Limits...
Earthquake-induced soil displacements and their impact on rehabilitations.

Konagai K - Proc. Jpn. Acad., Ser. B, Phys. Biol. Sci. (2011)

Bottom Line: Therefore one of what required of us is to deduce as much hidden signs as possible from observable changes of landforms.An attempt was made to convert changes in elevation in Eulerian description for images obtained from remote-sensing technologies to Lagrangian displacements, because Lagrangian displacements can directly describe behaviors of soils, which are typically history-dependent.This paper documents some big pictures of earthquake-inflicted landform changes obtained through this attempt.

View Article: PubMed Central - PubMed

Affiliation: Institute of Industrial Science, The University of Tokyo, Japan. konagai@iis.u-tokyo.ac.jp

ABSTRACT
A large earthquake can trigger long lasting geotechnical problems, which pose serious issues on both rehabilitations and land conservations. Therefore one of what required of us is to deduce as much hidden signs as possible from observable changes of landforms. Though serious, damage caused by the October 23rd 2004, Mid-Niigata Prefecture Earthquake has given us a rare opportunity to study the landform changes in mountainous terrain hit by this earthquake. An attempt was made to convert changes in elevation in Eulerian description for images obtained from remote-sensing technologies to Lagrangian displacements, because Lagrangian displacements can directly describe behaviors of soils, which are typically history-dependent. This paper documents some big pictures of earthquake-inflicted landform changes obtained through this attempt.

Show MeSH

Related in: MedlinePlus

Injection pressure-flow curves at different depths.14)
© Copyright Policy - open-access
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3313688&req=5

fig13: Injection pressure-flow curves at different depths.14)

Mentions: After the bottom end of the borehole was isolated with the single packer, injecting water pressure was increased stepwise with each increment ΔP set at about 20 kPa, and the resulting pressure P and flow rate Q were recorded when the flow had reached a quasi-steady-state condition. The data were recorded over a number of increasing and decreasing steps. The data from the injection test were used to determine the effective hydraulic conductivity (k) by means of the following equation as described in the Earth Manual:17)[5]where, L is the length of the isolated bottom end of the borehole, D the diameter of the borehole, and[6]Injected water forces its way through a fractured rock mass, and the increment rate of the hydraulic pressure/head (Eq. [2]) decreases suddenly when the injection pressure exceeds a threshold as shown in Fig. 13. This pressure is referred to as the “critical injection pressure.” Figure 10 summarizes both hydraulic conductivities and critical injection pressures along Borehole A. It is noted that the critical injection pressures were 176 kPa for the borehole segments from 27 to 29 m in depth, immediately above the shear plane, and 241 kPa for the segment from 29 m to 31 m that includes the shear plane in it. Particularly, the flow rate for the segment from 29 m to 31 m did not relax back to zero when the imposed injection pressure was removed. This indicated that when the injection pressure reached its critical value, the water suddenly forced its way into either the surrounding rock or the shear plane fracturing its bond. Thus, there was a concern that the rock mass above the shear plane would move when the open-hole water levels did increase by 24.1 m from the packer-isolated segments level. The Nagaoka Regional Development Bureau of the Niigata Prefectural Government drilled two Boreholes C and D (see Fig. 8) to monitor whether the open-hole water level would increase to that serious level, and whether the boreholes would exhibit signs of increasing inclination.7) An inclinometer was inserted along a notched casing fitted in the borehole, and inclinations were measured at a regular interval of 0.5 m. The records were compiled from 1st September 2005 until the end of 31st May 2006. The open-hole water levels for Boreholes C and D had been about 32 and 27 m below the ground surface levels with semiannual changes of ±2 and ±1 m, respectively. Water levels, reaching their peak values in snow-melting times (May) and immediately before snow times (December), were far below the critical levels, and inclinometer records did not show any sign of a possible rock-mass deformation. With these data compiled, the Nagaoka Regional Development Bureau, Niigata Prefectural Government, could start reconstruction of the interior of the tunnel after the 2 year careful investigation.


Earthquake-induced soil displacements and their impact on rehabilitations.

Konagai K - Proc. Jpn. Acad., Ser. B, Phys. Biol. Sci. (2011)

Injection pressure-flow curves at different depths.14)
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3313688&req=5

fig13: Injection pressure-flow curves at different depths.14)
Mentions: After the bottom end of the borehole was isolated with the single packer, injecting water pressure was increased stepwise with each increment ΔP set at about 20 kPa, and the resulting pressure P and flow rate Q were recorded when the flow had reached a quasi-steady-state condition. The data were recorded over a number of increasing and decreasing steps. The data from the injection test were used to determine the effective hydraulic conductivity (k) by means of the following equation as described in the Earth Manual:17)[5]where, L is the length of the isolated bottom end of the borehole, D the diameter of the borehole, and[6]Injected water forces its way through a fractured rock mass, and the increment rate of the hydraulic pressure/head (Eq. [2]) decreases suddenly when the injection pressure exceeds a threshold as shown in Fig. 13. This pressure is referred to as the “critical injection pressure.” Figure 10 summarizes both hydraulic conductivities and critical injection pressures along Borehole A. It is noted that the critical injection pressures were 176 kPa for the borehole segments from 27 to 29 m in depth, immediately above the shear plane, and 241 kPa for the segment from 29 m to 31 m that includes the shear plane in it. Particularly, the flow rate for the segment from 29 m to 31 m did not relax back to zero when the imposed injection pressure was removed. This indicated that when the injection pressure reached its critical value, the water suddenly forced its way into either the surrounding rock or the shear plane fracturing its bond. Thus, there was a concern that the rock mass above the shear plane would move when the open-hole water levels did increase by 24.1 m from the packer-isolated segments level. The Nagaoka Regional Development Bureau of the Niigata Prefectural Government drilled two Boreholes C and D (see Fig. 8) to monitor whether the open-hole water level would increase to that serious level, and whether the boreholes would exhibit signs of increasing inclination.7) An inclinometer was inserted along a notched casing fitted in the borehole, and inclinations were measured at a regular interval of 0.5 m. The records were compiled from 1st September 2005 until the end of 31st May 2006. The open-hole water levels for Boreholes C and D had been about 32 and 27 m below the ground surface levels with semiannual changes of ±2 and ±1 m, respectively. Water levels, reaching their peak values in snow-melting times (May) and immediately before snow times (December), were far below the critical levels, and inclinometer records did not show any sign of a possible rock-mass deformation. With these data compiled, the Nagaoka Regional Development Bureau, Niigata Prefectural Government, could start reconstruction of the interior of the tunnel after the 2 year careful investigation.

Bottom Line: Therefore one of what required of us is to deduce as much hidden signs as possible from observable changes of landforms.An attempt was made to convert changes in elevation in Eulerian description for images obtained from remote-sensing technologies to Lagrangian displacements, because Lagrangian displacements can directly describe behaviors of soils, which are typically history-dependent.This paper documents some big pictures of earthquake-inflicted landform changes obtained through this attempt.

View Article: PubMed Central - PubMed

Affiliation: Institute of Industrial Science, The University of Tokyo, Japan. konagai@iis.u-tokyo.ac.jp

ABSTRACT
A large earthquake can trigger long lasting geotechnical problems, which pose serious issues on both rehabilitations and land conservations. Therefore one of what required of us is to deduce as much hidden signs as possible from observable changes of landforms. Though serious, damage caused by the October 23rd 2004, Mid-Niigata Prefecture Earthquake has given us a rare opportunity to study the landform changes in mountainous terrain hit by this earthquake. An attempt was made to convert changes in elevation in Eulerian description for images obtained from remote-sensing technologies to Lagrangian displacements, because Lagrangian displacements can directly describe behaviors of soils, which are typically history-dependent. This paper documents some big pictures of earthquake-inflicted landform changes obtained through this attempt.

Show MeSH
Related in: MedlinePlus