All issues
Volume 42 (2001 - 200･･･
- Issue 6 Pages 335-
- Issue 5 Pages 264-
- Issue 4 Pages 208-
- Issue 3 Pages 140-
- Issue 2 Pages 74-
- Issue 1 Pages 2-
Volume 42, Issue 2
Displaying 1-5 of 5 articles from this issue
- |<
- <
- 1
- >
- >|
-
Takeshi ENDO, Shinichi KAWASHIMA, Masabumi KAWAI2001 Volume 42 Issue 2 Pages 74-87
Published: June 10, 2001
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSThe land subsidence began in the Koutou Distric developing the Shitamachi Lowland in the eastern par of Tokyo Metropolis at about the end of Meiji Era. Since then it had remarkably increased its degree and spread throughout the Lowland as the advance of the confined groundwater withdrawal. Such heavy land subsidence made the area below sea level almost all over the Lowland, especially the area below ebb tide level called Zero-Meter Region in the estuary of the Ara River. Due to spreading of such area below sea level, the Lowland had a lot of disasters of flooding caused by high tide and typhoons. Then to protect the Lowland area from these disasters, the Tokyo Metropolitan Government has systematically constructed and improved high tide countering facilities such as embankments, pumping stations and water gates. Furthermore in order to stop such land subsidence, the national government has restricted groundwater withdrawal for industrial use since 1961 by the Industrial Water Law, and for air conditional use since 1963 by the Law Controlling Pumping of Groundwater for Use in Building. This paper deals with the historical review of the development of land subsidence and its cease in Shitamachi Lowland to prevent land in the Lowland from subsiding again.View full abstractDownload PDF (3842K) -
Motoi INOUE, Takuya YAMADA, Hajime TANAKA, Ryuji KITAGAWA2001 Volume 42 Issue 2 Pages 88-100
Published: June 10, 2001
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSShear structure, clay minerals and carbonaceous materials in the Noda landslide area are studied mainly by X-ray diffractometry (XRD). The Noda landslide area is located in the central Chugoku, Japan and is underlain by the Triasic sedimentary rocks of Nariwa group. The sliding surfaces were confirmed in excarvated wall of drainege well. The specimens were obtained from the boring core and oriented block samples were obtained from drainege well. Carbonaceous materials were extracted from coaly mudstone. Various kind of deformation textures are confirmed through examinations of polished surfaces of oriented block samples. The obtained textures are well correlated with those of experimemtally established shear textures such as D shear, P shear and Riedel shear respectively.
Illite, chlorite, smectite, vermiculite and kaolin minerals are recognized in the samples. The amount of smectite increases with closing to the sliding surface. It is considered that smectite, vermiculite and kaolin minerals were formed through the weathering process whereas illite which occurred commonly with chlorite were representative constituent of the host sedimentary rocks.
The value of d (002) of carbonaceous materials is in the range of 3.40Å to 3.57Å It is to be noted that the d (002) value near the sliding surface is smaller than those of the others indicating that the crystalization degree of the carbonaceous materials near the sliding surface is relatively high.
Based mainly on clay minerals, carbonaceous materials and examination of deformation textures, occurrence mechanism of the lamdslide will be discussed.View full abstractDownload PDF (3868K) -
Yasuhito SASAKI2001 Volume 42 Issue 2 Pages 101-113
Published: June 10, 2001
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSThe effect of forests on slope failure prevention at the 1997 Kagoshimaken-Hokuseibu Earthquake was estimated based on the comparison of failure distributions between a young forest and the surrounding mature forest.
Many slope failures have occurred in a young forest near the epicenter of the earthquake, where needle trees were planted several years ago. On the other hand, the density of slope failures in the surrounding mature forest was relatively low. It should be due to the differnece of roots in each forest.
Slope angle, topsoil depth, and soil type along a measurement line in the young forest were investigated. It was clarified that topsoils were relatively deep in the slopes where failure occurred compared with the slopes where failure did not occurred. The stable limit of soil depth is estimated 115cm for the young forest and 140cm for the mature forest in the same slope angle of 46 degrees. The difference of the soil cohesion of each site, that is the effect of tree roots, is estimated 2.65kPa in a case of 0.5 in horizontal seismic coefficient, 46 degrees in slope angle, and 30 degrees in angle of internal friction. This estimated value is similar with some data which have been experimentally obtained by previous studies, and this value corresponds to 0.15 in horizontal seismic coefficient. Tree roots can prevent slope topsoil from failures to some extent in earthquake as well as in rainfall.View full abstractDownload PDF (4210K) -
Analysis of Primary Causes by Disaster Data in the PastTatsuo NOGUCHI, Tomoyasu SUGIYAMA2001 Volume 42 Issue 2 Pages 114-122
Published: June 10, 2001
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSA number of primary causes, mainly topographic and geological factors, are concerned with the occurrence of rock falls and rock slope collapses. Therefore, consideration of these primary causes is important to evaluate the rock slope stability. We analyzed the primary causes aiming to propose a more accurate and practical stability evaluation method of rock slopes along railways. In the former paper, we reported the analysis by the existing stability evaluation methods
In this paper, we extract the primary causes from disaster data in the past and analyze them. In addition, we examine the results of the two analyses. By this examination, we clarify the conditions and factors which are strongly concerned with the occurrence of downfall type rock falls, separation type rock falls and rock collapses, respectively. And we can distinguish the primary causes by their characteristics, which would be classified into the three cases as follows; (1) thc cause being directly concerned with the occurrence of rock falls and rock slope collapses; (2) the one being related to an unstable progression of slope; (3) the one giving influence to railways to different degrees. So we recognize that it is important to consider the characteristics of the primary causes in evaluating the stability of rock slopes.View full abstractDownload PDF (2093K) -
Hiroshi OHSHIMA, Yuji MATSUMOTO, Manabu ICHIHASHI, Hiroshi KAKIHARA2001 Volume 42 Issue 2 Pages 123-130
Published: June 10, 2001
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSThe Shirasu of special geology is distributed over a wide area of south Kyushu. When building the Shinkansen in this area, it becomes key subject that the method of tunnnel construction under the groundwater is used.
This paper describes as three considerations at stages of route plannig and design & construction stage of tunnnel. That are (1) the consideration of vertical location of rail line, and (2) new type permeable roadbed used slag, (3) tunnnel face stability by drain method of well point.View full abstractDownload PDF (1866K)
- |<
- <
- 1
- >
- >|