Research On Pile-rock Shear Characteristics And Load Transfer Mechanism Of Red Mudstone Pile Foundation

With the national "One Belt And One Road " program and the "13th Five-Year Plan"put forward,a variety of high-rise buildings,highways and high-speed railways,bridges,ports and terminals and other large infrastructure is planned and under construction,especially the western Area construction as a focus.China's western region is located in the plateau,basin,mountain and other complex terrain,and in the region widely distributed red mudstone.In the red mudstone area for large-scale infrastructure construction,the foundation of the carrying capacity and deformation requirements are higher.The pile foundation has the advantages of high bearing capacity,small deformation,convenient construction and economical cost,and has been popularized in the project and has become an important basic form of large-scale buildings.At present,the research on the bearing mechanism and calculation method of the pile foundation of the red mudstone needs to be improved.Therefore,the mechanism of the interaction between the red mudstone and the pile foundation needs to be studied deeply,and The influence of pile-rock contact surface roughness on bearing capacity of pile foundation is studied in detail.In this paper,a method for measuring the three-dimensional topography of pile-rock structures is proposed.The surface of pile-rock in pile beds with red beds is measured and the surface roughness of pile-rock is classified by the measurement results.Based on the shear stress characteristics of red mudstone-concrete interface under different roughness and different normal stresses,the load transfer mechanism of red mudstone pile is deduced according to pile-rock shear characteristic theory.Mainly include the following aspects:(1)Image acquisition and image preprocessing of three-dimensional topographic features of pile-rock interface of red mudstone pile by digital image processing technique.Three-dimensional reconstruction of pile-rock contact surface gray-scale images after image processing was carried out by using computer vision.The three-dimensional reconstructed topography of pile-rock contact surface was obtained and compared with the self-made simple contact roughness measuring instrument Contrast analysis to verify the accuracy of this method.(2)The quantitative description of the roughness of pile-rock facies is mainly expressed by roughness characteristic parameters.At present,the roughness characteristic parameters of structural plane are solved by statistic method and fractal geometry method.Based on the statistical method and the fractal method,the single characteristic parameters can not fully describe the roughness characteristics of the pile-rock facies.Therefore,it is necessary to combine the fractal dimension with the traditional parameters to make a more comprehensive description of the pile-rock facies And the roughness of pile-rock facies of red-bed mudstone pile are classified.(3)The red mudstone in Chengdu area is selected as the research object,and the direct shear test of mudstone-concrete interface is carried out by sampling in the room.The shear strength,deformation characteristics and shear failure modes of mudstone-concrete interface under different roughness and different vertical stress conditions are studied.(4)According to the indoor direct shear test,the shear characteristics of the pile-rock contact surface of the red mudstone pile are obtained,including the three stages of cementation,slippage,shear and sliding.The pile-Shear constitutive model of rock contact surface.Based on the shear characteristics of pile-rock contact surface,the load transfer characteristics and bearing capacity of red-bedded mudstone are analyzed synthetically.The pile-side friction resistance and the axial force of pile body are deduced by load transfer method.