Bamboo Grid Research Articles

Experimental and Analytical Studies on Soft Clay Beds Reinforced with Bamboo Cells and Geocells

This manuscript deals with the experimental and analytical studies carried out to explore the possibility of using naturally available bamboo to increase the bearing capacity of the soft soil. In order to extract the additional confinement effect on the soil, 3 dimensional-cells are formed from the locally available bamboo known as bamboo cells. The performances of the bamboo cells are compared with the commercial geocells. Further, a planar reinforcement in the form of bamboo grid was provided at the base of bamboo cells and the performance was compared with the clay bed reinforced with the combination of geocell and geogrid. The results of the laboratory plate load tests suggested that the ultimate bearing capacity of the clay bed reinforced with combination of bamboo cell and bamboo grid was about 1.3 times higher than the geocell and geogrid reinforced clay beds. In addition, a substantial reduction in the settlement was also observed. An analytical model was also proposed to estimate the bearing capacity of the clay bed reinforced with bamboo cells and bamboo grids. The model comprised of three mechanisms, namely the lateral resistance effect, vertical stress dispersion effect and membrane effect. The results predicted from the analytical model were found to be in good agreement with the experimental results. In a larger perspective, this study proposes a cost effective ground improvement technique in soft soils as an alternative to geocells and geogrids.

Behavior of Reinforced Stone Dust Walls Under Strip Loading

Abstract Stone dust, a by-product of metal aggregate quarries, is utilized successfully as an alternative material for sand in concrete, as road material, and in bearing-capacity problems. An attempt has been made in this study to utilize stone dust as backfill material. A series of tests were performed on laboratory models of reinforced stone dust walls under strip loading. Manually prepared grids of natural material bamboo and commercially available steel grids were used as reinforcement. Bamboo grids and steel grids were used as strips, concrete segmental blocks were used as facia, and the behavior of walls was studied under strip loading by varying lengths of reinforcement and vertical spacing between the reinforcement layers. Bamboo grids in strip form are good enough to resist high failure surcharge pressures, and the results are comparable with the steel grid–reinforced stone dust walls. Geofoam blocks having a density of 0.12 kN/m3and thicknesses of 5 mm, 15 mm, and 20 mm were placed behind the segmental concrete facia blocks to study their effect on lateral displacement of facia and surcharge at failure. The results show a good trend in reducing the facia displacements and increasing the surcharge at failure as the thickness of the geofoam blocks placed behind each facia unit is increased. Finite-element simulation of the model tests was carried out using commercially available Plaxis 2D software. Stone dust was modeled as linear elastic perfectly plastic material with Mohr–Coulomb failure criteria, and bamboo and steel grids were modeled as elastic material. The finite-element simulation results for failure patterns, horizontal displacement of facia, and settlement of the backfill showed reasonable agreement with the experimental results.

Use of Bamboo in Soft-Ground Engineering and Its Performance Comparison with Geosynthetics: Experimental Studies

The results of the laboratory investigation performed on clay beds reinforced with natural (bamboo) and commercial (geosynthetics) reinforcement materials are reported in this paper. To use bamboo effectively, three-dimensional cells (similar to geocells) and two-dimensional grids (similar to geogrids) are formed using bamboo (termed bamboo cells and bamboo grids, respectively). The performance of clay beds reinforced with bamboo cells and bamboo grids is compared with that of clay beds reinforced with geocells and geogrids. The bearing capacity of the clay bed increased by six times when a combination of geocell and geogrid was used. The ultimate bearing capacity of the clay bed reinforced with bamboo cell and bamboo grid was found to be 1.3 times more than that of clay bed reinforced with geocell and geogrid. In addition, substantial reduction in the footing settlement and the surface deformation was observed. The tensile strength and surface roughness of bamboo were found to be nine times and three times, respectively, higher than geocell materials. The bamboo was treated chemically to increase its durability. Although the performance of bamboo was reduced by 15-20% after the chemical treatment, its performance was better than its commercial counterparts. (C) 2014 American Society of Civil Engineers.

Effect of reinforcement on stress–strain behavior of stone dust

Stone dust is rock particles formed when huge rocks are broken into smaller sizes for use as construction material. Enormous amount of stone dust is generated as waste product at quarry sites all over India. Proper utilization of this waste is needed in a developing country like India. To check the suitability of this waste product in geotechnical engineering applications, a series of triaxial tests have been performed on stone dust without and with reinforcement. Reinforcements used were bamboo grid (BG) and steel grid (SG). Circular reinforcement grids of diameter 55 mm were used and placed in the triaxial specimen in four different arrangements as: one layer at center, two layers each at 1/3rd height, three layers each at 1/4th height, and two layers with one each at top and bottom of specimen. For all cases, BG reinforced specimen corresponded to higher peak deviator stress and shear strength parameters compared to that with SG. Finite element simulation is carried out with Plaxis 2D software, the results obtained show good agreement with the experimental results.

BEHAVIOUR OF MINE WASTE AS REINFORCED SOIL

Mining in Goa is done by open cast method, which gives rise to huge quantity of mining waste that occupies space and forms a source for series of problems. The enomerous amount of mine waste dumped around the regions of mining activity need to be reused constructively. Hence, if the mine waste is studied for its use as a reinforced soil, then burning issue of environmental pollution caused by mining dumps lying unprotected and unstabilized can be tackled to a certain extent. Also, it will be a step towards finding an alternative material for cohesionless soil in reinforced soil construction. In this study an attempt is made to check the suitability of soil from one of the mining dumps in Goa to be used as reinforced soil. The mine waste soil samples are studied for its compressive strength and shear strength behaviour by conducting two types of tests, unconfined compressive strength test and triaxial tests on unreinforced and reinforced soil samples. The reinforcement used in the form of a grid made from natural material bamboo. The bamboo grid reinforcement is placed in one, two and three layers, for studying the effect of reinforcement on compressive strength, shear strength parameters, stiffness and modes of failure of mining waste soil. The results of the tests on mining waste show improvement in strength as a reinforced soil mass.

Interaction between cohesive-frictional soil and various grid reinforcements

A total of 52 large-scale laboratory pullout and 24 large-scale direct-shear tests were conducted to investigate the interaction behavior between the different reinforcements and cohesive-frictional soil. The reinforcements used were steel grids, bamboo grids, and polymer geogrids. The backfill material used was locally available weathered Bangkok clay. The test results show that the inextensible reinforcements, such as steel grids, move approximately as a rigid body during the pullout test, and the maximum pullout resistance was reached within a relatively small pullout displacement. For extensible reinforcements, such as Tensar geogrids, the degree of resistance mobilization along the reinforcement varies, and the pullout-resistance achieved in the tests was controlled by the stiffness of the reinforcement. For steel grids, the friction resistance from the longitudinal member contributed only to about 10% of the total pullout resistance of the grids. The pullout of the bamboo and Tensar geogrids without transverse members yields 80–90% of the pullout resistance of the corresponding grids with transverse members, attributed to the nodes or ribs on longitudinal members. The bond coefficient as calculated for steel and bamboo grids demonstrated that the steel grids yielded a higher bond coefficient than that of the bamboo grids with the same grid size. However, for a polymer geogrid, the bond coefficient cannot be calculated from a pullout test because of the complicated pullout-resistance-mobilization mechanism along the reinforcement. The large-scale direct-shear-test results showed that, for the soil/grid-reinforcement interfaces, shear resistance can exceed the direct-shear resistance of the soil itself owing to the influence of the apertures on the grids. Finally, for compacted weathered clay, the strength parameters obtained from large-scale direct-shear tests were found to be substantially smaller than the results of triaxial UU tests. This may be because the failure plane in the large-scale direct-shear test was formed progressively, and the peak soil strength along the predetermined shear plane may not have been mobilized simultaneously.

Laboratory pull-out tests using bamboo and polymer geogrids including a case study

This study investigates the interaction between soil and geogrids by using both direct shear and pull-out tests and applied the results to a case study. A polymer geogrid and bamboo grids were used with clayey sand and weathered clay as backfill since these materials are readily available in Thailand. The results indicated that the interaction between soil and reinforcement consists of: (a) the adhesion between soil and reinforcement on the solid surface area of the geogrid; and (b) the bearing capacity of soil in front of all transverse members of the geogrids which behaved as a strip footing embedded in the soil. The proposed design procedure for pull-out resistance agreed fairly well with the laboratory pull-out test results. In addition, it was observed that bamboo grids have higher pull-out resistance per unit area than the polymer geogrids. Moreover, the cohesive fill proved to be quite effective when used with geogrid reinforcement. Finally, the proposed design procedure and test results were applied to a case study on an irrigation canal bank repaired by the Public Works Department of Thailand using cohesive backfill and Tensar SS2 geogrids resulting in much improved slope stability.