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 2014between the raft and the soil as well as the pore-water pressure beneath the raft were also measured during earthquakes incommon starting time with the accelerometers. The triggering acceleration is 0.004 m/s 2 on the B3F and the sampling rate isemployed at 100 Hz. Minimum available values of acceleration, strain and earth pressure are 2.4×10 -4 m/s 2 , 1.0×10 -4μand 5.0×10 -6 kPa, respectively. Measuring system is consisted of IC Card Data Logger, Dynamic Amplifier and Power Unit as shownin Table 1 and Photo 2 .Table 1 Property of measuring devicesDeviceIC Card Data LoggerServo AccelerometerDynamic AmplifierStrain gaugeEarth pressure cellPiezometerPropertyAD converter 24bit, Sampling 100HzTri-axis, Full scale:±2000galLVDT. Frequency Response:20HzLVDTLVDT, Capacity:200, 300kPaLVDT, Capacity:100kPaPhoto 2 Layout of measuring system4 LONG-TERM STATIC MEASUREMENT RESULTSFigure 3 shows the time-dependent load sharing among the pile load (kPa), the earth pressure and the water pressure in thetributary area of pile C. The earth pressure is an average of the measured values from D7 and D5. The pile load (kPa) isestimated by the axial force of the pile divided by the tributary area of 39 m 2 . The ratio of the load carried by the pile to thetotal load is 40% (42%) at the end of the construction and 47% (50%) about five years after that time. Here, the value inparentheses is the ratio of the load carried by the pile to the effective load. The ratios were almost same before and after the2011 off the Pacific coast of Tohoku Earthquake.Figure 4 shows the time-dependent earth presure acting on the embedded side walls. The earth pressure was stable after theearthquake. The value of earth pressure from D8-2 was found to be evaluated approximately as follows; an unit weight (17 kN/m 3 )×depth (11.2 m)×coefficient of earth pressure K (0.3) is 57 kPa.Fig. 3 Time-dependent load sharing between piles and raft around pile C (5-D street)44