Improving the town protection by diverting flood flows

Project name
Lužická Nisa, Jablonec nad Nisou, Improving the town protection by diverting flood flows across Mšeno dam reservoir – civils part

Project owner
Povodí Labe, státní podnik

Contractor
Consortium of Metrostav + SYNER – VD Mšeno

Designer
Valbek, spol. s r.o.

Contractor for geotechnical monitoring
ARCADIS Geotechnika a.s.

Construction period
11/2011 – 06/2013

Technical description

Basic data : flood prevention measures in the town of Jablonec nad Nisou link to the construction of structures ensuring the regulation of flows in the Lužicá Nisa and Bílá Nisa Rivers dated 1902 – 1910. The central piece of the entire solution is Mšeno dam reservoir built on the Mšeno Brook, to which flood flows are diverted through two derivation tunnels.
The current development project solves the increase in the capacity of the intake tunnels, the construction of new distribution structures and construction of a new outlet tunnel from Mšeno dam, including the construction of intake and outlet structures. The entire project is supplemented with associated building structures and operating systems.
Significant from civil engineering viewpoint are structures SO 02 Intake Tunnel (591.5 m, 11-14 m2, 0.5%), SO 04 Intake Structure (33 m, 16-34 m2, 100%-2%) and SO 05 New outlet Tunnel (1253.54 m, 12-16 m2, gradient 2%).
Geotechnical conditions : the area of operations is formed by Krkonoše-Jizerské Mountains pluton, mainly consisting of granites and granodiorites. The excavation of all underground structures passes through biotitic granite, which is characterised by various degrees of weathering in this locality; Unweathered rock blocks alternate with heavily weathered mass, which turns after disintegration into coarsely grained material, the so-called perk.
Technical project solution: see the project layout


Construction technology (tunnel excavation, primary lining, secondary lining) : The tunnels are driven from portal areas using the NRTM with canopy tube pre-support. Two hoisting shafts are used for the access to the linear working. Four excavation support classes (2-5) are designed for the excavation. The basic supporting element is SB C 20/25-X0 shotcrete with steel mesh, rock bolts and SN-type steel spiles. The 400 mm thick final lining is in C30/37-XC2 reinforced concrete.
Construction progress: Maximum concurrence of works on partial structures is necessary with respect to the owner’s requirement for the works to be completed by 30.6.2013 (see the Master Schedule). As of the end of January 2013, structures SO 01 and SO 03 and the excavation of SO 02 have been finished. On SO 05, 1052 m of the total 1258 m length of the excavation have been completed. The construction of the final lining of the intake tunnel from Paseky SO 02 and the construction of the intake structure near the shipyard SO 04 is underway. The works were completed at the end of 2013.
SO 02 tunnel excavation

SO 03 Bílá Nisa River channel treatment

SO 04 tunnel excavation

SO 04 Intake structure – placement of reinforcement and concrete casting of the substructure

SO 05 excavation face