Abstract: To address the shortcomings of the current research and simulation accuracy of superlong pipe sheds, the structural stress characteristics and deformation patterns of "longitudinal and transverse support" system consisting of superlong pipe sheds and temporary inverted arches are investigated. This system is specifically employed in highspeed railway tunnels that cross operational railways in cohesive loess strata. First, a detailed modeling of the superlong pipe shed is conducted using solid elements to analyze the deformation of the strata and stress distribution in the pipe shed. Next, realtime monitoring of the longitudinal stress in the pipe shed is performed using grating optical fiber test technology to reveal the influence range of tunnel excavation on the longitudinal stress of the superlong pipe shed. Finally, the mechanism of the "longitudinal and transverse support" system is analyzed. The results are summarized as follows: (1) A wellintegrated superlong pipe shed transfers vertical stress over a large longitudinal range to reduce stress on the steel frame near the tunnel face. (2) The temporary arch forms a closedloop structure with the supporting structure after excavation, which enhances the overall loadbearing capacity of the steel frame and effectively controls the deformation of the loess tunnel. (3) The minimum distance between the pipe sheds in the longitudinal and transverse support system formed by pipe sheds and supporting structures should be greater than twice the closing distance between the tunnel face and the supporting structure. (4) The influence range of tunnel excavation on the longitudinal stress of the superlong pipe shed is between 30 m in front of the tunnel face and 20 m behind it. The strongly affected range is from 10 m in front of the tunnel face to 5 m behind it. Moreover, the longer the length of the pipe shed, the better its loadbearing effect.

Key words: shallowburied cohesive loess tunnel, superlong pipe shed, longitudinal and transverse support, numerical simulation, deformation control, grating optical fiber test technology