏的现状，为多层含水层地区基坑开挖降水过程中减少地表沉降、保护环境，确定有效基坑降水及回灌方案提供科学依据与理论支撑。本项目共发表SCI论文6篇，申请发明专利2项等多项成果。