Track record

Characteristics

ＳWE-ＳＳＲＴ

Summary

Seismic While Excavating using Shallow Seismic Reflection survey for Tunnels

■SWE-SSRT: 5 tunnels ■Conventional SSRT in tunnel: 11 tunnels (including TBM) ■Conventional SSRT from outside of tunnel: 5 tunnels

What is the SWE-SSRT? ■SWE-SSRT uses the excavating blasts in multiple-steps as the seismic source which allows the continual survey and prediction　of tunnel geological conditions while excavating.

■ Seismic source is the excavating blasts（about 250 milliseconds delay） ■ Continual survey and　prediction ahead of tunnel face without interruption of tunnel excavating work ■ A GPS time signal transmission device and Rubidium atomic clock are used to synchronize the equipment internal clock ■ The cost is about half that of the previous method

Example of SWE-SSRT results　and geological revaluation on Furue-Minami tunnel

The 13th Infrastructure Technology Development Award 2011- excellence prizes -

Time　recording device inside tunnel using a Rubidium clock

Rubidium clock Recoder(12ch)

geophones

Rubidium clock Recoder(12ch)

geophones

Rubidium clock Recoder (12ch)

geophones

Rubidium clock synchronizing GSP time signals at site office

GPS

Tunnel  face  at  STA.496+95

Muddy  sandstone  rich Slate

SWE -­‐ SSRT  line -­‐ 9  Vp=4000m/s

STA.495+95 STA.495+10

End  of    this    ConstrucIon STA.  493+99

Sandstone  rich Furue  thrust  fault

（ assumed ）

Forward    analysis Backward  analysis Fractural  zone   related  to  Furue   thrust  fault  ?

： Heavy  reflecIon  Level

Comparison  of  the  SWE -­‐ SSRT   results  and  excavaIng  record       Review  of  predicIon  results  

(revaluaIon) Water  fall  from  the  roof     aWer  excavaIon

Sandstone  rich Muddy   sandstone Fractural

boundary

Fractural  bed  boundary  of   sandstone  rich  zone  and   muddy  sandstone  zone

Line -­‐ 7,8 Line -­‐ 9 Forward    analysis SWE -­‐ SSRT  Line -­‐ 7,8  Vp=4000m/s

Fractural  zone  including   underground  water

地層境界 砂岩優勢

泥質砂岩

7,8 9