Analysis Of The Influence Factors On The Reliability Of Spiral Under Inclined Load

Spiral pile is a pile with spiral shaped blade on the surface of the pile, because of the difference of material properties, load and the distribution characteristics of the blade, the bearing mechanism of the spiral pile foundation is different. Spiral pile is a variable section pile. If the spiral pile is subjected to inclined load, the failure mode and the load transfer mechanism of the spiral pile foundation are more complicated. Piles often also bear the horizontal force and vertical force. Therefore, if it is impracticable to screw pile single pile bearing capacity reliability with fixed value method to study, the tilt loading screw pile single pile bearing capacity reliability of the JC method.In view of the complexity of the spiral pile under inclined loads, the mechanical characteristics and failure mechanism are discussed in detail. On the basis of this, the paper focuses on the calculation model of ultimate bearing capacity of screw piles, and deduces the limit state equation. Inclined load under the action of screw pile single pile bearing force limit state equation, there are different variables, corresponding to different statistical characteristics. This paper mainly uses empirical formula method, static load test and static cone penetration test and three methods will be combined together to derive the statistical characteristics of the variables. Then, in order to study the influence of different variables on the reliability index of single pile’s ultimate bearing capacity, the paper discusses the method of engineering example. JC method of calculating the steps in a large number of iterative calculation, in order to ensure the accuracy and speed of calculation, according to the Fortran 90 standard in the Powerstation Fortran 4 Platform for the preparation of the corresponding calculation program. The program can analyze the reliability index of the pile and soil structure under different failure modes. Finally, a large number of numerical calculations are carried out by the computer program, and the different factors that affect the reliability of the single pile’s ultimate bearing capacity are discussed, and the following conclusions are obtained:(1) if the other conditions are certain, the reliability index increases first and then decreases with the increase of load effect ratio. (2) if the other conditions are certain, the reliability index increases with the increase of the total safety factor, and the effect is obvious. (3) if the other conditions are certain, the number of small pile diameter piles is more favorable than the large pile diameter piles with small quantity. (4) if the other conditions are certain, the standard value of the limit side resistance is high and the standard value of the limit end resistance is small, but the reliability index is relatively small.