Pile Load Tests Research Articles

Managing piling obstruction risk intelligently for reinvention of a UK brutalist building

Northwood Investors are reinventing a 1980s Brutalist-style London, UK, office building, ‘The Acre’, is located in a densely populated urban environment and surrounded by residential properties. There is a plethora of known and unknown obstructions beneath the site, including heavy steel grillages. Typically, such sites are redeveloped by total demolition and lengthy enabling works with significant vibration and noise. Instead, Northwood decided to replace selectively just 20% of the existing structure while upgrading and re-cladding the remaining 80% to create a modern development, with half the embodied carbon dioxide of the previously consented scheme. To make the scheme viable, Arup proposed the use of Pali Radice piles. This technique can construct mini-piles through layers of obstructions that would defeat traditional piling rigs and can operate in constrained spaces such as existing basements. Despite the choice of piling technique limiting the pile diameter and tender options, this offered a step change in risk control and was crucial to enabling the project. Drilling trials and preliminary pile load testing were undertaken. The trials proved the effectiveness of the technique and informed the pile design. Evidence from the trials permitted the method and programme to be assessed and installation risks to be managed appropriately.

Evaluation of ASTM D 1143/D 1143M-07 and Chinese Code JGJ 106-2014 for Pile Load Testing using Finite Element Method

Pile foundation is a structural element utilized to transmit structural load into the soil mass. During design processes, many empirical equations used to estimate axial pile capacity, and a pile load test is conducted to validate the design. In Indonesia, it is common to adopt ASTM D 1143/D 1143M-07 for pile testing. Chinese Code JGJ 106-2014 is another viable option, which has gained popularity recently. This study investigated the load–settlement curves obtained using both codes. The analyses were simulated using the Mohr–Coulomb and the Hardening Soil models. The Hardening Soil model yielded more reasonable load–settlement and load–excess pore water pressure curves than the Mohr–Coulomb model. The reason due to the Mohr–Coulomb model unable to capture the non-linear behavior of soil properly. Furthermore, the results showed that ASTM D 1143/D 1143M-07 and JGJ 106-2014 yielded comparable results. Hence, both methods could be substituted each other.

The Analysis of Pile Skin and Base Resistances Interaction Based on Static Pile Load Test in Experimental Research

Abstract Static pile load tests in laboratory conditions were carried out to study the mechanism of the pile skin and pile base resistance mobilization with settlement and their interactions. The mechanism of the skin resistance at the base is important in the correct interpretation of the pile capacity. Especially in the case of piles shallowly embedded in the bearing layer. In the studies described in this article, high-precision piezoelectric elastic stress maps were used. The tests were carried out on piles with a diameter of 2.5–2.8 cm, and length of 40 cm. Static pile load tests were carried out to measure resistance at the pile base, settlement and change of stress in the soil at the level of the pile base or beneath the pile base were measured. The analysis of stress in soil allowed to investigate the interaction between the resistances of the pile base and skin. The state of stress in the soil close to the pile base, both beneath and above the pile base level was heavily influenced by the simultaneous mobilization of skin and base resistance.

Capacity prediction and design optimization for laterally loaded monopiles in sandy soil using hybrid neural network and sequential quadratic programming

Data driven methods have gained momentum in recent years in solving highly non-linear engineering problems that are challenging to solve using conventional methods. In this paper, we present a hybrid neural network model to predict the lateral response of large-diameter monopiles in multi-layered soil. The hybrid neural network consists of a mixture of convolutional and fully-connected layers, which capture the impacts of the soil profile, the pile geometry, and loading conditions on the lateral load response of monopiles. To train the neural network model, we produced data from high-fidelity three-dimensional (3D) finite element (FE) models that are validated against full-scale pile load tests. To ensure consistent model performance across the entire range of pile capacities considered in the dataset (ranging from approximately 100 kN to 100,000 kN), we utilize the relative error (percentage error) as the criterion for training the model. To achieve this goal, we explored six different combinations of data transformation methods (i.e., natural logarithm and root transformations) and cost functions. Among these models, the model trained with Mean Squared Error (MSE) using natural logarithm transformation yielded the most accurate and consistent predictions of the lateral capacities of monopiles. To demonstrate the strengths of the developed neural network model, it was used as a surrogate model to perform pile design optimization using sequential quadratic programming. In addition, a design example is provided to show how the developed method can be easily implemented.

An Experimental Study on Estimation of the Lateral Earth Pressure Coefficient (K) from Shaft Friction Resistance of Model Piles under Axial Load

Estimating a pile shaft’s frictional capacity is challenging and has been a controversial subject among researchers. In this study, the shaft friction resistance of non-displacement (pre-installed) model piles under axial load was investigated. Four different model piles were used, including steel, timber, and two composite piles (FRP and PVC filled with concrete). The angle of interface friction (δ) between test sand, and pile materials was determined using an interface shear test (IST) at four relative densities. Axial pile load experiments were implemented in a soil tank and piles were embedded into loose to very dense sand. Model pile load tests were performed in such a way that there was no end (point) bearing capacity (only friction was generated), and lateral friction resistance between the pile material and the soil along the pile shaft formed the complete bearing capacity of the model pile. According to experimental results, it was observed that, with increasing sand relative density and surface roughness of the pile material, the shaft friction resistance of the model pile increases. A back-calculation analysis was also performed to find the values of lateral earth pressure coefficient (K) using Burland’s (1973) equation with the help of measured shaft friction capacity of the model pile load test. By performing multivariate regression analysis, an equation was obtained between the back-calculated lateral earth pressure coefficient (K) and other parameters. The obtained equation was used to calculate the K values given in other studies in the literature. It was determined that the obtained equation was in good agreement with the data in other studies. This equation can be beneficial in practice and can be advantageous for further study in the future.

A Novel Approach Proposal for Estimation of Ultimate Pile Bearing Capacity Based on Pile Loading Test Data

Determining the ultimate bearing capacity of piled foundations has been one of the most important problems in geotechnical engineering. It has been observed that the pile loading test evaluation methods based on the mathematical model give values far away from the failure load, even in piles that have reached the failure state. For this reason, it is aimed at developing a new mathematical pile loading test evaluation method based on the load-settlement curve. It has been thought that the main problem with the pile loading test evaluation methods based on other mathematical models giving values far from the failure load is that the methods iterate excessively. The new method proposed in the study was developed by taking this situation into account. The performance of the proposed new method was investigated using eight pile loading tests conducted in various provinces of Turkey. In order to verify the reliability of the newly developed method, the study was completed by applying multiple comparison tests with other methods in the literature (theoretical methods, finite element analysis methods, and pile loading test evaluation methods). According to the applied analysis of variance, it was concluded that the proposed new method remained within the 95% confidence interval and was usable.

A Novel Method to Predict Shaft and Base Responses of a Pile from Cyclic Pile Load Test Results

A Novel Method to Predict Shaft and Base Responses of a Pile from Cyclic Pile Load Test Results

Prediction of the End-Bearing Capacity of Axially Loaded Piles in Saturated and Unsaturated Soils Based on the Stress Characteristics Method

This study proposed an analytical approach for predicting the end-bearing capacity of driven piles that are subjected to axial loads in saturated and unsaturated soils. This is a generalized approach in which the stress characteristic method is employed successfully for both saturated and unsaturated soils. An iterative technique computer code was developed for the proposed analytical approach extending the finite difference method to develop solutions with the aid of MATLAB (version 2019a) that provides graphical output to visualize the results. The results from the proposed approach were compared against measurements for 13 pile load tests that include 11 in saturated soils and 2 in unsaturated soils, with good agreement. In addition, numerical analyses were performed using ABAQUS (version 6.14) to simulate the driven pile penetration and pile loading by employing the arbitrary Lagrangian–Eulerian adaptive mesh methods. The comparisons between the numerical predictions and measurements from a published model pile test suggested that the ultimate bearing capacity is well predicted by the finite-element model in comparison to the proposed analytical method. However, the proposed analytical method was simple for use in engineering practice applications to estimate the end-bearing capacity of pile foundations in both saturated and unsaturated soils.

Numerical Modelling of Displacement Pile Resistance in Sand Ground. Part 2: Discrete Model, at Rest Stage, Load Test

The article presents a continuation of research results on numerical modelling of displacement pile prototype ground (sand) resistance. Numerical modelling of ground resistance consists of three stages: restitution of initial soil stress state, the restoration of stress state developed during pile installation and the modelling of pile resistance against applied load (pile load test). Restitution of initial ground state induced in artificially created sand deposit after compaction procedures was realized by creating stress history and defining experimentally determined over consolidation stresses. Installation effects were restored using a well-known empirical approach based on relation between CPT test data and radial stress increase. Hardening soil model and its parameters were employed for modelling pile test substantiated in the first paper (Part 1) of the research. The discrete model of pile, soil layers, and pile-soil contact was created. Modelling of pile loading-unloading resistance was applied using an incremental loading procedure. Numerical analysis results validated with displacement pile prototype testing results.

The 2022 Pacheco Silva lecture: The influence of residual loads on pile foundation behavior

Residual loads can affect the load transfer and the settlement-induced in-service loadings, although they do not alter the bearing capacity. When residual loads are present and not measured or evaluated, the settlement estimate is greater than predicted if these loads are known. Residual loads can be measured when the pile instrumentation is nullified before pile installation, in the case of displacement piles, or before the first loading in non-displacement piles, such as bored cast-in-place piles, continuous flight auger piles, and micro-piles. In the case of underpinning foundation and piled raft, when the loading transfer is shared by the original and new foundation, or by the piles and the raft, it is essential to know the stiffness of each foundation element to estimate the load partition. If residual loads are present, pile stiffness is greater than when not considered in the design. The paper revisits this theme of practical relevance. A historical review of the most relevant research involving pile residual load measurements, pile loading tests including the interpretation of residual loads locked at a pile toe, and a new procedure for residual loads prediction are provided. A comparison is made of the experimental residual loads observed in some of the instrumented cases and the values estimated with the suggested procedure. The development of residual loads at the pile toe as a function of the toe resistance to total capacity ratio is very similar to the variation of the soil density as a function of soil moisture content in soil compaction.

Mechanical and numerical behavior of water jet-driven under-reamed concrete piles

Water jet-driving technique has been shown as a viable practice for driving prefabricated piles in resistant soil layers. However, this technique is also associated with the reduction of load capacity of piles. Along these lines, the use of reams in prefabricated concrete piles improves their mechanical performance. The main objective of this research was to study the efficiency of reams on water jet-driven concrete piles; to this extent, pile loading tests and mini-cone tests were carried out before and after the driving of the piles. In addition, numerical modelling with the finite element method (FEM) was applied to study the stress-strain behavior. By means of the numerical modelling, it was possible to identify the stress and strain distribution at the tip, shaft, and reams of the piles; this allowed the understanding of the contribution of these elements in the total load capacity. Results have shown that the reams directly contribute for load capacity, with increases up to 40% when compared to conventional piles. Laboratory tests and numerical modeling proved to be fundamental tools to understand the mechanisms behind the contribution of reams to the load capacity of piles.

Exploring Tree-Based Machine Learning Models to Estimate the Ultimate Pile Capacity From Cone Penetration Test Data

Several approaches have been developed to estimate the ultimate capacity of piles, such as static and dynamic load tests, static analysis from soil borings, and directly utilizing in-situ test results. Recently, there has been increased interest in using in-situ cone penetration test (CPT) to estimate pile capacity. Several analytical pile-CPT methods have been developed, which involve several correlation assumptions that can affect their accuracy. In this paper, three tree-based machine learning (ML) models, namely decision tree (DT), random forest (RF), and gradient boosted tree (GBT), are developed for estimating the ultimate capacity of piles from CPT data. A database that contains 80 pile load tests and associated CPT data collected in Louisiana was used to develop these ML models. The measured ultimate pile capacity (Qm) was determined using Davisson’s interpretation method from the load–settlement curve of each pile load test. Among the developed ML models, GBT demonstrated the most accurate ML model compared with the others. The estimation of ultimate pile capacity from the GBT model is compared with those obtained from the four best-performing direct pile-CPT methods (based on a previous study): the University of Florida (UF), probabilistic, European Regional Technical Committee 3 (ERTC3), and Laboratoire Central des Ponts et Chaussées (LCPC) methods. The GBT and pile-CPT methods were evaluated and ranked based on analysis of multiple statistical criteria. The results clearly showed that the GBT model outperforms the four direct pile-CPT methods for estimating the ultimate capacity of piles.

Correlation between Pile Displacement from Pile Load Tests and FE Modelling: Case Study of Piles in Cawthorne Channel Area in Nigeria: Case Study of Piles in Cawthorne Channel Area in Nigeria

Correlation between Pile Displacement from Pile Load Tests and FE Modelling: Case Study of Piles in Cawthorne Channel Area in Nigeria: Case Study of Piles in Cawthorne Channel Area in Nigeria

Cast‐in‐place deep foundations in Myanmar

AbstractThis article is a summary of the available research works of cast‐in‐place deep‐seated bored piles in Myanmar. Instrumented static pile load test results are analyzed, discussed, and updated. The information contained in the article is mainly from the construction projects of private sectors constructed in Yangon and extended study of previous work on current practices of deep foundations and deep excavation Works in Myanmar.

Evaluation of Bearing Capacity for Cast In-Situ Bored Piles

Abstract: Pile is a structural element constructed to overcome heavy loads from super structure, when proper bearing strata is not available at shallow depth. The prediction of bearing capacity of a bored cast in-situ pile is a complex problem, as it depends on installation method, concrete quality, ground condition and pile geometry. It is considered that the reliable method for finding bearing capacity is pile load test, which is time consuming and costly. The bearing capacity can also be analysed by empirical and analytical methods using soil data and SPT data. In this paper, empirical methods and graphical methods are used to evaluate beating capacity of cast in-situ bored piles. For empirical methods - IS code method, Meyerhof method, Bazaraa and Kurkur method are employed and for graphical methods - Hansen’s method, Chin-Kondner’s method, Decourt’s Extrapolation method are employed. All these methods are summarized for comparison with the pile load test values. A database of 3 bored piles is collected from different sites in Kerala. The above chosen SPT methods are calibrated by trial and error method to propose a new formula. A pile structural design also proposed.

Data-driven modeling of ultimate load capacity of closed- and open-ended piles using machine learning

ABSTRACT Field pile load tests are fairly expensive experiments that can be applied to certain pile types required to be installed in full scale. Hence, it is neither practical nor efficient to perform a load test for every installed pile. While there exist many empirical relations for predicting pile capacities, such methods typically suffer from accuracy and generality. Therefore, current geotechnical practice still looks for methods to accommodate full-scale pile load testing to serve as accurate and practical tools. In this study, load bearing capacities of closed- and open-ended piles in cohesive and cohesionless soils are predicted using machine learning. Nine such methods are utilized in the analyses where Cone Penetration Test (CPT) and pile data are considered as the learning features necessary to teach those methods the database gathered via a comprehensive search. Then, machine learning models are developed, and the databases are separated into five-folds according to the cross-validation-principle, which are used for both training and testing of the machine learning methods. Model predictions are validated with classical CPT-based equations. Results indicate that Relevance Vector Regression and the Random Forest methods typically generate considerably better predictions than the other methods and empirical equations. Thus, machine learning methods are found as reliable tools to predict the pile load capacities of both open-ended and closed-ended pile provided that there is a large enough database and that an appropriate method is used.

Helical piles with cement injection in medium dense sand

ABSTRACT Helical piles are frequently used as foundations of transmission line towers and other structures subjected to both compressive and tensile loads. However, the service performance of these structures can be affected by the uplift response of this type of pile due to the soil disturbance caused by the installation procedure. Two different procedures of cement injection were successfully used to repair this soil disturbance and improve the uplift response of helical piles in soils with some cohesion in a previous study, however these techniques have not been evaluated in cohesionless soils. Therefore, the current study examined the use of two cement injection procedures to improve the tensile and compressive responses of helical piles in medium dense fine sand. For this evaluation, pile loading tests were performed on six identical three-helix piles. The results show that the improvement caused by the cement injection is more significant for the pile uplift performance, although it slightly improves the pile compressive behaviour. The gain in allowable tensile load varied from 40% to 57% according to the injection technique. These preliminary results also indicate that the use of cement injection can provide similar load–displacement response for helical piles under tension and compression.

Long-term axial performance of continuous-flight pile in frozen soil

A number of buildings in the Canadian Arctic communities have failed or showed signs of failure of pile foundations caused by climate-change-induced excessive settlements. Effects of climate change warrant alternative pile types and new installation methods. Installing a pile into frozen soils by the torque method is rare in current practice of the Canadian Arctic. The continuous-flight pile is a new foundation type that is installed by torque. This study is aimed at investigating the axial load transfer of continuous-flight piles in frozen soils under long-term loads. A primary objective is to examine the effects of soil temperature, water content, and soil salinity on the resistance and the failure mode of continuous-flight piles in frozen soils. A series of axial load tests of model continuous-flight piles with a shaft diameter of 89 mm were carried out in the lab. Results show that primary and secondary creeps were observed during the constant load tests. The cylindrical shear mode and individual bearing mode were observed and inferred from the measured data. The adfreeze shear resistance and the individual plate bearing resistance under constant loads were estimated and verified using data from the literature. The adfreeze resistance increased with the applied load, and the plate bearing resistance increased as the normalized pile displacement rate increased. The mobilized adfreeze and plate bearing resistances suggest a potential increased load capacity of the continuous-flight pile compared to conventional smooth piles of similar diameter.

Evaluation of flexural behavior of steel pile connected with clamp-type mechanical connector

Typically, multi-segment steel piles that support loads are connected with mechanical connections or via the welding of segmented sections to ensure support capacity. Because steel piles are often used in the foundations of structures for which the flexural resistance performance requirements are relatively higher than those of pretensioned spun high strength concrete piles, the flexural resistant behavior and capacities of mechanically connected steel piles must be examined. In this study, to confirm the horizontal flexural resistance behavior of the steel piles connected via mechanical connections, a flexural load test of a steel pile connected with the clamp-type connectors was performed, and the flexural resistance behavior and failure characteristics generated in the flexural load state were evaluated. In addition, the mechanical pile connection and steel pile were modeled by finite element (FE) analysis, and the experimental and structural analysis results were compared. The variation in the flexural resistance performance with the changes in the material properties of the steel pile and mechanical connection was analyzed based on the FE analysis results. Taking into account the change in the material properties of the steel pile and clamp-type connectors, it was found that the maximum load and displacement increased with increasing yield and tensile strengths of the clamp-type connector.

Systematic literature review and mapping of the prediction of pile capacities

Predicting the pile’s load capacity is one of the first steps of foundation engineering design. In geotechnical engineering, there are different ways of predicting soil resistance, which is one of the main parameters. The pile load test is the most accurate method to predict bearing capacity in foundations, as it is the most accurate due to the nature of the experiment. On the other hand, it is an expensive test, and time-consuming. Over the years, semi-empirical methods have played an important role in this matter. Initially, many proposed methods were based on linear regressions. Those are still mainly used, but recently the use of a new method has gained popularity in Geotechnics: Artificial Neural Network. Over the past few decades, Machine Learning has proven to be a very promising technique in the field, due to the complexity and variability of material and properties of soils. Considering that, this work has reviewed and mapped the literature of the main papers published in journals over the last decades. The aim of this paper was to determine the main methods used and lacks that can be fulfilled in future research. Among the results, the bibliometric and protocol aiming questions such as types of piles, tests, statistic methods, and characteristics inherent to the data, indicated a lack of works in helical piles and instrumented pile load tests results, dividing point and shaft resistance.