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相向施工的软弱围岩隧道临近贯通时,两开挖面的扰动区将会叠加,围岩应力及变形异常复杂,存在掌子面大变形和失稳问题。结合狮子垄隧道,采用数值手段分别对单向、相向施工时的隧道围岩应力与位移场进行研究,分析临近贯通时围岩的稳定性。结果表明,相向施工时,随着掌子面前方土体长度的减小,围岩塑性区明显增大,变形加剧,拱效应逐渐减弱,稳定性大大降低;两开挖面间存在极限距离,当2个掌子面距离小于该值时,围岩大范围临近塑性破坏,必须采取有效应对措施,方可保证隧道施工安全。在对掌子面加固、提高初支强度等措施效果分析的基础上,采用竹锚管注浆对狮子垄隧道贯通段掌子面进行加固,并提高初支强度,保证了该软弱围岩大断面隧道顺利安全贯通。
When tunnels with weak surrounding rock are constructed adjacent to each other, the disturbed area of the two excavation surfaces will be superimposed, and the stress and deformation of the surrounding rock are complex. Large deformation and instability of the face are present. Combined with the tunnel of Lizig ridge, the stress and displacement field of tunnel surrounding rock during unidirectional and opposite construction are studied respectively by numerical means, and the stability of surrounding rock is analyzed. The results show that with the decrease of the length of the soil body in front of the face, the plastic zone of the surrounding rock obviously increases, the deformation increases, the arch effect gradually decreases and the stability is greatly reduced. There is a limit distance between the two excavation faces, When the distance between two faces is less than this value, the surrounding rock mass is near the plastic damage, and effective measures must be taken to ensure the construction safety of the tunnel. Based on the analysis of the effect of reinforcement on the face and the improvement of the strength of the initial branch and so on, the reinforcement of the face of the tunnel through the tunnel by means of bamboo anchor pipe grouting and the increase of the initial branch strength are ensured, Section tunnel smoothly safe.