超大断面隧道侧向扩挖施工围岩力学特征研究

通过等代圆法将侧向扩挖隧道断面简化为双连通域问题,结合复变函数理论Schwarz交替法推导出了侧向扩挖隧道复应力函数的具体形式,并以深圳横龙山隧道超大异形断面(跨度29.171m,高跨比0.45)侧向扩挖工程为例,通过数值计算对单次扩挖宽度、围岩应力和位移特征展开研究。结果表明:单次扩挖宽度为4m时最为适宜,三次分步扩挖产生的二、三、四次应力状态均有不同程度的变化,最大应力和位移值出现于双洞近接施工段且主洞三次扩挖产生的平均拉、压应力值均大于扩挖洞,拱顶应力限差控制在4%以内,计算结果具有较高的精度。

Mechanical deformation characteristics of rock mass surrounding lateral enlarging excavation of tunnels with ultra-large sections

The lateral enlarging excavation section is simplified to double connected domains by use of the method of equivalent circle. Combined with the theory of complex function, the specific equation of complex stress function for deformed ultra-large section (span 29.171 m and depth-span ratio 0.45) is deduced by Schwarz’s alternating method during lateral enlarging excavation. Taking the Henglongshan tunnel in Shenzhen of China as an example, the stress and displacement characteristics of surrounding rock mass are analyzed by numerical calculation. It is shown that the width of 4 m is preferable for each enlarging excavation, and during three steps of enlarging, the stress states of rock after second, third, and fourth excavation are different. The maximum value of stress and displacement is presented in the approaching region of double holes, and the average stresses of tension and compression around the main hole are larger than those around the enlarging holes. The allowable difference of stress at top of arch is controlled within 4%, and the computed results are precise.