LA OROYA TUNNELS AND BRIDGES PROJECTDEFINITIVE STUDIES FOR CONSTRUCTION

Peruvian Ministry of Transportation and Communication, through its entity PERT (Transportation Rehabilitation Program), convoked to an International Public Contest for Studies Number 02-99-MTC/15.02.PRT-PERT.01, in order to select a consultant company to carry out the Definitive Studies for Tunnels and Bridges Construction in “Via de Evitamiento La Oroya” (La Oroya Bypass). As a result of the contest, the project was awarded to Consortium BERGER-GMI, by Contract Number 033-2001-MTC/15.02.PRT.PERT.

The road section is located in Yauli county, Junin department, at km 162+500 of “Carretera Central”, near Curipata Town, and has an approximate length of 14.6 km. It has been foreseen to build three (03) bridges, two (02) tunnels and two fly over, in which will be projected two additional bridges. The end of “Vía de Evitamiento La Oroya” is located near Shinca town, joining with km 4+800 of “La Oroya-Cerro de Pasco” road.

The Project objective is the elaboration of the Technical File, at a bid level, in order to execute the labors. This comprehend all designs for construction, and the elaboration of the budget needed to complete the following works:

WorkApproximate Location in “Vía de

Evitamiento”Approx. Length

(m)TunnelsMarcavalle Tunnel From km 10+860 to km 12+140 90Shinca Tunnel From km 13+225 to km 13+375 150

BridgesFly Over Nº 1 From km 0+080 to km 0+095 15Fly Over Nº 2 From km 0+280 to km 0+320 40Curipata Bridge From km 0+025 to km 0+115 90Tambo Bridge From km 4+330 to km 4+510 180Shinca Bridge From km 14+060 to km 14+190 130

Labors are located between the following coordenates:

South Latitude : 11°37’30” y 11°30’00”West Longitude : 76°00’00” y 75°26’00”

Average Altitude : 3900 mosl

According to TOR, Technical Proposal of Consultant, and the Contract, there are some basic investigations that are necessary to carry out. These are the following:

- Topography, for the definitive location for each tunnel or bridge.- Geology Studies in the influence area of the works.- Geophysic - Geognostic Investigations, which includes:

- 03 diamantine borings in Marcavalle Tunnel and 01 in Shinca Tunnel.

- Evaluation of quarries (canteras) and water sources.- Hydrology and Meteorology Studies.- Seismic Risk- Environmental Impact Studies- Essays of mechanical of soils and rocks.

When this basic studies have been finished, the first stage of the project would be completed.The second stage of the project, will be the design of each tunnel and bridge.

Bridges Design, includes basically:

- Definition of length, width, and exact location.- Definition of bridge structures (position and dimension of pillars and abutments,

protection structures, against erosion, undercut and sedimentation phenomenon).- Definition of construction material (concrete type)- Topographic, geologic, hydrological and construction Drawings

The bridge structures will be designed for a lifetime of 100 years.

Tunnel Design, includes basically:

- Definition of length, width and exact location.- Definition of internal systems (if it is necessary) such as: ventilation, lightning,

emergency systems, etc.

At this matter, we will indicate some considerations for the two tunnels that will be designed:

- The tunnel structures are designed for a lifetime of 80 years- The installed equipment are designed for a lifetime of 15 years- The installed monitoring and communication equipment are designed for a lifetime of

10 years- Employ a construction method by a sequential excavation method using shotcrete

initial (temporary) lining and plain concrete final lining (NATM), as proposed by the LBI-GMI Consortium for all Rock Classes along the tunnel section.

- Bi-directional roadway will be maintained in the tunnels. Two lanes tunnel. 80 m2 secction

- Type of Rock: Mainly fracturated limestone. Longitudinal slope: Maximun 4%. No water table was detected until now.

- Altitude of the tunnel location is over 3000 m- Traffic is of interurban tunnel character- Design traffic is considered as 1000 vehicles/day- Diesel engine equipped heavy vehicles’ ration in the traffic is 80%.- Internationally accepted criteria exist to make difference in the safety systems for

tunnels with the length limits <350m – 700m – 1070m – and longer. By this classification of the safety system the Mercavalle tunnel is considered as a long tunnel and the Shinca tunnel is considered as a short tunnel.

- Internationally accepted criteria exist to make difference in the illumination pattern for tunnels with the length limits <50m – 100m and longer. By this classification of the illumination pattern both the Mercavalle tunnel and the Shinca tunnel are considered as long tunnels.

- Internationally accepted criteria exist to make difference in the ventilation system for

tunnels with the length limits <400m – 2000m – 4000m – and longer.By this classification of the ventilation system the Mercavalle tunnel is considered as a short tunnel and the Shinca tunnel is considered as a very short tunnel.

Tunnel Marcavalle, is an interesting case, because it will be the longest road tunnel in Peru, with an approximate length of 1250 m. Some special considerations for its construction are mentioned below:

Ventilation:

Longitudinal ventilation is designed Ventilators push the air upward Axial-flow fans (jet-fans) are installed: 2 fans of 1,2 m in diameter symmetrically at each

100m, A pair of additional fans are designed at 50m from the upper tunnel end (exit of the

climbing lane) Minimum air velocity (due to natural + mechanical effects) 3 m/s (ventilation at fire) Minimum air velocity (due to natural + mechanical effects) 1 m/s (regular operation) Maximum air velocity 8 m/s (ventilation at fire, after people are rescued) Design computation have to verify that air speed is sufficient to keep the CO concentration

less than 200ppm, and soot less than 1,4 kg-m³ in the air Design computation have to verify fan diameter, select fan type and capacity

Illumination

Illumination levels refer to road surface luminance Daytime road surface luminance in the

access zone of the tunnel (50m of shadowing grate/louvre) = 20% of local daylight illumination

threshold zone (50m) = 1000cd/m² 1st transition zone (100m) = 400cd/m² 2nd transition zone (100m) = 100cd/m² tunnel interior (beyond the transition zone) = 60cd/m²

Night road surface luminance in the whole tunnel = 30cd/m²

Fire Fighting

Fire and smoke detectors are designed at a spacing of 25m in the tunnel centerline above the roadway.

Alarm posts (Alarm boxes) are designed on both sides of the tunnel with a spacing of 25m. A set of alarm push buttons with two alarm options Fire Accident, help needed

Fire fighting posts are designed on alternating sides of the tunnel with a spacing of 100m (the distance between two fire fighting posts on the same side is 200m) The posts are outfitted with

Dry fire extinguishers, 2 pieces at each post, 6 kg fill of each Hydrants connected to the water main with the standard diameter hoses in rolls,

50m long hose on each roll Alarm boxes with the set of alarm push buttons as given above

The door of the fire fighting and alarm posts and both stands of the dry fire extinguishers have sensors. If the door is opened the control center gets an alarm. If the dry fire

extinguisher is removed, the control center gets alarmed and a yellow flashing light at the post is operated.