Abstract: Angola Quelo sand possesses the characteristics of softening and collapsibility when immersed with water; it is of significance to study its permeability for engineering. The permeability coefficient of natural and compacted Angola Quelo sand is measured by laboratory variable head penetration test and double-ring water infiltration test. Based on the test data, the ranges of permeability coefficient of natural and compacted Quelo sand is summarized; the relationship between permeability coefficient and void ratio is analyzed. In addition, the surface water infiltration laws of Quelo sand stratum are discussed. The test results show that the brown-red Quelo sand in the upper stratum is high permeability coefficient and poor water retention; so the surface water is easy to infiltrate into underground, whereas the permeability coefficient of the variegated Quelo sand in the lower stratum is low, which has the conditions for forming perched water, and it will be detrimental for engineering. There is an approximately logarithmical function relationship between permeability coefficient and void ratio of the natural brown-red Quelo sand; however, the variegated Quelo sand in lower stratum does not show this regularity. The permeability coefficient of the compacted brown-red Quelo sand is still higher, and anti-seepage effect is poor.

Key words: Quelo sand, brown-red sand, permeability coefficient, water infiltration test, water sensitive soil, phreatic line