ブックタイトル竹中技術研究報告書No70

概要

竹中技術研究報告書No70

TAKENAKA TECHNICAL RESEARCH REPORT No.70 2014竹中技術研究報告No.70 2014KiK-net (Kunugi et al., 2012). The hadron experimentalhall is located in Ibaraki about 270 km from the epicentre.Figure 3 shows the time histories of the horizontal andvertical ground accelerations recorded at the strong motionstation 0.4 km south from the hadron experimental hall(Hashimura et al., 2011). The peak horizontal and verticalground accelerations at a depth of 6 m below the groundsurface were 3.24 m/s 2 and 2.77 m/s 2 , respectively. The 12-story residential building and the 12-story office buildingare located in Tokyo about 380 km from the epicentre.Figure 4 shows the time histories of the horizontal groundaccelerations recorded at the site of the 12-story residentialbuilding. The peak horizontal and vertical groundaccelerations near the ground surface were 1.75 m/s 2 and0.75 m/s 2 , respectively (Yamashita et al., 2012).Fig. 5 Foundation plan with locations of monitoring devices3.2 Hadron Experimental HallThe hadron experimental hall shown in Fig. 1(f) islocated at J-PARC (Japan Proton Accelerator ResearchComplex) in Ibaraki Prefecture. The soil conditions, thefoundation design and the instrumentation, together withthe results of the long-term monitoring on the settlementand the load sharing, were described in the previous paper(Yamashita et al., 2014).The average pressure over the raft in design was 259 kPain the experimental line, 350 kPa in the beam line and 442kPa in the beam dump. The live loads were relatively large,67 to 84% of the total load, because a large amount of ironand concrete shielding blocks were to be set up after E.O.C.In order to reduce the settlement of the raft foundation dueto the compression of the cohesive soil layers below thedepth of 23 m, a piled raft foundation consisting of 371PHC (pre-tensioned spun high-strength concrete) piles, 22.0to 25.5 m-long and 0.60 to 0.80 m in diameter, wasemployed. The piles were constructed by inserting a coupleof pile segment into a pre-augered borehole filled withmixed-in-place soil cement. Figure 5 shows the foundationplan with a layout of the piles with the locations of themonitoring devices.Figure 6 shows the measured vertical grounddisplacements near the centre of the raft relative to a depthof 80 m. The ground displacement at a depth of 12.5 m wasapproximately equal to the foundation settlement. Thefoundation settlement was 12.4 mm at E.O.C. Thereafter,the settlement incr eased due to the setting up of theshielding blocks. The foundation settleme nt measured justbefore the 2011 off the Pacific coast of Tohoku Earthquakeon March 11, 2011 was 20.7 mm. On April 8, 2011, 28 daysFig. 6Fig. 8Measured vertical ground displacements in beam lineFig. 7 Measured axial loads at pile headMeasured contact pressure with pore-water pressure33