Journal of the Japan Society of Engineering Geology
Online ISSN : 1884-0973
Print ISSN : 0286-7737
ISSN-L : 0286-7737
Volume 22, Issue 3
Displaying 1-6 of 6 articles from this issue
  • Ryokichi HAMAJIMA, Tadahiko KAWAI
    1981 Volume 22 Issue 3 Pages 261-268
    Published: September 30, 1981
    Released on J-STAGE: June 04, 2010
    JOURNAL FREE ACCESS
    In this paper experimental as well as numerical results are reported for stress distribution in jointed rock media having various types of discontinuities, and these are compared with the corresponding results for a homogeneous elastic media.
    When the angle θ between the joint surface and horizontal axis of cohesionless jointed rock media is varied in the range 0<θ<90°, it is found that there exists a certain traditional angle θ where the stress distribution is also found to changes suddenly. The stress distribution is also found to change suddenly when the tensile strength σt is reduced below a certain critical value. Further this stress distribution becomes equal to that of the homogeneous elastic media when the cohesion C and tensile strengthσt are larger than the corresponding critical values respectively, and the shear modulus G of joint surfaces is set at G=E/(2 (1+ν)) which is obtainable from the elastic theory (ν: Poisson's ratio). The Mohr-Coulomb's linear expression for shearing stress is used for the yield criterion.
    The numerical method of analysis employed in this study is found to be applicable to the analyses of homogenous media as well as discretized jointed rock media, and it is believed that the present analysis can be effectively used for clarifying the mechanical characteristics of rock media of strong anisotropy.
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  • Kunio WATANABE
    1981 Volume 22 Issue 3 Pages 269-275
    Published: September 30, 1981
    Released on J-STAGE: June 04, 2010
    JOURNAL FREE ACCESS
    The continuity of cracks is one of the most important factors to determine many characters of rock mass such as ground water flow, strength and slope failure.
    The crack continuity can be quantitatively estimated by the combined application of two stochastic process models; the branching process model and the percolation process model.
    It goes without saying that detailed field data of crack system, particularly the ratios of the number of crack junctions to that of crack terminal points are indispensable for this kind of analysis.
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  • Takeshi SATO, Akio WATANABE, Akiyo EIKI, Keiji YAMADA
    1981 Volume 22 Issue 3 Pages 276-285
    Published: September 30, 1981
    Released on J-STAGE: June 04, 2010
    JOURNAL FREE ACCESS
    The relationship between rockfall and vibration of the ground has never been fully analyzed before in Japan because of several problems which fall within one of two categories which we have labelled “motivecause” and “primary cause”.
    Problems falling within the “motive cause” category are concerned with characteristics of vibration whilethose problems falling within the “primary cause” category are concerned with the conditions of mountainslopes (e. g. morphometric parameters of slope; shape, size and depths at which blocks have been buried onslopes ; quality of weathered materials and surface soil).
    In spite of these problems, it is quite important to analyze the relationship between rockf all and vibrationof the ground for some kinds of construction works such as railway and tunnel construction because shocksfrom blasting may cause rockfalls.
    In our survey, two seismic tests were carried out-one involving a dynamite blast and the other involvinga shockwave caused by a passing train.The results of these tests can be summarized as follows:
    1. The shock that was produced by the passing train did not cause a severe rockfalls. The maximum deformationof the ground was 7.6-10-5 cmand occurred above 10 seconds. These results are too small tocause a rockf all.
    2. The relationship among the amount of dynamite, the maximum displacement, the maximum accelarationand the transmissive velocity of vibration was studied to find the point at which a severe rockfall waslikely to occur during tunnelling work.In this test, 3 kg of dynamite were exploded 50 meters from the test site. As a result, the maximumdisplacement was 1.4-10-3 cm. This value is also too small to cause a rockfall.
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  • Hidetoshi INOMA
    1981 Volume 22 Issue 3 Pages 286-295
    Published: September 30, 1981
    Released on J-STAGE: June 04, 2010
    JOURNAL FREE ACCESS
    In excavation of the Kan'etsu tunnel, rock burst occurred expectedly. Especially for about 1 year since July 1980, many broken pieces of rock had sprung out frequently. Rock burst should be classified into sometypes, such as springing of rocks, cracks on face without springing of rocks, and only breakdown noises onface or in bed rock. Those types seem to be a series of forms of rock burst. Some examples of occurenceprocess of rock burst are shown in figure-3, -4, -5, -6.
    From our experiences of rock burst, it may be pointed out that those forms of rock burst have somecharacters. They are as follows:
    (1) It occurred even under small overburden.
    (2) It occurred in the formation of quartz-diorite, but not of hornfels.
    (3) It occurred mostly at face, and few at backward and side wall.
    (4) The existence of specific areas where rock burst occurred was recognized in the tunnel.
    (5) At the areas with inflow of ground water, it did not occurred.
    (6) It was related greatly to joint, fractured zone and so forth.
    (7) The sizes of brocken rock pieces were various, but the shapes of them were all generally flat.
    (8) It was closely related with working cycle of tunnel excavation.
    Some investigations including measuring of initial stress in bed rock and its change during tunnel excavation, core discing in the horizontal bored and sampled core, acoustic emission survey, rock properties tests, andtemperature measuring of face and sidewall, were carried out at the rock burst areas.
    As a result, significant informations on the behavior of bed rock related with tunnel excavation and onthe relation between rock burst and working cycle of excavation, were obtained.
    The rock mass at the rock burst areas was elastic and high brittleness. And rock burst seemed to beclosely related to geological weak zone of bed rock.
    For a countermeasure against rock burst, it was adopted as a keystone of tunnel excavation that many rockbolts were installed in working face. The tunneling method that we adopted by utilizing the above mentionedinvestigations of bed rock and analysis of our experiences of rock burst, may be appraised proper.
    It is useful that the system of acoustic emission survey is composed completely in order to control tunnelexcavation work at the rock burst areas.
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  • [in Japanese]
    1981 Volume 22 Issue 3 Pages 296-302_2
    Published: September 30, 1981
    Released on J-STAGE: June 04, 2010
    JOURNAL FREE ACCESS
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  • 1981 Volume 22 Issue 3 Pages 303-305
    Published: September 30, 1981
    Released on J-STAGE: June 04, 2010
    JOURNAL FREE ACCESS
    Download PDF (372K)
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