International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056 Volume: 04 Issue: 04 | Apr -2017 www.irjet.net p-ISSN: 2395-0072 © 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 1081 Influence of Different Mulches and Combination of Biochar and Sawdust Ash on Soil Permeability Nirmal John Joy 1 , Elza Mathew Varghese 2 1 Assistant Professor, Department of Civil Engineering, SAINTGITS College of Engineering, Kottayam, Kerala, India 2 PG Student Department of Civil Engineering, SAINTGITS College of Engineering, Kottayam, Kerala, India ---------------------------------------------------------------------***---------------------------------------------------------------------- Abstract - Permeability is defined as the ability of a porous media to transmit fluids. The stability of a structure is also depends on the amount of moisture under the soil. This paper is focused on the impact of addition of different mulches and combination of biochar and sawdust ash on soil permeability. Soil sample was collected from Vadavathor dumping yard site, Kottayam, Kerala. Site soil was examined initially and different combinations of both the adsorbents and mulches were added into the soil. The coefficient of permeability of the soil samples were determined using falling head method. The results showed that k value of the sample reduced for different combinations due to the action of cations, which hindered the flow of water. Mulches like straw, rubber, cardboard, woodchips were placed into the soil at different thickness(2cm, 3cm, 4cm -height) and adsorbents were added for a maximum of 4cm height(1cm-1cm,1cm-2cm,1cm-3cm,2cm-1cm,2cm- 2cm,3cm-1cm). Both the mulches and combination of adsorbents showed a reduction in permeability. Key Words: Permeability, Mulches, Adsorbents, Combination, Biochar, Sawdust ash. 1. INTRODUCTION There exist various measures for altering the permeability of the soil. Soil permeability is basically a measure of the ease with which water can flow through a soil. Permeability depends on porosity – the higher the porosity the higher the permeability. It is one of the most important geotechnical parameters that determine the behaviour of the soil. The three main parameters that determine the soil characteristics are shear strength, settlement and permeability. If the coefficient of permeability (k value) of the soil is higher, it shows that the passage of water through the sample is easier, there offers less resistance to the flow of fluids. There are many materials available in the market for altering the permeability. Reducing the ease with which the water can flow into the soil, that is reduction of permeability using locally available low cost mulches is an effective way. Mulching is the process or practice of covering the soil/ground to make more favorable condition for improving soil characteristics. Mulch technical term means covering of soil, while natural mulches such as leaf, stray, dead leaves and compost have been used for centuries. Mulching effects are physical (infiltration, improved water-holding capacity, soil structure and if decomposing organic material is correctly incorporated into the soil it also has a positive effect on aeration), chemical (soil pH, release of small amounts of nutrients, decomposing) and biological (temperature regulation for increasing microorganism activity)[1]. Rubber powder was usually taken from recycled rubber from automotive and truck scrap tires. Crumb rubbers were obtained from tyre manufactures. Cardboard mulches saves water loss through evaporation. It prevents soil compaction and maintains balanced soil temperatures. Straw mulch is organic. It is convenient to use and it also maintains soil moisture. Straw is collected from nearby field. Wood chips prevent weed growth and reduce light passage. Mulches chosen for this study include straw, rubber, cardboard, woodchips. The materials were collected from the local market nearby. Adsorbents selected for this work were biochar and sawdust ash. Sawdust is the term given to the product formed after cutting the wood log. It occurs in various sizes and shapes. It occurs in abundant quantity. Such a large amount of sawdust waste is mostly fed to landfill disposals [2]. Therefore effective utilization of sawdust ash is of great importance. It can be used for reducing the permeability of the soil. Waste sawdust ash is sourced from a sawmill. Biochar is a kind of charcoal made from the pyrolysis of a wide range of biomass feedstock, including crop, wood and yard wastes, and manures etc. It is also interesting because it has been demonstrated to improve soil quality and crop growth [3].It can be also used for lowering the permeability of the soil. Biochar required for the study is obtained from wood ash. Logs of wood are sourced from a local timber mill. 2. MATERIALS For the experimental work the site soil was collected from Vadavathor dumping yard site, Kottayam, kerala. Initial soil tests were conducted on the collected sample. Soil was dig out and packed in plastic bags, foreign matters like pieces of wood, cut glasses, plastic covers etc were removed from the soil carefully. Field density was also determined.