CBR Improvement of Clayey Soil with Geo-grid
The quality and life of pavement is greatly affected by the type of sub-grade, sub base and base course materials. The most important of these are the type and quality of sub-grade soil. But in India most of the flexible pavements are need to be constructed over weak and problematic sub-grade. The California bearing ratio (CBR) of these sub-grade have very low, it needs to more thickness of pavement. Decrease in the availability of suitable sub base and base materials for pavement construction have leads to a search for economic method of converting locally available problematic soil to suitable construction materials. The present research have to study the effect of geo-grid reinforcement on maximum dry density (MDD), Optimum Moisture Content (OMC), California Bearing Ratio (CBR) and E-Value of sub-grade soil. The clayey type of soil and one type of geo--grid were selected for this study. From the study it is clear that there is considerable improvement in California Bearing Ratio (CBR) of sub-grade due to geo-grid reinforcement. In case of without reinforcement (Geo-grid) the soaked CBR value was 2.9% and when geo-grid was placed at 0.2H from the top of the specimen the CBR increases to 9.4%.
Study on Improvement of Sub Grade Soil using Soil-Reinforcement Technique
A pavement constructed over a weak subgrade soil needs greater crust thickness due to low sub grade strength and such pavements which are laid directly on the weak clayey soils also fail early due to a non-uniform settlement resulting from the volume changes of the weak sub grade soil in the presence of moisture. Using geogrid a geo-synthetic material as reinforcement in the soil is also another technique for improving the sub grade strength. The choice of stabilizer depends on the type of sub grade soil, type of soil improvement required and accessibility of stabilizer. Improvement in the strength characteristics of the sub grade soil was evaluated using the CBR test. In the present study, use of geogrid at the different position of the CBR mould did not show good improvements in the strength of the black cotton soil. This may be due to lack of friction between the geogrid material placed and the black cotton soil. In case of the Sandy gravel soil, the CBR strength increased in the range of 6.8% to 10.2%, which is comparatively a better improvement compared to the strength gain in the Black cotton soil. This is because of good friction between the geogrid material and the sandy gravel soil.
Analytical and Experimental Investigation of Soil Reinforcing.
Abstract : Significant improvements in the capacity and service life of reinforced earth structures require an improved understanding of the fundamental behavior of these systems. Both experimental and analytical investigations were carried out to develop models for the interaction of geotextile-type reinforcement and granular soils. Reinforcement configurations and systems investigated were thought to be applicable to alternate launch and recovery surfaces (ALRS). Model ALRS systems using geotextiles and geogrids as reinforcement were tested in the laboratory in a variety of configurations. These were loaded to failure, quasi-statically, by both plane strain and axisymmetric rigid plates. Load-deformation characteristics as well as the shape of the deflected basin are reported. Significant increases in bearing capacity and modulus of subgrade reaction as a function of depth and number of layers of reinforcement were observed. However, there was a decrease in improvement as the depth to the first layer increased. Edge fixity conditions were found to be relatively unimportant, and the benefit of multiple-reinforcement layers was greater if the depth and spacing were small compared to the diameter of the loaded area. Surprisingly, little difference was observed in the response of the geogrids and geotextiles, probably because sand was used in the experiments. Geometric scaling of bearing capacity, based on the diameters of the loaded areas, was not possible.