大断面膨胀土隧道结构受力特性测试研究

Test Research on the Stress Characteristics of the Large Section Expansive Soil Tunnel

研究目的:大断面隧道因其跨度大、形状偏于扁平,在施工过程中表现出独有的力学特点,经常造成围岩大变形侵限、区域性塌方、底鼓和支护结构开裂等施工风险,而这些特点在膨胀土环境中表现的尤为明显,因此研究大断面膨胀土隧道支护结构受力特性具有重要的工程应用意义。本文以银西线庆阳隧道为工程背景,首先通过室内试验确定红黏土围岩的膨胀参数,然后利用现场监测手段对庆阳隧道支护结构的力学特性进行研究,并评价其支护结构受力性能,以期对同类隧道施工起到一定的指导作用。研究结论:(1)隧道膨胀土最大膨胀率为67%,最大膨胀力达到67.42 kP a,施工过程中应加强超前地质预报,尽可能减少水害对施工的影响;(2)隧道拱顶、两侧拱腰及底部具有较大围岩压力,围岩压力呈对称分布,初支闭合后拱顶附近围岩压力基本稳定,但两侧拱腰及仰拱位置围岩压力持续增大;初支闭合后钢拱架受力持续快速增长且受力基本对称,隧道上部初支内钢拱架受力始终较大,拱顶钢拱架应力最大达到1.46 MPa;(3)二衬施作后,初支仍存在一定变形,二衬左右两侧衬砌压力增长显著,二衬两侧拱脚位置混凝土应力增大明显;(4)本研究成果可为大断面膨胀性隧道设计优化和安全施工提供理论指导与科学依据。

Research purposes： Expansive soil tunnel often results in the risk of construction in the large deformation of the surrounding rock, the cracking of the bottom and the support structure cracking. Based on the engineering background of the Qingyang tunnel on Yinchuan - Xi＇ an high - speed railway. First, the paper determined the parameters of red clay surrounding rock by the indoor test, and then researched stress characteristics of the supporting structure in Qingyang tunnel with on - site monitoring method. Finally, the stress performance of the support structure was studied. Research conclusions：（ 1 ） The maximum expansion rate of expansive soil is 67%, and the maximum expansion force reaches 67.42 kPa. The advanced geological prediction should be strengthen and the water damage should be minimized on construction in construction. （2） The tunnel vault, both sides of the arch waist and invert arch have a large symmetrical surrounding rock pressure. After the initial support closed, the surrounding rock pressure near the vault is stable, but the pressure of the arch waist and the inverted arch continued to increase. The symmetry stress of steel arch continues rapidly grow. In the upper part of the tunnel, the stress of steel arch is always larger. The maximum stressreached 1.46 MPa. （3） The initial support deforms after the secondary lining constructed and the lining pressure of the lining on both sides of the two lining increases significantly. The stress of the concrete in the two sides of arch foot is obviously increased. （4） The results provide theoretical guidance and scientific basis for the design optimization and safety construction of large section expansive tunnel.