Regular Pile Research Articles

Pullout Response of the Pre-displacement Bladed Anchor in Cohesionless Soil

This study presents a new alternative technique, the pre-displacement pile, which aims to improve the uplift capacity of the regular pile. This modified pile intends to offer a bearing area underneath the sand during uplift using the blades. This method does not hinder the piles from being driven or penetrated the ground. An experimental study was conducted to investigate the uplift response of the modified anchor. The influence of the number of blades, the loading rate, and the relative density of the sand on the uplift capacity of the anchor pile with blades is studied. The ultimate pullout response of the pre-displacement anchor implanted in sand improves with an increase in blade number and loading rate. The percentage improvement in the pullout load for the anchor with four blades and a loading rate of 1 mm/s was (301%, 289%, and 249%) at sand relative densities of (30%, 50%, and 80%), respectively, compared to the unbladed pile. The existence of blades led to the creation of an ideal anchoring system. This piling modification is practical, suitable for marine projects, and easy to install for offshore applications.

Utilization of blade anchor for improving the uplift capacity of pile in sand: Model Study

This research introduces an alternative recent technique, bladed pile anchor, which aims to increase the surface area under the soil during uplift. This provides more shear resistance acting along the failure surface and increases the dead weight of the surrounding sand within the failure zone to resist the uplift force. As a result, the uplift capacities are increased. In this experimental study, the effect of many parameters, such as blade length ratio, blade width ratio, and sand relative density, on the ultimate uplift capacity of bladed pile anchors is investigated. The uplift capacities of bladed pile anchors embedded in sand increase with the increase of the blade surface area by increasing the blade length ratio and the blade width ratio. At blade length ratio of 3 and blade width ratio of π/2, the percentage increase in the uplift capacity reaches (275%, 233%, and 230%) at relative densities of (30%, 50%, and 80%), respectively, compared with regular pile. The existence of blades created an ideal anchorage system due to the increased surface area beneath the soil, resulting in increased uplift capacity. This pile modification is valid and suitable for marine structures, and it is easy to install for this application.

Effect on bearing capacity and settlement behaviour of fly-ash reinforced with fine micropiles

ABSTRACT Micropiling is an extensively used method for improving the stability of building foundations and load-carrying capacity of the soil. Unlike regular piling, it can be employed without pile driving equipment and, hence, it is a versatile option of soil reinforcement under space-restricted situations. Since, it is an economical and easy to implement option for soil improvement, this paper intends to study the improvement in bearing capacity and settlement behaviour of a fly-ash bed using fine micropiles under isolated footings, for low-cast and lightweight structures. Fly-ash, a by-product of coal-fired power plants, is used in the experiment because it is extensively used as a filling material for housing projects in low-lying areas and pavements. Micropiles were installed underneath the footing as well as beyond the periphery of footing with varied spacing and extent ratio. The results are depicted through two dimensionless constants, namely bearing capacity ratio (BCR) and settlement reduction factor (SRF). Significant improvements have been observed in load-carrying capacity and settlement potential due to decrease in spacing and increase in lateral extent of micropiles. The optimum configuration of spacing and lateral extend achieved 135% bearing capacity improvement with 71% decrease in settlement.

An Experimental Study on Laterally Loaded Winged Pile in Sandy Soil

Many offshore facilities such as offshore wind turbines and other engineering structures, including floating offshore facilities (FPSOs), are founded on or anchored with piles to transfer large horizontal loads relative to the imposed vertical load compared to onshore installations. The subgrade reaction of the soil surrounding the pile shaft mobilized when the lateral loading is applying on the pile to resist the applied loads. Since the soil at the midline is often weak and tends to have a poor subgrade reaction, resulting in large pile displacements near ground level. The lateral bearing capacity of pile foundations can be increased, and pile displacements near ground level can be decreased by expanding the piles’ cross-sectional area near the seabed level to compensate for the lower soil stiffness in the seabed level. One method of expanding the pile area in the lower soil stiffness zone is the addition of wings (or fins) near the seabed level. This paper presents a series of laboratory small-scale model tests that were conducted to laterally loaded piles with/without wings in sandy soil with different densities. The Piles slenderness’s ratio (L/D) is varied from 4, 6, 8, and 10 to simulate the behavior of both flexible and rigid pile designs, with different wings geometry and numbers. This study indicated that the lateral pile capacity increased, and the horizontal deformation of the pile decreased after mounting wings compared to the regular normal pile without wings. It has been found that the optimum geometry and number of adopted wings is found to be three wings, and its length equals (0.22) of the embedded pile length. The existence of wings improved the bearing capacity of the winged pile by 1.33, 1.18, and 1.16 for piles of L/D=10 in the case of loose, medium, and dense soils, respectively, compared to regular piles in the same condition.

Effect of kinematic interaction on seismic response of offshore wind turbines on monopiles

AbstractInterest in renewable energy over the past decade has motivated a remarkable research on offshore wind energy. Due to the environmental loading conditions in the early developments of offshore wind farms, the focus of the research and engineering has been on aerodynamic and hydrodynamic subjects. However, earthquake has turned out to be a major design concern in seismic areas such as East Asia, Southern Europe, and United States. The topics include, among others, nonlinear response of foundations, soil liquefaction, and their impacts on foundation performance. An important topic in seismic soil‐structure interaction (SSI) analysis is the kinematic seismic response of foundations. This information is crucial for analyses based on the substructuring approach where both kinematic response and foundation impedances are key parameters. While considerable research has been spent on the latter topic, very little has been reported on the kinematic interaction. Large monopoles with low aspect ratios tend to rotate much more than regular piles in pile group foundations due to seismic waves. The rotation leads to additional load on the tower and the turbine. This article uses a rigorous numerical model for monopole‐soil interaction in layered soil and computes both rotational and horizontal responses at the pile head (seabed) as functions of frequency. A suite of generic homogeneous and heterogeneous soil profiles with shear moduli representative of clay (generally linear) and sand (generally parabolic) are considered in these analyses. Through representative analyses, both in frequency domain and time domain, it is illustrated how the kinematic interaction influences the earthquake loads imparted to an offshore wind turbine (OWT).

Model study of single pile with wings under uplift loads

Several structures as in the case of offshore structures like jetty, flood wall and wind turbines are mostly subjected to uplift loads. Thereby, the safe design for such cases is using piles. In this research a novel recent technique is adopted to improve the uplift capacity of the pile. In this paper, the uplift capacities of single regular piles (without wings) and anchor winged vertical piles installed in dry sand with different densities are investigated. A total number of sixty experimental model single regular and anchor winged piles tests were performed. Model test series were performed at a fixed embedment depth, and pile diameter. The effect of wings which were designed at the tip of the pile at different values of length and diameter was studied. The test results demonstrated that the uplift capacity of anchor winged piles increases with the increase of sand relative densities. At the ratio of wing length to pile length (Lw/Lp) = 0.50 and at the ratio of the maximum diameter between the outer edges of the wing to pile diameter (Dw/Dp) = 3.0 the efficiency of improvement in the uplift capacity reached to 2.0, 2.38 and 2.77 times of regular piles without wings at sand relative densities of 30 %, 50 % and 80 % respectively. The presence of such wings at the tip of the mono-pile provided an ideal anchorage system because of the significant locking-up influence of the wings within the soils, ensuing improved uplift capacity and reduced the pile movement. The existence of such wings can significantly increase the earth pressure and skin friction around the pile shaft in the form of (K) and (Fs) respectively.

Numerical finite element analysis of laterally loaded fin pile in sandy soil

In the present study, the behavior of fin pile under lateral loading was investigated by ABAQUS software. First, the generated model was verified against an available experimental small-scale test in the literature. Having conducted verification, a study was carried out on the fin pile dimensions under lateral loading. Different parameters, such as pile diameter, fin’s length, and width, were studied. Moreover, a study on the fin’s aspect ratio by setting fin’s area constant was conducted, and then, optimum fin’s ratio was obtained. The results indicated that both fin’s length and width could improve pile efficiency under lateral loading, yet fin’s length had a more critical impact, and provided high lateral resistance and less usage of material. The analysis on the optimum fin’s dimension indicated that fin pile with 40 mm diameter provided 29% more lateral load capacity than regular pile with 40 mm diameter. Although the optimum fin pile with 40 mm diameter provided lateral load capacity equal to the regular pile with 50 mm diameter, the fin pile decreased material usage around 16%. Likewise, optimum fin pile with 50 mm diameter provided 27.6% more lateral load capacity than regular pile with 50 mm diameter. Even though fin pile with 50 mm diameter provided lateral load capacity equal to the regular pile with 60 mm diameter, the fin pile decreased material usage around 10.8%. The analysis on the fin piles showed that fin piles with 40 mm and 50 mm diameter provided 29% and 27.6%, respectively, more lateral load capacity than regular ones. Although the optimum fin pile with 40 mm diameter provided lateral load capacity equal to the regular pile with 50 mm diameter, the fin pile decreased material usage around 16%. Likewise, fin pile with 50 mm diameter provided lateral load capacity equal to the regular pile with 60 mm diameter; the fin pile decreased material usage around 10.8%. Finally, based on the study on different fin’s dimensions an empirical equation according to the statistical method was suggested that could be used as a practical tool.

Numerical studies on lateral load response of fin piles

ABSTRACTIn the recent past, in order to cater lateral loads, provision of fins to monopiles is evolving as an option for enhancing their lateral load capacity. Numerical and experimental studies pertaining to fin piles subjected to lateral loading are very limited. It is very difficult to understand the behaviour of fin piles through conventional soil pile theories, due to their different fin configurations. In the present study, three-dimensional finite element analyses were performed on regular piles (pile without fins) as well as fin piles. For fin piles, different fin lengths, orientation and position were considered during the analyses. The results have shown that fins placed at the top portion of the piles are more effective than fins placed at bottom of the pile. In all cases, fin piles exhibited more lateral load-carrying capacity compared to regular piles. When fin’s length is less than half of the pile length, lateral load-carrying capacity of fin piles is same irrespective of their orientation. However, fin’s orientation is significant, when fin length is more than 0.5 times length of piles, star fin piles exhibit more lateral load-carrying capacity compared to diagonal and straight fin piles. Fin piles experienced less bending moment compared to regular piles for a given lateral load. Further, it was also noticed that lateral load-carrying capacity of the fin piles depend upon fins’ length and their orientation.

An experimental study and numerical modeling of laterally loaded regular and finned pile foundations in sandy soils

A significant objective in the design and implementation of capable and cost-effective pile foundations is the enhancement of their lateral capacity when lateral load is applied. This study offers a nonlinear 3D analysis of pile-soil interaction. The ways that piles behave are examined in this research, with a sequence of laboratory model tests conducted to develop p-y curves of laterally loaded finned and regular piles in multilayered sandy soil from Karbala city in Iraq. To clarify the effects of group interaction, pile type, pile group patterns, and spacing ratios were analyzed, and from the investigational tests, p-multipliers values were identified.

Scale effect in centrifuge tests of helical anchors in sand

Centrifuge modelling is an advantageous technique to simulate the behaviour of helical anchors in sand. The uplift capacity of a single-helix anchor is the sum of the helix bearing resistance plus the shaft resistance; therefore, recommendations to avoid the grain-size effect of previous model tests on plate anchors and on regular piles appear to be reasonable for helical anchor model tests. However, there are two important differences between centrifuge models of plate anchors and helical anchors: the ratio of the helical plate to the shaft diameter and the plate installation procedure. Consequently, the shaft friction and the plate bearing resistance of helical anchors can be affected by the scaling effect in a different manner. To clarify this uncertainty, this study was proposed to investigate the grain-size effect on the results of uplift capacity of helical anchor models in sand. Anchor models with different scales were tested to simulate the same prototype in very dense dry sand in a centrifuge. These experiments have shown that no scale effect was found for models with the ratio of the effective helical radius to the average grain size >58. The findings obtained here could guide future centrifuge model studies on helical anchors.

Numerical Modeling of Dust Lifting from a Complex-Geometry Industrial Stockpile

This paper investigates the dust lifting phenomenon at the coal and iron ore stockpile at the Port of Koper, Slovenia. Dust lifting presents a serious environment and health hazard, thus the main objective of our study was to propose efficient measures for wind erosion reduction. A numerical model of the stockpile was created using the computational fluid dynamics (CFD) software. Wind velocity fields above the piles were calculated for the current stockpile layout and for several modified cases with rearranged piles and added porous barriers. Results from numerical modelling were used in the USEPA model to determine dust emission factors. Comparison of selected cases shows a positive, although limited effect of porous fences and barriers on reduction of local velocities and consequently, dust erosion rate. On the other hand, pile rearrangement has little effect and may not be practical for implementation. Realistic stockpile geometry with adjacent structures has shown to cause wind velocity distributions, which are not consistent with the most studied cases of regular pile shapes and layouts. The angle of incoming wind is a key factor influencing effectiveness of both solid and porous windbarriers. The proposed placement of porous barriers between the piles has shown to be effective in reducing wind exposure and dust emission. To maintain the dust emissions at an acceptably low level, other measures such as spraying with water and crust-forming liquids may still be necessary at higher wind velocities.

Experimental and theoretical studies of laterally loaded finned piles in sand

Large lateral loads may act on pile foundation supporting structures, such as bridge abutments, retaining walls, and structures subjected to wind–earthquake loads. A pile with fins is a newly developed type of pile foundation that is capable of supporting large lateral loads. In the present study an attempt is made to evaluate the improvement in lateral capacity of a pile with fins mounted close to the pile head. Small-scale model tests and a numerical study using finite element analysis were performed on regular piles without (fins) and piles with fins. These piles were installed in sand of different relative densities (Dr= 35% and 78%). The investigations were carried out by varying the length, width, and shape of the fins, and type of pile. Results reveal that there is a significant increase in lateral resistance of the piles after mounting the fins close to the pile head. The increase in lateral resistance gained by placing fins on a pile varies with geometries of the pile and fins. The lateral resistance increases with the increase in length of the fins until the fin’s length is equal to 0.4 of the pile length. Based on the results of the laboratory model and numerical analysis, critical values of fin parameters for maximum improvement are suggested. The agreement between observed and computed results is found to be reasonably good in terms of ultimate lateral load and fin efficiency. A comparison between the model results and the prototype-scale results is also studied.

Discrete element simulations of dense packings and heaps made of spherical and non-spherical particles

The discrete element method (DEM) in the simulation of static packings allows one to investigate the behavior of granular materials by modeling the forces on the particle level. No macroscopic parameters like the angle of repose enter the simulation, but they can be extracted as a result of the particle properties like friction, roughness or shape. One of the issues of static packings recently discussed is the stress distribution under granular heaps. This problem is used to highlight the possibilities of modeling at the particle level using DEM. Phenomena like arching or stress-chains are observed even for spherical particles in a regular pile in the absence of friction if the bottom is rough. The situation does not change much if polygonal, frictional particles are used without disturbing the regular piling. For more realistic situations, when the pile is built by pouring grains from above, the packing and the stresses are influenced by the creation history. The more eccentric the polygons are, the more pronounced a dip is observed in the vertical stress under the apex of the sand-pile.

Semi-flexible liquid crystalline polyesters based on twin di(p-oxybenzoyl) units X-ray study on smectic mesophase structures

Abstract An X-ray study is performed of oriented smectic mesophases of several polyesters consisting of two p-oxybenzoyl diads interconnected by a pentamethylene segment and a polymethylene segment of variable length. The X-ray diffraction patterns are very similar for all the samples and are constituted by one or more inner reflections, lying on the meridional line, and by two broad outer haloes split into two intense portions symmetrically placed above and below the equatorial line. The former reflections are attributed to the regular piling of the smectic layers; the latter are associated with the presence of rigid mesogenic groups that are tilted with respect to the layer normal, while the average chain axis lies perpendicular to the layer planes. Accordingly, the analysed smectic mesophases can be classified as unconventional smectic C. A structural model is proposed to account for the intensity profile of the X-ray patterns.

Cytological studies on mammary fibroadenoma

The cell pattern of fibroadenoma was observed by aspiration and operation smears obtained from 13 cases.All these were diagnosed histologically as fibroadenhma.The preparations were stained by M-G-G method.Usually, each cell from fibroadenoma case was round or oval in shape and small in size.It was rare to find nuclei over 20μ.Regular piling of cells was commonly found in these cases.Sometimes, the smears of fibroadenoma with remarkable epithelial proliferation had abundant cell materials and mild loose cohesion similar to the smears of cancer cases.Large and variable size of nuclei, irregular piling of cells, fusion of cell border and cell inclusion were common observations in cancer cases. But these findings were scarcely observed in fibroadenoma cases.