AJV of Impregilo, CMC and Construction Bureau 4 of the Hydropower Ministry is half way through approximately 90km of tunnels on Lots II and III on the South Main Line of the Shanxi Wan Jia Zhai Yellow River Diversion Scheme. The JV is battling climatic extremes and logistical challenges in a bid to alleviate severe water shortages in Shanxi Province, south eastern China.

Using four double shielded, hard rock TBMs, three from Robbins and one from NFM, the JV, which began excavation in December 1998, reports a daily best of 99m, a monthly best of 1822m and a four TBM cumulative monthly best of 4.9km. The production rates are the more impressive when taking into account that winter temperatures in the region, at 1500m elevation, fall to 30°C below zero, while other challenges include a road distance from contract start to finish of close to 160km.

Tunnelling on the $97m Lot II and $99m Lot III has been split into four sections (see diagram): T4 is 6.7km long, 4.9m in diameter and has been completed by TBM A; T5 is 25.6km long, 4.9m in diameter and is being driven by TBM A, which has finished 6.2km; T6 is 14km long, 4.8m in diameter, is being driven by TBM B and has currently completed 9.3km; T7 is 41km long, 4.9m in diameter and comprises two drives: TBM C from the north has finished 7.8km; TBM D from the south has reached 10.2km.

Construction is being carried out through Ordovician karstic limestone at T4, T5 and T6; in T6, wet, clay filled karstic cavities are encountered, slowing production. Roughly one third of T7 is in lime-stone, the remaining part in Carboniferous series, including sandstone with coal seams of variable thickness. Waterbearing fault zones are expected to pose special threats in the T7 excavation.

The tunnel lining comprises a single pass, honeycomb, four piece segmental lining, which permits a continuous excavation-erection cycle. Ring length is 1.4m, with i.d.s of 4.3m (T4, 5 and 7) and 4.2m (T6). Segments are produced in a centrally positioned precast factory with truck delivery to each portal.

The project is jointly financed by Shanxi Province and the World Bank and will initially service the province capital, Tai Yuan, easing water deficits in the urban, industrial and agricultural sectors.

Related Files
Lots II and III on the South Main Line of the Yellow River Diversion Scheme