基于统一强度理论的非静水压圆形隧道塑性区半径的脆塑性摄动解

基于统一强度理论和弹-脆-塑性模型,综合考虑围岩强度的中间主应力效应和脆性软化,采用摄动法建立了非静水压圆形隧道塑性区半径的解析解,继而探讨所得解析解的适用范围,并与文献复变函数法、摄动法、数值模拟和总荷载不变法进行对比,最后分析各因素对隧道塑性区形状和大小的影响规律.研究结果表明:所建立的圆形隧道塑性区半径摄动解析解为反映中间主应力效应不同程度的系列解答,可退化为理想弹塑性模型解答且得到文献中4种方法的正确性和合理性验证,适用于塑性区完全包围隧道的情况,对应的隧道塑性区为双轴对称的类椭圆,具有广泛的理论意义和工程应用价值;摄动参数对隧道类椭圆形塑性区的大小和长/短轴变化都有明显影响;隧道塑性区范围随中间主应力效应、围岩峰后强度参数的增加均显著减小,说明不考虑中间主应力效应的Mohr-Coulomb强度准则解答偏保守,弹-脆-塑性模型相比理想弹塑性模型更适合隧道塑性分析.

对高速公路小净距隧道合理净距的探讨

使用数值分析手段,对不同净距未支护条件下小净距隧道的受力状况、变形、围岩塑性区进行了仔细的分析研究,可以了解到:当两隧道的净距小于B(B为毛洞开挖宽度)时,在两隧道中岩墙较大范围内将产生塑性区,且位移量明显大于单洞状态。中岩墙部位产生了明显的应力叠加现象,处于很不利的受力状态,中岩墙需进行特殊加固处理。而当净距提高到1B及以上的时候,塑性区的产生范围基本接近单洞状态,所以可以确定该高速公路隧道Ⅴ级围岩段的合理净距应该要大于或者等于1.0B。

Prediction of plastic zone size around circular tunnels in non-hydrostatic stress field

This paper discusses the calculation of plastic zone properties around circular tunnels to rock-masses that satisfy the Hoek–Brown failure criterion in non-hydrostatic condition,and reviews the calculation of plastic zone and displacement,and the basis of the convergence–confinement method in hydrostatic condition.A two-dimensional numerical simulation model was developed to gain understanding of the plastic zone shape.Plastic zone radius in any angles around the tunnel is analyzed and measured,using different values of overburden(four states)and stress ratio(nine states).Plastic zone radius equations were obtained from fitting curve to data which are dependent on the values of stress ratio,angle and plastic zone radius in hydrostatic condition.Finally validation of this equation indicate that results predict the real plastic zone radius appropriately.