Analysis On Settlement Of Single Large-diameter Cast-in-situ Tubular Pile

The situation of large population and land scarcity in China has restricted the rapid development of national economy seriously. Years of practice proves that reclamation is an effective way to expand the land. However the conventional embankment method has the problems of high cost and large settlement after construction. As a new structure, the embankment of large-diameter cast-in-situ tubular pile, which combines the superstructure with infrastructure, has a promising future due to its small cross-section and large depth of treatment. So far few overseas researchers focus on this study and most domestic scholars only concentrate on its vertical bearing capacity. With the wide use of this pile and structure, the settlement calculation has increasingly aroused people's attention. Therefore, this paper focused on the settlement calculation method of this kind of single pile.First, the progresses of this type of pile were introduced, mainly concerning about the bearing capacity and methodology of settlement estimation of this corresponding composite foundation. Based on these achievements, major factors on the settlement of large-diameter cast-in-situ tubular pile were determined. Then, factors, such as different pile length, diameter, wall thickness, soil modulus along the pile and beneath the pile etc., were studied on the settlement behavior by using the software ABAQUS. Results indicated that except the wall thickness, other factors had great influences on pile settlement. Unlike other solid pile, penetration is the main component of its settlement, and the influences on it were also considered in this paper. Analysis results showed that these influences, except pile length, may greatly affect downward penetration.Based on the above studies, a new method of settlement calculation of single large-diameter cast-in-situ tubular pile was put forward. Total settlement consists of two parts;one is the penetration and the other the compression of the underlain layers.How to calculate the penetration was proposed according to the results of numerical analysis while the compression of underlain soils can be estimated by integration method. After comparing the results obtained from stress dispersion method and equivalent solid mass method, both recommended in the code, the latter was proven to be more accurate.Finally, three cases were used to validate the method proposed in this paper. By comparing the results with numerical analysis and measurements, the results demonstrated that this settlement calculation could match well with the field data.