Assessment of Flow Through Clay-sand Liners using Laboratory Models

Three laboratory models were designed to simulate a field section of a clay sand liner. The laboratory models were designed to test 10 cm thick Al Qatif clay sand liners with clay content of 15%, 20% and 25% overlain by agricultural soil and underlain by granular sandy material. The percolation through the clayey layer was measured for repeated watering following variable drying periods. 30 tests were conducted for each clay content over a period of 3 to 4 months in a laboratory controlled environment. Temperature, moisture and electrical conductivity were recorded using 5TE sensors. The hydraulic conductivity and soil water characteristics of the material used in the liners were studied. It was found that the soil suction and drying are related to non-uniform performance of the liner on repeated drying and wetting. The results of a theoretical model using Hydrus 2D for a similar section subjected to different environmental conditions indicated that liners can significantly reduce percolating water. The laboratory model confirmed the findings. The temperature drop below the ambient laboratory value was found 1.0 degrees C for the 15% clay and 0.6 degrees C for 20% and 30% clay liners. The trends of moisture gain and drop were shown.