Permeability Characteristics of Improved Granite Residual Soils

In response to the mechanical characteristics of the residual soil of granite in Youxi, Fujian, which is prone to softening and disintegration when encountering water, the external additives mixing method was used to improve its properties by adding additives to reduce its permeability coefficient. Adding ratios of lime, fly ash, and residual soil were set to 1∶1∶8, 1∶2∶7, and 1∶3∶6, respectively. Basic physical property index tests, compaction tests, and particle grading analysis tests were conducted on the granite residual soil from Youxi in Fujian. Variable water head permeability tests were conducted on the granite residual soil and improved granite residual soils separately. The test results showed that: (1) The saturated permeability coefficients of the improved granite residual soils by adding lime and fly ash into soil were decreased remarkably compared with that of the remolded residual soil, and its impermeability has been improved. (2) When the ratio of lime, ash, and soil is 1∶2∶7, the decrease in saturated permeability coefficient is the greatest, and the improvement effect in permeability is the best. (3) Whether remolded soil or improved soil, its saturated permeability coefficient increases with the increasing of its pore ratio, and decreases with the increasing of its dry density.