冻土地区公路路基的冻胀融沉机理及防控措施研究

Study on the Mechanism of Frost Heave and Thaw Settlement and Prevention and Control Measures for Highway Subgrades in Permafrost Regions

摘要: 冻土地区公路路基常面临冻胀融沉病害，导致路面开裂、沉降、翻浆等问题，严重影响通行安全与使用寿命。为揭示冻胀融沉内在机理并提出针对性防控技术，本文通过理论分析、室内试验与现场监测相结合的方法开展系统研究。首先明确冻土的物理力学特性及冻融循环对路基土体的影响；深入分析冻胀(水分迁移–冰晶体生长–土体膨胀)与融沉(冰层融化–结构破坏–承载力下降)的核心机理及关键影响因素(土质、含冰量、温度变化、地下水)；设计3组不同参数的路基土试件(粉质黏土、含砂黏土、砂砾土)进行冻融循环试验，测试力学性能退化规律；最后提出“源头控制–过程调节–工程加固”的三级防控体系，并结合青藏公路某路段工程案例验证措施有效性。研究表明：粉质黏土路基冻胀率达12.3%，融沉系数为0.085，是最易发生病害的土质；采用“换填非冻胀土 + 土工格栅加固 + 保温板防护”复合措施后，路基冻胀量控制在5 mm以内，融沉量≤8 mm，满足规范要求。本文成果可为冻土地区公路路基设计、施工及病害治理提供理论支撑与工程参考。

Abstract: Highway subgrades in permafrost regions are often plagued by frost heave and thaw settlement diseases, leading to problems such as pavement cracking, settlement, and mud pumping, which seriously affect traffic safety and service life. To reveal the intrinsic mechanism of frost heave and thaw settlement and propose targeted prevention and control technologies, this study conducts a systematic research using a combination of theoretical analysis, laboratory tests, and on-site monitoring. Firstly, the physical and mechanical properties of permafrost and the impact of freeze-thaw cycles on subgrade soil are clarified; the core mechanisms of frost heave (moisture migration - ice crystal growth - soil expansion) and thaw settlement (ice layer melting - structural damage - bearing capacity reduction) as well as key influencing factors (soil type, ice content, temperature change, groundwater) are analyzed in depth. Three groups of subgrade soil specimens with different parameters (silty clay, sandy clay, gravel soil) are designed for freeze-thaw cycle tests to study the degradation law of mechanical properties. Finally, a three-level prevention and control system of “source control - process regulation - engineering reinforcement” is proposed, and the effectiveness of the measures is verified through an engineering case of a section of the Qinghai-Tibet Highway. The results show that the silty clay subgrade has a frost heave rate of 12.3% and a thaw settlement coefficient of 0.085, making it the most disease-prone soil type. After adopting the composite measures of “replacement with non-frost-heaving soil + geogrid reinforcement + insulation board protection”, the frost heave of the subgrade is controlled within 5 mm, and the thaw settlement is ≤8 mm, which meets the specification requirements. The results of this study can provide theoretical support and engineering reference for the design, construction, and disease treatment of highway subgrades in permafrost regions.