All issues
Volume 33 (1992 - 199･･･
- Issue 6 Pages 322-
- Issue 5 Pages 245-
- Issue 4 Pages 187-
- Issue 3 Pages 123-
- Issue 2 Pages 61-
- Issue 1 Pages 1-
Volume 33, Issue 5
Displaying 1-5 of 5 articles from this issue
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Yasutaka TERADO1992 Volume 33 Issue 5 Pages 245-254
Published: December 10, 1992
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSThe Lugeon test is a kind of water pressure test of the permeability test introduced by M. Lugeon for measuring permeability of the good foundation rocks of dams. Strictly speaking, it is distinguished from the ordinary permeability test, because it is not always based on Darcy's law. However, Lugeon test is extensively used as the permeability test for the foundation rocks of dams.
In recent years, dams have been constructed not only on the hard bedrocks but also on the weak rocks, cracky rocks with wide open cracks, etc. Therefore, corrections and adjustments have been applied in testing procedures and interpretation methods.
However, in case of bedrocks both with small critical injection pressure and under the condition of deep groundwater level, the proper Lugeon value within critical injection pressure cannot be easily obtained and larger Lugeon value is often gained, for hydrostatic head exceeds the bedrocks' own critical injection pressure and hydrofracturing occurs.
In order to refrain from its phenomenon, injection pressure should be provided near the test stage, not on the ground. Therefore, lately improved Lugeon test method using the borehole multistage constant permeability test method have developed. As a result, the above mentioned problems were almost resolved.
While, in case of huge permeable bedrocks with wide open cracks, Lugeon value resulted from the ordinary Lugeon test is often considerably smaller, because of huge pipelines friction due to turbulent flow. However, according to the writer's experiences, Lugeon value nearly equal to the real permeability under a laminar flow can be obtained by means of the above mentioned method.View full abstractDownload PDF (1553K) -
Tsuyoshi KIMURA, Tetsuro ESAKI1992 Volume 33 Issue 5 Pages 255-262
Published: December 10, 1992
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSShearing characteristics of rock joints strongly depend on the surface roughness. BARTON (1973) proposed an empirical equation to estimate the shear strength of rock joints, introducing the parameter of JRC (joint roughness coefficient). BARTON and CHOUBEY (1977) conducted shear tests of 10 different rock joints and decided the value of JRC for each joint from back calculation using the equation. The values of JRC and the joint profiles are adopted in the suggested methods for the quantitative description of discontinuities in rock masses (ISRM, 1978). However, to decide the value of JRC for a rock joint in question, the joint profile must be visually compared with the 10 typical profiles. In addition, Barton and Choubey's procedure itself includes a few problems to discuss.
In this study, 10 specimens having Barton and Choubey's typical profiles and no roughness in the direction perpendicular to the profiles were made with a numerically controlled cutting technique, and were used in push tests (corresponding to shear tests) and tilt tests. The test results show that some of the profiles do not present the value of JRC correctly, and that the friction angles at the left and right shear directions are different by 20 degrees in one profile. With increase in JRC, the friction angles obtained from the push tests become greater than those from the tilt tests. Shear forces acting along a joint can be estimated from only changes in the dilation associated with shearing, in the case of no damage on the joint surface. In such a case, the parameter of arctan Sm, where Sm is the maximum slope in a profile, is well related to the friction angle of the profile, and can be regarded as a useful one to quantify a profile.View full abstractDownload PDF (1019K) -
Part 2: Joint Characteristic Elements and the Probabilistic Space ModelKokichi KIKUCHI, Yoshitada MITO, Makoto HONDA1992 Volume 33 Issue 5 Pages 263-275
Published: December 10, 1992
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSJoint distribution is regulated by 7 joint characteristic elements ; 1) orientation, 2) persistence, 3) density, 4) aperture, 5) filling, 6) roughness and 7) conductivity. For the purpose of making a stochastic space model of each joint characteristic element is defined as the results of the field investigations, Each joint set has its own distributional character. Therefore, each probabilistic space model must be probability density function conditional upon joint set.View full abstractDownload PDF (2067K) -
Case Study at the Test Shaft in the Tono Mine, Central JapanKoichi YANAGIZAWA, Hisashi IMAI, Nobuhisa OGATA, Hideaki OSAWA, Kunio ...1992 Volume 33 Issue 5 Pages 276-293
Published: December 10, 1992
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSIn order to evaluate the shaft excavation effect on groundwater flow, Power Reactor and Nuclear Fuel Development Corporation has been excavating the test shaft 6 meter in diameter and 150 meter in depth at the Tono Uranium Mine, Central Japan.
In this project, a hydrological evaluation system was set up to understand the shaft excavation effect on groundwater flow. This system consists of groundwater investigation, hydrogeological modeling, predictive simulation and long term observations of the groundwater flow.
The results are as follows;
(1) From the hydrological observation during a year, the recharge rate from the unconsolidated formation situated in subsurface zone into the rock mass was calculated to be 0.57 mm /day.
(2) The hydrogeological model was devided into 12 layers from the results of geological survey, geophysical logging and in-situ hydraulic tests.
(3) From the results of the predictive simulation and observation, the area where pore pressure was changed by the excavation was within 100 meter around the shaft and it was proved that the inflow into the existing shaft and drift was not affected by the excavation.
(4) The predictive simulation and measured data show good agreement.
(5) The availability of the modeling and the simulation, and the efficiency of the hydrological evaluation system have been confirmed.View full abstractDownload PDF (2926K) -
Manabu TAKAHASHI, Ziqiu XUE, Akira OOWADA, Youji ISHIJIMA1992 Volume 33 Issue 5 Pages 294-306
Published: December 10, 1992
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSTo clarify interconnected pore network, blue dyed epoxy impregnated thin sections of various rocks were prepared. Careful microscopic photographic studies of thin sections were able to distinguish pores from grains. Pores are measured clearly by the presence of blue dyed epoxy. This blue dyed epoxy impregnation method was most suitable for rocks with porosity above a few percent, and for fractured rocks with ultimate fracture planes. Specific microcracks with width above 10 micron meter are detected clearly in granitic rocks.
Using an image processing technique, porosities and aspect ratios of pore were estimated from the segmented microsections. Porosities measured from the image, in general, different from that of the physical tests. The porosity of the Shirahama sandstone decreased by about 2% after stressed to 49 MPa. The low aspect ratio pores of the Shirahama sandstone closed completely after stressed to 49 MPa.View full abstractDownload PDF (14018K)
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