泡沫轻质土和砂土回填管道沟槽动力响应数值模拟对比分析

Comparative analysis of numerical simulation of dynamic response of foamed lightweight soil and sand backfill pipeline trench

市政道路下覆管道回填区采用砂土等散体材料回填时,控制压实度是施工的关键技术难题之一。引入泡沫轻质土作为管道沟槽回填区材料能较好地解决回填压实度低的问题。为了研究回填管道沟槽泡沫轻质土的动力特性,结合某市政道路回填段行车激励现场试验,沿行车线路横向路面布设8个监测点,建立管道-回填区-路基路面三维动力模型,并施加不同工况下的三轴货车行车荷载激励,数值模拟结果与现场监测点实测数据对比验证了模型的可行性。运用此模型对泡沫轻质土、砂土回填区段的路基路面、管道外壁动力响应及路基工作区深度展开对比分析。结果表明:1)泡沫轻质土回填区沿深度方向动应力峰值衰减率、振动加速度衰减率分别为砂土回填区段的1.63~1.93倍及2.13~3.7倍。2)车重由空载变为满载时,泡沫轻质土回填区和砂土回填区管顶动应力峰值分别增加18.03 kPa和17.86 kPa,说明在回填区上行驶重型车辆时会导致埋地管道振动显著增加。3)泡沫轻质土、砂土回填区管顶和靠近行车一侧动位移峰值比例分别为1.31、1.96,泡沫轻质土回填区管道外壁动位移峰值分布较砂土回填区更加均匀。4)采用泡沫轻质土回填时路基动敏感区和动影响区深度分别为砂土回填的0.68~0.78倍、0.77~0.79倍,对路基稳定性有利。研究结果可为泡沫轻质土在市政道路管道沟槽回填中的相关应用提供参考。

Ensuring high quality compaction of backfill is one of the key technical difficulties in the process of backfilling pipeline trenches under municipal roads,especially for sand and other granular materials.The foamed lightweight soil has been investigated to explore the possibility of a potential backfill material with higher compaction degree.In order to study the dynamic characteristics of foamed lightweight soil in backfill pipeline trench,based on the field test of driving excitation in the backfill section of a municipal road,eight monitoring points were arranged along the transverse pavement of the driving line.A three-dimensional dynamic model of pipeline-backfill area-subgrade pavement was established with the driving load excitation of a three-axis truck under different working conditions.The numerical results were compared with measured data through field monitoring.It was verified the feasibility of proposed model.The dynamic responses of subgrade and pavement,pipeline outer-wall,and subgrade working depth of the section backfilled with foamed lightweight soil and sand were further investigated by proposed model.The results are shown as follows.(1)The attenuation rate of the peak dynamic stress and the attenuation rate of the vibration acceleration along the depth direction of foamed lightweight soil backfill area are respectively 1.63~1.93 times and 2.13~3.7 times that of sand backfill area.(2)When the vehicle capacity rises from unladen to fully laden,the peak dynamic stress of pipeline top increased by 18.03 kPa for backfilling foamed lightweight soil,and 17.86 kPa for backfilling sands,which indicates that the vibration of buried pipelines will make a significant increase with heavy vehicle loads.(3)The peak ratios of dynamic displacement at the top of the pipe and near the driving side in foamed lightweight soil and sand backfill area are 1.31 and 1.96 respectively,so the peak dynamic displacement of the outer wall of the pipe in foamed lightweight soil backfill area is more uniform than that in sand backfill area.(4)When foamed lightweight soil is backfilled,the depth of the dynamic sensitive and affected zone of the subgrade is 0.68~0.78 times and 0.77~0.79 times that of the sand backfill,respectively,which is beneficial to the stability of the subgrade.The research results can provide reference for application of foamed lightweight soil in the backfilling of municipal road pipeline trenches.