Tunnel Support Pressure
Calculate the support pressure a tunnel lining must resist, pv = γ·Hp, from the rock mass unit weight γ (kN/m³) and the rock load height Hp (m) — typically from Terzaghi's method or geomechanical classifications (RMR, Q-system). Support pressure is the vertical stress the loosened rock zone exerts on the support (shotcrete, steel sets, final lining), and it drives the structural design of the lining. In shallow tunnels the load may be the full overburden; in deep tunnels, arching reduces it to a fraction. Estimating it correctly is decisive: underestimating leads to collapse, overestimating raises cost. Enter the unit weight and the rock load height.
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Pressão de suporte de túnel
A pressão de suporte é a tensão que o revestimento de um túnel deve resistir, pv = γ·Hp, o produto do peso específico do maciço γ pela altura de carga de rocha Hp. Essa altura Hp — a espessura da zona de rocha afrouxada que pesa sobre o suporte — vem do método de Terzaghi ou de classificações geomecânicas como o RMR e o sistema-Q, que estimam a pressão de suporte diretamente a partir de índices de qualidade do maciço (resistência da rocha, espaçamento e condição das descontinuidades, presença de água). A pressão de suporte é o carregamento de projeto do revestimento: define a espessura do concreto projetado, o perfil das cambotas metálicas, a quantidade de tirantes e o dimensionamento do revestimento definitivo. Há uma física sutil aqui: em túneis rasos, sem recobrimento suficiente para formar o arco, a carga pode ser todo o peso da coluna acima; em túneis profundos, o efeito de arco do maciço limita a carga a uma fração (a altura Hp), tornando o suporte viável. Acertar essa estimativa é decisivo e delicado: subestimar a pressão leva à ruína do revestimento e ao colapso do túnel; superestimar encarece desnecessariamente uma obra que já é cara por natureza. Por isso o projeto combina cálculo, classificação do maciço e, sobretudo, observação contínua (convergência) durante a escavação. Informe o peso específico e a altura de carga de rocha.
Related Tools
Terzaghi Rock Load Height
Estimate the rock load height over a tunnel crown by Terzaghi's classic method, Hp = Cf·(B + Ht), from the rock load factor Cf (depending on mass quality — ~0 for intact rock to >2 for heavily fractured or swelling rock), the width B and the height Ht of the excavation. Hp represents the loosened rock zone above the tunnel that effectively loads the support — Terzaghi proposed that, due to arching in the mass, only a fraction of the total overburden acts on the lining. This loosening-load model is the historic basis for rock tunnel support design. Multiplying Hp by the unit weight gives the support pressure. Enter the load factor, width and height.
Tunnel Face Pressure (EPB/Slurry)
Estimate the face support pressure needed to stabilize the excavation front of a mechanized tunnel, p = K·γ·H, from the earth pressure coefficient K (at rest K₀ ≈ 1−sinφ, or active), the soil unit weight γ (kN/m³) and the axis depth H (m). In closed-face TBMs (EPB or slurry), the pressurized chamber must balance the earth and water pressure at the front, avoiding both collapse (insufficient pressure) and blow-out (excessive pressure). Face pressure is the most critical operational parameter of a TBM, adjusted in real time per cover, water table and soil type. This gives the earth component; total pressure adds hydrostatic water pressure and a safety margin. Enter the earth pressure coefficient, unit weight and depth.
Tunnel Convergence
Calculate a tunnel's convergence — the relative radial deformation of the excavation, ε = (u ÷ r)·100 — from the radial displacement u (the inward movement of the walls toward the center, measured by extensometers or total station) and the excavation radius r, in the same unit. Convergence is the primary monitoring indicator in NATM (New Austrian Tunnelling Method): it measures how much the rock mass deforms after excavation, reflecting stress mobilization and support effectiveness. Low, stabilized convergence indicates a stable mass; high, growing or accelerating convergence signals squeezing, instability or insufficient support, requiring immediate reinforcement. Enter the radial displacement and the tunnel radius.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.