Post-grouting Technology Of Bored Piles And Engineering Application Research In The Tianjing Area

Tianjin belongs to the area of deep soft soil development. Building high-level,high-rise buildings and heavy structures typically requires the foundation of bored pileswhich can provide the very large vertical bearing capacity and the large horizontal bearingcapacity. Although traditional bored piles have many advantages, but due to the adoptionof slurry-supported pore forming construction technology, it causes some defects such assedimentation on the bottom of piles, mud around shaft and the strength reduction of soilaround the pile. Because of these defects, the pile end and pile shaft resistance can not beexerted sufficiently. Post grouting technology not only retains the advantages of traditionalbored piles, but also makes up the defect and deficiency caused by its constructiontechnology. It can effectively improve the bearing capacity of bored piles, reduce thesettlement which can shorten the pile length, reduce the pile diameter and the amount ofcloth pile. So the post grouting technology of bored piles has a broad application prospectin Tianjin area.This paper introduces the development of present situation, application scope of thepost grouting technology of bored piles and the general situation of the engineeringgeology in Tianjin area, summarizes the defect and deficiency of traditional bored piles andthe functions and advantages of the post grouting technology of bored piles.Then themechanism of the post grouting technology to improve the bearing capacity of bored pilesis analyzed from two aspects of mechanics and chemistry. On this basis, this paperintroduces the estimation methods of the post grouting technology of bored piles bearingcapacity of two kinds of specification in detail. At the same time, calculation principle andcalculation results of two kinds of methods are compared and analyzed.The paper elaborates the whole process of bearing capacity estimation of the pilesoutside of the foundation, the post grouting construction, field static load test of piles,engineering optimization design and static load detection by the application example of the tip post grouting technology of bored piles of high-rise residential building in the project ofthe villagers resettlement housing(North Block)in Wang dingdi village Xiqing District Tianjin city. It focuses on the construction technology of the post grouting technique ofbored piles and the post grouting equipment, devices, grouting materials, the provisionsand calculation method of grouting parameter are expounded in detail. Then it Summarizesthe quality assurance measures of the construction technology of the post groutingtechnique of bored piles, analyzes the common problems of the construction technologysuch as the jam of grouting pipe, grouting interruption,stringing pulp,taking slurry, Unableto reach the grouting termination condition and puts forward the corresponding treatmentmeasures.The theoretical estimates of the post grouting bored piles and traditional bored piles,the actual static load values of the post grouting bored piles were compared and analyzed.The results show that the foundation design of the bottom post grouting bored piles isreasonable and the significant results have been achieved. In addition, the author collected the engineering data of the pile foundation of the residential building No.1-19in Wangdingdi medical city of the adjacent field area. The engineering geological conditions of thetwo projects are similar, so they can be compared. By comparing the two projects, thefollowing conclusion can be drawn: the bottom post grouting bored piles shorten the lengthof22-23%than the traditional bored piles. In providing basic same vertical compressivebearing capacity when their diameter is700mm. And there is little difference between theirsedimentation value.