Study On The Salty And Frost Swelling Properties Of Compactive Sulfate Salty Soil

The fine earth region of no relief of Shuimohe in north Tiansha distributes the salty soil extensively, in the soil, sulfate salty soil damaging greatest, is very danger to the water cannel, highway etc. Seriously, the engineering problem often sees no fresh .Therefore, take the soil of that region-the bigger damage and low liquid limit powder silt to be used as the research object. The research purpose of the thesis is that studying the rolling salty soil-the salty and frost property, for the engineering practice to provide the guild. This article studied the light compactive experiment of silt in that region ,the experiment of not saturated and saturated sulfate salty soil-salty and frost swelling ratio,salty and frost force; analyzing its salty and frost property, and combined the entity microscope and scanned electronic microscope means to further study its salty and frost property.Finally, article apply the experiment result to in the engineering. For the single salty and frost swelling experiment, in the condition of no loads, the experiment result can be the salty and frost swelling guild of upper part having no loads,Moreover, for the single salty and frost swelling force experiment, the adoptive condition of no deformation , experiment result can be the reference of sulfate salty soil of upper part having loads. First, this article carries on the research to the compactive experiment of low liquid silt in Xinjiang ,and gets next new understanding:with the increase of Na2SO4 content, ①In contrary to the chlorine salty soil, the plastic limit,the liquid limit of the sulfate salty soil are increasing.②the maximum dry density of light compactive experiment increases.③optimum water content of light compactive experiment increases. Second, the thesis aims at the salty and frost swelling experiment of sulfate salty soil, finds the result: ①For the single temperature influence, the salty and frost swelling experiment, Na2SO4 content smaller than 1 percents ,the main salty and frost swelling is under zero degree. When the Na2SO4 content is bigger than 1%,the main salty and frost swelling is above zero degree. The begin swelling temperature is relative to the Na2SO4 content but not the dry density. ②To make the saturated sulfate salty soil sample, there is new discover: it must not change the Na2SO4 content. According to the experience, experiment first make sample water content approach -ing the saturated content, second steam bled in the vacuum pump, then pumping the saturated sulfate salty liquid to soaking sample, so the absorbed water is little , Na2SO4 content changes also little.③For the salty and frost swelling expe-riment changing with the Na2SO4 content, saturated sulfate salty soil swells great, under the single water content factor, its salty and swelling ratio is near two times of un-saturated sample.④For the salty and frost swelling experiment of single dry density factor, 2 percents Na2SO4 content, the curve between the salty and frost swelling ratio with the dry density is ""shape. However, when the Na2SO4 content under 2 percents, the curve between the salty and frost swelling ratio with the dry density is horizon line shape. Third, the article studies the salty and frost swelling force of sulfate soil, the result shows: ①The greatest salty and frost force don't take place in the lowest temperature, sometimes salty and frost force decreasing with cooling.②The same to the salty and frost swelling ratio experiment, the begin swelling temperature increasing with the Na2SO4 content .For the sulfate salty soil of high Na2SO4 content is easy to take place swelling under normal temperature.③When the Na2SO4 content above 1 percents, salty and frost swelling force is rather large above zero decree, 90 percents when zero decree.④When temperature is -5℃,the salty and frost force is greatest , and stability below -5℃. ⑤For the experiment of salty and frost swelling force changing with Na2SO4 content , along with the increment of the sulfate salty content, experimenting the curve is even to present the basically slow line growth, but be unlike the salty and frost ratio experiment stage that rate of expansion experiment increases the slowness, behind it, increase quicker.⑥For the same sulfate salty content, biggest salty and frost swelling force increases along with dry density. ⑦Similarly to the salty and frost swelling experiment, the salty and frost swelling force of saturated sulfate salty soil is very large. Forth, it studied the experiment of the micro entity microscope and scan microscope electricity, the results showed: The observed results are accordance with the macro salty and frost swelling ratio experiment. Furthermore, also generalized new discovers like this: The separation of sodium sulfate in the grain contact boundary is distributed homogeneous, in the pore space is first distributed homogeneous in the outside pore, accumulated some degree, then distributed in the internal pore. The salty distribution is homogeneous in the close circulmstance. To the un-saturated sulfate salty soil, in spits of bigger salty content and dry density, on the condition of no loads, the hole among grain contact boundary,pore space can't be wholly fill-up by the salty and ice crystal, but there is part hole. Because solum has swelled freely when the pore is filled some extent. Finally, the article applied the research results to the engineering, conducted some suggestions: ①In the engineering it should do our best to reduce the Na2SO4 and water content of solum, speciously the saturated water content. ②For the no dry sulfate salty soil, the permission design Na2SO4 content should not above 1 percents in the code. ③To the fill...