Geoscience Reference
In-Depth Information
Fig. 16.5. Mechanism of deformation of an embankment due toliquefaction of the soil
under the embankment
Tie rod
Densification or
solidification
(1) Sheet piling for embankment
(2) Densification or solidification
at toes of embankment
HWL
Gabion
Sheet pile
Drain
Drain trench
(3) Lowering of water level
by trenches and pipes
(4) Lowering water level by gabion
Fig. 16.6. Remediation methods for existing embankments
liquefaction is possible during future earthquakes. As liquefaction may damage railway
embankments, a sheet-pile enclosed method has been developed to protect them as illus-
trated in Figure16.6(1). The design method of the remedial measure was based on sev-
eral shaking table tests and analyses. This method has been applied at several sites. The
dimensionsofthesheetpilesandtie-rodsdifferaccordingtoconditionsofthegroundand
embankments. At an embankment with a height of 8m and a width of 32m, liquefiable
layers were deposited to a depth of about 14m. For this embankment, sheet piles with
lengths of 18.5 and 16.5mwereinstalledat both toes and connected withtie-rods.
6.2.2. Yodogawa River dike (partially quoted from TC4, 2001)
The 1995 Kobe earthquake caused extensive damage to the Yodogawa dike. During the
restoration work, a countermeasure against liquefaction-induced settlement was applied
(TC4, 2001). At the Nishijima dike section, the outer part of the dike was not damaged.
Only the inner was rebuilt. The stability of this part was improved by installing double
rows of steel sheet piles at the toeand placing gravel between the rows.
6.2.3. Arakawa River dike (partially quoted from JGS, 1998)
ThedeepmixingmethodwasappliedtotheembankmentoftheArakawaRiverembank-
ment in Tokyo, as shown in Figure16.6(2). A loose sand layer where liquefaction was
anticipated was3to6mthick.Itwasplanned tousethedeep mixingmethod forawidth
