浅埋小净距公路隧道围岩压力分布规律

为了给小净距隧道设计和施工提供科学依据，并为完善中夹岩墙的加固方法奠定理论基础，首先通过对41座小净距隧道的双洞内侧围岩压力进行统计分析，研究了小净距隧道围岩压力的演化特点，分析了垂直围岩压力与单洞开挖宽度、埋深和净距的关系，讨论了双洞内侧侧压力系数与各工程地质参数之间的关系，并基于隧道实际滑裂面，建立了小净距隧道荷载计算模型，提出了小净距隧道围岩压力的计算方法，通过与实测数据及既有研究成果的对比，验证了该方法的合理性及普适性，并基于以上研究成果提出了小净距隧道围岩稳定性控制方法。研究结果表明：小净距隧道垂直围岩压力与水平压力发展趋势基本一致，水平压力发展速率明显大于垂直压力，稳定时间也较短；水平压力受双洞间的相互影响比垂直压力要大，在施工过程中应重点关注水平方向的应力发展；侧压力系数随净距增加而增大，但随埋深、内摩擦角和黏聚力的增加而减小，并普遍小于规范值；所提出的围岩压力计算式对于复杂小净距隧道具有较好的适应性，并能对施工过程中小净距隧道的围岩压力进行估算；小净距隧道围岩稳定性控制应从合适的施工方法、合理的支护设计以及实时的监控量测3个层面考虑，具体的控制对策应结合围岩条件和工程特点进行实施。

Distribution of Surrounding Rock Pressure of Shallow Highway Tunnels with Small Spacing

This study offers a scientific basis for the design and construction of small clear distance tunnels, and lays the theoretical foundation for perfecting the reinforcement method of a middle-rock wall. Based on a statistical analysis of the surrounding rock deformation and stress of 41 small clear distance tunnels, the space-time evolution laws of the surrounding rock deformation and pressure were studied. The relationships among the vertical surrounding rock pressure and interval, the overburden depth, and the geological parameters of the surrounding rock were analyzed. The relationships between the lateral rock pressure coefficients and some engineering geological parameters were discussed. Based on the actual sliding surface of the tunnel, the load calculation model of a small distance tunnel was established, and a formula for the surrounding rock pressure of small clear distance tunnels was deduced. Through a comparison with the measured data and other equations, the rationality and universality of the proposed method were shown. Based on the above research results, the surrounding rock stability control method was proposed. The results show that the trend of the development of the horizontal surrounding rock pressure is consistent with the vertical pressure, whereas the development rate is slightly different. The development rate of the horizontal pressure is greater than that of the vertical pressure, although the period of stability is relatively shorter. The effect of the interaction between the two holes on the horizontal pressure is greater than that on the vertical pressure. During the construction process, the horizontal stress should be of focus. The lateral rock pressure coefficients increase with the interval, which decreases with the depth, angle of internal friction, and cohesion. In addition, its value is less than that in a single-hole situation. The proposed formula can be well adapted to small spacing tunnels, and the rock pressure can be predicted when considering the regularities in the space-time evolution. The stability control should include the appropriate construction methods, a reasonable support design, and real-time monitoring, and the specific control measures shall be carried out considering the surrounding-rock and engineering characteristics.