Settlement Calculation Studv Of The Tubular Pile-net Composite Foundation

Tubular pile-net composite foundation is a new type of foundation treatment engineering, With the advantages of simple construction,makings provinces, high bearing capacity, short construction period, etc. During the construction of the deep soft soil area, due to the large settlement, especially engineering accidents caused by uneven settlement occurs frequently.At present for the pile cap type composite foundation, settlement calculation still uses the conventional algorithm, unable to distinguish the settlement between pile top and soil between piles. Under the action of the foundation in internal load,the distribution of stress field and displacement field study is little,and the measured data is less. Composite foundation settlement calculation theory lags far behind the engineering practice, it is to be continued developmentTubular pile-net composite foundation under embankment load is discussed in this paper,and additional stress formula of pile tip resistance, lateral friction resistance and medial friction resistance is deduced respectively based on Mindlin stress solution. It can be achieved that on the elastic foundation of an arbitrary point within additional stress computation to solve. Pile shaft resistance distribution forms, the pile load distribution changes and the neutral point position change on the effects of the additional stress in pile foundation are discussed in detail. The changing of stress coefficient of pile shaft resistance with different pile type section are compared.And then analyzed the play of " soil arch effect" and "tension membrane effect" in the reinforcement of composite foundation of pile type. Related theoretical formula was deduced with piles arranged in triangle and it propose a new method to calculate the pile efficacy. Discussed the influence of pile efficacy by the change of Rankine passive earth pressure coefficient of embankment filling and the ratio of pile spacing and pile cap width.As the surface load distribution form between piles is analyzed, the additional stress of soil bearing between piles is calculated with Boussinesq stress solution and then Mindlin-Boussinesq united additional stress field solution method of tubular pile composite ground is given. This method is applied in composite ground settlement calculation and the result is compared to the experimental data. At the same time, Combined with the finite element analysis, it is proved correctness and feasibility of the method proposed in this paper. And this method can be used for reference to engineering.At last, the load transfer mechanism of the special-shaped tubular pile with rib is studied by numerical simulation in this paper. The results show a more rapid mobilization of the side friction can be observed for the perpendicular surface to radial of the rib than the side surface and the circumferential surface. The effect of length and width of the rib on vertical bearing capacity are also discussed. It can be found that the length of the rib has a more significant effect on the vertical bearing capacity than the width. To provide a guideline to the engineering application of the new type of special-shaped tubular pile, a calculation formula on the vertical ultimate bearing capacity for the special-shaped tubular pile is proposed by correcting the formula for ordinary circular section tubular pile.