Study on unconfined compressive strength of two ash saline soil under freeze-thaw cycle
Saline soil is widely distributed in China,and the engineering performance of saline soil in frozen state deteriorates gradually with the development of freeze-thaw cycle,which affects the safe operation and durability of engineering in saline soil area.The influence of lime and rice husk ash(RHA)content on the unconfined compressive strength(UCS)of saline soil under different freeze-thaw cycles was studied through unconfined compressive test in Daqing City,Heilongjiang Province.The results show that the strain corresponding to the peak axial stress of the stress-strain curve increases during freeze-thaw cycle,which is a strain softening type.The elastic modulus becomes smaller,and the elastic stage of 0 and 1 freeze-thaw cycles is prominent,and the compaction stage after 3 freeze-thaw cycles is obvious.With the increase of the number of freeze-thaw cycles,the UCS of both natural and lime-RHA-stabilized soilds initially rises slighthy and then decreased significantly.The strength was the highest during the first freeze-thaw cycle,and the first to fifth freeze-thaw cycle was in the rapid deterioration stage,and the fifth freeze-thaw cycle reached the stable stage.It is suggested that the UCS of the fifth freeze-thaw cycle should be taken as the stable strength value.The greatest UCS improvement is achieved with 6％lime and 8％RHA,with strength enhancement factors of 4.32,3.50,4.83,3.63,3.39,and 3.31 after 0,1,3,5,7 and 9 freeze-thaw cycles,respectively.The lime-RHA combination is more effective than lime alone,and RHA alone outperforms lime alone.
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