Pile Tests Research Articles

Optimization of Load-transfer Functions for a Large-diameter Pile in Multi-layered Geological Conditions via a Stochastic Search Algorithm

The paper presents the combination of the load transfer method (computational model) and the genetic algorithm (optimization model) for the automated inverse analysis of instrumented pile load tests. The output of this process are the input parameters governing the shape of the load-transfer functions and thus the prediction accuracy when the load-transfer method is used as a design tool for deep foundations. The optimization problem is converted into an unconstrained task by applying the static penalty approach. Two types of measurements are considered in a newly proposed objective function: the load-displacement curve monitored in a pile head and the axial force profiles along a pile derived from strain gauges. Firstly, the local sensitivity analysis via the Design of Experiments is carried out to identify the parameters of the genetic algorithm which significantly influences the rate of convergence during the optimization process. Subsequently, a fully automated inverse analysis of the loading test of the large-diameter bored pile in multilayered geological conditions is presented. The simultaneous combination of two instrumentation sources leads to a stable unique solution with a sufficient match between the prediction and measurements despite a larger number of unknown – optimized variables.

Optimizing bucket-filling strategies for wheel loaders inside a dream environment

Reinforcement Learning (RL) requires many interactions with the environment to converge to an optimal strategy, which makes it unfeasible to apply to wheel loaders and the bucket filling problem without using simulators. However, it is difficult to model the pile dynamics in the simulator because of unknown parameters, which results in poor transferability from the simulation to the real environment. Instead, this paper uses world models, serving as a fast surrogate simulator, creating a dream environment where a reinforcement learning (RL) agent explores and optimizes its bucket-filling behavior. The trained agent is then deployed on a full-size wheel loader without modifications, demonstrating its ability to outperform the previous benchmark controller, which was synthesized using imitation learning. Additionally, the same performance was observed as that of a controller pre-trained with imitation learning and optimized on the test pile using RL.

PELAKSANAAN PEKERJAAN STRUKTUR BAWAH BANGUNAN GEDUNG SERBAGUNA GELANGGANG GENERASI MUDA MAJALENGKA

The Majalengka Regency Youth Center Development Project is an important historical milestone for infrastructure development in the Majalengka Regency area. The concept of an oval-shaped building like a stadium gives uniqueness to the design of the foundation of this building. Basically, the substructure is a very vital component for the success of a building, so the author is interested in looking further into the substructure, especially in work methods or work implementation. This research uses a qualitative approach, which can be interpreted as directly describing the work of the lower structures in the project which is used as the research object. The implementation of the lower structure work starts with the piling work and then continues with the pile cap work, carried out in stages using a zone system. In the realization of the implementation of the lower structure work on the GGM project, namely the piling work starting from site preparation, mobilization and set up of HSPD piling tools, measuring pile points, driving piles using the hydraulic jack-in pile method, testing piles, and pile head treatment, continued with the implementation of pile cap work starting from preparation, measurement and bow plank, soil excavation, installation of formwork, reinforcement and casting.

Lateral capacity of group helical piles in sand: an experimental and numerical study for sustainable infrastructures

ABSTRACT Helical piles are integral to support resilient infrastructures subjected to axial and lateral loads. This study explored model-scale testing of group helical piles in cohesionless soil in a rigid box. Initially, a total load of 5000 N is applied to the pile raft model, followed by a lateral load of 1600 N. Nine model tests are performed with a configuration of four, six, and nine, having conventional, single helical, and double helical piles. The data logger facilitated data collection using MATLAB software, and the load was increased at rate of approximately 4.9N/sec. The computed average reduction in the displacement of Single and Double Helical Pile Rafts is observed as 36.43% and 55.71%, respectively, compared to Conventional Pile Rafts. The addition of a second helix further reduced lateral displacement by 19.27%. Numerical analysis on Plaxis-3d showed that the experimental and numerical results are in good agreement.

Graph-Analytical Method for Calculating Settlement of a Single Pile Taking into Account Soil Slippage

Most of the existing methods of pile settlement calculation, including normative methods, do not fully take into account the processes occurring in the soil when loads are transferred to them and the changes in the properties of the contact zone soils. This leads to underutilisation of the bearing capacity of the soil, and the calculated settlement value may differ several times from the real values. In this paper, a graph-analytical solution to the problem of interaction of a single pile with a three-layer soil foundation is proposed to determine the settlement, taking into account the complex nature of the pile operation and the processes occurring in the soil when loads are transferred to them. The proposed method allows to use the non-linear behaviour of the soil on the lateral surface and under the tip of the pile, the possibility of its detachment and slippage after reaching the ultimate strength of the soil, changes in the properties of the contact zone soils, and the load distribution on the pile between its lateral surface and the tip. To verify the proposed graph-analytical solution, a comparative analysis was performed with the numerical method in the Plaxis 2d software (version 21.00.01.7) and with the results of static tests of piles at the construction site. To determine the strength reduction factor at the contact of soils with concrete, laboratory tests were carried out on a direct shear apparatus. Based on the results of the performed calculations, graphs of the dependence of settlements on loads were plotted, conclusions were drawn about the possibility of using the graph-analytical method, and prospects for further development and improvement of the graph-analytical method were proposed.

Small-scale physical modelling of vertically loaded, cyclically thermally-activated helical piles

To investigate the use of thermally-activated helical piles in shallow geothermal energy systems, a 1-g modelling study was conducted. Helical piles with either a single- or double- helix were installed in a medium dense, dry sand, and subjected to mechanical, thermal only and thermo-mechanical loading. The results indicate that during the thermal tests (1 – 3 cycles), a small upwards residual displacement was observed and pile head movements ranged between about 90% and 100% of the free expansion of the pile shaft above the shallowest helix, suggesting that the helices fixed the shaft and little restraint was offered by the surrounding soil. In the thermo-mechanical tests (30 thermal cycles), the pile head developed irrecoverable settlement as a function of the number of helices (more helices, less settlement) and initial load (higher load, greater settlement). No significant alteration in pile axial stiffness or resistance was found for piles with zero mechanical load that underwent only a few thermal cycles; however, an increase in stiffness and resistance, beyond that due to inherent variability in the test setup, was observed for piles with an initial load and following a large number of thermal cycles. The testing of thermally-activated helical piles in sand has confirmed that the response is similar to conventional piles and that thermal ratcheting effects can be managed by the application of suitable margins of safety in design and/or the use of multi-helix piles.

Development of improved finite element formulations for pile group behavior analysis under cyclic loading

AbstractThe effect of cyclic loading is an essential factor leading to progressive soil strength degradation. Therefore, a comprehensive analysis of the pile‐soil system behavior under cyclic loading is required to ensure the stability of pile group. There is room for improvement in the inherent constraint of the conventional numerical model in terms of approximating the soil resistance distribution along the pile by point loads at element nodes, necessitating a specific element that integrates considerations of pile group effect and cyclic loading within a unified framework. This study aims to develop a newly specific type of element for efficiently predicting nonlinear behavior within the pile‐soil system, addressing simulations involving nonlinear pile‐soil interaction, pile group effect, and cyclic loading. Modified element formulations based on soil stiffness matrices and soil resistance vectors specifically address pile group effect and consider parameters that influence pile behavior under cyclic lateral loading. The numerical solution procedure with Newton‐Raphson iteration allows the calculation of pile responses in geometric and material nonlinear analyses. The validation of the proposed method includes several examples, comparing it with existing numerical solutions and experimental tests of single piles and pile groups under cyclic loading. These comparisons further support the consistency of the proposed method with measured data and validate its accuracy in considering group effect and cyclic loading. The parametric study illustrates the ability of the proposed method to capture cyclic loading parameters while considering the influence of the number and magnitude of load cycles, the cyclic load direction, and the installation methods.

Physical Model Tests of Piles under Freeze–Thaw Cycles Subjected to Individual and Combined Loads

Physical Model Tests of Piles under Freeze–Thaw Cycles Subjected to Individual and Combined Loads

Identification of bored pile defects utilizing torsional low strain integrity test: Theoretical basis and numerical analysis

The torsional low strain integrity test (TLSIT), known for its advantages such as a smaller detection blind zone, improved identification of shallowly buried defects, stable phase velocity for signal interpretation, and better adaptability for existing pile testing. However, it lacks a comprehensive understanding of the authentic three-dimensional (3D) strain wave propagation mechanism, particularly wave reflection and transmission at defects. To address this gap, a novel 3D theoretical framework is introduced in this context to model the authentic 3D wave propagation during the TLSIT. The proposed approach is validated by comparing its results with those obtained from 3D finite element method (FEM) simulations and simplified 1D (one-dimensional) and 3D analytical solutions. Additionally, a parametric study is conducted to enhance insights into the formation mechanism of high-frequency interference observed during the TLSIT. Finally, a defect identification study is performed to provide guidance for interpreting the wave spectrum in terms of defect characteristics.

Load–displacement behavior of helical pile using Frustum Confining vessel (FCV) and full-scale testing in Babolsar sand

Nowadays, the use of deep foundations in various civil engineering projects, especially in marine and coastal structures, has been increasing. One type of deep foundations are helical pile foundations, which have gained significant attention in recent decades. This research investigates the load–displacement behavior of different helical pile configurations regarding geometry, i.e., helix diameter and spacing ratio (S/D) in two different soil densities under pullout and compressive loading conditions via the FCV-AUT device. Babolsar sand from the southern coast of the Caspian Sea was utilized for advancing this study. Additionally, four full-scale pile tests were conducted on the Caspian Sea coast under both grouted and non-grouted conditions for pullout and compressive loading. The results indicate that increasing the helix diameter, soil density, and S/D ratio enhances the compressive load-bearing capacity. However, in tensile loading, the ultimate load decreases with an increase in the spacing ratio. Furthermore, the grouting process in the three-helix pile exhibits better performance compared to the two-helix pile, potentially increasing the pile capacity up to 30%. In conclusion, the results obtained from the FCV device, utilizing scale theory, have been generalized to the large-scale pile test results in the field, are representative of in agreement and compatible.

Cyclic loading experiments and numerical analysis of laterally loaded piles constructed in marine soil

This study aims to thoroughly analyze the lateral loads that impact tubular steel piles, which are extensively employed in the construction of coastal structures. The ASTM D 3966 standard was followed for conducting field tests on test piles installed at the Mersin International Port. The “time-displacement” and “load-displacement” curves were obtained from the cyclic loading test of the laterally loaded piles at the construction site. The finite elements models of the tests conducted on the construction site with the same parameters was built to perform numerical analysis. At the end of the analysis, it was determined that the numerical model's results were highly consistent with those obtained from the field test. After verifying the field experiments with numerical models, a parametric study was conducted. Parametric studies were conducted to compare the lateral displacements of tubular steel piles with variations in pile diameter, wall thickness, and load application height effect. The relationship between pile head displacements and these parameters appears to be almost linear. It is noteworthy that a change of approximately 10 percent in these parameters shows a correlation with changes of up to 3 percent in deformations.

Analysis on the cooperative variation law of pile-soil temperature field in Island permafrost region

To determine the cooperative variation laws of temperature fields in bridge concrete piles and the surrounding frozen soil during the freezing process in high-latitude, low-altitude insular permafrost regions, we utilized a practical bridge construction project within the frozen soil area of the Daxing'an Mountains, China. This served as the foundation for developing a method to remotely and dynamically monitor the temperatures of piles and soil in permafrost regions, enabling continuous, automatic monitoring of pile-soil temperature data. Employing this automatic temperature monitoring system, we collected temperature data from two 15-m-long concrete bored piles before and after freezing, and monitored the freezing process of the pile foundations in real-time. The cooperative variation laws of the pile-soil temperature field over time were summarized, and a calculation equation for the pile foundation's freezing time was established based on finite element analysis results. Monitoring and analysis reveal that under the influence of the frozen soil temperature field, the pile foundation initially freezes from the bottom up in a unidirectional manner. When the atmospheric temperature falls below 0 °C, the pile foundation freezes simultaneously from both the upper and lower directions. Post-freezing, the internal temperature of the pile body aligns with the surrounding soil temperature, with a temperature difference of less than 0.1 °C at the same depth. For similar in-place temperatures, the freezing time for a test pile with a 1.2m diameter is 1.14 times that of a 1.0m diameter test pile. The range of the hydration heat effect of cement concrete extends 1–2 times the pile diameter.

Assessment of interfacial friction angles of sand-structural materials

This research evaluates the interfacial friction angles of sand-structural materials (i.e. concrete, steel, and wood) from direct shear and model pile tests data. Some variable parameters are considered for performing laboratory tests such as shearing rates (0.05, 0.5, 1.0, 2.0, and 2.5 mm/min.), pile diameters (38.1, 76.2, and 101.6 mm), and normal stresses (27, 55, and 81 kPa). The validated shearing rates are found to be 8.7% and 4.3% in cases of direct shear and model pile tests respectively, which may represent a good accuracy of experimental tests. According to the direct shear test results, the interfacial sand-concrete and internal friction angles are equal at shearing rate of 2 mm/min. The interfacial friction angles are increased with the increment of pile diameters because of slip dilation impact of small diameter pile. The interfacial friction angle of sand-wood pile shows the higher value because of lower self-weight and stiffness of wood compared to the other structural materials. There is a scope for further research by conducting numerical analysis and deriving analytical formulations for obtaining explicit solution.

Influence of Pile Foundation Construction on Existing Tunnels in a Metro Protection Area: Field Test and Numerical Simulation

On the basis of the Fengqi Chaoming project in Hangzhou City, Zhejiang Province, China, this paper investigates the influence of pile foundation construction on the existing tunnels in a metro protection area to ensure the stability and safety of the pile foundation construction in the area of Hangzhou Metro Line 2 through in situ pile tests and numerical simulations. The test results show that the pile foundation construction has a certain influence on the existing metro tunnels, and the degree of influence gradually decreases as the distance between the pile foundation and the metro tunnel increases. The corresponding impact level for the pile foundation at 12 m from the tunnel is 1.06 mm, and that for the pile foundation at 4.9 m from the tunnel is 1.18 mm. Different types of pile foundations also lead to different degrees of influence. The maximum settlement corresponding to triaxial cement mixing piles is 1.89 mm, while the hard-method occlusal piles is 1.18 mm. The monitoring point of the metro tunnel with the smallest distance from the pile foundation experiences the largest deformation, but several sets of deformation data meet the requirements of the deformation control index, indicating that the pile foundation construction is safe and controllable.

New Design Criteria for Long, Large-Diameter Bored Piles in Near-Shore Interbedded Geomaterials: Insights from Static and Dynamic Test Analysis

This paper presents an analysis of long, large-diameter bored piles’ behavior under static and dynamic load tests for a megaproject located in El Alamein, on the northern shoreline of Egypt. Site investigations depict an abundance of limestone fragments and weak argillaceous limestone interlaid with gravelly, silty sands and silty, gravelly clay layers. These layers are classified as intermediate geomaterials, IGMs, and soil layers. The project consists of high-rise buildings founded on long bored piles of 1200 mm and 800 mm in diameter. Forty-four (44) static and dynamic compression load tests were performed in this study. During the pile testing, it was recognized that the pile load–settlement behavior is very conservative. Settlement did not exceed 1.6% of the pile diameter at twice the design load. This indicates that the available design manual does not provide reasonable parameters for IGM layers. The study was performed to investigate the efficiency of different approaches for determining the design load of bored piles in IGMs. These approaches are statistical, predictions from static pile load tests, numerical, and dynamic wave analysis via a case pile wave analysis program, CAPWAP, a method that calculates friction stresses along the pile shaft. The predicted ultimate capacities range from 5.5 to 10.0 times the pile design capacity. Settlement analysis indicates that the large-diameter pile behaves as a friction pile. The dynamic pile load test results were calibrated relative to the static pile load test. The dynamic load test could be used to validate the pile capacity. Settlement from the dynamic load test has been shown to be about 25% higher than that from the static load test. This can be attributed to the possible development of high pore water pressure in cohesive IGMs. The case study analysis and the parametric study indicate that AASHTO LRFD is conservative in estimating skin friction, tip, and load test resistance factors in IGMs. A new load–settlement response equation for 600 mm to 2000 mm diameter piles and new recommendations for resistance factors φqp, φqs, and φload were proposed to be 0.65, 0.70, and 0.80, respectively.

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.

Learning approaches to cost–benefit decision analysis of pile designs from site investigation plans

ABSTRACT The study introduces an approach to pile design optimisation in geotechnical engineering, integrating both Reinforcement Learning (RL) and Machine Learning (ML) algorithms with Cost–Benefit Decision Analysis (CBDA). The study explores three Site Investigation Plans (SIPs), described as Current (CSIP), Actual (ASIP) and Optimal (OSIP), that can be used to address uncertainties in subsurface conditions and pile design. RL is used to determine the optimal action in transitioning between these interrelated SIPs. Apart from the SIPs, the optimal action is also shown to depend on structural variables for the pile design. These variables are used in ML algorithms, such as Random Forest (RF), Gradient Boosting Machine (GBM) and Support Vector Machine (SVM), to predict the optimal action for decision-making of the SIP at a given site. The proposed CBDA framework is applied to a database consisting of 152 usable test piles across various U.S. states, which enables the assessment of SIPs under diverse geological conditions. The results show that RL effectively optimises SIP selection with RF achieving the highest overall accuracy in predicting optimal SIP actions. The study contributes a novel data-driven approach to CBDA and SIP evaluation in geotechnical decision-making.

Thermal interference process between two energy piles in 2D model using transparent soil

Energy piles have the potential to contribute to the use of shallow geothermal energy. The heat exchange efficiency of energy piles in groups decreases compared with that of a single energy pile. Understanding the thermal interference mechanism between piles and its impact on the temperature response of the soil is crucial. In this study, the evolution processes of the temperature field of transparent soil around one and two energy piles in a 2D model were obtained by establishing the relationship between pixel intensity and soil temperature. This relationship was verified using a single energy pile test under heating conditions. Thermal images of transparent soil under different thermal loads (heating or cooling) were studied to investigate the phenomenon of thermal interference between two piles. The temperature superposition effect becomes more evident closer to the center of the two piles. Analyzing the temperature distribution in the soil and introducing a thermal interference coefficient revealed that the thermal accumulation effect between piles is more significant under lower thermal loads.

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.

Evaluating the Direct CPT-Based Design Methods for Estimating the End Bearing and Side Resistance of Instrumented Test Piles

Evaluating the Direct CPT-Based Design Methods for Estimating the End Bearing and Side Resistance of Instrumented Test Piles