Comparison of SCS Double Hydrometer Test of Dispersivity of Soil with Pin Hole Test & Chemical Analysis of Pore Water Extract of Soil

摘要

Dispersive soils in general are very erodible and easily deflocculated in water. Use of dispersive clay soils in hydraulic structures and embankment dams or any other water retaining structures can cause serious engineering problems if these soils arenot identified in the construction stage. These soils however can be used in embankment with proper quality control. The conventional index tests such as particle size distribution and Atterberg limits, which are normally, performed on soils are inadequate to identify dispersivity of soils. The available test methods as per ASTMfor dispersive soils are Crumb Test, Pinhole test, SCS double hydrometer Test and chemical analysis of pore water extract. The pinhole test, originally developed by Sherard, which models the erosional performance of soils, is the best test for determining dispersivity of soil. The test is based on visual assessment of the presence of turbidity in the emerging water, and on measurement of the rates of flow. The chemical analysisof soils pore water extract is also seems to be reliable methods for characterizing soil dispersivity. The phenomenon of dispersivity is due to the presence of dissolved sodium content in pore water and therefore its percentage was calculated by estimating total dissolved cations (Na, K. Ca& Mg) present in soils pore water extract. The crumb test is a qualitative test, whereas The SCS dispersion test evolved from the correlation of earth-structure failures and physiochemical soil characteristics161. For identification of dispersivity of soil,out of above mentioned four methods, one particular method may not identify all dispersive clay soil. Therefore they may be performed individually or used together to help verify dispersion1'31. On the basis of above facts, an attempt has been made to correlate the performance SCS double hydrometer test of dispersivity of soil with Pinhole test & Chemical analysis ofpore water extract of soil. A total of 130 data were selectedfrom different river valley projectsfor the analysis. This paper presents comparison of SCS double hydrometer test of dispersivity ofsoil with Pinhole test & Chemical analysis ofpore water extract of soil.