滨海软土地区深大基坑群施工过程致灾机理及预警控制研究

Due to the immature of the design theory, monitoring and prediction system in excavation engineering, accidents of deep excavations occurred frequently in coastal soft soil area, which caused many severe geological disasters of city. The excavation group, which means a group of nearest excavations constructed at same time or the supper large excavation divided into small parts, has been developed because the scale of underground construction was increased fast. The mechanism of disasters caused by such excavation group is more complex and the risk of the disasters is much higher than single excavations. The mechanism of the geology disasters caused during excavation group in the soft soil of coast area is analyzed in this research by the lab tests, theoretical analysis and field monitoring. The prediction and control methods of the disasters are also studied. A new apparatus for soft soil tests is developed by the considering small strain effect and the influence of unloading and seepaging. The constitutive model of soft soil under the complex stress paths during excavation group is then presented based on the lab tests. By considering multi-scale characters of the geometric model and different materials during deep excavation group, a nonlinear multi-scale numerical method based is presented to finish the large, whole process, and extractive analysis. The coupling effect between unloading of excavation and pore water pressure reducing caused by dewatering is also considered in the numerical method. The mechanism of the geology disasters and its developing behavior can be obtained based on the field surveys, model tests and numerical analysis. Then the multi-parameter risk evaluation method is built by combining the mechanical calculation and monitoring data. Finally, a system including the dynamic prediction, pre-warning and feedback control on the geology disasters during large excavation group is developed. The results and productions of this research can be used in analyzing and preventing of the disasters in underground construction of coast area.

由于基坑工程分析理论不成熟和监控预警不完善，滨海软土地区深大基坑施工的工程事故频发，诱发地面沉降等严重城市工程地质灾害。随着基坑规模的不断发展，同步施工相邻群坑群和超大面积分区开挖基坑群越来越多，其致灾机理更为复杂。本项目综合采用室内试验、理论分析和现场测试等方法，对滨海软土地区深大基坑群施工过程的致灾机理及预警监控方法开展研究。研制新型土工试验设备，揭示滨海软土在应力和渗流耦合作用下的响应机理，建立本构模型。考虑深大基坑群施工的物理、几何和时间多尺度特征，开发可分析开挖与抽水施工流固耦合的非线性多尺度数值方法，形成大规模、全过程精细分析工具。阐明基坑群施工过程的致灾机理与灾变规律，提出融合力学分析和监测数据的多参数灾变评估理论，建立深大基坑群施工过程诱发工程地质灾害的动态评估与预警控制平台。为滨海软土地区地下空间开发中重大工程的地质环境灾害效应分析与监测预警控制提供科学依据和实用方法。

由于基坑工程分析理论不成熟和监控预警不完善，滨海软土地区深大基坑施工的工程事故频发，诱发地面沉降等严重城市工程地质灾害。随着基坑规模的不断发展，同步施工的相邻型群坑群、超大面积分区开挖的分隔型基坑群、地下结构联通的连接型基坑群越来越多，其致灾机理更为复杂。本项目采用设备研制与室内试验、理论分析与数值模拟、现场测试与反馈分析等方法开展研究，系统探讨了滨海软土地区深大基坑群施工过程的致灾机理及预警监控方法。.1）基坑施工中滨海软土的力学特性与本构模拟：研制了实现渗流与应力耦合驱动的真三轴试验设备，测试滨海软土在复杂耦合作用条件下的响应规律，提出了其小应变本构模型及参数确定方法。.2）基坑群施工耦合作用过程的解析与数值分析：提出了坑间有限宽度土体土压力计算方法、基于桥域耦合算法的几何多尺度分析方法、考虑渗流应力耦合驱动的多尺度数值分析方法、基于土体小应变刚度特性的数值分析方法，实现了对不同形式基坑群结构与地质环境系统渗流应力耦合作用的分析模拟。.3）深大基坑群施工的受力变形规律与致灾机理：结合现场测试与理论分析，分别探讨了分隔型基坑群、关联型基坑群、相邻型基坑群的水土耦合相互作用机制及其受力变形特性，揭示了软土基坑群施工过程的地质环境效应及灾变演化规律。.4）深大基坑群地质灾害的多参数预警控制方法：提出了基坑群施工过程灾变风险的数据融合分析方法、多参数风险评估理论和动态反分析计算方法，开发了软土深大基坑群施工过程诱发工程灾害的风险评估与预警控制平台，提出了地质灾害的控制措施。.研究成果揭示了滨海软土地区深大基坑群施工对环境影响的作用机理，为滨海软土地区地下空间开发中重大工程地质环境灾害效应分析与监测预警控制提供科学依据，并成功应用于上海地区的多项重大工程。.本项目共培养毕业博士11人、硕士8人；发表期刊论文68篇，其中SCI期刊论文42篇；申请发明专利26项、软件著作权8项。