针对软岩地层中浅埋大断面隧道进洞施工下穿运营公路极易造成地表沉降超限、塌方与威胁行车安全这一难题，以贵州省桐梓隧道4#斜井洞口施工下穿运营公路为例，提出洞内外综合加固方案。综合加固方案主要包括: 1)安装临时钢骨架路面缓冲结构，保证公路畅通，减少对公路的扰动； 2)在洞口浅埋段进行地表注浆，改善围岩稳定性，堵塞裂隙水通道； 3)管棚支护与双层超前小导管预注浆相结合，采用台阶预留核心土掘进方案，确保挖掘机铣刨时围岩稳定； 4)设置一种新型锁脚锚杆，以提高锚固岩石的稳定性。通过沉降和位移监测数据，验证了该加固方案的有效性。与常规山岭隧道洞口施工方案相比，采用该方案有效控制了复杂地形隧道洞口的沉降值和超挖，保证了地面交通的畅通，减少了喷射混凝土的消耗，防止了塌方、冒顶、滑坡等地质灾害的发生。
When shallowburied largecrosssection tunnel crossing underneath
operational highway in soft rock stratum, problems such as over settlement,
collapse, and hidden danger to highway easily occur. Hence, a case study is
conducted on the #4 inclined portal of the Tongzi tunnel crossing underneath an
operational highway in soft and waterrich strata in
Guizhou, China. Then, comprehensive reinforcement inside and outside tunnel is
proposed, which include: (1) The temporary steel bridge guarantees the smooth
flow of the highway and scatters concentrated load. (2) In the shallow section
of the tunnel portal, surface grouting is carried out and the surrounding rock
stability is improved by blocking the water paths in the cracks. (3) The pipeshed support, combined with pregrouting
with a doublelayer micropipe, and the application of
bench reservation core soil are used to ensure the surrounding rock stablility
during the excavation with a milling machine. (4) A new type of locking anchor
is proposed to enhance the stability of the anchoring rock. Finally, the
effectiveness of the scheme is confirmed by monitoring and measurement.
Compared with the conventional mountain tunnel portal construction plan, the
methods recommended can effectively control the complex terrain tunnel
settlement and overbreak, ensure the smooth flow of surface traffic, reduce the
consumption of shotcrete, and avoid collapse, roof collapse, landslides, and
other geological disasters.
