剧烈瓦斯爆炸隧道洞口致损机理

Damage mechanism of tunnel portal subjected to severe gas explosion

为探究洛带古镇隧道瓦斯爆炸下洞口衬砌致损机理,对隧道内积聚瓦斯等效、量化研究,采用LS-DYNA建立与洞门几何结构一致的流固耦合数值模型并验证,以RHT模型模拟混凝土并修正参数,对爆炸过程中冲击波的传播特征及强度、洞门致损机理研究分析,并将模拟结果与实际情况对比.研究表明:爆炸冲击波在隧道内无规则的反射效应使其强度剧增、流场复杂,局部位置有聚焦现象,隧道内高压达1. 2~2. 4 MPa;传播过程中,靠衬砌一侧冲击波运动速度较快,形态也由"球状"变为"喇叭"状;当以平面波形态传至洞门时,拱顶冲击波强度增加56%,达2. 8 MPa,并在削竹式洞门周边发生衍射;自隧道传出后,强度逐渐降低,边墙及底板处的冲击波沿纵向径直射出,拱部冲击波向斜上方运动,形成"蘑菇云".爆炸作用下,衬砌曲边墙脚处完全破坏;爆心距7 m范围内衬砌受损严重; 7~15 m范围内拱部几乎未受损;洞门受损严重.缺少围岩的约束作用,洞门拱顶Y向、拱脚X向位移分别达0. 26和0. 14 m,迎爆面、背爆面拉应力分别介于7. 9~31. 5 MPa、4. 9~15. 6 MPa,背爆面出现多个应力峰值,洞门主要为受拉致损.经对比,洞门损伤特征的数值模拟结果与现场实际情况基本一致,可为后续的衬砌灾害处治提供依据.

To investigate the damage mechanism of tunnel portal subjected to gas explosion in the Luodaiguzhen tunnel,equivalent and quantitative studies were carried out on the accumulation of gases in the tunnel,and a fully coupled numerical model with dimensions that were consistent with the actual dimensions was established by LS-DYNA and verified. The RHT model was used to simulate the concrete,and some parameters were modified. The propagation traits and strength of the blast shock wave and the damage mechanism of the tunnel portal were studied. The studies show that the strength of the shock wave is significantly enhanced due to its numerous irregular reflection. This results in a complicated wave field. The wave aggregates in local regions,and the pressure in the tunnel is 1. 2-2. 4 MPa. The wave near the lining travels faster during propagation,and its shape changes from the spherical to horn. The strength of the wave in the vault of the tunnel portal is increased by 56% to reach 2. 8 MPa,and diffraction occurs in the vicinity of tunnel portal. After the wave is propagated from the tunnel,its strength gradually decreases,and the wave,which originally moves along the sidewall and floor,continues to travel along the longitudinal direction. The shock wave along the arch moves upward and forms a"mushroom cloud. "The corner of the sidewall is destroyed completely during the explosion,and the lining suffers serious damage within 7 m of detonation,and the arch is almost intact in the range of 7-15 m. The tunnel portal is also severely damage. Without the constraint of surrounding rock,the displacement of the vault in the Y and X directions of the portal is 0. 26 and 0. 14 m,respectively,andthe tensile stresses that acted at the front and back surfaces of the portal are 7. 9-31. 5 MPa and 4. 9-15. 6 MPa,respectively,and multiple peak stresses occur on the back surface of the portal. The damage of the portal is mainly caused by the tensile stress. By comparison,the numerical simulation results of the damage characteristics of the tunnel portal basically agreed with the actual situations.Therefore,the results can provide useful references for the treatment of lining hazards.