BREAKTHROUGHS IN TUNNELING – short course University of Denver – 9-11 September 2019
GROUND FREEZING FOR SHAFTS AND TUNNELS
Filippo Mira-Catto Grouting and Ground Freezing Manager Bauer Foundations Corp. – Odessa (FL)
© BAUER AG, 86529 Schrobenhausen GROUND FREEZING
PRINCIPLE: To change the pore-water into a solid wall of ice, which bonds the soil particles together, rendering the strata both strong and impermeable
© BAUER AG, 86529 Schrobenhausen GROUND FREEZING
Improved Soil Properties
• Strength: frozen soil can be likened to a weak concrete or rock therefore complete stability can be assured
• Impermeability: common to all frozen soil types thus the requirement for dewatering/pumping is eliminated
© BAUER AG, 86529 Schrobenhausen GROUND FREEZING
Frozen conditions are created by circulating a cold fluid through a series of coaxial pipes, drilled in the ground.
The fluids utilized are two: • Brine (Water – Calcium Chloride) • Liquid Nitrogen (LN)
© BAUER AG, 86529 Schrobenhausen BRINE – INDIRECT METHOD
© BAUER AG, 86529 Schrobenhausen LN – DIRECT METHOD
© BAUER AG, 86529 Schrobenhausen THE DIFFERENT FREEZING METHODS
© BAUER AG, 86529 Schrobenhausen THE GROUND FREEZING PROCESS
© BAUER AG, 86529 Schrobenhausen INFLUENCE OF UNDERGROUND WATER MOVEMENTS
10
9
8
7
6
5 NITROGEN -150 °C 4
3
2
critical (m/day) groundwaterspeed critical 1 BRINE -33 °C 0 0.70 0.80 0.90 1.00 1.10 1.20 1.30 spacing between freezing pipes (m)
© BAUER AG, 86529 Schrobenhausen FREEZING TIME vs PIPE SPACING
40 BRINE -33 °C CLAY 35 SAND 30
25
20
CLAY 15 freezing time (days) time freezing SAND 10
NITROGEN -150 5
0 0.70 0.80 0.90 1.00 1.10 1.20 1.30
spacing between freezing pipes (m)
© BAUER AG, 86529 Schrobenhausen UNCONFINED COMPRESSION STRENGTH
25.0
) SABBIASAND 20.0 MPa (
15.0 LIMOSILT strength
10.0 ARGILLACLAY compression 5.0
GHIACCIOICE
0.0 Unconfined 0 -5 -10 -15 -20 -25 -30 -35 Temperature (°C)
© BAUER AG, 86529 Schrobenhausen Soil conditions: • Unit weight, porosity, water content, temperature of the soil water, degree of saturation • Soil Mineralogy (quartz and clay content)
Project Requirements: • Distribution of the freezing pipes • Ground Freezing Method
© BAUER AG, 86529 Schrobenhausen Thermal Calculation • Evaluation of the freezing process • Freezing time • Maintenance time
Structural analysis of the freezing body
© BAUER AG, 86529 Schrobenhausen THERMAL CALCULATION SHAFT
© BAUER AG, 86529 Schrobenhausen THERMAL CALCULATION SHAFT
© BAUER AG, 86529 Schrobenhausen Key Points for Ground Freezing Process:
• Measuring of the drilling deviation in “Real Time” in order to understand the frozen wall integrity and any possible interference with the excavation stage
• “Real time“ monitoring system for ground temperature
© BAUER AG, 86529 Schrobenhausen Temporary excavation support for: • Cross passages realization • Rescue of Tunnel Boring Machine • Break-in and Break-out for Tunnel Boring Machine • Tunnel excavation • Shafts • Groundwater Cutoff Wall
© BAUER AG, 86529 Schrobenhausen Berlin, Germany – Staatsoper
Frozen soil wall
© BAUER AG, 86529 Schrobenhausen Cairo, Egypt – Greater Metro Line 3 Project
Frozen ground ring for TBM rescue
© BAUER AG, 86529 Schrobenhausen Uskudar Station Istanbul, Metro Line 5 Turkey
Frozen Ground ring for TBM Break-in
© BAUER AG, 86529 Schrobenhausen Ismailia Tunnel - Egypt
© BAUER AG, 86529 Schrobenhausen • Twin tube road tunnel under passing the Suez Canal • TBM diameter: 13m • Max depth below ground: 70m • Soil: very fine and quick sand • 4 cross passages every km of tunnel • 2 cross passages located partly in clay
© BAUER AG, 86529 Schrobenhausen Ismailia Tunnel - Egypt
Thermometer Pipe
Dewatering Pipe
Frozen Area
Typical Section of Cross Passage © BAUER AG, 86529 Schrobenhausen Ismailia Tunnel - Egypt
3D view of drilling rig working from Westbound tunnel on mobile platform © BAUER AG, 86529 Schrobenhausen Ismailia Tunnel - Egypt
Blow-out Preventer © BAUER AG, 86529 Schrobenhausen Ismailia Tunnel - Egypt
Drilling Layout and Brine Circuit © BAUER AG, 86529 Schrobenhausen Ismailia Tunnel - Egypt
© BAUER AG, 86529 Schrobenhausen Ismailia Tunnel - Egypt
Frozen Wall Evolution © BAUER AG, 86529 Schrobenhausen Ismailia Tunnel - Egypt
Brine Circuit © BAUER AG, 86529 Schrobenhausen Ismailia Tunnel - Egypt
Excavation of Cross Passage © BAUER AG, 86529 Schrobenhausen POWISLE STATION C13 –METRO LINE 2 WARSAW
© BAUER AG, 86529 Schrobenhausen Cross Section
© BAUER AG, 86529 Schrobenhausen Geological Conditions
© BAUER AG, 86529 Schrobenhausen Freezing Pipes Array
© BAUER AG, 86529 Schrobenhausen Break-through between central DW
© BAUER AG, 86529 Schrobenhausen LN Freezing circuit
© BAUER AG, 86529 Schrobenhausen Brine Freezing circuit
© BAUER AG, 86529 Schrobenhausen © BAUER AG, 86529 Schrobenhausen Ground freezing technique is a valid temporary support for underground structures Economically competitive with very fine soils, wherein recourse injection grout is required Due to real time monitoring, it’s a safe technique for workers Non-polluting geotechnical process
© BAUER AG, 86529 Schrobenhausen THANKS FOR YOUR ATTENTION !!
Filippo Mira-Catto Grouting and Ground Freezing Manager