Unexpected performance and cost factors for hard rock TBM. Analyses of specific cases with the thrust- penetration gradient
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This document analyzes factors that influence the thrust-penetration gradient of hard rock tunnel boring machines (TBMs), including: - Rock properties like strength, anisotropy, joints, and stress conditions affect the gradient. Low rock strength and high stress result in a high gradient. - Tunnel diameter impacts the gradient, with smaller diameters having a lower gradient. - Overburden affects the gradient, with higher overburden/strength ratios giving a higher and more variable gradient. - Joint alteration from hydrothermal activity can significantly decrease the gradient by strengthening the rock mass, as seen at the Nant de Drance project.
Unexpected performance and cost factors for hard rock TBM. Analyses of specific cases with the thrust- penetration gradient
- 1. Dr. M. Weh H. Wannenmacher WTC 2014 Marti Holding AG www.martiag.ch Unexpected performance and cost factors for hard rock TBM. Analyses of specific cases with the thrust- penetration gradient • Thrust-Penetration Gradient • Influence of Tunnel diameter • Influence of overburden • Influence of joint alteration Thrust- Penetration Gradient Influence of Tunnel diameter Influence of overburden Influence of joint alteration
- 2. Dr. M. Weh H. Wannenmacher WTC 2014 Marti Holding AG www.martiag.ch Unexpected performance and cost factors for hard rock TBM. Analyses of specific cases with the thrust- penetration gradient TBM-specific influencing factors • Type, spacing and wear rate of cutters. • TBM-diameter. • Thrust per cutter. Intact Rock/ Rock Mass influencing factors: • Intact UCS. • Grade and orientation of anisotropy of rock mass. • Joint conditions, joint orientation towards the tunnel alignment and spacing of joints. • Magnitude and orientation of stress conditions and effects of stress redistribution on rock mass behaviour. Thrust- Penetration Gradient Influence of Tunnel diameter Influence of overburden Influence of joint alteration 0 5 10 15 20 25 30 35 40 0 50 100 150 200 penetration(mm/rev) thrust/cutter (kN) Islisbergtunnel, Silt/Sandstone: 30MPa Gorgier, Marlestone: 28MPa Gorgier, Limestone: 120MPa Bure: Marlestone: 20MPa Bure, Limestone: 130MPa Katzenberg, Limestone: 100MPa Katzenberg: Marlestone, 10MPa Low rock strength: High gradient High rock strength: Low gradient
- 3. Dr. M. Weh H. Wannenmacher WTC 2014 Marti Holding AG www.martiag.ch Unexpected performance and cost factors for hard rock TBM. Analyses of specific cases with the thrust- penetration gradient Scale dependency of tunnel radii on the thrust penetration gradient Small tunnel diameter: Low gradient Big tunnel diameter: High gradient Thrust- Penetration Gradient Influence of Tunnel diameter Influence of overburden Influence of joint alteration 0 0.1 0.2 0.3 0.4 0.5 0.6 0 50 100 150 200 250 thrustpenetrationgradient (mm/rev/kN/cutter) uniaxial compressive strength (MPa) TBM projects with overburden < 1000m r > 5500mm 3500 < r < 5500mm 2500 < r < 3500mm r < 2500m Tunnelradius: Factor 2 in diameter is more than factor 2 in gradient
- 4. Dr. M. Weh H. Wannenmacher WTC 2014 Marti Holding AG www.martiag.ch Unexpected performance and cost factors for hard rock TBM. Analyses of specific cases with the thrust- penetration gradient Influence of stress on the thrust-penetration gradient Relation overburden/UCS < 4: Low thrust-penetration gradient Relation overburden/UCS > 7: High thrust-penetration gradient (+60%) Thrust- Penetration Gradient Influence of Tunnel diameter Influence of overburden Influence of joint alteration y = 0.6363x-0.437 R² = 0.9133 y = 1.2921x-0.495 R² = 0.5069 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0 50 100 150 200 250 300 thrustpenetrationgradient (mm/rev/kN/cutter) uniaxial compressive strength (MPa) TBM radius = 4715mm overburden/UCS < 4, Löschberg 4 < overburden/UCS < 7; Lötschberg overburden/UCS > 7: Lötschberg
- 5. Dr. M. Weh H. Wannenmacher WTC 2014 Marti Holding AG www.martiag.ch Unexpected performance and cost factors for hard rock TBM. Analyses of specific cases with the thrust- penetration gradient Influence of stress on the thrust-penetration gradient Relation overburden/UCS small: Narrow distribution of gradient Relation overburden/UCS high: Wide distribution of gradient Thrust- Penetration Gradient Influence of Tunnel diameter Influence of overburden Influence of joint alteration 0% 5% 10% 15% 20% 25% 30% 35% frequency(%) gradient (mm/rev/kN/cutter) 0% 5% 10% 15% 20% 25% 30% 35% frequency(%) gradient (mm/rev/kN/cutter) 0% 5% 10% 15% 20% 25% 30% 35% frequency(%) gradient (mm/rev/kN/cutter) 0% 5% 10% 15% 20% 25% 30% 35% frequency(%) gradient (mm/rev/kN/cutter) Fine grained migmatitic gneiss (270MPa, overburden/UCS = 6.3) Coarse grained granite (150MPa, overburden/UCS = 9.8) migmatitic gneiss (112MPa, overburden/UCS = 5.55) metamorphic slates (77MPa, overburden/UCS = 5.03) 0.005 0.015 0.025 0.035 0.045 0.055 0.065 0.075 0.085 0.095 0.105 0.115 0.125 0.135 0.145 0.155 0.165 0.175 0.005 0.015 0.025 0.035 0.045 0.055 0.065 0.075 0.085 0.095 0.105 0.115 0.125 0.135 0.145 0.155 0.165 0.175 0.005 0.015 0.025 0.035 0.045 0.055 0.065 0.075 0.085 0.095 0.105 0.115 0.125 0.135 0.145 0.155 0.165 0.175 0.005 0.015 0.025 0.035 0.045 0.055 0.065 0.075 0.085 0.095 0.105 0.115 0.125 0.135 0.145 0.155 0.165 0.175 unstable faceunstable face
- 6. Dr. M. Weh H. Wannenmacher WTC 2014 Marti Holding AG www.martiag.ch Unexpected performance and cost factors for hard rock TBM. Analyses of specific cases with the thrust- penetration gradient Influence of joint alteration on the thrust-penetration gradient Thrust- Penetration Gradient Influence of Tunnel diameter Influence of overburden Influence of joint alteration 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0 2 4 6 8 10 12 14 thrustpenetrationgradient (mm/rev/kN/cutter) overburden/UCS TBM radius = 4715-4725mm Löschberg Nant de Drance Unexpected low gradient expierenced in the access tunnel of Nant de Drance P.S.S. .
- 7. Dr. M. Weh H. Wannenmacher WTC 2014 Marti Holding AG www.martiag.ch Unexpected performance and cost factors for hard rock TBM. Analyses of specific cases with the thrust- penetration gradient Influence of joint alteration (Nant de Drance P.S.S.) Thrust- Penetration Gradient Influence of Tunnel diameter Influence of overburden Influence of joint alteration Healing of joints (growth of chlorite and quartz) due to hydrothermal activity increases strength of rock mass decreases the thrust-penetration gradient significantly .