Engineering and economic assessment of in-situ pressed linings
Engineering and economic expediency of in-situ pressed lining is determined by comparison with other types of lining, given that they are compatible, and the assessment includes all relevant factors. Technological progress in tunnel engineering has indicated that abandonment of in-situ linings in metro tunnelling has been temporary. Transport and hydraulic tunnels are generally constructed with in-situ linings cast in resettable forms, where concrete mix is delivered through pipes. Quality manufacture of precast elements for linings means plants making special equipment, as well as facilities for its storage, transportation and delivery to the face and erection. Major operations at construction of precast lining include: excavating of the face; erection; execution of flat invert; all kinds of groutings, caulking, extension of tracks, delivery of spoil to the shaft, and maintenance of mechanisms. The cost and labour input at construction of a tunnel lining are constant for a certain type and material used.