The problem that occurs during open-ended steel pipe pile installation is that soil enters the pipe and develops frictional resistance that further prevents soil intrusion, causing plugging and ...increased piling resistance. The steel pipe pile with tapered tip (tapered tip pile) restrains plugging and piling resistance. To apply the tapered tip pile as end-supported piles, it is essential to clarify the bearing capacity mechanism suitable for tapered shapes. In addition, it is not possible to apply the bearing capacity mechanism of the flat tip pile (straight pile). The purpose of this paper is to reveal the piling performance and the bearing capacity by experiment and to propose the bearing capacity model based on the mechanism in a fully plugged mode. Experiments were conducted on model-tapered pipe piles installed in sands with different soil conditions to investigate the effects of the pile shape on piling performance and bearing capacity. Extending the combination theory of Prandtl and cavity expansion, bearing capacity model and formula incorporating shape parameters were derived. Theoretical values were good agreement with the experimental results.
This paper presents a case study involving construction of eight rock-socketed piles with diameter of 8.0 m in the primary part and enlarged diameter of 9.5 m at the base. These mega piles were ...constructed in a 29.8–33.8 m deep excavation pit. They were believed to be the largest rock socketed piles in the world at the construction time. The project was a critical part of building the 606 m tall Shenzhen PingAn Financial Center. Challenges in the construction of the mega piles include strict requirement on controlling the deformation of the surrounding structures, the presence of fissure groundwater in the bedrock, the excavation of pile holes in moderately weathered to slightly weathered rock, the installation of large reinforcement cages in small construction space, and the placement of massive concrete (i.e., with total volume of more than 1800 m
3
per pile). Other interesting features include an in-service metro line existing along the north side of these mega piles within distance of only 21 m, and end-bearing of piles on a strong intact granite rock with maximum unconfined compressive strength of 88.2 MPa. The end bearing capacity of piles was computed based on the rock quality designation index. During the construction, in situ tests were performed to monitor and examine the quality of the piles.
Pretensioned spun high strength concrete (PHC) piles are a commonly used type of pile, while approximately 60% of the pile′s strength is only used in the design bearing capacity. Because of the ...limited support capacities of PHC piles, applying PHC piles to high-rise buildings or soft ground is inefficient. Extended end (EXT) piles are a new type of pile that can reduce the waste of pile strength and increase the ground bearing capacity. This study investigated the behavior of EXT piles through a field test and it was confirmed that the bearing capacity of the EXT pile is better than the PHC pile. The increased bearing capacity of EXT piles also influenced work duration and project cost.
In recent years, works to improve existing structures and strengthen their seismic resistance have increased. Pile construction in narrow spaces is constrained by the site and the construction ...process. Therefore, a construction method of soil-cement composite pile using a mechanical agitator was developed. The purpose of this study is to clarify the compression characteristics of pile tip for soil-cement composite pile. This paper briefly summarizes the construction method, then discusses the results of the compression model tests, and finally summarize the results of simulation for the compression model tests by the three-dimensional analysis using the finite element method.
Determination of axial capacity of piles has been a challenging problem since the beginning of the geotechnical engineering profession. The axial capacity of a single pile can be estimated by summing ...the skin friction capacity and the bearing capacity of the pile toe. In this paper, an attempt is made to numerically analyze the end bearing capacity of drilled shafts in sand. The numerical results obtained were compared with the results of pile load test. The comparison between numerical and experimental base load-settlement curves showed that the proposed numerical analysis produces satisfactory predictions. Then, variations of the end bearing capacity of drilled shafts versus embedment depth and pile diameter were studied. Numerical results showed that with the increase in embedment depth and pile diameter, the end bearing capacity increases, but with a decreasing rate. Moreover, the range of failure zone surrounding the pile tip is discussed.
The computing of end-bearing capacity of pile has vital significances for foundation design while the foundations analysis is usually problematic due to those diverse soils and engineering ...conditions. Though various CPT-based methods which have already been applied in numerous huge engineering practices are available for the analysis of pile foundation bearing capacity home and abroad, there still seemed lacking legitimate guidance assisting to select these formulations quite effectively. In this paper, five CPT-based design methods are compared in deep, the realization through computer program is also presented, with the capacity data accumulated from pile engineering coming into mind, we are on the way to making designers choose better methods during the designing process.
An Incompletely End Supported Pile (IESP) is a pile in a soft soil layer underlain by a hard soil layer that does not reach the bottom hard layer in practice. This study estimates the end bearing ...capacity of IESP by using an inhouse Rigid Plastic FEM code (RPFEM), considering shear strength non-linearity of soil against confining pressure, and soil-foundation interaction. The effect of the distance between the pile tip and the bottom hard soil layer (d/B) on the end-bearing capacity of IESP was mainly investigated for three types of soil: cohesive soils, cohesionless soils and intermediate soils. Also, theratio (r) of the end bearing capacity of the pile when it reaches the bottom hard layer to that of the pile when the bottom layer has no influence was was considered. By considering the shear strength non-linearity, the end bearing capacity was accurately estimated. The estimations were consistent with previous analytical, experimental and numerical solutions. It is found that the end bearing capacity inversely decreases with the distance d/B and becomes constant around d/B = 3. Based on the results, a formula for estimating the end bearing capacity of IESP is proposed. Comparisons with methods in existing literature confirmed the reliability of the proposed equation.
This study investigates the load transfer mechanism that includes the effect of helix bending deflection on end-bearing capacity, distribution of ground pressure under the helix and soil deformation ...around the screw pile. The helix to shaft diameter ratio of 2.5 and 2.8 with a strong helix and a weak helix were used. The model ground was prepared with fine sand at 80% of relative density. To investigate the load transfer mechanism, the experimental tests were modelled in a 3D finite element code. A good agreement between the experimental and numerical approaches was found. The numerical analyses showed that large influence zone exists under screw pile with strong helix, which resulted in higher mobilized soil shear strength that contributed to higher end-bearing capacity. In the case of strong helix, uniform pattern of pressure distribution was observed under the central shaft and the helix. Similar pattern of pressure distribution under the central shaft was observed in weak helix case but the pattern of pressure distribution under the helix changed from uniform to triangular to trapezoidal at various stages during the load test. The normalized end-bearing capacity decreased linearly with the increase in normalized helix bending deflection in both approaches, i.e. experimental and numerical.
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