Test Research On The Expansion Characteristics Of Coarse Sulphate Saline Soil

Sulphate saline soil has salt expansion,collapsibility,corrosion and other engineering hazards,expansion is the main hazard. Treatment of saline soil foundation is mainly to eliminate the salt expansion,existing study on the expansion characteristics of coarse saline soil is more about expansion deformation, the method of sulfate salty soil treatment is mainly for it’s expansion,but there is a few research on the expansion force.In order to understand salt heaving characteristics of saline soil comprehensively,the author described the common salty soil treatment methods and problems to be solved, and designed a series of laboratory simulation tests on the condition of single cooling after considering the constraint conditions, moisture conditions,the factors of salt type, salt content, temperature change and load suppression in practical engineering.Through the simulation test for84sets of samples,the author obtained the following conclusions which have theoretical significance and engineering practical value.a.In the cooling process, sensitive temperature which influence the volume swelling strain and swelling load of coarse saline soil sample is0℃-2.5℃, almost no change after-2.5℃cooling process; temperature section of maximum expansion force is-5℃-10℃,mostly in nearly-7℃.b.For the same salt content and moisture content, different soil samples,there are two different void ratio that make the maximum volumetric strain and freezing-salt expansion force of the samples have maximum and minimum(0.55,0.58in this test).c.The expansion force growth rate changes with the stage of cooling process. During the room temperature to about10℃cooling process, the expansion force growth rate decreases sharply,in the cooling process of0℃2.5℃,the growth rate decreases after transient increase,then remain stable.d.The influence of moisture content and salt content on the expansion force is coupling; increasing of the moisture content makes an increased salinity which maximum expansion force required, but may make the biggest frozen-salt expansion force relatively reduced.e.Under constrained conditions,the volume expansion strain and expansion stress showed good linear rule, the expansion force growth rate is related to salinity and the void ratio. This is the important basis of saline soil foundation treatment, at the same time, the author suggests that the design load value should not be less than50kPa when we design anchors or counterforce device of coarse saline soil in practical engineering.