Abstract: In the aim of exploring the effect of nitrogen fertilizer pollution on the physical and mechanical properties of red clay, the change regularity of typical red clay from Yanshan mountain, Guilin was analyzed. The red clay specimens were immersed in ammonia (NH₃·H₂O) solution with ammonia concentration (0, 4.5%,9.5%, 13.5%, 18%) and curing time (1 d, 7 d, 14 d) as controlling factors. Results show that the mass, moisture content, specific gravity, liquid limit and plastic limit all increased with the increase of ammonia concentration and curing time; but compression modulus decreased, while compressibility of soil is enhanced. The alkali-soil interaction is the fundamental cause of the weakening in physical and mechanical performance of alkali-contaminated red clay in Guilin area. Such interaction results in the dissolution of the binder between red clay particles and the formation of flocculants, hence changing the original stable state of the structure.

Key words: red clay, ammonia contaminated, physical and mechanical properties, curing time, experimental study, Yanshan area of Guilin