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Due to the development of dedicated software and the computing capabilities of modern computers, the application of numerical methods to analyse more complex geotechnical problems is becoming increasingly common. However, there are still some areas which, due to the lack of unambiguous solutions, require a more thorough examination, e.g., the numerical simulations of displacement pile behaviour in soil. Difficulties in obtaining the convergence of simulations with the results of static load tests are mainly caused by problems with proper modelling of the pile installation process. Based on the numerical models developed so far, a new process of static load test modelling has been proposed, which includes the influence of pile installation on the soil in its vicinity and modelling of contact between steel pile and the soil. Although the presented method is not new, this is relevant and important for practitioners that may want to improve the design of displacement piles. The results of the numerical calculations were verified by comparing them with the results of pipe pile field tests carried out in a natural scale on the test field in Southern Poland.

This paper presents a comprehensive evaluation of the performance of Rigid Inclusion (RI) columns through the application of the Composite Modulus Calculation (CMC) methodology, addressing both short-term mechanical behavior and long-term settlement trends. The investigation is based on a real-world infrastructure project situated along the southern coast of Iran, involving the construction of large-scale storage tanks on geotechnically problematic soils. In the short-term analysis, a three-dimensional numerical model was developed and calibrated using the results of a full-scale static load test conducted on a single RI column. The close agreement between measured and simulated responses substantiates the accuracy of the adopted numerical approach. Subsequently, long-term performance was assessed via systematic interpretation of settlement monitoring data, analyzed within the CMC framework to capture the time-dependent behavior of the ground-structure system. Results indicate a pronounced mitigation of vertical deformations following ground improvement. Specifically, center settlements were reduced from an initial estimated value of approximately 42.3 cm to 17.9 cm, while peripheral settlements declined from 36.7 cm to 18.1 cm. These reductions signify the effectiveness of RI columns in enhancing vertical load distribution and controlling excessive settlements. Moreover, the utilization of RIs with varying embedment depths successfully minimized differential settlement across the tank footprint, maintaining total and differential displacements within permissible engineering thresholds. A hydrostatic loading test, spanning 133 days and achieving a maximum water elevation of 18 m, served as a validation benchmark. The recorded settlement profiles exhibited strong correlation with numerical predictions, reinforcing the robustness and conservative nature of the modeling strategy. The findings underscore the practical applicability and reliability of the CMC approach in large-scale geotechnical design scenarios involving extensive RI networks. The method offers a computationally efficient yet accurate alternative to fully discretized modeling techniques, particularly in cases demanding high-volume parametric analyses and performance-based design assessments.

The excavation method has significant effects on the response of piles, and post-grouting is a great way to improve the response of piles. In this research, field static load tests were performed on three large-diameter and superlong rock-socketed bored piles (LSRBPs) of superhigh-rise constructions. The effects of composite excavation and combined grouting on the response of LSRBPs were studied. The improved effects of combined grouting on LSRBPs that were drilled by composite excavation were discussed. The results indicate that the composite excavation improves construction efficiency but affects shaft-forming quality, thus lowering the bearing capacity of LSRBPs, while combined grouting can contain this defect. Despite reducing the original pile size, combined grouting still significantly improves the bearing capacity of LSRBS and reduces the dispersion of bearing capacity. Existing pile design methods overestimate the bearing capacity of LSRBPs constructed using composite excavation, but underestimate it after combined grouting. The composite excavation forms different pile-rock (soil) interfaces, which affects the effectiveness of combined grouting. The simultaneous application of composite excavation and combined grouting reduces design pile size and improves construction efficiency, thereby achieving the goals of cost reduction and low-carbon construction. The findings have significant implications for the construction and design of LSRBPs.

This paper aims to investigate the effect of combined end-and-side grouting on the bearing properties of large-diameter rock-socketed bored piles in highly weathered rock layers. Eight full-scale pile load tests were conducted in the highly weathered rock layer to analyze the enhanced mechanism of the combined grouted bored piles. The test data from pile mechanical testing were compared with the recommended values in the current specification and geological survey report. The results demonstrate significant improvement in the side and end resistances of the combined grouted bored piles, resulting in a substantial increase in the bearing capacity and effective settlement control. It was observed that the construction of impact holes for bored piles can cause severe damage to highly weathered rock structures and weaken the mobilization of side and end resistances. Moreover, it was found that the calculation of the enhancement coefficient in the current specification underestimates the practical bearing capacity. The measured enhancement coefficients for the side and end resistance of piles in fully or highly weathered rock layers range from 2.49 to 3.05 and 2.24 to 2.43, respectively, which are more reasonable and feasible for the calculation. The research findings deepen the understanding of the bearing characteristics of large-diameter rock-socketed bored piles with combined grouting and provide valuable case references for the optimal design of large-diameter combined grouted piles for building foundations in Shenzhen, China.HighlightsPost-grouting had the potential to improve super high-building foundation reliability while reducing pile length and cost.The improvement effect and improvement mechanism of combined grouted bored piles embedded in highly rock strata were revealed.The influence of the size effect for large-diameter piles in highly weathered rock was revealed.The construction of impact holes for bored piles can cause severe damage to highly weathered rock structures and weaken the mobilization of side and end resistances.The enhancement coefficients for the side and end resistance of piles in fully or highly weathered rock layers were proposed.

Field testing is the most relevant method for verifying pile foundation design calculations. The ultimate static load test allows the pile load to reach the maximum bearing capacity; however, the excessive cost of this method restricts its use. The theory presented in this paper is based on static load test results performed in a specifically designed chamber that closely resembles natural soil conditions and pile dimensions. This study utilizes the Meyer-Kowalow theory and previous author’s work on this topic to attain a streamlined design process and reduce costs without compromising safety and reliability. It was concluded that the relationship between the toe and skin of the pile remained constant, and this was depicted in graphs showing the results under field conditions. The author intends to verify this conclusion in future research, using more static load test results. The primary focus of this study was to develop a method for estimating pile-toe bearing capacities, which represents the most complex measurement method to solve. The previous author’s works focused on developing the calculus required to estimate the pile-skin bearing capacity, which was the first step in describing the pile-soil interaction. This study focused on verifying a mathematical model describing pile-toe behavior and calculations based on this model. This study provides practical equations for estimating pile-toe and skin resistance, which can improve the design process when using the proposed method.

A series of full-scale static loading tests on square footings supported by rigid inclusions was conducted as part of the French research project ASIRI+. The primary objective of these experiments was to evaluate the impact of a load transfer platform (LTP) between the shallow foundation and rigid inclusions on the performance of the footing and enhanced soil. To achieve this, various loading configurations were examined, including vertical loading with and without eccentricity, as well as horizontal loading, across different structural scenarios—shallow foundations on soil, shallow foundations on reinforced soil with or without a load transfer platform, and rigid inclusions. The comprehensive data obtained from these experiments contribute to a deeper understanding of the load transfer mechanisms in reinforced soil, elucidating the function of each component and facilitating the calibration of numerical models.

The current engineering practice has shown that post-grouting improves the vertical bearing capacity of bored piles. However, some engineers are concerned about the effectiveness of post-grouting in the context of extra-long bored piles. At present, the effect of pile tip post-grouting on the side resistance of these extra-long bored piles remains uncertain. This paper investigated the effects of post-grouting on the compressive and uplift responses of extra-long piles, drawing on case studies from seven field static load tests. It proposed a mechanism for pile tip post-grouting across various bearing layers to enhance the side resistance of extra-long piles by reinforcing the soil beneath the pile tip. Additionally, it outlined the effectiveness and limitations of post-grouting in improving the vertical response of extra-long piles situated in different bearing layers. The analytical results indicated that post-grouting at the pile tip improved the strength of the soil beneath the pile tip. This improvement not only decreased the settlement at the pile tip but also enhanced the side resistance of the pile, especially the side resistance near the pile tip. The effectiveness of pile-tip post grouting in improving pile side resistance is significantly and positively correlated with the reinforcing effect on the soil beneath the pile tip. The effectiveness of post-grouting on the vertical response of extra-long piles can be inconsistent under working loads. Therefore, it is crucial to improve the quality of post-grouting construction in these piles to enhance the overall effectiveness of post-grouting improvements.

This study proposes a work-based interpretation procedure, hereafter referred to as the IDEA method, for identifying the failure-related transition load in monotonic static load tests of pre-stressed high-strength concrete pipe piles. The method was examined using nine full-scale axial compression tests from a site in the lower reaches of the Yangtze River, China. Cumulative work was reconstructed from the measured load settlement curves, and an incremental work response indicator was fitted with a one-break continuous segmented-regression model. The breakpoint was taken as the IDEA estimate, while bootstrap confidence intervals and delta BIC were used to evaluate numerical stability and model support. For the present nine piles, IDEA showed close agreement with the code-interpreted reference loads and yielded the lowest MAPE among the five Q-s interpretation methods considered, whereas the Davisson method showed slightly lower COV and RMSE. Additional perturbation analyses indicated low sensitivity to moderate settlement noise but clear sensitivity to sparse loading records and missing pre-failure points. A preliminary external application to 10 published pile cases showed generally favorable agreement with reference loads reinterpreted from digitized external Q-s curves using a uniform abrupt-settlement criterion. Because the original settlement–time records of the external cases were unavailable, the external assessment is treated as a curve-based transferability check rather than a strictly code-certified validation.

The stability of foundation piles in the secondary terrace of the Wei River is of great significance for engineering construction in northwestern China. To investigate the bearing behavior of piles and the shear characteristics of the pile–soil interface, three cast-in-place piles were constructed at a representative site, with reinforcement stress meters installed in two of them. Static vertical compression tests were performed using a sparse-to-dense loading strategy, and comparative interface shear tests were carried out under controlled laboratory conditions. The results show that the pile side friction resistance accounts for the majority of the bearing capacity, while the contribution of end resistance is limited. The shear stress–displacement curves of the pile–soil interface can be classified into three types—strain-hardening, strain-softening, and ideal elastic–plastic—depending on soil properties and stress levels. These findings provide a clear classification of the support–deformation relationship and reveal the mechanisms governing load transfer in the secondary terrace deposits. The outcomes offer practical guidance for the design and optimization of pile foundations in alluvial terrace areas.

Piles are structural members made of steel, concrete, or wood installed into the ground to transfer superstructure loads to the soil. Nowadays, many structures are built on poor lands, and therefore piles have crucial roles in such structures. Performing in-situ tests such as cone penetration (CPT) and piezocone penetration tests (CPTu) have always been of great importance in designing piles. These tests have a brilliant consistency with reality, and as a result, the outcome data can be used in order to achieve reliable pile designing models and reduce uncertainty in this regard. In this paper, the capability of various CPT and CPTu based methods developed from 1961 to 2016 has been investigated using four statistical methods. Such CPT and CPTu based methods are adopted for direct prediction of axial bearing capacity of piles using CPT and CPTu field data. For this purpose, 61 sets of field data prepared from CPT and CPTu have been collected. The data sets were utilized in order to calculate the axial bearing capacity of piles (QE) through 25 different methods. In addition, the measured axial pile capacities (QM) have been collected, recorded and prepared from field static load tests, respectively. Then, four different statistical approaches have been applied to assess the accuracy of these methods. Finally, the most reliable and accurate methods are presented.