Sulphate Saline Soil Solidified By Modification Sodium Silicate And Its Durability Under Freeze-thaw Cycle

Chemical solidification is an important method to modify and cure soil.Strength and durability is the significant engineering properties for the curing soil.In the long time,most research focuses on the strength property,but the research about the early strength and durability under the condition of dry-wet-freeze-thaw cycles.The degradation mechanism research of curing soil under dry-wet-freeze-thaw cycles indicates that no matter what kind of soil,the solidification mechanism of curing agent is all the same which goes through a series of complicated physical and chemical reactions to form fibroid,needlelike and vitreous hydrated silicate three-dimensional gelatin net structure.It enhance the cohesive force between soil particles.The aging properties of sodium silicate influence the solidification effects,and it mainly causes the weak resistance of three-dimensional gelatin net structure to dry-wet-freeze-thaw cycles.Temperature modified sodium silicate,composite modified water glass and inorganic material-temperature modified sodium silicate are carried out to solidify the saline soil in this thesis.The solidification effects of these three methods are compared through no lateral compressive strength tests.The microstructure of solidified soil is observed under X-ray diffraction test and SEM.The research about resistance to freeze-thaw of solidified saline soil modified by inorganic material-temperature modified sodium silicate is carried out.It is aimed to make a further investigation about efficient chemical curing method on saline soil.It has great practical significance in establishing the theory about sulphate saline soil solidification and in developing the new technique about solidifying sulphate saline soil by modified water glass,lime and coal ash.(1)The research results of no lateral compressive strength tests with saline soil solidified by temperature modified sodium silicate show that: the strength of solidified soil increases with the growth of modified temperature.This is because that the energy from heating makes the aging water glass change into nano particles and enhances the cohesive strength.With the growth of temperature,it accelerates the production of gelatin,increase the amount.The gelatin would fill the pores in saline soil and increase the strength.(2)The research results of no lateral compressive strength tests with saline soil solidifiedby composite modified sodium silicate show that: the strength of solidified soil increase with the growth of PS material volume fraction.The mechanism is that potassium sodium silicate and sodium water glass interact with each other during the procedure and refine particles.Sodium ion has slow velocity to form the gelatin film so that it could cover the gelatin film made by potassium ion which is thin and causes cohesive fracture.Secondary reinforcement of gelatin strength increase the strength of soil.(3)The research results of no lateral compressive strength tests with saline soil solidified by inorganic material-temperature modified sodium silicate show that: the strength of solidified soil decreases with the growth of temperature.This is due to that the sodium silicate Na2O/Si O2 used in the experiments is small,and this results in that the coal ash could not dissolve completely in booster and produce less gelatins.The compressive strength of saline soil solidified by modified water glass under different temperatures decrease with the growth of freeze-thaw cycle times.The descend range become slight after the cycle time is over 10.The resistance to freeze-thaw shows great improvement.The mechanism is that silica gelatin film fills the pores and make it difficult for water movement.