Experimental study on vertical tensile bearing mechanism of screw cast-in-place piles

The vertical tensile bearing capacity of the screw cast-in-place pile is studied through the indoor model tests and field tests, and it is shown that the screw cast-in-place pile is superior to be used as the uplift piles. Through the indoor model tests, the failure modes of the screw pile and the straight rod pile by uplift loads are obtained intuitively by using the image processing technology, then the tensile bearing mechanisms are discussed, and the field tests are used for verification. The model and field tests show that the tensile bearing capacity of the single screw pile is higher than that of the straight rod pile with the same diameter, and the tensile lateral resistance of the screw pile is obviously higher than that of the straight rod pile with the same diameter. For the screw section, the tensile ultimate lateral resistance is the shear strength of the surrounding soil, and the fracture surface is a continuous arch. For the straight rod section, the tensile ultimate lateral resistance is the friction resistance between the pile body and the soil around the pile, and the failure surface is the cylinder around the pile. According to the test results and from an engineering practical point of view, the expression for the tensile ultimate bearing capacity of a single screw cast-in-place pile is given by introducing the drawdown coefficient, and the values of the relevant parameters are suggested.