We reported the rock drillability of rotary-percussion drilling using a roller cone bit in a previous paper. In the present paper, investigation of the rock drillability was extended to percussion drilling using two types of percussion bits. Rocks used for this investigation were granite and two types of andesite having uniaxial compressive strengths of 131 to 214 MPa. Drilling tests were conducted at inlet oil pressures of the percussion drill of 9.5 to 13.5 MPa and at rotary speeds of 25 to 175 rpm. The main results obtained from the tests are as follows:
1. The maximum penetration rate and the minimum specific energy were obtained at the inlet oil pressure of 13.5 MPa, independent of rock and bit types.
2. With respect to the penetration rate and specific energy, the appropriate rotary speed was judged to be about 75 rpm in the high-speed bit and about 100 to 150 rpm in the button bit. In addition, the rotary energy was larger than the percussion energy at the appropriate rotary speed.
3. When rocks were drilled effectively, the effect of the percussion energy and that of the rotary energy on the penetration rate were almost the same.
4. The minimum value of specific energy in percussion drilling using the high-speed bit was correlated very roughly with the uniaxial compressive strength of the rock being drilled.
5. The minimum specific energy of percussion drilling was larger than that of rotary drilling, independent of rock and bit types.

抄録全体を表示

高温, 拘束圧下における火成岩の熱膨張特性を明らかにするため, 5種類の岩石を用いて, 温度30℃～284℃, 拘束圧0～49.0MPaの条件下で測定を行い, 火成岩の熱膨張特性は, 温度にも圧力にも依存すること, および花崗岩質岩石と安山岩とでは, 熱膨張特性が異なることを示した. また, 火成岩の熱膨張特性を支配する四つの要因を提案するとともに, 今回の測定結果は, これらの要因によりよく説明できることを示した.

抄録全体を表示

A new virial equation of state for ammonia was obtained. The second and the third coefficients of the equation were determined, using the experimental results of Beattie and Meyers, and the values that were calculated with the molecular theory by Rowlinson were adopted as the second virial coefficient for low temperature. A formula for specific heat of vapour ammonia under the ideal state was obtained, using the values that were calculated by Harrison and Kobe. A formula of vapour pressure of ammonia was obtained for a temperature range from -70°C to the critical temperature, using the experimental results of Cragoe and the others. The other charactaristic equations were made through thermodynamical calculation. The author calculated the charactaristic values of ammonia from the equation of state and the others, and made i-log₁₀P diagram for a temperature range from 0.2kg/cm² to 80kg/cm² and also for a temperature range from -60°C to 300°C.

抄録全体を表示

A practical method of measuring REYNOLD's stress uv, by a hot wire anemometer with single hot wire fixed on a rotatable support and operated by constant constant temperature method, is presented with experimental results. Emphasis is placed on simplicity in measuring processes and accuracy in quantitative results. For the purpose of ascertainning quantitative accuracy of this method, an experiment was made in a fully developed turbulent flow in a 8.3 cm diameter pipe at speeds of 10, 20 and 30m/s. Values of Reynolds stress measured by the hot-wire were compared with the values calculated from the preassure drop along pipe axis and the mean velocity distribution across the diameter. Preliminary experiments, to arrange a formula of effective velocity, -effective heat loss on hot wire inclined to flow direction, were made in a wind tunnel flow at speeds of 312m/s with two different diameter hot wires;-thinner one was used for turbulence measurements.

抄録全体を表示

In the present study, a drilling test using a 66-mm-diamter high-speed (HS) percussion bit was first carried out to investigate the rock drillability of Sori granite, which has a uniaxial compressive strength of about 220 MPa. Durability tests were then performed with Sori granite using two HS bits in order to investigate the effect of the bit weight on the amount of bit wear. Based on the results of the drillability tests, bit weights of about 6 kN and 13 kN were selected. The main results obtained from the durability tests are as follows:
a. The penetration rate of both bits decreased linearly with increasing drilled length. On the other hand, the specific energy increased almost linearly with drilled length.
b. Both bits almost reached the bit-life at the drilled length of about 30 m. A detailed analysis revealed that, for both bits, the torque increased linearly with drilled length, with the final torque at 30 m being about 0.11 and 0.13 kN-m higher than the initial.
c. For both bits, the height-loss of gauge tips was almost identical and increased linearly with drilled length.
e. For both bits, a one-to-one correspondence was found between the increase in torque and the height-loss of gauge tips. This revealed that the torque is a quantitative indicator of bit wear, regardless of the bit weight.
Finally, to investigate the effect of changing the rock strength, a drilling test was conducted using a new HS bit with Shinkomatsu andesite, which has a uniaxial compressive strength of 192 MPa. The one-to-one correspondence mentioned above was observed as well.

抄録全体を表示

Three point bending tests were conducted to investigate the effect of the chemical and wet environments on the fracture toughness of Inada granite, Kimachi sandstone, and Shin-Komatsu andesite. The new testing method was also suggested here so that the chemical solution or water constantly can exist at the crack tip during the tests. The fracture toughness was evaluated by both ISRM suggested method and AE (Acoustic Emission) technique. In AE technique AE hypocenter distribution was determined to pinpoint the crack front and process zone, then stress intensity factor was calculated using the crack length evaluated by AE hypocenters distribution. Fracture toughness of the granite, in which significant decrease has not been reported before even in wet condition, dropped 25 % in wet condition when compared to the one in dry condition, and also 37 % down in Kimachi sandstone. In Shin-Komatsu andesite, fracture toughness in wet or chemical condition dropped about 10 % from dry condition. It was found that the form of crack, estimated by AE hypocenters, have two patterns in Inada Granite. But in other rocks, there are only one pattern infracture loading. The AE behaviors in wet condition implies that the fracture mechanism could be changed from brittle manner to possibly ductile one.

抄録全体を表示