Correlation Analysis Between the Treating Depth of PVD and the Subsidence of Soft Ground Foundation of Expressway

The quality of pre-investigation and other reasons would lead to the disagreement between the depth of prefabricated vertical drain(PVD) and actual soft ground foundation. All these factors would have a seriously bad effect on the subsidence and the stability of soft ground foundation. The author combines the Suining-Ziyang-Meishan expressway project, detailedly analyses the correlation between different depths of PVD and actual soft ground foundation based on observation settlement data. The results shows: Before the limit fill height(LFH), with load increases, the depth of PVD has little effect on subsidence rate, the curve of PVD depth-subsidence rate is approximately linear; when backfilling height exceeds the LFH, the closer depth of PVD is to actual depth, the more obvious soft foundation reinforcement effect is, the larger rate and value of subsidence are. However, when PVD depth is 1m deeper than the actual, subsidence rate decreases. In addition, according to the difference of observation total settlement and theoretical calculation settlement due to the difference between PVD depth and actual, adjust preloading period to meet the requirements of pavement construction and post-construction settlement.