This study introduces a unified cylindrical and spherical cavity reverse expansion model to simulate the formation of compaction grouting bodies and grout diffusion along pile shafts. Stress field expression employs the superposition method, while displacement field analysis utilizes the nonassociated Mohr-Coulomb criterion. By combining the displacement expression for cylindrical cavity reverse expansion with the fluid flow equation, a calculation method is proposed to compute the upward and downward diffusion heights of grout, considering the unloading effect. The parameter analysis demonstrates that ultimate grouting pressure increases with increasing soil strength and grouting depth, with the ultimate grouting pressure at the pile tip being greater than that at the pile side. The value of grout diffusion height is negatively correlated with unloading ratio and grouting depth while positively correlated with grouting pressure and pile diameter. The deeper the grouting depth, the greater the impact of unloading on grout diffusion height. Three case studies validate the effectiveness of the proposed model. Analysis reveals that when grouting pressure exceeds the ultimate pressure, the size of the grout body is related to the grouting volume. Neglecting the unloading effect in the prediction of grout diffusion height for pile foundations would lead to conservative results.

In this study, six rock-socketed bored piles were tested in the field to investigate the bearing characteristics of rock-socketed bored piles in silty clay formations in coastal areas, and the model piles were simulated and optimized using the finite element (FE) method. The results showed that the lateral resistance of the piles in the clay layer is less than 50 kPa, and the lateral resistance of the rock-embedded portion is within 136.2-166.4 kPa. Compared with increasing the rock-embedded depth, increasing the diameter of the test piles can improve their vertical bearing capacity more effectively. The average horizontal critical load (Hcr) increased by 84.54 %, and the average horizontal ultimate load (Hu) increased by 50.3 % for the 800 mm diameter piles compared to the 600 mm diameter piles. Also, at the end of the test, the 600 mm diameter test piles showed severe damage at 6-9.5 D below the mud surface and were more susceptible to instability damage than the 800 mm diameter test piles. In soft clay strata, the 'm' values converged rapidly with increasing horizontal displacement and stabilized when the displacement exceeded 10 mm. The FE simulations confirmed that the horizontal displacement of the pile mainly occurs at 4 m depth below the mud surface, and the displacement of the test pile can be effectively reduced by reinforcing the soil around the pile. The silt at the bottom of the pile is one of the critical factors causing the uneven settlement of the test pile, severely affecting the vertical bearing capacity of the pile foundation.

The unclear impact of small-spacing construction between new road piles and railway piers in China's coastal soft soils can threaten the safety of operating high-speed railways. By field monitoring and numerical simulation tests, this study examines the deformation characteristics of railway piers and the surrounding stratum due to adjacent pile construction in soft soils. The stratum-lateral deformation (SLD) and the displacement of the bridge pier group with various pile-forming processes or pile construction schemes were measured in field monitoring. Furthermore, the intricate interplay between varying pile diameters and spacing was examined using comprehensive numerical methodology. On this basis, a comprehensive evaluation model for the Construction Deformation Comprehensive Index (CDCI) was established to compare the multi-stage combined effects of pile construction. The results indicate that the bored pile drilling and concreting procedures significantly affect the deformations of the stratum and pier. Specifically, a negative correlation is observed between stratum deformation and the bored pile's distance and depth. The most significant deformation is in the depth direction within the three-direction pier profile. The displacement amplitude caused by single-pile construction surpasses about 2-3 times that of non-construction. Additionally, the CDCI could provide valuable insights for evaluating the holistic impacts on stratum and pier deformation in similar pile construction projects.

This study employs variance-based and parametric analyses to quantify the impact of geometric and mechanical properties on the performance of pile foundations under axial tensile (Pa) and lateral (PL) loading. Utilizing 3D finite element analysis with the Drucker-Prager model, the research investigates pile-pile cap interaction across varying soil moduli (Es = 5, 20, & 50 MPa) and length-to-diameter (L/D) ratios (10, 20, & 33). The sensitivity analysis identifies the friction coefficient between sand and pile, as well as pile diameter, as the most influential factors, followed by pile length and the Young's modulus of both the pile and the sand. Parametric analysis reveals that pile deformation, contact pressure (Pc), and shear stresses (fs) are strongly affected by Es and the L/D ratio. Under Pa loading, as Es and L/D decrease, fs increases up to a certain depth before decreasing. Additionally, the normalized Pa to axial deformation ratio (Pa/delta a) decreases with increasing relative stiffness of the pile to soil (Ep/Es), with L/D becoming increasingly influential as Ep/Es decreases. Under PL loading, increased L/D and Es result in greater pile flexibility and a concentration of Pc at the top. The pile's lateral deformation behavior with depth mirrors the Pc distribution.

This paper presents an analysis of long, large-diameter bored piles' behavior under static and dynamic load tests for a megaproject located in El Alamein, on the northern shoreline of Egypt. Site investigations depict an abundance of limestone fragments and weak argillaceous limestone interlaid with gravelly, silty sands and silty, gravelly clay layers. These layers are classified as intermediate geomaterials, IGMs, and soil layers. The project consists of high-rise buildings founded on long bored piles of 1200 mm and 800 mm in diameter. Forty-four (44) static and dynamic compression load tests were performed in this study. During the pile testing, it was recognized that the pile load-settlement behavior is very conservative. Settlement did not exceed 1.6% of the pile diameter at twice the design load. This indicates that the available design manual does not provide reasonable parameters for IGM layers. The study was performed to investigate the efficiency of different approaches for determining the design load of bored piles in IGMs. These approaches are statistical, predictions from static pile load tests, numerical, and dynamic wave analysis via a case pile wave analysis program, CAPWAP, a method that calculates friction stresses along the pile shaft. The predicted ultimate capacities range from 5.5 to 10.0 times the pile design capacity. Settlement analysis indicates that the large-diameter pile behaves as a friction pile. The dynamic pile load test results were calibrated relative to the static pile load test. The dynamic load test could be used to validate the pile capacity. Settlement from the dynamic load test has been shown to be about 25% higher than that from the static load test. This can be attributed to the possible development of high pore water pressure in cohesive IGMs. The case study analysis and the parametric study indicate that AASHTO LRFD is conservative in estimating skin friction, tip, and load test resistance factors in IGMs. A new load-settlement response equation for 600 mm to 2000 mm diameter piles and new recommendations for resistance factors phi qp, phi qs, and phi load were proposed to be 0.65, 0.70, and 0.80, respectively.

The accurate prediction of grouting upward diffusion height is crucial for estimating the bearing capacity of tipgrouted piles. Borehole construction during the installation of bored piles induces soil unloading, resulting in both radial stress loss in the surrounding soil and an impact on grouting fluid diffusion. In this study, a modified model is developed for predicting grout diffusion height. This model incorporates the classical rheological equation of power-law cement grout and the cavity reverse expansion model to account for different degrees of unloading. A series of single-pile tip grouting and static load tests are conducted with varying initial grouting pressures. The test results demonstrate a significant effect of vertical grout diffusion on improving pile lateral friction resistance and bearing capacity. Increasing the grouting pressure leads to an increase in the vertical height of the grout. A comparison between the predicted values using the proposed model and the actual measured results reveals a model error ranging from -12.3% to 8.0%. Parametric analysis shows that grout diffusion height increases with an increase in the degree of unloading, with a more pronounced effect observed at higher grouting pressures. Two case studies are presented to verify the applicability of the proposed model. Field measurements of grout diffusion height correspond to unloading ratios of 0.68 and 0.71, respectively, as predicted by the model. Neglecting the unloading effect would result in a conservative estimate.

Large-diameter bored piles can safely transmit loads from structures by skin friction to the surrounding soil strata and end bearing at the bedrock layer, thereby providing a high compressive capacity. High-Strain Dynamic Testing (HSDT) provides a unique alternative technique to traditional Static Load Testing (SLT) for determining the static compressive resistance of the bored piles, considering its quicker performance and significant cost reductions. This article's main objective is to numerically explore the performance of large-diameter bored piles during the HSDT and to understand their dynamic behavior under an axial compressive impact force. This research is based on testing pile foundations for reinforced concrete mixed-use towers in the coastal zone of New Alamein City, Egypt. The tested pile is a 1.20 m diameter bored pile. Numerical modeling is performed to simulate both the HSDT and the SLT for two piles at the same site. Non-linear axisymmetric finite element modeling is employed to validate both test records and develop some sort of matching between the two tests. As lumped models, the developed numerical models use the signal-matching process, which is conducted by varying and adopting the strength parameters and deformation characteristics of the ground or soil deposit and the soil-pile interface. The predicted load-displacement curves, developed from analyzing dynamic records employing the Modified Unloading Point (MUP) method, are consistent with the field records. The verified non-linear models are utilized to accomplish a comparative parametric analysis to better understand the drop-mass system aspects. The analysis results emphasize the significance of employing adequate impact energy (i.e., dropping height and mass) to move the pile top to a sufficient extent to mobilize its full resistance. However, a longer impact duration, i.e., larger mass, is more effective for achieving a deeper high-strain wave. The impact load should be developed by a larger drop mass with a lower drop height, not a smaller drop mass with a higher drop height. The results also indicate that, for relatively longer piles, the skin friction of the upper layers surrounding the pile shaft is fully mobilized, whereas the skin resistance of the lower layers is not fully mobilized, regarding the stress wave phenomenon effect. Finally, this study's findings can be employed to develop guidelines and design procedures for the HSDT to be effectively performed on bored piles.

This paper reports numerical simulation and field test research on the horizontal static and cyclic loading performance of a single pile reinforced by cement-soil. 3D numerical models of soil-cement soil-concrete pile with various reinforcement sizes were established in ABAQUS. By comparing the effects of different cement-soil reinforcement widths and depths on bearing capacity and bending moments, a reinforcement width of 3 times of the pile diameter and a reinforcement depth of 1/4 of embedded depth are the optimal design parameters. On this basis, unidirectional and bidirectional cyclic loading tests were conducted on reinforced and unreinforced piles with a length of 40 m and a diameter of 1.6 m, respectively. The test results indicate that the critical horizontal load of reinforced pile increased by 40%, and the peak bending moment decreased by approximately 14.5% compared to unreinforced pile. This enhancement is attributed to the cement-soil around the pile, which increases the soil resistance and limits the horizontal displacement of the pile head. The cyclic hysteresis curve of reinforced piles is fuller than that of unreinforced piles, exhibiting a larger hysteresis area and a 74.5% increase in the initial stiffness of the pile head. Additionally, the cement-soil surrounding the pile mitigates the effects of cyclic weakening and plastic accumulation under cyclic loading.

Rotary penetration test is a newly developed in-situ testing technology in recent years, which combines the advantages of large drilling depth and continuous, intuitive, good repeatability, fast testing speed, and economy of cone penetration testing data. It uses static pressure and rotational torque to penetrate the soil stratum at a constant speed by standard conical double helix probe, recording the penetration resistance of the probe during the process of uniform penetration, the resistance torque, and water pressure during the process of soil damage. It is a new in-situ testing method for testing and studying the physical and mechanical properties of soil stratum. Through the analysis of mechanism and a large number of field tests, the results of the rotary penetration test (RPT) were analyzed by comparing with data of cone penetration test (CPT), drilling test, field pile test, and others; the characteristic indexes of rotary penetration as well as a series of analysis method and empirical formula were proposed, i.e. how the rotary penetration test results were applied to classify the strata, judge the soil category, determine the basic bearing capacity of the ground and the ultimate bearing capacity of the concrete bored pile. The research results were of great significance to enrich the in situ test method and promote the application and popularization of the rotary penetration technology.

Liquefaction can lead to structural failure as it reduces the bearing capacity of building foundations. This phenomenon occurs in saturated sandy soils where pore water pressure increases, significantly decreasing effective soil stress. Evaluating the axial and lateral bearing capacity of bored piles affected by liquefaction is crucial to ensure the stability and performance of foundation systems. This study focuses on assessing the capabilities of bored piles in the Governor's Office of Sulawesi Barat Province, which are influenced by liquefaction phenomena. The empirical approach applied the O'Neill and Reese 1989 method, while the numerical approach used RS Pile. The calculation results revealed decreased axial bearing capacity under liquefaction conditions. In non-liquefaction, PC. 4 can withstand up to 24946 kN, with displacements of 0.94 cm (x), 0.39 cm (y), and 1.12 cm in settlement. In liquefaction, it decreases to 2876.78 kN, with displacements of 1.32 cm (x), 0.86 cm (y), and 1.68 cm in settlement. In non-liquefaction, PC.3 can withstand up to 17407.93 kN with displacements of 0.02 cm (x), 0.04 cm (y), and 0.06 cm in settlement. In liquefaction, it decreases to 1713.05 kN, with displacements of 0.02 cm (x), 0.05 cm (y), and 0.07 cm in settlement.