All issues
Volume 21 (1980)
- Issue 4 Pages 181-
- Issue 3 Pages 119-
- Issue 2 Pages 51-
- Issue 1 Pages 1-
Volume 21, Issue 4
Displaying 1-5 of 5 articles from this issue
- |<
- <
- 1
- >
- >|
-
Masamitsu NEGISHI1980 Volume 21 Issue 4 Pages 181-194
Published: December 30, 1980
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSAs it is widely recognized that there is a large difference in strength between rock mass with fissures and intact test-pieces of rock, the author aimed to establish more useful equations that bind both strengths.
For this purpose, test-pieces with numerous micro cracks made by freezing and thawing cycles were prepared, and the relation between their uniaxial compressive strength and P-wave velocity was investigated.
The result showed that this relation is considerably similar to that of rock mass with fissures and indicates that this is a very useful method in laboratory.
Test-pieces of welded tuff were used for this experiment because of its uniform texture and appropriate hardness. On the basis of the results of laboratory experiments on the test-pieces of intact and cracy rock, an approximate value of shear strength of rock mass can be calculated by the following equation:
τm0=τp0 (Vpm/Vp0) n
where, in case of soft rock (uniaxial conpressive
strength qu0=10-100 kg/cm2), n=1.3-1.7
medium hard rock (qu0=100-500), n=1.6-2.8
hard rock class I (qu0=500-1, 000), n=2.7-4.0
hard rock class II (qu0≥1, 000), n=4.0-5.5
τm0: shear strength of rock mass (cohesion)
τp0: shear strength of intact test-pieces of rock (cohesion)
Vpm: P-wave velocity of rock mass
Vp0: P-wave velocity of intact test-pieces of rock.
Furthermore, the relation between shear strength of intact test-pieces of rock and that of rock mass obtained by blok shear tests at 10 localities of Hokkaido, can be approximately expressed by the following equation:
τm-b0=τp0 (Vpm/Vp0) N
where, in case of soft rock, N=3.0-3.5
medium hard rock, N=3.5-5.5
hard rock class I, N=5.5-8.0
hard rock class II, N≥8.0
τm-b0: shear strength of rock mass obtained by
in-situ block shear tests (cohesion, kg/cm2)
In planning of general construction the latter value (τm-b0) has been commonly used. However, the differerence of the two values (τm0 and τm-b0) must be recognized, and their application should be made according to the purpose of safety of dam, tunnel and slople stability of large cutting in rock mass, etc.View full abstractDownload PDF (2850K) -
Ryuichi OKAMOTO, Saburo MIURA, Yasuo NAKAMURA1980 Volume 21 Issue 4 Pages 195-206
Published: December 30, 1980
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSDams constructed on recent volcanic rocks have many difficult problems on foundations and abutments such as strength, permeability and so on. Authors have been conducting case studies on 25 dams constructed on Neogene and Quaternary volcanic rocks in Kyushu District to find out the most relevant seepage control methods for such dams. Obtained results are as follows.
From a seepage control viewpoint, geological features of studied dams are classified into following six large groups: 1) Lava, 2) Alternation of lava and pyroclastic rocks, 3) Tuff breccia, 4) Densely welded tuff, 5) Partially welded tuff-“Shirasu”, 6) Old river deposits etc. On the other hand, permeability of rock mass estimating from ground water level at abutments is classified into following three large groups: A) Ground water level at abutments is relatively high, B) Ground water level at abutments is relatively low but higher than river bed elevation, C) Ground water level at abutments is lower than river bed elevation.
Considering these six geological features and three permeability characteristics, the most relevant seepage control methods proposed by authors are shown in Table 7. As shown in Table 7 curtain grouting can be applied for a wide variety of geological conditions. Detailed profile of curtain grouting is shown in Table 8. But both Table 7 and 8 are tentative standards at early planning stage, so practical seepage control methods should be selected taking full account of precise geological conditions of each dams and conducting various in situ tests such as grouting test, Lugeon test, pumping test, etc.
As recent volcanic rocks in Kyushu are often distributed laterally, problems on seepage control arise from not only dam sites but also overall storage areas. So it is important to investigate geological conditions of overall storage areas and to point out problems. Then the most relevant seepage control methods should be selected for various geological conditions such as consolidation grouting, limb grouting, branket, concrete cutoff, etc.View full abstractDownload PDF (2644K) -
On the Conditions of Occurrence and Prediction of MudflowHideo KASAI1980 Volume 21 Issue 4 Pages 207-215
Published: December 30, 1980
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSIn the previous report, many papers on the mudflow were collected and summarized in order to examine the present state of understanding of the phenomena and to advance effective investigations in the future. In that report, as part (I), following points were mainly concerned, which were definition, classification, nature of flowage, deposition and (topographical and geological) conditions of occurrence of mudflow.
In this report, as part (II), following points are deeply concerned with same aim, which are (vegetational and climatical) conditions of occurrence, frequency and prediction of mudflow.View full abstractDownload PDF (2116K) -
[in Japanese]1980 Volume 21 Issue 4 Pages 216-223
Published: December 30, 1980
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSDownload PDF (1697K) -
[in Japanese]1980 Volume 21 Issue 4 Pages 224-230
Published: December 30, 1980
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSDownload PDF (1514K)
- |<
- <
- 1
- >
- >|