通风管-大孔隙块体类复合冷却路基的幅宽热效应研究

Considering the significant heat absorption of wide asphalt pavement and the narrow, crowded Qinghai-Tibet Engineering Corridor, choosing an integral or two separated embankments is an primary issue for embankment construction of the planned Qinghai-Tibet Expressway (QTE) in permafrost regions. The project will take the embankment cooled by ventilated ducts and block layer with large porosity as study object. Currently, the cooling effect of this combined cooling method has been validated by previous studies when used for expressway constructed with separated embankment. In this project, a test project of expressway embankment at Beiluhe Basin and a large-scale in-situ mode test will be used to reveal the influence of embankment width on “ventilation effect” and “thermal semi-conductor effect” of this combined cooled embankment. Then, through numerical simulations, the influence of embankment width on heat convection intensity of the combined cooled embankment, level and shape of underlying permafrost table, temperature field condition and heat budget of subgrade soils will be revealed. With the results of in-situ tests and numerical simulations, thermal effect of embankment width on the combined cooled embankment and subgrade soils will be quantified, and long term thermal stability of the separated embankment and the integral embankment will be systemically evaluated. Finally, structures for enhancing ventilation effect will be proposed to weaken the thermal effect of embankment width. And, the feasibility and solution of an integral embankment for the planned QTE will be discussed. The research achievement will provide a scientific basis from long-term embankment thermal stability for the planned QTE on choosing an integral embankment or two separated embankments.

面对宽幅沥青路面“聚热效应”和狭窄拥挤的青藏工程走廊，分离式、整体式路基选择是拟建青藏高速冻土路基工程面临的首要问题。本项目以目前在分离式条件下表现良好的通风管-大孔隙块体类复合冷却路基为研究对象，基于项目组已有高等级公路试验示范工程、结合现场大尺度模型机理试验，揭示路基幅宽对这类复合路基“通风效应”和“热半导体效应”的影响机制与程度。基于现场监测，建立复合路基降温效果数值预测模型，研究幅宽对路基体对流换热强度与分布、人为冻土上限位置与形态、地温场分布特征、冻土地基热量收支的影响与程度，揭示并量化由路基幅宽引发路基（路堤-地基）热效应，进而系统评价分离式、整体式复合路基长期热稳定性。探索通过强化通风效应，以补偿上述路基幅宽热效应，回答整体式路基能否抵御宽幅沥青路面强烈吸热效应与气候变暖的双重影响这一问题。研究成果将为拟建青藏高速公路分离式、整体式路基选择从路基热稳定性角度提供科学依据。

面对青藏高速公路建设这一国家重大需求，围绕整体式、分离式通风管-大孔隙块体类复合冷却路基的长期效能对比，从整体式、分离式周边流场、通风管内风速、风温的沿程分布、以及整体式、分离式路基长期热状况三个角度出发开展研究工作，利用了包括现场监测、大型风洞试验、数值模拟等研究手段。取得的主要研究进展包括：1）在高海拔多年冻土区，高速公路路基内通风管内气温较环境气温高0.2~1.1°C，进口气温较出口气温高1°C左右。通风管内风速与环境风速的季节变化基本同步，管内风速的量值约为环境风速的28%；当环境风向与通风管路基垂直且较为稳定时，环境风速与通风管内风速呈现良好的线性关系，而当环境风速显著变化时，环境风速与通风管内风速相关性差；通风管管内风速随通风管管径的增加呈抛物线形式增加，当管径超过0.6m后，管内风速不再随管径的增加而明显提升；通风管管内风速基本不受外伸长度的影响，但随埋设高度的增加基本呈线性增加趋势；2）高海拔冻土区公路整体式路基周边流场可分为坡前减速区、路基上部加速区、坡后扰动区，其中坡前减速区水平范围约为1.8~2.5倍路基高度，坡后扰动区水平范围约为11~13倍路基高度；其中坡后扰动区可分为坡后低速回流区和消散恢复区，前者约为2~4倍路基高度，后者约为10倍路基高度；对于分离式路基而言，当两幅间距大于5倍前幅路基高度时，前后幅路基间相互影响不再显著；3）对于通风管-大孔隙块体类冷却路基，整体式路基存在聚冷效应，冻土地基的总放热量基本成倍增加，由分离式路基条件下69674.5 J/h增加到整体式的116046.2 J/h，增幅达到1.67倍。运营50年后，整体式路基聚集的冷能储量是分离式路基的2.6倍，且路基温度场的对称性即人为上限分布形态更加平整。基于项目研究，发表论文29篇，其中SCI/EI收录21篇，申请专利4项，等级软件著作权2项。获得甘肃省科技进步一等奖1项。