Numerical Analysis On Bearing Capacity Of Post-Grouted Bored Pile Under Vertical Load

Bottom slime and shaft mudcake are two principal deteriorative factors affecting the mobilization of bearing capacity of slurry bored piles. To solve this problem, the Institute of Foundation Engineering of CABR successfully developed the patented post-grouting technology. Through the effects of filling and cementation, intrusion, compaction and consolidation, post-grouting can significantly improve bored pile bearing capacity and reduce pilehead deformation.This thesis, based on summary of previous researches and numerical analyses using finite element method, presents study on the vertical bearing characteristics of post-grouted bore piles, as follows:(1) Systemic summarization of the state-of-the-art of post-grouting technology, including its development history, construction procedure, strengthening mechanism, improvement of post-grouted soils, field testing, analytical and numerical study, etc.(2) Detailed presentation of field results of pile load tests on post-grouted bored piles for the two huge projects of Beijing Capital Airport new Terminal 3 and ShanghaiExpo 500kV underground transformer substation. Based on the comparative load test results, it is demonstrated that post-grouting can significantly improve the bearing characteristics of bored piles.(3) 2D axisymmetric finite element modeling using Plaxis software was established for both post-grouted and non-grouting piles; and 3 typical field tested piles were analyzed and compared. To consider the small strain stiffness developed in the initial load stage during pile testing, HS small model was implemented.(4) Parametric study on the influences of grouting volume and strength of grouting bulk on the bearing characteristics of post-grouted bored piles was conducted.(5) 3D finite element modeling was also set up and its results were compared with field tests and 2D axisymmetric results.