Abstract: The influencing factors and their influencing degree of economy of large crosssectional mechanized construction of soft rock railway tunnel are of great significance. As a result, the construction quantities of two mechanized construction design drawings, i.e. the large crosssectional mechanized construction and conventional mechanized construction(bench method) of soft rock tunnel of ZhengzhouWanzhou Highspeed Railway, are introduced, and three sets of budgeting schemes are established from aspects of quantity optimization and technology variation based on existing railway cost standard and partial unit price analysis on large crosssectional mechanized construction of soft surrounding rock. The research results show that: (1) The advance reinforcement is the main economic affecting factor of large crosssectional mechanized construction. (2) Compared with the conventional mechanized construction method, the budgeting index per meter of large crosssectional mechanized construction in Grade Ⅳa, Ⅳb and Ⅴa surrounding rocks increases by -9.41%, 10.81% and 6.24% respectively; and the monthly advance of large crosssectional mechanized construction in Grade Ⅳ and Ⅴ surrounding rocks increases by 9.33% and 22.22% respectively, which shows obvious economy.

Key words: railway tunnel, soft surrounding rock, large crosssection, mechanized construction, economy, construction quantity, construction method