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Volume 39 (1998 - 199･･･
- Issue 6 Pages 486-
- Issue 5 Pages 414-
- Issue 4 Pages 346-
- Issue 3 Pages 244-
- Issue 2 Pages 174-
- Issue 1 Pages 4-
Volume 39, Issue 3
Displaying 1-9 of 9 articles from this issue
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[in Japanese]1998 Volume 39 Issue 3 Pages 244-253
Published: August 10, 1998
Released on J-STAGE: February 23, 2010
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[in Japanese]1998 Volume 39 Issue 3 Pages 254-260
Published: August 10, 1998
Released on J-STAGE: February 23, 2010
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Takahiro OYAMA, Masahiro CHIGIRA, Naoya OHMURA, Yositomo WATANABE1998 Volume 39 Issue 3 Pages 261-272
Published: August 10, 1998
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSSome mudstone is weathered quickly below the floors of residential houses, even though it is protected against meteorological effects, such as rain, snow, sun shine, etc., and eventually heaves house floors. We investigated one of the ground heavings occurring in the houses built on fresh mudstone of the Miocene Yunagaya Formation and its fill in the Fukushima Prefecture, central Japan, and found that the mechanism of the heaving is the sequence of the oxidation of pyrite contained in the mudstone catalyzed by iron-oxidizing bacteria, dissolution of calcite and other acid-fragile minerals by sulfuric acid from pyrite, upward migration and evaporation of the water containing sulfate and calcium ions, and the crystallization of calcium sulfate (gypsum) which expands the rock to heave the ground surface. The upward migration of the water and the crystallization of gypsum easily occurs in a ventilated space below the house floors, but not outside the houses because of downward migration of rain water in humid regions.
The house we investigated was built on a fill of fresh mudstone blocks 21 years ago, and the floor has heaved several centimeters. The central part of the floor heaved most. We drilled three bore holes and obtained samples from the depth of up to 5.36 m; two from the ground below the floor and the other outside the house. The samples were analyzed for their physical properties, mineralogy, and microbiology.
Below the house floor, the rocks were abundant in gypsum to the depth of 40 cm with a fluffy cover layer consisting of powdery gypsum crystals, a few centimeters thick. The rocks had the suspension pH of 3.5-4 and were relatively dry. Important point was that iron-oxidizing bacteria were concentrated only at the base of this zone. The rocks deeper than 40 cm were essentially absent from gypsum and had suspension pH of approximately 5.
Below the ground outside the house, on the other hand, the fill was almost absent from gypsum and had the suspension pH of 6.View full abstractDownload PDF (3445K) -
Satoru KAWASAKI, Kameichiro NAKAGAWA, Kazuhiro KOIZUMI1998 Volume 39 Issue 3 Pages 273-281
Published: August 10, 1998
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSFrom the viewpoint that the principle of effective stress can apply to rocks, an attempt to estimate coefficients of permeability of rocks was performed by measuring of consolidation phenomenon like soil materials. Specimens were sedimentary rocks, i. e., soft mudstone and hard conglomerate. This attempt led to the conclusion that close agreement between coefficients of permeability measured by isotropic consolidation tests and injection tests was seen. It is a special merit of this estimation method for coefficient of permeability that a triaxial test with a consolidation test is enough to obtain coefficient of permeability without a laboratory permeability test. This simple estimation method is therefore considered one of effective methods.View full abstractDownload PDF (1857K) -
Yoichi OKADA, Kaoru SAKOGAICHI, Tamotsu KIYAMA, Manabu TAKAHASHI, Itos ...1998 Volume 39 Issue 3 Pages 282-286
Published: August 10, 1998
Released on J-STAGE: February 23, 2010
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an Example from Active Fault Systems in the Western Chugoku District, Southwest JapanYuji KANAORI1998 Volume 39 Issue 3 Pages 287-297
Published: August 10, 1998
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSThe two Lake Ohara-Yauneyamanishi and the Iwakuni-Kamine active fault systems are defined as zones composed of active and geologic faults, in the western Chugoku District, based on the distributions of lineaments, geologic faults, and active faults. The Kikugawa and Shibuki faults, which have been previously recognized, are relatively large-scale active faults outside the active fault systems. The average release-rate of the seismic moments of the active faults and fault systems is calculated from the magnitude of destructive inland earthquakes or the average slip-rate of active faults. The amount of seismic moments is given from the calculated average release-rate multiplied by the elapsed period from the latest earthquake event to the present. The magnitude of the probable earthquake that would occur along the active fault or fault system in 1997, which is described as a magnitude potential of the probable earthquake, is converted from the amount of seis mic moments. Taking the obtained magnitude potential into account, the risk of destructive inland earthquakes is assessed for each active fault or fault system, and the assessment is also discussed.View full abstractDownload PDF (3348K) -
Satoru KISHI, Naofumi HAMATANI, Jitsuya NAGATA, Ikuo HARA, Takeshi KUS ...1998 Volume 39 Issue 3 Pages 298-305
Published: August 10, 1998
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSThere is a freshwater lens which is stored in porous Pleistcene Ryukyu Limestone aquifer at Tsuken island in Okinawa prefecture. The volume of the freshwater lens were estimated approximately 97, 000m3 in this study.
In order to avoid the intrusion of saltwater during pumping, a radial well type intake facility with vertical pit (14m in depth and 3.5m in diameter) and four horizontal collector pipes (each 25m in length) was designed and constructed. After that the continuous pumping test during 31 days was proceeded.
As the result, amount of the freshwater yields by the intake facility are 7, 000m3 which correspond to 3.4 times larger than that of a vertical pipe well (150mm in diameter and 27m in length) where located close to the intake facility.View full abstractDownload PDF (1657K) -
Tsuyoshi HARAGUCHI, Takashi NAKATA, Kunihiko SHIMAZAKI, Toshifumi IMAI ...1998 Volume 39 Issue 3 Pages 306-314
Published: August 10, 1998
Released on J-STAGE: March 25, 2010
JOURNAL FREE ACCESSWe invented a new method and equipment necessary for extensive sequence-oriented sampling of unconsolidated Quaternary sediments. This method is which enables us to collect deeper and wider soil sections, is an application of the basic idea of Geo-slicer by Nakata and Shimazaki (1997).
The basic structure of the equipment is simple and is composed of two parts, a sampling box generally made of a long iron sheet pile with flat U-shaped cross section and a shutter of iron plate which covers the open side of the sampling box. In the operation of sampling, a sampling box is driven vertically into ground at first, and a shutter being combined with the box containing samples, and then the both box and shutter are pulled out together from the ground. A vibro-hammer or a hydraulic-hammer common in construction sites is generally used to drive them into ground.
This method was tested at two sites. On the Kamishiro fault, an active fault trace in Hakuba-mura, Nagano Prefecture, on the Itoigawa-Shizuoka Tectonic Line, we successfully extracted two 11m long soil logs 0.35m wide and 12 cm thick. From the 5m deep river bed of the Kyu-Edo in the Tokyo metropolitan area, ten 0.3 m wide, 12 cm thick and 9m deep soil logs were obtained to form an extensive soil section.
Although this sampling method is still to be improved for perfect performance, we realize that this is the most practical sampling method to obtain extensive vertical soil sections of the unconsolidated Quaternary sediments. This method may be most effectively applied in active fault studies, tsunami deposits, tephrochronology, preliminary archeological works as well as many fields of environmental studies.View full abstractDownload PDF (4694K) -
Manabu TAKAHASHI, Ming ZHANG, Tetsuro ESAKI, Kentaro SAKAI1998 Volume 39 Issue 3 Pages 315-321
Published: August 10, 1998
Released on J-STAGE: February 23, 2010
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