Abstract: A new type of underground structure, underground bundled integrate tunnel(UBIT), which relies on transverse prestress, is proposed to reduce the impact of underground engineering construction on urban ground roads, pipelines, and buildings (structures) and improve the stress of underground passage structure. According to the engineering demands, a fullscale experimental study of the quarter structure is conducted to investigate the deformation response of the structure under design and overload conditions. The results reveal the following: (1) The development of structural deformation can be divided into elastic stress and nonlinear stages. (2) The weak point is located in the joint at the structure′s top quarter span, and the separation stress is 2.106 MPa. (3) The bundled integrate structure can bear twice the design load without separation, the structure stiffness is reduced by 60% after the joint separation, and the structure is not damaged and still has bearing capacity under four times the design load. (4) Under overload conditions, the relationship between the prestress strain increment and the vertical deflection of the structure is nearly linear proportional.

Key words:  bundled integrate structure, transverse prestress, fullscale test, mechanical properties