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Granular anchors are a relatively new concept in ground engineering with relatively little known regarding their load–displacement behaviour, failure modes, ultimate pullout capacity, and also potential applications. A granular anchor consists of three main components: a base plate, tendon, and compacted granular backfill. The tendon is used to transmit the applied load to the base plate, which compresses the granular material to form the anchor. A study of the load–displacement response and ultimate pullout capacity of granular anchors constructed in intact lodgement till and made ground deposits is reported in this paper. Parallel tests were also performed on cast in situ concrete anchors, which are traditionally used for anchoring purposes. A new method of analysis for the determination of the ultimate pullout capacity of granular anchors is presented and verified experimentally, with the dominant mode of failure controlled by the column length (L) to diameter (D) ratio. Granular anchors with L/D > 7 principally failed by bulging whereas short granular anchors failed on shaft resistance, with the latter mobilizing similar pullout capacities as conventional concrete anchors.

Ground treatment of soft soil deposits by prefabricated vertical drains (PVDs) is a common practice in geotechnical engineering. The PVDs accelerate the consolidation process and help to rapidly increase the strength and stiffness of soil. Certain operational problems, such as clogging, are inherent to PVDs. The fine particles in the soil may become entrapped within the fibers of the filter, i.e. the geotextile, surrounding the PVD. If the pores of the filter sleeve are clogged, the discharge capacity of the PVD reduces and, consequently, the consolidation process is impeded. In this paper, a numerical study is carried out to investigate the effect of PVD geotextile filter clogging on the rate of soil consolidation. The rate of consolidation decreases with increasing clogging and is a function of the location of the clogged area in the PVD. In the parametric study, the PVD was sequentially clogged and its effect studied. The effect of smear was also included in the analysis.

Granular piles can resist only compressive and shear loads owing to their inherent nature. By a simple modification of providing a pedestal/geogrid at the bottom and attaching a cable to the same, they are made to resist pullout/uplift forces. This paper presents an analysis of granular pile anchor (GPA), considering it and the in situ soil to behave linearly and the in situ ground to be semi-infinite. A parametric study presents results in the form of variations of normalised shear stress, displacement influence coefficient and axial uplift force with depth with relative stiffness factor. Two methods for the estimation of deformation moduli of the GPA and the in situ soil are proposed. Based on the estimated values of the moduli, the displacements of GPA were estimated and the results compared with test results of Kumar (2002). The predicted displacements compare well with the measured ones.

This paper describes an innovative design of a newly developed large test setup for testing the performance of footings supported on soft clay reinforced with granular columns. This advanced testing method is used to examine the settlement of footings supported on granular columns. Two important features of the equipment are ͑a͒ the axial loading system which allows samples to be consolidated under K o condition while the load is applied onto a small foundation area of the sample, and ͑b͒ a relatively large sample size of 300-mm diameter and 400-mm high. The system is also equipped with pressure cells located beneath the footing and top cap to measure the pressure distribution with respect to foundation displacement and a lateral strain gage to monitor boundary effects. This paper reports on some of the early findings from the preliminary tests carried out using this equipment. Samples for testing were prepared by consolidating kaolin slurry in a large one-dimensional consolidation chamber. The granular columns were installed using the replacement method by compacting crushed basalt ͑uniformly graded with 90 % between 1.5-2-mm particle sizes͒ into a preformed hole. The preliminary tests have yielded promising results, validating the functionality of the equipment and support the prospect of increasing the knowledge with respect to settlement response and design of a footing supported on granular columns.

Laboratory-based research studies and full-scale evaluations of the behaviour of ground improved with granular columns are ample regarding bearing capacity, but limited in respect to the settlement response. This paper presents a laboratory model study that considers the settlement performance of isolated pad footings bearing on reinforced sand deposits under the influence of a fluctuating groundwater table. This is a particularly onerous condition for loose sand deposits in coastal areas, which may undergo significant collapse settlement over time. Loose and dense experimental sand beds were constructed, and the performance of rigid footings under a maintained load and bearing on sand incorporating different column configurations was monitored under cycling of the water table over a period of 28 d, with one filling/empting cycle every 18 h. It was found that settlement, while greatly reduced compared with that for unreinforced footings, was ongoing, and typically occurred at a much greater rate for loose sand than for dense sand. Also, settlement rates were slightly higher for fully penetrating than partially penetrating columns, and also for footings reinforced by a column group rather than a single column. This was attributed to the migration of sand grains into the larger column voids.

Granular piles improve the behavior of the ground by increasing bearing capacity, reducing settlements, accelerating consolidation, and mitigating liquefaction related damages by reinforcement and densification effects. GPs due to their inherent nature can resist compressive and shear loads but not tensile ones. Granular piles can be made to resist pullout or uplift forces by placing an anchor at the base and attaching the same by a cable or rod to the footing to transfer the applied pullout forces to the bottom of the GP. Such an assembly is termed a Granular Pile Anchor (GPA). Analyses for displacements in granular pile anchors in groups of two, three or four, are presented based on Poulos and Davis (1980) for rigid piles. Results are presented as variations of interaction factor, 'α' with spacing s/d and relative stiffness factor, K. The results compare well with those of Poulos and Davis for rigid piles. The principle of superposition is validated for groups of 3 and 4 GPA.

Foundations of structures like earth retaining structures, abutments, waterfront structures, machines, oil/gas platforms in offshore areas, etc. are subjected to eccentric and/or inclined loading. Response of a rectangular foundation on the surface of the ground modeled as non-linear Winkler model is evaluated for its dependence on eccentricity of load, stiffness and ultimate stress of the ground. The ultimate bearing capacity of eccentrically loaded foundation is not only a function of width of the footing and eccentricity of load but also depends on the compressibility of the foundation soil. The ultimate load ratio of eccentrically loaded foundation with respect to concentrically loaded foundation is estimated based on both Meyerhof's method and the proposed approach. The predicted values of ultimate load ratio compare well with the measured ones.