Triangular Pile Research Articles

Load Transfer in Geosynthetic-Reinforced Piled Embankments with a Triangular Arrangement of Piles

A geosynthetic-reinforced piled embankment situated along a newly constructed high-speed rail line was fully instrumented and monitored to explore soil arching in an equilateral-triangular arrangement of piles with circular cap configuration. During construction, the settlement and vertical stress on the pile caps and subsurface at ground level and the tensile strain in the geogrid were recorded. A modified analytical arching model is derived from the established concentric arches (CA) model to elucidate the load transfer mechanism, specifically for a triangular array of piles. The general framework assumes that the embankment load, not resting on the subsurface beneath the arches, is transferred outward along the arches and distributed uniformly over the improved ground. Compared to the conventional CA model, the proposed model gives a lower proportion of load carried by piles, more in line with field measurements. Given the friction and adhesion between soil and geosynthetics, a novel quartic equation is applied to characterize the tensioned membrane effect of geosynthetic reinforcement based on Pham’s circular and parabolic models. The stiffness variation of the biaxial geogrid was critically assessed for the triangular pile arrangement, and its implications for the design were revealed. Finally, the pile efficacy and critical arch height were determined from different analytical methods and checked against field observations, demonstrating the potential of the proposed model.

Uplift Load Carrying Capacity of Cylindrical and Belled Pile in Cohesive soil Bed

Foundation of some structures like transmission towers, mooring systems for ocean surface or submerged platforms, tall chimneys, jetty structures etc. are subjected to uplift loads. Literature reflects that scholars have conducted pull out field prototype and model test and failure pattern of soil is studied for belled piles in loess soil and cohesionless soil. In this research work, the authors have carried out 36 tests on single pile and pile groups and uplift load carrying capacity is obtained by experimental investigation of single pile, triangular pattern (2x1) and square pattern (2x2) using the model piles of cylindrical and belled shaped in cohesive soil of soft consistency. The piles are having 20 mm shaft diameter and varying L/d ratio of 6, 8,10,15,18 and 20 for both cylindrical pile and belled pile. Belled portion is cast in belled pile with an angle of 70° with horizontal and having base diameter of 60 mm and height 55 mm. Spacing between two piles in various pile group was kept three times the piles shaft diameter (3d) in all experiments. Based on the experimental results as the L/d ratio increases uplift load carrying capacity increases. Uplift load carrying capacity of single pile, triangular pile group and square pile group of belled pile is 410%, 280% and 240% more than cylindrical piles. Uplift load carrying capacity of triangular pile group and square pile group increases by 182% and 273% for cylindrical pile and 104% and 141% for belled pile in comparison with single pile. Failure pattern of soil is obtained from experiments performed on belled pile and by using this failure pattern, theoretical uplift load carrying of belled pile is obtained.Uplift load carrying capacity.

Monitoring of an instrumented geosynthetic-reinforced piled embankment with a triangular pile configuration

ABSTRACT A comprehensive monitoring programme was undertaken at a geosynthetic-reinforced piled embankment over soft ground to better understand its time-dependent performance. The programme involved continuous monitoring of earth pressure, axial force in piles, settlement of structural elements, lateral movement of subsoil, and geogrid tensile strain of the instrumented system. Earth pressure measurements evidenced the mobilization of soil arching; pile efficacies were derived from established analytical methods and assessed against observed data for piles with circular cap configuration arranged in a triangular pattern, with the Concentric Arches model giving the best predictions. The development of axial load in piles can be properly captured by a regression equation with analytical approach. Penetration and compression behaviours of structural elements were evaluated by settlement measurement on piles and soils at ground level relative to pile toe or substratum. The proposed approach in obtaining tensile force of geogrid was verified with the measured differential-settlement data.

Evaluating the Design Criteria for Light Embankment Piling: Timber Piles in Road and Railway Foundations

Three-dimensional finite element (FE) simulations were performed to further develop the Swedish design guidelines for geogrid-reinforced timber pile-supported embankments, also known as lightly piled embankments. Lightly piled embankments are constructed mainly in areas which typically have highly compressible soils, and the method utilises untreated timber piles as its key feature. The timber piles are installed in a triangular arrangement instead of the more common square arrangement, with a centre-to-centre distance of 0.8–1.2 m. The aim of this study was to evaluate the current standard using FE modelling setups with square and triangular pile arrangements with varying centre-to-centre distances, based on a typical road foundation case. The evaluation mainly focused on comparing the embankment settlements, as well as the load and stress distribution in the embankment, the piles and the geosynthetic reinforcement. As part of the evaluation, a state-of-the-art study was done on international design guidelines and analytical models. From the FE simulations, no evident difference in mechanical behaviour was found between the triangular and square piling patterns. The maximum allowed centre-to-centre distance between piles can potentially be increased to 1.4 m, decreasing the number of piles by as much as one third.

Improvement of pressurized flushing efficiency by installing a single pile upstream of the orifice

Removal of sediments from dam reservoirs is an important task for water resources management. The pressurized flushing is a more common way for the evacuation of sediments. The present study experimentally investigates a case of a single pile installed upstream of the orifice to improve the pressurized flushing efficiency. In this regard, five pile cross-section configurations, namely circular, face-on square, corner-on square, corner-on triangular, and side-on triangular, were studied here. The piles were placed at four different distances (4.9, 8.4, 11.9, and 15.4 cm) upstream of the orifice. The results showed that the piles were the most effective when installed with a minimum distance. Furthermore, the flushing cone expanded in volume by increasing the output discharge. The highest increase in the flushing cone volume (671% relative to the control configuration without pile) at a fixed discharge rate was obtained with the corner-on triangular pile. The second highest expansion of the flushing cone volume (362% relative to the control configuration) was obtained with the face-on square pile. Furthermore, at 57% higher than the control case, the circular pile realized the least increase in the flushing cone volume.

Anchor Strength Analysis for Mooring of a Floating Breakwater in Senoro Field, Central Sulawesi

This paper will describe complete investigations of the analysis anchor strength for mooring of a floating breakwater in Senoro Field. The terminal has berthing facilities located in a water depth about 30 meters, with the wave height of 2.7 meters that made difficult for tanker to berth properly. The requirement for berthing ships must have minimum wave heights of 0.7 meters to 1.5 meters as a requirement [1]. Considering the previously mentioned, a floating breakwater has suggested for reducing wave height. The purpose of this final project is to determine the tension mooring line and anchor pile strength to withstand all possible working loads. Response amplitude operator (RAO) of floating breakwater is used to find the structure characteristic as a response due to wave action. Based on the study, wire rope mooring was chosen due to its safety factor passed API RP 2SK standard, such as the biggest tension is 1389,68 kN on line 1 and the smallest is 1157,72 kN on line 8. Calculate anchor pile strength with three types: spun piles, spun square piles, and triangular piles. Anchor pile could be installed depending on three main factors, uplift capacity, bearing capacity and pile in compression. Based on the analysis, uplift capacity result for pile F is 1960.1 kN, while uplift load result is 1958.47 kN, and pile in compression result is 4155 kN while allowable compression result is 5532 kN. For pile G, uplift capacity result is 1960.7 kN, while uplift load result is 1958.47 kN, and pile in compression result is 4599 kN, while allowable compression result is 7189 kN.

Scale-like cantilever cell traps

The micro-domain provides excellent conditions for performing biological experiments on small populations of cells and has given rise to the proliferation of so-called lab-on-a-chip devices. In order to fully utilize the benefits of cell assays, means of retaining cells at defined locations over time are required. Here, the creation of scale-like cantilevers, inspired by biomimetics, on chemically robust planar silicon nitride (Si3N4) film using focused ion beam machining is described. Using SEM and optical profilometry imaging, regular tilting of the cantilever with almost no warping of the cantilever was uncovered. With Monte Carlo simulation, it was found that the ion implantation in the film was limited to tens of nanometers, and SEM imaging confirmed that the ion beam milling edges were smooth. Finite element analysis showed that the scale-like cantilever was best at limiting stress concentration without difficulty in manufacture and having stresses more evenly distributed along the edge. It also had a major advantage in that the degree of deflection could be simply altered by changing the central angle. From a piling simulation conducted, it was found that a random delivery of simulated particles on to the scale-like obstacle should create a triangular collection. In the experimental trapping of polystyrene beads in suspension, the basic triangular piling structure was observed, but with extended tails and a fanning out around the obstacle. This was attributed to the aggregation tendency of polystyrene beads that acted on top of the piling behavior. In the experiment with bacterial cells, triangular pile up behind the cantilever was absent and the bacteria cells were able to slip inside the cantilever's opening despite the size of the bacteria being larger than the gap. Overall, the fabricated scale-like cantilever architectures offer a viable way to trap small populations of material in suspension.

Calculation Method of Soil-Column Area Replacement Ratio in the Composite Foundation

The calculation equations of soil-column area replacement ratio (m) recommended by Chinese code Technical Code for Ground Treatment of Buildings (JGJ79-2012) have many limits in the practice. In this document, general equations of m value are derived by subdividing the composite soil element under the different pile arrangements. The results show that m value is determined by the two parameters: interval number among piles (n) and pile diameter-spacing ratio (d/s). m value greatly decreases with the increase of d/s at the constant n, whereas m slightly decreases with the increase of n at the constant d/s, and the larger n, the smaller drop of m value. Under triangular pile arrangement, the Chinese code recommended equations can be used with less than 10 percent of error ratio of m value when the width of composite foundation is above 10 m, but the general equations should be applied when the width is below 10 m. Under square pile arrangement, the recommended equations can be used when the width of composite subgrade is above 15 m, but the general equations should be applied when the width is below 15 m. The general calculation equations of m value derived in this paper can provide certain reference for theoretical calculation and engineering application.

Wind tunnel and computational study of the stoss slope effect on the aeolian erosion of transverse sand dunes

Abstract To understand aeolian particle entrainment, it is important to take into account the surface slope, as most natural sand surfaces are not horizontal. The influence of slope angle on local friction velocity is the subject of this research. Three transverse triangular piles, with stoss slopes of 10°, 20°, and 32°, were tested experimentally, and modeled computationally. The wind tunnel experiments include two sets of tests: the first one consists of friction velocity measurements across the windward slope and the second set comprises the measurement of the sand dune longitudinal profile over time. The experimental tests were conducted at four undisturbed wind speeds ranging from 8.3 to 10.7 m/s. The computational modeling was performed using a commercial CFD code, and it aimed to replicate the experimental conditions with the objective of evaluating its ability to predict the friction velocity across the windward slope. The numerical predictions of the friction velocity, for the initial longitudinal profile, show good agreement when compared to the experimental values. The region where the predicted friction velocity exceeds the threshold coincides quite well with the eroded area. The correlation between the vertical sand flux, across the stoss slope, calculated using the first eroded longitudinal profile, against the predicted friction velocity showed a cubic relation. The computational model, in view of the predicted results, seems to be a reliable tool for the estimation of the friction velocity for situations similar to those studied in this work.

Comparative Study on Bearing Performance between Y-Section Pile and Conventional Pile

Y-shaped vibro-pile (referred to as Y-Section pile) is a newly developed pile based on traditional circular driven cast-in-place pile and the principle of peripheral expansion of various shapes with constant cross-section. Three-dimensional numerical model is built for Y-Section pile, circular pile, square pile and triangular pile with the same sectional area using finite element software ABAQUS. The pile material is elastic model as well as soil around pile and under pile is Mohr-Coulomb model. With the same cross-sectional area and under the same load, the settlement of Y-Section pile is the smallest, followed by triangular pile, square pile and circular pile in sequence; the average stress of pile-end soil of square pile is the greatest, followed by triangular pile, circular pile and Y-Section pile; the ultimate bearing capacity of Y-Section pile is the largest, followed by triangular pile, square pile and circular pile. Assuming that the lateral friction is of linear growth along pile shaft and of triangular distribution, the maximum lateral friction intensity at pile tip is different for various piles with the same cross-sectional area, and the largest is circular pile, followed by square pile, Y-Section pile and triangular pile. The maximum lateral friction intensity of Y-Section pile is up to 88.71% of circular pile and there is friction resistance weakening with various shapes.

Thermodynamic limit in the elastic triangle: Padé approximants.

The equilibrium properties of a triangular pile of N rows of particles, interconnected by linear springs and subjected to gravity are explored. A preliminary algebraic investigation of the small N value case suggests that the particle displacement field can be represented by low order Padé approximants. [1,1] Padé approximant representations are introduced for the horizontal and vertical displacement field components. Each representation contains three polynomials in the particle position coordinates. In the vertical displacement case the polynomials are successfully fitted to numerical solutions of the equilibrium equations. The resulting expression exhibits a thermodynamic limit with 1/N corrections. This procedure fails in the horizontal case. It is suspected that a higher order Padé approximant is required.

Thermodynamic limit in the elastic triangle: perturbation theory

The equilibrium state of a triangular pile of particles, interconnected by linear springs and subjected to the force of gravity, is explored algebraically. A subset of the springs is treated as weak in relation to the others and perturbation theory is used to obtain the zero order and first order expressions for the equilibrium positions of the particles. The zero order results prove to satisfy a thermodynamic limit. In contrast, the first order results fail to exhibit a thermodynamic limit because the perturbation expansion parameter proves to be a function of the number of rows of particles in the triangle.

Shelter Effect of Porous Fences on the Saltation of Sand Particles in an Atmospheric Boundary Layer

Effects of porous wind fences on the wind erosion of particles from a triangular sand pile were investigated experimentally. The porous fence and sand pile were installed in a simulated atmospheric boundary layer. The mean velocity and turbulent intensity profiles measured at the sand pile location were well fitted to the atmospheric boundary layer over the open terrain. Flow visualization was carried out to investigate the motion of windblown sand particles qualitatively. In addition, the threshold velocity were measured using a light sensitive video camera with varying the particle size, fence porosity and the height of sand pile. As a result, various types of particle motion were observed according to the fence porosity. The porous wind fence having porosity =30% was revealed to have the maximum threshold velocity, indicating good shelter effect for abating windblown dust particles. With increasing the sand particle diamter, the threshold velocity was also increased. When the height of sand pile is lower than the fence height, threshold velocity is enhanced.

Modeling of stress distribution in granular piles: Comparison with centrifuge experiments.

The classical method to compute stress and strain distributions in granular materials is recalled using continuum mechanics approach, and different rheological laws described. It is recalled that granular materials exhibit highly nonlinear response such as nonlinear elasticity, dilatancy and plastic flow. Finite element technique is used to predict the stress field distribution below a conic and a triangular pile. The dependence of the stress distribution on the rheological law, the bottom boundary condition and the building process (horizontal or inclined strata) is demonstrated. These results are compared to experimental data obtained in centrifuge. (c) 1999 American Institute of Physics.

Wall pressure analysis of two-dimension shallow bins with top piles

The top pile of a bin has an effect on the wall pressure distribution. In this paper the method of characteristics and the method of wedges have been employed to analyze wall pressure distributions of 2-D shallow bins with symmetric triangular prism-shaped piles at the top. The results show that these two methods predict very close estimations of the pressures for shallow bins. In addition, compared with the method of characteristics, the Janssen and Coulomb formulae may overestimate the pressures at small and large depths, respectively.

Deformation of an elastic triangle in equilibrium under gravity.

The equilibrium state of a triangular pile of particles interconnected by linear springs and subjected to the force of gravity is investigated numerically. The three strain components describing the deformation of the pile, the density change, and the supporting stress field are calculated. The results (a) exhibit an unexpected richness in behavior and (b) show evidence of a thermodynamic limit in small (\ensuremath{\sim}100 layers) piles.

Force distribution in a two dimensional sandpile

We have constructed a discrete element computational code which solves the equations of motion that describe particle-particle interactions. As a first example we have applied the code to a two dimensional triangular pile of discrete particles. We take this to be a two dimensional analogue of a conical pile of particulate material. With this simple model, we try to understand—with partial success—the experimental results of Smid and Novosad ( I. Chem. E. Symp., 63 (1981) D3/V/1) which show a counter-intuitive dip in the normal stress underneath the highest section of the pile. We also obtain two separate analytic models, one based on recurrence relations and the other on a continuum approximation, to describe the force distribution inside a two dimensional pile of particulate material.

Activities: How Many Blocks in a Triangular Pile?

Activities: How Many Blocks in a Triangular Pile?