| Piles'bearing capacity is composed of the side friction resistance and the bottom resistance. Under normal circumstances, the side friction is dominated. When the pile there is a certain thickness of soil due to consolidation of such cases, the pile side resistance occurs adverse effects on the pile bearing capacity of the negative friction. At present, many research works have been took for the pile of negative friction, and carried out a lot of result in theoretical research,field testing,laboratory testing and numerical simulation by internal and external scholars, but it rarely has research focused on the relevant parameters of pile as "Xigeda strata " of Pan-Xi region, and there are few studies about which caused filling nagtive friction.This article relies on Two projects that mentor Professor-level senior engineer Liu Wenlian take a "Xichang, Panzhihua Iron and Steel Vanadium and Titanium Resources Comprehensive Utilization Projects-Pile Type Selection and Design Parameters of Pile Foundation" and Professor Fan Zhuguo commitment "Xichang, Panzhihua New Steel Vanadium Titanium base for numerical simulation of pile foundation ", based of field test and carried out theoretical calculations and numerical simulation of negative friction pile conducted a study of specific tasks include the following aspects:(1) Taking site testing of single pile of negative friction in Xichang, Panzhihua New Steel Vanadium Titanium base. Laying stress terms in the pile, setting stratified settlement gauge around the pile, through heaping loadings around pile top, forced consolidation by inject water, Backfill settlements and axial force are measured, analyzes the influence of loading,inject water and backfill compaction on axial force on the shaft, the neutral point location and the size of the negative impact of frictional resistance;(2) Using the formula for the location of neutral point is calculated, and the results measured with the field test results of difference between the 0～1.8m, the results are basically the same, indicating the outcome of this experiment can be used as the future of engineering design parameters;(3) Taking three-dimensional calculation model with FLAC3D software, through the simulation calculation and analysis of the fill thickness, loading of pile top on the shaft axial force, neutral and negative effects of frictional resistance, and compared with the field experiments found that pile load can reduce negative friction on piles in the drop-down role. In this paper, combining theoretical and experimental approaches, and should be supplemented by computer simulation, studying of negative friction of single pile in backfill which constituted with "Xigeda strata" in Panzhihua New Steel Vanadium Titanium base, and obtained reference value results for construction of pile foundation design in the future. |
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