Study On Bearing Capability Of The New Cast-in-place Concrete Pile With Half-Screwed

Half-screwed pile has born as the development of our country's civil engineering, which is cylinder type in the top, and screwed at the bottom. Half-screwed pile adopts unique changed section design, and the general knowledge of life"The screw is nailed more firmly than the nail" is used in the design and construction of piles, whose firmer character reflects fully. Without movement of soil, mud and noise, half-screwed pile has environmental advantage, reliable quality, lower project fabrication cost, simple craft, fast construction rate, and extensive application range. As a new type of pile with Very high practical value, its development prospect is very broad.However, as a new type pile, its theoretical research is still far from enough, a lot of work only stays on the surface. In order to further popularize this pile technology and make it has broader application space, it is necessary carry on the further theoretical research about bearing capability of the half-screwed pile. On the base of the researchers of pile's vertically bearing capability, loading delivery mechanism and destroy mode domestic and international, through on-site static load test and analysis, the bearing capability of half-screwed pile is studied with hyperbolic model, empirical formula derivation and grey theory system model.Firstly, the development and current situation are analyzed generally, and its characters, construction method and advantages in application are introduced.Secondly, according to the research on relevant literature domestic and international, its loading delivery mechanism, effect factors and destroy model are analyzed systematically, and the method on research of loading delivery mechanism and bearing definite, which have made the theory frame for research of half-screwed pile.The third,On the base of analyses of half-screwed pile's structural characteristic, strength characteristic and mode of destroying, ultimate bearing capacity formula is deduced, side resistance on screwed section by soil shear strength, and revision coefficientψ_pi of ultimate tip resistance standard value squeezed branch pile and half-screwed pile and revision coefficientη_pi of ultimate tip resistance standard value's depth are pull into to revise tip resistance.Then based on the factual dates of static load test on half-screwed pile, Q-s curve of vertical static load test get mathematics analysis, grey GM (1,1) mode is established to predict ultimate tip resistance through grey theory lack of date modeling method, and it is compared to hyperbolic model and deduced ultimate tip resistance to verify its feasibility and accuracy.