Study On Post-grouting Technologies Of Bored Piles And Their Application

The post-grouting technologies of bored piles can eliminate the adverse effects on the cutting at the bottom of pile and the silt around pile and can improve the impact between pile and soil, and can increase the bearing capacity of single-pile greatly, Therefore, the technology was widely used in construction in recent years.The paper discussed the impacting mechanism of the cement fluid and the soil around the pile and provides the guidance for design and construction. And this can improve the application of the technology of post grouting. The paper expatiates it from several aspects as follow.Firstly, basic features of grout and the rheological property of grout impacted by force are analyzed in the paper.Secondly, the author analyses the mechanism that the post-grouting increases the bearing capacity of the bore pile.Thirdly, the author studies further the effect of the post-grouting for the stress and the shear stability of soil with micro-aspect.Fourthly, based on the theories above-mentioned and the practice of engineering, the author summarizes a series of practicing technological process of the post-grouting, the author considers the enlarge top at the bottom of pile to rigidity foundation according to the impact model between pile and soil. The enlarge top is pressured partly when the load along the axis of pile. The effective pressured area is the horizontal projection of the pressured area. Then the author gives out an experiential formula of single-pile limiting bearing capacity in gravel stratum.Lastly, the theory above-mentioned is used in the project of post-grouting in Wuhan. The post grouting can improve the bearing capacity of single-pile greatly and reduce the difficulty and the cost of project. And it was proved by the contrasting test between grouting and ungrouting.