Experimental Study On The Effect Of Coal-metakaolin On Strength And Deformation Of Cement Soil

Cement soil is a common relatively cheap material.It has many advantages,such as convenience construction,small environmental pollution and wide application.So it is used in various fields of geotechnical engineering.When it is used to strengthen the weak foundation,due to the particularity of soil and the uncertainty of engineering environment,cement soil must have better performance to meet the needs of the actual project.In this paper,under the background of the practical application of cement-soil mixing piles,the admixtures of the coal-metakaolin,which is secondary to coal gangue,and cement are used as compound curing agent to reinforce soil.Through the indoor unconfined compressive strength test,the strength and deformation performance of cement soil under different working conditions are studied to evaluate the performance of improved cement soil.The main research contents are as follows:(1)The strength and deformation characteristics of improved cement soil soaked in clean water were studied.The strength variation of improved cement soil under different ages and MK contents was investigated.The strength regression model based on the above two factors was proposed.A new method of dealing with stress-strain curve was proposed,and the measured stress-strain curve was modified by this method.The modified stress-strain curves were compared to analyze the effect of age and MK content on its morphology.The relationship between the ultimate strain,deformation modulus and compressive strength of the improved soil was analyzed qualitatively.(2)The strength and deformation characteristics of improved cement soil soaked in sodium sulfate solution were studied.The compressive strength of improved cement soil was analyzed by comparing the compressive strength at different ages,MK contents and sodium sulfate solution concentrations.Two kinds of intensity regression models were established,i.e.,prediction model of compressive strength based on age and MK content,and intensity prediction model based on MK content and sodium sulfate concentration under 28 d age.Through the above two models,the relationships of three factors that is age,MK content,sodium sulfate concentration and compressive strength were established.The influences of the above three factors on the stress-strain curve were analyzed.Through the qualitative study of the relationship between the limit strain compressive strength and deformation modulus,the concentration of corrosive solution,the strength and deformation characteristics were combined organically.(3)The constitutive model of improved cement soil under different working conditions were studied.Based on the standards and codes,the constitutive model of concrete was used to simulate the stress-strain curve of cement soil.The model was used to analyze the parameters of constitutive model of improved cement soil under two different curing environments.