Pile Load Tests Research Articles

Optimized systems of multi-layer perceptron predictive model for estimating pile-bearing capacity

The primary goal of this research is to leverage the advancements in machine learning techniques to forecast the bearing capacity of piles effectively. Accurately predicting load-bearing capability is an indispensable aspect in the field of substructure engineering. It is worth noting that determining load-bearing capability via in-place burden tests is a resource-intensive and labor-intensive process. This study presents a pragmatic soft computing methodology to tackle the aforementioned challenge, employing a multi-layer perceptron (MLP) for the estimation of load-bearing capacity. The dataset employed in this research encompasses a multitude of field-based pile load tests, with a meticulous selection of the most impactful factors influencing pile-bearing capacity as input variables. For a comprehensive comparative analysis, genetic algorithm-based optimizers (Crystal Structure Algorithm (CSA) and Fox Optimization (FOX)) were incorporated with MLP, leading to the development of hybrid models referred to as MLFO and MLSC, both structured with three layers. The performance of these models was rigorously evaluated using five key performance indices. The findings indicated a consistent superiority of MLFO over MLSC across all three layers. Remarkably, MLFO exhibited exceptional performance in the second layer (MLFO (2)), boasting an impressive R2 value of 0.992, an RMSE of 33.470, and a minimal SI value of 0.031. On the other hand, MLCS (1) registered the lowest accuracy in predicting the process with the least R2 value related to the validation phase of the model with 0.953. Taken together, these results affirm that the optimized MLP model stands as a valuable and practical tool for accurately estimating pile-bearing capacity in civil engineering applications.

Investigation on the bearing capacity evolution of building pile foundation during permafrost degradation

The warming and melting of permafrost due to climate warming pose a considerable threat to the integrity of the Pan Arctic building, thus jeopardizing sustainable development. The increase in ambient temperature in permafrost areas will cause deterioration in the bearing capacity of building pile foundations. Considering the continuous deepening of the active layer (za), the present paper used small-scale physical modeling to investigate the potential variation of bearing capacity and load transfer mechanism of pile foundations under the scenario of continuous degradation of permafrost. The ultimate bearing capacity of a single pile and the undrained shear strength of the ground under different za are estimated by cone penetration tests. In the static load test of single piles, the axial load-settlement, axial force of pile shaft, and earth pressure at the pile tip are measured. The results show that the rise in ground temperature and the deepening of the za shorten the elastic and elastic-plastic stages of the load-displacement curve, resulting in a gradual decline in the bearing capacity of a single pile. The pile-soil interface temperature is always higher than the adjacent ground temperature at the same depth. Adfreezing force of the pile-soil interface decreases due to the increase in ground temperature and water content. With the deepening of za, the peak point of the shaft resistance decreases from −30 cm to −60 cm under the ultimate state. Meanwhile, with more axial load transfer along the pile shaft to the pile tip, the share ratio of pile tip resistance to ultimate stress gradually increases. In addition, the temperature rise of frozen soil at the pile tip accelerates the settling rate of the pile, which eventually causes the pile foundation failure.

The Effectiveness of determining the Load-bearing Capacity of Piles based on the Results of Pile Dynamic Testing: The Case Study of Long An Province, Vietnam

Determining the load-bearing capacity of piles currently relies on various field experimental methods, with static pile compression loading testing and dynamic pile testing through Pile Driving Analysis (PDA) being widely accepted as reliable practices. However, the application of PDA tests faces limitations, especially in construction projects with weak soil profile while the static pile load test usually requires high testing costs. Consequently, the conventional dynamic pile testing method, checking the resistance through a number of dynamic hammer blows, is commonly utilized. Despite its prevalence, there has been limited research on the traditional dynamic pile testing method. In light of this, the present study aims to examine the traditional approach by analytical and numerical simulations. By doing so, it seeks to offer a more objective and comprehensive understanding of its effectiveness when compared to alternative methods.

Driven pile foundation reuse in East London, UK

Multiple phases of redevelopment of the London Docklands, UK, have resulted in the need to replace existing structures with new, often larger, structures. This paper presents the case history of a 1980s low-rise office building (three to four storeys) being replaced by a medium-rise (five storeys + roof terrace) recreational building structure. The 1980s building was founded on driven closed-ended steel tube piles located within one of London’s historic docks. Subsequent to the 1980s building construction, London Underground (LU) tunnels were constructed below the dock in the late 1990s in close proximity to the structure. Piling in the dock adjacent to the LU tunnels resulted in restrictions to pile construction methodology. The new structure reused the driven piles in the dock and added new onshore bored piles to accommodate a larger building footprint landwards. The pile reuse justification used the original preliminary pile load test and driving records along with current design codes. The 1980s allowable working loads stated on the design drawing were lower than that required to support the new building, thereby requiring reinterpretation of preliminary pile load test results. The pile reuse assessment justified an increase in pile working load from 1050 to 1760 kN.

The Vertical Behaviors of Dissimilar Pile Composite Foundations over Inclined Bedrock

Pile composite foundations (PCFs) have been commonly applied in reinforcement engineering to adjust the vertical stiffness of foundations, due to the displacement control design criteria for foundations. PCFs that have dissimilar pile lengths, located over inclined bedrock, have shown significantly different vertical behaviors from PCFs with equal pile lengths, placed over a semi-infinite medium. However, the vertical behaviors of dissimilar PCFs over inclined bedrock cannot be predicted with the current theoretical methods, although they have been widely adopted in engineering. An analytical method is proposed in this investigation to analyze the vertical bearing characteristics of dissimilar PCFs over inclined bedrock. A pile–soil system is decomposed into fictitious piles and extended soil, and then a control equation to determine the axial force along the fictitious piles is established, stemming from the compatibility conditions between them. The vertical behaviors of dissimilar PCFs can be obtained by solving the control equation with iterative procedures, and the equation is verified by two field load tests of single piles from the Honghe bridge and a numerical case. Then, the settlement and load transfer behaviors of 3 × 1 dissimilar PCFs and their influence factors are analyzed, and the results are as follows. (1) Obvious differences can be observed concerning the axial force distribution, settlement w, and load-sharing ratio (LSR) of each pile element for different pile–soil stiffness ratios (Ep/Es). (2) The LSR of pile 1 increases from 0.074 to 0.253 for the rigid pile and from 0.062 to 0.161 for the flexible pile condition when the cushion stiffness Kc changes from 1 × 104 kN/m to 3 × 108 kN/m. The non-dimensional vertical stiffness of the foundation, N0/wdEs, increases from 10.21 to 28.95 for the rigid pile condition and increases from 8.69 to 14.44 for the flexible pile condition, when Kc increases from 1 × 104 kN/m to 4 × 105 kN/m. (3) The neutral layer depth of the pile zn, the average settlement w, and the differential settlement wd of each element head decrease with Kc, and no negative friction zone exists (zn = 0 m) for all the pile elements when Kc> 2 × 105 kN/m. (4) The N0/wdEs decreases with the distance between the pile bottom and the inclined bedrock Δ. For the rigid and flexible pile conditions, the N0/wdEs is 22.16 and 13.48 for Δ = 1 m, and 13.13 and 10.10 for Δ = 8 m. The wd reaches 16.7 mm and 4.0 mm for Δ = 1 m and Δ = 8 m, respectively. (5) The N0/wdEs increases almost linearly with an increase in l/d for the rigid pile condition, and it gradually decreases for the flexible pile condition. The developed model can improve the design and analysis of PCFs located over inclined bedrock under vertical loading.

Static Load Testing of Instrumented Screw Piles in Soft Soil Deposits

With the rapid development across major cities, low-capacity screw piles are adopted by builders as a viable economical option in managing risk involving settlement in soft soil deposits. Although the required installation torque and the capacity of a screw pile can be correlated to the soil shearing resistance at the interface of its shaft and helical plates, the correlated ultimate capacity of the pile is specific only to undrained conditions. Therefore, if the water table fluctuates within the embedment length of the pile, the correlated ultimate strength is not valid. This poses a serious design concern in over-consolidated fills. Therefore, due to the uncertainty associated with the compressive capacity of installed screw piles in soft saturated deposits, it is advantageous to perform a static load test to verify the serviceability and ultimate loads. In this study, four static load tests were carried out on screw piles at four different construction sites in the city of Melbourne, to study the load transfer mechanism at various levels of axial loading and subsequent unloading/reloading stages. In one of the sites, the screw pile was equipped with miniature transducers to monitor the generated total stress and pore-water pressure during the installation and post-installation. The results of this study indicated that a static load test can accurately estimate the real bearing capacity of a screw pile which differs significantly from the design geotechnical strength calculated using theoretical equations. It was concluded that in the absence of a pile load test, it is rational to adopt a geotechnical reduction factor of 0.4 and neglect the skin friction capacity of the screw pile to provide a safe foundation design.

Load-Settlement Analysis of Axially Loaded Piles in Unsaturated Soils

Unsaturated soil covers a significant part of the world, and studying the behavior of deep foundations in this medium is an important step in increasing accuracy and economic efficiency in geotechnical studies. This paper presents an analytical solution to investigate the load-carrying characteristics of single piles embedded in unsaturated soils, accounting for the effect of groundwater level on the pile’s response. For this purpose, relationships for shear modulus and Poisson’s ratio for unsaturated soils were collected from the literature to consider their effects as key parameters on pile performance. A parametric study was conducted to evaluate the effect of soil moisture content on the behavior of the pile-soil system for different soil types, and the effect of pile slenderness on its load-settlement behavior was studied for varying soil moisture contents. The results indicate that the pile stiffness increases as the soil suction increases while below a critical slenderness value, hence increasing the pile load capacity. However, this improvement occurs within a limited range of soil suction that is narrower for coarse-grained soils. The pile settlement corresponding to soil failure was also evaluated by modifying the existing solutions for unsaturated soils. The developed solutions were verified against the predictions of published solutions as well as the results of finite element analysis and pile load tests. It was found that the system stiffness decreases by 50% when the water table rises from the pile toe level to the ground surface in the studied soil.

Predicting Load-Settlement Behaviour of Large Diameter Piles using Runge-Kutta numerical Method.

A numerical solution for predicting the axial load and corresponding settlement of large diameter piles is proposed based on the hyperbolic curve load transfer function in this paper. It is important to note that the most reliable approach to determine the axial load capacity of a pile is to use the P-S curve, which is usually obtained through an on-site load test. Performing a pile load test on a large diameter pile (pile diameters over 3m), requires a thousand tons of test load, which sometimes is unachievable. The load-settlement relationship or P-S curve of this type of pile can be determined by the Runge-Kutta numerical method for practical application especially for offshore piles. Comparison is made between the results obtained by this proposed numerical, the test data, analytical solution and pile load test data, and close agreement has been found thus verifying the accuracy of the proposed method. However, the rigid body displacement of the piles did not show any significant effect on the proposed numerical when compared to the analytical and onsite pile load test results. It is expected that the proposed numerical method can be used to predict the load and corresponding settlement of large diameter piles.

Effect of soil-pile contact parameters on pile bearing capacity value

The soil and foundation elements are fundamental to the behavior of a structure. When the foundation soil has a low capacity, it is necessary to transmit the loads to a deeper and more resistant layer, using deep foundations. A pile load test is a field measurement of the bearing capacity (vertical or horizontal) of a foundation element. In addition to a physical model of a load test, the use of computational tools can bring additional understanding. In order to analyze the responses obtained by numerical models compared to field test results, tools that use Finite Element Methods (FEM) and that have a series of constitutive models become a great alternative. This paper aims to study the behavior of Continuous Flight Auger (CFA) piles, aiming to understand the soil-pile interaction regarding the effect of soil-pile contact parameters on pile bearing capacity value. In this way, experimental data from three load tests were compared with numerical simulations using the Mohr-Coulomb constitutive model. Also, a parametric study was completed based on the collected soil data from the literature of the region that most affected the settlement behavior of the load pile. It was concluded that there is a direct and significant influence of the friction coefficient on the pile bearing capacity. In addition, by incorporating more real soil data and parameters representing its actual formation, the results of the pile load test simulation can be taken as an alternative to estimate the ultimate capacity of a vertically loaded pile in the absence of the static load test, which has been widely observed in engineering practice.

Results of a Simple Pile Loading Test Using Human Power and Numerical Simulation of the Results

Results of a Simple Pile Loading Test Using Human Power and Numerical Simulation of the Results

The Application of Soft Foundation Treatment of Cement-soil Mixing Pile in Zhangzhuang Pumping Station

The text introduces the process of comparison and selection of foundation treatment scheme, combining with example of foundation treatment in Zhangzhuang pumping station, and elaborates the detailed design steps and calculation way of cement-soil mixing pile,the economy benefits is very significant through settlement check, composite static load test, static load test of single pile, the bearing capacity of composite foundation meets the design demand.

Evaluation of ultimate load - bearing capacity of piles based on static compression test and pile dynamic analysis (PDA)

Determining the load bearing capacity of piles from field tests is a reliable method that allows for the verification of load carrying capacity according to theoretical calculations, thereby the ultimate load-bearing capacity of the piles can be evaluated, serving as the basis for selecting the design load-bearing capacity that is suitable for the site conditions. Among the various pile load testing methods, static compression testing is a traditional method known for its high reliability and early adoption. However, when piles are constructed at significant depths or large diameter drilled piles have higher load bearing capacities, static compression testing encounters difficulties due to the large experimental load and extends testing times. In contrast, the pile dynamic analysis method (PDA) introduced by the Case Institute of Technology in the United States in the 1960s determines the load bearing capacity of piles based on stress wave propagation theory in elastic bars. It offers several advantages, including shorter testing times and no need for static loading, making it suitable for challenging terrain conditions. Nowadays, this method is widely used and integrated into the design guidelines and testing standards of many countries. In this article, base on the results of axial static compression tests and PDA method on reinforced concrete piles and drilled piles at several real project to compare and evaluate the load bearing values of the piles and assess the reliability of the testing methods.

PREDICTING GEOTECHNICAL AXIAL CAPACITY OF REINFORCED CONCRETE DRIVEN PILE USING MACHINE LEARNING TECHNIQUE

Modified Meyerhof method is a popular method to calculate pile geotechnical axial capacity in Malaysia currently. From past experience, pile design based on empirical and analytical method produce variability of predicted capacity, in which, there is a wide scatter of predicted capacities and tendency for the predictions to be conservative, i.e. to underestimate the load capacity. This study provides options of machine learning and statistical approach for prediction of pile capacity based on soil investigation and dynamic pile load test result. It serves as an additional checking for engineer during design of pile based on conventional empirical method. It also helps to provide deeper insights of non-linear variables related to pile capacity through machine learning and statistical approach. This study helps engineer to design pile foundation optimally, economically and safely. The prediction of pile geotechnical axial capacity with machine learning technique and statistical approach for local marine clay soil in Penang, Malaysia is proposed in this study. The information from soil investigation report and dynamic pile load test report are gathered from six projects at Batu Kawan and Nibong Tebal located in Penang state that contributed 439 numbers of data. The skin friction factor, end bearing factor and pile geotechnical axial capacity are computed and predicted using empirical method, machine learning model and statistical model. Support Vector Machine illustrate best fit model for predicting skin friction factor with R2 of 0.517 while Random Forest seems to be the best fit model for predicting end bearing factor with R2 of 0.264. Random Forest is found to be the best model in predicting the geotechnical pile axial capacity compare to other models as it explains 96.2% of the variability of pile capacity.

Interpretation of bi-directional pile load Tests using instrumented gauge data

ABSTRACT This study presents a method that is conventionally used for interpretation of a head-down pile load test, which is modified and extended for a bi-directional pile load test. A parabolic function is used to simulate the load transfer curve along a depth above or below the load cell. The coefficients of the function are obtained by fitting the measured gauge data. Three bored piles are tested using a bi-directional load cell that is installed in the middle of the pile shaft and the results are interpreted using the method of this study. An equivalent head-down load-displacement curve that is obtained using the presented method produces results that are in good agreement with those that are obtained using the conventional method. The relationship between mobilized unit skin friction and displacement that is obtained using the measurement data and using the presented method shows similar trend.

Application of lateral displacement measurement in pile lateral load test

Usual pile lateral load test does not supply advance results. This paper presents pile lateral load test using suitable instrument to measure lateral movement of pile shaft. The new method of pile test supplies the behavior of pile under lateral load such as pile deformation, pile inner forces, soil pressure… and help to validate the design calculations as well as to choose the reasonable pile-soil calculation method.

Resistance responses and design recommendations for driven piles in coarse-grained soil-based intermediate geomaterials

Piles driven in Intermediate GeoMaterials (IGM) pose multiple design and construction challenges because of the high uncertainty in IGM properties, lacking knowledge pertaining to pile responses in IGM, and absence of classification, static analysis (SA) methods, and design recommendations. A classification criterion is established for coarse grained soil based intermediate geomaterials (CG-IGM) using test pile data from bridge projects completed in four U.S. states. This study improves our understanding of pile resistance responses in CG-IGM and results in pile design recommendations. Unit shaft resistance (qs) of CG-IGM increases with the ratio of effective vertical stress (σv′) to the ratio of corrected N-value, (N1)60. Unit end bearing (qb) increases with the ratio of. corrected N-value, (N1)60 to the effective vertical stress (σv′). New SA methods are developed for predicting qs and qb. The proposed SA methods are compared against existing β-method developed for coarse grained soil and validated using an independent pile load test dataset. Pile setup is observed in qs of piles driven in CG-IGMs, and pile relaxation is mostly observed in qb. Statistical assessment concludes that the proposed SA methods provide more accurate and consistent qs and qb predictions than that by the β-method.

A practical framework for assessing the effect of cyclic softening of clays on the lateral response of single piles

Single pile foundation has been widely used for the most offshore wind turbines to resist the cyclic loading resulted from the wind and wave. The cyclic loading can result in the degradation of the shear strength and the stiffness of clays surrounding piles. This study proposed a practical framework for assessing the effect of cyclic softening of clays on the lateral response of piles. A 3D finite difference model was developed for the pile – soil interaction under cyclic loading and then verified by full-scale monotonic and cyclic lateral load tests conducted on the single pile in clay. The cyclic softening behavior of undrained clays was described by a nonlinear dynamic softening constitutive model developed by the authors. The effect of the loading type (i.e., one-way and two-way loading) and the loading amplitude on the cyclic lateral response of piles was investigated. Moreover, a prediction function was proposed and was demonstrated to be effective in estimating the evolution of cumulative peak lateral displacement of cyclically loaded single piles in clays. The proposed practical framework provides an alternative for predicting the cyclic response of single piles in clays based on the monotonic lateral load test of piles.

Pile Capacity Checking Tool based on Distributed Fibre Optic Sensing for Instrumented Pile Load Test

Pile load test instrumented using Distributed Optical Fibre Sensing (DOFS) offers a superior ability to assess pile capacity through continuous strain profiles as opposed to the discrete measurement method such as Vibrating Wire Strain gauges. Due to the vast amount of spatial data generated by the sensor, processing the raw data from DOFS is not always straightforward, often done manually with careful interpretation of various factors affecting the measurements. Experts are reconciling with different data processing algorithms to assess pile capacity (t-z curve) from the DOFS data and verify it, leading to a demand for standard practice. Currently, the verification is done by comparing the pile capacity assessed from DOFS data to the analysis from the commercially available numerical software. The software typically requires input parameters such as extensive soil data, structure geometry, and loading intensity. Some of these parameters are limited (due to bureaucracy or trade secrecy) for the pile load test contractor to verify the pile capacity computation. This paper presents a checking tool that has been developed to automate the processes including raw file parsing, initial processes (trimming, positioning, and averaging), and post processes (pile capacity computation and checking). The post processes utilised the simplified Finite Element Method (FEM) to perform the checking which only utilised the DOFS data. In this paper, an application of the developed tool to a DOFS instrumented pile load test in Kuala Lumpur is reported. This exercise provides the information that the tool can be helpful to verify the pile capacity computation from DOFS data with promising performance reliability at 95%.

Deriving a p-y curve from lateral pile load tests – Case studies in alluvial OC clays

Estimating lateral pile capacity is one of the most typical works for geotechnical engineers. Although it has been a routine calculation, obtaining reliable results is still challenging, especially when the ground condition is unfamiliar. Fortunately, the lateral pile capacity prediction can be performed by deriving a p-y curve from the load-deformation curve measured during pile testing. In cases where a preliminary test pile exists, fortunately, the p-y curve can be generated easily using a subgrade reaction approach suggested by Davisson and Gill (1963). Two lateral pile load test results were used to show the prospect of this method for practical applications. The field tests were on driven and bored piles with different diameters and lengths embedded in alluvial OC clays at two different sites in Jakarta, Indonesia, where both piles were categorised as long piles. Derivation of p-y curves was performed with a simple spreadsheet. Then, the obtained p-y response was used to estimate the load-deformation curve. Results showed that the back-calculated curve agree well with the measured data. This outcome might be because the p-y curves were directly derived from the field test where the pile experienced in-situ stress, resulting in a more representative of the actual condition.

Estimation Criteria for Static Rock Mass Deformability Modulus for Rock-Socket Design in Metamorphic Rock Masses

This study investigates the most appropriate empirical criteria to estimate the static rock mass deformability modulus (𝐸𝑚) in the design of rock-sockets in cast-in-situ bored pile construction. The in-situ 𝐸𝑚 values are initially estimated through back analysis of static pile load test data. Secondly, the rock mass deformability estimated from back analysis (𝐸𝑚b) are tested statistically against selected established empirical equations to determine whether the latter are appropriate for use in metamorphic rock terrain of Sri Lanka. It is found that the existing empirical criterion based on the square root of intact unconfined compressive strength (𝜎𝑐) derived from back analysis of pile load test results is appropriate for weak-poor rock masses. For strong-poor rocks, it is recommended to employ the equation based on 𝜎𝑐', and in general the two equations generate lower and upper bound solutions. The equation based on intact deformability modulus (𝐸𝑖) performs well in strong-excellent quality rock masses, while the equations based on 𝐸𝑖 and rock quality designation (𝑅QD) are found to be appropriate for weak-fair to excellent rock masses. Finally, a new set of equations appropriate for different rock mass types have been proposed through regression analysis along with appropriate design measures to be adopted.