Model Test And Mechanism Study Of Reinforcement For Slope With Constructed Retaining Wall By Micropiles

In southwest China,the terrain is mainly mountainous and hilly,with almost rugged roads,so the roads and houses are mostly built along the mountains.The urban areas are also uneven.Therefore a large number of retaining wall have been built.However,because of years of disrepair,rainfall,earthquakes,even it has not been designed when it's built,many of these retaining walls have cracked,seepage,and excessive displacement,so it should be reinforcement as quickly as possible.As a light reinforcement structure,micropiles have a lot of advantages,such as small influence on surrounding traffic and resident,fast and strong reinforcement,a high degree of mechanization,and little damage to the environment.Therefore,micropiles can satisfy all requirements when are people reinforcing the constructed retaining wall in urban and rural.In this thesis,the mechanism of micropiles reinforcing constructed retaining wall slope is studied by model test,and the mechanical of micropiles with different reinforcement forms are compared.Next,the bending moment and shear force distribution equation of micropiles is derived through theoretical research,and the micropiles application of reinforcing constructed retaining wall slope in two practical projects is analyzed,so the main research results are as follows:(1)By analyzing the results of the model test,the micropiles reinforcing constructed retaining wall slope can be divided into four stage: the soil compaction stage,the micropiles bending stage,the constructed retaining wall slip-incline stage and the soil cracking stages.From the result,we can know that the landslide thrust has dropped significantly after each row of micropiles,and the back row piles are carried a more landslide trust.(2)Combining with the mechanical characteristics of the micropiles section,the fourth-order linear homogeneous ordinary differential equation of micropiles deflection curve is derived by using the Hetenyi method.The law of full-length bending moment and shear force distribution have been obtained when reinforcing the slope with constructed retaining wall and the program for automatically calculating the bending moment and shear force of micropiles was compiled by MATLAB.(3)As a kind of flexible piles,the soil between micropiles and constructed retaining wall is extruded easily when the micropiles and constructed retaining wall are pressed against each other.In general,when the force of the micropiles is greater,the reverse bending is more obvious,and the maximum bending moment value of micropiles often appears at the position of the sliding surface.(4)Both the model test and the numerical simulation results show that the I-beam reinforcement micropiles has a large bending rigidity under the same reinforcement ratio,so its anti-sliding performance is relatively better.(5)Through the practical engineering numerical simulation results,the anti-sliding mechanism of micropiles reinforcing constructed retaining wall slope can be seen as an anti-sliding retaining wall which the micropiles group combined with the surrounding soil.Therefore,the micropiles can control the sliding of the slope body effectively and can improve the stability factor of the slope significantly.The research results of this thesis have important reference value for design in practical projects when people want to reinforce the constructed retaining wall slope by micropiles,and it can also provide some reference for further research on micropiles and constructed retaining wall slope.