Aiming at open problems in the design and construction of double span arch-connecting tunnel

a research on three-dimensional stress characteristics of two types midboard is carried out by means of finite difference method FLAC3D2.0; and their merits and demerits

as well as applicable conditions are analyzed. The result shows that stress of separated type curved wall is more proper than integral type stalk on shallow depth double span arch-connecting tunnel in the condition of II type rock; inner force of midboard has been in stabilization when left cavern heading face drives to three times diameter from researched cross-section; while right and left cavern heading face drives to (–1–1)D time diameter from reseached cross-section

inner force of midboard greatly changes

and these constructions are key processes.