| With the increased national investment in construction in the west,more and more projects in permafrost areas are being accelerated.As the main engineering material in construction,the study of the interaction between concrete and powdered clay body is of great significance to the safety and economy of engineering projects.The article analyzes the effect of different materials,normal stresses,roughness and temperature on the shear strength of pile-soil interface by establishing the coupling equation of hydrothermal force,and derives the formulae for calculating the shear strength of pile-soil interface under normal and negative temperatures.The effects of roughness on the pile axial force,pile lateral freezing force and pile top displacement were qualitatively analysed.(1)The variation of shear strength at the contact surface of different materials is analysed.The variation of shear strength at the interface at room temperature is concrete-soil > woodslab-soil > aluminium-slab-soil,while the shear strength at the interface of aluminium-slab-soil is the highest at negative temperature,indicating that the physical properties of the materials and the smoothness of the contact surface have different degrees of influence on the interface shear strength.(2)The shear strength of the pile-soil interface under different normal stresses was analysed.The contact surface shear strength increased gradually with the increase of normal stress,but the rate of increase decreased gradually with the increase of normal stress.The shear expansion of the contact surface occurs at low normal stresses,while the contact surface shows shear contraction at high normal stresses.(3)The influence of the geometric effect of the contact surface and the sand filling method were combined to define the concrete roughness,and the change law of the interface shear strength under four kinds of roughness was analysed,and it was found that when the roughness was less than 2.793,the peak shear strength increased gradually with the increase of roughness,and when the roughness was greater than 2.793,the peak shear remained basically the same with the increase of roughness,i.e.at room temperature The critical roughness is 2.793.(4)The variation of the interface shear strength at different temperatures was analysed,and the variation of the interface shear strength with displacement was divided into three stages:elastic stage,plastic stage and smooth shear stage.Compared with the peak shear strength of the interface at room temperature,the peak shear strength at negative temperature increased by80%,indicating that the influence of temperature on the interface shear strength is greater,when the temperature is higher than-2°C,the change of interface shear strength with increasing roughness is more obvious,when the temperature is lower than-2°C after the contact surface shear strength with the change of roughness has less influence,indicating that as the temperature decreases the influence of roughness on the interface shear strength gradually The effect of roughness on the interface shear strength gradually decreases as the temperature decreases.(5)By analysing the effects of normal stress and roughness on the interface shear strength at room temperature,the concrete-soil interface shear process was divided into three parts for calculation,and the formulae for calculating the interface shear strength were derived,and the reasonableness of the formulae was verified by comparing with the numerical simulation results.The influence of different factors on the interfacial shear strength was analysed by using SPSS software for the law of change of interfacial shear strength under negative temperature,and the formula for calculating the interfacial shear strength under negative temperature was fitted.(6)Using qualitative analysis,the effect of different roughness of the pile surface on the displacement of the pile top,pile shaft force and pile side freezing force under negative temperature is analysed,according to the P-S curve,it can be seen that the ultimate bearing capacity of the pile is increased to a certain extent with the increase of roughness,when the pile top load is less than the ultimate bearing capacity of the pile,the roughness of the pile surface can reduce the settlement of the pile,and when the load exceeds the ultimate bearing capacity,the effect on the settlement of the pile The effect on pile settlement when the load exceeds the ultimate load carrying capacity is very small.The pile axial force decreases with increasing roughness and the effect of roughness on pile axial force decreases with increasing pile top load.The pile side peak freezing strength increases with increasing roughness and then stabilises.When the temperature reaches-5°C,the roughness has basically no effect on the pile side freezing strength,indicating that both the increase in pile top load and the decrease in temperature suppress the effect of roughness on the interface shear strength. |
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