Ultimate Pile Capacity Research Articles

Assessment of ultimate bearing capacity of the pile for jacking & rotary piling method

Techniques of pile installation such as jacking, dropping weight, vibration, and explosion were applied but these methods were discovered to have weaknesses, such as high friction resistance and high settlements. To overcome these problems, this study introduces new method of pile installation which is Jacking and Rotary method (J&R). The objective of this study is to determine pile behaviour for static load test using common method namely jacking (J), and a new method, J&R through the ultimate pile capacity achieved by both methods. A stainless steel 25 mm circular pile, a 50 mm circular pile and a screw pile were used as test piles for this investigation. To achieve the objectives, this study employed graphical methods such as Brinch Hansen 80% and Tangent method to determine the ultimate pile capacity for both piling installation methods. Results revealed that for jacking method, the highest ultimate pile capacity value for the 50 mm circular pile was 1.186 kN, whereas the 25 mm circular pile had the lowest pile capacity reading of 0.539 kN. Screw pile shows the reading of 1.068 kN for its pile capacity. While for J&R, the highest average for both graphical methods are screw pile with 0.683 kN, while the 50 mm circular pile produced the lowest pile capacity which was 0.491 kN. For 25 mm, pile capacity using J&R is 0.543 kN. Result shows the acceptable for J&R methods to be introduced with further investigation such as the response of pile under axial loading and others.

Experimental study on the behavior of a new post-grouted micropile in a tropical soil

This work aims to analyze the behavior of a new post-grouted micropile setup developed in tropical soil. Its main innovation is the use of high mechanical resistance steel pipes (N80 class) for drilling and as a structural component of the micropiles. The pipes have special manchette valves uniformly spaced to allow neat cement grout injection into the soil. Two instrumented micropiles with 0.3 m diameter (after injection) and lengths of 19.4 m and 21 m were installed at Experimental Site III of the University of Campinas (Unicamp). The geological profile of this site presents a sandy clay surface layer (porous and collapsible) followed by a layer of sandy silt (diabase residual soil). The piles were subjected to compressive slow maintained loading tests and were instrumented along their depth with strain gages. No geotechnical failure was observed during the load test. The maximum load achieved by the MC1 and MC2 micropiles were 2.210 kN and 2.470 kN, respectively. The load test data were extrapolated to estimate the ultimate geotechnical pile capacity. The extrapolated geotechnical failure load was above 2.500 kN for both micropiles and similar to those estimated by the Federal Highway Administration FHWA (2005) load capacity method. It was verified that (1) the pile material undergoes creep under stress above 25 MPa on the transversal section of the pile and (2) the debonding effect during the loading process. The micropiles showed higher values of skin friction compared with other piles installed in the same geological-geotechnical context (tropical soil).

The Effects and Vertical Bearing Capacity of Two Jacked Model Piles in Sand

The effects and vertical bearing capacity of two jacked piles in sand are still not well understood, and the mechanism of the adjacent pile’s uplift caused by the jacking pile in a double pile system is especially unclear, but these facets are important to the stability of the jacked pile. In this paper, a series of tests is performed on jacked model piles in sand, where in the influences of the pile length and the driving pile’s speed on the effects and vertical bearing capacity of two jacked piles were studied. The results revealed that the effects and vertical bearing capacity of the two jacked piles were mainly in relation to pile length and influenced by the driving speed. The horizontal displacement of the top of the first jacking pile during the installation of the post-jacking pile was caused by the difference in the stress state of the first jacking pile between the side of the pile’s face and its back side, in which the uplift displacement of the first jacking pile was also involved. The radial stress of the pile increased nonlinearly with the depth under different pile lengths and gradually converged to the passive earth pressure. The ultimate capacity of the double pile is approximately twice that of a single pile, and the ratio of the ultimate capacity of a single pile to the final jacking pressure was approximately 1.04.

Ultimate Bearing Capacity of Helical Piles as Electric Transmission Tower Foundations in Unsaturated Soils: Analytical, Numerical, and Experimental Investigations

Ultimate Bearing Capacity of Helical Piles as Electric Transmission Tower Foundations in Unsaturated Soils: Analytical, Numerical, and Experimental Investigations

Study on the rupture surface morphology and ultimate bearing capacity of a self-anchored test pile

The expression of the ultimate bearing capacity of the upper uplift pile and the lower compressive pile of a self-anchored test pile was obtained by studying their rupture surface morphology. The upper uplift pile had a composite shear rupture surface shape, and the lower compressive pile had the Meyerhof rupture surface shape. Since the interaction between the upper pile and lower pile of a self-anchored test pile is negligible, the expression form of the ultimate bearing capacity of a self-anchored test pile was obtained based on the transformation formula of its bearing capacity. Under the test conditions, the rupture surface morphology of a self-anchored test pile belongs to the situation when the equilibrium point is inside the rupture surface of the lower compressive pile. The theoretical rupture surface is approximately 0.09 m away from the pile side at ground level (1.8 d, where d is the pile diameter). Compared with the distance of the measured rupture surface of the upper uplift pile to the pile side, the difference value is -2.17%. The calculated ultimate bearing capacities of the upper uplift and lower compressive piles are 1287.34 N and 1201.65 N, respectively. The ultimate bearing capacity of the self-anchored test pile is approximately 2726.16 N. Compared with the experimental values of the upper pile and lower pile of the self-anchored test pile, the difference values are + 0.97% and − 7.57%, respectively. Compared with the experimental values of the traditional test piles, the difference value is − 2.64%. The rupture surface morphology and the expression of the ultimate bearing capacity of the self-anchored test pile in this paper can provide a research basis reference for calculating the ultimate bearing capacity of the self-anchored test piles with different pile sizes and soil properties.

Prediction and Optimization of Pile Bearing Capacity Considering Effects of Time

Prediction of pile bearing capacity has been considered an unsolved problem for years. This study presents a practical solution for the preparation and maximization of pile bearing capacity, considering the effects of time after the end of pile driving. The prediction phase proposes an intelligent equation using a genetic programming (GP) model. Thus, pile geometry, soil properties, initial pile capacity, and time after the end of driving were considered predictors to predict pile bearing capacity. The developed GP equation provided an acceptable level of accuracy in estimating pile bearing capacity. In the optimization phase, the developed GP equation was used as input in two powerful optimization algorithms, namely, the artificial bee colony (ABC) and the grey wolf optimization (GWO), in order to obtain the highest bearing capacity of the pile, which corresponds to the optimum values for input parameters. Among these two algorithms, GWO obtained a higher value for pile capacity compared to the ABC algorithm. The introduced models and their modeling procedure in this study can be used to predict the ultimate capacity of piles in such projects.

Theoretical Analysis of the Influence of a Sectional Form of a Flexible NT-CEP Pile Disc on the Anti-tilting Loading Performance

This work uses ANSYS software to simulate and analyze the new flexible concrete expanded plate (NT-CEP) piles, mainly evaluating the anti-overturning bearing performance of NT-CEP piles with different plate cross-sectional forms and the damage state of the soil around the pile. The software is used to design four groups of model piles with different plate cross-sectional forms and conduct an in-depth analysis of the displacement cloud diagram, load—displacement curve, and stress cloud diagram after load failure. The pile-soil force mechanism and failure law are obtained, and the flexible NT-CEP is analyzed. The calculation model of the ultimate horizontal bearing capacity of the NT-CEP piles supplements the theoretical results of the concrete expanded piles under horizontal loads and provides theoretical support for its design and popularization in practical engineering.

Prediction of axial load bearing capacity of PHC nodular pile using Bayesian regularization artificial neural network

Pre-stressed precast high strength concrete (PHC) nodular piles with hyper-MEGA construction method are favorably used in medium to high-rise building foundations. In this study, a feed-forward neural network (FFNN) was adopted to investigate the ultimate axial load bearing capacity of the PHC nodular pile. The network receives the composite pile and geotechnical conditions with eight input neurons and outputs the nodular pile's ultimate axial load bearing capacity. Among numerous possible FFNN network architectures, the most accurate one is determined by optimizing the hidden layer. Network training is conducted with Bayesian regularization backpropagation (BRB); the training datasets consist of static pile load test and standard penetration test index of soil profile collected from various projects in Vietnam. The significance of each input parameter is quantified with importance-based sensitivity analysis. An explicit function has been constructed from weights and bias values at each neuron in the FFNN to estimate the axial load bearing capacity. The excellent agreement of all output values by the proposed FFNN with the measured values proved the model’s robustness and reliability. The predictive capacity of the proposed FFNN model has significantly outperformed all current empirical formulas. The outcome of this study can be directly put into engineering practice to furnish an economically optimal design of the composite nodular pile.

Centrifuge model tests and settlement calculation of belled and multi-belled piles in loess area

Belled and multi-belled piles are cast-in-place piles with one or several bell-shaped enlargements. In this study, centrifuge model tests were conducted to explore the bearing mechanism of belled and multi-belled piles in loess area. It was found that both the bell shape forming and pile loading procedure lead to the compaction effect of soil adjacent to the pile which was shown intuitively as the mutation of axial force and side friction resistance at certain positions of pile shaft. The compaction effect due to the bell-shape enlargement transformed to the squeeze out behavior when the bell is oversize, with negative effects on the bearing capacity of piles. The compaction effect due to bell tip stress together with the bell tip resistance strengthens the attenuation rate of pile axial force. A stable relationship in the percentages of bell tip resistance, pile tip resistance and the upper load was also found at the later load stage of multi-belled piles. A settlement calculation formula for multi-belled piles was proposed based on Mindlin solution. Finally, the accuracy of the formula was verified by model test results. The method for predicting the ultimate bearing capacity of multi-belled piles was proposed, and it was verified by an in-situ worked-out example.

Micromechanical analysis of the particle corner breakage effect on pile penetration resistance and formation of breakage zones in coral sand

Although particle corner breakage has proven to be the major breakage mode of irregular grains, most pile–soil interaction analysis has focused on particle fracture breakage, thus the microscopic mechanism of sharp settlement/stress change for piles in coral sand remains unclear. This particle corner breakage–based study features laboratory pile penetration tests as well as DEM simulations. In the laboratory tests, in-situ sand samples that avoid slipping loss of corner debris are obtained and adopted. During DEM simulations, the cluster method is adopted with the linear parallel bond model. Unlike with classical friction resistance of piles, the particular shrinkage of friction resistance of piles in coral sand can be seen as resulting from a dual effect of corners. An additional increase in confining pressure was not efficient at improving the ultimate friction-bearing capacity of piles in crushable angular grains. As indicated by a diagram describing relationships between corner breakage and effective contacts, the force transmission in soil is newly generated, allowing interpretation of the sharp decrease of pile friction-bearing capacity. Findings indicate that higher grain angularity increases particle breakage within a narrower shear zone in soil samples. Finally, a particular relationship between particle breakage mode and the breakage zone around the pile tip is derived. This study sheds light on the microscopic mechanism of pile penetration in crushable granular soils, offering guidance for evaluating the ground-bearing capacity of angular granular soils.

A novel direct SPT method to accurately estimate ultimate axial bearing capacity of bored PHC nodular piles with 81 case studies in Vietnam

Bored PHC nodular piles (BPNP) are an eco-friendly and advantageous option for pile foundations of medium-rise to high-rise buildings. As none of the current methods to estimate the ultimate axial load-bearing capacity is accurate enough for BPNP in engineering practice, this study aims to achieve that objective by developing a new direct SPT method. To that end, we use static pile load test and SPT data of 81 PHC nodular piles collected in Vietnam. The ultimate bearing capacity is interpreted from the load–displacement curve in pile static load tests by various methods to determine the most suitable method for the nodular piles. Furthermore, 8 methods to determine axial load pile capacity directly from the standard penetration test are examined. Each method’s effectiveness is evaluated by comparing its predicted values with the measured values. Finally, the genetic algorithm for function optimization is employed to develop a new direct SPT method that can accurately predict the ultimate axial load-bearing capacity of nodular piles. The reliability of the proposed formula is justified by comparing the proportion of end bearing capacity with other published works. It is verified that the developed directed SPT method outperforms all current methods and could be implemented directly in engineering practice.

Estimation of ultimate bearing capacity of bored piles using machine learning models

The ultimate bearing capacity of bored piles is an essential parameter in foundation design of structure. In the present study, three Machine Learning (ML) methods namely Adaptive Neuro-Fuzzy Inference System (ANFIS), Support Vector Machine (SVM) and Artificial Neural Network (ANN) were utilized to estimate bearing capacity of bored piles based on limited engineering parameters of pile and soil obtained from 75 test sites in Vietnam. These parameters include pile diameter, pile length, tensile strength of main longitudinal steel bar, compressive strength of concrete, average SPT index at the tip of the pile, average SPT index at the pile body. Validation of the methods was verified using standard statistical metrics namely Root Mean Square Error (RMSE) and Correlation coefficient (R). The results show that all the proposed models have good potential in predicting correctly bearing capacity of bored piles on training data (R>0.93) and on testing data (R>0.88) but performance of the SVM model is the best (R:0.985 (training) and R:0.958 (testing). Thus SVM model can be used for the accurate prediction of ultimate bearing capacity of bored piles for proper designing of the civil engineering structure foundation.

Modified Meyerhof approach for forecasting reliable ultimate capacity of the large diameter bored piles

The static loading test is undoubtedly the most reliable method for forecasting the ultimate capacity of the large diameter bored piles (LDBP). However, in-situ loading of this class of piles until reaching failure is practically seldom due to the large amount of settlement required for shaft and base mobilization. Therefore, many international design standards recommend either capacity-based or settlement-based methods to estimate the LDBP ultimate capacity in case of the impossibility of performing loading tests during the design phase. However, those methods are invariably associated with various degrees of uncertainty resulting from several factors, as evidenced in several comparative analyses available in the literature. For instance, the settlement-based method of the Egyptian code of practice (ECP 202/4) usually underestimates the ultimate capacity of LDBP. In contrast, Meyerhof's capacity-based method often overestimates the LDBP’s ultimate capacity. In this paper, a modified approach has been proposed to forecast the ultimate capacity of the LDBP. This approach was modified from Meyerhof’s classical formula (1976) through three fundamental stages. First, an assessment study was performed to evaluate the reliability of the estimated LDBP ultimate capacity using Meyerhof’s classical method. For this purpose, results of full scale loaded to failure loading LDBP test and related twenty-eight parametric numerical models with various pile geometrical and soil geotechnical parameters have been used. Based on the assessment study findings, the essential modifications were suggested in the second stage to adapt Meyerhof’s classic method. In the third stage, the results of several numerical models and in-situ loading tests were employed to assess the accuracy of the developed modified method. This study showed that Meyerhof's classical method overestimated the ultimate capacity of LDBP with an error percentage ranging from 14 to 46%. On the other side, the proposed modified approach has succeeded in estimating the ultimate capacity of loaded to failure in-situ LDBP test and twenty numerical LDBP models with error percentages ranging from 0.267 to 7.75%.

Prediction of Ultimate Antifloating Force of Bored Piles in Urban Road Crossing Overpass

As an effective antifloating measurement in underpass engineering, uplift piles have been widely employed in the antifloating design of underground structures, such as basements, underground roads, and underground shopping malls. For the purpose of studying the antifloating behavior of bored piles and predicting the uplift bearing capacity in underpass engineering, the on-site pull-out tests of bored piles are carried out in laboratory. Besides, the MMF growth curve model, the ordinary hyperbolic model, and the exponential model are employed to fit and predict the ultimate bearing capacity of the measured uplift load and uplift displacement data of three test piles, respectively. The research results indicate that three test piles meet the stability requirements of antibuoyant bearing capacity, and the pull-up load-displacement curves of test piles are gentle and steep. Meanwhile, the fitting accuracy of the pull-displacement curve is high; specifically, the correlation coefficient is above 0.98619, and the average value is 0.99134, thereby verifying that the fitting effect of MMF growth curve model is better than those of the hyperbolic model and the exponential model. Therefore, the MMF growth curve model proposed in this paper not only describes the fitting of the uplift load-uplift displacement curve of uplift piles accurately but also predicts the ultimate bearing capacity of test piles. The research results provide an important reference for the antifloating behavior of bored piles in underpass engineering.

Method for Calculating Vertical Compression Bearing Capacity of the Static Drill Rooted Nodular Pile

The static drill rooted nodular (SDRN) pile is a new kind of composite pile foundation made by inserting a precast nodular pile into the cemented soil. Based on the tests and analysis on the mechanism characteristics of these two kinds of interfaces, which are between the pile and cemented soil, and between the cemented soil and soil, this paper proposes a calculation method for the ultimate vertical bearing capability of the SDRN pile considering two failure modes. When the precast pile and surrounding cemented soil fails as a whole, the diameter of the cemented soil pile is taken to calculate the ultimate shaft resistance, and the shaft resistance of the SDRN pile is about 1.05∼1.10 times that of the bored pile in the same soil layer. When the core precast pile fails in penetration mode, the diameter of the core pile is taken. The pile shaft resistance takes that of displacement piles in the same soil layer. The lower nodular pile shaft resistance should consider the squeezing effect of nodular joints. Besides, the improvement of pile tip resistance due to the expanded cemented soil should also be taken into consideration. The result is the smaller value calculated according to these two failure modes. The ultimate bearing capacity of a SDRN pile calculated by the theoretical method is not only compared with the field test result, but also the simulation result of a 2D model pile built by PLAXIS finite element software. In addition, the finite element simulation is also confirmed to be an effective way to investigate the mechanism characteristics of SDRN piles more thoroughly.

Estimation of the Large Diameter Bored Pile Ultimate Capacity Using Different Design Methods: Assessment Study

In this paper, in situ measurements of two well-instrumented loading tests performed on large diameter bored piles (LDBP) have been utilized to assess the reliability of the predicted ultimate pile capacity using three settlement-based and capacity-based methods. The first test was conducted on a short LDBP with a 1.3m and 9.50 length. This LDBP was constructed in stiff clay soil and loaded till the achievement of the failure. While the second in-situ loading test was performed on a long LDBP with a 1.00 m diameter and 34.00 m length. This LDBP was constructed in multi-layered soil and examined under three axially loading and unloading cycles to obtain the ultimate load settlement relationship. Although this LDBP was loaded with an applied load of three times its working capacity, but no apparent failure was reached at the end of the loading test. Thus, two different methods are adopted to interpret the test data and determine the ultimate pile capacity. The obtained ultimate capacities of the two tests were utilized in an assessment study. The comparative analysis results showed a significant difference between the ultimate capacity obtained using three different methods and field measurements. Out of the three utilized methods in this study, the two settlement-based methods underestimated the LDBP ultimate capacity of the two LDBP cases; conversely, the third capacity-based method overestimated the ultimate capacity of the two LDBP cases.

Uncertainty Analysis of Axial Pile Capacity in Layered Soils by the Piezocone Penetration Test

This study presented a framework for uncertainty analysis of the ultimate axial bearing capacity of piles evaluated by the UniCone method in layered soils. The UniCone method by Eslami and Fellenius (1997) is a direct piezocone penetration test (CPTU) method for evaluating the ultimate axial capacity of piles in the reliability design. The spatial variability of CPTU data is modeled as a random field for each soil unit in the soil strata. The empirical correlation coefficients of the UniCone method are assumed to follow lognormal distributions. On the basis of uncertainties of CPTU data and empirical correlation coefficients, the first-order reliability method (FORM) is then applied to the reliability analysis of ultimate axial bearing capacity of piles. The effects of spatial variability of CPTU data and variations of empirical correlation coefficients on the ultimate axial bearing capacity of piles are evaluated by an Excel spreadsheet-based framework. Seven case studies show that the proper identification of different soil units from soil profiles is crucial for estimating the failure probability of pile capacity in the reliability analysis. Uncertainties of CPTU data and empirical correlation coefficients would be over-estimated unless different soil units in soil profiles are identified properly from each other. The over-estimated geotechnical parameters contribute to a higher failure probability of pile capacity. The proposed framework can evaluate the uncertainty of the ultimate axial bearing capacity of pile foundations more rationally.

Performance control of root piles using a digital odometer

Root piles are injected and installed during mortar shaft construction, using pressures of up to 500 kPa. The executive control is typically done through static load testing, an expensive and time-consuming method. Static load tests on eight controlled piles (diameters between 310 mm and 410 mm) were performed, aiming at evaluating pile ultimate load. This study suggests an innovative, non-destructive approach to validate root pile field performance, using a digital speedometer connected to the drilling rig’s rotating head. The proposed method monitors variables related to bearing capacity during pile installation and proposes an empirical equation to estimate the ultimate bearing capacity of root piles. For the assessed piles, the predictions obtained with the proposed equations agreed fairly well with results from static load tests, proving it as a feasible and helpful option for the executive control of root piles, especially when load tests are not available.

Prediction of Pile Shaft Capacity in Tension Based on Some Direct CPT Methods-Vistula Marshland Test Site.

This paper presents different CPT methodologies for the prediction of the pile shaft resistance in tension on the example of three reference screw piles of the Jazowa test site in Poland. The shaft capacity was estimated based on the cone resistance, sleeve friction and CPT excess pore water pressure. Three piles with a diameter of 0.4 m and the length varied from 8 m to 14.6 m were subjected to static load tests in tension. Their results were used to determine the ultimate bearing capacity of the reference piles. The pile shaft resistance was estimated according to the AFNOR standard, Doan and Lehane 2018 centrifuge tests based method (Delft University of Technology approach), the Modified Unicone method, KTRI (Kajima Technical Research Institute) and LCPC (Laboratoire Central des Ponts et Chaussées) method. Then, the ultimate bearing capacity determined in static load tests was compared to the estimated values according to five different methods. The best estimation, fitting almost perfectly to static load test values, was obtained with the AFNOR method, whereas the other predictions significantly underestimated the ultimate bearing capacity.

Three-dimensional scour hole model and scour effects on the ultimate capacity of lateral loaded rigid piles

The rigid pile with a large diameter and a small slenderness ratio is the most widely used foundation for offshore wind turbines. Scour around piles seriously threatens the safe operation of offshore wind turbines, so its effects on rigid piles need to be studied urgently. In this paper, scour tests under steady current and static lateral load tests after scour are conducted. According to the results of scour tests, a three-dimensional scour hole model suitable for engineering reality and its analytical expression are proposed. Then, the results of load tests indicate that scour reduces the ultimate lateral capacity of foundations, and the percentage of reduction is related to the current direction, whereas does not change with load eccentricity. Finally, a preliminary formula for evaluating the ultimate lateral capacity of rigid piles after scour is presented, which can easily and quickly determine the upper and lower limits of scour effects.