The effects of temperature and wet-dry cycling on water-repellent soils

The synthetic modification of soils through the addition of organosilanes to create a water-repellent barrier is a developing area of geoenvironmental engineering research. Organosilane modification of soils can be used for different geotechnical aspects such as landfill covers to prevent infiltration of water into the subsurface waste layers and reduce leachate generation. Research was conducted to evaluate temperature effects on artificially induced water repellency of two different soils and an industrial by-product (coal fly ash). The stability of the water repellency was investigated through exposure of treated samples to wet/dry cycles. To determine the water entry pressure that a modified soil can sustain, soil samples were prepared in a permeameter and connected to a standpipe where water was introduced at a controlled rate. These trials were repeated for different temperatures of the water-soil setup. The stability portion of the tests involved cyclically saturating then drying samples while periodically measuring the effect on water entry pressure. Rainfall runoff depth estimates were combined with the temperature-dependent water entry pressure data for evaluating runoff due to water repellency.