| Reliability of Field-Reported Foam-Conditioning Parameters in EPB Tunnelling: Per-Ring Evidence from Isfahan Metro Line 2 |
| کد مقاله : 1042-IMEC15 (R1) |
| نویسندگان |
|
behnam ebrahimy *1، Ali Koohsari2، Mohammad Hossein Mokhtarzadeh1، Mohammad Mahdi Abbasi1، Amir Hossein Kalhor1 1Faculty of Engineering, Tarbiat Modares University 2Department of Civil Engineering, Sharif University of Technology |
| چکیده مقاله |
| Foam-conditioning records are widely used to describe earth-pressure-balance (EPB) tunnelling practice, although the quantities reported by machine channels and shift logs are not always directly comparable. This study examines their consistency for the 6.9 m S-227 shield on Isfahan Metro Line 2. Machine channels labelled foam injection ratio (FIR) and foam expansion ratio (FER) were compared with the contractor’s shift log and estimates recomputed from per-ring mean flow and advance-rate channels. After screening physical operating records without imposing limits on the reported FER channel, 1835 rings were retained, including 688 with all three records. Shift-log FER agreed closely with the recomputation: the median signed relative difference was 1.27%, the median absolute relative difference was 1.30%, and Spearman’s correlation was 0.96. For the machine FER channel, the median paired ratio was 4.93 and the correlation was −0.76. Reported FIR exceeded the recomputation by median paired factors of 1.22 for the machine channel and 1.23 for the shift log. These differences are consistent with differing averaging conventions, although the available ring summaries cannot establish their cause. Across the retained drive record, median recomputed FER was 4.6 and 67% of rings had FER below 5. EFNARC ranges are treated as indicative guidance, so this observation alone does not establish inadequate conditioning. The comparison is concentrated in the early drive, and the five available grading samples provide limited spatial coverage. Field reports should identify the source, pressure basis and averaging convention of conditioning parameters and preserve the channels needed to reproduce them. |
| کلیدواژه ها |
| EPB tunnelling, soil conditioning, foam injection ratio, foam expansion ratio, field data validation |
| وضعیت: پذیرفته شده برای ارسال فایل های ارائه پوستر |
