Dispersive Soil Essay

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The soils that are highly susceptible to erosion and containing high percentage of sodium ions are called “Dispersive soil.” Dispersivity is the property of soil by virtue of which soil separates into their component particles when wet. Soil dispersivity is due to the presence of exchangeable sodium present in the structure. Dispersive soils are structurally unstable soils. In appearance, dispersive clays are like normal clays that are stable and somewhat resistance to erosion, but in reality they are highly erosive and subjected to damage and failure. These soils are erodible in nature and have tendency to segregate in presence of water and erode under small seepage velocity leading to problems of stability failure of earth and earth retaining…show more content…
The failures associated with this type of soil are piping and internal erosion due to dispersion of soil. These soils cannot be identified by visual classification, Atterberg’s limits or particle size analysis. Dispersive soils are identified by pinhole test, crumb test and double hydrometer test. So, these soils are identified and stabilized. These soils are characterized by an unstable structure, easily flocculated in water, and very erodible. These soils usually contain high percentage of exchangeable sodium ions which is susceptible to replacement by calcium and aluminium ions. Soil with higher composition of coarse grained particles has higher dispersibility that lead to lower resistance to the internal erosion. Dispersive soils are stabilized with lime and fly ash. The dispersivity of soil is reduced with the addition of lime, pozzolanic material and cement. It is observed that with the increase in lignosulfonate the coefficient of erosion decreases and significantly increases the critical shear stress of both clayey and silty soils. Palm oil fuel ash is pozzolanic material. With the increase in POFA content the maximum dry density decreases and water content increases. POFA is used as a stabilizer in peat soil stabilization with the addition of OPC increased the unconfined confined compressive strength

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