炭质泥岩路堤动力湿化变形及损伤失稳机理研究

The regions of carbonaceous mudstone widely distributed , use it for embankment filling is unavoidable, vehicle dynamics and rain infiltration will cause subsequent collapse and strength degradation of embankment filling materials. although targeted prevention measures were taken during fill of embankment, the research of dynamics- wetting deformation and degradation mechanism still lack, which causes the unstability of the carbonaceous mudstone embankment is often happened. .The project is aimed at this problem to carry out the following work: firstly, based on the filling index design model of carbonaceous mudstone embankment to analyzes the moisture migration and deformation characteristics under the influence of dynamics- wetting conditions.; Secondly, combined with nondestructive testing technology and triaxial test, based on CT damage concept,carry out the research of Strength degradation mechanism and dynamics-weting damage constitutive model of carbonaceous mudstone under dynamics-weting conditions. At the some，Based on Hoek-Brown criterion, the Mohr-Coulomb strength indirect solution is derived which damage characteristics can be considered. Establish carbonaceous mudstone strength calculation method which dynamics-weting damage can be considered, design of carbonaceous mudstone embankment stability calculation process; Finally, establish embankment stability evaluation system, put forword embankment stability control method under dynamics-weting conditions. The results of the project are helpful to improve the construction technology of the durable subgrade and prolong the service life of the subgrade.

在炭质泥岩广泛分布地区，将其用于路堤填筑不可避免，但在车载动力及雨水渗入作用下极易造成填料的后续崩解及强度劣化。虽在填筑时采取了必要防范措施，但目前对炭质泥岩填料的动力湿化变形及劣化机理尚缺乏研究，导致炭质泥岩路堤失稳现象时有发生。.本项目针对该问题，开展了以下工作：首先依据路堤填筑指标设计路堤模型试验来对炭质泥岩路堤在动力-湿化影响下的变形及水分迁移特征进行分析；其次将无损检测技术与三轴试验结合，引入CT损伤概念，开展动力湿化条件下的强度劣化机理及动力-湿化损伤模型的研究。同时，基于Hoek-Brown准则，推导能考虑损伤特征的Mohr-Coulomb强度等效间接解法，建立能考虑动力及湿化损伤的炭质泥岩强度计算方法，设计合理的炭质泥岩路堤稳定性计算流程。最后，建立路堤稳定性评价体系，提出动力-湿化条件下的路堤失稳机理。研究成果对完善我国耐久性路堤建造技术具有重大的经济和社会效益。

炭质泥岩分布广泛，具有强度低、遇水易崩解、风化速率快的特点。在材料贫乏地区采用充分崩解炭质泥岩作为路堤填料势在必行，现有预崩解炭质泥岩路堤在湿热环境与车辆动荷载的长期作用下常出现较大变形，甚至发生整体失稳。本研究对预崩解炭质泥岩物理力学性质、干湿循环与动荷载作用下应力应变特征及其本构模型、考虑干湿循环与动力损伤效应的路堤稳定性进行了系统研究，具体研究工作如下：.(1) 通过开展基本物理力学性质试验，得到了预崩解炭质泥岩天然含水率、颗粒分布曲线、不均匀系数、曲率系数、塑限、液限、塑性指数、最佳含水率、最大干密度等路用性能指标，建立了不同压实度预崩解炭质泥岩土水特征Van-Genuchten模型。. (2) 预崩解炭质泥岩抗剪强度、同一轴向应变所对应的偏应力与压实度、围压成正比，与体积含水率、干湿循环次数成反比，同一轴向应变所对应的侧向应变与压实度、围压成反比，与体积含水率、干湿循环次数成正比。预崩解炭质泥岩粘聚力、摩擦角与压实度成线性正相关，与干湿循环次数成双指数负相关，体积含水率越大，粘聚力越小，摩擦角基本不变。.(3) 提出了可以描述预崩解炭质泥岩轴向应变、侧向应变与动荷载作用次数之间关系的永久变形预估模型。.(4)在分析预崩解炭质泥岩应力应变特征的基础上，推导了基于对数函数的非线性本构模型，编写了对数本构模型数值计算程序，验证了数值计算程序的正确性，非线性对数本构模型拟合预崩解炭质泥岩应力应变曲线的效果显著优于邓肯-张模型。.(5)降雨开始后，路堤坡面附近土体基质吸力变化规律可以归纳为基本稳定、快速降低、缓慢降低与持续升高四个阶段。.(6)移动荷载作用下，同一时刻，水平方向动位移值、动应力值自车辆荷载移动路径向两侧逐渐减小，竖直方向动位移值、动应力值从上往下依次减小，动应力的消散具有一定迟滞效应。.(7)提出了一种可以考虑干湿循环与动力损伤效应的路堤稳定性分析方法，并采用该方法对降雨入渗与车辆荷载作用下预崩解炭质泥岩路堤稳定性进行了数值计算。