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Volume 46 (2005 - 200･･･
- Issue 6 Pages 311-
- Issue 5 Pages 250-
- Issue 4 Pages 190-
- Issue 3 Pages 115-
- Issue 2 Pages 72-
- Issue 1 Pages 2-
Volume 46, Issue 5
Displaying 1-6 of 6 articles from this issue
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Akito NAKASUJI2005 Volume 46 Issue 5 Pages 250-255
Published: December 10, 2005
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESS“Sediment disaster prevention law”has become effective in Japan since April 1, 2001. It has been equipped with a newly-developed method to determine disaster-vulnerable areas. This methodology have a problem that it does not consider unique and complex characteristics of each individual slope or stream.
Hazard maps, without mentioning, must provide the information of disaster prediction to their users. In that sense, most sediment disaster hazard maps currently distributed among citizens in Japan are not“sediment disaster hazard maps”; they are“sediment disaster-vulnerable area maps. ”Some technical reasons why the study of the hazard mapping for sediment disasters has been less advanced include (1) there are less scientific records of actually occurred disasters compared to volcanic hazards and (2) the causing factors of sediment disasters are more complex than those of flood disasters, such as water level, flow velocity, etc.
In addition to the technical problems mentioned above, there is an organizational problem in the current way of utilizing hazard maps. In the case of the storm disaster taken place in Miyagawa village, Mie prefecture in September 2004, many people were killed by the disaster due to the late issuing of evacuation order, even though the residents were provided with an accurate disaster susceptibility map of the village. Information about the disaster-susceptible areas and evacuation sites on hazard maps prepared by municipalities in Japan is rarely taken into account in their regional disaster prevention plans including evacuation training. Therefore, how to improve the organizational aspect of the utilization of hazard maps has become very important issue in the field of hazard mapping, as well as the methodological improvement of hazard mapping.View full abstractDownload PDF (2876K) -
Toshifumi IGARASHI, Ryosuke SAITO, Shunsuke NAGASAWA, Kuniomi ASAKURA, ...2005 Volume 46 Issue 5 Pages 256-264
Published: December 10, 2005
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSColumn leaching experiments using pyrite-bearing andesite, calcite-bearing basalt, and pyrite- and calcite-bearing mudstone were carried out to elucidate the neutralization of acid water resulting from pyrite oxidation by pH-buffering minerals. The results showed that the solubility equilibrium of calcite controlled the water quality of the effluent from the column for basalt, and that both calcite dissolution and pyrite oxidation occurred at approximately the same rate for mudstone unless the product of the calcium and sulfate activities exceeded the solubility of gypsum. Plagioclase was expected to act as an acid-buffering mineral for the andesite, based on the chemical properties of the effluent. This indicates that the pH-buffering minerals commonly observed in rocks and soils, such as calcite, may effectively neutralize the acidic water resulting from pyrite oxidation. The use of these minerals may lead to a rationalization of the embankment structure of pyrite-bearing rocks.View full abstractDownload PDF (1431K) -
Tetsuya FUKUDA, Yasuhito SASAKI, Yasuhiko WAKIZAKA2005 Volume 46 Issue 5 Pages 265-279
Published: December 10, 2005
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSThe aerial photograph interpretation of 964 slope failure cases proved the following facts. (1) The angle of elevation formed by failed slope height and length, θ, shows normal distribution when the failed slopes were divided into some group by an appropriate combination of failure trigger, area/geology, topography, and vegetation. (2) In case of rainfallinduced failures, the factors of area/geology and/or topography influence the distribution of θ. (3) On the other hand, in case of earthquake-induced failures, the influence of the above factors on the θ distribution is very small. Using the above θ distributions, we developed a stochastic simulation system for predicting hazard areas of shallow slope failure debris.
The algorithm of this simulation is based on the following steps. (1) Get the distance of hazard areas of “Random walk” was calculated from Monte Carlo method using probability distribution of θ. (2) Random walk was performed until the distance of hazard areas. (3) And these processes were repeated.
The result of this simulation roughly corresponded with past cases of slope failures. This simulation is an effective method of hazard mapping on shallow slope failure.View full abstractDownload PDF (3124K) -
Takato TAKEMURA, Aliakbar GOLSHANI, Masanobu ODA, Ken-ichiro SUZUKI, S ...2005 Volume 46 Issue 5 Pages 280-286
Published: December 10, 2005
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSThe excavation of underground openings results in a change in stress distribution which may lead to the development of a plastic zone around the tunnel, termed as excavation disturbed zone. To characterize the behavior of excavation disturbed zone as well as host rock, time influence on the mechanical properties of rock is of great importance. For instance, when considering deep excavations for disposal of high-level radioactive waste in rocks, assessment of the timedependent stability of rock mass under deep geological environment is necessary. With this in mind, creep tests were carried out on Inada granite under confining pressure: 40 and 80 MPa for dry and wet samples. The conclusions are summarized as follows:
1) Shear zone developed just before tertiary creep is similar to the onset of the macroscopic failure under conventional loading condition (short term).
2) Crack evolution decreases with confining pressure increasing. Furthermore, presence of water accelerates the cracks growth.
3) Time to failure depends on the clay mineral content. In other words, in underground spaces, clay content of surrounding rock is considerably influenced the long-time stability of the site.View full abstractDownload PDF (1565K) -
Pucai YANG, Noboru YOKOYAMA, Kimio INOUE, Kousuke AMINO2005 Volume 46 Issue 5 Pages 287-292
Published: December 10, 2005
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSThe climactic eruption of Mt. Pinatubo in the Philippines on June 15, 1991, formed a summit crater lake with a diameter of about 2, 000 meters and a depth of 600 meters. A radial drainage, which originated from the Crater Lake, deeply eroded the young pyroclastic deposits, thereby providing advantageous conditions in facilitating slope failures and lahars. Steep valley wall failures and subsequent lahars have posed a considerable threat to the downstream. On July 10, 2002, during an intense storm event, a huge lahar along the Bucao River occurred, which was presumably from the summit Crater Lake breach at the Maraunot Notch; this provoked wide public attention. Consequently, aerial and site investigation was immediately carried out to understand the Crater Lake breach mechanism and the reason for the resultant lahars. This paper summarizes partly the observations and gives the conclusions about the breakout of the Crater Lake and its influence on the lahars around Mt. Pinatubo, geological explanation of the causes of the Crater Lake breach and suggestion on mitigation methods for further breakout of the Crater Lake.View full abstractDownload PDF (3276K) -
Masahiro CHIGIRA, Akito NAKASUJI, Kenzo FUKUI, Atsushi TANASE, Hiroshi ...2005 Volume 46 Issue 5 Pages 293-302
Published: December 10, 2005
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSThe 2004 Mid Niigata prefecture earthquake (M6.8) occurred on 23rd in October 2004, severely damaging infrastructures in this area by strong shaking, liquefaction, and landslides; particularly a large number of landslides occurred in the mountainous areas in and around Yamakoshi Village, which has been now merged with Nagaoka city.
The Japan Society of Engineering Geology and the Japanese Landslide Society made a joint investigation team and made a ground survey in the affected mountainous areas from 5th to 7th in December, and reported the results at the special symposium organized by both the societies. After the earthquake, the affected area experienced heavy snow from December 2004 to March 2005; the snowfall was a record within recent 19 years. Almost all snow melted before the middle of May 2005, and the joint investigation team made a ground survey again from 21st to 25rd in May 2005 to check the effect of snow on landslides or destabilized slopes. The effects of the snow and its melting on the slopes were not large, but the reconnaissance team has found precursory features of future landslides or sediment yielding : new cracks and widening of existing cracks which were made by the earthquake. Long-term monitoring is essential for these features to mitigate future disaster. Here we report the results of our investigation on the change of the landslides or destabilized slopes between just after the earthquake and after the snow melt as well as newly visited landslide sites.View full abstractDownload PDF (9817K)
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