Evaluation of the Effect of Nano-Clay and Pressure Change on the Self-Healing Properties of Clay Soils

Some factors such as soil mass settlement, earthquake activities, and hydraulic failure causing tensile forces in the earth's structures and, consequently, cracks creation and development of water leakage from cracks. In this study, to reduce possible damage caused by cracking and its extension to the erosion of internal structures, the effects of nano-clay on the self-healing properties of clayey soils have been investigated. In this study, the effect of nano-clay additive, pressure, and time elapsed on crack restoration in clay was evaluated. To perform experiments, two types of cracks with thicknesses of 0.5 and 1 mm with a depth of 50 mm were created in the samples and the montmorillonite nano-clay was used as an additive. Twelve tests with different percentages of nano-clay, without pressure and at pressures of 50 to 500 kPa in two steps after the cracking (first day) and 24 hours after the creation of crack (second day) were performed for samples with a thickness of 0.5 and 1 mm. The flow rate is measured in all tests and was the basis for judging the impact of each factor. The results showed that when the cracked sample is made with one millimeter, under non-pressure conditions, in about 60 minutes, approximately 500 ml of water passes through the crack. However, when the sample contains 2 and 5% nano-clay, the amount of water passing through the crack within 60 minutes, would be 40 and 5 ml, respectively. This decrease in the volume of passing water shows the positive effect of nano-scale fine grains on cracking closure.