季节冻土在冻融循环与冲击型荷载协同作用下永久变形机理及分析方法研究

In seasonally frozen regions subgrades are prone to greatly permanent deformation under the freeze-thaw cycle and heavy vehicle dynamic load, which brings the traffic potential risk, while the related research lags behind.For seasonally frozen soil, the disaster-causing mechanism and prevention measures will be investigated under the synergistic effect with frozen-thaw cycle and impact load. The study includes: (1)By in-situ testing, the parameters will be measured such as the dynamic stress, temperature, phase change and the overall stiffness of subgrade soil will be studied for seasonally frozen soil considering the synergistic effect with freeze-thaw cycle and impact load ; (2)For seasonally frozen soil, constitutive model of the permanent deformation will be built under the synergistic effect with frozen-thaw cycle and impact load，in the mean while, the dynamic finite element analysis system will be developed for permanent deformation caused by the synergistic effect ; (3) Through frozen soil dynamic triaxial test and numerical simulation for arbitrary wave input, the coupling effect of freeze-thaw cycle with impact load, and the relationship between this coupling effect and permanent deformation will be investigated for revealing the permanent deformation mechanism ; (4) The defensive measures of subgrade soil will be studied under the synergistic effect with frozen-thaw cycle and impact load, which can providing technological means for road engineering disaster prevention and mitigation and scientific management of transportation.

季节冻土路基在冻融循环及重载车辆动载作用下极易发生大幅度永久变形，带来交通安全隐患，但相关研究滞后。本课题针对季节冻土在冻融循环与冲击型荷载协同作用下致灾机理和防御措施展开研究。主要研究内容包括：（1）对路基土中动应力、温度、相位变化、永久变形及总体刚度等参数进行现场实测，初步掌握季节冻土在冻融循环与冲击型荷载协同作用下永久变形时空分布规律；（2）构建并验证冻融循环与冲击型荷载协同作用下冻土永久变形本构模型，开发两者协同作用下的冻土永久变形动力有限元分析系统；(3）通过任意波输入动三轴冻土试验和数值模拟，研究冻融循环与冲击型荷载间的耦合效应及这种效应与永久变形的关系，揭示永久变形发生机理；（4）研究季节冻土路基在冻融循环与冲击型荷载协同作用下的灾害防御措施。通过研究为道路工程防灾减灾及交通运输科学管理提供技术手段。

本项目以季冻土路基力学特性为研究背景，提出了冲击型车辆荷载的概念，围绕冻融循环和冲击型车辆荷载协同作用展开了一系列专题研究。提出了季冻土路基监测新技术，首次将光纤光栅测试技术引入季冻土路基变形监测中，并对路基在冻融循环及冲击型车辆荷载协同作用下的动态响应进行了为期三年的现场实测；以更符合季冻土路基实际的试验工况，给出了季冻土动模量比、阻尼比计算公式，振陷模型和抗剪强度指标计算公式，为季冻区交通基础设施设计参数选取提供了依据；揭示了冻融循环与冲击型车辆荷载协同作用下路基土永久变形机理，并提出了合理有效的减灾措施；研发了基于低功耗蓝牙技术的季冻土路基温度监测系统和基于ArcGIS的路基土冻胀预警系统，给出了基于FLAC3D的路基动态响应分析方法，为季冻区道路安全评价和防灾减灾提供了有效手段。