Abstract:With the development of the construction technique of cast-in-place piles with sleeves driven by using high frequency vibratory hammers, the cast-in-place piles have been widely used in construction engineering. But the researches on the penetration mechanism of sleeve for cast-in-place piles driven by using high frequency vibratory hammers, especially the excess pore pressure generated by sleeve for cast-in-place piles installation into sand, are still not complete. The paper presents the FEM model of penetration of sleeve driven by using high frequency vibratory hammers, and studies in detail the formation, distribution and variance tendence of excess pore pressure. And factors affecting behavior of pore pressure such as penetration depths, outer diameters of sleeve, displacement amplitudes and permeability coefficients are also studied by orthogonal finite element method combining the orthogonal experiment with numerical simulation. The results of finite element analysis show that excess pore pressure decreases with the increase of vertical distance and radial distance from the tip of sleeve. Excess pore pressure amplitude increases gradually with time, and decreases with the increase of vibratory frequency in sleeve penetration. Excess pore pressure assumes roughly exponential decay trend with time, and dissipates mainly along the inside of sleeve at the end of sleeve penetration. The primary factors affecting behavior of pore pressure are penetration depths and permeability coefficients. The results provide theoretical and practical reference to analysis of pore pressure generated by sleeve for cast-in-place piles installation into sand using high frequency vibratory hammers.