Yaru Lv

Field Tests on Bearing Characteristics of X-Section Pile Composite Foundation

AbstractTo investigate the behavior of X-section cast-in-place concrete piles (XCC pile), a series of static load tests for piled foundation are conducted on the basis of a soft soil reinforcement engineering for a sewage treatment plant in the north of Nanjing, China. The testing results are presented in load-settlement curves, pile-soil stress ratios, distributions of skin friction (side friction) and axial force, and load-sharing between side resistance and end-bearing capacity. Comparative analysis between an XCC pile and a circular section concrete pile (circular pile) with the same cross-sectional area indicates that the XCC pile with its increased perimeter can improve the vertical-bearing capacity by 20% because of the larger skin friction. Also, the XCC pile shows increasing pile-soil stress ratio and reduces settlement. The existing design standards for traditional piles can be referenced by the XCC pile composite foundation, because the axial force and skin friction distribution are the same as...

In-Situ Tests on Cast-in-Place Concrete X-Section Pile for Bearing Capacity of Single-Pile Composite Foundation

The static load tests for pile composite foundation of X-section pile and circular section pile in the same area are conducted on trial pile in soft soil reinforcement engineering of a sewage treatment plant in the North of Nanjing, China. The load-settlement curves, pile-soil stress ratios and distributions of axial force are obtained. The comparison of test results on single-pile composite foundation of the two indicates that the vertical bearing capacity of X-section pile is 20% greater than that of the circular section pile with the same use of concrete because of the larger side friction. The results also show that the pile-soil stress ratio of X-section pile is higher than that of circular section pile, and the settlement of circular section pile is larger than that of X-section pile under the same loading. The axial forces of both X-section pile and circular section pile decrease from the pile top to the bottom. Therefore, in the same area, the bearing capacity of single-pile composite foundation of X-section pile is better than that of circular section pile. The in-situ test results are very significant for the theory study and engineering application of X-section pile composite foundation.

A Theoretical Analysis of the Vertical Shearing Mechanism of the H-Pile

Theoretical solutions dependent on vertical shearing mechanisms are derived by means of equilibrium analyses to calculate the effective vertical stress of the surrounding soil, the unit positive (or negative) shaft friction, and the axial force (or dragload) of the H-pile. They are calibrated by measured axial force and dragload of centrifuge model tests. In addition, the effects of vertical shearing on the load transfer mechanism of the H-pile are investigated.

A creep constitutive model incorporating deformation mechanisms for crushable calcareous sand

Due to the high compressibility and low crushing strength induced by remarkable intra-granular void and highly irregular shape, the creep response of calcareous sand is far larger than that of silica sand. Unlike silica sand, the creep behavior of calcareous sand under general stress might be divided into the initial near-linear phase, damping phase, and the steady phase. The three-phase creep behavior is difficult to be well described by general creep models, such as Burgers viscoelastic model. This paper conducted two sets of triaxial creep tests of calcareous sand under general stress state, finding that the three-phase creep is mainly governed by the mechanisms of grain rearrangement, interparticle friction, and particle crushing, respectively. Local instability near cavities on calcareous particles leads to specific initial near-linear phase and damping phase compared to silica sand. Further, a new creep constitutive model was established using different rheological components to theoretically describe the creep characteristics of calcareous sand. The constitutive model was validated and proved to describe creep behavior of calcareous sand reasonably with the test data.

Geometric Effects on Piles in Consolidating Ground: Centrifuge and Numerical Modeling

AbstractAlthough semi-open H piles have been widely used, geometric effects (GEs) on H-shaped piles in consolidating ground subjected to negative skin friction (NSF) and downdrag are still not well...