All issues
Volume 41, Issue 1
Displaying 1-5 of 5 articles from this issue
- |<
- <
- 1
- >
- >|
-
Hideo KIYA2000 Volume 41 Issue 1 Pages 2-11
Published: April 10, 2000
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSSoil ground is a general term for cohesive soil, sandy soil, gravelly soil and other special types of soils such as pyroclastic deposit, which are commonly featured by low strength. One of the most important problems for tunnel construction is the face wash-out due to water gush at the soil ground, which is composed of granular soils other than cohesive soil. Therefore, the face stability is a condition required for tunnel support design for granular soil ground. The author performed a statistical analysis of some tunnel construction data on sandy ground, model experimental study and numerical parametric analysis on the critical condition, in order to make clear distinction among changes in face state.
In this paper, the author suggests a following classification standard of sandy ground conditions for railway tunnels from the results of the above research.
[IN]: ground state of considerably stable face
[IL]: ground state of unstable face to cause wash-out due to small changes in face stability balance for the worse
[SL]: ground state of extremely unstable face, worth than [IL] for which serious troubles are foreseeable in excavation
The boundary between for the ground classes [IN] and [IL] is distinguished by the fine grain content (Fc) of soils; ground condition of class [IN] having Fe≥10%. The boundary of [IL] and [SL] is also distinguished by the relative density (Dr) of soils; class [SL] having Dr<80%. Above classification can be applied to the conditions where the pressure head (WL) from the tunnel face center is WL<10m.
Further, the author suggests a method to classify different types of soil ground, that is obtained from experimental studies of evaluation of granular soil except sandy soil and a consideration of characteristic conditions of layered ground structures with complicated geological conditions.View full abstractDownload PDF (2264K) -
Hirokazu ISHIHARA, Takeshi KAMEI, Tadashi NAKAMURA2000 Volume 41 Issue 1 Pages 12-23
Published: April 10, 2000
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSThis paper describes an integrated study on sedimentary environments of Holocene deposits near Lake Jinzai in the Izumo Plain using CNS elemental analysis and its application to geotechnology. The weight ratios of total organic carbon to pyrite sulfur (C/S ratio) and total organic carbon to total nitrogen (C/N ratio) and total sulfur (TS) are useful for evaluating sedimentary environment. The geological processes of the Lake Jinzai area during the Holocene is also described.
In addition, the influence of variation of calcite (CaCO3) content on observed strength-deformation characteristics with depth is investigated. Quantitative relationships between CaCO3 content and strength-deformation characteristics for cohesive soils of the Lake Jinzai area have been developed as a result of this work, i. e, strength-defomation characteristics increase as the CaCO3 content of the soils increases. Finally, this study emphasizes to geotechnical engineers the necessity of integrated evaluation for the refinement of construction technology.View full abstractDownload PDF (2899K) -
Senro KURAOKA, Keiichi MONMA, Haruo SHUZUI2000 Volume 41 Issue 1 Pages 24-33
Published: April 10, 2000
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSJoints and faults often control stability of rock slope. Although various numerical techniques have been developed in order to model these discontinuities, it is still extremely difficult, if not impossible, to predict behavior of jointed rocks slopes due to lack of reliable geological data. The objective of this paper is to report an example of how numerical analysis may be applied to extract useful information when data required for the analyses are limited. To this end, a rock slope with distinct joint sets was selected and the distinct element method (DEM) was used to find factors and mechanisms that control the stability rather than predicting the stability with safety factors. There are, however, a number of factors that may affect the stability and therefore a number of parametric simulations may be needed. In this study, factorial design method was applied to effectively determine the factors that have significant influence on the stability with minimum number of simulations. The results indicate important factors that can be useful in focusing location of further investigation and designing counter-measures to stabilize the rock slopes.View full abstractDownload PDF (2543K) -
Kazushi MORI2000 Volume 41 Issue 1 Pages 34-40
Published: April 10, 2000
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSIn the Sahel region, spread in West Africa, groundwater in the alluvial plain of wadi is very important water resources for dry-season irrigation. Determining the depth to bedrock and depth to water table by geophysical methods makes possible to decrease the costs and labours for well construction. The author carried out handy seismic refraction method by sledgehammmer striking, for explosives such as dynamites commonly used for seismic sources are hard to available in this region.
Determined depths of basement and water table by seismic method are sufficiently analogous with actual depths measured in the boreholes. This handy seismic method is suitable for determining depths of basement and water table shallower than twenty meters, and applicable widely in the Sahel region for preliminary study of shallow groundwater resources.View full abstractDownload PDF (1362K) -
Akio CHO, Ziqiu XUE, Makoto TAKAHASHI2000 Volume 41 Issue 1 Pages 41-47
Published: April 10, 2000
Released on J-STAGE: February 23, 2010
JOURNAL FREE ACCESSA 750m deep borehole was drilled in Tsukuba city for an underground water level obeservation well. Using this borehole, hydraulic fracturing test, ASR (Anelastic Strain Recovery) tests and DSCA (Differential Strain Curve Analysis) tests were performed at a depth around 670m, to measure in-situ underground stress. From a break down pressure of 49MPa, we estimated the maximum and minimum horizontal principal stresss were about 40MPa and 30MPa, respectively. In ASR tests, the maximum and intermediate principal strains were located horizontally and the minimum principal strain was located vertically. Assuming the vertical stress was overburden pressure (12MPa), the maximum and minimum horizontal principal stresses were 21MPa and 15MPa, respectively.
The underground stresses around Tsukuba city is in the condition that two principal horizontal stresses are greater than a vertical stress. This underground stress condition is different from the results of stress relieving method conducted on many underground openings in Japan.View full abstractDownload PDF (1275K)
- |<
- <
- 1
- >
- >|