Experimental Researches And Numerical Analyses Of Vertical Bearing Behavior Of Bored Pile Foundations Including Defective Piles With Stem Enlargement Or Shrinkage

As one of the most important foundation forms, bored pile has been used inengineering construction widely. However, due to variable geological andconstruction conditions, bored piles were likely to develop into some kinds of defectpiles such as broken pile, stem shrinkage pile, stem enlargement pile, concretesegregation pile, which had a negative influence on the pile bearing capacity andsettlement. Major source of hidden danger and finansial loss was caused by improperhandling of these defect piles. At present, the processing and utilization of defect pilesmostly rely on experience, lack of convincing theory basis. It will lead to two kinds ofsituations, one is the estimation of defect pile bearing capacity is too high, and lead todanger; the other is the estimation is too low, then too conservative reinforcingmeasures are taken and lead to waste.In view of the above facts, this paper carried on a study on the vertical bearingbehavior of stem shrinkage pile and stem enlargement pile, aiming at providing theorybasis of the processing and utilization of defect piles and proposing an index systemand method for evaluating defect pile vertical bearing capacity and settlement. Studymethods of this paper included two aspects, experimental analysis and numericalcalculation. The test included indoor test and field test. This paper proposed acomplete set of methods through the test, including the controlling of indoor modelfoundation soil, hole-forming method of model pile, field grouting pile method, andpile load test control scheme, etc., especially in expanding and reducing the hole, thispaper took use of the homemade tool, and constantly trying to grope, put forward a setof method in making defect model piles with the same conditions as the normal pile insitu, and the qualities of the defect piles were at a certain accuracy. The numericalcalculation took use of the PLAXIS finite element analysis software2D module. Backanalysis was adopted in correcting the numerical simulation parameters of model pile.Then the parameters were used in the analysis of actual engineering size model pile. Adiscussion was brought out about the vertical bearing behavior of the model piles.Through the test and numerical analysis, this paper finally concluded some results:1. Put forward a set of test standard for model pile experiment analysis;2. Put forward a set of method in making defect model piles with the same conditions as the normalpile in situ;3. Comparation analysis of the load-settlement curves of defect piles andnormal pile was carried on;4. A series parameters for simulating the pile load testwere proposed by back analysis, and were applied in the simulation of real size pilemodel. Some important conclusions were got in the end.