THE STUDY OF INFILTRATION ON UNSATURATED SOIL FOR NON-ADIABATIC NON-ISOTHERMAL CONDITION

• Main Author: Adhi Fajar, Reza
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/43946
• Institution: Institut Teknologi Bandung

Water infiltration from the ground surface is generally considered to be the groundwater recharge, while some which transform into the vapor phase and back to the groundsurface during evaporation. Therefore, there is an uncertainty in the determination of the volume of water infiltration that become the groundwater recharge. In this case, the mechanism of water vapor movement inside soil-bare is influenced by energy equilibrium as well as the characteristics of porous media. Meanwhile, previous infiltration models have not specifically included the principle of energy equilibrium, thus is needed to improve the formulation of water infiltration involving thermodynamics principles. In this study, groundwater flow equations were reformulated through the concept of positive infiltration, negative infiltration and simultaneous infiltration, respectively with a downward orientation, upward, and a combination of both opposite directions. Conceptual and mathematical models were constructed, with the resulting infiltration formulation involving thermal components in the form of the Modified Richard Equation (MRE). The verification was done gradually with a physical model approach in the form of a soil column test apparatus or an Infiltration Column and numerical simulation of different element methods through the Crank Nicolson scheme which wass supported by a series of laboratory tests. Hypotheses in this study have been answered by the identifying point of optimum water content infiltration as the turning point of an infiltration gradient in the equation of Richard-Fajar, especially for the case of simultaneous infiltration with the continuous flux assumption. The location of the point where the optimum water content is affected by the size of the porous media grains designed to equal the granules of sand, silt and clay, in accordance with the AASHTO soil classification system using silica sand. In this case, the rate of positive infiltration is always greater than the negative infiltration rate, because the evaporation process in the porous media layer occurs in the position of dry water content and without the influence of gravity.