泥岩地层盾构隧道下穿既有成昆铁路无预加固施工安全分析

新建地铁隧道下穿既有运营铁路时,如何在无预加固措施下保证新建隧道和既有铁路的安全,是施工的关键。文章依托成都轨道交通9号线一期工程元华停车场东出入场线盾构隧道近接既有成昆铁路工程,采用有限元软件模拟最不利工况下的工程安全性,通过主动托换补偿地层应力损失的可行性以及岩土物理力学参数变化的敏感性。研究结果表明,在泥岩地层、无预加固、有列车荷载作用、注浆压力控制在0.30 MPa及以上条件下,盾构隧道近接下穿既有成昆铁路施工时,能主动托换补偿地层应力损失,限制围岩塑性区发展,满足铁路线路轨道10m弦高低偏差矢度值≤±0.5 mm的管理规定,确保盾构近接施工时的安全。

Analysis on Construction Safety of a Shield Tunnel beneath Existing Chengdu-Kunming Railway without Pre-reinforcement in Argillite

It is critical for the construction safety of a new metro tunnel underneath existing operating railway with⁃out pre-reinforcement measure.Based on the shield tunnel which is located at east depature and arrival line of Yuan⁃hua depot of phase 1 project of Chengdu rail transit line 9 and approaching existing Chengdu-Kunming railway,it simulates the engineering safety in most unfavorable condition,the feasibility of realizing groundstress compensation through active underpinning by grouting and the sensitivities of track deformation to physical and mechanical parame⁃ters changes of soil and rock by FEM software.The research results show that it can compensate stratum stress loss through active underpinning and restrain plastic zone development of surrounding rock,meeting the requirement that vector value of vertical deviation of rail track with 10 m chord should be less or equal to±0.5 mm during con⁃struction of a shield tunnel approaching existing Chengdu-Kunming railway in conditions of argillite stratum,no prereinforcement,train load effect and grouting pressure being 0.30 MPa or more.