Robbins has claimed the fastest weekly progress rate achieved with any of the 14 TBMs on Phase 2 of New Delhi metro - 168 rings, or 202m, with the first of its two shields to complete excavation.rnThe 6.52m diameter EPBM, being driven by JV contractor Continental Engineering Corp (CEC/Soma, achieved the reported fastest advance rate during its second 1 km long bore, which completed on 5 March).rnThe JV is working on contract BC-16 between Udyog Bhavan and Green Park. The Robbins shields were built to an EPB design by Mitsubishi Heavy Industries (MHI) and arernundertaking half of the tunnelling required - the parallel tunnels between Jor Bagh in the middle of BC-16 and Udyog Bhavan at the contract boundary with BC-15.rnOn the other side of Jor Bagh, a pair of 6.54m diameter Herrenknecht shields (S-411, S-412) have been employed by the JV to drive twin tunnels. They were launched from INA box station.rnGeology along the alignment comprises sandy silt, silty sand and gravels with groundwater pressures generally up to 2 bar. Cover is approximately 15m.rnIn early 2007, the JV was awarded a 40-month contract by the client, Delhi Metro Rail Corp (DMRC), to design and build therntunnels, which total approximately 4km in length.rnThe first Robbins TBM was launched from Jor Bagh station in May last year and finished its first 1 km long drive with an intermediate breakthrough, at Race Course station, in late September. On that leg, the TBM built up to 19 rings per day - more than expected - and with 90% avaiiability, the JV commented, noting the contribution from electric motors in continuing the drives in mainly soft clays.
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