A series of laboratory model tests have been performed to study the behaviour of geocell-reinforced sand beds under strip loading. The strain in geocell walls, pressure transmitted to the subgrade soil, and deformations in the subgrade were measured during the tests to develop an understanding of the mechanism of geocell reinforcement. The pattern of strain variation in the geocell walls indicates that the geocell mattress behaves as a composite beam supported by the subgrade soil. The load dispersion in the geocell mattress is found to be governed by factors such as geometry of the geocell layer and its placement position under the footing. © 2007 NRC Canada.

K Rajagopal

Department Of Civil Engineering

N. R. Krishnaswamy

Deformation

Mechanical testing

Pressure effects

sand

Soil structure interactions

Strain

Walls (structural partitions)

GEOCELL WALLS

SAND BEDS

soil reinforcement

Strip loading

Composite beams and girders

Geosynthetics

LOADING TEST

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Behaviour of geocell-reinforced sand beds under strip loading

Canadian Geotechnical Journal

This paper presents the results of laboratory model tests carried out to study the relative performance of different forms of reinforcement (i.e. geocell planar and randomly distributed mesh elements) in sand beds under strip loading. The results demonstrate that geocell reinforcement is the most advantageous soil reinforcement technique of those investigated. With the provision of geocell reinforcement, failure was not observed even at a settlement equal to about 45% of the footing width and a load as high as eight times the ultimate capacity of the unreinforced soil, whereas, with planar reinforcement, failure took place at a settlement of about 15% of the footing width and a load of about four times the ultimate capacity of the unreinforced soil. For the case with randomly distributed reinforcement mesh, failure was recorded at a load of about 1.8 times the ultimate capacity of the unreinforced soil and at a settlement of about 10% o of the footing width. © 2004 Thomas Telford Ltd.

Geosynthetics International

Performance of different geosynthetic reinforcement materials in sand foundations

The results from laboratory model tests on strip footings supported by geocell reinforced sand beds with additional planar reinforcement are presented. The test results show that a layer of planar geogrid placed at the base of the geocell mattress further enhances the performance of the footing in terms of the load-carrying capacity and the stability against rotation. The beneficial effect of this planar reinforcement layer becomes negligible at large heights of geocell mattress. © 2001 Elsevier Science Ltd. All rights reserved.

Geotextiles and Geomembranes

Strip footing on geocell reinforced sand beds with additional planar reinforcement

This paper presents the results from laboratory-model tests on a strip footing supported by a sand bed reinforced with a geocell mattress. The parameters varied in the testing program include pattern of geocell formation, pocket size, height and width of geocell mattress, the depth to the top of geocell mattress, tensile stiffness of the geogrids used to fabricate geocell mattress and the relative density of the sand. With the provision of geocell reinforcement, failure was not observed even at a settlement equal to 50% of the footing width and a load as high as 8 times the ultimate bearing capacity of the unreinforced sand. Based on the model test results, the depth of placement and the dimensions of the geocell layer for mobilising maximum bearing capacity improvement have been determined. In addition to the tensile strength of reinforcement, the aperture size and orientation of ribs of the geogrid used to fabricate geocell mattress must be taken into account while evaluating its contribution to the improvement in the performance. © 2001 Elsevier Science Ltd. All rights reserved.

Bearing capacity of strip footings supported on geocell-reinforced sand

Anchors of very large uplift capacities are required to support offshore structures at great water depths. The capacities of plate and mushroom type anchors are generally estimated based on the shape of rupture surface. An attempt has been made in the present investigation to delineate the rupture surfaces of anchors embedded in submerged and dry sand beds at various depths. The results exhibited two different modes of failure depending on the embedment ratio, namely, shallow and deep anchor behaviour. The load-displacement curves exhibited three- and two-phase behaviours for shallow and deep anchors, respectively. Negative pore water pressures recorded in submerged sand also exhibited variation similar to that of pullout load versus anchor displacement.Anchors of very large uplift capacities are required to support offshore structures at great water depths. The capacities of plate and mushroom type anchors are generally estimated based on the shape of rupture surface. An attempt has been made in the present investigation to delineate the rupture surfaces of anchors embedded in submerged and dry sand beds at various depths. The results exhibited two different modes of failure depending on the embedment ratio, namely, shallow and deep anchor behaviour. The load-displacement curves exhibited three- and two-phase behaviours for shallow and deep anchors, respectively. Negative pore water pressures recorded in submerged sand also exhibited variation similar to that of pullout load versus anchor displacement.

Ocean Engineering

Anchors in sand bed: Delineation of rupture surface

The technique of reinforcing soil for foundation improvement is well established. This paper addresses the aspect of settlement of reinforced sand foundations, where the major part of the existing work deals with the aspect of bearing capacity. A detailed analysis is made paying individual attention to soil, reinforcement, and the interface between the two. A three-dimensional, nonlinear finite-element analysis is presented that uses a three-dimensional, nonlinear soil-reinforcement interface friction element, along with other three-dimensional elements to model the system. The results of the analysis are compared with those from tests conducted in the laboratory and are found to be in good agreement. The studies lead to a better understanding of the behavior of the system at different stages of loading.

Fulltext

Journal of Geotechnical Engineering

Settlement of reinforced sand in foundations

Journal	Canadian Geotechnical Journal
ISSN	00083674
Open Access	No