Pile Width Research Articles

Performance of Pile–Wall System Adjacent to Footings

The performance of a retaining wall is dependent on multiple factors including lateral earth pressure, which results from backfill soils and adjacent footings located behind a retaining wall. The prediction of a retaining wall’s performance in a footing–soil–wall system (FSPS) must incorporate the influences caused by the movement of a retaining wall. This study examines the performance of a retaining wall formed by driven, precast, concrete piles located adjacent to a concrete footing using two- and three-dimensional finite element analysis (2D and 3D FEA) by ANSYS 13.0 software. Both soil and concrete are assumed to behave as non-linear, elastic-perfectly plastic and rate-independent materials in compliance with the upper-bound model of Drucker–Prager yield criterion. Three backfill and foundation soils are considered: kaolin, silty clay, and kaolin–sand. Various conditions of soil type, footing shape ratio, pile width, and footing–pile distance through 180 FEA runs are investigated. The effects of 2D and 3D FEA on the behavior of the pile–wall system are compared. The lateral deflection and pressure distribution profiles along the pile–wall are studied and presented. Two empirical equations predicting lateral deflections at the pile toe and pile head and useful for pile structural design are developed under the ultimate pressure of the adjacent footing.

Influence of Slope on Calculative Width of Pile

Influence of Slope on Calculative Width of Pile

A new model for mechanical calculation of h-type anti-slide piles

h-Type anti-slide piles (hTPs) have been receiving increasing attention in slope reinforcement engineering. However, most of the existing calculation methods for hTP responses exclusively consider the influence of earth pressure on the pile shaft. This study presents a new model for the hTP based on the Winkler foundation. The deformation of the back pile is taken as the constraint condition, and a calculation program for a statically indeterminate structure satisfying the pile–soil deformation coordination condition is created. An iterative method is used to address the internal force and deformation of the cantilever, loaded, and anchorage sections of the hTP. The rationality of the proposed model is verified by comparing it with previous models. A comparison of the hTP with an ordinary anti-slide pile (AP) shows that the top displacement of the hTP is 41.4 % smaller than that of the AP with an identical sectional area. Further parametric analysis reveals that increasing the pile width can considerably reduce the hTP top displacement, but the inertial moment and elastic modulus have weak influences on that displacement.

Development of unified p–y curve model for clays using finite element analysis of laterally loaded piles

In this study, a unified p–y curve model is developed for clays in undrained conditions using the results of 3D finite element (FE) modeling. The p–y curves are primarily used in the analysis of laterally loaded piles. Formulas for the ultimate lateral bearing capacity factor ( Np), and the reference deflection in the p–y curve ( y50), were obtained using the results of parametric studies and regression analysis. The tangent hyperbolic function was used to model the p–y curve shape. In the FE models, the clay soil material was modeled as elastic-perfectly plastic material using Mohr–Coulomb criteria, and the pile material was modeled as elastic only. The parametric study results show that Np varies nonlinearly with depth. The proposed model for Np is composed of two regions: a nonlinear zone and a linear zone. The model for Np used the undrained shear strength ( su), effective unit weight of soil ( γ′), and pile width ( D) as parameters. Further, the proposed model for y50 was found to be dependent on the soil stiffness ( Es), D, and Np. The dependency of y50 on Np was often overlooked in previous studies. Finally, the proposed model was imported in LPILE program and the results from previous case studies were compared with the proposed model predictions.

Morphological Evolution of Passive Soil Arch in Front of Horizontal Piles in Three Dimensions

The anti-slide pile is a primary method of landslide control. The effect of the passive soil arch in front of the embedded section of piles has a significant effect on the anti-slide pile’s bearing capacity. The upgraded model test scheme was used to conduct model tests with a pile spacing four times the width of the pile and a geometric scale ratio of 1:15. The anti-slide pile stress, pile bending strain, and soil stress in front of the pile were all studied in relation to the loading amount. In addition to the model test, the numerical simulation method was utilized to investigate the three-dimensional morphological change of the passive soil arch in front of the pile. The results indicated that: clearly, the side piles can eliminate the border effect. The distribution of pile bending strain along the pile after loading is referred to as a parabola. Bending failure occurred at a depth of 40 mm, approximately 0.9 m from the pile top. Under the condition that the pile spacing is four times the pile width, a passive soil arch occurs in front of the anti-slide pile’s fixed part, and its development can be split into four stages: formation, development, completion, and destruction. The passive soil arches in front of the piles are generated and destroyed gradually along the buried depth, and the three-dimensional surface of the space drops gradually along the buried depth with the loading amount and advances toward the loading direction until the anti-slide pile system fails. The research findings and experiences can serve as a basis for future research.

Interaction mechanism of the anti-slide pile and sliding mass based on the soil arching effect

Anti-slide pile has been one of the most used preventive measures for the landslide treatment in the recent years. The pile spacing has a significant impact on the arching effect which develops due to the relative compressibility of soil relative to the anti-slide piles. To reveal the interaction mechanism of pile and soil, the soil stress behind the anti-slide piles was studied based on the stress analysis of a semi-infinite plate. The influencing factors, such as time, pile spacing, and pile number were considered for the soil arching effect determination. A new method for determining the maximum pile spacing was presented, based on the Mohr-Coulomb failure criterion and the ultimate equilibrium method. The stress nephogram behind the anti-slide piles was obtained, and different distributions of soil arches, including the hyperbolic arch, extended shoulder arch, inverted bell arch, and circular arch were observed to be influenced by both the pile width and spacing. For the same pile width, the additional stress of soil decreases with the increase in the pile spacing. However, for the same pile spacing, a less apparent soil arching effect was observed when the pile width was smaller. This work can provide a simple solution for determining the soil stress and maximum pile spacing for the anti-slide pile design.

Research on the overall bearing behavior characteristics of the all-vertical-piled wharf under horizontal load

Based on the ANSYS model, the simulation analysis of the all-vertical-piled wharf is carried out. It is found that the zero point of the pile displacement of the all-vertical-piled wharf is about 6 times the depth of the pile width (pile diameter) below the mud surface. The difference in pile displacement changes under various working conditions below this position is very small, and the pile displacement above this position is positively correlated with the horizontal load. Through research, the pile displacement curve and load-displacement curve of the all-vertical-piled wharf are constructed, and the method for determining the overall ultimate bearing state of the all-vertical-piled wharf is established. The research results can provide a reference for the study and judgment of the overall bearing safety of the all-vertical-piled wharf under horizontal load.

Influence of Geometry and Separation Walls on The Behaviours of Pull-out Pipe Piles Embedded in Sandy Soil

Predicting of piles capacity and their behavior is always an important and serious problem for a safe geotechnical engineering design. In the present study, experimental model tests have been conducted on a single steel pipe piles driven in sandy soil and subjected to pull-out force. The experimental tests were conducted on vertical open-ended piles with circular and square cross-sectional area and three various diameters 3 cm, 4 cm and 5 cm in a steel soil box have been used. The tested pile’s model has embedment with three penetration ratios (PR=L/D) of 10, 15 and 20. All tests were done in medium density soil (Dr = 50%) with open ended pipe pile to study the effect of pile geometry on pile behavior, and three other tests were conducted on the 5cm diameter and 10 penetration ratio in medium soil density to study the importance of addition of separating wall. The study discovered that the capacity of single piles with circle cross-section area under pull-out force increasing by 211% and 458% with the increasing of pile diameter (width) from 3cm to 4cm and 5cm respectively, and increasing by 210%, 448% and by 112%, 288%. Also, by 79% and 211% with increasing penetrating ratio (PR) from 10 to 15 and 20 for diameters 3cm, 4cm and 5cm respectively, with respect to reference pile. And the same behavior for square cross-section pipe pile, when the pull-out capacity increasing with the increase of pile width and penetration ratio due to the increasing in the friction area. Besides that, It was also found that the separation walls increased the coefficient of lateral pressure in addition to the friction area. At the same time, there are an optimum number of separation walls that can be used to increase the pile pull-out capacity and that when using three separation walls.

Effect of the inclined pile-soil arch in a soil landslide reinforced with anti-sliding piles

Aiming at the stability of a highway slope reinforced with anti-sliding piles, the mechanical behaviour of the inclined pile-soil arch in a soil slope reinforced with anti-sliding piles was analysed. Based on the pile-soil arching effect, a mechanical calculation model of the inclined pile-soil arch was established. According to the limit equilibrium condition of the inclined pile-soil arch, the analytical solution for pile width on the vault was obtained when the earth pressure on the pile side was distributed in triangular and parallelogrammic shapes. Based on the positional relationship of the vault of the pile-soil arch axis, the equations for inclined and horizontal pile-soil arches and the corresponding arching conditions were obtained. Analysis of a case study indicated that the sliding force of the pile-soil arch, pile width, cohesion, and internal friction angle of soil all influenced the arching condition of the inclined pile-soil arch and the designed pile spacing. When the sliding force exceeded 3500 kN/m, the calculated results according to the inclined pile-soil arch and horizontal arching models could not satisfy the arching condition. When the sliding force exceeded 2000 kN/m, the clear pile spacings calculated according to the inclined and horizontal pile-soil arch models were similar; in the case that the internal friction angle exceeded 15°, the clear pile spacings calculated based on the two models were similar; at a low internal friction angle, the results calculated according to the two models could not satisfy the arching condition; at a large internal friction angle, the results calculated based on the inclined pile-soil arch could satisfy the arching condition, while those based on the horizontal arching could not; when the pile width was less than 1 m, the results calculated based on the above two models could not satisfy the arching condition. Therefore, it is more reasonable to perform analysis by utilising the equation for the inclined pile-soil arch and the pile spacing calculated when the pile-soil load was distributed in triangular form was lower than that when the pile-soil load was distributed in parallelogrammic shape.

Performance of sheet pile to mitigate liquefaction-induced lateral spreading of loose soil layer under the embankment

Liquefaction-induced lateral spreading of the foundation soil severely damages the embankment resting on it. Installation of sheet pile near the toe of the embankment is a widely used technique to mitigate lateral spreading of the foundation soil and the associated damage to the embankment. However, several factors, such as the thickness of the liquefiable foundation, width of sheet pile, and softening of the bearing stratum, that may affect the performance of the sheet pile as seismic retrofit against lateral spreading has not been well studied yet. Therefore, a series of dynamic centrifuge experiments are carried out to study the applicability of sheet pile in various thickness of liquefiable foundation under moderate to strong sequential ground motions. It is found that the sheet pile effectively mitigates the lateral spreading of a thin as well as thick liquefiable foundation. Besides, the sheet pile having the same width of the target area performs equally as a wider sheet pile in mitigating channel-ward ground movement. The experimental results also show that the liquefaction-induced softening of the dense bearing stratum immediately below the loose foundation significantly influences the performance of the sheet pile.

Settlement analysis of pile cap with normal and under-reamed piles

The use of pile foundations has become more popular in recent years, as the combined action of the pile cap and the piles can increase the bearing capacity, reduce settlement, and the piles can be arranged so as to reduce differential deflection in the pile cap. Piles are relatively long, slender members that transmit foundation loads through soil strata of low bearing capacity to deeper soil or rock strata having a high bearing capacity. In this study analysis of pile cap with considering different parameters like depth of the pile cap, width and breadth of the pile cap, type of piles and different types of soil which affect the behaviour of pile cap foundation is carried out by using Finite Element Software ANSYS. For understanding the settlement behaviour of pile cap foundation, parametric studies have been carried out in four types of clay by varying pile cap dimensions with two types of piles namely normal and under-reamed piles for different group of piles. Furthermore, the analysis results of settlement and stress values for the pile cap with normal and under-reamed piles are compared. From the study it can be concluded that settlement values of pile cap with under-reamed pile are less than the settlements of pile cap with normal pile. It means that the ultimate load bearing capacity of pile cap with under-reamed piles are greater than the pile cap with normal piles.

Calculative Width of Pile Foundation on Slope Based on Particle Image Velocimetry (PIV)

The calculative width directly affecting the horizontal bearing capacity of the pile is an important parameter of the horizontal loaded pile foundation and its effective value will change with the variation of slope angle. In order to research the effect of slope on calculative width, 4 groups of model test under static lateral loading with different slope angles were carried out indoor. Based on the PIV system, the horizontal diffusion angle was obtained by the quantitative analysis of the vectorial displacement field of soil around the pile. The calculative width of pile under 4 slopes was then calculated based on the Horizontal Diffusion Principle. Compared with numerical simulation and full‐scale test, calculative width based on Horizontal Diffusion Principle is greater than that based on the code of China (JGJ94‐2008) and it decreases by about 3.3 m by every 10° increase of slope. After correcting the calculative width based on Horizontal Diffusion Principle, m‐value that can characterize the horizontal resistance of the pile is greater than that based on the code of China (JGJ94‐2008); the average difference of two m‐values is about 75 MN/m4. Slope has a strong weakening effect on m‐value. These conclusions provide a certain reference for the selection of calculative width in engineering.

Model Study on Burden Distribution in COREX Melter Gasifier

COREX is one of the commercialized smelting reduction ironmaking processes. It mainly includes two reactors, i.e., a (reduction) shaft furnace (SF) and a melter gasifier (MG). In comparison with the conventional blast furnace (BF), the COREX MG is not only equipped with a more complicated top charging system consisting of one gimbal distributor for coal and eight flap distributors for direct reduction iron (DRI), but also the growth mechanism of its burden pile is in a developing phase, rather than that in a fully-developed phase in a BF. Since the distribution of charged burden plays a crucial role in determining the gas flow and thus in achieving a stable operation, it is of considerable importance to investigate the burden distribution influenced by the charging system of COREX MG. In the present work, a mathematical model is developed for predicting the burden distribution in terms of burden layer structure and radial ore/coal ratio within the COREX MG. Based on the burden pile width measured in the previous physical experiments at different ring radii on a horizontal flat surface, a new growth mechanism of burden pile is proposed. The validity of the model is demonstrated by comparing the simulated burden layer structure with the corresponding results obtained by physical experiments. Furthermore, the usefulness of the mathematical model is illustrated by performing a set of simulation cases under various charging matrixes. It is hoped that the model can be used as a what-if tool in practice for the COREX operator to gain a better understanding of burden distribution in the COREX MG.

Influence of Pile Width and Pile Stiffness on Lateral Subgrade Reaction

Influence of Pile Width and Pile Stiffness on Lateral Subgrade Reaction

Systematic Onset of Periodic Patterns in Random Disk Packings.

We report evidence of a surprising systematic onset of periodic patterns in very tall piles of disks deposited randomly between rigid walls. Independently of the pile width, periodic structures are always observed in monodisperse deposits containing up to 10^{7} disks. The probability density function of the lengths of disordered transient phases that precede the onset of periodicity displays an approximately exponential tail. These disordered transients may become very large when the channel width grows without bound. For narrow channels, the probability density of finding periodic patterns of a given period displays a series of discrete peaks, which, however, are washed out completely when the channel width grows.

Support characteristics of eco-spiral pile with respect to twisting angle and ratio of borehole diameter to pile width

This study numerically analysed the characteristics of eco-spiral piles (Eco-SPs) as multi-purpose geotechnical supports. The behaviour of eco-spiral piles in the ground was studied with respect to their twisting angle and the ratio of borehole diameter to eco-spiral pile width using FLAC-3D based on the finite-difference method. A cement mortar grout was modelled to sustain the eco-spiral pile in a sandy soil. Relationships were found among the eco-spiral pile’s twisting angle, pull-out load and maximum shear stress. The results should aid the further design of the bolts for application in a range of circumstances.

Experimental Study to Evaluate the Effect of Consolidation Behavior on Pile Setup

Abstract This paper presents the field experimental results of static load tests (SLTs) and dynamic load tests (DLTs) that were conducted on instrumented prestressed concrete (PSC) test piles to characterize the pile setup phenomenon for individual soil layers along the piles' length. For this purpose, three PSC piles were driven at a bridge construction site in Lake Charles, LA, that were tested at different times after installation. The piles were instrumented with sister bar strain gauges to measure the load transfer along the piles' length, and pressure cells and piezometers to measure the total stress, effective stress and excess pore water pressure (PWP) with time and hence the setup for different soil layers along the piles' length. Multilevel piezometers were installed in the surrounding soil to evaluate the spatial distribution of excess PWP and to measure the influenced zone caused by pile driving. The load tests showed that the side resistance increased by 129 %, 99 %, and 91 % for the three test piles during the last load test. The case pile wave analysis program (CAPWAP) analysis of the DLTs and the load distribution plots from SLTs were used to compute the resistance of individual soil layers along the piles with time. The results showed that the soil layers with low undrained shear strength and high value of generated excess PWP exhibited higher amount of setup; while soil layers with low permeability and low coefficient of consolidation exhibited higher rate of setup compared to other soil layers. The results also showed that setup increased at a higher rate before the dissipation of excess PWP and the rate became much slower after the end of dissipation process. The dissipation of excess PWP (or consolidation data) was used to quantify the setup by its contributing factors (i.e., consolidation and aging effect). The results showed that a majority of setups was because of the consolidation effect. The results of multilevel piezometers indicated that the influenced zone because of pile driving was almost 3B (B = pile width) radial distance from pile face.

Investigation of Soil-Arching Development in Dense Sand by 2D Model Tests

A trapdoor system has frequently been used to study soil arching and its development in recent years. The load transfer in the fill of piled embankments is very similar to a trapdoor system with multiple trapdoors. There are multiple arching models described in different standards and guidelines for piled embankments that can be subdivided into three archingmodel families. To study the soil-arching type and its development, a series of model tests with sand fills were carried out in a two-dimensional (2D) multi-trapdoor test setup. The tests considered four factors—the fill height, trapdoor width, pile width, and grain size of the sand—with four values for each factor. Triangular slip surfaces were found at very small deformations using the particle image velocimetry (PIV) technique. These surfaces evolved in ways that could be related to the three types of stress-distribution ratio curves, with development patterns similar to the arching families of piled embankments: (1) the rigidmodel family, (2) the equal-settlement-plane-model family, and (3) the limit-equilibriummodel family. The limit-equilibrium-model family occurred in tests with narrow trapdoor widths.

Investigation on 3D ground deformation and response of active and passive piles in loose sand

Two scaled-model tests were carried out to investigate the pile–soil–pile interaction during a lateral loading process. Two instrumented piles, termed the active pile and the passive pile, were installed into loose sand. The active pile head was subjected to lateral loads, and the passive pile was set at twice pile width away from the active pile center. To study the effect of the direction of lateral loading on the pile–soil–pile interaction, the passive pile was set in front of and behind the active pile in Tests 1 and 2, respectively. Experimental results showed that the leading passive pile produced much stronger effects on surrounding ground deformation and on response of active pile as compared with the trailing passive pile. The intermediate soil between the active and passive piles was the most susceptible to be affected by the leading passive pile. Within this zone, the larger magnitude of ground heave (by up to 50 %) was caused by the leading passive pile. The leading passive pile also enhanced the lateral resistance of the active pile by up to 70 %. The underlying reason is that the leading passive pile was located in the passive influence zone of the active pile and hence restrained the intermediate soil between the two piles. As a result, the relative stiffness ratio between soil and pile increased, leading to a stronger soil resistance.

Prediction of the Settlement for the Vertically Loaded Pile Group Using 3D Finite Element Analyses

The settlement prediction of small pile group at working load using 3D Finite Element (FE) approach was carried out based on the case of Belfast pile load test. Three different types of analysis were investigated: a linear elastic (LE) analysis where all the soil was assumed to be linear elastic, a complete nonlinear (CNL) analysis where both the soil adjacent to the pile shafts and between the piles using the Hardening Soil (HS) model, and a nonlinear and linear elastic analysis (NL-LE) with the soil close to the pile shafts using HS model while the soil in the remaining area is modeled as an elastic material. Then all the FE analyses were compared to the analytical approach (RATZ). The results of FE analysis suggest that incorporating a nonlinear zone of soil close the pile shaft and leaving the soil linear elastic beyond this zone gives more reasonable estimation of interaction factor, thus, a much better prediction of pile group settlement will be observed. It is suggested that a value of half the pile width for the distance from pile shaft to the edge of this nonlinear zone would be sufficient to capture the load transfer mechanism for a typical pile group. While best prediction was given by RATZ approach as the group settlement ratio which reflect the interaction effect between piles in the group obtained from RATZ mostly close to the field measurements.