Study On Calculation And Application Of Anti-sliding Piles Under Pile-soil Interaction

Anti-sliding pile is a retaining structure used extensively in the measures of landslide treatment, which plays a very important role in the measures of landslide treatment of the whole world. The traditional analytical methods of anti-sliding pile take the soil and the anti-sliding pile into account respectively without considering their coupling, in which the soil is just a force and the pile is just a bearer. In fact, under the effect of the landslide thrust the anti-sliding pile can mobilize the resisting force of most soil and rock exceeding the range of the pile width, which behaves the obvious effect of pile-soil interaction. At present, because of the complexity and mutability of the soil and rock, the design theories and calculation methods of anti-sliding pile are immature and should be more perfect and be supplemented so that it will approach the fact much closer.Firstly, the calculation theories of the external force and internal force are studied in this paper. The calculation of the landslide trust is a prerequisite of the design of anti-sliding pile. The existing methods of calculating the landslide trust are summarized with analyzing the advantages and disadvantages of every method, in this paper, a method of designing loadings calculation is put forward under considering the resisting force of the block and the stability of the soil and rock in front of pile. In this paper, the composite stiffness principle with bi-parameter method under the soil-pile interaction, a new internal force calculation method of the anti-slide pile, is proposed based on the analysis of the existing internal force calculation methods of the anti-sliding pile. The deflection differential equation of the anti-sliding pile based on the composite stiffness principle with bi-parameter method is set up, and the formulae of displacement and internal force of the rigid anti-sliding pile are obtained. The finite difference method is used to set up the finite difference equation of the pile with considering eight kinds of support conditions. The internal force calculation and figure treatments of the anti-sliding pile are programmed under the different support conditions based on the composite stiffness principle with bi-parameter method. A (practical) example shows the calculated displacement and internal force of the anti-sliding pile would be reasonable and credible if the proportional coefficient and resisting index of the soil are suitable. The effects on the displacement and internal force of the anti-sliding pile are discussed in this paper, which result from the distribution of landslide thrust, bi-parameter m and l/n, the different support conditions.Secondly, in this paper, the numerical analysis is used to simulate the soil arching effect surrounding anti-slide pile with FLAC^3D, which is the main manner of the soil-pile interaction. The analysis results show that there are two kinds of stress arching surrounding the pile, the soil arching effect will increase with the depth of the soil, and different soil property leads to different soil arching shape. The effecting factors on the behavior of soil arching effect are studied in detail, such as the magnitude of load, the spacing between adjacent piles, the cohesion and internal friction angle of soil, the modulus of elasticity ratio of soil to pile, Poisson ratio, dilatancy angle, interface conditions, constraint conditions etc.By combining the principle of forming soil arching surrounding anti-slide pile, in this paper, the mechanical characteristics of soil arching is analyzed, and the conclusion that there are three kinds of failure form to the soil arching is proposed. Under the horizontal and vertical static equilibrium condition of soil arching and the controlled strength condition of the soil, a reasonable calculation formula is set up for pile spacing, and the calculation formula of thickness and highness are obtained for the soil arching along slip surface. The calculation formula of spacing between adjacent piles is illustrated by a practical project and the result shows that the pile spacing from the formula rational can not only guarantee the soil to exert all anti-sliding power but also ensure the slope stability.Micro steel pipe anti-sliding pile is a new retaining structure combined with the steel pipe pile and micropile. Micro steel pipe pile can not only retain the sliding of the slope but also reinforce the soil surrounding the piles. In this paper, it is proved that the tensile stress increments are generated in pile, while the compressive stress increments are generated in the soil due to the lateral loading, because of the friction and bonding between pile and soil. It is also proved by laboratory experiments that the reinforced soil surrounding the piles introduce some kind of additional cohesion. In this paper, the micro steel pipe piles and the soil surrounding piles are regarded as a new macroscopical continuous composite material of soil and pile with hardening, which increases the strength of the soil. According to the calculation method in this paper, the design method of single row and multi-row micro steel pipe piles are proposed, a practical project illustrates the effective application of the micro steel pipe piles in the slope problems.