软岩隧洞围岩时效变形与支护结构受力分析

Analyses on Time-dependent Deformation of Surrounding Rock and Stress Characteristics of Supporting Structure in Soft Rock Tunnel

基于典型的Burgers蠕变模型,采用满足Mohr-Coulomb屈服准则的塑性元件与之串联,建立了一种由Burgers蠕变模型与带拉伸截止限的Mohr-Coulomb塑性屈服准则组合而成的复合粘塑性模型,并针对滇中引水工程软岩隧洞进行数值模拟。结果表明,蠕变初期洞周围岩变形增长较快,之后逐渐衰减,变形增长速率随时间推移而减小;隧洞不同部位围岩时效变形特性有所不同,侧墙部位蠕变30d后趋于稳定,但顶拱受软岩流变影响时间较长,到100 d左右才基本达到稳定;支护结构受力随时间变化规律与围岩时效变形规律基本一致。

Based on the classic Burgers creep model, and coupled in series with plastic cell that satisfies Mohr-Coulomb yield criterion, a composite visco-plastic model is established, which is composed of Burgers creep model and Mohr-Coulomb criterion with limit of tension cutoff. In light of Dianzhong Water Diversion Project in Yunnan Province, a typical soft rock tunnel is chosen for numerical simulation. The calculation results indicate that： （a） at the initial stage of creep, the deformation of surrounding rock increases rapidly and then begins to decay, and the growth rate of deformation decreases with time; （b） the time-dependent deformation characteristics of surrounding rock at different parts of tunnel are different, the sidewall tends to be stable after creep for 30 days, while the vault needs 100 days since it is influenced for a long time by the soft rock rheology; and （c） the stress time-varying law of supporting structure is consistent with the time-dependent deformation law of surrounding rock.