Experimental Study On Mechanical Properties Of Fiber Reinforced Cemented Tailings Material Under Multiple Factors

The large-scale resource utilization of mine solid waste（tailings）is extremely important for the development of environmentally friendly mines,and the use of tailings as cementitious materials for engineering is an effective means of large-scale elimination of tailings.Ordinary cemented tailings material（CTM）is generally used for mine filling.The fiber mixed into the CTM can improve the strength and toughness of the CTM,so that its application in engineering becomes more extensive.Therefore,supported by the National Natural Science Foundation of China（No.51764013）,this paper investigates the mechanical properties of fiber reinforced cement body（FRCTM）under uniaxial compression under various factors（cementitious sand ratio（c/t）,mass fraction,and fiber type）,with a view to providing suitable material proportioning options for the application of FRCTM in engineering.In this paper,based on laboratory experiments,gray theory,and numerical simulation,the mechanical properties of FRCTM were studied,and the variation rules of strength and toughness,macroscopic failure patterns,and microscopic reinforcement mechanisms of FRCTM under factors such as c/t,mass fraction,and fiber type were obtained,as well as the correlation between the mechanical properties of FRCTM and multiple factors.And the fracture process of FRCTM under uniaxial compression was simulated and reproduced.The research results can provide scientific reference for the engineering application of FRCTM.The main research results are as follows:（1）Uniaxial compression tests were carried out on cementing specimens with different c/t（1:6,1:8,1:10）,mass fractions（65%,68%,72%）and fiber types（fibreless,glass fiber,polyacrylonitrile（PAN）fiber）using MTS testing machine.The change trend of the strength of the CTM that increases with the increase of the c/t or mass fraction is basically not affected by the addition of fibers.Only when the c/t is 1:10,the strength of the glass fiber reinforced CTM increases first and then decreases as the mass fraction increases;When the mass fraction is 68%,the fiber has the most obvious effect on improving the strength of the CTM.When the mass fraction is 72%,there is a negative increase in the strength of the CTM After the fiber is added.This indicates that when adding fibers to improve the strength of the CTM in engineering,it is necessary to strictly control the mass fraction;considering comprehensively the toughening effect of PAN fiber on the CTM is the best;When the CTM is destroyed,the integrity of the CTM mixed with fibers is good,and the cracks are small and not obvious.The destruction occurs in the post peak stage.（2）MLA650F scanning electron microscope was used to observe the microscopic morphology of the CTM specimens that had completed the uniaxial compression test.The c/t is proportional to the degree of hydration reaction,that is,the more hydrated calcium silicate（C-S-H gel）is produced;The higher the mass fraction,the less Ca（OH）₂,and the more ettringite（AFt）and C-S-H gel;The fibers retard the development of cracks in the CTM through frictional and adhesive bonding.（3）Based on the gray correlation analysis method,the correlation degree between the mechanical properties of different fiber reinforced CTM and factors such as the mortar ratio and mass fraction was studied.The correlation degree between the c/t and the strength and toughness of the cement is greater than 0.5,And the correlation degree of mass fraction is small,indicating that the c/t is a key factor affecting the mechanical properties of the CTM;Compared to non reinforced CTM,the contribution rate of the mortar ratio to the strength and toughness of glass fiber reinforced CTM is small,while the contribution rate to the strength and toughness of PAN fiber reinforced CTM is large,indicating that the effect of improving the mechanical properties of PAN fiber reinforced CTM by changing the mortar ratio is the best.（4）Based on FLAC 3D numerical software,the fracture process of FRCTM under uniaxial compression was studied and reproduced.The stress-strain curves obtained from simulation tests and indoor tests have a similar trend before and After the peak stress,and the error of the peak stress is within 5%,which proves the reliability of the model;The displacement and delamination phenomenon of FRCTM compared to non reinforced CTM is relatively obvious,there is no significant stress concentration phenomenon during the entire loading process,and the plastic zone distribution is relatively sparse and loose,which proves that FRCTM has better compression resistance.