Study On The Performance And Application Of Geopolymer In Soft Soil Foundation Treatment

In this paper,the author proposes a method of strengthening soft soil foundation by a kind of geopolymer which is a new green and environment-friendly alkali activated cementitious material as solidifying agent through mixing pile method.The performance of the soft soil reinforced by geopolymer is mainly studied.First,the initial’ mix proportion of geopolymer treating soft soil was obtained by experimental design,and the unconfined compressive strength test and direct shear test were carried out in the laboratory.The orthogonal test was carried out with three indexes,the content of the geopolymer,the water content of the soft soil and the stirring time.And the optimum mixture ratio of ground polymer reinforced soft soil foundation was determined by means of range and variance analysis.The main and secondary factors affecting the strength of reinforced soil are the content of geopolymer and the water content of soft soil.The unconfined compressive strength and shear strength of ground polymer soil at 90d age can reach 3.75～4.73 MPa and 0.753～1.523 MPa,respectively.It is found that the strength law of reinforced soft soil increases with the increase of age and content of geopolymer,and decreases with the increase of water content,and that there is a positive correlation between unconfined compressive strength and shear strength of geopolymer soil.When the unconfined compressive strength fcu=3.75～4.73 MPa,its cohesion c=0.753～1.523 MPa,its internal friction angle between 34 degrees-47 degrees fluctuations,and its compressive strength is about 3.03-5.12 times of shear strength.At the same time,by measuring permeability and proportion limit of geopolymer soil,permeability coefficient of polymer soil can reach 10-9cm/s or even 10-8cm/s,smaller than the undisturbed soil permeability coefficient 10-7cm/s,and it is found that polymer soil proportion limit increases with the increase of unconfined compressive strength values,a positive correlation between σp and fcu is shown,and the regression results for σp=0.8 fcu.Then,the reinforced soil samples are analyzed by microscopic test.By scanning electron microscope(SEM)and CT(SEM)test,it is found that the reaction of geopolymer can produce cementation and filling and reduce the soil porosity.What’s more,it is found that polymer soil absorption peak appeared in the absorption peak of 877 cm-1 and 1141cm-1 of pure polymer and undisturbed soil were not seen by infrared spectrum experiment,indicating that the bond is caused by the formation of the reactant and changes the internal structure.Finally,through the design and stability analysis of the geopolymer soil mixing pile,and combined with the on-site engineering examples,the further checking and calculation are carried out.The core and static load test results of field test show that after reaching 28d age,the strength of the mixing pile meets the design requirements,and the design of soft foundation treatment is carried out,and the construction technology and construction parameters are determined.The research results of this paper can provide a new way and new method for soft foundation treatment,and it also has the guiding significance in construction.