Research On Mechanical Characteristics Of Bamboo Pipe Pile And Soil Nailing Composite Retaining Structure

The acceleration of urbanization brings about the development of high-rise buildings and full use of underground space.Theoretical research and practice of foundation pit excavation and support technology are more and more importantThe original single supporting technology could not meet the present requirements of safety,environmental protection and low carbon.Under this background,considering high strength and energy saving,an ecological retaining structure with bamboo pile and soil nailing as an example is put forward in this paper.In order to study this new supporting system in depth,the role in supporting system and conventional failure modes of bamboo pile and soil nailing were summarized in contrast to the conventional bamboo pile and soil nailing retaining structure.In the field of experimental research,the compression tests,bending tests and miniature model tests of the shallow foundation pit of original bamboo members were carried out,and some progress had been gotten.Stress and deformation of the original size bamboo pile soil nailing support structure corresponding to the miniature model tests were detailedly analyzed through ABAQUS.To test the mechanical properties of moso bamboo,axial compression tests of 54 round bamboo members were carried out to determine the change rule of bamboo members,ultimate bearing capacity in Xianning area of Hubei province.The bamboo joint,s influence on bearing capacity of bamboo members were analyzed by comparison of the compressive strength.Meanwhile,three types of failure modes in compression tests were summarized.In transverse bending test,the distribution curve of bamboo beams,deflection were drawn and changed with the changeable load by displacement from displacement meter.Meanwhile,the plane-section assumption is suitable for the bending deformation of the circular bamboo by strain values at different heights on bamboo beam.This material performance test shows the excellent bending performance and great material toughness of moso bamboo.Based on the indoor miniature model experiment,a finite element model of foundation pit supported by bamboo pile and soil nailing was established by ABAQUS.Through the set of analysis steps,the excavation working condition of foundation pit was simulated.Considering soil deformation,pile strain,bending moment and axial force of soil nailing,the mechanical and deformation characteristics on bamboo pile and soil nailing composite retaining structure were analyzed.The following conclusions are as follow.Firstly,considering soil arching effect unobvious,it is allowed without consideration in model test with bamboo pipe pile and soil nailing composite retaining structure.Secondly,the maximum displacement in soil surface of loading area reaches more than ten times the minimum displacement.An inflection point with displacement appears in the eight meter range outside the foundation pit.Third,the deformation of bamboo pile changes with different excavation stage,and positive and negative bending moment occurs alternately in different positions of the bamboo pile.The inflection point with bending moment is finally stabilized by the initial multipoint,and the maximum stress of pile moves down along with deep excavation.Fourth,the change rules of axial force of each row of soil nailing are similar.Only one maximum value of its axial force exists along the length,and the axial force is small at both ends and large in the middle.