Study On Durability Of Sulfate Saline Soil Under Freezing-thawing And Drying-wetting Cycles

In northwest, the temperature is big difference between day and night. The northwest environment characteristics is more centralized rainfall and strong evaporation, soil area hit under the freezing-thawing, drying-wetting alternate function and so on, It not only increased the soil salinization, but also the engineering properties of saline soil and its development is greatly restricted. Therefore, strengthening the study on action the durability of of saline soil under freezing-thawing and drying-wetting cycles, is to make the saline soil science for engineering application in the area of theoretical guidance.This article selects the sulfate saline soil of Hexi Corridor for study.Making saline soil remake sample and experrimenting respectively for different specimens under the unconfined compressive strength test, microscopic test and disintegration test and so on. Combined with the feature of microscopic and macroscopic phenomena to study the variation of saline soil under the different. action. We get the following conclusions:(1) In the freeze-thaw cycles, for the first time after freeze-thaw effect unconfined compressive strength with cyclic number constantly attenuation, quality constantly attenuation; In the dry-wet cycles, unconfined compressive strength along with continuous attenuation, cycle times and has periodic, diminishing quality too. Sample in the dry wet- the joint action of freezing and thawing damage, faster than the action of single but whether method to strain and radial strain, deformation of the sample is not the simple accumulation of single action results.(2) The freezing and thawing, and the roles of dry wet will have great influence on the microstructure of soil sample, and the reaction to the macroscopic properties. Pores in soil after a contrast, the increase in the number, but the total area is reduced, in the body of the soil elements are still exist in amorphous sulfate, connection to the stability of soil skeleton play a role. Repeated freezing and thawing, big pore area occupies a large proportion, make the structure of softening, irreversible changes, the intensity attenuation. In the wet function, the variation regularity of pore play an important role in the development process of microcracks. After a dry wet effect, sharply reduce the pore area, grain drying shrinkage effect obviously, soil particle contact more closely, the sample has higher intensity. Again and again of dry wet function, microcracks in soils of continuous development, the pore number increasing, the growth of macropore contribution is very big.(3) The disintegration of the sample is the comprehensive performance of water immersion effect, wedging effect of soil sample surface and cement dissolution erosion effect. Each other is feedback and contact. Different amount of disintegrating under the action of saline soil and disintegration rate change rule, frozen, freeze-thaw and dry after after disintegration curve close to the sample. The disintegration time of sample of drying-wetting process increases obviously, disintegrating slowly. Drying-wetting effect is greater than the influence of the freezing-thawing on the process of disintegration. We find the soil disintegration law is different and the disintegration curve is not a typical “ S ” through the test combined effects of different process in different order. The initial state of disintegration of soil samples has a great effect on results.