| With the rapid development of science and technology,the depth of coal mining gradually deepened,deep shaft roadway high temperature and high humidity problems are increasingly prominent,the roadway lining stability of the roadway rock lining adversely affected.Therefore,this paper takes a new type of thermal insulating shotcrete as the object of study,and uses indoor temperature and wet cycle test to simulate the underground high water temperature and dry and wet cycle environment to investigate the parameter deterioration and creep characteristics of thermal insulating shotcrete after the effect of temperature and wet cycle.The main findings are as follows.(1)After the manufacture of the thermal insulating shotcrete specimens,four bath temperatures(room temperature,40℃,60℃ and 80℃)were set,and the specimens were cycled dry and wet 3,7,14 and 28 times at each temperature to study the deterioration of the thermal insulating shotcrete parameters.The quality,ultrasonic velocity and thermal conductivity of the specimens are tested during the cycle,and the compressive strength test,damage characterization and microscopic analysis are performed after the cycle.The results show that the mass loss rate of the specimens after each cycle at the same bath temperature is negative,which means that the specimens have more mass than before the cycle;The ultrasonic speed increases and then decreases as the number of cycles of the specimen increases at each water bath temperature;The thermal conductivity of the specimen after 28 cycles in 40℃ water bath is 0.2866W/(m·K),which is only 3.2%higher than the thermal conductivity without cycle;The compressive strength of the specimen after cycling in the bath temperature shows the change rule of increasing first and decreasing later as the number of cycles increases;When the water bath temperature is at room temperature,the specimen breaks the cracks with the increase of cycles from tensile cracks gradually to shear cracks,shear damage features gradually obvious,80℃ cycle almost all the specimens for axial splitting destruction;The intensity of diffraction peaks of C2S and C3S becomes weaker gradually with the increase of the number of cycles,while the intensity of their hydration products C-S-H and AFt gradually increases with the increase of the number of dry and wet cycles.(2)The uniaxial compression creep test is carried out at a loading rate of 1KN/min,and the axial creep strain increases with the increase of the number of dry and wet cycles at each stress level;At each stress level,the axial steady-state creep rate shows a nonlinear increase with the increase in the number of dry and wet cycles,and the axial steady-state creep strain rate is larger at higher stress levels;The instantaneous deformation modulus decreases nonlinearly with the increase of wet and dry cycles,and the instantaneous deformation modulus E0 and the number of wet and dry cycles n is in accordance with the E0=6.31-0.861n n relation,R2=0.95.(3)The uniaxial compression creep test was carried out at a loading rate of 3KN/min,the axial strain of the specimen at each graded stress level increased with the increase of temperature in the water bath;When the water bath temperature is 40℃,the axial creep strain in the specimen shows a tendency of increasing and then decreasing with the increase of the number of cycles;At each stress level,the axial steady-state creep rate shows a nonlinear increase with increasing bath temperature;The instantaneous modulus of deformation decreases nonlinearly with the increase in the number of wet and dry cycles,and the instantaneous modulus of deformation E0 and the number of wet and dry cycles n exist E0=4.83-0.651n(n-2.53),R2=0.88;After 0,3,7 cycles of wet and dry cycles in a room temperature water bath,the specimens have a larger creep deformation at higher loading rates,and after 14,28 cycles,the creep deformation at lower loading rates is larger,and a group of specimens with 0 cycles of wet and dry cycles at room temperature is selected as the object of study,and the axial steady-state creep rate is larger when the loading rate is 3KN/min.Figure[58]table[23]reference[80]... |
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