| The direct application of loess as the filling of railway subgrade will result in certain engineering problems such as insufficient strength and high permeability.Alkali-excited base polymers are widely tried because of their good mechanical properties and environmental protection.In order to solve the loess engineering issues,alkali water glass activated slag base polymer was used to improve loess properties.In order to study the reinforcement effect,anti-seepage effect,reinforcement mechanism and anti-seepage mechanism of railway subgrade loess by different improvement methods.Taking the loess of Xi’an,mixing the required proportion of GGBS with raw loess,adding the corresponding proportion of water glass’s solution to carry out the test.Through direct shear test,unconfined compressive strength test and water penetration test,combined with scanning electron microscopy test,particle size analysis test,XRD test and mercury injection test to reveal the improvement mechanism,this study has the engineering extension,economy and environmental friendliness in the improvement of railway subgrade loess.The main research results are listed as follows:（1）When GGBS is mixed alone,its content is an important factor affecting the skeleton mechanical properties of loess.With the increase of powder content（65%→90%）,the shear strength firstly increases and then decreases.When the powder ratio is 80%,that is,when the optimal mass ratio of loess to GGBS is 1:0.75,the shear strength index c value of 7 d increases to 91.9 k Pa（31.7%higher than that of normal loess）.Theφvalue is increased to 32.1°.（2）The modulus and alkali content of sodium silicate were the main factors affecting the mechanical and impermeability of loess when sodium silicate excited GGBS solidified loess structures.With the decrease of the modulus of water glass and the increase of alkali content,the compressive strength of GGBS solidified loess induced by water glass increased,and the water content and permeability coefficient decreased.The optimal proportion of water glass was 1.5 modulus and 1.5%alkali content,and the compressive strength reached 14.9 MPa at28 days,which was 33.7 times higher than that of raw loess.The moisture content at 7 days was 10.8%,which decreased by 42.2%.The permeability coefficient at 7 days is 7.08×10-6 cm/s,which is 12 times smaller than that of plain loess.（3）Considering the engineering application and promotion,according to the orthogonal test results under different sodium silicate modulus and alkali content,the optimal economic combination range of sodium silicate excited GGBS to improve loess is concluded:sodium silicate modulus is 1.5～2.4,alkali content is 1～1.5%.In addition,the influence of sodium silicate modulus on mechanical strength and permeability coefficient of improved loess is greater than that of alkali content under the condition of economy consistency.（4）Sodium silicate activated GGBS to generate calcium silicate（aluminate）gel,which improved the degree of cementation and coarse particle content of loess skeleton particles.The mechanical properties of loess were improved.The generated gel fills and blocks the super-large pores,making the overall distribution of pore diameter channels narrow and pore connectivity worse,improving the friction strength and bond strength of loess,and reducing the permeability. |
