Sustainable slow maintained pile load test

Slow maintained load test is widely used by contractors in Malaysia to ensure the driven pile could accommodate the design load of the structure. Slow maintained load test is a test to determine load-settlement curve and pile capacity for a period of time using conventional load test. Conventional static pile load test equipment is large in size thus making it heavier and takes a long time to install. In addition, it consumes a lot of space which causes congestion at construction sites. Therefore, the objective of this thesis is to conduct a conventional load test by replacing the pile kentledge load with anchorage and reaction pile. Preparations of ten designs comprising six commercial designs were reviewed. In addition, four proposed designs were suggested for the setup. Final design was produced based on its safety factors and criteria referred via literature review. The test frame consists of reaction frame with four reaction helical pile with two helixes per reaction pile. The deformation shapes, safety factor, stress, and strain of the design and finite element of the model has been analysed with the use of SolidWorks and Plaxis 3D software. SolidWorks software emphasizes on the model load-deflection relationship while Plaxis 3D ensures a correlation of reaction between pile uplift force and soil. Then, the model was tested on site to determine the relationship between physical load-deflection and pile-soil uplift force. The results of uplift force and displacement for numerical and physical test were nearly identical which increment of load-displacement graph pattern. The higher the uplift force, the higher the displacement obtained. In conclusion, the result obtained and the design may be considered as a guideline for future application of sustainable slow maintained pile load test

Investigation into the effect of uncertainty of CPT-based soil type estimation on the accuracy of CPT-based pile bearing capacity analysis

Cone Penetration Test (CPT or CPTu) is commonly used for estimating soil types and also for the geotechnical design of pile foundation. However, the level of agreement between the CPT-based soil types and the traditional identification of soil types based on samples may vary significantly; and it is not clearly understood if this variation has any sort of relationship with the CPT-based pile design. To investigate into this area, a ground investigation trial was carried out at six different locations as part of a highway scheme in East of England. At each location the trial comprised one CPTu adjacent to one borehole (BH) with conventional sampling and laboratory testing. The soil types were estimated from the CPTs and compared with the boreholes findings, and the levels of correlation between them were established. Similarly, the ultimate bearing capacity of a typical bored pile based on the CPTs and on the BHs were calculated and compared. Despite the variable level of disagreement of the CPT-based soil type estimation with the BHs findings, the pile capacity based on CPT data was found to be generally consistent with the values obtained from the traditional BHs-based pile design

Bored pile design in stiff clay II:Mechanisms and uncertainty

The soil mechanics related to pile design in clay has been the subject of substantial engineering research. In a companion paper, various codes of practice were reviewed showing the effect on pile capacity of the different global factors of safety that emerge from the various partial factor combinations for the ultimate limit state. Factors of safety are generally specified based on the opinions of experts. In this paper an assessment will be made of various objective procedures that can be used to reduce uncertainty in the design process, especially regarding the adoption of a pile resistance model and the selection of a soil strength profile as part of a ultimate limit state check, and the estimation of pile head settlement in the context of a serviceability limit state check. It is shown that both total stress and effective stress calculation methods are applicable in London Clay. Estimates of settlement using a non-linear soil stress–strain relationship are made and compared with published data. It is shown that the compression of the concrete dominates the settlement of long piles. Given the low settlements observed, recommendations are made for a reduction in standard factors of safety for bored pile design in stiff clays. </jats:p

Numerical evaluation of the soil behavior during impact driving of pipe-piles

During the impact driving of pipe-piles, the soil is influenced in different ways including the void ratio, stress distribution, and plugging formation. Such effects may play an important role in structural design criteria such as the pile’s lateral support provided by the soil. Hence, this work is focused on investigating the change in the mechanical characteristics of the soil during impact driving using an advanced numerical analysis tool which is validated against an experiment. The investigation includes the pile penetration behavior, plugging formulation inside the pile, and the change of the lateral stress in the soil during the pile installation. The proposed numerical model is shown to provide similar results compared to experimental measurements. The void ratio of the soil is influenced due to pile driving up to a lateral and vertical distance of 2D and 1D, respectively, where D is the pile diameter. Compared to the initial void ratio, the soil inside the pile experienced loosening about 20% while the soil outside is densified about 30% during driving. Moreover, the induced lateral stress inside is more than the one outside the pile, indicating the formation of plugging. Compared to the initial lateral stress state, the pile installation increased the lateral stress up to four times inside and two times outside the pile. Based on the findings of this work, the effects of driving on soil mechanical properties are not minimal and may affect the pile performance including the lateral resistance of the pile. By using the numerical approaches such as one in this study, the evaluation of the various effects on the soil due to pile driving and gaining a better understanding of the such complex problems are possible

Load and Resistance Factor Design of Bridge Foundations Accounting for Pile Group–Soil Interaction

Pile group foundations are used in most foundation solutions for transportation structures. Rigorous and reliable pile design methods are required to produce designs whose level of safety (probability of failure) is known. By utilizing recently developed, advanced, two-surface plasticity constitutive models, rigorous finite element analyses are conducted. These analyses are for axially loaded single piles and pile groups with several pile-to-pile distances in various group configurations installed in sandy and clayey soil profiles. The analyses shed light on the relationships between the global response of the pile-soil system (development of shaft and base resistances) and the behavior of local soil elements (e.g., shear band formation). The influence of the group configuration, pile-topile spacing, soil profile, and pile head settlement on the group effects are studied. Mechanisms of pile-soil-pile interactions in pile groups are revealed. Pile efficiencies for individual piles and the overall pile group are reported for use in pile group design. The instrumentation, installation, and static and dynamic testing of a closed-ended, driven pipe pile in Marshall County, Indiana is documented. The test results along with two other case histories are used to verify the new Purdue pile design method. Probabilistic analyses are performed to develop resistance factors for the load and resistance factor design, LRFD, of pile groups considering both displacement and non-displacement piles, various soil profiles, and two target probabilities of failure. The pile design equations, pile group efficiencies and resistance factors together form the LRFD pile design framework. Two step-by-step design examples are provided to demonstrate the LRFD pile design procedures for single piles and pile groups

Screw pile design optimisation under tension in sand

Many applications in offshore engineering, such as floating or jacket-founded wind turbines or wave energy converters, require a significant uplift capacity of their foundations to be kept in place. Straight-shafted or suction piles in sands have a limited uplift capacity as they resist by friction only. In contrast, screw piles or screw anchors are a promising solution which provides a similar capacity to plate anchors and does not generate disturbance for marine mammals (e.g. from pile driving operations). The optimisation of the screw pile design does not rely only on the geotechnical assessment of the uplift capacity based on soil strength, but also on operational (installation requirements) and structural (helix bending, core section stress, limiting steel plate thick-ness) constraints. This paper develops a methodology for the design optimisation of screw piles under pure ten-sion in sand, incorporating all of these constraints, based on simplified analytical or semi-analytical approaches. The results show that the uplift capacity provided by an optimised screw pile is able to meet the needs of the offshore industry, across a range of soil densities and different applications (jacket foundation pile or tension leg platform anchor), providing that adequate installation plant could be dev

Design of a 10T Flake Pile Roller Stand

This article provides a summary of the design and operating parameters for a 10T Flake Pile Roller Stand. The 10T Flake Pile Roller Stand is designed to reduce the force required to install conveyor belt that has been pre-spliced and assembled into a flake pile. The performance requirements of the 10T Flake Pile Roller Stand were initially determined through Excel spreadsheet calculations. Finite element analysis was used to determine the structural stresses induced by the belt tension during operation within the pulley shell, the pulley shaft and the stand. The maximum belt tension was 10 tonnes. Australian Standard AS3990 Mechanical Equipment–Steelwork has been utilized for determining the suitability of the design. The design meets the requirements of the standard for the proposed belt tension

Driven Pile Foundation in Coral Sand, Jeddah, Saudi Arabia

Tubular steel piles, 1.42 meter in diameter, were driven into coral and coral contaminated sands to support marine structures on the Red Sea coast of Saudi Arabia. The paper describes the design evolution process, highlights the pile test program conducted on site to verify design and compares pile design penetration with actual penetration lengths. Despite corrections introduced to the design using site-specific load tests; the final design overestimated capacities in over 50 per cent of the total piles driven. The unpredictable and erratic pile behaviour observed during pile driving ascertains the need for more appropriate pile design and installation methodology for piles driven in coral and coral contaminated formations

The Average Temperature of Energy Piles

The geotechnical design of energy piles requires confirmation that the foundations can continue to carry safely the required load from the overlying structure and that no detrimental effects from the additional imposed temperature changes will occur. These additional design checks require assumptions to be made about the temperature changes within the pile. However, there is no universal approach for determining these, and routine application of over-conservative pile temperatures can lead to unrealistically adverse geotechnical design scenarios. This paper considers how the average temperature of a pile can be determined based on the analysis steps already carried out for the thermal design. The aim is to be able use the calculated fluid temperatures, along with readily available pile and ground parameters, to provide better assessments of the actual pile temperature so that the outputs of the geotechnical design can be improved. Two dimensional numerical simulations are used to determine the average pile temperature for different pipe, pile and concrete properties. The results of the simulations are compared with analytical approaches, allowing these to be validated for use on a routine basis. It is shown that the temperature of the center of the pile, which can be determined easily by analytical methods, can be used as a proxy for the average pile temperature