地下工程降水开挖对区域地层变形作用机制的多尺度耦合分析

Excavation-induced environmental effect develops from engineering scale to geological scale due to the long-term and large-area dewatering and deep excavation. The multi-scale analysis method for dewatering and deep excavation simulation is able to ensure the excavation stability and study the deformation behavior of regional strata simultaneously. In this proposal, a multi-scale analysis method is proposed and used to study deformation behavior of regional strata subjected to deep excavation and pumping. Research contents are listed as: multi-scale modeling method for regional strata deformation is constructed based on concurrent multi-scale theories; constrained relations are built up to connect different multi-scale subdomains and the corresponding multi-scale mechanical equations and seepage equations are derived; mixed time step algorithm is proposed to solve the seepage equations; and small strain stiffness constitutive model for soft clay is presented based on perfect elasto-plastic theory, which is used to perform multi-scale analysis of regional strata deformation subjected to deep excavation and pumping in confined aquifer; and the proposed multi-scale method is used to study the deformation mechanism of the regional strata based on a deep excavation project.; the effect of the engineering geology and waterproof curtain are analyzed; based on the numerical results and field data, the mechanism of the regional strata response due to dewatering and deep excavation. Further accomplishment will be of great benefit to deformation analysis theories and methods of stratum, and provide instructions for control and evaluation of engineering geology safety.

大范围长周期的降水和开挖使得深基坑工程的环境效应从工程尺度逐渐向地质尺度发展，采用多尺度耦合分析方法模拟基坑承压水降水和开挖过程，可以在确保基坑工程安全的同时掌握区域地层环境的变形特性。本项目以软土地区深基坑为研究对象，通过多尺度耦合数值分析方法研究，探讨深基坑降水开挖对区域地层变形的作用机理。基于并发多尺度构造原理,建立的深基坑地质模型及不同尺度域间的约束关系，推导多尺度耦合的力学和渗流控制方程；制定时间步长多尺度计算流程,实现耦合模型的混合时步高效算法，形成融合土体小应变本构的多尺度耦合分析方法；采用多尺度耦合分析方法系统研究地质条件、结构形式等因素对地层变形的影响规律，结合现场测试数据，揭示深基坑降水开挖耦合作用下区域地层工程结构的多尺度相互作用机制及变形特性。项目研究有助于完善深基坑诱发的区域地层变形理论和分析方法，为城市工程地质安全评价和控制提供科学依据。

大范围长周期的降水和开挖使得深基坑工程的环境效应从工程尺度逐渐向地质尺度发展，采用多尺度耦合分析方法模拟基坑承压水降水和开挖过程，可以在确保基坑工程安全的同时掌握区域地层环境的变形特性。本项目以软土地区深基坑为研究对象，采用理论推导，数值模拟，现场测试等方法，建立了基于桥域耦合的几何多尺度耦合分析方法，提出了考虑土体小应变刚度特征的力学本构模型，建立了考虑开挖与降水耦合作用的深基坑施工数值模型，模拟深基坑施工全过程，获得了降水与开挖联合作用下的深基坑受力变形特性。通过系统参数研究，阐明了深基坑降承压水对围护结构和地层变形的影响规律，提出了围护结构水土压力分布模式和地面沉降简化预测方法。研究成果发表SCI期刊论文18篇、EI期刊论文6篇，获得授权发明专利1项。项目研究有助于完善深基坑诱发的区域地层变形理论和分析方法，为城市工程地质安全评价和控制提供科学依据。