Lateral Resistance Of Piles Research Articles

Research on Effect of Heap Loading on Deformation and Mechanical Properties of Bridge Double Pile Foundation on Steep Slope

In order to analyze the deformation and stress characteristics of the pile foundation on the slope, this paper uses the finite element software Abaqus for numerical simulation. The displacement and stress data of pile under different working conditions (the combination of heap load and vertical load and horizontal load and inclined load) were collected; the distribution of pile displacement, axial force and bending moment were analyzed. Simulation results show that: slope top loading has little effect on vertical displacement; when the heap load exceeds 200 kPa, the horizontal displacement is greatly affected. Pile axial force decreases with pile burial depth; pile lateral resistance plays a more adequate role in the rock and soil layer. The bending moment of double pile foundation is positive at the top and negative at the bottom. Applied oblique load has obvious p-Δ effect.

Effect of ground improvement on the lateral resistance of closed-end steel pipe piles in a coal ash pond

This study assessed the effect of configuration of the ground-improved body to improve the lateral resistance of piles driven into a coal ash pond. Nine closed-end steel pipe piles were studied by lateral load tests in the investigation, which included four test piles and five reaction piles. While TP1 pile was carried out without the reinforcement, TP2, TP3, and TP4 piles were tested with various reinforcements, including grid-type, block-type, and cross-type. The lateral load test results showed that the ultimate lateral loading capacity, pile-head stiffness, and soil resistance of the reinforced piles compared with TP1 pile were increased by 26%–39%, 54%–238%, and 33%–128%, respectively. Conversely, the maximum bending moments of the reinforced piles were reduced by 48%–73%, respectively. Soil-mixing wall reinforcement was found to increase effectively the lateral resistance of the closed-end steel pipe piles in a coal ash pond. However, because a variety of ground-improved body configurations can increase the lateral resistance of piles, the choice of the type of reinforcement must be considered for reliable design, construction feasibility, and economic benefits of engineering practice.

Group effect on ultimate lateral resistance of piles against uniform ground movement

In earthquake engineering, pile foundations are designed to withstand the lateral loading that results from large displacements due to ground movement caused by strong earthquakes. The distress and failure of superstructures occurs when the lateral load exceeds the ultimate lateral resistance of the piles. The aim of this study is to estimate the ultimate lateral resistance of piles especially in terms of the group effect induced by the pile arrangement. Several experimental and numerical analyses have been conducted on pile groups to investigate the group effect when the groups are subjected to uniform large horizontal ground movement. However, the ultimate lateral resistance of the pile groups in these studies was calculated by applying load to the piles. The present study directly assesses the ultimate lateral resistance of pile groups against ground movement by systematically varying the direction of the ground movement. Although the load bearing ratio of each pile in a pile group, defined as the ratio of the ultimate lateral resistance of each pile in a pile group to that of a single pile, is an important design criterion, it was difficult to assess in past works. This study focuses on the load bearing ratio of each pile against ground movement in various directions. The use of the finite element method (FEM) provides options for simulating the pile-soil system with complex pile arrangements by taking the complicated geometry of the problem into account. The ultimate lateral resistance is examined here for pile groups consisting of a 2 × 2 arrangement of four piles, as well as two piles, three piles, four piles, and an infinite number of piles arranged in a row through case studies in which the pile spacing is changed by applying the two-dimensional rigid plastic finite element method (RPFEM). The RPFEM was extended in this work to calculate not only the total ultimate lateral resistance of pile groups, but also the load bearing ratio of the piles in the group. The obtained results indicate that the load bearing ratio generally increases with an increase in pile spacing and converges to almost unity at a pile spacing ratio of 3.0 with respect to the pile diameter. Moreover, the group effect was further investigated by considering the failure mode of the ground around the piles.

Effect of geometric nonlinearity on the ultimate lateral resistance of piles in clay

In this note we investigate how the assumption of small deformations affects the estimation of the ultimate resistance to lateral pile movements in clay. For that we perform coupled hydro-mechanical finite element analyses, using the Modified Cam Clay model to describe soil behaviour. Validation of the numerical methodology via small-strain analyses is followed by an investigation on how the ultimate resistance diverges from exact plasticity solutions when large displacements are considered. Results suggest that the failure mechanism depends on the pile displacement required to mobilise the ultimate resistance, and that small-strain plasticity solutions provide upper bounds of the ultimate resistance.

Experimental Study of Micropile Lateral Resistance Effectiveness

Abstract The range of soil around the micropile when the pile is mobilized by force and the sensitivity of design parameters variation to the effect of micropile was studied by the prototype test and numerical calculation of the effect of lateral resistance of micropile. During the experiment, the variation of soil pressure around the micropile was monitored under the step loading, and the influence distance of lateral resistance on the pile is analyzed, and the high, middle, and low impact radius is defined according to the degree of influence. The distribution of vertical displacement of soil around pile when the pile diameter, pile length, and soil physical properties change was analyzed using numerical calculation, as well as the effects of normalized parameters on the influence of lateral resistance. Results showed that to better utilize the anti-slide coupling effect between piles where the soil overlying on the slope is formed by silty clay, pile spacing should be within the mid to high impact radius. Compared to other parameter changes, optimizing the pile length had the greatest effect on increasing pile lateral resistance and impact radius. Results provided a basis for designing effective pile spacing in anti-slide micropile groups.

On the behaviour of pile groups under combined lateral and vertical loading

The effect of vertical loads on the lateral response of a 3×5 pile group embedded in sandy and clayey soils is studied through 3D finite differences analyses using the computer code FLAC3D. In the numerical model, the piles were treated as a linear elastic material and the soil was idealized using the Mohr-Coulomb constitutive model with a non-associated flow rule. Vertical loads, inducing a vertical pile head displacement of 0.01-pile diameter, were applied prior to the application of the lateral loads. Numerical results showed that the lateral resistances of the piles installed in sandy soil increase with vertical loads. However, the presence of vertical loads on piles embedded in clay reasonably decreases their lateral capacities. The increase and decrease in the lateral stress in the sandy and clayey soils, respectively, are the major driving factors to contribute the change in the lateral resistance of piles, depending on the pile position in the group and its lateral deflection. The distribution of lateral loads among piles in the group tends to be more uniform when vertical loads were considered leading to a more economical pile foundation design.

極大地震時の杭および改良体の外周地盤の強非線形化が杭基礎建物の応答に及ぼす影響

This paper describes effects of strong nonlinear interaction between soil and piles or improved soil on seismic response of a building supported by piles. Shaking table tests by large earthquake inputs were conducted using structure model supported by piles in dry sand. 3D-nonlinear analyses were also conducted to investigate the effects of strong nonlinearity of ground around piles or improved soil. It is obtained that strong nonlinearity of ground around piles or improved soil affects the response of superstructure and pile stress. Especially, the strong nonlinear behavior of ground around improved soil changes the response of superstructure and the lateral resistance of piles.

Simple Expression of the Ultimate Lateral Resistance of Piles on Sand based on Active Pile Length

Simple Expression of the Ultimate Lateral Resistance of Piles on Sand based on Active Pile Length

Variation of limiting lateral soil pressure with depth for pile rows in clay

Pile group interaction effects on the lateral pile resistance are investigated for the case of a laterally loaded row of piles in clay. Both uniform undrained shear strength and linearly increasing with depth shear strength profiles are considered. Three-dimensional finite element analyses are presented, which are used to identify the predominant failure modes and to calculate the reduction in lateral resistance due to group effects. A limited number of two-dimensional analyses are also presented in order to examine the behaviour of very closely spaced piles. It is shown that, contrary to current practice, group effects vary with depth; they are insignificant close to the ground surface, increase to a maximum value at intermediate depths and finally reduce to a constant value at great depth. The effect of pile spacing and pile–soil adhesion are investigated and equations are developed for the calculation of a depth dependent reduction factor, which when multiplied by the limiting lateral pressure along a single pile, provides the corresponding variation of soil pressure along a pile in a pile row. This reduction factor is used to perform p–y analyses, which show that, due to this variation of group effects on the lateral soil pressures with depth, the overall group interaction effects depend on the pile length. Comparisons are also made with approaches used in practice that assume constant with depth reduction factors.

Numerical investigation of the ultimate lateral resistance of piles in soft clay

The paper presents a numerical study on the undrained lateral response of a single, free-head, reinforced concrete pile in soft clays. Soil conditions simulating normally consolidated clays are examined—undrained shear strength increasing with depth—and the pile-soil interaction under static lateral loading is analyzed. The nonlinear p-y curves proposed in literature for soft clays are imported into a beam-on-nonlinear-Winkler-foundation simulation in order to predict the pile head lateral load—displacement curve and the distribution of the horizontal displacement and bending moment along the pile. The striking differences among these methods require further investigation via 3D finite element analyses. The determination of the ultimate soil resistance p ult from the results of the finite element analyses aims at providing the estimation of a range of values for the ultimate soil resistance coefficient N p with depth and the comparison of the derived values to the corresponding ones proposed by existing methodologies.

On the influence of vertical loads on the lateral response of pile foundation

The influence of vertical loads on the lateral response of group piles installed in sandy soil and connected together by a concrete cap is studied through finite elements analyses. The analyses focus on the five piles in the middle row of 3×5 pile groups. The vertical load is applied by enforcing a vertical displacement equivalent to 2% of the pile diameter through the pile cap prior to the application of the lateral loads. The results have shown that the lateral resistance of the leading pile (pile 1) does not appear to vary considerably with the vertical load. However, the vertical load leads to 23%, 36%, 64%, and 82% increase in the lateral resistance of piles 2–5, respectively. The increase in the lateral pressures in the sand deposit is the major driving factor to contribute the change in the lateral resistance of piles, depending on the position of the pile in the group. The distribution of lateral loads among piles in the group tends to be more uniform when vertical loads were considered leading to a more economical pile foundation design.

Ultimate Lateral Resistance of Piles in Cohesive Soil

The ultimate lateral resistance of piles in cohesive soil is studied using the well-known finite difference code, FLAC2D. The Modified Cam Clay (MCC) constitutive relation is adopted in the analyses to model the cohesive soil behavior, whereas the structural pile model with three degree of freedoms, available in FLAC2D library, is adopted to model the piles. The reliability of Broms's method, still used in the current design practice of piles under lateral loads, is verified. Comparisons between the ultimate lateral resistances of piles and those deduced from the graphs proposed by Broms (1964) are presented in graphs. Different factors thought to affect the lateral resistance of piles in cohesive soil, not adequately considered in Broms's method, such as clay stiffness, pile length, pile diameter and axial load are parametrically studied. A special concern is devoted to elucidate the effects of over-consolidation ratio (OCR) on the ultimate lateral resistance of piles in cohesive soil.

Undrained limiting lateral soil pressure on a row of piles

The displacement finite element, lower and upper bound finite element limit analysis and analytical upper bound plasticity methods are employed to investigate the undrained limiting lateral resistance of piles in a pile row. Numerical analyses and analytical calculations are presented for various pile spacings and pile–soil adhesion factors. The numerical results are shown to be in excellent agreement with each other and also with the theoretical upper bounds produced by the analytical upper bound calculations. Based on the numerical and analytical results, an empirical equation is proposed for the calculation of the ultimate undrained lateral bearing capacity factor. This equation is subsequently used to calculate p-multipliers applicable to the lower part of piles in pile rows, which are compared to multipliers available in the literature (that are constant with depth). The comparison shows significant differences, indicating that the amount of reduction in lateral resistance due to group effects is not constant with depth as routinely assumed in practice.

Investigation of Static Laterally Loaded Pile in Layered Sandy Soil

Investigation of the static lateral load resistance of pile on layered sandy soil was made by laboratory model test on single pile. The experiment was carried out with variable diameter and variable embedded length of pile on sandy soil. In this study, model pile was single pile which satisfies the Meyerhof’s Relative Stiffness limit of pile for flexible pile. Single pile embedded length, L=0.46m, 0.609m, 0.762m for pile diameter, d=0.013m, 0.019m, 0.026m, respectively. And for surcharge condition embedded length of single pile, L=0.609m and surcharge of pressure, P=3369.55Kg/m3, P=6739.1 Kg/m3 and P=13478.20Kg/m3 for each diameter and for saturated condition of pile diameter, d=0.013m. These experiments were conducted with local sand of Rajshahi region and domar sand; available in Bangladesh. Lateral static loads were applied in the single by a static lateral load set up arrangement. Due to the static lateral load the pile was deflected. The load-displacement response, ultimate resistance of pile has been qualitatively and quantitatively investigated in the experiment. The lateral resistance of pile obtains by experiment and the ultimate lateral load resistances obtained by analytical methods were compared. The load displacement curves are similar and non-linear. Lateral failure at a pile head displacement from 8 to 10, 7 to 9 and 6 to 8mm for single pile of d= 0.013m, 0.019m and 0.026m, respectively. In the case of saturated condition of sand a pile head displacement 15mm for single of d=0.013m. It observed that the failure load was the point at which the curve exhibits a pick or maintains continuous displacement increase with no further increase in lateral resistance. DOI: http://dx.doi.org/10.3329/jsf.v8i1-2.14630 J. Sci. Foundation, 8(1&2): 83-88, June-December 2010

Vertical loads effect on the lateral pile group resistance in sand

Vertical loads effect on the lateral response of a 3×5 pile group embedded in sand is studied through a two-dimensional finite element analysis. The soil-pile interaction in three-dimensional type is idealized in the two-dimensional analysis using soil-pile interaction springs with a hysteretic nonlinear load displacement relationship. Vertical loads inducing a vertical pile head displacement of 0.1-pile diameter increase the lateral resistance of the single pile at a 60 mm lateral deflection by 8%. Vertical loads inducing the same vertical displacement applied to a pile group spaced at 3.92-pile diameter increase the overall lateral resistance by 9%. The effect on individual piles, however, depends on the pile position. The vertical load decreases the lateral resistance of the leading pile (pile 1) by 10% and increases the lateral resistances of piles 2, 3, 4, and 5 by 9%, 14%, 17%, and 35%, respectively. Vertical loads applied to the pile group increase the confining pressures in the sand deposit confined by the piles but the rate of increase in those outside the group is relatively small, resulting in the difference in a balance of lateral soil pressures acting at the back of and in front of the individual pile.

Effects of existing piles on lateral resistance of new piles

Cyclic lateral-loading centrifuge tests were conducted on a new pile located at the center of 2×2 existing piles, to evaluate the effects of the existing piles on the new pile's lateral resistance when the piles of an old building are left derelict. Furthermore, two-dimensional FEM analyses of the horizontal cross sections of the pile–soil systems were carried out. The centrifuge test results show that the lateral resistance of a new pile, located among existing piles, shows slight increases. The existing piles increase the horizontal subgrade reaction of the upper part of the new pile, but slightly decrease that of the lower part of the new pile. Numerical analyses reveal that the key to whether an existing pile increases the horizontal subgrade reaction of a new pile or not, is the soil displacement at the location of the existing pile. An existing pile increases the horizontal subgrade reaction of a new pile when the existing pile displacement is less than the soil displacement caused by the new pile. Conversely, an existing pile decreases the horizontal subgrade reaction of a new pile when the existing pile displacement is greater than the soil displacement caused by the new pile.

Reduced lateral resistance of abutment piles near MSE walls based on full-scale tests

Pile foundations for bridges must often resist lateral loads produced by earthquakes and thermal expansion or contraction. In addition, space constraints are also leading to vertical mechanically stabilized earth (MSE) walls at abutment faces. Available test results indicate that lateral pile resistance can decrease significantly as piles are placed closer to MSE walls. However, no design procedure is available for assessing the decrease in resistance or the effect of the reinforcement on lateral resistance. In this study, full-scale tests were conducted on three 400 mm pipe piles spaced at 1.6, 2.9 and 5.2 pile diameters behind a 10.5-m high MSE wall. The piles were double wrapped with a 0.25 mm thick sheet of low-density polyethylene (LDPE) to reduce down drag. The measured lateral resistance decreased as the spacing behind the wall decreased. The lateral resistance of the pile at 1.6 diameters from the wall was less than one-half of that for the pile at 5.2 pile diameters. Measured tensile forces were higher in the reinforcements adjacent to the pile closest to the wall indicating that the reinforcing grid was supplying additional resistance to pile movement. Back-analyses using a <i>p-y</i> curve approach found the friction angle and <i>k</i> value to be 28° and 41 MN/m³, respectively for the pile located 5.2 diameters away from the wall. These values are significantly lower than other lateral load tests in similar gravels on piles without LDPE sheets. P-multipliers to account for the reduced capacity were developed and provided reasonable agreement with measured response.

Lateral resistance of a pile installed near a reinforced slope

Carpet shreds and carpet shred–soil mixtures can be used as alternative backfill material in many geotechnical applications. In this study an experimental testing programme was undertaken using small-scale model tests with the goal of evaluating the lateral resistance of a single pile located near a reinforcing sandy slope. A broad series of conditions including unreinforced cases was tested by varying parameters such as: carpet shred content (i.e. ratio of the weight of the shreds to weight of dry sand), aspect ratios of carpet shreds (ratio of length to width), pile distance from the slope crest, relative density of sand, angle of the slope, embedded length, skin friction and the cross-section of the pile. The carpet shred content and aspect ratio were found to influence the lateral resistance of a single pile located near the reinforcing sandy slope. The optimum carpet shred content and aspect ratio of carpet shred were 1·5 and 3 respectively, and with these values a good improvement in lateral resistance of piles was reached.

Numerical simulations and parametric study of SDCM and DCM piles under full scale axial and lateral loads

The new kind of reinforced Deep Cement Mixing (DCM) pile namely, Stiffened Deep Cement Mixing (SDCM) pile is introduced to mitigate the problems due to the low flexural resistance, quality control problem and unexpected failure of DCM pile. The SDCM pile consists of DCM pile reinforced with concrete core pile. Previously, the full scale pile load test and the full scale embankment loading test were successfully conducted in the field. To continue the study on the behavior of SDCM and DCM piles, the 3D finite element simulations using PLAXIS 3D Foundation Software were conducted in this study. The simulations of full scale pile load test consisted of two categories of testing which are the axial compression and the lateral loading. For DCM C-1 and C-2 piles, the clay–cement cohesion, C DCM , and clay–cement modulus, E DCM , were obtained from simulations as 300 kPa and 200 kPa as well as 60,000 kPa and 40,000 kPa, respectively. For the SDCM piles, the simulation results show that increasing length ratio, L core/L DCM , increased the bearing capacity whereas the sectional area ratio, A core/A DCM , has only small effects on the bearing capacity for the axial compression loading. The verified parameters such as the clay–cement cohesion, C DCM , and clay–cement modulus, E DCM , from simulations of axial compression tests were 200 kPa and 30,000 kPa, respectively. On the other hand, increasing the sectional area ratio, A core/A DCM , significantly influenced the ultimate lateral resistance while the length ratio, L core/L DCM , is not significant in the ultimate lateral load capacity when the length of concrete core pile is longer than 3.5 m. In addition, the tensile strength of DCM, T DCM , and concrete core pile, T core , are very important to the lateral pile resistance. The back-calculation results from simulations of tensile strength were 5000 kPa and 50 kPa for the T core and T DCM , respectively.

Effect of pile cap elevation below ground surface on lateral resistance of pile groups-experimental study

This paper presents the results of experimental study on model piles to show the effect of pile cap elevation below the ground surface and pile spacing on lateral resistance of single pile and pile groups driven in sand. Thirty five tests were performed on single piles and 2 x 2, 3 x 3, 4 x 4 pile groups at pile spacing equal to 3<i>D</i> and 5<i>D</i> with pile cap located at different elevation below the ground surface. Five cases for pile cap elevation were considered: case 1, bottom of pile cap in contact with the ground surface; case 2, top of pile cap at the ground surface elevation; case 3, bottom of pile cap below the ground surface at a depth where <i>D_f/t</i> equal 2; case 4, bottom of pile cap below the ground surface at a depth where <i>D_f/t</i> equal 3.33; and case 5, bottom of pile cap below the ground surface at a depth where <i>D_f/t</i> equal 6.67. In all the studied cases, the pile tips located at the same elevation. The results of the tests show that the lateral carrying capacity of single pile and pile groups increase as the pile cap depth below the ground surface, <i>D_f</i>, increases and as the spacing between piles in the group increases.