Granular Pile Anchor Research Articles

Review of Analytical Studies on The Failure of Granular Anchor Piles in Expansive Soil

Abstract: Soft ground, characterized by a high content of clay, silt, peat, and loose sand, is generally unsuitable for constructing large structures due to insufficient stability. Ground improvement techniques, such as the use of stone columns (or granular piles), are often implemented in these areas to enhance load-bearing capacity and minimize settlement. The Granular Anchor Pile (GAP) is an advanced version of the stone column that includes an anchor to boost its tensile load-bearing or pullout capacity. In this study, formulations from various authors regarding the pullout capacity of anchors embedded in clayey soils are analyzed to assess the contributions of pile failure and anchor failure to overall GAP failure. The results indicate that GAP failure occurs due to two main factors: 50%–65% of the anchor length failing, and 35%–50% of the pile length failing. This breakdown helps in understanding the role of each component in the overall pullout capacity of GAP

Behavior of Granular Pile Anchors Against Uplift Forces and Heave Reduction: A Review

Behavior of Granular Pile Anchors Against Uplift Forces and Heave Reduction: A Review

Optimum Design of Granular Pile Anchor System for Ground Improvement on Expansive and Shrinking Soil

Optimum Design of Granular Pile Anchor System for Ground Improvement on Expansive and Shrinking Soil

An experimental investigation for pullout response of granular pile anchors embedded in clayey soil

An experimental investigation for pullout response of granular pile anchors embedded in clayey soil

Heave Behavior of Granular Pile Anchor-Foundation System (GPA-Foundation System) in Expansive Soil

Granular Pile Anchor (GPA) is one of the innovative foundation techniques, devised for mitigating heave of footing resulting from the expansive soils. This research attempts to study the heave behavior of (GPA-Foundation System) in expansive soil. Laboratory tests have been conducted on an experimental model in addition to a series of numerical modeling and analysis using the finite element package PLAXIS software. The effects of different parameters, such as (GPA) length (L) and diameter (D), footing diameter (B), expansive clay layer thickness (H) and presence of non-expansive clay are studied. The results proved the efficiency of (GPA) in reducing the heave of expansive soil and showed that the heave can be reduced with increasing length and diameter of (GPA). The heave of (GPA-Foundation System) is controlled by three independent variables these are (L/D) ratio, (L/H) ratio and (B/D) ratio. The heave can be reduced by up to (38 %) when (GPA) is embedded in expansive soil layer at (L/H=1) and reduced by about (90 %) when (GPA) is embedded in expansive soil and extended to non- expansive clay (stable zone) at (L/H=2) at the same diameter of (GPA) and footing. An equation (mathematical mode1) was obtained by using the computer package (SPSS 17.0) for statistical analysis based on the results of finite element analysis relating the maximum heave of (GPA-Foundation System) as a function of the above mentioned three independent variables with coefficient of regression of (R2 = 92.3 %).

A State-of-the-Art Review and Numerical Study of Reinforced Expansive Soil with Granular Anchor Piles and Helical Piles

Expansive soils exist in many countries worldwide, and their characteristics make them exceedingly difficult to engineer. Due to its significant swelling and shrinkage characteristics, expansive soil defies many of the stabilization solutions available to engineers. Differential heave or settlement occurs when expansive soil swells or shrinks, causing severe damage to foundations, buildings, roadways, and retaining structures. In such soils, it is necessary to construct a foundation that avoids the adverse effects of settlement. As a result, building the structure’s foundations on expansive soil necessitates special consideration. Helical piles provide resistance to uplift in light structures. However, they may not fully stabilize foundations in expansive soils. A granular anchor pile is another anchor technique that may provide the necessary resistance to uplift in expansive soils using simpler methods. This review and numerical study investigate the fundamental foundation treatments for expansive soils and the behavior of granular anchors and helical piles. Results indicate that granular anchor piles performed better than helical piles for uplift and settlement performance. For heave performance, the granular anchor and helical piles perform nearly identically. Both achieve heave reductions greater than 90% when L/H > 1.5 and D = 0.6 m.

The efficiency of granular pile anchor foundation system in reducing heave of Irbid expansive clayey soil: An experimental investigation

This study is devoted to investigate the efficiency of granular pile anchor (GPA) in controlling heave of shallow foundations constructing over expansive soils. In this study heave measurements were made on laboratory model footings reinforced with GPAs having different diameter (3 cm, 4 cm and 5 cm) and embedded length (20 cm, 30 cm and 40 cm). The GPAs foundation system was constructed on expansive clay compacted in a steel box 60 cm in diameter and 70 cm in height. The measured percent reduction in heave was found to increase with increasing embedded length and diameter of GPA. The experiments conducted in this study showed that the percent reduction in heave when using GPAs may reach as high as 93 %. A theoretical formulation for the prediction of the percent reduction in heave was developed in this study. A comparison of the predicted percent reduction in heave using the developed formulation with the measured values in this study indicated good agreement and suggested that the proposed formulation in this study can be used to estimate the percent reduction in heave of shallow foundations constructing over expansive soils reinforced with GPAs.

Heave and pullout studies of geogrid-encased granular pile-anchors in expansive clay beds

This paper presents heave and pullout studies of plain granular pile-anchors (GPAs) and geogrid-encased GPAs. Experiments were conducted in California bearing ratio (CBR) moulds and fabricated moulds of size 381 × 381 × 457 mm in expansive clays. The GPA method is an innovative technique developed for reducing heave and improving bearing capacity and pullout capacity. In this study, GPAs were encased in geogrids to augment the engineering performance of the system. Tests were conducted in CBR moulds and fabricated larger moulds to study and compare the heave and pullout behaviour of plain GPAs and geogrid-encased GPAs. The results indicated that the clay beds reinforced with geogrid-encased GPAs showed better heave and pullout behaviour. Heave decreased by 90.8% and 92.5%, respectively, in the case of plain and geogrid-encased GPAs installed in the CBR moulds and by 95.12% and 98.3% in the case of plain and geogrid-encased GPAs installed in fabricated large moulds. Pullout load on geogrid-encased GPAs in CBR moulds improved by 42.17% over that on plain GPAs and pullout load on geogrid-encased GPAs in the fabricated large moulds improved by 52.25% over that on plain GPAs.

Model Tests on Granular Pile Anchor and Helical Anchor: A Comparative Study

Model Tests on Granular Pile Anchor and Helical Anchor: A Comparative Study

Experimental Study on the Factors Influencing the Performance of Geogrid Encased Granular Pile Anchor Installed in Cohesionless Soils

Experimental Study on the Factors Influencing the Performance of Geogrid Encased Granular Pile Anchor Installed in Cohesionless Soils

Effect of load inclination on the uplift capacity of the granular anchor pile foundation in cohesive soil

Effect of load inclination on the uplift capacity of the granular anchor pile foundation in cohesive soil

An experimental investigation for pullout response of a single granular pile anchor in clayey soil

The granular pile anchor foundation is an effective and economical foundation system to counter the pullout forces exerted in case of transmission towers or foundations in expansive soil. The pullout tests were performed to study the behaviour of a single granular pile anchor in the clayey soil bed. Tests were conducted in a steel tank of 1 × 1 × 1 m size with the help of loading frame arrangement. The pullout load required for upward movement equal to 10% diameter was considered as the pullout capacity of the granular pile anchor. In the parametric study, length and diameter of the granular pile anchor were varied to examine their effect. Number of anchor plates was also varied in few tests. The pullout capacity enhanced with an increase in the diameter and length to diameter ratio. The effect of the length to diameter ratio was appreciable up to the value of 10. However, no significant effect was found in the cases of multiple anchor plates. A relationship is proposed to predict normalized pullout capacity.

An experimental and numerical comparative study on the uplift capacity of single granular pile anchor and rough pile in sand

ABSTRACT Granular pile anchor (GPA) is a relatively new foundation technique that is found to be effective in resisting uplift forces in expansive soils. GPA can be utilized as an economical substitute to other methods to resist the uplift loads in sandy soils. In this study, the performance of GPA and rough piles installed in the sand bed under uplift was examined using laboratory-scale model tests and numerical modelling under field-scale conditions. The laboratory-scale model tests were performed on GPA and rough pile installed in loose, medium dense, and dense sand beds by varying the embedment ratio. A numerical study was also done to check the findings from the experimental study and GPA suitability under field-scale conditions. The laboratory-scale and numerical study revealed that GPA performs better than bored pile under uplift force and can be used as an effective ground anchoring alternative.

An Experimental Study on heave and Uplift Behaviour of Granular Pile Anchor Foundation System

Several innovative ground improvement techniques were presented by various researchers throughout the globe for modification of the existing poor soils. Granular Pile-Anchors (GPA) were found to be more promising in resisting the heave behavior of the expansive soils in recent times. The engineering behavior of the soil can be improved by this technique apart from resting the swell. This technique is a modification on the existing granular pile technique with an anchor plate beneath the granular pile that is connected to the foundation by means of an anchor rod or cable. Numerous scale model tests were discussed in this paper to understand the heave and pull-out behavior of Granular Pile-Anchor Foundation (GPAF) system. The effect of spacing was studied by using two granular piles at varied spacing. It was observed that the swell potential was reduced to about 68.09% for 50mm dia GPA, compared to the virgin expansive soil. The swell potential was found to be further reduced at twice the diameter of the pile spacing. The pull-out capacity was found to be increased by about 393% by providing a 50mm diameter GPA in the expansive soil.

Analytical study on failure of granular anchor pile

The soft grounds are not suitable for construction of huge structures as the soil may contain high percentage of clays, silts, peat and loose sands. Ground improvement technique such as stone columns (granular pile) is utilized in such areas to improve load bearing capacity and reduce settlements. Granular Anchor Pile (GAP) is a modified form of stone column in which an anchor is incorporated to improve the tensile load carrying capacity or pullout load. In the present study formulation given by various authors for finding pullout capacity of anchors embedded in clayey soil are considered and studied in order to determine the contribution of percentage (%) length of pile failure & % length of anchor failure in GAP failure. The pullout capacity of GAP is obtained at 50%–65% length of anchor failure, 35%–50% length of pile failure.

Foundation Failures Mitigation under Expansive Clay by Using Granular Pile Anchor System

Expansive soils are found in typical areas in the world especially in arid and semi-arid regions. The problems associated with this type of soil drive geotechnical engineers to invent new technologies as remediation’s such as physical and chemical treatments. Innovative foundation techniques were also suggested for remedying the swell-shrink problems of the expansive soil. The granular pile anchor (GPA) is relatively a more favorable technique indebted to its cost-effective, easy and fast to assemble and most importantly was found to be more efficient in remedying the expansive soil. Despite the extensive studies on the expansive soil remedies, yet the granular pile anchor system requires more comprehensive and in-depth investigations. This study is aimed at developing a model with granular piles of various length and diameter extended to the stable zone to investigate the heave and uplift pressure in the expansive soil. For this purpose, experimental and numerical analysis were conducted in a small and in a full scale model respectively. A significant improvement was attained in heave reduction and an increment of uplift capacity. The findings also show that heave decreased significantly when the length and diameter of the GPA increases while the uplift capacity increased. However, it was noted that the extension of length to the stable zone resulted in insignificant changes. Therefore, it can be concluded that the maximum length of 6 m is the ideal length for GPA with different diameters according to foundations design requirement for this particular type of soil.

Improving expansive clay beds with granular pile anchors (GPAs) and geogrid-encased GPAs

Granular pile anchors (GPAs) are an innovative foundation technique developed for reducing the heave of expansive clay beds. Other engineering characteristics of expansive clay beds have also been found to improve through GPA reinforcement. This paper presents experimental data on heave, compressive load response and pullout response of expansive clay beds reinforced with plain GPAs and geogrid-encased GPAs. The heave of the expansive clay beds decreased by 95·12% on the installation of plain GPAs and it further decreased (by 98·3%) in the case of geogrid-encased GPAs. Plate load tests were conducted on unreinforced expansive clay beds and clay beds reinforced with plain GPAs and geogrid-encased GPAs for a comparative study. Similarly, pullout tests were conducted on clay beds reinforced with plain GPAs and geogrid-encased GPAs. The clay beds reinforced with geogrid-encased GPAs resulted in a higher load capacity in compressive as well as pullout tests than the beds reinforced with plain GPAs.

Experimental and Numerical Studies on Pull-out Behavior of Granular Anchor Pile Foundation Embedded in Sandy Soil

The granular anchor pile foundation (GAPF) is an improved foundation technique used to withstand compressive as well as tensile forces and effectively reduce the settlement of soil. In this paper, the behavior of a GAPF system was studied in sandy soil. Pull-out load tests were conducted on GAPF by varying different parameters viz. length of pile (250 mm, 350 mm and 450 mm), L/D ratio (7.5, 10 and 12.5) and group of piles (spacing 2D, 2.5D and 3D). The test results indicate that the pull-out capacity decreases with the increase in L/D ratio from 7.5 to 12.5. The group effect resulted in increased uplift load in comparison to that of a single GAP tested. Finite element analysis using PLAXIS 3D software had also been carried out to validate the results of physical model tests. On comparison of numerical and model study results, a reasonable agreement has been found.

Uplift behaviour of axial granular pile anchor encased with geogrid in cohesionless soil

Purpose The purpose of this paper is to provide a cost-effective foundation technique for the design of foundations of transmission towers, heavily loaded structures, etc. Design/methodology/approach Experimental model tests are conducted in a model test tank to find out the effect of length and diameter of geogrid encased granular pile anchors, the relative density of sand and the angle of inclination of the pile from the vertical on uplift behavior of granular pile anchors. Findings The uplift capacity of the geogrid encased granular pile anchor increased with increasing length and diameter of granular pile anchor. Further, increasing the relative density of surrounding soil increased uplift capacity of geogrid encased granular pile anchor system. Moreover, increasing the angle of inclination of loading also increased uplift capacity of whole system. Thus, the proposed system can be effectively used in field for further applications. Originality/value The paper is helpful for the engineers looking for cost-effective foundation techniques for heavily loaded structures.

Ground improvement using granular pile anchor system: resistance to heave and uplift pressure

<span lang="EN-GB">Expansive soil is found in many parts of the world where its major drawback is its expansion and shrinking property upon moisture absorption and drying during alternation of rainy-dry seasons. Due to its swelling-shrinkage repeated process, fatigue and distress cause crack to structures. Granular pile anchor (GPA) system is a pioneering technique that is utilised in reinforcing these expansive soils. Granular pile anchor (GPA) system is a pioneering technique that is utilised in reinforcing expansive soils. The GPA provides tensile resistance which arrest the exerted upward forces and hence reducing heave. Previous investigations have only focused on load-displacement relationships by utilizing the pull-out technique. In this technique, an external force pulls the GPA and the corresponding displacements are recorded. The results provide indication of the GPA resistance to the applied force. However, in real conditions the heave and expansion forces were developed as a result of the pressure caused by the water absorption which pushes the entire soil bed in the upward direction along with the GPA. Therefore, this paper is aimed to explore this concept by carrying experimental and numerical investigations on a small scale model for a single pile with a diameter of 4 cm, with lengths of 20 and 40 cm. Ultimately, the reinforced soil exhibits reduction in upward force and heave compared to the unreinforced soil. Also, verifications for the testing shows that the relationship between the upward force and heave exhibits almost linear relationship for both experimental and numerical investigations. Therefore, shallow foundations incorporated with a GPA system proves to effectively lessen the heave that occurs in expansive soils which in turn can solve problems for constructions.</span>