High Strain Dynamic Testing Research Articles

An Evolutionary Polynomial Computing of Pile Capacity Using the Results of High-strain Dynamic Test

An Evolutionary Polynomial Computing of Pile Capacity Using the Results of High-strain Dynamic Test

Analysis on the synergistic variation law of pile refreezing process and bearing capacity based on high-strain dynamic test method

The high-strain dynamic test method possesses the attributes of speed, efficiency, and environmentally-friendly, low-carbon characteristics. To study the reliability of the high-strain dynamic test method in detecting the bearing capacity of pile foundation in permafrost regions, 4 test piles, each with a length of 15 m and a diameter of 1.0 m, were poured based on the actual bridge construction project in the permafrost region of Daxing'an Mountains in China. Based on the temperature data between the piles and soil, the refreezing state of the pile foundation was comprehensively judged. Subsequently, the static method was employed to assess the friction resistance values and single pile bearing capacity of each soil layer on the pile side under different freezing states before and after the pile foundation refreezing. Building upon these findings, the restrictive parameters for soil elastic limit q_{(i)}, soil resistance R_{U} (i) and other parameters in the pile-soil model of high-strain dynamic test method are clarified. The test and analysis results indicate that under the condition that the ground temperature of frozen soil is about − 1.9 °C, the pile-soil refreezing takes about 120 days, and the pile-soil refreezing is a slow process; In CAPWAPC calculation program, after the values of soil parameters were constrained by the results of static-load test, the calculated curve is in satisfactory agreement with the measured curve, and the parameters of the pile-soil model are reliable, which can be used for the rapid detection of the ultimate bearing capacity of piles in permafrost regions; In the process of pile-soil refreezing, the change of temperature field affects the freezing strength between pile and soil, the process of pile-soil refreezing is positively correlated with the increase of pile foundation bearing capacity.

Lessons learned from large-scale physical modeling of tapered jacking piles: HSDT

To provide an improved understanding of the behavior of screw piles in disturbed soil, as a series of companion papers, laboratory tests with full scale tapered jacking piles were performed in the current study. The designated tapered pile has the similar dimensions, material properties and cone-shaped bottom, with the exception of threads eliminated.
 The main objectives of this paper are to: (1) establish the robust and efficient simple high strain dynamic testing (HSDT) requirements for validating displacement tapered piles capacities while exploring the installation effect; (2) determine a correlation between static and dynamic bearing capacity in compression for steel tapered piles installed by jacking in sand with various relative densities.
 Out of nine large-scale laboratory expriments at Aalborg University Offshore Geotechnics Laboratory [1-3] with the tank filled with Aalborg University Sand No.1, this research exclusively presents some lessons learned from an exemplar tapered jacking pile installation (Test 4) in dry sand (relative density and its response to monotonic and impact loadings. The selected piles have diameter of D=76 mm and 89 mm with length of 2.07 m. The layout of the miniature CPTs carried out to measure soil state is shown in Fig. 1, with four CPTs performed following each jacking installation campaign to study the soil state after the installation of the piles (Fig. 1). In order to fulfill the objectives, the piles are installed by a static compression load that includes an unloading/reloading step, followed by dynamic testing in order to facilitate the determination of the bearing capacity (Fig. 2). The hammer test was carried out on both piles, by a hammer from increasing drop heights of 218, 418, 618, 818 and 1018 mm (Fig.3). The hammer consists of a sleigh with multiple attached steel plates weighting 19.31 kg on average and the sleigh itself weighs 18.55 kg. Tapered pile jacking resulted in dilation extending to a depth of 2.8when diameter exceeds from 76 mm to 89 mm. By contrast, in the region around pile P76, the soil was entirely densified. The tendency to densify the soil near tip area due to jacking installation is observed in both tests, where the initial viod ratio varied from 0.67 to 0.59 and from 0.63 to 0.57 corresponding to piles P76 and P89, respectively (Fig.4).
 Subseuqntluy, Danish Pile Driving Formulas (DDR) introduced by [4] was ustilised which is according to the required potential energy from a hammer stroke to exceed the pile penetration resistance. The mass of the hammer G is defined by:
 where elastic settlement =, A is cross-sectional area, E is the Young’s modulus, l is the installed length of pile which is approximately 1.9 m, and is the maximum static force required to install the pile. The efficiency factor is set as 1. During the impact loading tests, the settlement of the pile is measured with a 1 mm accuracy for each hammer stroke, and the limiting settlement, s was set to yield a certain level (0.1D) when the drop height is 618 mm. Thus, the dynamic bearing capacity = , and ratio= are shown in Table 1.

Research on Dynamic Pile-Driving Formula Parameters and Driving Feasibility of Extra-Long PHC Pipe Piles

Prestressed high-strength concrete (PHC) pipe pile has the advantages of high single pile bearing capacity, a wide range of applications, good driving resistance, fast construction speed, etc. It has been widely used in high-rise buildings, bridges, ports, and other industries. The application of extra-long PHC pipe piles with a length of more than 50 m is increasing. However, there are few studies on the drivability and hammering criteria of extra-long PHC piles. To analyze the drivability of extra-long piles and predict their bearing capacity, in this paper, high-strain dynamic tests were carried out on 14 test sections with the pile foundation of Temburong Bridge in Brunei as the research background. The hammer stop control criteria calculated according to the Hiley formula would lead to excessive hammering. Three types of damage occurred during construction: pile shaft breakage, weld tearing, and pile head breakage. The weight and drop height of the piling hammer selected for this project were appropriate, and the extra-long test piles can be hammered to the design depth. The values of Cp (Compression of the pile) and n (the efficiency of the blow) were fitted based on the dynamic test data, which provided a more accurate reference for the selection of subsequent piling parameters of the project. It provides a more accurate calculation method for predicting the bearing capacity of extra-long PHC piles and provides control criteria for pile stopping and a scientific basis for their design and construction.

Dynamic analysis model of open-ended pipe piles that considers soil plug slippage

The high-strain dynamic load test (HSDT) is a convenient and efficient method of assessing the compressive load capacity of piles. Although several numerical models are available to interpret the responses of open-ended pipe pipes (OEPPs) in the HSDT, these models cannot capture the motions of pile base soil or distinguish the difference in the external and internal soil resistance of the OEPPs. Thus, a novel fictitious-soil pile (FSP) model is developed in this study to analyze the responses of small-diameter OEPPs with soil plugs under high-strain impact loading. Apart from simulating the wave propagation in the base soil and slippage at the pile–soil interface, the proposed model also describes the sliding modes of the soil plug under dynamic load conditions (DLCs). The developed model was validated by comparing the calculated pile responses with those obtained from conventional numerical models as well as field measurements of a steel OEPP. Based on the proposed model, two sliding modes of the soil plug (bottom- and top-sliding) were found in the HSDT to be dependent on impact loading durations. The prediction of the OPEE load capacity from HSDTs could be affected by the soil sliding mode, which should be investigated in more detail in future research.

Evaluation of bearing capacity of PHC pipe piles via the dynamic and static loading test

Due to its faster implementation and potential cost savings for estimating the bearing capacity of PHC pipe piles, the High Strain Dynamic Test (HSDT) offers an alternative approach to Static Load Test (SLT). The report presents a bearing capacity study via those methods with a sliding micrometer. And a Pile Driving Analyzer (PDA) imported from the United States is employed, to determine the design parameters of pile foundation engineering and provide the error sources of bearing capacity. Sliding micrometers with cone-shaped rings are embedded in the inner side of the pile piles every 1 m for measuring the strain. The law of stress and strain at various depths during loading is presented in this paper. As a new concept, the “inflection point” is proposed by the relationship between shaft resistance and relative displacement of pile-soil. By comparing the SLT and HSDT, the relationship between toe resistance and settlement of pile is demonstrated. This paper analyses the reliability and precision, and explore the error source so as to provide theoretical evidence for trail-pile testing in future. And the error of bearing capacity between SLT and HSDT with CAPWAP studies shows that the HSDT could provide adequate results for assessing the bearing capacity of PHC pipe piles.

Concrete Pile Defect Identification: Insights from Cross-Hole Sonic Logging and High Strain Dynamic Pile Test

This paper aims to identify the types of defects, location of defects, size of defects, and capacity of five concrete piles using a High strain dynamic pile test and Cross-hole sonic logging test. In this study, Cross-Hole Sonic Logging method (CSL) is a potent quality-control tool that exclusively detects much smaller flaws with high accuracy with utilizing velocity and first arrival time (FAT) from ultrasonic waves to find out the integrity of the drill shaft. From CSL test, the bearing capacity needs to be calculated manually using a waterfall diagram and soil profile. Moreover, the high strain dynamic pile test is used to identify integrity and bearing capacity of concrete pile via resistance analysis down to the pile and split of the base to shaft resistance when only pile head measurements are taken then using Case Method and CAPWAP analysis. Through this analysis, the bearing capacity can be interpreted; the Belta (damage factor) is applied to estimate location and size of the defect in the concrete pile. Based on the result of CLS test for three concrete piles, P01, P04, and P10, indicated that P01 and P04 are “Good” pile integrity with the bearing capacity of 4583kN and 6600kN, while P10 showed as “Potential defect at depth 9.25m to 10.25m” of pile integrity with bearing capacity of 6600kN. Furthermore, High strain dynamic pile test of two concrete piles, P2E and P2P, showed that the integrity category is “Ok” with bearing capacity 9896kN.

Nonlinear fictitious-soil pile model for pile high-strain dynamic analysis

Existing numerical models for simulating the pile behaviours in high-strain dynamic load tests (DLTs) cannot account for the wave propagation in base soil. This paper proposes a nonlinear fictitious-soil pile (FSP) model to better simulate the base soil. The proposed model regards the base soil as a FSP with a cone angle extending from pile toe to bedrock, and simulates shaft resistance by improved Randolph model. The pile-soil system is discretized into a series of mass-nonlinear springs, and was solved based on the Newmark’s β method. The proposed model was validated by comparing its predictions with those obtained from Randolph model and Smith model, as well as field measurements of driven and bored piles in different sites. Parametric study demonstrated that the calculated results were significantly affected by the discretization degree, FSP dimensions and soil nonlinearity. The displacement attenuation in base soil is nonlinear, and the impact energy is consumed rapidly near pile toe. Besides, large-diameter piles tend to have a larger affected zone, in which the wave phenomenon in base soil should be considered. Empirical formulas for soil affected zone and required pile displacements in DLTs were proposed to facilitate the practical application of FSP model.

Evaluation of capacity of power hammer machine foundation from high strain dynamic load test: Field test and axisymmetric numerical modeling

The power hammer machines induce harmful vibrations in different parts of the foundation which may result in excessive dynamic settlement. While designing the hammer machine foundation, variety of static and repetitive impact load tests are generally conducted to ensure both the stability and serviceability of the foundation system. The static load test (SLT) is performed in the case of such foundations to obtain the ultimate capacity. However, the SLT is unable to predict the reliable response of the machine foundation. Hence, the current study is aimed to investigate the static and dynamic resistance of power hammer machine foundation by employing the high strain dynamic load test (DLT). The test procedure involves measuring the acceleration, axial force and settlement at the top of the machine foundation. Additionally, the soil resistance pertaining to damping is assumed to disappear with the zero-velocity at the first moment, which is identical to the unloading point method (UPM). Also, the field test and axisymmetric finite element analysis by considering the nonlinear soil model were performed to evaluate the stress settlement curve (SSC) from both SLT and DLT. The results reveal that the capacity of the machine foundation subjected to repetitive dynamic loads increases gradually and then tend to remain stable in case of additional impact loads. The SLTs showed 3–4 % higher static resistance than the first DLT and 8–9 % reduction in contrast to the second DLT. Moreover, the residual plastic deformation of the soil beneath the machine foundation was recorded to rapidly increase at the beginning of hammer tamping while it decreased steadily with further increasing of the hammer blows.

Bearing performance of steel pipe pile in multilayered marine soil using fiber optic technique: A case study

It is important to appraise the performance of the steel pipe pile performance in harbor engineering. The load transfer mechanism and pile-soil interaction could not be clearly understood using the traditional measurement. In this case, fiber Bragg grating (FBG) and Brillouin optical time domain reflectometry (BOTDR) were applied simultaneously at an open-ended steel pipe pile field test in Ganyu Port, China. Results showed that the fiber optic sensing system accurately measured the axial force, side friction, and bearing behaviors of open-ended steel pipe piles based on strain data. During the pile driving stage, the system captured the bending deformation and eccentric load on the upper part of the pile above the mud surface, identifying the relatively large tensile strain at the final stage of driving. For the static load test, the strain and resistance distribution obtained by sensing systems suggested that 80% of pile compression was concentrated in the upper 20 m, and the maximum force was observed at the location of soil surface. The precision of high strain dynamic tests is limited for complex field conditions and model’s parameters-setting.

Factors Influencing Pile Friction Bearing Capacity: Proposing a Novel Procedure Based on Gradient Boosted Tree Technique

In geotechnical engineering, there is a need to propose a practical, reliable and accurate way for the estimation of pile bearing capacity. A direct measure of this parameter is difficult and expensive to achieve on-site, and needs a series of machine settings. This study aims to introduce a process for selecting the most important parameters in the area of pile capacity and to propose several tree-based techniques for forecasting the pile bearing capacity, all of which are fully intelligent. In terms of the first objective, pile length, hammer drop height, pile diameter, hammer weight, and N values of the standard penetration test were selected as the most important factors for estimating pile capacity. These were then used as model inputs in different tree-based techniques, i.e., decision tree (DT), random forest (RF), and gradient boosted tree (GBT) in order to predict pile friction bearing capacity. This was implemented with the help of 130 High Strain Dynamic Load tests which were conducted in the Kepong area, Malaysia. The developed tree-based models were assessed using various statistical indices and the best performance with the lowest system error was obtained by the GBT technique. The coefficient of determination (R2) values of 0.901 and 0.816 for the train and test parts of the GBT model, respectively, showed the power and capability of this tree-based model in estimating pile friction bearing capacity. The GBT model and the input selection process proposed in this research can be introduced as a new, powerful, and practical methodology to predict pile capacity in real projects.

Limitations of the Danish driving formula for short piles

Dynamic formulae are a widely used expedient for the control of driven piles to ensure load capacity. These formulae have considerable limitations when used in the prediction of the load capacity on their own, but are very useful in the control of a piling when combined with other tests. This technical note presents an evaluation of the Danish Formula for 54 precast concrete piles, comparing its results with High Strain Dynamic Tests (HSDTs), Static Load Tests (SLTs) and predictions by a semi-empirical static method (Aoki & Velloso, 1975). The data used in the comparison come from three works in the city of Rio de Janeiro, Brazil. All piles were driven with free-fall hammers and in one particular work the piles were relatively short. The predictions of the Danish Formula were evaluated in relation to the pile length/diameter ratio. It was concluded that for short piles - with lengths less than 30 times the diameter - this formula indicates bearing capacities higher than the actual ones. A correction for a safe use of the Danish Formula for short piles is suggested.

Load-Transfer Mechanism of Helical Piles Under Compressive and Impact Loading

Abstract Helical piles are currently used to support large compressive loads, which requires accurate evaluation of their bearing capacity. High strain dynamic load testing is increasingly used to ...

Analytical models of impact force-time response generated from high strain dynamic load test on driven and helical piles

The High Strain Dynamic Test (HSDT) offers an alternative approach to the conventional static load test for estimating the axial capacity of helical piles due to its faster implementation and potential cost savings. In this paper, a mathematical model developed by Clough & Penzien that simulates the force-time response at the top of a pile with uniform cross-section subjected to a hammer impact is evaluated for the HSDT setup. To verify the suitability of the model, the calculated force-time history from the mathematical model is compared with actual field data for driven and bored piles. The model is then used to explore the characteristics of hammer impact on helical piles with attention to estimating the impedance increase caused by the helices. Generally, helices offer additional end bearing resistance, thus increase the mechanical impedance of the pile. The obtained results demonstrate that it is necessary to account for the effect of helical plates in the analysis, especially for large diameter helical piles. Consequently, a method to approximate the increase in the pile impedance for a helical pile with single and double helices is developed using added soil mass model.

Finite element analysis of helical piles subjected to axial impact loading

Abstract Two-dimensional (axi-symmetrical) dynamic finite element analyses were performed to simulate the static load tests (SLT) and High Strain Dynamic Load Tests (HSDT) conducted on helical piles to gain better understanding of their behaviour during the tests. The finite element models were verified using the results of two case histories involving SLT and HSDT on large diameter helical piles. The finite element models simulated the helical piles installed in both sand and clay soils and were used to characterize soil-pile interaction during the tests and to establish the derived static load-settlement curves for both types of soil. The verified numerical models were employed to perform a comprehensive parametric study to investigate the influence of various material and geometric aspects of the soil-pile-hammer system on the dynamic response of helical piles during axial impact loads. The results from the parametric study were used to formulate guidelines for the design of effective HSDT on helical piles as well as on driven piles.

A Novel Numerical Method for Calculating Vertical Bearing Capacity of Prestressed Pipe Piles

A novel method for calculating the vertical bearing capacity of prestressed pipe piles with the acceptable error was proposed and verified. Soils at the pile side and end were, respectively, simulated by an elastic‐plastic model and a new double‐line (at soft rock and soil layers) or triple‐line model (at hard rock and soil layers); then, a mechanical model was established for simulating vertical bearing capacity of prestressed pipe piles, and the corresponding calculation process was carried out. The values of pile side resistance, pile end resistance, and pile end elastic displacement were first obtained from the results of high‐strain dynamic testing (HSDT) and then were imported into the proposed numerical model for calculating the vertical bearing capacity of prestressed concrete pipe piles. The static load test was carried out to verify the numerical results. Besides, 20 piles were tested at two typical test sites (soft and hard rock bearing strata), of which 8 piles were arranged at the soft rock bearing stratum site and 12 piles were arranged at the hard rock bearing stratum site. The numerical results achieved from an empirical formula were also used for making a comparison. The values obtained by the proposed method were highly close to those achieved from the static load test with an error of within 10%. The outcomes indicated that the proposed numerical method can be potentially applied to predict the bearing capacity of prestressed pipe piles.

USING THE STRESS-WAVE THEORY TO DETERMINE THE BEARING CAPACITY OF PILES

High strain dynamic pile testing is usual practice, and has many benefits that make its use highly attractive. However, it requires careful preparation, specific equipment, attention to detail and testing engineer skill to properly perform these tests. Engineer skills for testing largely determines the non-proliferation of the method in Russia. Without of understanding wave equation analyses, the test engineer may not realize when results are valid, or when capacity results may be only a lower bound. It is widely known that the capacity of driven piles may change with time after installation and for that reason restrike tests are generally recommended. It is also generally stated that the set per blow should be at least 2 mm, or otherwise the dynamic test may only yield a lower bound solution. To confirm or refute these recommendations, an analysis of the existing test database was conducted, as well as an analysis of the tests performed at the Perm region facilities. The article presents the conclusions of this analysis and practical recommendations.

High strain dynamic testing of driven piles during the construction of the bridge across the Kerch Strait

In accordance with the Russian Federal Target Program of Social and Economic Development of the Crimea and Sevastopol, a bridge across the Kerch Strait is being built now. Of course, such complex structures are significant for Russia. Solving technical issues at different stages of engineering investigations, design, construction and operation of such objects it is required to attract specialists from scientific, educational, design, construction organizations, and manufacturers of building materials, structures and equipment from different countries. Before the implementation of this project, more than 70 different variations of the construction of the transport crossing were considered. These are combinations of bridges (cable, arched, girder, combined, etc.), tunnels and embankments in four sections of the Kerch Strait. As a result of the multifactor analysis, the optimal variation of the transition through the Tuzla point of two parallel bridges of about 19 km in length, with beam spans of 55-64 m, arches with a width of 227 m and a height of 45 m in the navigable channel was adopted. The bridge clearance for passage of ships is 185 × 35 m. To design a unique and complex bridge under existing regulations, special technical conditions were developed. When piles were driven, there were difficulties and issues that required prompt solutions. Employees of the Department of Highways and Bridges of the Perm National Research Polytechnic University were involved in testing piles and hammers. The design of foundations and the technology of driving piles were changed as the test results were obtained.

Quality Control Acceptance Criteria Improvements for Pre-Stressed High Strength Concrete Pile Driving Operations in Japanese Building Construction

The current practice in Japan for most driven pre-stressed high strength concrete (PHC) piling sites utilizes an ″energy formula″ approach involving the ″set-penetration test.″ In its current state, driven PHC piles in the Japanese construction industry are at increased risk of being damaged due to inferior driveability evaluation procedures leading to an increased probability of damaged piles remaining undetected after installation. This study presents two case studies in Okinawa, Japan which utilized dynamic analysis as the primary piling quality acceptance criteria and compares results to the energy formula approach which is more common to Japanese construction sites. Based on the observations of these two case studies, the applicability of dynamic testing, particularly the high-strain dynamic test, the low-strain integrity test, and wave equation analyses is analyzed. In conclusion, a case is presented that Japan′s over reliance on an energy formula approach should be augmented by additional QC procedures. A combination of wave equation analysis, dynamic testing and simple visual inspection of post-driven PHC pile conditions is recommended to better protect the integrity of driven PHC piles throughout Japan.

Application of Artificial Neural Network for Predicting Shaft and Tip Resistances of Concrete Piles

<p class="MsoNormal" style="text-align: justify; line-height: 200%;">Axial bearing capacity (ABC) of piles is usually determined by static load test (SLT). However, conducting SLT is costly and time-consuming. High strain dynamic pile testing (HSDPT) which is provided by pile driving analyzer (PDA) is a more recent approach for predicting the ABC of piles. In comparison to SLT, PDA test is quick and economical. Implementing feed forward back-propagation artificial neural network (ANN) for solving geotechnical problems has recently gained attention mainly due to its ability in finding complex nonlinear relationships among different parameters. In this study, an ANN-based predictive model for estimating ABC of piles and its distribution is proposed. For network construction purpose, 36 PDA tests were performed on various concrete piles in different project sites. The PDA results, pile geometrical characteristics as well as soil investigation data were used for training the ANN models. Findings indicate the feasibility of ANN in predicting ultimate, shaft and tip bearing resistances of piles. The coefficients of determination, R², equal to 0.941, 0.936, and 0.951 for testing data reveal that the shaft, tip and ultimate bearing capacities of piles predicted by ANN-based model are in close agreement with those of HSDPT. By using sensitivity analysis, it was found that the length and area of the piles are dominant factors in the proposed predictive model.</p><p class="MsoNormal" style="text-align: justify; line-height: 200%;"> </p><p class="MsoNormal" style="text-align: justify; line-height: 200%;"><strong>Resumen</strong></p><p class="MsoNormal" style="text-align: justify; line-height: 200%;">La Capacidad Axial de Soporte (ABC, en inglés) de un pilote de construcción se determina usualmente a través de una Prueba de Carga Estática (SLT, inglés). Sin embargo, estas pruebas son costosas y demandan tiempo. La evaluación de las Dinámicas de Alto Esfuerzo de Pilotes (HSDPT, inglés), que la provee el programa de Análisis de Excavación (PDA, inglés), es una forma de aproximación más reciente para preveer la Capacidad Axial de Soporte. En comparación con la Prueba de Cargas Estática, la evaluación PDA es rápida y económica. La implementación de Redes Neuronales Arficiales (ANN, en inglés) que permita resolver problemas geotécnicos ha ganado atención recientemente debido a su posibilidad de hallar relaciones no lineales entre los diferentes parámetros. En este estudio se propone un modelo predictivo ANN para estimar la Capacidad Axial de Soporte de pilotes y su distribución. Para fines de una red de construcción se realizaron 36 pruebas PDA en pilotes de diferentes proyectos. Los resultados de los Análisis de Excavación, las características geométricas de los pilotes, al igual que los datos de investigación del suelo se utilizaron para probar los modelos ANN. Los resultados indican la viabilidad del modelo ANN en predecir la resistencia de los pilotes. Los coeficientes de correlación, R², que alcanzaron 0.941, 09.36 y 0.951 para la evaluación de los datos, revelan que la capacidad del pilotaje en el último rodamiento, en el cojinete del eje y en la punta que se predijeron con el modelo ANN concuerda con las establecidas a través del HSDPT. A través del análisis de respuesta se determinó que la longitud y el área de los pilotes son factores dominantes en el modelo predictivo propuesto.</p>