###### Abstract  
The deformation characteristics of the surrounding rock in tunnel groups are considered critical for the design of support structures and the assurance of the long-term safety of deep-buried diversion tunnels. The deformation behavior of surrounding rock in tunnel groups was investigated to guide structural support design. Field tests and numerical simulations were performed to analyze the distribution of ground stress and the ground reaction curve under varying conditions, including rock type, tunnel spacing, and burial depth. A solid unit-structural unit coupled simulation approach was adopted to derive the two-liner support characteristic curve and to examine the propagation behavior of concrete cracks. The influences of surrounding rock strength, reinforcement ratio, and secondary lining thickness on the bearing capacity of the secondary lining were systematically evaluated. The following findings were obtained: (1) The tunnel group effect was found to be negligible when the spacing (\(D\)) was \(\geq\)65 m and the burial depth was 1600 m. (2) Both \(P_{0.3}\) and \(P_{\text{max}}\) of the secondary lining increased linearly with reinforcement ratio and thickness. (3) For surrounding rock of grade III (IV), 95% \(u_{\text{lim}}\) and 90% \(u_{\text{lim}}\) were found to be optimal support timings, with secondary lining forces remaining well below the cracking stress during construction. (4) For surrounding rock of grade V in tunnels with a burial depth of 200 m, 90% \(u_{\text{lim}}\) is recommended as the initial support timing. Support timings for tunnels with burial depths between 400 m and 800 m are 40 cm, 50 cm, and 60 cm, respectively. Design parameters should be adjusted based on grouting effects and monitoring data. Additional reinforcement is recommended for tunnels with burial depths between 1000 m and 2000 m to improve bearing capacity, with measures to enhance impermeability and reduce external water pressure. These findings contribute to the safe and reliable design of support structures for deep-buried diversion tunnels, providing technical support for design optimization and long-term operation. t +
Footnote †: journal: Applied sciences  
_Article_  
Study on the Deformation Characteristics of the Surrounding Rock and Concrete Support Parameter Design for Deep Tunnel Groups  
Zhiyun Deng  
1 Laboratory for Ecological Protection and High-Quality Development of the Upstream of Yellow River, Qinghai University, Xining 810016, China; [EMAIL_ADDRESS]  
2 School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China  
3 Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China; [EMAIL_ADDRESS] (J.Y. ); [EMAIL_ADDRESS] (H.H.) 4 Power China Chengndu Engineering Co., Ltd., Chengdu 610072, China; [EMAIL_ADDRESS] (Y.X. ); [EMAIL_ADDRESS] (Z.T.) 5 Technological Innovation Center of Hydropower, Wind, Solar and Energy Storage of Tibet Autonomous Region, Chengdu 610072, China  
6 Northwest Engineering Corporation Limited, Power China, Xi'an 710065, China; [EMAIL_ADDRESS]  
7 Huangen Tibet Yarting Zangho River Hydropower Development Investment Co., Ltd., Lhasa 850000, China; [EMAIL_ADDRESS]  
###### Abstract  
The deformation characteristics of the surrounding rock in tunnel groups are considered critical for the design of support structures and the assurance of the long-term safety of deep-buried diversion tunnels. The deformation behavior of surrounding rock in tunnel groups was investigated to guide structural support design. Field tests and numerical simulations were performed to analyze the distribution of ground stress and the ground reaction curve under varying conditions, including rock type, tunnel spacing, and burial depth. A solid unit-structural unit coupled simulation approach was adopted to derive the two-liner support characteristic curve and to examine the propagation behavior of concrete cracks.