Effects of horizontal and three-dimensional reinforcement on frost-heaving and thawing-settlement in seasonally frozen soils
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摘要: 冻胀融沉是季节性冻土区建筑物破坏的主要原因，实际应用表明，土工合成材料加筋路基具有良好的抗冻融循环损伤能力，然而不同加筋形式的有益影响尚未被量化。针对四川阿坝地区典型季节性冻土，开展了水平及立体加筋土冻融循环试验及平板载荷试验，研究了冻融循环对加筋土和未加筋土力学性能的影响，对比了水平加筋及立体加筋土的防冻胀融沉效果。研究发现：水平加筋和立体加筋均可一定程度上抑制土体的冻胀融沉，提高冻融循环后土体的承载力，抑制冻融循环的弱化作用。立体加筋加固效果优于水平加筋。经过5次冻融循环后，水平加筋使冻胀隆起和融化沉降分别减少5%，6%，立体加筋使冻胀隆起和融化沉降分别减少4%，17%；水平加筋对冻融循环土体的承载力和刚度分别提高75%，29%，立体加筋对冻融循环土体的承载力和刚度分别提高388%，40%。Abstract: The frost heaving and thaw-induced settlement is the primary causes of structural damage in the areas with seasonally frozen soils. Practical applications have demonstrated that the roadbeds reinforced with geosynthetic materials exhibit excellent resistance to cyclic frost-thaw damage. However, the beneficial effects of various forms of reinforcement have not been quantified. To address this gap, the freeze-thaw cycle tests and plate-load tests are conducted on soil samples, horizontally or three-dimensionally reinforced, collected from a representative seasonal frozen soil site in the Aba area, Sichuan Province. The effects of freeze-thaw cycle on the mechanical properties of the reinforced soil are compared to those of unreinforced soil. Additionally, a comparative analysis of the mitigation effects of frost-heaving, thawing-settlement and bearing capacity is performed between the horizontally and three-dimensionally reinforced soils. The study reveals that the frost-heaving and thawing-settlement in the soils can be effectively mitigated by both the horizontal and three-dimensional reinforcements. Moreover, these reinforcement methods enhance the post-freeze-thaw bearing capacity of the soils and counteract the weakening effects of freeze-thaw cycles. Notably, the three-dimensional reinforcement demonstrates a superior reinforcing effect in comparison to the horizontal reinforcement. Following five freeze-thaw cycles, the horizontal reinforcement results in a 5% reduction in the frost-heave and a 6% reduction in the thaw-induced settlement, while the three-dimensional reinforcement yields a 4% reduction in the frost heave and a 17% reduction in the thaw-induced settlement. The horizontal reinforcement enhances the bearing capacity and stiffness of freeze-thaw cyclic soil by 75% and 29%, respectively. In contrast, the three-dimensional reinforcement significantly improves the bearing capacity and stiffness of the freeze-thaw cyclic soils by 388% and 40%, respectively.
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图 3 土工格栅/格室加筋地基示意图
Figure 3. Schematic diagram of geogrid/geocell reinforced foundation
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图 4 冻融循环过程中土体的热电偶布置示意图
Figure 4. Layout of thermocouple in clay sands during freeze-thaw cycle
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图 5 一次冻融循环过程中土工格栅/格室加筋土与未加筋土温度随时间的变化曲线
Figure 5. Temperature evolution of geogrid/geocell-reinforced soil and unreinforced soil with time during one freeze-thaw cycle
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图 7 每次冻融循环后非加筋土和加筋工况下土体的冻胀
Figure 7. Frost-heave of unreinforced and reinforced sands after each F-T cycle
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图 8 不同冻融循环次数加固及未加固地基荷载-沉降曲线
Figure 8. Load-settlement curves of reinforced and unreinforced clay sands with different freeze-thaw cycles
表 1 模型试验组别
Table 1 Details of model tests
试验编号 试验材料 冻融循环次数 温度监测 冻胀监测 平板加载试验 GR-1 未加筋土体 0 否 否 是 GR-2 1 是 是 是 GR-3 5 是 是 是 GR-4 土工格栅水平加筋土体 0 否 否 是 GR-5 1 是 是 是 GR-6 5 否 是 是 GC-7 土工格室立体加筋土体 0 否 否 是 GC-8 1 是 是 是 GC-9 5 否 是 是 
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