Effects of Different Conditions of Water Cooling at High Temperature on the Tensile Strength and Split Surface Roughness Characteristics of Hot Dry Rock

Abstract EN

To investigate the effects of the different conditions of water cooling at high temperature on the tensile strength and split surface roughness characteristics of hot dry rock in the Songliao Basin, the physical characteristics, tensile strength, and split surface roughness of granite under different conditions of water cooling at high temperature were studied.

In addition, the relationship between tensile strength and split surface roughness under different conditions of water cooling at high temperature was established.

The results showed the following: (1) as the rock temperature increased, the number of water injection cycles increased or the water injection temperature decreased, the mechanical properties of the specimen weakened, and the roughness of the split surface increased.

The threshold for the effect of the rock temperature on the split surface roughness of granite was 300°C.

At 400°C, the tensile strength greatly decreased.

At 600°C, the tensile strength, height mean square error (MSE), fluctuation difference, roughness coefficient, and roughness profile index of the specimen were 0.21, 2.51, 2.57, 8.92, and 1.06 times those at 100°C, respectively.

After five heating-cooling cycles, the tensile strength, height MSE, fluctuation difference, roughness coefficient, and roughness profile index of the specimen were 0.57, 1.33, 1.49, 1.29, and 1.01 times those after one cycle, respectively.

(2) The roughness angle calculated using the root mean square of the first derivative of the profile was always greater than that derived using the roughness profile index.

In addition, the higher the temperature, the lower the water temperature, the more high-temperature-water cooling cycles, the greater the difference between the above two calculations.

(3) When the tensile strength varies, the factors affecting the variation in the height MSE and surface roughness were in the following descending order: rock temperature, number of heating-cooling cycles, and water temperature.

In addition, the higher the tensile strength, the lower the roughness coefficient.

This study is expected to provide a reference for the selection of different conditions of water cooling at high temperature for thermal recovery in the Songliao Basin.