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