Long-term Deformation Of Elevated Road Under The Effect Of Deep Groundwater Recharge

Elevated road is an important part of traffic network in Shanghai. The safe operation of elevated road is a guarantee for city development. Elevated road in Shanghai is almost located in the city center where land subsidence is serious. Artificial recharge in deep strata is an effective method to prevent land subsidence, and make the deep strata upheave to some extent. The pile foundations of elevated road are relative deep so that the deformation of deep strata will greatly affected the elevated road.In this paper, a long-term measurement scheme is carried out to record the deformation of the Middle Ring Elevated from 2007 to 2012 and the interaction between regional land subsidence and elevated settlement is analyzed. The results are as follows:(1) The deformation of Middle ring elevated is mostly affected by deeper strata which lie below the pile foundation. The settlement tendency matches the land subsidence well, and the differences depend on geological condition and foundation type. Elevated settlement and land subsidence is the most serious in ⑥ absent area, and the most slightly in normal area.(2) Through the numerical analysis, the impact of groundwater recharge on elevated settlement is identified, and the settlement characteristic of elevated road is discussed based on the seasonal change of groundwater recharge volume. The shallow strata consolidate and settle under the ground surface load, and the deep strata upheave gradually. The elevated road settles at first and then upheaves to some extent under the interaction effect of recharge load and ground surface load. The long-term settlement of pile foundation is mainly influenced by deep strata.(3) Relevant parameters are analyzed to determine how ground water recharge impacts the elevated road settlement. Geological condition, well location, well depth, recharge volume are all considered. Based on those analyses, basic rules of how deep recharge affect elevated deformation and land subsidence is obtained. With the increase in well depth, recharge volume, foundation depth and the decrease in horizontal distance, the impact of ground water recharge is more and more obvious, and make the elevated piles upheave gradually.