300 m^(2)级5车道隧道九硐室施工力学特性数值计算

Numerical calculation of mechanical characteristics during construction of nine chambers in a 300 m^(2) class 5-lane tunnel

针对深圳侨城东路宝鹏大型地下互通式立交涉及的300 m^(2)级5车道超大断面隧道,开展施工技术方案及结构受力研究.首先,提出一套“分硐室开挖+衬砌加强支护”的超大断面隧道九硐室开挖施工技术.然后,结合隧道几何尺寸及支护方案,建立Midas三维有限元数值计算模型探究5车道超大断面隧道开挖施工动态力学响应特性.最后,提取隧道各分部结构应力云图,统计特征测点应力及位移监测曲线.研究结果表明:施工期间需采用超前小导管+管棚注浆措施对围岩进行预加固;现场需通过双侧壁导坑+双临时横撑构成九硐室开挖工法,并采用双层初期支护+加强加厚二次衬砌支护方案;现场开挖施工后结构应力与位移呈现快速增加趋势,而后隧掌子面不断前移各统计曲线逐步趋于平稳;围岩压力峰值可达2.01 MPa,拱顶位置超前小导管内力值最大为10 kN,两侧拱腰位置管棚内力最高为20 kN,拱腰及拱脚位置钢拱架内力最大为113 kN,拱肩位置锁脚锚杆内力在第66开挖施工步达到18 kN;初支结构测点应力峰值为2.4 MPa;初支拱顶、拱肩部位沉降峰值分别为12.4、6.8 mm;管棚、锁脚锚杆等结构联合支护效果明显.

This paper investigates the construction technology and structural stress of a 300 m^(2),5-lane super-large section tunnel involved in the Baopeng large underground interchange on Qiaocheng East Road in Shenzhen.Firstly,a construction technique for excavating nine chambers in a super-large sec⁃tion tunnel is proposed,involving sub-chamber excavation+reinforced lining support.Subsequently,utilizing tunnel geometry and support schemes,a three-dimensional finite element numerical calcula⁃tion model is established in Midas to explore the dynamic mechanical response characteristics of the ex⁃cavation construction for the 5-lane super-large section tunnel.Finally,stress cloud maps for each sub-section structure of the tunnel are extracted,and statistical analysis is conducted on the stress and dis⁃placement monitoring curves of characteristic measurement points.The research results indicate the need for advanced measures,such as small conduits and grouting within the pipe shed,to pre-reinforce the surrounding rock during the construction period.On site,a nine-chamber excavation method involv⁃ing double-sided wall guide pits and double temporary horizontal braces is required.Additionally,a sup⁃port scheme comprising double-layer initial support+reinforced thickened secondary lining support is ad⁃opted.After on-site excavation and construction,structural stress and displacement exhibit a rapid in⁃creasing trend,followed by the continuous forward movement of the tunnel face,eventually leading to the stabilization of the curves.The surrounding rock’s peak pressure can reach 2.01 MPa.At the arch crown position,the maximum internal force of the leading small conduit is 10 kN,the maximum internal force of the pipe shed at the two sides of the arch waist position is 20 kN,the maximum internal force of the steel arch frame at the arch waist and arch foot positions is 113 kN,and the internal force of the lock⁃ing anchor rod at the arch shoulder position reaches 18 kN in the 66th excavation construction step.The peak stress at the measuring point of the initial support structure is 2.4 MPa,and the settlement peak val⁃ues at the initial support arch crown and arch shoulder are 12.4 mm and 6.8 mm,respectively.The com⁃bined support effect of the pipe shed,locking anchor rod,and other structures is significant.