1 Investigation of vibration properties of the KEKB tunnel after the Great East Japan Earthquake Contents Situations after the earthquake Geological survey GM properties of the KEKB tunnel KEK Hiroshi Yamaoka

2 NSEWUD （ Acceleration response ） The Great East Japan Earthquake （ Time ） Tsukuba Acc. (gal) Frequency (Hz)

3 Damage at the KEB tunnel Water leakage Displacement Displacement of Exp. joint Outside Magnets/equipments: Not so big damages. Serious damage  Magnet alignment. Made by Masuzawa-san,

4 Lifting a cavity Sit Crane truck ~20  m HLS sensors 20 seconds [  m] 4sec. A few cars passed Vibration properties after the eartquake Many cars passed Bus/truck passed Vibrations on the QB magnet(Horizontal) D3

5 Vibrations affect by crane operation at Tsukuba exp. hall. Slow drive Slow lowering Just begin lowering

6 - Horizontal vibrations became larger than the previous data. - Around 1Hz vibration is large. - Vertical vibration isn't so different.  The tunnel its-self or environment of the tunnel might have any damages. Compare vibrations on D3 floor to the previous data NSEWUD D3

7 To understand the present condition of the tunnel; - Are there any damages on the tunnel its-self?  Check: Cracks, Exfoliations, Water leakages, Sinking, etc.  Visual observation, Ultra-sonic sensor. - Are there craves/air-gap around the tunnel? (Not finished)  If they are existing, the tunnel is supported unstably. It cause un-uniform deformation of the tunnel.  Microwave radar sensor - What is the geological features/strength surrounding the tunnel?  To know the soil properties and strength.  It is possible to investigate liquefaction.  Soil boring test, Swedish weight sounding test.

8 Configuration of the KEKB tunnel - No piling below the floor at arc-section. - Refilled soil filled after complete the tunnel. Walls to prevent a landslide. TP+30m TP+27m TP+22.8m TP+17.7m

9 Inspection of cracks on the KEKB walls. Result: - Need to keep observation that cracks grows or not.  Most of the cracks have been repaired.

10 Soil boring test, Swedish weight sounding test. B1 S1 S11 S2 S3 S4 S5 B2 S6 S7 S8 S10 S9 B1S1S11S12S2 Ceiling of the tunnel (T.P.+22.8m) the tunnel floor level (T.P.+17.7m) Refilling soil layer (Sand+Silt) Silt layer (T.P.+30m) Evaluation of Liquefaction If FL<1: It will cause liquefaction  If earthquake larger than 150 gal, liquefaction will be occurred.  Liquefaction was occurred at the earthquake.  Refilling soil layer is very soft: Low N-value.  The tunnel is in the soft layer. FL value Depth (m) Criteria(Liquefaction)

11 Swedish weight sounding test (Hard geology layer)

12 Swedish weight sounding test (Soft geology)

13 Results of geological survey To understand the present condition of the tunnel; 1. Are there any damages on the tunnel its-self? (Result) - There are a lot of cracks larger than allowable width (>0.3mm).  Cracks on the wall have been almost repaired at present.  Some cracks remained to keep observation. Cracks grow or not. 2. Are there craves/air-gap around the tunnel? (Result) To inspect craves/air-gap, thickness of the tunnel wall is too thick by radar sensor.  We have looking for another sensor/method. 3. What is the geological features/strength surrounding the tunnel? (Result) Geological features was measured to be very soft.  It's easy to transfer noises from the outside, and vibration become big. Liquefaction will be occurred if an earthquake is larger than 150 gal.  This makes that soil is softer.  In fact, liquefaction was occurred in KEKB tunnel by the earthquake.

14 Comparison of ground motion among some places in KEKB tunnel Tsukuba (I.R.) OhoFuji Nikko

15 lowest amp. Tsukuba (I.R.) OhoFuji Nikko Integrated amplitudes Noisy due to traffic

16 Observed vibration around 1Hz Nikko Tsukuba (I.R.)

17 Observed vibration around 8Hz Tsukuba (I.R.) Fuji Fuji-Nikko Nikko-Tsukuba

18 高エネルギー物理学研究所トリスタン基本計画（中間報告書） 昭和 57 年 2 月 12 日 日建設計より FEM model for geology (Mass-spring model) Mode shapes/Period Fixed G.L m Mode Period 1 st nd rd th 0.13  Resonant peaks, ~1Hz and ~8Hz, might be resonance of the geology. These parameters are input.

19 30Hz 65Hz Concrete E=30GPa Density=2.3 Damping= 2% Natural frequencies Fixed Weight of Concrete shield 300tons Weight of magnets 2tons 20m Tsukuba (I.R.) Vibration at Tsukuba(I.R) Resonances are existing >30Hz. ? ? It was understood that the resonant peaks larger than 30Hz come from the resonance of the bridge. This makes larger integrated amplitude. Reinforcement is planning.

20 Conclusion - The earthquake affected to the vibration properties at KEKB tunnel.  Sensitive to noises, Larger vibration.  This is due to the change of geological properties surrounding the KEKB tunnel.  We have made the geological survey.  The KEKB tunnel need to keep observation of the conditions.  Cracks on the tunnel walls, vibration properties.  Geological features was measured: Very soft.  Liquefaction will be occurred: > 150 gal. - Some resonant peaks are investigated. ~1Hz, ~8Hz at the tunnel, >30Hz at I.R. bridge.

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22 スウェーデンサウンディング ・ N 回回転したときの沈下量を測定 40kg 20kg 30kg

23 Feb. 1 st,'12 KEKB 床面での振動 Recent ground motion around IR region

24 > 0.1Hz > 1.0Hz > 10Hz P1(-10m)P2(GL) P3P4 D3 15m 4m Higashi- Odori (Boulevard ) The number of automobiles （ 10 min./every hr.) Weight(Trucks+Big trucks ） Direction: UD