Active Control Method Of Excavation-induced Pile Lateral Deformation By Capsule Grouting Technology

The control methods of pile lateral deformation induced by adjacent excavation focused more on passive control methods like strengthening the supporting system and active control methods like conventional Tube-a-Manchette(TAM)grouting rather than capsule grouting technology(CGT),which could achieve millimeter level and fine control.CGT can precisely control the stress and displacement of soil and structure in the target area by accumulating slurry inside the capsule and pushing the capsule to expand to the external soil.Based on field trail and numerical simulation,the technology,mechanism and strategy of using CGT to control pile lateral deformation induced by adjacent excavation were studied in this paper.In technology research,capsule design,slurry design and grouting equipment and steps were introduced.And based on a foundation pit engineering in Tianjin,the world’s first excavation-induced pile lateral deformation field trail proved that CGT could control the pile lateral deformation.Besides,CGT could control the influence area more accurately and disturb adjacent soil more slightly when compared with TAM.In mechanism research,A finite element model was established to analyze the influence transfer mechanism of CGT on adjacent soil and structure through deformation and internal force.After that,parameters related with pile foundation,foundation pit and grouting were selected to analyze the influence on maximum displacement of pile and grouting recovery rate.The lateral displacement of pile foundation after grouting presents a "bow shape" along the depth,and the extreme position is determined by the depth of excavation and the depth of grouting.In strategy research,a comprehensive effect evaluation system of CGT was established to evaluate the pile deformation and internal force of adjacent structure.And the active control strategies of CGT under different pile head states and pile group state were compared,which concluded that there are optimal strategies for CGT,and the number of bags in pile group state has significant influence on the control effect.In addition,the control effects of real-time grouting and single grouting on pile lateral deformation were compared,and the real-time grouting strategies under different working conditions were studied to verify that real-time grouting could effectively control the deformation range of pile foundation during construction.