On the Tunnel Support Mechanism of Shotcrete

从隧道支护稳定性的角度研究了喷浆与地面相互作用的力学效应。衬砌模型采用一组通过弯曲弹簧连接的刚性杆件，地基假定地基反力系数为常系数。通过改变喷筑宽度、侧向土压力系数、覆盖层厚度和隧道断面形状，进行了大量的参数数值分析。结果表明，路基反力对隧道的稳定性是至关重要的，如果路基反作用力足够大，即使是薄喷混凝土衬砌也可以支撑周围的地面。其他结论如下：1)坡面反力通过控制隧道周围的变形来减小喷浆衬砌的弯矩。2)薄壁喷浆衬砌可能会产生大量的弯矩。3)薄壁喷浆衬砌是首选的，除非发生屈曲。4)即使喷浆衬砌发生弯曲破坏，如果希望有足够的地面反力，也不会造成严重的破坏。由于本研究是通过非常简单的力学模型进行的，因此需要对隧道的稳定性进行进一步的研究。

The mechanical effect of the interaction between the shotcreting and the ground is studied from a view point of the tunnel support stability. A serial set of rigid bars jointed through the bending springs are adopted for a model of the lining while the constant coefficient of subgrade reaction is assumed for the ground. A lot of parametric numerical analyses are done by changing the width of shotcreting, the coefficient of the lateral earth pressure, the overburden and the shape of tunnel section. It is shown that the subgrade reaction is essential for the tunnel stability and that even a thin shotcrete lining supports the surrounding ground if an adequate amount of the subgrade reaction is expected. Other conclusions are as follows.1) The sugrade reaction reduces the bending moment of the shotcrete lining by controlling the deformation around the tunnel.2) The thin shotcrete lining may cause a large amount of bending moment.3) The thin shotcrete lining is preferred unless the buckling occurs.4) Even when bending failure occurs in the shotcrete lining, no serious damage is resulted if a sufficient ground reaction is expected.A further research is required concerning the tunnel stability since the present study was done through a very simple mechanical model.