不同换填材料对多年冻土地区公路路基温度状况影响的数值模拟

Numerical Simulation of Influence of Different Replacement Materials on Highway Subgrade Temperature in Permafrost Area

为解决气候变暖、施工扰动引起的多年冻土区公路路基融沉失稳问题,探索适用于东北地区多年冻土的路基结构,该研究提出采用大粒径块石层换填地基多年冻土层的新型路基结构对路基变形进行改善,并在京漠公路瓦拉干至西林吉段工程中进行实践。对比不同换填材料对路基热稳定性的影响,将换填角砾路基结构作为对照,建立考虑水分相变和空气自然对流换热的传热模型,对2种路基交工后20 a内的温度状况进行数值计算。结果表明,2019—2039年,换填块石路基和换填角砾路基下多年冻土上限分别降至-4.43 m和-6.51 m,融化夹层面积分别增加至44.48 m^(2)和72.53 m^(2)。换填块石路基比换填角砾路基下多年冻土上限更高,融化夹层更薄。而且换填块石路基下多年冻土上限始终位于块石层内,由于块石颗粒间能够形成良好的嵌锁结构,从而有效抵御地基不均匀变形,因此该路基结构可以有效减小路基沉降量。然而,换填角砾路基下多年冻土上限已经进入中风化安山岩层,而且角砾颗粒间不能形成良好的嵌锁结构,也无法抵御地基不均匀变形,由此判断换填角砾路基的融化沉降量较大,该路基结构不适用于东北多年冻土区。该研究从路基热稳定性角度分析和验证了换填块石路基结构对改善路基沉降的有效性,为解决东北多年冻土区公路路基融沉失稳问题提供了重要参考。

In order to solve the problem of thawing settlement instability of highway subgrade in permafrost regions caused by climate warming and construction disturbance,and explore the subgrade structure suitable for permafrost in Northeast China,this study proposes to improve the subgrade deformation by using a new type of subgrade structure with large-size block stone layer to replace the permafrost layer of the foundation,and has carried out the practice in the Walagan-Xilinji section of Beijing-Mohe Highway.By comparing the effects of different replacement materials on the thermal stability of subgrade,and taking the structure of the replacement breccia subgrade as a comparison,a heat transfer model considering the water phase change and the natural air convection heat transfer is established,and the temperature conditions within 20 years after the handover of the two kinds of subgrade are numerically calculated.The results show that from 2019 to 2039,the permafrost table s under replacement block stone subgrade and replacement breccia subgrade will be reduced to-4.43 m and-6.51 m,respectively,and the areas of thawing interlayer will be increased to 44.48 m^(2)and 72.53 m 2,respectively.The permafrost table of the replacement block stone subgrade is higher than that of the replacement breccia subgrade,and the thawing interlayer is thinner.Moreover,the permafrost table under the replacement block stone subgrade is always located in the block stone layer.Because the block stone particles can form a good interlocking structure to effectively resist the uneven deformation of the foundation,the subgrade structure can effectively reduce the settlement of the subgrade.However,the permafrost table under the replacement breccia subgrade has entered the moderately weathered andesite,and the breccia particles cannot form a good interlocking structure,nor can they resist the uneven deformation of the foundation.Therefore,it is judged that the replacement breccia subgrade has a large amount of thawing settlement,and the subgrade structure is not suitable for the northeast permafrost regions.From the perspective of subgrade thermal stability,this study analyzes and verifies the effectiveness of the replacement block stone subgrade structure in improving subgrade settlement,which provides an important reference for solving the thawing settlement instability of highway subgrade in the permafrost regions of Northeast China.