关于矩形明(棚)洞土压力荷载模式的探讨

Discussion on Earth Pressure Mode of Rectangular Shed Tunnel

由于现有规范中明(棚)洞荷载不能完全体现回填土石与结构的相互作用,为确保结构设计安全,从现有规范中荷载规定出发,采用力学分析和理论推导,分析回填土石明(棚)洞结构的荷载模式,推导荷载计算公式,并采用数值分析和工程案例进行验证。研究表明:目前规范中棚洞荷载均忽略了结构侧上方回填土体对结构顶板产生的荷载作用,该部分土体作用以附加水平力和附加竖向力的形式传递至结构顶板,呈三角形分布形式,可通过库仑土压力理论的演化公式进行计算。附加荷载对结构产生不利影响,随着回填坡度的增加,对结构的影响越明显,尤其是对外侧墙的剪力影响尤为突出。工程案例对比研究表明,考虑附加荷载时理论计算可反映出外侧墙发生剪切破坏,与现场实际破坏模式相同,表明考虑附加荷载的荷载模式与工程实际相符。在明(棚)洞结构设计中,需考虑附加荷载作用的影响,否则可能导致结构处于不利状态。

The load mode in the existing specifications does not fully reflect the interaction between backfill soil and structure.Mechanical analysis and theoretical derivation methods are employed to analyze the load mode of shed tunnel with soil backfill,and the load calculation formulas are derived to ensure the safety of the structural design.Numerical analysis and engineering cases are used to verify the results.Research results reveal the following:(1)The load of the backfill upper side of the structure,which transmits to the structure′s top plate in the form of additional horizontal and vertical forces with a triangular distribution,is ignored in the existing specifications.It can be calculated using the evolution formula of Coulomb earth pressure theory.(2)This additional load adversely impacts the structure,which worsens with increased backfill slope,especially on the shear force of the outer sidewall.(3)The case study results show that when considering additional load,the theoretical failure mechanism agrees with the actual failure mechanism.Thus,the influence of additional load must be considered in the structural design of the shed tunnel.