干湿交替条件下膨胀土隧道衬砌内力试验研究
Experimental study on the internal forces of expansive soil tunnel lining under the drying-wetting alternate condition

为开展衬砌受膨胀土胀缩特性影响的内力变化及变形特征的规律性研究,对膨胀土隧道模型实施了5个循环的干湿交替试验。研究结果表明:在衬砌弯曲应力值方面,其随循环次数的增加呈减小趋势,衬砌弯曲应力—时间关系曲线趋于平缓,说明衬砌受膨胀围岩胀缩效应的影响随循环次数的增加而逐渐减弱;在衬砌变形方面,受围岩吸水膨胀影响,衬砌被压扁,且拱腰处为最不利截面。而受失水收缩影响,衬砌发生弹性恢复变形但残留部分塑性变形;在循环时间方面,其随循环次数的增加而逐次减短,说明干湿循环作用能扩展土体中水分运动的孔隙网络,提高围岩的渗透能力。
In order to carry out the regularity study of the internal force variation and deformation characteristics of tunnel lining influenced by the expansive soil swell-shrink characteristics, the five-cycle wetting-drying tests of the expansive soil tunnel model were implemented. Several results and conclusions are gained as following: 1)In the aspect of lining bending stress value, the stress value showed a decrease trend with the increase of cycling times, and the lining bending stress-time relation curves become to flatten. It means that with the increase of cycling times the influence by swell-shrink effect of swelling wall rock to tunnel lining has gradually weakened. 2)In the aspect of lining deformation, affected by the expansion of surrounding rock, lining is squashed and the haunch is the critical section. While affected by the contraction of surrounding rock, the elasticity recovery deformation of lining has occurred but part of plastic deformation remained. 3)In the aspect of cycling time, the time gradually shortened with the increase of cycling times. It indicates that the wetting-drying cycles could enlarge the pore network for moisture movement in clay, and improve the penetration ability of the surrounding rock