Study On Anti-sliding Mechanism And Calculation Method Of Grouting Micro Steel Tube Composite Pile

Micropile is a type of small diameter bored pile constructed by strong reinforcement and pressure grouting, of which the diameter is between 100 and 300mm, slenderness ratio is larger than 30.As a new type of slope supporting structure, grouting micro steel tube composite pile is combined in a certain cross-section using the steel pipe as reinforced materials. With the advantage of rapid and convenient construction and fully mobilizing the self-anti-slide ability of rock and soil mass, micropile has an increasing wide application in slope reinforcing engineering;however, the immature theoretical studies have been done on the micropile anti-slide structures, In view of this, the research effort is carried out in this thesis.At first, the geo-mechanical indoor model test of the grouting micro steel tube combination pile which used to reinforce the rock slide is studied in this thesis.,the model test shear box which demanded by indoor model test is designed and the model materials of rock and soil are prepared in accordance with similarity theory, based on those, the model test is implemented. The impact of the section form on the anti-sliding performance of the group piles is the major consideration in the model test. The section form of micro composite pile includes single-row, rectangular section and round section. For the single-row pile, the pile spacing is 3 times pile diameter; the lateral pile spacing is also 3times pile diameter within the micro combination pile with the rectangular section, while its vertical pile spacing are 2 times,4 times,6 times, and 8 times pile diameter. For the round section micro combination pile with the piles placing evenly in the center of the circle section and the section circumference, pile spacing are 2.5 times,4 times, and 6 times pile diameter.Secondly, based on analyzing the results of model test, the anti-slide mechanism of micro-composite pile which used to reinforce the bedrock landslides is discussed. The distribution feature of internal force and the lateral earth pressure of the single pile within the composite pile are acquired through the analysis of model test, at the same time;the variation character of the micro-composite structure's pile head displacement under different lateral load is acquired.According to the model test results, the anti-sliding mechanism of grouting micro steel pipe combination pile is revealed from those respects, including the failure mode of the whole micro composite pile, the impact of the section form on the anti-sliding performance of the group piles, the lateral load transfer effects within the micro-composite pile, and the characteristics of single pile's inner force and deformation within the composite pile.Finally, based on the foregoing study, the mechanical computation model of the grouting micro pipe combination anti-sliding pile is established, which is demonstrated to be correct and rational by model testing data recalculation and a calculation example analysis, and the corresponding calculation method is proposed.