Test Research On Working Behaviors Of Micro-pile With Coupling Beam

There are more and more projects using of this kind of new efficient pile foundation since micro-pile invented by Lizzi in the 1950 s.Nowadays,the use of micro-pile extend to the various branches of geotechnical engineering from ground stabilization in the early stage.In recent years,micro-pile had achieved good result of engineering in control of landslide,but there have no widely accepted theory of the design to micro-pile,especially there have no clear understanding that the form and effect of coupling beam.Test research of the effect that the working behaviors of micro-pile by different form of coupling beam was carried out in this paper.Based on similarity theory,analyzing the effect of micro-pile with different coupling beam through the model test of indoor frame.There have some reference significance to he application of micro-pile in the project of landslide treatment.In this paper,mainly researches of several aspects are as follows :1.In order to simulating the real landslide,research on similarity theory for reflecting actual law truly by test data in detail.Based on similarity theory,specially deduced the similarity coefficient of each parameters of slide body and micro-pile.Designing material of model test by combining both condition of test and expected purpose.A new replaceable simulating method of coupling beam was designed,the items of testing equipment and monitoring method were introduced,completed and explained the working conditions and testing steps.2.Analyzed the mechanical characteristic of micro-pile with different form of couplingbeam and compared four groups working conditions,which reflected by load-displacement curve,pile bending moment along the depth,soil pressure of front and back with pile along the depth,which organized by testing data.Test results indicated that maximum displacement of pile top of micro-pile with longitudinal and transverse cross beam decrease by 20.07% than transverse beam,extreme value of bending moment of each row along the direction of landslide decrease by 18.65%,5.61%,13.64% than transverse beam,but there are concentration of bending moment on the pile top,maximum landslide pressure back of pile which each row along the direction of landslide increase by 47.62%,55.56%,75% than transverse beam,load sharing ratio of each row increase to 1:0.903:0.871 from 1:0.895:0.796,stressed uniformly to pile of each row,the soil resistance of pile front and the deformation of pile were decreased.Transverse beam didn't appear to be much different than independent micro-pile,displacement of pile top,bending moment,soil pressure are consistent to longitudinal cross beam compared with longitudinal and transverse cross beam,which indicated that longitudinal cross beam play the mainly role of increasing the integrity of micro-pile group,and the effect of transverse beam was not obvious in the condition of this test.3.Nonlinear finite element analysis with strength reduction method was conducted,which indicated that plastic zone connection was interdicted effectively by all sorts of micro-pile,increased the stability of landslide.Equivalent plastic strain and maximum displacement was deceased observably by longitudinal and transverse cross beam than transverse cross beam.The finite element simulation is in good agreement with the model test on the regularity of the interaction of various coupling beams.4.Combined the model test and finite element simulation finally,comprehensive summing up the effect of coupling beam of micro-pile,and application recommendations for coupling beam on micro-pile were given.