Load Bearing Characteristic Studies Of Large-Diameter Tubular Piles Using Cast-In-Situ Concrete

Construction technics and structure characteristic of large diameter cast-in-situ tubular piles is different from that of ordinary cast-in-place piles or steel pipe piles, which bring on the particularity of tubular pile's bearing characteristic. Using analytical arithmetic, three aspects have been studied that are tubular pile's vertical bearing force considering soil core's function, tubular pile's bearing characteristic under vertical and transverse load, and stress and displacement of double-row-pile sea wall's piles. The main original work and results are as follows:1. With elastic-plastic load transfer function, a set of analytical equations for the axial load-settlement curve of cast-in-situ tubular pile have been deduced to determine the vertical bearing capacity of pile according to the settlement of the pile top. The distribution equations of axial force and friction along pile can be gotten. It shows that force soil core beared and friction will change following the pile top load, pile and soil elasticity modulus ratio and pile's inner and outer diameter ratio. In single pile's load-settlement curve, the longer pile length is or the bigger C_sa and k_a is, the bigger the ultimate resistance of the pile is, then the bigger the settlement is.2. On the basis of 'm' method, coupling formulas have been gotten when single pile is loaded under the load combination of vertical focus load, transverse load, pile's self-weight and its inner and outer friction, and free load is concluded in for the first time. It shows that P-Δ effect can't be ignored when the free length and vertical load are big, and pile's deadweight and its friction have little influence on distortion and bending force along pile. The top transverse distortion and the most bending force have the same current with the top bending force, the top transverse force, free length, pile's diameter, etc, in which the top transverse force has the biggest influence on pile's most bending force and the top transverse distortion.3. Several kinds of sea wall structures are introduce in this paper, equivalent pile top load of each pile of double-row-pile sea wall was gotten by the method of structure displacement.First pile top distortion coefficient, top rigid coefficient, tip board' s displacement and its corner are calculated, then the loads acting on the tip of the sea wall are equivalent to each pile top.4. Bending force and transverse distortion along pile are calculated in three kinds of working conditions, which are single pile under load in construction period, fugacious load domino effect combination in sea wall construction period and permanent load domino effect combination in common using period. It shows that pile has the biggest bending force value under the third working condition, bending force decrease along the pile from the pile top under the second working condition. Influence of changes of pile space between and row space between to load transfer characteristic of sea wall is analyzed.