CONTAMINANT TRANSPORT THROUGH FRACTURED POROUS MEDIA: AN EXPERIMENTAL STUDY

Abstract

Groundwater water pollution is very frequent in nature these days. The pollutant travels from a source due to natural movement of groundwater and due to concentration gradient present in space. Transport of pollutants through porous media has received lot of attention in last few decades. Contaminant transport in porous media is very interesting and motivated by concerns over the presence of a wide variety of chemical substances and wastes in subsurface environment. In this dissertation report, an attempt is made to study about the solute transport behaviour through fractured porous media. An experiment has been conducted in the Hydraulics lab. Container consists of fractured porous media which has been created with clay (matrix) and fractured in middle of container for analyzing the behaviour of solute through it. Two set-up has been made one is short and another one as long model. Firstly, the soil was saturated with fresh water then solute was introduced constantly and the samples were collected from out let at time interval. Break through curves are also drawn for observed values. Constant boundary condition and pulse type boundary conditions are used during experiments. Later, observed data of solute has been simulated to determine the transport parameters by using numerical model. It is shown that the solute transport through fractured porous media is a combined process of advective- dispersive transport within fracture and diffusive transport into and out of adjacent matrix blocks. Diffusion from fracture into matrix will likely have some effect on all fracture-transported solutes, unless equilibrium is attained. Hence, it is observed that higher value of diffusion coefficient reduces the magnitude of solute concentration in the fracture. Also, higher value of fracture retardation factor reduces the magnitude of solute concentration in the fracture. It means diffusion coefficient behaves like a fracture retardation factor. Value of diffusion coefficients depend on fracture velocity and resident time for solute transport through fractured porous media