Permeability and Cracking of Compacted Clay Liner Improved by Nano-SiO2 and Sisal Fiber

The landfill liner is the last line of defense to protect the soil from damage, but it is difficult to satisfy both impermeability and crack resistance requirements with conventionally compacted clay. This paper proposes a new composite material to enhance the anti-seepage and anti-cracking properties of clay as a solution to this problem. In this Study, the effects of two single amendment materials, Nano-SiO2 (6 dopings) and sisal fiber (SF) (4 dopings), and a composite amendment material (Nano-SiO2+SF), on the permeability and cracking resistance of the improved clay were investigated by infiltration tests and dry-wet cycle tests, respectively. The nuclear magnetic resonance test (NMR) test reveals the microscopic pore changes of soil and explore the reinforcement mechanism. The findings of penetration experiments demonstrate that Nano-SiO2 and SF, both single and composite components, can increase the modified clay’s impermeability. The optimum content of Nano-SiO2 is 3%, and its permeability coefficient is 5.09 × 10−8 cm·s−1, which is two orders of magnitude lesser than that of virgin soil. The results of three dry and wet cycle tests showed that the overall trend of fracture length and cracking factor (CIF) increased with the increase of the number of de-wetting. After the third de-wetting of the modified clay, 0.75% Nano-SiO2 + 0.3% SF is the optimal dose, which reduces the fissure length by 19.94 times and CIF by 27.25 times compared with the three de-wetting of the plain clay. As a whole, the data demonstrates that the composite Nano-SiO2 and SF are able to make up for the shortcomings of each component. It can simultaneously improve the anti-seepage and anti-cracking properties of the enhanced clay. The test results provide a certain benchmark for the impermeability and anti-cracking of landfill liners.