Mechanization of finishing of pneumatic-concrete tunnel linings, ensuring lower roughness

Abstract

For tunnels constructed in rock wide use should be made of progressive types of linings in which the bearing capacity of rock of medium and high strength is utilized to the maximum possible extent.Such linings include, in particular, a new type made of a cavitationand wear-resistant material --pneumatic concrete with a geometrically accurate and smooth surface. The formless technology for construction of such linings makes it possible to obtain high-quality permanent linings of practically any small thickness (5-20 cm). This type of lining may have a minimal thickness, it is characterized by absence of contact grouting, and it has high density, strength, and imperviousness, as well as better conditions for joint operation with the rock.The use of permanent penumatic-concrete linings is possible in tunnels driven by the shield and combined methods, as well as by the drilling --blasting method with smooth breaking of the outline; and in combined linings, when pneumatic-concrete or reinforced Gunite shells are constructed on primary linings made of prefabricated, cast-ln-place, and cast-inplace --pressed concrete. However, the basic condition for applicability of such linings in hydraulic tunnels is the solution of the problem of building them with regular geometric shapes and a smooth surface characterized by a roughness coefficient of 0.011-0.012.