Investigation on the Correlation between Electrical Resistivity and Vane Shear Test of Peat Soil

Irfan, Bin Ahmad Afip (2019) Investigation on the Correlation between Electrical Resistivity and Vane Shear Test of Peat Soil. Masters thesis, Universiti Malaysia Sarawak.

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Abstract

This research aims to establish a correlation between electrical resistivity and shear strength of the peat soil using Wenner four-point probes and vane shear methods. The research question is the electrical resistivity reading being affected by these variables, such as, soil density, soil salinity and soil moisture. If the electrical resistivity reading is being subjected into these variables, then, the electrical resistivity reading, and conductivity will be different depend on the variable because the variable will influence the electrical conductivity making the electrical current movement much simpler or vice versa. The specific objectives were two-folds, namely: (a) to determine the physical properties of peat soil, (b) to investigate the relationship between laboratory/field soil resistivity and vane shear test for determination of undrained shear strength. Data were randomly collected over six locations in Meranek, Sarawak for in-situ test and three repetitions for each data set based on three parameters. Physical laboratory soil properties test was then conducted to determine the degree of humification of the soil sample, then, the peat assessment through scanning electron microscope (SEM). The micrograph of peat shows colloidal granular particles with no visible hollow cellular connections. The peat index properties reflected the effect of decomposition and the influence of fabric composition on geotechnical properties of peat was discussed. The test consisted of moisture content, loss on ignition, fiber content, organic content, bulk density, specific gravity and pH. Results indicated that the physical properties obtained were as follows: peat moisture content of 1136.69%, loss of ignition, 91.78%, organic content, 91.27%, fiber content, 5.7%, bulk density, 1.15 Mg/m3, specific gravity, 1.33, pH, 3.57, and Von Post Degree of Humification, H7. The soil resistivity and vane shear strength readings for laboratory testing are correlated with soil salinity, moisture content and density. The R2 values showed a good correlation for soil salinity (R2 =0.8468) and density (R2 =0.9475), respectively. However, a weak correlation of R2 =0.1205 was observed for soil moisture. The R2 value for in-situ correlation between soil resistivity and three parameters (soil salinity, moisture content and density) was R2 =0.8916. It can be concluded that the peat soil shear strengths of the study measured using Wenner four-point probes for in-situ was 4.382 ohm.m and 2.47 ohm.m for laboratory, based from Loke’s studied it is range between 1 to 25 ohm.m is categories as soft material soil and by using the vane shear strength method, the in-situ reading was 23 kPa and 5 kPa for laboratory. It can be implied from this study that the peat soil of the study area can be categorized as loamy soft soil texture and it is suitable for agriculture instead of construction. The relationship established between Wenner four-point probes and vane shear method was to contribute for ground engineering design that would enhanced site suitability investigation work purpose.

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