Study In The Salt Expansion And Characteristic Of Sulfate Saline Soil In Yinnan Irrigation Area Of The Yellow River In Ningxia

In this paper, the foundation soil of the fourth pumping station of Ningxia Yellow irrigation project was taken as the main research target. Firstly,we deduced the relations of water content, salinity and volumetric strain of saline soil,according to the salt expansion and deformation effects;In this paper, we make researchs on rules of salt expansion and characteristics of saline soil; through on-site sampling and took single temperature expansion tests indoors,It is founde that in situations when water content be unchanged, The test show that:(1) The salt expansion rate increases with the decrease of tmperature and the temperature limits of voilent change of salt expansion is from 15℃to—5℃;(2) The salt expansion rate increases with the increase of initial dry densityi;(3) The salt expansion rate increases with the increase of Na2So4 content;Through buried moisture, temperature sensors, displacement models in different depths,and then carried on dynamic observations of the moisture within the foundation and vertical displacement of temperature, founded that:(1) The temperature distributions of each soil layer changes in period, concludes the rules and the reasons of the temperature distribution changes within the foundation of saline soil. (2) The main causes leading to moisture content gradient is the temperature gradient, the free water in the soil migrated toward the cold side under the effect of temperature gradient, the migration amounts increased with the increases of temperature gradient;(3) Periods from early December to late March the following year when the temperature of foundation soil is below 5℃, is the best time for the developments of salt expansion deformation; The temperature of foundation soil is betweent 5℃to- 5℃,and the amounts of salt expansion increased rapidly.Finally, in allusion to the persecute situation of expansion and distortion of foundation of the fourth pump station of Ningxia supporting Yanghuang irrigation project, according to the actual situations of the project and the excellent engineering experiences of my dear mentor, I have suggested some practical methods to deal with saline soil foundation.