| Soft soil has the bad engineering characteristics of large natural water content,large pore ratio,high compression coefficient and low strength.Stirring pile reinforcement method has been widely used in the treatment of soft soil foundation because of the short construction time and low cost.However,as the main curing agent of mixing pile reinforcement,cement often has engineering problems such as poor integrity of pile,insufficient strength of pile and insufficient bearing capacity,and cement has poor curing effect on soft soil with high moisture content and high plastic index.Geopolymer materials are considered as the most likely new green gelling agent to replace cement and have a wide application prospect in the field of soft soil solidification.At present,there is little research on the treatment of silty soft soil along seashore,lakeside and river by geopolymers.Therefore,based on the treatment of Xiangjiang soft soil foundation in Xiangtan City,Hunan Province,this paper intends to use slag-fly ash base polymer instead of cement as the curing agent of soft soil.Through unconfined compressive strength,SEM morphology observation and EDS analysis,the mechanical properties and curing mechanism of geopolymer/cement solidified soil are comparatively studied.In addition,indoor model tests of geopolymer solidified soil composite foundation were carried out to analyze the loading deformation characteristics,pile-soil stress ratio and pile top stress of model piles.The specific research contents are as follows:First,the unconfined compressive strength test was carried out to study the influence of main factors such as water-binder ratio,alkali activator dosage,silicon and aluminum raw material ratio and different ages on the strength of the sample.Based on economy and work integrity,the recommended mixing ratio of slag-fly ash base polymer is as follows: the slag-fly ash ratio is 80:20,the water-binder ratio is 0.4,the alkali activator modulus is 1.2,and the dosage should be 30%.Secondly,the unconfined compressive strength test(UCS)was carried out through the indoor proportion test of geopolymer solidified soil to study the influence of the main factors on the variation of the parameters of geopolymer solidified soil,and to obtain the optimal test scheme of parameter combination.The results show that geopolymer has a better curing effect on soft soil.In practical application,appropriate proportion of slag-fly ash,curing agent content and alkali content should be selected so as to effectively improve the strength of cured soil and have good fluidity.Again,by scanning electron microscope,SEM and X-ray energy spectrum analysis(EDS)tests on polymer solidified soil in the microstructure research,from the micro perspective the slag and fly ash base polymer on the mechanical properties of soft soil,and through the analysis of the chemical composition,mineral composition and microstructure analysis discusses the polymer curing mechanism of soft soil,Combined with previous experience,the hydration mechanism of geopolymer solidified soft soil is deduced,and the microscopic mechanism of geopolymer solidified soft soil of Xiangjiang River is explained.Finally,the study of polymer composite pile treatment of soft soil foundation,according to the optimal ratio of the above experiment,by pouring different working conditions of polymer mixing pile in the laboratory,and ordinary Portland cement mixing pile as the control group,study the consolidation characteristics and deformation mechanism of composite foundation of polymer mixing pile and vertical bearing characteristics of single pile.It provides theoretical basis and data support for soft soil foundation engineering application along river. |
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