能源隧道换热过程中的地层热补给能力研究

Anchorage Mechanism and Field Tests of Prestressed Anchor Cables with Different Anchorage Lengths in Soil-Rock Composite Strata

为研究不同水文地质条件下能源隧道的长期换热性能,对年周期、日周期以及年周期与日周期叠加3种换热方案下,能源隧道周围地层的温度变化情况进行了数值模拟分析。数值模型中考虑了地层、衬砌及空气的温度场以及地下水渗流及空气流动。为方便计算,将换热管等效为面热源,通过调节其换热效率模拟能源隧道的不同运行方案。计算结果表明:1)地下水渗流速度越大,地层的热补给能力越高,地层温度受能源隧道的影响范围也越大;2)无论是年周期还是日周期运行方案,地下水渗流速度越大,隧道周围的温度场越快达到稳定状态;3)与年周期换热方案相比,日周期换热方案虽然不能有效提升地层的热补给能力,但是可以显著减小能源隧道对地层温度的影响范围;4)可通过优化制冷或采热的功率及持续时间,使1个年周期后能源隧道周围地层温度恢复至初始状态,从而提高能源隧道的运行效率,降低能源隧道对地层环境的影响。

To obtain the optimal anchorage length for soil-rock composite strata,indoor tests,numerical simulations,and engineering tests are conducted to investigate the working conditions for two types of anchorage lengths(12 m and 8 m).The results show the following:(1)The peak shear stress transfers from the beginning to the end of the anchorage section under the tension load,while the peak shear stress is low and the axial force decay rate is high in the anchorage in clayey soil gravel sandstone layer.(2)With the increase of tension load,the anchorage section in clayey soil gravel sandstone layer gradually transforms from tensile stress zone to compressive stress zone,the transfer rate of stress to the depth is low,and the anchorage solid has the characteristics of poor resistance to external load and high deformation.(3)The anchor cable axial force can be divided into three evolutionary stages:loss of prestress,rise,and fluctuation,and when the anchorage section passes through the clayey soil-gravel sandstone layer,the prestress is lost in the fluctuation stage,and the prestress is non-uniformly distributed in different directions.(4)It is recommended to avoid anchoring in the soil-gravel sandstone layer when the anchor cable passes through the soil-rock composite strata.