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The undrained pullout capacity of granular pile anchors (GPA) can be sensitive to changes in soil shear strength. Researchers are intrigued by evaluating spatial variations in soil behavior in geostructures. However, there is a dearth of research on the effect of spatial soil variability on long GPA pullout capacity. The present study conducted probabilistic analyses of GPA pullout capacity using the local average subdivision method (LAS), considering the spatial variation of soil shear strength and its correlation with the soil elastic and shear modulus. The finite-difference method was used to predict GPA behavior in each random field realization to determine the probability of failure using the Monte Carlo method. The results demonstrated that consideration of GPA's friction angle as a random parameter had negligible effects on pullout capacity. Moreover, the surface heave was limited by increasing the length/diameter ratio to more than 10. The pullout capacity of the GPA decreased by 30% due to a higher horizontal to vertical correlation length exceeding 5. In addition, the safety factor for the empirical equation obtained 1.5 and 2 for coefficient of variation higher and less than 0.2 in an isotropic random field, respectively. Finally, the concrete granular pile anchors were proposed to increase the pullout capacity and reduce corrosion effects on the anchor bar. [ABSTRACT FROM AUTHOR]

Abstract 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.

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Several foundation techniques, such as belled piers, under-reamed piles, helical piles are adopted in expansive soils to avoid the problem posed by its swelling nature. In recent years, the granular pile anchor (GPA) technique has been in practice for resisting the uplift of foundation caused by expansive clay beds. Model and prototype studies on GPA revealed that swelling of expansive clay beds can be effectively controlled by the GPA technique. This paper presents a comparative study on the behaviour of GPA and helical pile anchors (HPAs) in expansive soil subjected to swelling. The data presented in this paper pertain to model tests of clay beds reinforced with varying number of GPAs (N = 0, 1, 2 and 3). Similarly, the model tests were conducted on clay bed reinforced with varying number of HPAs (N = 0, 1, 2 and 3). Tests were also conducted by varying the number of helix. Test results shows that the heave (mm) decreases with an increase in the number of GPAs. Similarly, the heave decreases with an increase in the number of HPA. Further, heave (mm) also decreased with increase in the number of helix. The resultant heave reduction is found to be more in case of expansive soil reinforced with GPA when compared to expansive soil reinforced with helical pile. [ABSTRACT FROM AUTHOR]

Granular piles/stone columns are one of the most commonly preferred ground engineering systems for improving a variety of weak soils, such as soft clays, loose sands, waste fills, and ash ponds. They are installed using a range of techniques, namely vibro compaction, vibro replacement, composer method, rammed stone columns, and geopiers, based on on-site conditions and availability of machinery. Granular piles improve the ground by densification especially in loose sands, by reinforcement in case of waste fills and ash ponds, by reinforcement and consolidation in case of soft clays, and mitigate damages from liquefaction by functioning as drains. The paper presents a critical review of developments related to granular piles encompassing recent analytical, experimental, numerical studies, and field investigations of their compressive, uplift, and seismic responses. Three well-documented case histories of an embankment, a mechanically stabilized earth wall, and a liquid storage tank on granular pile-engineered ground are presented to illustrate their versatility. [ABSTRACT FROM PUBLISHER]

The use of granular pile is one of the effective and efficient methods of ground improvement because of its ability in improving the bearing capacity and reducing the settlement of different soft soils. Conventional granular piles cannot be used as tension members to offer resistance under pull out loads. Granular Pile Anchor (GPA) is one of the recent ground improvement technique in devised for resisting pull out forces. In a granular pile anchor, the footing is anchored to a mild steel plate placed at the bottom of the granular pile through a reinforcing rod or a cable. The main objective of the present study is to investigate the effect of relative density of fill material, granular pile diameter on the pull capacity of the granular pile anchor and the comparison of encased and non-encased granular pile has been done. The laboratory model tests using GPAF system revealed that the pull-out capacity of the granular pile anchor increased with increasing relative density of the granular material. There was a maximum percentage increase of 35% in the ultimate load when the relative density was increased from 50 to 70% for 50 mm diameter pile. It was also revealed that the pull-out capacity of the granular pile anchor increased with increasing diameter of the granular pile anchor. The increase of 35% was also obtained when the diameter was increased from 30 mm to 50 mm at a relative density of 70%. For the encased pile, maximum increase in the percentage ultimate pullout load was obtained for pile diameter of 30 mm and it was about of 13.2%. [ABSTRACT FROM AUTHOR]

Soft soils need to be improved to make them suitable for construction. Granular Piles (GP) are effective and economical solutions to improve the behavior of the soft soil by increasing bearing capacity, reducing settlements due to reinforcement. Granular piles due to their inherent advantage are effective in countering swell pressures from expansive clays. Installation process of GPs densifies the ground adjacent to GPs inducing additional benefit. Advantages of GP to resist compressive and shear loads are well documented and attempts to extend its utility to resist tensile loads is being investigated. An anchor is placed at the base of granular pile and attached to the footing by a cable or rod which transfers applied pullout force to the bottom of GP. Such an assembly is termed as 'Granular Pile Anchor' (GPA). Experimental study on laboratory models of GPA in clayey sand for different compaction properties lead to different undrained shear strength and stress - strain characteristics. Pullout resistance derived from pile capacity is mainly affected due to the variation in undrained shear strength with depth. Results are presented as variations of load - displacement responses and failure patterns for three different undrained shear strength values. [ABSTRACT FROM AUTHOR]

Laboratory and field studies have shown that granular pile-anchor foundations (GPAF) are a promising foundation system that can be used to reduce the detrimental effects of reactive soils. This paper presents results from finite element analyses undertaken on granular pile-anchor foundations in a reactive soil using PLAXIS software. The study investigated the ability of a single pile to resist forces induced by both heave and shrinkage. The results confirmed the efficiency of the granular pile-anchor foundations in resisting heave induced by moisture gain. However, in order to resist shrinkage, the GPAF system has to be reinforced with geofabric to assist resisting bulging of the granular pile into the surrounding soil. The analyses showed that success of the GPAF in heave resistance may be adversely influenced by the high stiffness of the interface, which requires only small relative movement to mobilize full resistance. The efficiency of the GPAF system increases with the ratio between the pile diameter and supported footing. Using a group of piles instead of a single pile under a footing can reduce the efficiency of the GPAF system. [ABSTRACT FROM AUTHOR]