浅埋偏压隧道洞口安全防护关键技术研究OA

Targeting the instability risks of shallow-buried,eccentrically loaded tunnel portals in mountainous highways-under paleo-landslide/deposit conditions,small clear spacing,alignment coupling,and traffic constraints-this paper proposes a coordinated protection and performance-based control framework.Using the Dashiban Tunnel as a case,we develop a technical pathway of"counter-pressure backfilling → advance pipe-roof(large pipes)/full-ring spiles → excavation-followed immediate support and early ring closure → parameterized grouting in depositional sections → coordinated traffic management".We introduce a five-component control vector and a"sequence-advance length-closure-strengthening-monitoring"strategy,establish a closed loop of monitoring-back-analysis-parameter updating,and identify the time window between ring closure and grouting,as well as staggering distances and advance limits for small clear spacing.Results show the framework enables minimal disturbance and rapid stiffness recovery at the portal,reducing unloading-induced deformation and local instability;the grouting"three elements"(pressure,grout take,and hold time)together with the time-window criterion help form an integrated bearing and water-tight boundary.The study yields a replicable,parameterized design and dynamic control scheme,strengthens internal-force and seepage monitoring,and provides implementation and evaluation guidance for similar projects.