Tunnel Volume Loss
Calculate the volume loss of a tunnel excavation, VL = Vs ÷ (π·D²/4)·100, the percentage ratio between the settlement trough volume per metre Vs (m³/m) and the excavated cross-section area (from diameter D). Volume loss quantifies how much soil 'disappeared' relative to the theoretical tunnel volume — caused by face relaxation, overexcavation, tail-gap closure behind the TBM shield and consolidation. It is the key control parameter for urban excavation: well-run EPB/slurry TBMs achieve 0.5-1.5% in soils; values above 2-3% indicate problems and excessive settlement. Enter the trough volume and the tunnel diameter.
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Perda de volume de túnel
A perda de volume (volume loss) é o parâmetro-mestre do controle de escavações de túneis em solo: VL = Vs ÷ (π·D²/4)·100, a razão percentual entre o volume da bacia de recalque por metro Vs (o solo que efetivamente 'sumiu' e apareceu como depressão na superfície) e a área da seção teórica escavada, calculada a partir do diâmetro D. Em outras palavras, mede quanto solo se perdeu além do volume nominal do túnel. As causas são várias e cumulativas: relaxamento do maciço na frente de escavação (se a pressão de face for insuficiente), sobre-escavação (a máquina corta um diâmetro maior que o revestimento), fechamento do gap anular atrás do escudo da tuneladora antes de a injeção preenchê-lo, e consolidação posterior do solo. A perda de volume é o termômetro da qualidade da operação: tuneladoras de frente fechada (EPB e slurry) bem operadas atingem VL de 0,5 a 1,5% em solos urbanos; valores acima de 2 a 3% acendem o alerta vermelho, pois geram recalques excessivos e risco de danos. O conceito é poderoso porque conecta causa e efeito: liga diretamente os parâmetros operacionais da máquina (pressão de face, volume e pressão de injeção de cauda, velocidade de avanço) aos recalques medidos na superfície e ao risco para as edificações. Monitorar e minimizar a perda de volume é, em essência, a arte de tunelar sob a cidade. Informe o volume da bacia de recalque e o diâmetro do túnel.
Related Tools
Maximum Surface Settlement (Tunnel)
Calculate the maximum surface settlement, over the tunnel axis, S_max = Vs ÷ (i·√(2π)), from the settlement trough volume per metre of tunnel Vs (m³/m, the lost soil volume surfacing) and the trough-width parameter i (m, Peck's method). Since the trough is Gaussian, integrating the curve gives Vs = √(2π)·i·S_max, isolating the maximum settlement, which occurs right over the axis. This is the critical value for damage assessment: compared to allowable limits (typically 10-25 mm for sensitive structures), it decides whether the excavation is safe or needs mitigation. Enter the trough volume and the width parameter.
Peck Settlement Trough Width
Calculate the trough-width parameter of the surface settlement induced by tunnelling, i = K·z₀, by Peck's method, from the trough-width parameter K (~0.5 for clays, ~0.25-0.35 for sands) and the tunnel axis depth z₀. The surface settlement from ground loss follows a Gaussian (inverted bell) curve, and i is its standard deviation — the horizontal distance from the tunnel axis to the inflection point, defining the trough width. Larger i means a wider, gentler trough (clays); smaller means narrower and deeper (sands). This parameter is essential to predict damage to nearby buildings in urban tunnels. Enter the K parameter and the tunnel depth.
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.
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.