多年冻土路基融化沉降过程中应力传递规律研究

In permafrost regions, thaw settlement of permafrost embankment is one of the main reasons leading to embankment damages. The key step to reveal mechanism of these damages is to clearly clarify the law of stress distribution during the process of permafrost embankment thaw settlement. Currently, for lack of systematically theoretical and experimental study on the law of stress distribution, existing theory method cannot meet the needs of practical engineering application. This project will take the Qinghai-Tibet highway as study object to investigate and analysis the law of stress distribution through model and in-situ tests; the previously developed 3-D large strain thaw consolidation theory and FLAC numerical platform will be modified by incorporating the Modified Cam-Clay model; through small samples tests results, the applicability of these modification works will be verified and corrected; by practical application of the modified theory and numerical platform in cases of model and in-situ tests, the law of stress distribution during permafrost embankment thaw settlement will be systematically studied. The research achievement will provide an essential technology support for the construction maintenance and damage prevention in permafrost regions engineering.

在多年冻土地区，冻土路基的融化沉降是引起一系列路基病害的主要原因之一。揭示这些工程病害内在机理的关键在于准确掌握冻土融化沉降过程中的应力传递规律。目前，由于对这一过程中应力传递规律缺乏系统的理论和试验研究，致使现有理论方法无法满足实际工程需要。本项目拟以青藏公路为研究对象，通过室内模型试验和野外原位观测分析冻土融化沉降过程中的应力传递规律；结合修正剑桥模型进一步完善和改进申请人前期所建立的三维大变形融化固结理论和FLAC数值模拟平台，并根据小样品试验对其进行验证和修正；在此基础上，将该平台应用于实际工程计算，对比分析模型试验和原位观测结果系统研究冻土路基融化沉降过程中的应力传递规律。研究成果将为多年冻土地区道路设施的维护和病害防治提供可靠科学依据。

准确描述和揭示应力分布和传递规律是进行冻土路基融化沉降预测的重要前提。以往的工作对冻土融化过程中应力的分布和传递规律缺乏系统的理论和试验研究。本项目以青藏公路为研究对象，采用自主研制的冻土低温恒温试验箱和标定装置开展了土压力盒标定工作。使用经过标定的土压力和开展了室内模型试验和野外观测试验，研究分析了冻土路基中应力传递和分布规律。基于申请人前期建立的大变形融化固结数值模拟平台，引入分段插值算法对其进行修正和改进，解决了计算高含冰量冻土地基时出现的不稳定和不收敛问题。通过试验验证表明经过完善的融化固结数值模拟平台能够有效描述不同温度和荷载条件下土体的应力分布和传递规律。研究结果显示路基浅层土体在运营初期完成固结，其有效应力与总应力分布状态基本一致，且分布形态主要取决于地基土层融化区域的形态。同时，融化后土层中的超静孔隙水压力主要集中于融化封面处。这一研究结果表明，多年冻土路基长期运营过程中的持续沉降主要来源于融化峰面处孔隙水压力的消散。