Large-diameter Steel Pipe Piles Research Articles

Influence of the Internal Friction Resistance on the Vertical Compressive Bearing Capacity of Large-Diameter Steel Pipe Piles

Current calculation methods for the vertical bearing capacity of steel pipe piles are predominantly designed for smaller diameters and do not account for the soil inside the pile. This necessitates an evaluation of their applicability to piles with diameters exceeding 2.0 m. This study aims to refine the existing formula for calculating vertical bearing capacity, as outlined in the Port Engineering Foundation Code of China, by investigating the vertical bearing capacity of large-diameter steel pipe piles through numerical simulations. By analyzing the relationship between the internal friction resistance of the soil core within the pipe and the bearing capacity for diameters ranging from 2 m to 10 m, this paper proposes a revised formula specifically tailored for steel pipe piles with diameters greater than 2 m, incorporating the effect of the soil core. The validity of the proposed formula is then confirmed through comparison with field data from four large-diameter steel pipe piles. The results demonstrate that the modified method proposed in this study performs better than the original formula when compared with the measured data.

Research on the vertical compressive bearing characteristics of offshore wind power steel pipe piles

In the absence of a comparison of static load test results for large-diameter steel pipe piles at home and abroad, optimize the design parameters based on the test pile results to guide later construction. This paper is based on the pile foundation design calculation method of API specification, as well as the relationship between the t-z, Q-z, p-y curve modes suggested by this specification, vertical ultimate bearing capacity, and stratum parameters. The conclusions and results obtained are limited to pile foundation calculations using API specifications. Analyze and back-analyze the results of static load tests on large-diameter steel pipe piles, and verify the pile foundation parameters. Combined with the data obtained from the test pile tests, analyze the stratum parameters to guide the optimization design of pile foundations in the construction drawing design stage of the offshore wind farm expansion project.

Research on Numerical Pile Testing Methods and Parameter Selection for Large-Diameter Steel Pipe Piles at Sea

Numerical test research and inverse analysis research on large-diameter steel pipe piles are particularly important for optimizing design parameters. Based on the field pile test results completed at an offshore wind farm in Jiangsu Province (including compression static load test, pull-out test, and horizontal load test), the actual geological conditions and loading process of the site were simulated, and numerical pile tests were systematically conducted. Sensitivity analysis of some key parameters was carried out, parameter value methods were proposed, and on this basis, the deformation failure modes of the foundation under different loading conditions, the mechanism and distribution law of pile side friction resistance under compression and pull-out conditions, and the relationship between foundation resistance and pile displacement under horizontal loading conditions (p-y curve) were studied.

Analysis and experimental research on the reliability of the connection between large-diameter bridge piles and caps

This article investigated the construction conditions of the pile foundation in the Wuxing section of the “Shanghai Suzhou Huzhou” railway bridge project. To test the reliability of large diameter connectors, it has established a finite element model with ABAQUS software for numerical simulation. Based on on-site tests, the reliability of the connection between the pipe pile and the cover steel was studied. According to the simulation results, when the load is P= 900 kN, the displacements of A2 and A3 steel pipe piles are 55.8 mm and 60.1 mm, respectively. The load-displacement relationship shows a high-order curve distribution. According to the results of on-site experiments, the displacements are 77.9 mm and 60.2 mm, respectively. The load-displacement relationship is linear. The results for the simulation and on-site testing are consistent. This study provides a basis to the research on the reliability of the connection between large-diameter steel pipe piles.

Su-Based Shaft Friction Design Method and Evaluation for Pipe Pile

The shaft friction in clay is essential to bearing capacity of pipe piles. Reasonable selection of design methods and parameters is very important for offshore piles. This paper focuses on the current popular vertical load design methods based on undrained strength for pipe piles, especially for offshore piles. Based on the database, the accuracy and reliability of various pile design methods based on undrained strength su in clay were reviewed. The small-scale model tests were conducted to evaluate su-based methods. For the shortcomings of small-diameter piles in the database, a field test of full-scale offshore pile was carried out and analysed. By comparing the calculated and the measured capacity for each method, the reliability of various design methods is evaluated for large-diameter piles. For the design methods based on undrained strength, it demonstrates the importance and reliability of the determination of undrained strength parameters. In view of the vertical loading conditions of offshore large-diameter steel pipe piles, reasonable suggestions for design methods and parameters determination are given.

Ground Stability Analysis in Non-Open-Cut Tunneling Method Using Small-Diameter Steel Pipe Piles

The non-open-cut method is used for constructing tunnels under existing roads without blocking traffic. Various non-open-cut methods use pipe roofs made of medium- and large-diameter steel pipe piles. However, the risk of ground settlement or heave is involved during the application of such piles. Therefore, research is conducted through model tests and numerical analysis on the non-open-cut method to investigate these problems using small-diameter piles. The progress of tunnel construction is divided into two repetitive steps. The first step (Stage 1) involves pulling back the pressure panel, and the second step involves propelling the precast structure (Stage 2). The behaviors of the pipe piles and ground displacement are analyzed according to the cover depth, tunnel size, existence and nonexistence of the shoe structure, and progress of tunnel construction. Small-diameter piles reduce the displacement during both stages. With a decrease in cover depth, the stress acting on the pile decreases during Stage 1 and increases during Stage 2. The presence of the shoe structure reduces the stress on the pile during both stages. The ground behavior based on the construction progress indicates that the ground settlement increases during Stage 1; however, no correlation is observed during Stage 2 at low depth.

Case study on pile running during the driving process of large-diameter pipe piles

ABSTRACTThe super-long and large-diameter steel pipe piles are often adopted for the construction of offshore oil platforms in deep sea. One constructability issue related to driving heavy pipe piles is the pile running. The term pile running refers to the quick penetration of a pile into the seabed as a result of its high self-weight and low resistance from the seabed. The unexpected pile running can cause the steel wire of the hammer to break or even the loss of the hammer. A case study of pile running at an oil platform is introduced in this paper. A simplified theoretical method is proposed to explain the mechanisms of the pile running in this case. A factor of friction degradation is proposed to calculate the dynamic skin friction from the static ultimate skin friction of surrounding soil. The comparisons between the predictions to the case history show that the proposed simplified method can be used to predict the pile running condition.

Dynamic Analysis of an Offshore Wind Turbine Including Soil Effects

Offshore wind turbines (OWTs) offer an attractive, sustainable solution to the impending global energy crisis. A major challenge in fixed-bottom OWT design is accounting for soil-structure interaction (SSI) under the influence of random dynamic loading from wind, waves and currents. Usually, SSI is either ignored in OWT studies or is incorporated by means of simplified foundation concepts like the apparent fixity model. OWTs in shallow water depths (less than 30 m) are mostly supported on monopiles - large diameter steel pipe piles driven into the subsoil. Monopiles transfer the dynamic lateral loads into the soil by bending action. The present work deals with the dynamic analysis of the NREL 5MW OWT on a monopile foundation, in Indian waters. It involves parametric studies on various clayey soil profiles - soft, medium stiff and stiff clay. An operational wind speed of 12 m/s and a sea state of 4 m significant wave height and 10 s spectral peak period are considered. The OWT design should ensure that the natural frequency is away from the forcing frequencies of wind, wave and rotor. A water depth of 20 m is considered. Hub-height aerodynamic loads are obtained using the NREL-FAST code, which is based on the blade-element momentum (BEM) theory. The hydrodynamic time domain analyses are performed in the FEM based coupled hydrodynamic - geotechnical software, DNV-GL - USFOS. USFOS makes use of the JONSWAP spectrum to generate irregular waves. Soil is represented by means of p-y, Q-z and t-z curves. Results indicate the significance of including SSI in OWT studies. Variation in response due to change in pile penetration depth and pile diameter are also highlighted. Stiffness of clay is the design driver for OWTs.

Use of Air Bag System for Instrumentation of Lateral Load Tests on Previously Installed Pipe Piles

Abstract A simple and inexpensive air bag system for allowing measurement of the deflected shape of laterally loaded piles has been developed. The air bag system may be used for hollow piles that have already been installed. The system includes an inclinometer casing that is held against the inner wall of the pile by an inflated air bag. Tests on small- and large-diameter steel pipe piles at two different locations showed that the air bag system performed reliably. The air bag system can allow measurement of p-y characteristics in lateral load tests on piles for which the possibility of such measurement may not have previously existed.

Evaluation of excess pore pressures and drainage conditions around driven piles using the cone penetration test with pore pressure measurements

Large-diameter steel pipe piles were driven as part of the foundations for the Alex Fraser Bridge near Vancouver, British Columbia. The piles penetrated through a normally consolidated marine clayey silt. As part of the geotechnical studies a multipoint piezometer was installed close to the pile group. A cone penetration test with pore pressure measurements (CPTU) was performed adjacent to one of the piles shortly after driving. During the CPTU through the clayey silt deposit, dissipation tests were performed to evaluate the pore pressures around the nearby pile. The CPTU results are compared with the pore pressures recorded at the multipoint piezometer, allowing for differences in radial distance from the piles. Excellent agreement was obtained between the CPTU and multipoint piezometer data, both showing large excess pore pressures around the piles. The CPTU dissipation data were also analyzed to evaluate the time required for dissipation of excess pore pressures around the piles. The upper half of the clayey silt deposit was inter bedded with thin sand and silt layers. The CPTU data showed that the thin sand layers were sufficiently large in extent to allow rapid dissipation of the pore pressures due to cone penetration but were not of sufficient extent to allow dissipation of the excess pore pressures from the much larger diameter piles. Key words: in situ, piles, pore pressures, CPT.