特大断面泥质软岩隧道浅埋段施工力学特征及工法适应性分析

Analysis of Construction Mechanical Characteristics and Construction Method Adaptability of Shallow Super-large Section Tunnel in Argillaceous Soft Rock

以龙泉山一号特大断面泥质软岩隧道浅埋段为工程背景,首先采用现场监控量测的方法对两个试验断面支护结构变形数据进行分析,再通过数值计算的方法与现场监测数据进行对比,验证了所采用计算参数的合理性,同时对双侧壁导坑法和CD法施工时隧道支护结构受力及变形特征展开深入研究,进一步分析CD法的适应性。研究结果表明:CD法拱顶沉降和断面水平收敛分别为37.8 mm和42.1 mm,较双侧壁导坑法分别增大5.6 mm和11.1 mm,但仍小于控制变形量;两工法支护结构拉应力均主要集中分布在仰拱,其中最大拉应力在仰拱左侧,隧道左拱腰和左拱肩压应力较大;CD法初期支护最大拉应力和最大压应力分别为2.33 MPa和10.74 MPa,较双侧壁分别增大1.87 MPa和3.21 MPa, CD法锚杆最大轴力达到64.5 kN,比双侧壁导坑法减小20.7 kN;两工法塑性区主要位于两侧拱肩及拱脚位置,CD法塑性区面积相较于双侧壁导坑法增大。根据二者工法对比,CD法能够满足施工安全要求,同时可为类似工程提供参考。

Taking the Longquanshan No.1 Tunnel with large section argillous soft rock as the engineering background, firstly, the deformation data of two test sections are analyzed by using the method of on-site monitoring and measurement, then through comparisons between the numerical calculation method and the field monitoring data, the rationality of the calculation parameters used in this paper is verified. At the same time, the stress and deformation characteristics of the tunnel support structure during the construction of double side drift method and CD method are deeply studied to further analyze the adaptability of CD method.The research results show that:(1) The vault settlement and section horizontal convergence of CD method are 37.8 mm and 42.1 mm respectively, which are 5.6 mm and 11.1 mm higher than that of double side drift method, but still less than the control deformation.(2) The tensile stress of the two construction methods support structure is mainly concentrated in the inverted arch, of which the maximum tensile stress is on the left side of the inverted arch, and the compressive stress of the left arch waist and left spandrel of the tunnel is large. The maximum tensile stress and maximum compressive stress of CD method primary support are 2.33 MPa and 10.74 MPa respectively, which are 1.87 MPa and 3.21 MPa higher than those of double side drift method respectively. The maximum axial force of anchor bolt by CD method is 64.5 kN, that is 20.7 kN less than that by double side drift method.(3) The plastic zone of the two working methods is mainly located at the spandrel and arch foot on both sides, and the plastic zone area of the CD method is larger than that of the double side drift method. According to the comparison of the two construction methods, CD method can meet the construction safety requirements and provide reference for similar projects.