Abstract: It is essential to choose a suitable breakthrough mode for the docking section between the shield and mined sections. The major procedures of breakthrough mode by shield and mining methods are presented to handle this issue, and the idea of shield dismantling before a breakthrough is proposed for the docking section constructed using mining technique. The shielddismantling process under the surrounding rocks of grades Ⅱ to Ⅴ and the breakthrough process using the mining method under the surrounding rocks of grades Ⅲ and Ⅳ are simulated considering the surrounding rock grade as a variable. By comparing the features of the two breakthrough modes and numerical calculation findings, conclusions are drawn as follows: (1) The shield dismantling before the breakthrough can efficiently enhance the turnover utilization rate of the shield, avoiding machine jam and minimizing the impact of blasting. (2) The numerical calculation results of shield dismantling in advance reveal that the development of the plastic zone and deformation in neighboring rocks of grades Ⅱ to Ⅳ are not clear, while that of grade Ⅴ increases rapidly, indicating that the shield dismantling in advance is feasible in surrounding rocks of grades Ⅱ to Ⅳ and not feasible in surrounding rock of grade Ⅴ. (3) The numerical results of tunnel breakthrough by mining technique in surrounding rocks of grades Ⅲ and Ⅳ indicate that the deformation rapidly increases at docking section in surrounding rock of grade Ⅳ; thus, appropriate reinforcement measures should be adopted. Finally, the breakthrough mode selection method for docking section between shield and mined sections considering surrounding rock grade are summarized and confirmed in practical engineering.

Key words: shield method, mining method, docking construction, breakthrough mode, surrounding rock grade, numerical calculation