Roger Storry, Bouygues Civil Works: Geotechnical challenges and solutions at the Port of Miami Tunnel Project
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Roger Storry, Bouygues Civil Works: Geotechnical challenges and solutions at the Port of Miami Tunnel Project



Roger Storry, Geotechnical Director, Bouygues Civil Works delivered this presentation at the 2013 Australian Tunnelling conference. The two day conference is supported by the Australasian Tunnelling ...

Roger Storry, Geotechnical Director, Bouygues Civil Works delivered this presentation at the 2013 Australian Tunnelling conference. The two day conference is supported by the Australasian Tunnelling Society and brings together tunnelling leaders, engineers and industry experts to share best practice in tunnelling design, construction, safety and maintenance.

The 2012 program focussed on updates from Australasia’s current and future projects, plus case studies from leading International projects - sharing best practice and lessons learnt from the forefront of the latest tunnelling projects. For more information about the event, please visit the conference website:



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Roger Storry, Bouygues Civil Works: Geotechnical challenges and solutions at the Port of Miami Tunnel Project Roger Storry, Bouygues Civil Works: Geotechnical challenges and solutions at the Port of Miami Tunnel Project Presentation Transcript

  • Geotechnical Challenges and Solutions at the Port of Miami Tunnel Project R. Storry , Geotechnical Director Bouygues Civil Works 12th Australian Tunnelling Conference, Melbourne, 2013
  • CONTENT of PRESENTATION  Project Introduction and Scope  Geological Challenge of the Project  Ground Investigation Preformed  Construction Challenges; – Shafts – Tunnelling – Spoil Conditioning – Hyperbaric works – Cross Passages
  • BACKGROUND  The Port of Miami is Miami’s second largest economic generator. The Project will provide direct access to the Port of Miami cruise and cargo ports from the Interstate Highway System – Increasing the cargo capacity (currently 6.8 million tons of cargo) – Eliminating cargo truck traffic in Downtown Miami (currently about 7000 movements daily)  Public-Private Partnership (PPP) Project – Design-Build-Finance-Operate-Maintain – 55-Month Design & Construction Schedule – 30-Year Operation/Maintenance Period  Total Construction Cost – US $710 Million – Geotechnical Contingency/Risk Sharing Program- $180 Million
  • PROJECT LOCATION Atlantic Ocean Watson Island Biscayne Bay City of Miami Miami Beach Dodge Island Project Site
  • PROJECT SCOPE Roadway Improvements Bridge Widening MacArthur Causeway Bored Tunnels Biscayne Bay Government Cut Channel Tunnel Portal Port of Miami Dodge Is. Tunnel Portal POM Roadway Improvements
  • SUMMARY OF TUNNEL BORES AND CHALLENGES  2 tunnels each 1.27 km long  Tunnel bore 12.87m (11.3m ID)  8 piece rings using 1.7m long, 615mm thick universal segments  5% maximum grade and a tight horizontal curve Rmin= 305m  Low ground cover : from existing grade to 1.5 Tunnel Dia. ( less than 1 Dia. in Channel)  Tunnel Separation: 1/3 to 1 ¼ Dia. (edge to edge)  Cross passages required every 240m (5 number) Image courtesy of BCWF/Jacobs
  • PROJECT SCHEDULE Project Start: October 2009 Notice to Proceed (Construction): May 2010 TBM Erection: August-November 2011 TBM Launch from Watson: November 11, 2011 TBM Arrival Dodge (Breakout): July 31, 2012 TBM Turn around: Three months TBM Launch from Dodge: October 29, 2012 Final TBM Break out: May 2013 Project Substantial Completion: May 2014
  • GEOLOGICAL CHALLENGE  Project site consists of man-made islands at sea-level and carbonate sedimentary sequence (10,000 to 2 Million years old).  Heterogeneous profile of relatively thin variably cemented sedimentary rock layers, loose sediments and intermediate geo-materials which vary both laterally and vertically.  Geologic Units : Miami Limestone Formation (S3), Fort Thompson Formation (S5), Anastasia Formation (S6), Key Largo Formation (S7) & Tamiami Formation (S8).
  • GEOLOGICAL CHALLENGE  Biscayne Aquifer: Highly Permeable and interconnected to Atlantic Ocean  Tunnelling challenges –  First time large diameters tunnelling attempted in Florida  highly permeable, up to k=10-2m/sec and void content up to 60%, (imposes restriction of type of TBM),  unstable ground, low ground cover, high hydrostatic pressures; and  varying mixed-faced conditions  Sound technical solutions required
  • GEOLOGICAL CHALLENGE – LAYER S7 • 27m to 36m bgl. SPT N = significant zones <10 and locally SPT N zero • Average Core Recovery = 26 % ?? What is the real Geological Model ??
  • COMPLEMENTARY GROUND INVESTIGATIONS  Complementary Ground Investigation (CGI);  Critical to confirm the ground model – In strata Layer 7 the existing GI recovery averaged only 26%, with SPT N of zero at >30m depth;  Conventional techniques – SPT, rotary coring, shallow CPT, geophysical surveys  “Unconventional” techniques – Deep CPT’s , 150 to 300 mm Sonic Cores  Specific Techniques – Large Diameter Shafts (2.1m), Downhole Video, Hydrophysical Investigation
  • COMPLEMENTARY GROUND INVESTIGATIONS  Complementary Ground Investigation (CGI);  Performing the works within cruise ship channel was a great challenge to overcome - GI work was carried out on a 24hr / day basis when no cruise ships were in port (1 to 3 days per week).  Biscayne Bay is an aquatic preserve strictly managed – no spillage or leakage
  • SPT and ROTARY CORING  Complementary Ground Investigation (CGI) Layer S5 Layer S6 Layers S1 - S4 Layer S8
  • COMPACTION GROUTING TRIAL (CA REQUIREMENT)  Purpose:  Treat zones of loose sand foreseen by tender interpretation  Define parameters for full scale grouting to improve bearing capacity in loose sand areas in Layer 7 where intersected by TBM  Results:  Conclusion: The Layer 7 was not able to be densified by compaction grouting despite having significant zone of SPT N <10  No large zones of very loose sand on Layer 7 – “What is the Geological Model?”
  • SONIC CORING  Greatly enhances recovery;  150mm samples typically disturbed but full material recovery.  Compression of material inside barrel indicated very porous, collapsible formation (indication of porosity range 20 to 80%).  Coralline limestone  Lack of sand  Selection of geotechnical parameters remained a concern.
  • LAYER S7 – CONE PENETRATION TESTING  Cone Penetration Test (CPT)  Provided continuous profile of soil parameters  Qc= 0 to 58 MPa (avg. <8 MPa)  Where Qc<5.5 ground considered to be unstable  73 no. CPT’s
  • SITE SPECIFIC CPT CORRELATION Pore pressure (bar) 0 4 0 4 8 12 16 20 16 Cone resistance, qc (MPa) 8 12 20 -78 Approx 2 inch -80 -82 A -84 -86 G -88 Elevation (ft) -90 F -92 P103 GT4 cpt 1 qc fs -94 G -96 -98 pwp rec Dr=20% fs=0.5v'tan20 -100 Approx 2 inch A+ -102 -104 E -106 -108 0 20 40 60 Recovery (%) 80 100 0 40 80 120 Friction, fs (kPa) 160 200
  • GEOLOGICAL CHALLENGE – SONIC CORING Layer S6 Layer S7  Complete material recovery enable correlation with CPT
  • COMPLEMENTARY GROUND INVESTIGATION  Borehole video compared to sample recovered by sonic drilling Approx 3 inch  Start to understand that this is an open coralline limestone  Collapsible structure
  • LARGE DIAMETER SHAFTS Purpose;  Confirm the geologic/geotechnical conditions of Layer S7  Evaluate stability of excavation in Layer S7  Obtain bulk samples for conditioning trials  Excavated using a BG-40 Drilled Shaft Rig (2100mm dia/ 34m deep)  Radar profiling of shaft excavation (Sonicaliper) and shaft wall videography
  • GEOLOGICAL CHALLENGE – FINAL GROUND MODEL  Total of 152 investigation holes complementing 87 holes pre contract holes – about 1 hole every 10m of tunnel. Additional 126 investigation holes for other project components. Layer S7 – Borehole camera Layer S7 Coral heads in calcarenite matrix – KEY LARGO LIMESTONE
  • FINAL GROUND MODEL (Partial section) Layer S7 - locally CPT qc <2.5MPa
  • SOIL CONDITIONING LABORATORY TRIALS  Laboratory index tests to assess feasibility of soil conditioning once a deficit of “fine material” was identified by the GI in the Key Largo layer: • bulk samples of excavated materials • range of soil mixtures & sample gradings • range of water contents • range of conditioning treatments – foams, polymers, thick mortar • slump tests to assess conditioned soil
  • SOIL SAMPLING  Bulk samples from ‘Large Diameter Shafts’  Mechanically excavated materials - representative of TBM spoil  Grading analysis and water content measurements Large Diameter Auger Shaft arisings Layer S4/5/6 Layer S7
  • EPB SOIL CONDITIONING APPLICATIONS Average grading curves : Layers S1 to S6, S7 Silt and S8 Average grading curves : Layers S7
  • SAMPLE ASSESSMENT  Measured quantities of soils, ‘Channel’ water and conditioning agents  Assessment based on: • Slump value • Shape of slumped soil cone • Segregation of liquid • ‘Suitable’, ‘Borderline’, ‘Not suitable’ samples (Peila et al, 2009) • Characterisation: grading, water content, vane shear strength SUITABLE Paste formed, regular slump BORDERLINE Paste formed, too stiff BORDERLINE Paste formed, too fluid NOT SUITABLE No paste formed, liquid segregation
  • SPOIL TESTING - OBYONE  Due to the importance of the spoil conditioning for the project and the risks involved further testing was performed using the Bouygues in-house laboratory model EPB apparatus OBYONE (container of soil and water shipped to Paris!).  The advantage of this apparatus for complex ground conditions is that it replicated more closely the conditions at pressure in the plenum using; i. Pressurised sample mixing / conditioner injection (foam, polymer) ii. Extraction through screw conveyor iii. Fully monitored – mixer torque, screw torque & pressure gradient PRESSURISED SAMPLE MIXING TANK SCREW CONVEYOR FOAM INJECTION LINE
  • SPOIL TESTING CONCLUSION  Soils without Layer S7/Key largo Limestone could be effectively conditioned  Not feasible to reliably & robustly condition samples of Layer S7/Key Largo even with the addition of 30% ‘thick mortar’ + 1 - 2% water-absorbent / viscosifying polymer due to;  Very coarse grading with low sand / fines content  Heterogeneity of in-situ material  High in-situ porosity, water content and groundwater pressure  Index test results confirmed by pressurised OBYONE model EPB tests
  • Construction Challenges
  • GROUND CONDITION CHALLENGE – HIGH PERMEABILITY  Highly permeable strata inhibited the use of slurry wall cut-off trenches  Solution - Cutter Soil Mixing panels with “I” beams and tie-back anchors, tremied base slab and tensioned tie-down elements.  Shaft depth reduced to limit excavation in the stronger layers (resulted in extending the tunnels by 91m each tube)
  • WATSON ISLAND LAUNCH SHAFT  S1 The shaft base was tremie poured concrete; single row of tiebacks was used for the walls and tie-down anchors were used to resist uplift of the base slab after dewatering Shaft Dmax= 13m Tie Back 16 Strand Anchors; 48m long S4 S6 Key Largo S7 18 TO 30m deep Tension Elements to resist uplift of slab
  • WATSON ISLAND & DODGE ISLAND PITS Watson Island Dodge Island
  • TUNNEL ALIGNMENT CHALLENGE  Shaft optimisation (single shaft on each island located within constrained environment) resulted in a spacing between the tunnel tubes of <4m at both extremities in poor ground  Very low ground cover in very poor material (fill and bay bottom silts) through the initial 150m of boring   risk of instability between and above excavations Ground Treatment Solutions:  Construct overburden to provide ground cover to TBM  Inter-tube CSM barrettes  Shallow soil mixing
  • OVERBURDEN Overburden – cement treated base with geotextile to provide 3m minimum cover to TBM  For the CSM to be an efficient shaft support system the shaft base level was raised resulting in the TBM being partially above the existing ground
  • TUNNEL TUBE PROXIMITY CSM Barrettes Panels  Inter-tube reinforcement using CSM panels anchored into the competent Fort Thompson Limestone Layer  2.8m long panels hit and miss Central Barrettes until bore separation >7m
  • VERY SHALLOW GROUND COVER Shallow Soil Mixing  2.7m diameter SSM tool  Treatment over both tubes (on Dodge this required the demolition and rebuilding of a truck bridge access ramp)  Design strength 3MPa Shallow Soil Mixing - 3 to 7m deep
  • UNSUITABLE SPOIL GRADING  High permeability and environmental concerns regarding loss of slurry led to the selection of an EPB TBM as the only feasible solution for the project  Following complementary GI and extensive soil conditioning trials it was concluded that the Layer S7/Key Largo spoil could not be adequately conditioned so jeopardising the face stabilisation process.  In additional the chemically dissolved Key Largo Limestone was interpreted to be unstable / metastable  Confinement control was particularly important as significant lengths of this large diameter tunnel had a ground cover of less that 1 tunnel diameter.
  • UNSUITABLE SPOIL GRADING  EPB process was adopted where ground conditions / spoil grading suited (two thirds of the bored tunnel length).  Conditioning was achieved using foam and a water absorbent polymer specially developed for use with saline ground water conditions. Very challenging with >3.5bars water pressure.  Where the Key Largo limestone (Layer 7) was encountered the granular spoil could not be sufficiently conditioned to provide to face stabilisation and an alternative solution was required.
  • POMT TBM – MODIFICATION FOR WCP  The solution adopted to enable safe tunnel excavation where effective spoil conditioning was considered not possible was a process named Water Control Process (WCP)  WCP was utilized where the Key Largo layer was intersected  The plenum is full of water at hydrostatic pressure and the excavated rock is evacuated via the screw conveyor, through a crusher (100mm down) into a hydraulic circuit up to the surface • Supply density ~1.05 • Flow – 1000m3 / hr (4m/sec in pipe) • Return density ~ 1.4 (max)
  • WATER CONTROL PROCESS  Important - the use of the WCP process requires that the excavation face be self-stable.  The Key Largo limestone layer was determined to be unstable leading to a significant risk of face instability and the inability to construct and grout the segmental lining in place.  Ground treatment was therefore required to provide stability prior to excavation.
  • FORMATION GROUTING – FACE STABILITY S6 S7  Formation Grouting of Layer S7 in 3m long Stages  Top down method used with “target volume injection” to a limiting pressure  Design target grout volume to stabilise was 40% of the rock mass  Double flush circulation rotary drilling used with water
  • FORMATION GROUTING – FACE STABILITY • “Unusual” grout mix - Pumpable, thixotropic, stable, low mobility grout but with high penetrability but with grout mix. • Design requirement ~1 MPa strength (avg. 2 MPa achieved)
  • FORMATION GROUTING DESIGN Watson Island Government Cut Shipping Channel Very restricted working hours Dodge Island
  • FORMATION GROUTING CROSS PASSAGES 2 & 3 – GROUTING AND GROUND FREEZING  Work performed onshore Grouting at CP3 (Watson and Dodge Islands) and Grouting at CP2 offshore in channel
  • FORMATION GROUTING  Work limited to the period when no cruise ships were in the channel - a window of only 1 to 3 days per week  Barges had to be set up and removed from the channel each time work was undertaken
  • FORMATION GROUTING  Grouting campaign comprised;   1,050 holes (~30,000m of drilling) ~50,000m3 of grout injection
  • CROSS PASSAGES and INSPECTION PLUGS Cross Passage ‐ CSM Treatment  Cross Passage ‐ Formation Grouting & Ground Freezing Treatment Intervention Plug – CSM Treatment
  • CROSS PASSAGE GROUND TREATMENT  5 cross passages required between the main bored running tunnels  Due to the highly permeable/loose nature of the soils pretreatment is required  CP1, CP4 and CP5 pretreated from ground surface using CUTTER SOIL MIXING – overlapping panels to form a treated block  CP2 and CP3 – Surface access restrictions prevented the use of CSM so ARTIFICIAL GROUND FREEZING was adopted
  • CROSS PASSAGE – CSM EXCAVATION  CSM treated cross passages constructed using traditional tunnelling methods:  Excavation with small excavator, jack hammer.  Support by steel arches and shotcrete  Installation of waterproofing membranes  In situ concrete lining
  • GROUND FREEZING – PRE GROUTING  At CP2 and CP3 - Pre-grouting of Layer S7 to control ground water and to mitigate potential long term stability problems after thawing of the ice  Grout volumes of up to 69% of the volume of the treatment zone  Residual permeability of about 10-4m/sec (2 orders reduction)
  • GROUND FREEZING - DESIGN  Double row of freeze pipes selected as the optimal solution  48 units at CP3 and 45 at CP2 plus monitoring tubes
  • GROUND FREEZING – WEST BOUND TUNNEL  Surface freezing circuit in second bore (red lines in sketch) 20kW plant in WB tunnel at CP2 and CP3
  • GROUND FREEZING – FREEZING UNITS  Ammonia cooled freeze plants  Freeze plants located on surface as system not safe for underground environment  2No. working plants (400Kw and 350Kw) and one back-up plant (400Kw)  Brine supply temperature ~ -30°C to -33°C  Monitoring system in place to alert on any plant malfunctions
  • GROUND FREEZING – TECHNICAL DATA FOLLOW-UP Brine temperature and flow – minus 33°C achieved at CP  Monitoring Pressure in ice ring compared to external – build up of pressure not robust  38no. instruments installed on the freezing equipment and brine supply network  527 separate instruments have been installed at CP2 and CP3 to monitor the progress and performance of the ground freezing.  Day to day monitoring - over 5,000,000 individual data points for a 24 hour period
  • GROUND FREEZING – CP EXCAVATION  Arch ribs (circular) and shotcrete installed at 1m c/c.  Safety measures – emergency door, 24 hour working, back-up freeze plant and back-up power supply.
  • TBM HYPERBARIC INTERVENTION PLUGS  Highly permeable ground made conventional hyperbaric interventions for routine maintenance impossible  Intervention plugs – (Cutter Soil Mixing overlapping panels 2.8m by 1.2m) at approx. 200m intervals provided “safe havens” for cutter disc / tool inspection and changes  Treated ground strength 3MPa and permeability <10-6 m.s-1 CSM “plug” to enable safe maintenance stoppage
  • TBM BREAK-IN : 11 November 2011
  • THE TBM TURNAROUND  To avoid the logistical issues (dismantling and transportation) the TBM was turned around and re-launched within the Dodge Island Shaft using a specially designed turntable (complicated by the 5% incline of the TBM at breakout)  The actual sliding and turning of the shield took 9 days.
  • FINAL TBM BREAKOUT 6th MAY 2013  Tunnel boring completed 6th May 2013  Ground Freezing for cross passages completed mid November 2013  Project on schedule for opening in May 2014
  • CONCLUSIONS  Complex underground construction in challenging ground conditions requires comprehensive ground investigations to develop a robust understanding site geological/geotechnical model.  Sufficiently detailed technical and method studies are required in advance of the works to discover and mitigate potential risks.  The investment in the ground investigation, although significant, enabled a significant project risk to be identified, fully understood and mitigated in advance of tunnelling.
  • 1. Storry, R.B., Brais, L., Pascual, P. 2013. A Geotechnical Challenge at the Limit,: TBM Tunnelling beneath the Port of Miami, Florida, USA. World Tunnel Congress 2013 Geneva. Anagnostou & H. Ehrbar (eds). 2. Storry, R.B., Pina, R.M., Hight, D.W. 2013. Ground Investigation Challenges at the Port of Miami Tunnel Project, Florida. Rapid Excavation and Tunneling Conference 2013 Washington. DiPonio & Dixon (eds). THANK YOU