Experimental Evaluation of Bearing Capacity and Behaviour of Single Pile and Pile Group in Cohesionless Soil (original) (raw)
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A Model Study on Pile Behavior under Inclined Compressive Loads in Cohesionless Soil
International Journal of Engineering Research and, 2015
Pile foundations are extensively used to support various structures built on loose/ soft soils where shallow foundations would undergo excessive settlements or have low bearing capacity. Piles are slender, having high length to width ratio, and are mainly designed to resist axial loads. However, some structures such as high rise buildings, offshore structures, tall chimneys, earth retaining walls are subjected to horizontal or lateral pressure caused by wind force, wave force, traffic movement, earthquake etc. Thus, piles are used as foundation to transmit vertical and lateral loads to the surrounding soil media. In many cases, they may be subjected to inclined compressive loading conditions also. These loads cause lateral and vertical displacements and rotation of the pile cap. These overall behaviors of the piles are estimated from the available conventional theoretical approaches. There are limited experimental studies available on behavior of vertical piles subjected to inclined compressive loads. This paper is an attempt to study the behavior of single pile in cohesionless soil, subjected to varying inclined load until failure with the angle of applied load varying from 0º to 90º from the vertical axis of the pile, through an experimental model study on model mild steel and concrete piles driven into dry river sand. Axial and lateral load carrying capacities of both piles of various slenderness ratios (10, 15, and 20) are found through the loadsettlement diagrams and are compared. The effects of vertical and lateral components of inclined loads on horizontal and vertical displacement of the pile head are discussed. Also, the effects of pile material on the lateral load capacity of piles are studied.
The Bearing Capacity of Large Bored Pile in Cohesionless Soil
Engineering Journal of Research and Development, 2015
Thai geotechnical engineers started using bored piles more than 40 years ago but only in Bangkok, the capital of Thailand in which the soil is strata consists clay and sand. Piling projects outside Bangkok still prefer driven piles than bored piles because of the low cost. Recently bored pile is extensively used, especially in downtown but the pile size is small. The large bored piles were used for the first time in Khon Kaen in which the soil is cohesionless. A 1.2 m diameter bored pile with 40 m long was tested by static method. The frictions along pile shaft were measured by 21 vibrating wire strain gauges installed in pile and then compared with the frictions computed by various methods proposed in the literatures. The method developed by Davies & Chan(1981) gave the best fit. The results show that K and β should not be constant but should vary in direct proportion to strength of the soils around pile.
IJERT-A Model Study on Pile Behavior under Inclined Compressive Loads in Cohesionless Soil
International Journal of Engineering Research and Technology (IJERT), 2016
https://www.ijert.org/a-model-study-on-pile-behavior-under-inclined-compressive-loads-in-cohesionless-soil https://www.ijert.org/research/a-model-study-on-pile-behavior-under-inclined-compressive-loads-in-cohesionless-soil-IJERTV4IS110160.pdf Pile foundations are extensively used to support various structures built on loose/ soft soils where shallow foundations would undergo excessive settlements or have low bearing capacity. Piles are slender, having high length to width ratio, and are mainly designed to resist axial loads. However, some structures such as high rise buildings, offshore structures, tall chimneys, earth retaining walls are subjected to horizontal or lateral pressure caused by wind force, wave force, traffic movement, earthquake etc. Thus, piles are used as foundation to transmit vertical and lateral loads to the surrounding soil media. In many cases, they may be subjected to inclined compressive loading conditions also. These loads cause lateral and vertical displacements and rotation of the pile cap. These overall behaviors of the piles are estimated from the available conventional theoretical approaches. There are limited experimental studies available on behavior of vertical piles subjected to inclined compressive loads. This paper is an attempt to study the behavior of single pile in cohesionless soil, subjected to varying inclined load until failure with the angle of applied load varying from 0º to 90º from the vertical axis of the pile, through an experimental model study on model mild steel and concrete piles driven into dry river sand. Axial and lateral load carrying capacities of both piles of various slenderness ratios (10, 15, and 20) are found through the load-settlement diagrams and are compared. The effects of vertical and lateral components of inclined loads on horizontal and vertical displacement of the pile head are discussed. Also, the effects of pile material on the lateral load capacity of piles are studied.
Experimental investigation of the behavior of pile groups in sand under different loading rates
Geotechnical and Geological Engineering, 2006
The behavior of pile groups in sand under different loading rates is investigated. A total of 60 tests were conducted in the laboratory using model steel piles embedded in a medium dense sand. The model piles have an outside diameter of 25 mm and embedment length of 500 mm. Five different configurations of pile groups (2 • 1, 3 • 1, 2 • 2, 2 • 3, 3 • 3) with center to center spacing between the piles of 3d, 6d and 9d (d is the pile diameter) were tested. The piles were subjected to axial compressive loads under four different loading rates: 1.0, 0.5, 0.1 and 0.05 mm/min. Test results indicated that the axial compressive capacity of pile group increases with the loading rate such that the pile capacity versus logarithm of loading rate data plot approximately along a straight line. The slope of this line increases as the number of piles in a group increases and it decreases by increasing the spacing between piles in a group.
Research Square (Research Square), 2022
According to the current practice, the unit shaft resistance of piles based on ground pa-9 rameters is calculated with the-method or the-method, for total or effective stress con-10 ditions respectively. Indeed, these two methods are included in the prEN1997-3:2021 11 draft standard. And while the physics behind these methods is adequate for calculating the shaft resistance of piles in clays and sands for total and effective stress analysis respectively, the main difficulty in applying the effective stress approach in clays is to esti-14 mate the radial effective stress acting on the pile. In the present paper this is addressed by a proposed earth pressure at-rest coefficient, applicable to cohesive-frictional soils and both horizontal and vertical pseudo-static conditions. Comparison examples show excellent agreement of the analytically derived shaft resistance capacities with the respective numerical ones. Regarding seismic conditions it is noted that, for the case of axially loaded piles the horizontal component of the seismic excitation does not affect the shaft resistance 20 capacity of piles, while the vertical component could be neglected as acting favorably. Finally, it is mentioned that the proposed method is a general − procedure, applicable also for purely cohesive and cohesionless soils.
Theoretical and Actual Bearing Capacity of Driven Piles Using Model Piles in Sand
Applied Mechanics and Materials, 2015
In general, increasing of penetration rate may result in an increased of pile capacity. Occasionally, there were differences between theoretical and actual bearing capacity of the piles. Rate of penetration of pile influenced the pile bearing capacity. The bearing capacity of model pile increased as the rate of loading increased based on pile driving formula. Therefore, the study was conducted to determine the bearing capacity of model piles with different penetration forces based on theoretical method and experimented analysis. Five circular hollow section model piles using pipe pile were used to penetrate into cohesionless soil with different penetration force respectively. The loading for ultimate bearing capacity using theoretical calculation was approximately about 0.163kN.However, referring to the limitation of a laboratory setup, the maximum loading was 0.12kN. Several trials had been initiated but when it reached 0.14kN, the setup was unstable and dangerous to be continued. ...
Evaluation of short piles bearing capacity subjected to lateral loading in sandy soil
International Journal of Civil and Structural Engineering, 2015
Almost all types of piles are subjected to lateral loads. In many cases, however, the applied lateral loads are comparable with gravity loads. Lateral loads and moments are generally induced from wind and earthquake. All piles which are subject to lateral loads are usually divided into two categories: long piles and short piles. The general methods to estimate lateral bearing capacity of piles are based on ultimate bearing capacity and allowable horizontal displacement for short and long piles respectively. Several theoretical methods including Hansen, Broms, Petrasovits, Meyerhof, Prasad and Chari have been proposed to predict lateral bearing capacity of piles in cohesionless soils. All these theories are based on simplified soil pressure distribution assumption along the pile length. In practice the Broms method is most popular, since it is simple and applicable for both of short and long piles. In the present research steel pipes are used as pile in laboratory to evaluate lateral capacity of piles subjected to horizontal loads. Steel model piles, with two different outside diameters of 21.7 mm and 27 mm, wall thickness of 2.4 mm and lengths of 400, 600, 800 mm were used for tests. The soil, in which piles were embedded, was fine sand with friction angle of 33 о and 41.5 о for loose (γ = 13.8 kN/m 3) and medium dense (γ = 15 kN/m 3) states respectively. The sand container was cylindrical in shape with 0.7 m diameter and 1.0 m height. Thin wires, attached to the pile at different levels, were utilized to measure horizontal displacement of piles within the soil. According to theories and experimental test results, the behavior of piles with different length and diameter, embedded in sand was evaluated. A comparison between experimental test results and different theories reveals that Prasad and Chari method is more suitable for estimation of lateral bearing capacity. It is shown that with Increasing the length and diameter of piles and also density of soil, the lateral bearing capacity increases as well, but the soil density is more effective than the other parameters. In addition, it is shown that the location of pile rotation point is not affected by changes in diameter and soil density.
Response of Pile Group under Lateral Cyclic Load in Cohesionless Soil - An Experimental Study
The subject of pile foundation under lateral cyclic load is an age-old problem confronted by Geotechnical Engineers. The environment prevalent in ocean necessitates the piles supporting offshore structures to be designed against lateral cyclic loading resulting from the effects of ocean waves. The quasi-static nature of this type of loading induces progressive deterioration in the interactive performance of the soil-pile system introducing gradual loss in pile capacity associated with increased pile head deflection. In order to understand the effect of lateral cyclic loading on pile group, a new set up associated with motor-gear combinations and other mechanical components, has been developed. With the help of this set up, a series of experiments is carried out with 2 x 2 pile group embedded in well graded dry sand.
Axial load capacity of piles in sand
The axial load capacity of individual piles in cohesionless soils can be estimated at design time using a variety of methods. Because of the difficulties in modeling the process of pile driving, setup , and loading of piles, useful methods are based on case histories cf load tests. Perhaps the most common approach in current use is to specify a soil/pile friction angle, an earth pressure coefficient, a tip bearing capacity factor, and appropriate limits on side shear and end bearing. The various parameters may be made functions of soil classification, relative density, depth, or whatever other variables the investigator thinks are important. In this paper, we compare several methods of analysis that have been in wide use, as well as a method based on continuous functions and a newer method developed by Jardine and coworkers, with measured capacities for untapered piles in tension and compression, in cohesionless soils, and try to draw conclusions about the relative merits of the methods.
Axial resistance of non-displacement piles and pile groups in sand
Rivista Italiana di Geotecnica, 2017
Finite element analyses with a two-surface-plasticity constitutive model and calibration chamber tests with DIC technique are used to investigate the response of non-displacement piles and pile groups to static axial load. The study shows that the mobilized coefficient of lateral earth pressure K increases with increasing relative density D R in sand but deceases with increasing depth (and the resulting greater initial vertical effective stress ' v0). Due to scale effects, a model-size pile develops a much greater unit shaft resistance than a prototype pile under similar conditions. The surface roughness of the piles has a significant impact on the mobilization of shear band and shaft resistance along the pile shaft: up to a threshold value, a greater pile surface roughness generates a thicker shear band and greater unit shaft resistance. Three-dimensional FE analyses on non-displacement pile groups reveals that the interactions between piles in a small pile group are minimal due to strain localization near the piles, and the group efficiency is almost unity at the ultimate load level.