Sumitomo Osaka Cement Co., Ltd. (SOC) Kokura Mine and Mitsubishi Materials Corporation (MMC) Higashitani mine adjoiningly operate limestone mine at Hiraodai area in Kita-Kyusyu city, Fukuoka prefecture. MMC Higashitani mine need to replace underground facilities when bench down from current mining level in order to secure future minable deposit. SOC Kokura mine has undeveloped mining area between Higashitani mine, but cannot utilize their plenty minable deposit since there is no way to carry limestone to their cement plant because Kokura mine is located inland. In order to solve above issues, both mines started joint development project by focusing on the following five points. 1 Utilize the limestone deposit in SOC's undeveloped mining area and boundary area of both mines. 2 To plan production and shipping quantity for the purpose that all joint develop area can end mining at the same time. 3 Confirm content of installed facilities and investment cost between both companies and clarify way of cost allocation. 4 Ensure the safety operation and seek minimum cost. 5 Joint work to acquire necessary license/Approval and to solve social issue with local community. This joint project is not only aim to secure the limestone deposit, but also enable us to built long term supply system, obtain new customers and improve operating ratio by joint use of their facilities. And this approach would be the one of the ideal model of limestone mine.

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Polycrystalline diamond compact (PDC) tips, which originated with the development of PDC cutters in 1973, have recently been used to fabricate percussion drill bits. In the present study, rotary-percussion drilling tests were carried out to evaluate the performance of two PDC percussion bits, both having a diameter of 65 mm, but containing different types of PDC tips. The drilling medium was hard abrasive granite. For comparison, a WC-Co percussion bit was also tested. The WC-Co percussion bit reached the end of its life at a drilling length of 20.6 m due to large gage loss. In addition, its rate of penetration (ROP) decreased quickly with increasing drilling length due to large height loss at the gage tips. On the other hand, for both PDC percussion bits, a drilling length of 46.8 m was achieved without gage loss and with very small height loss. In addition, the decrease in the ROP with increasing drilling length was much less for the two PDC percussion bits. Thus, the PDC percussion bits exhibit much higher performance than the WC-Co percussion bit. Also emphasized is that we found the fact that the torque on bit detects the height loss on gage tips of all bits. Finally, the drilling costs using the different bits were estimated based on the results of the drilling tests and several reasonable assumptions. It was found that for a drilling length of 80 m, the total drilling costs were almost the same for the PDC percussion bits and the WC-Co percussion bit, even though the bit cost of PDC percussion bits were considerably more expensive.

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Variation of rock strength has an important role in designing the various rock structures. Though strength in uniaxial stress state such as uniaxial compressive strength has been well investigated up to now, the strength in complicated stress state such as triaxial compressive or shear strength has been studied only to very limited extent because of its difficulty in experimental works. For example, variation of shear strength should be studied under various normal stresses and then many specimens are necessary. In this study, direct shear tests of red shale were conducted under the normal stress from 1 to 6 MPa. A special care was taken to make as many specimens as possible from the limited sample rock, and total number of 397 specimens were tested. It was found that the variation of Δτ, which is the difference between the shear strengths measured in testing and calculated with the regression line, did not depend on normal stress. The obtained failure criterion and variation of strength for the red shale were discussed comparing the envelope of rock stress which was reported previously and the results of other rocks in various testing conditions.

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A tropospheric delay is known to give non-negligible error to measurements in precise displacement monitoring using Global Positioning System (GPS), when difference in height between GPS antenna points is large, or more than a few tens of meters. One effective way to reduce such error, in the case of short baselines (less than a few kilo-meters), is to process GPS signal taking mathematical tropospheric model such as the Modified Hopfield model, and meteorological data near the measurement site. However, under the condition of large height difference between antenna points, some amount of error still remains after the correction, especially in the seasons that weather changes a lot. Therefore, this paper proposes a new method to correct tropospheric delay error more easily and effectively than the correction method using mathematical tropospheric model and meteorological data. In our method, tropospheric delay error is directly measured at a fixed point, and the measured error is proportionally allocated to the other measurement points depending on the height differences between the reference point and the measurement points. This proposed correction method was applied to a field measurement that had continued for more than five years at an open-pit limestone quarry, which had nine GPS antennas with a maximum height difference of 209 meters. The results showed that the proposed correction method successfully removed the tropospheric delay errors better than the conventional method. Furthermore, according to a measurement performance test that was carried out in the same site, 5-millimeter displacement given to an antenna in height direction could be detected within 1-millimeter accuracy.

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Acid Mine Drainage (AMD), high acid water containing heavy metals discharged from mines, not only from the operating ones but also from the already abandoned ones, has been recognized as major cause of mine pollution. In Japan, the government spends billions of yen every year to prevent pollution caused by AMD in about 80 abandoned mines. It is widely believed that the treatment will continue for decades or an even century,but it is difficult to predict how long it will be and how much it will cost.Therefore, a predictive model is quite helpful. In our previous work, a two-steps predictive model for solution composition and neutralization chemical requirements of AMD in future was constructed based on the regression analysis and geochemical modeling. The model requires the past historical water quality data from AMD monitoring, such as metal concentration and pH in the solution, instead of the sample rocks as other conventional prediction methods. In this paper, two more case studies were carried out for Japanese abandoned mines. In each case study, future solution composition, neutralizer dosage and sludge generation were estimated. Then, the time when the water quality satisfies Japanese effluent standard was estimated. The results of this study demonstrate the effectiveness of our model for the prediction of AMD quality and chemical requirements of neutralization treatment after mine closing. These results were analyzed in the context of TMR (Total Material Requirement) and the environmental burden of this neutralization process is relatively small comparing to the burden of operations and the long time span of neutralization seems more serious concern. Comparing the result of this paper with that of our previous works, it is revealed that we have to carry out more case studies in order to obtain the general idea of future AMD treatment.

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