考虑膨胀应力和剪胀的深埋隧道弹塑性解

基于湿度应力场理论，推导了考虑膨胀应力和剪胀特性的圆形隧道开挖后围岩力学响应的弹塑性解。将隧道软弱围岩遇水膨胀现象视为湿度-应力耦合过程，基于Fick第二定律，推导了圆形隧洞围岩内湿度扩散非稳态解。采用非关联流动法则，获得了隧道高膨胀势区的应力和位移解答。以两种不同质量岩体开挖的隧洞为例，分析了膨胀围岩应力和变形的影响因素。结果表明，考虑膨胀应力（取决于围岩含水率变化和湿度膨胀系数）时，塑性区扩大，松动圈厚度增加，应力收敛变慢。当膨胀应力增大到一定程度时，塑性区将出现拉应力区。膨胀岩隧洞开挖遇水作用，膨胀应力增加的围岩变形远大于地应力引起的围岩变形。同时，应力剪胀对膨胀性围岩的变形影响不容忽视，尤其是在支护抗力较小的情况下，洞壁处径向位移增加显著。

Elastoplastic solution for a deep-buried tunnel considering swelling stress and dilatancy

This study focuses on tunneling under challenging conditions, particularly with regard to the stress distribution and deformation in the humidity stress field. The swelling phenomenon during tunneling has been treated as a coupled humidity–mechanics process, where the humidity diffusion and stress dilatancy are considered together to obtain stress and deformation fields for tunnels crossing the formations with high swelling potential. A solution to the nonstationary process of humidity transfer has been derived according to Fick’s second law. The swelling pressure has been included in the form of body force, and a non-associated flow rule has been adopted to obtain the analytical solutions. Next, considering the examples of rock tunnels that are excavated in two different quality rock mass, we have investigated the impact factors on stress and deformation in swelling surrounding rock. Numerical results show that the inclusion of the swelling stress increases the plastic zone of the surrounding rock and the maximum stress at the elastic-plastic boundary, whereas the stress convergence has been decreased. After a certain increase in swelling pressure, a tensile stress zone appears in the plastic circle. The deformation of surrounding rock caused by swelling pressure can be much more significant than that caused by in-situ stress. Furthermore, the effect of dilatancy on the deformation rock cannot be negligible especially when the support resistance is small. This paper presents a new possible workflow to quickly evaluate the elastic-plastic stress and deformation of tunnels in swelling surrounding rock.