The failure wedge in dense sand bed under strip loading of width （B） is found to be extended around 3B on either side of the footing center line and a depth of about 1.1B from the footing base （Chummar 1972）.The depth and the width of foundation soil bed,in the present tests, were 7B and 13B, respectively.In view of this, it could be said that the tank used in the current investigation is considerably large enough and is not likely to interfere with the zone of deformation of soil and geocell and hence the experimental results.
The model tests were performed at relative densities of 30,40,50, 60,and 70%.These relative densities were achieved in the test tank through pluviation using a calibrated sand raining device.At prescribed depth （as per test configuration）,the sand raining was temporarily ceased and the geocell reinforcement was placed on the surface of the sand.After this, sand raining was continued.The accuracy of sand placement and consistency of the placement density were checked during raining by placing small aluminum cans with known volumes at different locations in the test tank. The difference in densities measured at various locations in the test tank was found to be less than 1%.
Fig. 1. Details of geometry of geocell-reinforced foundation systemand instrumentation
Fig. 2. Bearing pressure versus footing settlement for unreinforcedfoundation bed
A hand operated hydraulic jack, supported against a reaction frame, was used for applying vertical load on the test footing.The loads transferred to the footing were recorded through a proving ring installed between the hydraulic jack and a ball bearing over the footing.In the absence of a clear-cut failure, the footing was loaded until a maximum settlement of 50 mm.Footing settlements （s) were measured through two dial gauges ( and ; see Fig. 1)placed on either side of the center line of the footing.The deformations (heave/settlement) of the soil surface on either side of the footing were also measured by dial gauges, placed through small plastic plates on the fill surface,at a distance of 2B from the edge of the footing ( and ; see Fig.1).The footing settlement (s) and the surface deformation data reported
here are the average values of the readings taken at the two different points and are presented in nondimensional from as s /B (%) and (%), respectively.
The strain in the geocell reinforcement was measured through electrical resistance-type-strain gauges of 10-mm length, 2-mm width,120- resistance, and 2.1 gauge factor.These strain gauges were mounted on the rib of the geogrid,serving as the transverse member,in the geocell reinforcement (Fig.1).At each gauge location,the geogrid surface was mildly roughened using sand paper and then wiped clean with a clean cloth and neutralizing solution. Next,the strain gauges were pasted with a quick setting adhesive (cyanoacrylate).The lead wires,connecting the strain measuring instrument,were soldered to the strain gauge wires through a strain relief pad.It should be mentioned here that unlike the planar reinforcement system,the geogrid in the geocell reinforcement is held by bodkin joints，which arrests the cross plane bending.In the absence of cross plane bending,most of the strain induced in the reinforcement is due to the in-plane axial deformation.Therefore for measurement of in-plane axial strain in the geocell walls,single strain gauge was used at each instrumentation point.To nullify the effects due to temperature, each strain gauge was supplemented by dummy gauge. The strains were measured using a digital strain meter that uses Wheatstone bridge principle.The strain measurements are reported at normalized footing load levels bearing pressure ratio (BPR).The BPR is defined as the ratio between the footing pressure with geocell and the ultimate footing pressure in test on unreinforced soil at 70% relative density. The compressive strains are reported with sign and the tensile strains with sign. 格室加筋砂土地基土相对密度性能的影响英文文献和中文翻译(2):http://www.youerw.com/fanyi/lunwen_56448.html