The relationship between the shear strength of interface and the times of cycles is analyzed by the improved labotatory experiment

The friction coefficient of the pile and soil interface changes with the temperature cycle

and the variety of average shaft resisitance of temperature cycle is studied by numerical calculation model. It is found that the shear strength of interface decreases with the increase of the times of cycles after several times of temperature cycles

and the greater the normal stress is

the more loss of shear strength is after the temperature cycle. During the process of temperature rising

the friction coefficient of the pile and soil interface decreases and the average shaft resistance decreases. During the process of temperature declining

the friction coefficient of the interface increases while the average shaft resistance increases. After several times of temperature cycles

the friction coefficient of the pile and soil interface remained basically unchanged

and the average shaft resistance of the pile-soil interface became more and more stable during the heating and cooling process.