Evaluating dynamic responses of pavement structures with pipeline trench backfilled with foamed lightweight soil
Traditional granular materials such as soil,sand,and gravel are often used to backfill the pipeline trenches under municipal roads.Due to the limited space of the trench,compaction degree is difficult to meet design requirements.It is thus susceptible to pavement cracking or collapse under traffic load or pipeline damage.Foamed lightweight soil(FLS)is adopted to backfill the pipeline trench for its advantages of light weight,compressive strength,self-compaction,and anti-leakage.The vibration acceleration and dynamic displacement were taken as dynamic response indices,and the field tests of the FLS backfilling test section and the medium sand backfilling test section were conducted to investigate the dynamic response characteristics,respectively.The vehicle loads of the field tests were divided into three types:no load,half load,and full load.Each loading stage was tested at three driving speeds:20 km/h,40 km/h,and 60 km/h,with a total of 9 testing schemes.The field tests results show that the maximum vibration acceleration and dynamic displacement of the FLS backfilling section are 31.93 mm/s2 and 6.23 μm,respectively,while those of the medium sand backfilling section are 35.79 mm/s2 and 6.90 μm,respectively.The peak vibration acceleration and peak dynamic displacement rise with increasing vehicle weight and speed.It is observed that the peak dynamic displacement range of measuring points in the FLS backfilling section only varies between 15.2%～51.0%of that in the medium sand backfilling section when the vehicle weight shifts from no load to full load.Similarly,when the vehicle speed increases from 20 km/h to 60 km/h,the range of peak dynamic displacement of measuring points in the FLS backfilling section is only 16.8%～66.8%of that in the medium sand backfilling section.The attenuation rates of peak vibration acceleration and peak dynamic displacement in the FLS backfilling section are 1.16～1.38 times and 1.15～1.33 times of that in the medium sand backfilling section,respectively.Backfilling with FLS reduces the high frequency and low frequency components of vibration.The FLS backfilling section has a consistent and sturdy overall stiffness and a good vibration reduction effect.The research findings have practical implications for the design and construction of the FLS backfilling pipeline trenches under municipal roads.
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