ABSTRACT
As there is a contradiction between the stability of the surrounding rock and construction efficiency during the construction of the severe sandy dolomite tunnel, and the risk level of the surrounding rock area cannot be clearly classified, a theoretical analysis of the deformation of the tunnel's surrounding rock and the stress characteristics of the supporting structure is conducted using numerical methods. Combined with the basic concept of the yield approach index (YAI), the safety evaluation of the tunnel's surrounding rock is carried out, and the specific control measures of the surrounding rock deformation are proposed. The conclusions are as follows: the numerical results show that when the advanced small pipe and the surrounding rock grouting are used, the deformation decreases by about 33%, the range of the plastic zone decreases by about 50%, and the stress of the steel arch and bolts obviously reduces, compared with the case of no advanced surrounding rock control technology. Based on the YAI theory, the evaluation and calculation of the safety degree of the rock mass area in its state are realized. With the increase in the tunnel buried depth, the YAI of the surrounding rock in front of the tunnel face and side walls increases significantly. In order to ensure the stability of the tunnel's surrounding rock, the control measures, such as the advanced small pipe support and the composite grouting material reinforcement of the surrounding rock of the tunnel face, are applied. It is shown that the proposed measures have a good effect in field applications.
