Research Of Pile-sinking Resistance Of Jacked Pile In Soft Clay And Discussion On It's Application

Jacked pile has many good qualities such as noise-free, vibration-free and pollution-free. Jacked pile will be used more and more in construction as the development of the jacking machine and the increase of environmental protection. Compared with its widely application, the research or analysis about jacked pile is too few to satisfy the demands of construction.Based on the research of mechanism of jacked pile, the factors that may affect the end resistance and the shaft resistance are discussed.The practice shows that it is easier for jacked pile to penetrate into soil when it has a tine. To find out how tine works, the finite element method is used to analyze the affection to the end resistance caused by tine of pile in qualitative; the Terzaghi bearing capacity theory is used to analyze the affection in quantitative. The results show that the affection of geometry shape of end of pile should be considered when calculating the end resistance; it is better to add tine to jacked pipe pile when plug effect may appear so that the end resistance can be weakened and the pile can be penetrated easier.To research varies of shaft resistance during jacking, based on the ultimate equilibrium theory and the cavity expansion theory, daggle parameter is created to analyze varies of normal stress during jacking; according to the difference of frictional coefficient, the shaft of pile is divided into two parts: normal section and softening section. These analyses can explain the fact that the shaft resistance provided by certain soil decreases after the end of pile reaches the depth; these analyses also provide some theoretic direction for the estimation of shaft resistance.The property of pile is proved that it can be changed by the history of load through theoretic analysis and field tests. The relations between the final jacking force and ultimate bearing capacity are discussed from the view of surcharge preloading. The results show that the settlement should be controlled when confirming the value of final jacking force and if an appropriate termination criterion is applied, the final jacking force can be equal to the "preconsolidation pressure", and this opinion is verified by the field tests. Based on the above-mentioned, the application of final jacking force in the construction of jacked pile and the pile selection for the static load tests are discussed.