Experimental Investigation on Strength and Bearing Capacity Improvement of a High Plasticity Clayey Subgrade Soil Using Lime

Limited connectivity and poor infrastructure of roads acts as a roadblocks hampering the socio-economic development of one region. In order to overall development of these regions an effort should be given to cultivate well established road network. But due to scarcity of good quality soil PWD engineers are often forced to build roads over the weak soil which directly affects the strength and durability of the road. It is therefore essential to improve the engineering properties of such problematic soil with suitable stabilization technique as and when encountered. Lime stabilization is one such well known chemical stabilization technique extensively used to improve the poor subgrade condition and it is recommended by several codes in INDIA. This paper attempts to study the effect of lime on strength and bearing capacity improvement of soft clayey soil. A series of UCS and CBR tests are conducted with different percentages of lime (i.e. 3, 5, 7 and 9%) and at different curing period to assess the potential of lime in strength improvement. Test results indicate that strength, stiffness and bearing capacity of the soil is considerably improved after lime amendment. Both unconfined compressive strength (UCS) and California bearing ration (CBR) improved up to 7% of lime beyond that it decreases. The improvement of UCS and CBR is found approx three and five fold as compared to original soil. Underlying mechanisms of this improvement is further scrutinized by microstructural analysis such as X-ray diffraction (XRD), Field Emission scanning electron microscope (FESEM) with Energy dispersive X-Ray Analysis (EDAX). Apparent formation of some new peaks in XRD analysis and change of textural and structural morphology of clayey soils obtained from FESEM confirms the formation of cementitious compounds in the lime stabilized soil.