(1. National Field Observation and Research Station of Landslides in Three Gorges Reservoir Area of Yangtze River，China Three Gorges University，Yichang，Hubei 443002，China；2. College of Civil Engineering and Architecture，China Three Gorges University，Yichang，Hubei 443002，China；3. China Construction Fifth Engineering Division Corp.，Ltd.，Changsha，Hunan 410000，China；4. Faculty of Engineering，China University of Geosciences，Wuhan，Hubei 430074，China)
Abstract：The phenomenon of supporting structure cracking due to the expansive soft rock is common in tunnel engineering. Taking the non-uniform stress of tunnel surrounding rock structure caused by expansive soft rock as the starting point，the stress characteristics of the supporting structure of expansive soft rock tunnels are studied，and a swelling force release method of expansive soft rock tunnel supporting structure is established. The granular bentonite is implanted between the primary support and the secondary lining as the buffer layer，and the model test is carried out. The three-dimensional numerical model is established by MIDAS GTS NX software，and the mechanical characteristics of the expansive soft rock tunnel support structure before and after the buffer layer are comparatively analyzed. According to the tunnel mechanics theory，the swelling force slow-release model of the expansive soft rock tunnel supporting structure is established，and the expression of release coefficient is obtained. The practicability of the slow-release method is verified. The results show that the deformation of the supporting structure and the swelling force of the surrounding rock after adding the buffer layer are significantly smaller than those before adding the buffer layer. The deformation characteristics are characterized by the sinking of the vault，the characteristics of arch bottom upward uplift and the arch waist inward convergence. The buffer layer reduces the swelling force of surrounding rock acting on the supporting structure by resisting，weakening and transferring. Consequently the single concentrated force system is transformed into the uniform load system. The slow-release coefficient calculated by the slow-release model is 30%–50%，indicating that the implantation of granular bentonite as a buffer layer between the initial support and the secondary lining can slow down the swelling force. This research can provide a reference for solving the swelling problem of soft rock tunnels.
[1] 孟陆波，潘皇宋，李天斌，等. 鹧鸪山隧道二次衬砌开裂机制及支护时机探讨[J]. 现代隧道技术，2017，54(2)：129–136.(MENG Lubo，PAN Huangsong，LI Tianbin，et al. Cracking mechanism and supporting time of secondary lining of Zhegushan Tunnel[J]. Modern Tunnelling Technology，2017，54(2)：129–136.(in Chinese))
[2] 耿 琳，金 龑，吴传赛，等. 季节冻土区吉图珲高铁东兴膨胀岩隧道保温防冻方法及分析[J]. 自然灾害学报，2019，28(3)：17–26.(GENG Lin，WU Yan，WU Chuansai，et al. Thermal insulation and anti-freezing method and analysis of Dongxing expansive rock tunnel of Jitu-hun high-speed railway in seasonal frozen soil area[J]. Journal of Natural Disasters，2019，28(3)：17–26.(in Chinese))
[3] 卿三惠，黄润秋. 乌鞘岭特长隧道软弱围岩大变形特性研究[J]. 现代隧道技术，2005，42(2)：7–14.(QING Sanhui，HUANG Runqiu. Study on large deformation characteristics of weak surrounding rock in Wushaoling extra-long tunnel[J]. Modern Tunnelling Technology，2005，42(2)：7–14.(in Chinese))
[4] HOLTZ W G，GIBBS H J. Engineering properties of expansive clays[J]. Transactions of the American Society of Civil Engineers，1956，121(2814)：641–677.
[5] HUDER J，AMBERG G. Sources in marl，clay and anhydrite[J]. Swiss Journal of Architecture，1970，88(43)：975–980.
[6] EINSTEIN H. Tunneling in swelling rock[J]. Underground Space，1979，4(1)：51–61.
[7] FRANKLIN J A. A ring swell test for measuring swelling and shrinkage characteristics[J]. International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts，1984，21(3)：113–121.
[8] WANG L L，BORNERT M，YANG D S，et al. Microstructural insight into the nonlinear swelling of argillaceous rocks[J]. Engineering Geology，2015，193(2)：435–444.
[9] 范秋雁，梁 昕，韩进仕. 非饱和膨胀岩饱和度及胀缩特性试验研究[J]. 岩石力学与工程学报，2020，39(1)：45–56.(FAN Qiuyan，LIANG Xin，HAN Jinshi. Experimental study on saturation and swelling- shrinkage characteristics of unsaturated expansive rock[J]. Chinese Journal of Rock Mechanics and Engineering，2020，39(1)：45–56.(in Chinese))
[10] 张善凯，冷先伦，盛 谦. 卢氏膨胀岩湿胀软化特性研究[J]. 岩土力学，2020，41(2)：561–570.(ZHANG Shankai，LENG Xianlun，SHENG Qian. Study on the swelling and softening characteristics of Lady-Liu expansive rock[J]. Rock and Soil Mechanics，2020，41(2)：561–570.(in Chinese))
[11] 丁秀丽，赵化蒙，黄书岭. 基于吸湿–膨胀分析模型的岩石膨胀变形演化规律研究[J]. 岩石力学与工程学报，2021，40(增2)：3 005–3 013.(DING Xiuli，ZHAO Huameng，HUANG Shuling. Study on the evolution law of rock swelling deformation based on the moisture absorption-expansion analysis model[J]. Chinese Journal of Rock Mechanics and Engineering，2021，40(Supp.2)：3 005–3 013.(in Chinese))
[12] 陈福榜，左清军，吴友银，等. 富水环境下板岩膨胀过程宏–细–微观机制研究[J]. 岩石力学与工程学报，2020，39(1)：126–137. (CHEN Fubang，ZUO Qingjun，WU Youyin，et al. Macro-micro-mechanism of slate expansion in water-rich environment[J]. Chinese Journal of Rock Mechanics and Engineering，2020，39(1)：126–137.(in Chinese))
[13] 于洪丹，陈卫忠，谭贤君，等. 饱和过程中黏土岩变形和水化膨胀特性研究[J]. 岩石力学与工程学报，2022，41(增2)：3 534–3 542. (YU Hongdan，CHEN Weizhong，TAN Xianjun，et al. Study on deformation and hydration expansion characteristics of clay rock during saturation[J]. Chinese Journal of Rock Mechanics and Engineering，2022，41(Supp.2)：3 534–3 542.(in Chinese))
[14] 李兆琛，朱 勇，周 辉，等. 考虑弹性软化的膨胀岩地铁隧道湿温等效模拟方法[J]. 岩土力学，2022，43(增2)：497–507.(LI Zhaochen，ZHU Yong，ZHOU Hui，et al. Method for equivalent simulation of wet temperature of subway tunnel in expansive rock considering elastic softening[J]. Rock and Soil Mechanics，2022，43(Supp.2)：497–507.(in Chinese))
[15] 李 健，谭忠盛. 大断面黄土隧道初期支护与围岩相互作用机制研究[J]. 现代隧道技术，2013，50(3)：79–86.(LI Jian，TAN Zhongsheng. Study on interaction mechanism between primary support and surrounding rock of large section loess tunnel[J]. Modern Tunnelling Technology，2013，50(3)：79–86.(in Chinese))
[16] 黄明利，赵建明，谭忠盛，等. 兰渝铁路木寨岭隧道岭脊段衬砌–围岩结构体系变形受力特征分析[J]. 现代隧道技术，2016，53(6)：89–99.(HUANG Mingli，ZHAO Jianming，TAN Zhongsheng，et al. Analysis of deformation and stress characteristics of lining-surrounding rock structure system in ridge section of Muzhailing Tunnel on Lanzhou-Chongqing Railway[J]. Modern Tunnelling Technology，2016，53(6)：89–99.(in Chinese))
[17] 李树忱，晏 勤，谢 璨，等. 膨胀性黄土隧道钢拱架–格栅联合支护力学特性研究[J]. 岩石力学与工程学报，2017，36(2)：446–456.(LI Shuchen，YAN Qin，XIE Can，et al. Study on mechanical properties of steel arch-grid combined support for expansive loess tunnel[J]. Chinese Journal of Rock Mechanics and Engineering，2017，36(2)：446–456.(in Chinese))
[18] SCHLEISS A J，MANSO P A. Design of pressure relief values for protection of steel-lined pressure shafts and tunnels against buckling during emptying[J]. Rock Mechanics and Rock Engineering，2012，45(1)：11–20.
[19] 左清军，吴 立，林存友，等. 富水软岩隧道跨越断层段塌方机制分析及处治措施[J]. 岩石力学与工程学报，2016，35(2)：369–377. (ZUO Qingjun，WU Li，LIN Cunyou，et al. Collapse mechanism analysis and treatment measures of water-rich soft rock tunnel crossing fault section[J]. Chinese Journal of Rock Mechanics and Engineering，2016，35(2)：369–377.(in Chinese))
[20] 柳厚祥，郑智雄. 高地应力软岩公路隧道泡沫混凝土卸压机制及支护结构研究[J]. 中国公路学报，2016，29(11)：122–129.(LIU Houxiang，ZHENG Zhixiong. Study on pressure relief mechanism and supporting structure of foam concrete in high ground stress soft rock highway tunnel[J]. China Journal of Highway and Transport，2016，29(11)：122–129.(in Chinese))
[21] 汪 波，王 杰，吴德兴，等. 让压支护体系在软岩大变形公路隧道中的应用研究[J]. 铁道科学与工程学报，2016，13(10)：1 985–1 993.(WANG Bo，WANG Jie，WU Dexing，et al. Application of yielding support system in soft rock large deformation highway tunnel[J]. Journal of Railway Science and Engineering，2016，13(10)：1 985–1 993.(in Chinese))
[22] 蔡 峰，孙晓明，王 炯，等. 海下强膨胀软岩动压巷道恒阻让压耦合支护技术研究[J]. 岩石力学与工程学报，2017，36(增2)：3 957–3 964.(CAI Feng，SUN Xiaoming，WANG Jiong，et al. Study on constant resistance yielding pressure coupling support technology for dynamic pressure roadway in strong expansive soft rock under sea[J]. Chinese Journal of Rock Mechanics and Engineering，2017，36(Supp.2)：3 957–3 964.(in Chinese))
[23] 彭 鹏，张顶立，孙振宇. 含软弱夹层隧道围岩变形特性与加固参数设计方法[J]. 岩石力学与工程学报，2021，40(11)：2 260–2 272. (PENG Peng，ZHANG Dingli，SUN Zhenyu. Design method of deformation characteristics and reinforcement parameters of surrounding rock of tunnel with weak interlayer[J]. Chinese Journal of Rock Mechanics and Engineering，2021，40(11)：2 260–2 272.(in Chinese))
[24] 李文江. 隧道力学[M]. 北京：机械工业出版社，2013：124–127. (LI Wenjiang. Tunnel mechanics[M]. Beijing：Mechanical Industry Press，2013：124–127.(in Chinese))
2023, Vol. 42 
