Experimental Study On Dynamic Characteristics Of Fiber-cement Improved Red Clay In Kunming Area

As a kind of special soil,red clay is widely distributed in Yunnan and southwestern in our country.On the one hand,it is regarded as a good foundation due to its good mechanical properties.On the other hand,due to its water sensitivity,regional differentiation and fissures,it has a certain impact on the safety of engineering construction.Based on the research properties at home and abroad,this essay takes the red clay and its improved soil of the Chenggong campus of Yunnan University as the research object.Based on the theory of soil mechanics,the method of triaxial test is used to study the fiber-cement improvement of the red clay in Kunming area.The static and dynamic characteristics of,focus on the analysis of the influence of confining pressure and dry-wet cycles on static strength;the influence of confining pressure,frequency and dry-wet cycles on dynamic deformation properties and dynamic strength properties.The main research results are as follows:（1）When the cement content is less than 15%,the addition of cement to the red clay can greatly improve the non-lateral compressive strength of the red clay;the addition of fibers does not increase the strength of the red clay as much as cement,and when the fiber is too high,the strength of the red clay decreases.In the end,12%cement and 0.5%fiber were selected as the best solutions in chemical and physical improvement methods for follow-up tests.The influence of the dry-wet cycle before and after the improvement on the strength and structure of the soil was analyzed,and it was concluded that the mixing of cement and fiber improved the water-sensitive properties of the red clay.（2）The undrained shear strength of the red clay after the improvement is increased,and the influence of the confining pressure and the dry-wet cycle on the strength of the soil before and after the improvement is analyzed.Using the Mohr Coulomb theory,shear strength indexes(and c)are obtained.（3）The dynamic characteristics of the red clay before and after the improvement are different.The dynamic stress amplitude and the dynamic strain amplitude before the improvement conform to the hyperbolic model,while the dynamic deformation of the modified red clay shows linear elasticity as a whole,which conforms to the linear regression model and Logistic regression.model.After the improvement,the maximum dynamic elastic modulus of the red clay is significantly increased,the damping ratio will be significantly reduced,the dynamic failure mode will be changed,and the dynamic strength will be significantly increased.The influence of the confining pressure,frequency and the number of wet and dry cycles on the dynamic characteristics of the red clay before and after the improvement is analyzed,and the relevant parameters are obtained by fitting.