Calibration of Strain Gauged Square Tunnels for Centrifuge Testing

Abstract

Access from the University of Nottingham repository:http://eprints.nottingham.ac.uk/34803/1/2016%20-%20Tsinidis%20-%20Geotechnical %20and%20Geological%20Engineering%20-%20Calibration%20of%20Strain%20Gauged %20Square%20Tunnels%20for%20Centrifuge%20Testing.pdf Copyright and reuse:The Nottingham ePrints service makes this work by researchers of the University of Nottingham available open access under the following conditions. This article is made available under the University of Nottingham End User licence and may be reused according to the conditions of the licence. For more details see: http://eprints.nottingham.ac.uk/end_user_agreement.pdf A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription.For more information, please contact eprints@nottingham.ac.uk aiming at the investigation of the seismic response of underground strcutures and tunnels 35 (Shabayama et al., 2010, Lanzano et al., 2012Cilingir and Madabhushi, 2011a, 2011b, 36 2011c Chian and Madabhushi, 2011;Chen et al., 2013;Chen and Shen, 2014; Tsinidis et al., 37 2015a;Ulgen et al., 2015;Abuhajar et al., 2015). Experimental studies have been also 38 conducted for the evaluation of the seismic behavior of actual case studies during retrofitting 39 projects (Adalier et al., 2003;Chou et al., 2010). Although there are some published 40 experimental programs investigating the behaviour of rectangular embedded structures, where 41 strain gauges were employed to record the lining forces (e.g. Chen and Shen, 2014), no clear 42 reference is given for the calibration of these crucial instruments. 43 Calibration of Strain Gauged Square Tunnels for CentrifugeThis lack of reference, along with the need for more artificial 'case studies', motivated the 44 realisation of the collaborative experimental project TUNNELSEIS, through the EU funded 45 research project SERIES. Within the framework of this research project, the seismic response 46 of shallow square tunnels embedded in dry sand was investigated by means of dynamic 47 centrifuge tests. The tests were carried out at the geotechnical centrifuge facility of the 48 Schofield Centre, University of Cambridge. This technical note summarizes the calibration 49 procedure followed for the resistance strain gauges, which were used to record the lining 50 forces and highlighting the significance of advanced numerical simulation in the calibration 51 procedure of complex construction models. 52 53 Description of centrifuge tests undertaken 54Three dynamic centrifuge tests were performed on square tunnel models embedded in dry 55Hostun HN31 sand, reconstituted at two different relative densities of about 50 % and 90 %. 56Two square tunnel models were manufactured and tested, namely: a relative rigid one 57 having a thickness of 2 mm and a more flexi...

On the dynamic response of square tunnels in sand

“…This may explain part of the differences between the numerical and the experimental results. Moreover, the calibration procedure was done carefully following the procedure outlined in Tsinidis et al (2016) (reference [51] in the revised manuscript). However, there are always unavoidable uncertainties related with the above procedure, potentially causing some differences with the numerical results.…”

“…However, there are always unavoidable uncertainties related with the above procedure, potentially causing some differences with the numerical results. Actually, the large deviation in the recorded axial forces in the symmetrical positions SG-A1 and SG-A3 is related to the large difference observed in the calibration factors of the particular strain gauges ( [51]). Accounting for the complexity of the investigated problem, the comparisons between the experimental and the numerical results seem to be fair enough.…”

“…Although the calibration of the strain gauges was done very carefully (i.e. [51]), there are always some unavoidable uncertainties related with the calibration of the above instruments, potentially causing some differences between the experimental and the numerical results." Page: 15 lines: 2-4 "The large deviation between the recorded axial forces in the symmetrical positions SG-A1 and SG-A3 is related to the large difference observed in the calibration factors of the particular strain gauges [51].…”

“…Although the calibration of the strain gauges was done very carefully (i.e. [51]), there are always some unavoidable uncertainties related with the calibration of the above instruments, potentially causing some differences between the experimental and the numerical results. "…”

“…All the instruments were properly calibrated before and checked after testing. Regarding the strain gauges, their calibration was made carefully for simple static loading patterns using the procedure outlined in Tsinidis et al[51]. Typical models layout (h = 60 mm for Test 1, 100 mm for Test 2)…”