A study of the strain characteristics and internal force nonlinearity of anti-slide pile

This paper presents an investigation of regularity between the internal force and deformation of anti-slide pile under the actual stress condition, places its emphasis on the regularity of force characteristics, deformation and stability of pile body under the interaction between anti-slide pile and soil. Based on experimental data of large physical model tests of anti-slide pile, and fitting the data with MATLAB, the solution from the strain data of pile surface to the deflection diagram of pile body is realized. The regularity between the strain characteristics and internal force variation of anti-slide pile are analyzed by comparing the strain of pile surface, bending moment of pile body, shear and deflection in the two conditions: different loading conditions under the same pile length and different pile lengths under the same loading condition. The results demonstrate that the working stage of anti-slide pile under the condition of monotone and cyclic loading is divided into three stages: the uncracked stage, concrete cracking-steel yield stage and steel yield-pile destroying stage. Under the first and second load levels in the uncracked stage, the stain surface of pile, the bending moment of pile body, the shear force of the load section and deflection appear smaller negative values due to the slight rebound of the compaction pile body of the soil, and the absolute values of the smaller negative values are about 1% the values at the pile destroying stage. The growth rates of strain, bending moment, shear force and deflection of concrete cracking-steel yielding stage are obviously accelerated. Strain, bending moment, shear force and deflection of steel yielding-pile destroying stage show nonlinear growth, and the failure modes of pile body are all bending and shear failure. As the length of the free end increases, strain and bending moment increase by about 10% and 3% at the pile destroying stage, while the shear force decreases by about 20%. Compared with the monotonic loading, the maximum bending moment and maximum deflection increase by about 2% and 1% respectively under cyclic loading.