Effect of Fly Ash on The Compressibility Behavior of Peat: An Experimental Study

Abstract

Peats are considered as geotechnically problematic soil, due to their high compressibility and low shear strength. To improve peat chemical and mechanical method of stabilization is widely used. This paper focuses on an experimental study to chemically stabilize peat by deep mixing method (DMM) using ASTM class F fly ash as the stabilizer. Peat: fly ash ratio of 90: 10 was used in the stabilization mix. Testing such as index properties tests (organic content, specific gravity and Atterberg limit), direct shear test and Rowe cell test were conducted for raw peat and fly ash stabilized peat. For the Rowe cell test, 30 mm diameter central fly ash stabilized DMM column was placed in the raw peat sample, and the consolidation test was performed for raw peat sample, and the consolidation test was performed for raw peat and the peat with central fly ash stabilized column. Based on the experimental findings, peat used can be classified as sapric amorphous peat with a Von Post scale classification of H8 class. In addition, cohesion (c) increases with the addition of 10% of fly ash while friction angle (Ø) reduces with fly ash addition. Compressibility parameters (Cv, Cα and Cc) decrease with the addition of 10% fly ash to peat and the reason for the reduction is fly ash absorbs water from peat and undergo reactions producing stiffer matrix. Percentage reduction in Cv and Cα are 12.7% - 33.4% and 7.1% - 25.93% depending on the normal stress, while the percentage reduction in Cc is 10.5%.