偏压小间距隧道施工力学行为及围岩破坏规律

为研究偏压小间距隧道施工力学行为及围岩破坏规律。在CD法施工下,通过建立偏压小间距隧道有限元模型,利用ABAQUS有限元软件在不同开挖顺序及不同隧道间距下对偏压小间距隧道施工过程进行了动态模拟与分析,基于强度折减法基本原理,探讨了不同隧道间距下围岩塑性破坏规律,确定了合理隧道间距。研究结果表明:①在不同开挖顺序下,先行左洞开挖方式要优于先行右洞:②随着隧道间距的增加,左洞围岩位移不断减小,右洞围岩位移先减小后增加;③随着隧道间距的增加,沿中间岩柱竖向中心线的水平位移逐渐减小;竖向应力则表现为先减小后增大的规律;④右洞开挖完成后,两洞初期支护中右拱腰处的弯矩明显大于拱顶处,而轴力则反之;⑤随着隧道间距的增加,中间岩柱塑性贯通程度逐渐弱化,安全系数不断提高,等效塑性应变逐渐减小。研究结果可为偏压小间距隧道的设计与施工提供依据。

Mechanics Behavior and Surrounding Rock Failure Law of Small-spacing Tunnel with Unsymmetrical Loading under Construction

The mechanics behavior and surrounding rock failure law of small-spacing tunnel under construction with unsymmetrical loading were studied via finite element method. The construction process (with CD (Center Diaphragm) construction method) with varied excavation sequence and tunnel distance was dynamically simulated and analyzed in ABAQUS. The rule of the plastic damage of surrounding rock under different spacing was discussed based on strength reduction method, and the reasonable tunnel spacing was determined. Results manifested that: 1) as for different excavation sequences, excavating the left tunnel first was superior to excavating the right tunnel first; 2) with the expansion of tunnel spacing, the displacement of surrounding rock of the left tunnel decreased continuously, while that of the right tunnel declined first and then increased; 3) also with the elongation of tunnel spacing, the horizontal displacement along the vertical center line of the intermediate rock column dropped gradually, whereas the vertical stress first reduced and then rose; 4) When the excavation of the right tunnel is completed, the bending moment at the right arch waist in the initial support of the two tunnels was obviously greater than that at the arch top, while the axial force was to the opposite; 5) with the increase of tunnel spacing, the plastic penetration degree of the intermediate rock column gradually weakened, the safety coefficient constantly improved, and the equivalent plastic strain gradually decayed. The research findings provide basis for the design and construction of small-spacing tunnel under unsymmetrical loading.