2019-4_Pages_50-55

V.I. Golovanov, A.V. Рekhotikov, V.V. Pavlov, N.S. Novikov

FIRE TESTS OF TUNNEL LINING TUBINGS

Abstract. The main bearing and enclosing building structures of the combined lining of road tunnels and subway tunnels are reinforced concrete tubing. Taking into account the specific operation of underground structures reinforced concrete constructions have high humidity. Earlier studies have found that explosive (brittle) destruction of concrete occurs in structures made of heavy concrete with humidity more than 3.5 %. During exposure to high fire temperature in the tunnel after 10–15 minutes concrete can explode. Concrete pieces of 4–6 cm thick and  up to   50 cm² fly off to a distance of 10 m. The destruction occurs throughout the heated surface and leads both to the destruction of the protective layer of concrete and to decrease of the cross-section of the tubing. As a result, the structures prematurely reach the fire resistance for the loss of bearing capacity R.

Prevention of concrete explosive destruction of reinforced concrete lining of the tunnel is an important task to ensure a normalized fire resistance of tunnel structures.

All Russian Research Institute for Fire Protection conducted some fire tests for reinforced concrete tubing of standard sizes used in the construction of subway tunnels. Fire resistance assessment of the samples with concrete moisture content of 6 % was carried out under the unilateral influence of standard fire temperature on a specially manufactured stand at vertical and horizontal normative load. For comparison, there were studied tubes made of ordinary concrete and concrete with polypropylene fiber in the amount of 1 kg/m³ recommended by EN 1992-1-2:2004 as an additive to concrete reducing the risk of explosive destruction. According to the experimental study results it was found that on the heated surface of the ordinary concrete tubing under the influence of high temperatures there was an explosive destruction accompanied by loud claps with the destruction of the protective layer of concrete. In samples made of fiber reinforced concrete explosive destruction of concrete did not occur.

During the test it was established that the limit conditions of the structure on the loss of load-bearing and heat-insulating capacity did not come. The fire resistance of reinforced concrete tubing with the addition of polypropylene fiber according to GOST 30247.0–94 was not less than 125 minutes (REI 120).

In the practice of constructing long-distance road tunnels there is usually used structural fire protection in form of plate materials or fireproof plasters to ensure a standardized fire resistance and to prevent explosive destruction of concrete of tunnel lining. The use of reinforced concrete tubing made of fiber concrete with polypropylene fiber for enclosing structures of the tunnel will significantly reduce the cost of fire protection and shorten the period of construction.

Keywords: fire resistance of building structures, fire protection of underground structures, standard fire temperature mode, fire resistance limit, reinforced concrete tubing, polypropylene fiber

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Received  July 30, 2019

Authors:

Vladimir I. Golovanov – Doctor of Technical Sciences, Main Researcher. E-mail: pavelgol1@yandex.ru;

Andrey V. Pekhotikov – Candidate of Technical Sciences, Head of Department. E-mail: pekhotikov.a@mail.ru;

Vladimir V. Pavlov – Head of Sector. Е-mail: vv.pavlov@mail.ru;

Nikolay S. Novikov – Researcher. Е-mail: agps.nick182@gmail.com.

All-Russian Research Institute for Fire Protection (VNIIPO), Ministry of the Russian Federation for Civil Defense, Emergencies and Elimination of Consequences of Natural Disasters (EMERCOM of  Russia), Balashikha, Moscow region, Russia.