Study On The Rheological Behavior Of The Slurry Backfill Material

In the field of engineering, stability and durability is the basic engineering standard of a backfill material. Because of its small slurry viscosity, good fluidity, high strength, expansion actively, slurry backfill material is popular in mine filling and underground caverns gradually. However, there is lack of the study on its rheological properties, this paper focuses on the rheological properties of slurry backfill material.This paper mainly used the uniaxial compression creep theory and methods, Cyclic loading and unloading test auxiliary. The rheological properties of backfill body and mechanical parameters were studied. Replacing the previous methods of axial deformation as the reference standard, Deformation modulus and Poisson’s ratio were considered as the research object. The time effect of the two parameters and the strain rate effect has carried on the detailed study. On the basis of these, the relationship between stress-strain explored. At the same time by using the method of numerical analysis and simulation of the backfill body to simulate the constitutive equation. deducing the strength of backfill body of time-varying. Studying the timeliness and durability of the backfill body was certain guiding significance. The main research content of this paper is as follows:(1) Slurry backfill material’s tension-compression ratio was about 0.16, the brittle characteristics was obvious. When loading, per level backfill body had instantaneous deformation under load, then for creep deformation. Creep under the action of a single load level, backfill body grew with the increase of the load time, entered the stable creep stage tend to a constant growth rate but not 0. Steady creep rate under different load levels increased with the increase of load. Backfill body lateral, axial deformation both had stress threshold, the lateral threshold value was about 60%~80% of axial. The lateral deformation was more sensitive than the axial. It was a way to measure creep Poisson’s ratio of the backfill body to predict deformation degree. When filling Poisson’s ratio was more than 0.4, the lateral deformation of the filling into the acceleration phase; when the Poisson’s ratio was 0.6, the whole of filling maybe entered the stage of accelerated creep.(2) Based on the uniaxial compression creep test of concrete, the characteristics creep curve was analyzed,and come to the conclusion that burgers model was applicable to describe the creep characteristics of backfill body. Using the creep curve to back analysis the parameter of burgers model with the Origin8.0 Least-square method,a one-dimensional constitutive equation of backfill body were established. The results of time-varying strength analysis showed that compressive strength of backfill body decreased by 17.83% after 10 years, if it were 100 years, the body decreased by 49.33%. Using FLAC3 D to simulate the creep, stress and strain changed over time and the analysis results are basically identical. When the external load sustained acted on the structure of backfill body, even if the load were small, growth over time, the continued deterioration still had occured within the material backfill body.(3) The moisture content of backfill body was one of the most obvious factors of the body creep. With the improvement of backfill body’s moisture content, body’s mechanical parameters have been promoted, the viscous coefficient of backfill increased as well, especially in the stage of high stress level. creep rate along with the increase of moisture content gradually reduced. Size effect for the homogeneous and structural unit small material was very small, almost negligible. It would had great guiding significance for the test research conclusion to apply to production field. Loading rate on the influence of the backfill body was mainly performed in two aspects: on the one hand backfill body deformation rate was certain. when loading rate was less than or equal to the deformation rate of backfill body, the deformation of the backfill body was sufficient, as measured by the rate of deformation rate was the real. While loading rate were greater than the backfill body deformation rate, deformation of backfill body would lag the loading rate, at that time would show some parameters bigger "illusion", high loading rate of backfill body had a certain impact damage; On the other hand, as the increase of loading rate backfill body instantaneous deformation modulus of the specimens increased gradually, and it was regularity with stress level. Low stress and moderate stress level, the change of the instantaneous deformation modulus was obvious linear law, at a high stress level, the variations in the instantaneous deformation modulus was nonlinear law.