Study On Fatigue Characteristics Of Red Mud-Cement Stabilized Soil Under Freeze-Thaw Action

In recent years,with the rapid improvement of China’s economic development,alumina output has also increased year by year.The resulting industrial waste,namely red mud,will waste resources on the one hand,and pollute the surrounding environment on the other.Thus,how to effectively absorb red mud has become a hot topic.Mixing red mud into cement composite soil can not only improve the mechanical properties of cement composite soil,but also create economic benefits,save land resources,and relieve the pressure of red mud on the environment.Taking into account that the red mud-cement composite soil in the northern region can be damaged by freeze-thaw cycles and fatigue damage caused by vehicles,which will significantly reduce the basic mechanical properties and durability of the material.Therefore,studying the influence of red mud content on the mechanical properties,fatigue performance and micro-structure mechanism of red mud-cement composite soil is a necessary link to verify the feasibility of applying red mud-cement composite soil to engineering practice.Meanwhile,it also has important Theoretical significance and engineering application value.In this thesis,laboratory experiments were conducted to explore the influence of the amount of red mud and the number of freeze-thaw cycles on the mechanical properties and fatigue properties of cement composite soil.The main tasks are:(1)The unconfined compression test and split tensile test of the red mud-cement composite soil under the conditions of different red mud content,cement content,and freeze-thaw times were carried out,and the cement content and red mud content were obtained.The influence of freezing and thawing times on the unconfined compressive strength and splitting tensile strength of red mud-cement composite soil was given;(2)By the orthogonal test,the fatigue loading test was carried out in advance before the unconfined compressive strength test of the red mud-cement composite soil.Under the loading mode of fixed frequency and fatigue times,the freezing and thawing times and the red mud were obtained.The influence degree and law of the three factors of admixture and amplitude load on the unconfined compressive strength and split tensile strength of red mud-cement composite soil was given,and the regression equation and surface graph of the three factors on the compressive strength was established;Under the mode of increasing fatigue loading,the influence degree and law of red mud content,freeze-thaw times and loading frequency on fatigue life of red mud-cement composite soil were explored,and the regression equation and curve diagram of the influence of red mud content,freeze-thaw times and loading frequency on fatigue life of red mud-cement composite soil were established according to the experiment data.(3)In the augmented fatigue loading mode,the influence degree and rules of three factors,namely the red mud content,freeze-thaw times,loading frequency on the fatigue life of the red mud-cement composite soil and the law of influence.The regression equation and surface diagram of the effect of red mud content,freeze-thaw times,loading frequency on the fatigue life of red mud-cement composite soil were established based on the data obtained from the test.(4)In the constant amplitude fatigue loading mode,the influence degree and rules of three factors,red mud content,freeze-thaw times,and amplitude loading on the fatigue life of the red mud-cement composite soil were explored,and the regression equation and surface diagram of red mud content,freeze-thaw cycles and amplitude load on the fatigue life of red mud-cement composite soil were established.(5)Through the analysis of the results of scanning electron microscopy(SEM)and energy spectrum analysis,the influence of the amount of red mud and cement on the development of hydration products in the red mud-cement composite soil specimen was obtained,and the effect of freeze-thaw times on the strength of the specimen was explained from a microscopic point of view.