Abstract: Rain infiltration through the soil is the critical factor in the frequent landslides on the coast of China. By considering the geological disaster points of Dehua County, Quanzhou City, Fujian Province as the main research object, the permeability characteristics of slope wash and granite residual soil are concerned in these typical geological disaster points. The one-dimensional soil column infiltration test was carried out using the soil infiltration device developed by simulating rain intensities of 15, 30 and 60 mm/h, respectively, with the rainfall conditions of duration (180 min) and amount (90 mm). The response law of moisture content, wetting front and infiltration rate of each soil column with time under different working conditions was investigated. The main results are presented in detail. The soil wetness spreads deeper and faster as the permeability coefficient of soil and the rainfall intensity become greater. The soil moisture content responds to rainfall from shallow to deep part during the process of rainfall infiltration. Meanwhile, the influence of different rain intensities on water content is mainly reflected in the first response time and saturation time. The high intensity of rain leads to short response time and a quick saturation speed. A function is proposed for different rainfall intensities, which can characterise the wetting front infiltration laws of the Maping landslide and the Bengtuling landslide in Dehua County. The results are of great significance for the early warning of landslide hazards.

Key words: rainfall, slope wash and residual soil, wetting front, response time, landslide