Study Of Load-Bearing Properties Of Large-Diameter Long Friction Pile

Because of the influence of factors such as the bridge superstructure, load and hydro geological conditions, more and more long-span bridges have been appeared. The diameter and length of the pile has been increased to improve the bearing capacity of the bridge's foundation. So a large number of large-diameter long friction piles have been applied to engineering. An empirical formula has been used to calculate the vertical bearing capacity of large-diameter long friction piles in the current code. But this empirical formula is conservative and cannot reflect the mechanism of load-bearing and deformation for large-diameter long friction piles, that has led to contradictions of the theory and the reality. Although design load safety factor has been considered in the calculation of allowable pile vertical bearing capacity, yet control standard of the single-pile settlement have not been mentioned. So pile-soil deformation calculation and vertical bearing capacity of pile have not contacted each other, that has led to cannot forecast the influences of single-pile settlement on upper structures. The disease would have appeared at some structure after completion. This paper analyzes the bearing properties of large-diameter long friction piles and presents a method of accurate calculation for single-pile settlement, by which determinates of vertical bearing capacity of large-diameter long friction piles is determinated.After well studying and analyzing, a systematic study of the bearing properties of large-diameter long friction piles has been made through the static load test result, simulation analysis as well as theoretical calculation. And a kind calculation method that vertical bearing capacity of pile foundation can be determinated according to P S curve is put forward. The validity of all the above methods on the real projects is also compared and analyzed and a method system of calculating vertical bearing capacity of pile foundation through P S curve has been formed. Major results of this thesis provide the design theory and calculation means for large-diameter long friction piles. This makes the pile foundation design more and more economical and secure. Meanwhile, we can forecast the influences which the settlement of pile to upper structures and provide reasonable design or structural measures for upper structures to guarantee Structure's normal using requirement. Not only could the research be provided to lay a theoretical foundation for the perfection of Design of Ground Base and Foundation of Highway Bridges and Culverts, but also gives important theoretical meaning and practical value.