为验证总安全系数法中喷层的荷载结构模型及其安全系数计算方法，研制大型隧道结构模型试验系统，采取结构试验的方法，开展毛洞、不同厚度喷层以及二次衬砌的加载破坏试验。通过围岩和细砂材料的三轴试验明确模型试验中各材料的物理与力学参数，模拟毛洞、不同厚度喷层以及二次衬砌的加载破坏全过程，依据破坏状态明确喷层与二次衬砌的设计承载能力，试验中监测围岩应力应变、喷层内外侧应变和喷层位移，结合监测结果分析喷层与二次衬砌在承载过程中的变形特征与受力特征，明晰喷层与二次衬砌的承载机制，并与总安全系数法理论计算结果进行对比分析。结果表明： 1）在试验断面条件下喷层受力状态为小偏心受压，喷层与围岩之间的粘结能有效传递剪力，从而减少了喷层的弯矩，有利于充分发挥喷层的抗压强度，同厚度情况下喷层的设计承载力要高于二次衬砌； 2）试验得到的厚度为2 cm和4 cm喷层的设计承载力比总安全系数法理论计算结果分别大27.0%和22.9%，表明总安全系数法的喷层承载力计算模型是合理的，并具有合适的安全性。
Herein, a largescale tunnel structural model
experimental system is established. First, loaded damage tests are conducted on
tunnels without support, supported by shotcrete of various thicknesses, and supported
by secondary lining through structural tests to validate the feasibility of the
load structure model of the shotcrete layer using the total safety factor
method and its calculation method. The physicomechanical
parameters of each material in the model test are then clarified through
triaxial tests of the surrounding rocks and fine sand materials. The entire
loaded damage process of the tunnels without support, supported by shotcrete of
various thicknesses, and supported by secondary lining, is simulated. The
designed bearing capacity of the shotcrete and secondary linings is determined
according to tunnel failure states. The stress and strain of the surrounding
rocks, internal and external strain of the shotcrete layers, and displacement
of the shotcrete layers are monitored. Finally, the deformation and stress
characteristics of shotcrete and secondary linings are analyzed for determining
the bearing capacity of these materials. Comparing the results with the
calculated results using the total safety factor method shows the following:
(1) The stress of the shotcrete layer exhibits a small eccentric compressive
stress. The cohesion between the shotcrete lining and surrounding rock mass can
transfer the shearing force in the rock mass, reducing the bending moment and
greatly improving the compressive strength of the shotcrete lining. The
designed bearing capacity of the shotcrete lining is higher than that of the
secondary lining under the same thickness. (2) The designed bearing capacities
of the shotcrete lining with thicknesses of 2 and 4 cm are 27.0% and 22.9% higher, respectively, than the
theoretical calculation results by the total safety factor method, indicating
the rationality of the calculation model of the bearing capacity of the
shotcrete lining by the total safety factor method.
