Differential settlement of widened subgrade in cold and high-altitude permafrost regions
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摘要: 为了研究高寒高海拔多年冻土区拓宽路基面层吸热对下伏多年冻土温度与沉降的影响, 建立了基于热力耦合理论的差异沉降计算的有限元模型, 并利用实体工程监测数据对模型进行了修正, 分析了不同季节、不同填高与阴阳坡工况下拓宽侧路基差异沉降分布规律, 确定了多年冻土区最优路基拓宽位置。研究结果表明: 多年冻土区拓宽路基最大融深与沉降均出现在秋季, 10月份的变形最不利, 病害特征最突出, 其中4m填高路基第10年最大差异沉降为16.9cm, 分别为7、1、4月份沉降的1.1、1.4、1.7倍; 差异沉降与路基填高存在正相关性, 当路基填高分别为2、4、6 m时, 10年内路基的差异沉降分别为13.2、16.9、18.1cm; 阴坡侧拓宽路基的温度与沉降变化小于阳坡侧, 在10年内, 阳坡侧拓宽路基底面最大升温为1.3℃, 阴坡侧为0.6℃, 阳坡侧拓宽路基最大差异沉降为16.9cm, 阴坡侧为12.3cm; 即使阴坡侧拓宽, 差异沉降仍使拓宽路基顶面形成一个斜率为2%~3%的斜坡, 进而使路面产生较大附加应力, 最终造成结构层病害。Abstract: In order to study the influence of heat absorption of widened subgrade surface on underlying permafrost's temperature and settlement in cold and high-altitude permafrost regions, a finite element model computing the differential settlement of widening subgrade based on the thermal-mechanical coupled theory was established and corrected by the monitoring data of practical engineering, the differential settlement distributions under diverse seasons, different filling heights and working conditions at sunny and shady slope sides were studied, and the optimal widened location of subgrade in permafrost regions was determined. Research result shows that the maximum melting depth and settlement of widened subgrade appear in autumn, October is most unfavorable for subgrade settlement, and disease characteristics are remarkable. When the filling height of subgrade is 4 m, the maximum differential settlement of subgrade is16.9cm and 1.1, 1.4, 1.7times larger in October than in July, January and April within 10 years. Within 10 years, when the filling heights of subgrade are 2, 4 and 6 m respectively, thedifferential settlements are 13.2, 16.9 and 18.1 cm respectively, so the differential settlement increases with the increase of filling height. Within 10 years, the maximum rising temperature of subgrade is 1.3 ℃ at sunny slope side and 0.6 ℃ at shady slope side, the maximum differential settlement of subgrade is 16.9cm at sunny slope side and 12.3 cm at shady slope side, so the temperature and settlement of widened subgrade change smaller at shady slope side than at sunny slope side. Even widening subgrade at shady slope side, the differential settlement of subgrade still results in a 2%-3% slope at the top of subgrade, the slope will result in the great additional stress of pavement, so that the diseases of pavement structure occur.
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图 8 冻土上限实测值与计算值对比
Figure 8. Comparison between measured and calculated values of permafrost table
图 9 沉降实测值与计算值对比
Figure 9. Comparison between measured and calculated values of settlement
图 12 不同填高拓宽路基温度分布
Figure 12. Temperature distributions of widened subgrades with different filling heights
图 13 不同填高拓宽路基沉降分布
Figure 13. Settlement distributions of widened subgrades with different filling heights
图 14 不同填高阴阳坡侧拓宽路基温度分布
Figure 14. Temperature distributions of widened subgrades with different filling heights at sunny and shade slopes sides
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