The existing correlations between pile and cone penetration test (CPT) results often lack versatility for silty geomaterials, as they were primarily developed for clays or sands. To establish ...meaningful correlations, it is essential to understand the geology of the environment under examination. The CPT and its derived parameters, including the Soil Behavior Type (SBT) index, have proven to provide reliable soil information, particularly in the field of pile foundation engineering. This paper presents the findings and interpretations from several pile load tests conducted alongside field cone penetration tests on a Holocene saline interlayered silty formation, a distinct condition encountered in practice. Various CPT-based pile design methods were employed to evaluate pile capacity based on CPT results. As observed, predictions for pile shaft resistance in this geological formation remained consistent across all methods, while notable variations emerged in estimating pile end bearing. This was inferred to be a result of limited research on pile end bearing capacity in the literature, leading to proposals of broad ranges for pile influence zone and toe coefficient values, as well as various CPT tip resistance averaging techniques across different methods. Consequently, to improve accuracy, modifications based on site-specific test data may be necessary. Drawing from the assessments, effective modifications involved considering the SBT index near the pile tip. Subsequently, the current study introduces a new region-specific adjustment to the widely recognized Enhanced Unicone method based on the SBT index, resulting in a more accurate estimate of pile end bearing in such interlayered silty contexts, with less scatter compared to other available approaches.
The object of this research is to compare the behavior of floating and end bearing stone columns made of recycled aggregates of building debris with natural aggregate. To do so, both types of stone ...columns were constructed by crushed concrete and crushed brick as recycled aggregates and compared with the same models made of gravel as natural aggregates. All the columns were constructed with the same size, density, and grading in a clay bed. To evaluate the initial quality of materials of the stone columns, the index tests were performed. The results of such tests illustrated the less resistance of recycled materials in comparison to the natural materials; On the contrary, according to the results of the index tests, crushed bricks are not recommended to construct stone columns. Despite the index tests, results of loading on a floating column filed with natural and recycled aggregate were approximately the same, but the bearing capacity of the end bearing column made of natural aggregates was higher than the same model made of recycled aggregates.
This paper presents a machine learning (ML)-based method for predicting the end-bearing capacity of rock-socketed shafts. For ML model training and testing, a database of 151 test shafts covering a ...wide range of rock types, shaft dimensions, and ground profiles has been developed from various sources. To properly take into account different factors, the rock property constant
m
i
, unconfined compressive strength of intact rock
σ
c
(MPa), geological strength index GSI, length of the shaft within the soil layer
H
s
(m), length of the shaft within the rock layer
H
r
(m), and shaft diameter
B
(m) were taken as the inputs and the ultimate bearing capacity factor
N
σ
, which is the ratio of ultimate end-bearing capacity to
σ
c
, was taken as the target output. Four commonly used ML algorithms, support vector machine (SVM), decision trees (DT), random forest (RF), and Gaussian process regression (GPR), were first utilized to train models, respectively. Then, the trained models with the four ML algorithms were fused together with an ensemble learning (EL) approach to further enhance the prediction accuracy. Comparisons with existing empirical equations show a much better performance of the ML-based method for predicting the end-bearing capacity of rock-socketed shafts. Parametric studies were also performed with the EL model to investigate the importance of the six input parameters and the results show that the most important parameter is
σ
c
, followed by
B
, GSI,
H
r
,
H
s
and
m
i
in the order of importance. For the convenient application of the ML-based method, a graphical user interface (GUI) app has been developed. Finally, two examples were analyzed to demonstrate the application of the GUI app with the implemented EL models. The results show that the GUI app can be used for quick and accurate prediction of the end-bearing capacity of rock-socketed shafts by considering the various parameters.
Highlights
Four machine learning algorithms are fused together with an ensemble learning approach to predict the ultimate bearing capacity of rock socketed shafts.
The proposed ensemble learning model outperforms other existing empirical methods.
For the convenient application of the ensemble learning-based method, a graphical user interface app has been developed.
The end load-settlement relationship of piles with asymmetric bottom expansion was investigated by centrifugal model tests and three-dimensional FEM simulation analysis. In the centrifugal model ...tests, the pile end load-settlement relationship was equivalent to symmetrically expanded piles, even under conditions where the pile shaft was located at the edge of the expanded bottom. Simulation analysis also showed that the vertical stress distributions under the expanded bottom surface were equivalent for symmetrically and asymmetrically expanded piles up to the ultimate bearing capacity, and that there was no significant difference in settlement, confirming the experimental results.
This study investigates the load transfer mechanism that includes the effect of helix bending deflection on end-bearing capacity, distribution of ground pressure under the helix and soil deformation ...around the screw pile. The helix to shaft diameter ratio of 2.5 and 2.8 with a strong helix and a weak helix were used. The model ground was prepared with fine sand at 80% of relative density. To investigate the load transfer mechanism, the experimental tests were modelled in a 3D finite element code. A good agreement between the experimental and numerical approaches was found. The numerical analyses showed that large influence zone exists under screw pile with strong helix, which resulted in higher mobilized soil shear strength that contributed to higher end-bearing capacity. In the case of strong helix, uniform pattern of pressure distribution was observed under the central shaft and the helix. Similar pattern of pressure distribution under the central shaft was observed in weak helix case but the pattern of pressure distribution under the helix changed from uniform to triangular to trapezoidal at various stages during the load test. The normalized end-bearing capacity decreased linearly with the increase in normalized helix bending deflection in both approaches, i.e. experimental and numerical.
As an efficient solution for deepwater moorings, gravity installed anchors (GIAs) have many attractive attributes and play a remarkable role in various deepwater applications. The end-bearing ...capacity factor offers an efficient method to evaluate GIA end bearing under complex conditions involving multiple factors. It can also assess total anchor bearing capacity. Based on numerous large deformation finite element (LDFE) analyses, two formulas have been developed to calculate the end-bearing capacity factors for GIAs in clay under quasi-static or dynamic conditions. Through rigorous statistical analysis, it is demonstrated that the formulas provide accurate predictions of the end-bearing capacity for various GIAs, particularly those with loading characteristics similar to OMNI-Max anchors, i.e., the padeye location and the loading angle. The contribution of the end bearing to the overall bearing capacity of GIAs is analyzed under various loading conditions. Furthermore, a comparative study proves that the formula accounting for the loading rate effect can be degenerated to evaluate the end-bearing capacity factor of the anchors under quasi-static conditions. The results provide a comprehensive understanding of the end bearing and offer an efficient solution for determining the total bearing capacity of various GIAs in clay under complex conditions. These findings contribute to the advancement of design and performance assessment of GIAs, enhancing their reliability and effectiveness in applications.
•Theoretical evaluation of the end-bearing capacity of GIAs in clay.•Formulas applicable to GIAs under quasi-static and dynamic conditions.•Definite conditions applied for various GIAs.•Knowledge of the contribution of end bearing to the total bearing capacity of GIAs.•Statistical analyses based on large amount of data from various GIAs.
Abstract
A similar theoretical approach is generally used to estimate the end-bearing capacity of straight and screw piles. However, under similar ground conditions (stress level and bearing-capacity ...factor) and pile tip area after the pile is installed, the end-bearing capacity of the screw pile is less than the straight pile. In this study, the experimental tests were modeled in a three-dimensional (3D) finite-element code to better understand the pressure distribution and mobilized shear strength under straight and screw piles embedded in similar ground conditions. Moreover, the effect of helix position on the pile bearing capacity and pressure beneath the helix and shaft of the screw pile was also investigated. A helix-to-shaft diameter ratio (Dh/DSS) of 2.8 was used. A good agreement between experimental and numerical results was found. The results indicated that the pressure distribution under the screw pile with a thick helix (non-deformed helix) and straight pile are similar when the helix is positioned (dh) at the pile tip (dh = 0). As the helix is moved further away from the pile tip (dh > 0), the pressure under the helix gradually decreases, while the pressure under the shaft increases and then decreases within a certain dh/Dh. The mobilized shear strength contribution of the helix decreased with the increase in helix position-to-helix diameter ratio (dh/Dh). Moreover, when dh/Dh ≥ 1.5, both central shaft and helix behaved independently, and their contribution in mobilized shear strength cannot be considered as a group. Regarding the effect of the helix position on the shaft pressure, when dh/Dh < 1.5, the ratio of screw pile to straight pile end-bearing capacity decreases almost linearly with the increase in dh/Dh. A modified equation is proposed that includes the two factors—helix position and shape (helix which differentiates screw pile shape from the straight pile)—to estimate the end-bearing capacity of the strong helix screw pile.
AbstractThe objective of this study is to investigate the effects of an inclined base plate on the end bearing capacity of embedded piles and soil behavior below a pile base according to the vertical ...stress and inclination angle of the base plate. Two types of model piles were prepared: a conventional pile with a flat base plate with a diameter of 50 mm and piles with an inclined base plate with a diameter of 56 mm. Load tests were conducted using model piles with a diameter of 50 mm incorporated with load cells and bender elements in a calibration chamber. The end bearing capacity, unit end bearing capacity, and shear wave velocity increase for all model piles with an increase in the vertical stress and in the inclination angle. The increment in the end bearing capacity may result from the increased projected area, the increased contact area between the inclined base plate and soil, and increased horizontal effective stress. The unit end bearing capacity also demonstrates a good relationship with the shear wave velocity, which is a function of the horizontal effective stress below the pile base. This study suggests that piles with inclined base plates may be effectively used in the embedded pile method to improve the end bearing capacity.
Abstract
This study proposed an analytical approach for predicting the end-bearing capacity of driven piles that are subjected to axial loads in saturated and unsaturated soils. This is a generalized ...approach in which the stress characteristic method is employed successfully for both saturated and unsaturated soils. An iterative technique computer code was developed for the proposed analytical approach extending the finite difference method to develop solutions with the aid of MATLAB (version 2019a) that provides graphical output to visualize the results. The results from the proposed approach were compared against measurements for 13 pile load tests that include 11 in saturated soils and 2 in unsaturated soils, with good agreement. In addition, numerical analyses were performed using ABAQUS (version 6.14) to simulate the driven pile penetration and pile loading by employing the arbitrary Lagrangian–Eulerian adaptive mesh methods. The comparisons between the numerical predictions and measurements from a published model pile test suggested that the ultimate bearing capacity is well predicted by the finite-element model in comparison to the proposed analytical method. However, the proposed analytical method was simple for use in engineering practice applications to estimate the end-bearing capacity of pile foundations in both saturated and unsaturated soils.
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