干湿交替条件下膨胀围岩隧道的力学性态研究

以广西南宁膨胀土为围岩材料,制作室内膨胀围岩隧道物理模型。通过对隧道模型进行干湿循环试验,得出围岩在吸水及失水条件下的围岩应力-时间关系曲线及衬砌应变-时间关系曲线。试验认为在吸水过程中大部分测点的围岩压力都经历了增长、减小、不同速率的再增长3个阶段。衬砌变形则经历缓慢增长、急剧增长、急剧减小、微增长4个阶段;在失水过程中,从整体上可以将围岩压力变化分为两部分,即围岩失水收缩致使衬砌和围岩的接触压力下降导致围岩应力值减小以及土体收缩产生收缩应力导致应力监测值增大。并分析这种变化规律的形成机理,证明时间效应和空间效应的存在。为今后膨胀围岩隧道的结构设计和施工优化提供一定的理论参考。

Research on Mechanical Behaviors of Swelling Wall Rock Tunnel under Dry-wet Alternate Conditions

With the expansive soil in Nanning,Guangxi area used as the material of surrounding rock,an indoor physic model of swelling wall rock tunnel is established. The relation curve of surrounding rock stress-time and that of tunnel lining strain-time are obtained by means of drying-wetting test of the tunnel model under the condition of surrounding rock water absorption and water loss.The test results indicate that the surrounding rock pressure at most measuring points experiences such three phases as increase,decrease and increase again in different rates in the process of water absorption,while the deformation of tunnel lining is subject to such four stages as slow growth,dramatic increase,dramatic decrease and slight growth. In the process of water loss,the changes of surrounding rock pressure,on the whole,can be divided into two categories: one is the decrease of surrounding rock stress caused by the decrease of contact pressure of the lining and the surrounding rock due to water loss and surrounding rock shrinkage,another is the increase of monitoring values caused by the shrinking stress due to shrinking forces. Further more,the mechanism of the changes is analyzed,demonstrating the existence of time effect and space effect and providing some theoretical references for structure design and construction optimization of such tunnels.