Water Arrives in KunmingAfter nearly five years struggling with extremely difficult geological conditions, the official inauguration ceremony of the Zhangjiuhe River Water Diversion and Water Supply Project (KWSP) took place on Sunday 25th March, 2007 at the water treatment plant in Kunming.Kunming is the political and economical centre of the Yunnan Province and one of the most beautiful historical and cultural cities of China. The city is one of the 14 cities in China that are severely short of water. Apart from the difficulties encountered during construction, the project was under pressure to supply water to the city since last year’s rain season did not provide sufficient downfall for the existing water supply and a water shortage was to be expected if the project could not be opened before March 2007. Project backgroundKunming and Zürich, where Pöyry Infra is based, have been maintaining a twinning relationship for more than 20 years and Pöyry Infra has successfully cooperated with Kunming since 1988 in several projects, such as a wastewater drainage master plan, an urban city master plan and the Zhangjiuhe River Water Supply and Diversion Project.Since 2001, Pöyry Infra (former Electrowatt Infra) has been involved in the project, which is located in the southwest of China. This project consists of a dam in the north of Kunming to collect water from the Zhangjiuhe River in the Yunlong basin and the 98 km water pipe line conveying the water to the treatment plant close to Kunming. Visit www.poyry.comPöyry Infra is carrying out the construction supervision and design review for civil works Lot 1 together with his local subcontracting consultant GHIDRI (Guiyang Hydroelectric Investigation Design and Research Institute) of the State Power Corporation of China. The USD35 million contract for civil works Lot 1 has been awarded to the Italian contractor CMC of Ravenna. The civil works Lot 1 consists of the headwork complex with powerhouse, the pre-chlorination building, the access to the Kangle tunnel, the 7,797 m Kangle tunnel and the 13,733 m Shanggongshan tunnel. The total investment foreseen for the project is about USD476 million. This water supply project is one of the largest in China and has a capacity of 0.6 million tonnes of water per day. Visit www.cmc.coopGeologyThe geology along the alignment includes limestone, karstic limestone and sandstone with some expected fault zones. They are present in two main lithologies, one with schist rock and the second with dolomitic rock. The schist rock is made up of pelitic and arenaceous schists with fine and very fine beds with variable quantities of clays, ranging from fractured to very fractured. The dolomitic unit is made up of compact, fractured to highly fractured dolomites and calcareous dolomites. Test of bypass gate valve during water trial run on 8th March, 2007 The overburden of the tunnels is variable: the maximum cover is at 350 m corresponding to the highest peaks and the minimum cover is 20 to 25 metres and corresponds to the crossing of the most deeply cut valley. The major cover can be found in the area dominated by the schists, having an average depth of around 150-200 metres, whereas in the dolomite area the average overburden measures about 100 metres.The water table lies between 0 m to max. 200 m above the tunnel alignment, only the Shanggongshan inlet and outlet are for relatively short stretches above the water table. Excavation methodsThe contract stipulated that both tunnels would be driven with a double shield hard rock TBM. A Robbins TBM equipped with a 3,655 mm-diameter cutter head dressed with 25 432 mm-diameter disc cutters was used. Other TBM specs were as follows: cutter head maximum recommended thrust of 6,250 kN, cutter head drive by two speed electric motors with clutches, and backup length of 350 metres. The installation of the TBM was completed by mid April 2003, and excavation started two months ahead of schedule. Visit www.therobbinscompany.com Opening ceremony at the water treatment plant on 25th March, 2007 During excavation, the rock found was heavily fractured dolomite, sometimes argillaceous, and sandy granular fault material. Caves in material were described as sandy, gravely material or soup. Due to these unforeseeable geological conditions, the progress rates of the TBM in the Shanggongshan tunnel were much slower and caused more problems than expected. These unexpected difficulties and obstacles were encountered in the poor geological conditions of the contact zone between the schists and dolomites and several fault zones intersecting the Shanggongshan tunnel obliquely. In this area, the rock mass properties are characterised by low cohesive strength with high permeability.The owner, Kunming Zhangjiuhe River Water Diversion and Water Supply Project Administration Bureau (KWSP) - after consultation with the contractor and the engineer - first decided to change the excavation method of the Kangle tunnel from TBM to conventional drill-and-blast method, which included five heading faces and the construction of the required intermediate adits for access to the headings.The TBM was stopped several times due to sudden collapses of the tunnel face, partly filling the cutter head and the telescopic shield, and blocking the TBM. Excavation of a bypass bore was necessary to free the TBM. Even sudden collapses filling parts of the bypass gallery and smaller instabilities occurred.In order not to delay the completion date of the project and to speed up the construction progress, a second decision was made in the sequence of events, which consisted in adopting the drill-and-blast method instead of TBM to bore 3.9 kilometres of the Shanggongshan tunnel from the outlet side (from Ch. 10+000 to Ch. 13+932). A first adit was bored at Ch. 11+237 so that three additional working faces for drill-and-blast excavation could be started.But on 9th June, 2005 the TBM was again stopped at Ch. 7+568 by running sand with high underground water pressure. After Pöyry’s geological expert Dieter Fellner, the contractor’s geologist and other local geological experts had visited the site and had been consulted, the owner decided a third change on 3rd September, 2005: the TBM method should be abandoned. The remaining downstream section of the Shanggongshan tunnel, from Ch. 7+568 to Ch. 10+000, had to be excavated using drilling and blasting and the TBM had to be removed. The excavated length of the Shanggongshan tunnel when the TBM was taken out was 7,556.5 metres of a planned total of 21.5 kilometres of TBM excavation. View pictures here.To reach the completion target, three additional adits had to be bored to divide the tunnel in short sections. A total of seven heading faces were in progress and excavation from the Shanggongshan inlet was also continued with conventional tunnelling after the TBM and its backup was removed, only leaving the TBM carcass in place. Consolidation grouting both from the surface and inside the tunnel had to be implemented to cope with the geological conditions.The blasted cross-section ranges from 11.92 to 14.28 square metres depending on the rock class. The internal area is 7.06 square metres. The drill and blast was carried out by local subcontractors with pneumatic hand drills and other local materials and equipment (locos, excavator loaders and muck shuttle cars).Support and liningThe TBM-built tunnel is lined with precast concrete segments with an internal diameter of three metres backfilled with fine gravels and grouted. One segmental ring consists of five elements including the keystone. The thickness is 25 cm and the width is 1.10 m. Two types of segments were installed according to the encountered rock class, either light segments reinforced with steel bars (124.76 kg/cu m) or heavy segments (153.83 kg/cu m).Drilling and blasting changed the originally foreseen segmental lining by in-situ reinforced concrete lining. The temporary support consists of shotcrete reinforced with wire mesh, anchors and steel ribs, depending on the encountered rock class.Ventilation and muck haulageDue to the length of the tunnels and the small internal diameter of three metres, the ventilation design was a real challenge. Application of standard calculation methods was not possible so that calculations had to be based on the Swiss Standard SIA 196. Along the tunnel, a series of booster fans were installed.A mucking system by rail was used behind the TBM, with 24 kg/m rails installed with a spacing of 820 mm. The muck train consisted of a 15 t diesel locomotive, six segment cars (for two segment rings), one fine gravel car, one cement car, nine muck cars to carry the material excavated by two TBM strokes and one man rider for personnel transport. For emergency and safety purposes, a rescue car was based in the area of the California switch in the 300 m-long backup. The blasted rock was transported by means of electric locomotives and Decauville shuttle cars. An electric driven track-mounted rock loader was employed in the drill and blast tunnels to load the rock onto the mining cars and transport it to the disposal area.Contract managementDue to the unforeseen geological conditions, the owner had to grant a contract extension to CMC until end March 2007. In spite of the great difficulties met during tunnelling and thanks to the efforts and quick decisions by all involved parties, it was possible to meet the deadline set by the Kunming municipal government to finish the civil works before the end of March, including the water trial run which was not included in the contract programme. The water trial run was successfully conducted between 8th and 23rd March, 2007 and all parties, including the people of Kunming, were happy to celebrate the arrival of water on 25th March. Pöyry Infra has taken care of the negotiations, the contractual consequences and claims management due to the change of the excavation method. They are now in the closing stage of the project, taking care of acceptance, as-built plans, final accounts and supporting the owner with the handover of the project to the operation unit. Click cn/48. 16/07.