Abstract: The constant resistance yielding support is the ideal form of support for squeezing tunnel. Current technology is difficult to satisfy the safety requirements of high bearing capacity, large deformation and load stability at the same time. In response to this problem, the conversion constant resistance yielding device (CCYD) was developed inspired by the metal drawing process in combination with the characteristics of steel arch support. In this paper, the working principle of the CCYD was discussed, and its mechanical response law and characteristics were analyzed. Through the indoor test and numerical simulation, the influence of the design parameters was analyzed, and the performance measurement index of the conversion constant resistance yielding device was determined. The analysis shows that: 1) The conversion constant resistance yielding device can constantly resist deformation under pressure; when installed in the steel arch joint allowing it to be part of the steel arch, the device can ensure the stability of the arch, improve its large deformation adaptability while providing constant support for the surrounding rock. 2) Based on the four design parameters: the cone angle, the friction coefficient, the cross-section shrinkage rate and the diameter of the pressure bar, the device can realize pressure resistance and pressure control with satisfactory load stability, which can provide important technical support for soft-rock tunnel large deformation and the stability control of support.

Key words: yielding support, squeezing large deformation, constant resistance yielding device, numerical simulation