模擬岩石の熱破砕に及ぼす岩石温度の影響

高速水噴流による高温岩体の破砕に関する研究

抄録

Effects of rock temperature on the thermal fracturing of imitative hot dry rock specimens by an impinging water jet having a speed of 70 m/s at nozzle exit (1.4 mm I.D.) have been studied with reference to the establishment of drilling and fracturing methods for natural hot dry rocks. These specimens (75 mm in diameter and 150mm in length) were made of castable fire-resistant material. The temperatures of the specimens were room temperature, 200, 400, 600, 800 and 1000°C. The water was at room temperature.
Experimental results indicated that fracturing patterns of specimens varied characteristically with specimen temperature, θ. On the surface of aspecimen struck by the water jet for 10s, a cylindrical hole-shaped cavity with diametem of 3 to 5 mm at the jet stagnation point was observed in both cases of θ=400°C and θ≥800°C. A large crater-shaped cavity was observed at 600°C. The tendency of curves showing the relation between the depth or the volume of cavities and θ was similar to that of the boiling curve, having the maximum value at about 600°C and the minimum at about 800°C. A model for the flow and the heat transfer with boiling of impinging water jets on a high temperature surface was proposed to explain the experimental results.