爆破荷载作用下新建与既有隧道支护结构动力响应研究

Study of the Dynamic Response of the Newly-Built and Existing Tunnel Supporting Structure under the Blasting Load

系统研究爆破冲击同时对新建隧道和既有隧道支护结构动力影响具有重要意义。以某隧道接近既有隧道为例,建立爆破施工对既有隧道和新建隧道支护结构的影响三维模型,利用高能炸药材料模型及JWL状态方程来模拟爆破荷载作用下既有隧道的动力响应特性,结合LS-DYNA显式动力分析程序和多物质流固耦合算法较为准确地对新建隧道的爆破机理进行数值模拟,对爆破荷载作用下既有隧道二次衬砌与新建隧道初期支护的动力响应规律展开研究,得到了不同工况下新建隧道二衬和既有隧道初支在不同时刻的振速分布规律、位移变化云图。结果表明:不同围岩等级既有隧道二次衬砌的动力响应规律十分相似,爆破冲击波最先传到既有隧道二次衬砌上迎爆侧边墙上,既有隧道二次衬砌结构上质点沿X方向振速峰值最大,衰减较快。当距离掌子面一定距离后,新建隧道拱脚处振速峰值超过拱顶位置,不同位置振速大小依次是拱脚>拱顶>拱腰。初期支护上质点X、Y、Z 3个振动方向中沿Z方向即隧道中心线方向振动较大,衰减较快。炸药起爆后,新建隧道初期支护上不同位置在爆破冲击波的作用下,沿着掌子面往洞口方向依次发生振动,同一断面上,拱顶和拱脚位置振速较大,施工中应加强监测。

The systematic study of the blasting impact is of great importance to the dynamic response of the newly-buih and the existing tunnel supporting structure. Taking a new tunnel neighboring the existing tunnel as a case, the three-dimensional model about the effect of the blasting construction on the existing and newly-built tunnel supporting structure was established. Combined with the LS-DYNA explicit dynamic analysis procedure and the multi-material flow-solid coupling algo- rithm, numerical simulation on the blasting mechanism of newly-buih tunnel was made with relative accuracy. Besides, the dynamic response rules of the primary supporting of the newly-buih tunnel and the secondary lining of the existing tunnel under different surrounding rock blasting load were studied, thus obtaining the vibration velocity distribution rule and the displacement nephogram change of them under different working conditions. The results show that the dynamic response rules of the secondary linings of different surrounding rocks are very similar, and that the explosive shock wave firstly transfers to the blasting side wall of the secondary lining of the existing tunnel and the peak vibration speed value of the mass point in the secondary lining structure along the X direction is at the maximum and attenuates very fast. When there is a certain distance fromthe working face of tunnel, the peak velocity at the arch foot of newly-built tunnel exceeds to that at the vault, and the vibra- tion velocity in different locations display as arch foot, vault and arch waist from＇high to low in order. The vibration along the Z direction in the initial support with 3 vibration directions of X, Y and Z is larger, that is, the centerline of the tunnel, and its attenuation is faster. After the explosive is detonated, vibration occurs from the working face to the tunnel entrance under the action of blasting shock wave at different positions of the initial support in the newly-buih tunnel. Besides, in the samefracture surface, the vibration velocity in the positions of the vault and of the arch foot is bigger, which should be given more monitoring during the construction.