Konstruktor - Trag u vremenu i prostoru

BASIC INFORMATION:

Employer:

Location:

Installed Power:

Design:

Construction Period:

BRIEF DESCRIPTION OF THE WORKS:

1. Hydrotechnical – headrace tunnel 1,574m long plus 150m of access tunnels in the shape of a horseshoe. The tunnel is 4.20m high; the arch radius is 2.10m and the bottom width 3m. The cross-sectional area of the tunnel is 14.80m². The tunnel will be provided with a 30cm thick
   reinforced concrete lining. After casting the lining for the tunnel, its clear span will be 3.60m.
2. Intake structure (with a sedimentation tank) approx. 20m high to be provided with plate gates and grilles for cleaning.
3. The surge shaft and the valve chamber at the end of the tunnel 42m high and inside dimensions of 8x5.40m.
4. Outdoor machine house 22.50x15m.

Statistics: open excavation accounted for 60,000m³, tunnel excavation for 27,000m³, concreting for 20,000m³, reinforcing 600t and 1,700m³ shotcrete.
Site organization and technology were as follows:
1. Excavation for the headrace tunnel was carried out according to the traditional scheme by drilling and blasting with the assistance of a jumbo-drilling machine equipped with two booms and the use of explosives activated by non-electric nonel type detonators. Loading and transport of excavated material were carried out by a loader (2.5m³) and dump trucks.

The tunnel is ventilated. It is lined in situ with concrete placed behind steel shutters in 10m lengths and traveled forward in a retracted mode. The tunnel is lined with reinforced concrete 30cm thick. The works were carried out in three (3) shifts.
2. The works for the intake structure included blasting. Concrete was placed behind shutters with
the assistance of a truck-mounted concrete pump.
3. Excavation for the surge shaft/valve chamber involved open cut with the use of explosives and the assistance of excavators equipped with hammers. Concrete was placed behind special shutters with the assistance of a tower crane.
4. The outdoor machine house was built as a typical high-rise structure by the application of a conventional method of construction.

The works entailed specific difficulties which were predicted and the effects of which were eliminated or reduced to a minimum. This referred to the following: a small tunnel profile requiring use of special equipment and continuous time control due to the overlapping of separate phases of the
work. Also, the nature of the terrain which is composed of karst and cavernous rock; the works to be carried out below the level of the river involved the risk of water entering the tunnel. Problems also arose in blasting for the tunnel and the outdoor structures due to close proximity of the existing
hydro-technical tunnel. This tunnel, which was not made of concrete, was in a very bad condition.