Experimental study of stress concentration factors of hollow pipe-piles

The hollow pipe-piles can effectively reduce soil squeezing effect during static pile driving, and accelerate the dissipation of excess pore water pressure, decreasing its maximum value. With accelerating the dissipation of excess pore water pressure, unfavorable situation including pile floating and skewing can be effectively avoided, while the bearing capacity of pile foundation as a whole and the stability of foundation pit can be raised. But the openings in the shaft of pipe-pile can certainly generate stress concentration and weaken the bearing capacity of the pipe-pile. Thus, a series of model tests on stress concentration and ultimate bearing capacity of the hollow pipe-pile is carried out. The stress concentration and the reduction of ultimate bearing capacity are analyzed. The testing results show that the performance of the piles with symmetrical opening holes is better than that with the asymmetric opening holes with regard to the bearing capacity, and the bearing capacity of the pipe-pile with hole opened in a radial direction is the highest among all types of piles. The above results can provide guidance for designing the hollow pipe-pile foundation and help promote their application.