黄土连拱隧道开挖的模型试验与压力拱分析

针对黄土连拱隧道复杂的施工力学特性，研究黄土连拱隧道动态开挖全过程中隧道轮廓位移、围岩的应力及压力拱分布规律.通过大型室内模型试验模拟黄土连拱隧道中的导洞开挖，利用相关监测元件对隧道轮廓位移、围岩的径向及环向应力进行采集和分析；采用有限差分软件对开挖过程的位移及压力拱进一步分析.研究表明：随着黄土连拱隧道不同导洞的开挖，各监测点位移时程曲线总体形状呈台阶形增长，且各台阶的增长对应各导洞初期开挖的位移突变；黄土连拱隧道的压力拱范围比同等级围岩的连拱隧道更大，先行导洞开挖完时，其拱顶压力拱大约为1D（D为隧道洞高），单洞开挖完时，其拱顶压力拱范围大约1.5D；从第一先行导洞开挖到双洞完成，中隔墙上部围岩压力拱范围经历了0.5D→1D→0.5D→1D的变化，形成了多次应力重分布，对此范围的围岩应及时注浆或打入锚杆，加强支护.
Abstract: The displacement of tunnel contour, the stress of the surrounding rock and pressure arch distribution during the whole process of excavation were studied, according to the complex mechanical properties of construction of the loess double-arch tunnel. A large-scale indoor model test was carried out to simulate the excavation of middle pilot tunnel method in the loess double-arch tunnel. The data of the displacement of tunnel contour and radial and circumferential stress were collected by relative monitoring instruments. Moreover, the finite difference software was used to further analyze the displacement and pressure arch of the excavation process. Results indicate that with the different drifts of loess arch tunnel excavation, the displacement-time curve of each monitoring point develops in the form of step shape. And each step growth corresponds to the displacement mutation of each drift initial excavation. The pressure arch of the loess double-arch tunnel is larger than the double-arch tunnel of the same grade surrounding rock. When the first pilot tunnel excavation is completed, the pressure arch of the tunnel vault is about 1D(D is the height of the tunnel). When the single tunnel excavation is completed, the pressure arch of the tunnel vault is about 1.5D. From the first pilot tunnel excavation to double tunnels completion, the pressure arch of the upper middle wall of the surrounding rock ranges from 0.5D to 1D, 0.5D and 1D. The stress redistribution is formed, thus the upper middle wall of the surrounding rock should be timely grouting or into the anchor reinforcement.