强震下液化场地流滑运动机理及其对地铁地下结构的影响研究

As far as the earthquake damages caused by liquefaction-induced flow in violent earthquake are concerned, this research project will be studied by using Dynamic Hollow Cylinder Apparatus, refined numerical simulation technology, different dimension shaking table tests and so on. Firstly, the dynamic behaviors of liquefied sand during the whole loaded process are studied by two kinds of tests. Based on the theories of fluid dynamics and the elastoplasticity mechanics, the coincidence constitutive model and the failure criterions used to model the main deformation properties of liquefied soil will be advanced. Secondly, the behaviors of liquefaction-induced flow and slip of surface soils and nonlinear dynamic contact on the interacted surfaces between different materials are studied and its' numerical simulation techniques used are also analyzed. Based on the fluid-solid coupling calculated method by using fluid dynamics calculated method and the finite-elements method, a large refined 3-D numerical simulation platform will be advanced and used to model the complicated dynamic interaction system which is comprised by large-scale liquefied site and subway underground structures. Based on this numerical simulation platform, the liquefaction-induced flow, slip and failure of liquefied site can be simulated effectively and accurately. At the same time, the shaking table testing technologies to model the liquefaction-induced flow of liquefied site are also studied. At last, by using the methods of theoretical analysis and numerical simulation and large-scale shaking table tests, the liquefaction-induced flow mechanism of liquefied site is analyzed in detail, and then the theoretical analysis model and calculated method are studied to model the liquefaction-induced flow and dynamic failure of liquefied site. At the same time, the damage mechanism of subway underground structures caused by liquefaction-induced flow are also analyzed in detail, and then the earthquake disaster control methods will be also studied to alleviate the earthquake damages of subway underground structures. As a result, the research results achieved in this research project will provide not only new theoretical model but also calculated method used to study on the liquefaction-induced flow and failure of liquefied site. At the same time, the new forecasting methods and earthquake disaster reduction technologies will be also advanced for the seismic safety of subway underground structures.

针对强震诱发砂土液化流滑运动所造成的严重震害，本项目拟通过室内试验、精细数值模拟和模型试验等研究手段。首先，开展土体液化全过程动力学特性的研究，以流体动力学结合弹塑性力学的方法，建立土体液化全过程的一致性本构模型及其破坏准则；其次，基于对土体液化后流动、层间滑移、界面动力接触损伤等特性的研究，用计算流体动力学方法与有限元法的耦合分析方法，建立强震下液化流滑场地与地铁地下结构系统的流固耦合分析模型与大型高效数值仿真分析平台，同时，研究该复杂相互作用系统的振动台模型试验技术；最后，基于多种研究手段，揭示强震下液化场地流滑运动特征及其对地铁地下结构的地震破坏机理与破坏过程，提出液化场地流滑运动的理论分析模型和简化计算方法，并提出相应的地铁地下结构动力灾变控制方法。本研究不仅能为强震下液化场地流滑运动的研究提供新的分析模型和计算方法，同时对地铁地下结构防震减灾的研究也具有重要的科学意义和应用价值。

强地震中，砂土液化大变形及其区域场地失稳与滑移等破坏必将对城市轨道交通隧道和车站结构产生最为严重的威胁。鉴于此，通过理论分析、室内试验、数值模拟和模型试验，研究了砂土液化全过程的动力学特性及其能够描述砂土液化前弹塑性变形特性、液化后流动大变形特性的一致性本构模型；同时，揭示强地震中砂土液化所引起的土体大变形及其场地失稳或滑移等地震运动规律、破坏机理和过程；探明了由液化土体大变形所引发的地铁地下结构地震破坏成灾机理及其破坏过程。重要研究成果如下：.（1）基于对动态空心圆柱扭剪试验结果的分析，揭示了新近沉积片状颗粒砂土的液化大变形特征（剪应变幅达到100%），给出了不同的初始应力状态下土体液化全过程的动力学特征（抗液化强度、剪应变率、表观黏度等变化规律），给出了饱和土体液化全过程的模量弱化过程及其力学描述方法。研究结果进一步揭示了砂土液化大变形机理，发展了砂土液化大变形的物理描述方法。.（2）基于砂土液化前和液化后的不同物理特性，建立了砂土液化大变形的数值计算方法，基于大型并行计算集群平台，建立液化流滑运动场地-地铁地下结构系统的流固耦合三维数值分析模型和快速算法的大型高效数值仿真分析平台。这一研究成果发展了砂土液化大变形的数值计算理论与方法。.（3）基于建立的大型高效数值仿真分析平台和模型试验，实现了场地流滑运动的数值模型模拟（滑动面的位置确定、流滑距离的计算和场地侧移分布特征等），揭示了不同地震动激励下和不同地形地质条件下液化场地流滑运动特征、破坏机理及其过程。.（4）基于建立的大型高效数值仿真分析平台和大型振动台模型试验，揭示了液化土体大变形及其场地流滑运动对地铁地下结构（区间隧道、大型换乘车站、隧道与车站连接部位等）的地震破坏机理及其破坏过程，以及不同场地上地铁地下结构的抗震性能水平及其评定方法。相关研究成果为地铁地下结构的地震反应、抗震性能和地震安全性评价提供合理有效地分析方法。