Study On Three-dimensional Soil Arching Effect Of Pre-stressed Anchor Pile

Pre-stressed anchor piles began to be used and developed as a new type of retaining structures in the1980s. It has been applied widely in the high slope and deep pit governance of highway, railway and housing construction because of its safety, economy, land conservation, etc. Engineering practice showed that pressure transmission mode of pile-anchor retaining structures can not better reflect its real force state, need to be further improved.Based on the engineering practice and access to relevant literature, soil pressure transfer mode of pile-supported embankment was introduced to the pre-stressed anchor pile retaining structures, a new calculation model was proposed-based on "three-dimensional soil arching effect of soil pressure transfer model " in which most of its of the pile plate structure directly was transfered to the anchor head by soil arch effect formed on-uniform deformation of soil, the remaining portion of its was then passed to the anchor head by the pile and plate structure.In order to demonstrate the correctness of the theory, the paper relied on scientific and technological project of Chongqing-based on three-dimensional soil arching effect pre-stressed anchor piles key technology research and application (CSTC,2010AC0109), and used theoretical analysis, indoor model test, numerical analysis and project monitoring and other technical methods, and carried out in-depth studies about three-dimensional soil arching effect exists, the factors that affect the soil arching effect, load transfer mechanism and the pile plate suffered earth pressure, and made the following achievements:①Through theoretical analysis, The paper demonstrated the existence possibilities of three-dimensional soil arching effect, put forward to its basic form conditions, derived the anchor spacing control equation of form soil arching effect. On this basis, deduced soil pressure formula exerted on pile and plate of basing on three-dimensional of soil arching effect, discussed the impact of factors related to the size of soil pressure. Finally, the paper described the rationality of the calculated results which was compared with the conventional design method.②Through the indoor model test, verified the existence of soil arching effect, discovered a significant distribution that the soil arching effect in the middle of retaining structures more apparent than its upper and lower. According to the experimental results, the three-dimensional soil arching was split into4three prismatic soil arch which its both ends directly supported in anchor head and a1shell soil arch which its Quadrilateral supported in three prismatic soil arch.Test data showed that the earth pressure was non-uniform distribution along the depth of fill, Earth pressure exerted on pile is inversely "B" distribution, and it was larger the anchor head than other parts; On the contrary, Earth pressure exerted on baffle is positive "B" shape, and the greater the distance from the anchor head, the earth pressure as well.③Through numerical analysis, the paper further verified the existence of soil arching effect, moreover, its distribution law was the same with Indoor test, finally, analyzed the anchor head spacing and soil physical and mechanical characteristics impact on soil arching effect, the results indicated that the shear strength parameters c、 φ, elastic modulus E, Poisson’s ratio μ had a significant influence on soil arching effect, the soil arching effect was enhanced with c、φ and E increasing and u weakening.④A slope engineering case monitoring results testified that three-dimensional soil arching effect was existed, and theoretical analysis and model test, numerical analvsis were corrected.⑤Based on the " three-dimensional soil arching effect" theory and research results, developed a set of anchor pile design calculation software, to be applied to the engineering design.