Numerical Modelling of Various Aspects of Pipe Pile Static Load Test

Due to the development of dedicated software and the computing capabilities of modern computers, the application of numerical methods to analyse more complex geotechnical problems is becoming increasingly common. However, there are still some areas which, due to the lack of unambiguous solutions, require a more thorough examination, e.g., the numerical simulations of displacement pile behaviour in soil. Difficulties in obtaining the convergence of simulations with the results of static load tests are mainly caused by problems with proper modelling of the pile installation process. Based on the numerical models developed so far, a new process of static load test modelling has been proposed, which includes the influence of pile installation on the soil in its vicinity and modelling of contact between steel pile and the soil. Although the presented method is not new, this is relevant and important for practitioners that may want to improve the design of displacement piles. The results of the numerical calculations were verified by comparing them with the results of pipe pile field tests carried out in a natural scale on the test field in Southern Poland.

Installation of Conductor Supported Platform CSP at X Field

This technical paper presents the offshore installation execution work of Conductor Supported Platforms (CSP) at ‘X’ field. The knowledge sharing was based on the successful installation of three (3) numbers of CSP for ‘X’ development project. The platforms were installed at approximately of 70m water depth and encountered technical challenges during offshore execution. ‘X’ field is located about approximately 45km North West of Miri, Sarawak. The CSPs were installed by Derrick Barge (DB) via double blocks crane upending method for the substructures and conventional lifting method for the topsides. The CSP was designed for 70 meters water depth with four (4) numbers of vertical legs, four (4) numbers of skirt piles, and one (1) number of pin pile. The weight of the topside was about 600MT, meanwhile the substructure was about 1100MT respectively. These CSPs marked as a pioneer in the installation of its kinds at 70m water depth in COMPANY. The concept required high accuracy of detailed offshore installation engineering. This configuration however had caused some challenges during installation. Among the major challenges were issues on the pin-pile verticality, substructure levelness and upending activities via double blocks crane upending method. The effective strategies were adopted to improve the on-bottom stability by installing pin pile prior to substructure set down. The pin pile was installed by utilizing Subsea Fast Frame (SFF), in order to achieve pin pile's verticality. The crucial part during pin pile installation was to ensure meeting the verticality accuracy and minimum tolerance may high potentially impact the substructure install ability and meeting level requirement. However, due to a big annulus gap at pin pile sleeve of the substructure had caused prolong in levelling operation. In order to improve subsequent platforms levelling operations, a set of centralizers were introduced and installed after confirming the pin pile verticality result, in order to reduce the annulus gap. Despite all the challenges aforementioned, the installation of CSPs were completed successfully and most importantly with Zero Lost Time Injury (LTI).

Model Study of a Single Pile With Varied Configuration in Sand

In this experimental work, the influence of pile cross-section with varied configurations on the axial compression load capacity of a single pile and related settlement in sand are investigated. The influence of relative sand density (Dr), the pile length to diameter (L/D) ratios and the pile installation techniques are presented. A testing program comprising seven model steel piles with varied shapes of 20 mm width/diameter was conducted. The tests are performed on model piles with the pile length to diameter ratios of 10 and 30 installed in the three cases of sand modeling as loose, medium dense and dense sand. Results indicated that, the rectangular pile is the optimization cross-sectional under the same pile geometry and soil conditions. Also, the increase of the relative sand density has a significant influence on the ultimate compression pile load. Furthermore, the ultimate axial loads of flexible piles in the case of loose sand using the non-displacement method were found to be increased by 119%, 114%, 143%, 82% 139%, 89% and 100% comparing with the ultimate axial loads of rigid piles for the seven models of closed-ended pipe, open-ended pipe, conical base pipe, square closed-ended, square open-ended, tapered and rectangular piles respectively. While, these percentages were found to be increased by (49%, 37%, 26%, 78%, 35%, 71% and 91%) and (77%, 50%, 13%, 116%, 61%, 89% and 85%) in the cases of medium dense and dense sand respectively. The results also indicated that, piles installed in sand using jacking technique have more resistance compared with piles installed in sand using non-displacement technique.

Effects of Pile Installation on Existing Tunnels Using Model Test and Numerical Analysis with Medium Density Sand

Vital underground structures such as sewers, power transmission lines, subways, and underpasses are potentially vulnerable to adverse effects from aboveground construction. In this study, the influence of pile installation on nearby existing tunnels was investigated. Both a laboratory model test and finite-element numerical analysis were conducted. Twelve different combinations of horizontal and vertical offsets between the pile and the tunnel were investigated. Different surcharge loads (allowable and ultimate) were also considered. In this way, the appropriate separation distance between the existing tunnel and the piles was established for sandy, medium-compaction soil. Although this study considers simple ground conditions, it facilitates safe construction by confirming the appropriate separation distance and comparing the areas that cannot be penetrated by the structures of each standard.

Study on the Correlation between Soil Consolidation and Pile Set-Up Considering Pile Installation Effect

In saturated fine-grained soil, the development and dissipation of excess pore water pressure (EPWP) during and after pile jacking change the effective stress of the surrounding soil, and thereby affect the pile set-up. In this paper, the entire process of steel-pipe pile jacking (the installation process and the subsequent consolidation phase) is simulated with three-dimensional (3D) finite element models, considering the pore water effect. After the model verification, a comprehensive numerical analysis was performed to investigate the development and dissipation of EPWP, changes in soil stress state, and the side shear resistance of pile with time after installation. On this basis, not only the influence of ks, cu, E, and OCR on EPWP generation during pile jacking and subsequent soil consolidation effect after pile installation but also the correlation between pile set-up and EPWP dissipation is investigated.