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11/13/2012 PAGE 1 UNCONVENTIONAL SUBSURFACE INVESTIGATION METHODS FOR SOIL TUNNEL/TRENCHLESS PROJECTS Tracy Lyman – Brierley Associates Nate Soule – Brierley Associates CONVENTIONAL SUBSURFACE EXPLORATION METHODS EXAMPLES AND HEARTACHES ALTERNATIVE EXPLORATION METHODS ADVANTAGES AND EXAMPLES INTRODUCTION

UNCONVENTIONAL SUBSURFACE INVESTIGATION METHODS FOR …rmnastt.org/documents/4.3-Unconventionalsubsurfaceinvest-Lyman.pdf · UNCONVENTIONAL SUBSURFACE ... UNCONVENTIONAL EXPLORATION

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11/13/2012

PAGE 1

UNCONVENTIONAL SUBSURFACE INVESTIGATION METHODS FOR SOIL TUNNEL/TRENCHLESS PROJECTS

Tracy Lyman – Brierley AssociatesNate Soule – Brierley Associates

• CONVENTIONAL  SUBSURFACE EXPLORATION METHODS 

• EXAMPLES AND HEARTACHES

• ALTERNATIVE EXPLORATION METHODS

• ADVANTAGES AND EXAMPLES

INTRODUCTION

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• AUGER BORING

• ROTARY WASH BORING

• SPLIT SPOON SAMPLES @ 5 FT (N‐VALUES)

• UNDISTURBED SAMPLES

• CONE PENETROMETER/VANE SHEAR

• LAB TESTING

STANDARDIZED, REPEATABLE, 

WELL‐UNDERSTOOD

CONVENTIONAL METHODS

• BORING SPACING/SCOPE

• 200 ‐500 FT 

• USNCT/T AND INDUSTRY PRACTICE

• LARGE/COMPLEX – 1.5 TO 2.25 % PROJECT COST

• SMALL/ROUTINE – 1 TO 1.5% OF PROJECT COST

CONVENTIONAL METHODS ‐ SCOPE

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• GROUND TYPES

• COARSE GRAVEL, COBBLES, BOULDERS

• ARTIFICIAL FILL/HARD OBSTRUCTIONS

• MIXED FACE

• HIGH GROUNDWATER IN SILT/SILTY SAND

• PROBLEMS

• VERTICAL VARIABILITY

• HARD OBSTRUCTIONS

• LOW PERMEABILITY IN SILT AND SILTY SAND

LIMITATIONS/PROBLEMS

• DENVER 72‐IN STORM DRAIN

• SEATTLE WATER LINE

• DENVER INTERCEPTOR SEWER

PROJECT EXAMPLES/HEARTACHES

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• 300 FT HIGHWAY CROSSING

• SAND/SILTY SAND NEAR CREEK

• AUGER BORINGS AT EACH SHAFT (NO CENTER BORING IN HIGHWAY)

• WHEELED TBM WITH SAND SHELVES PLANNED AND DEWATERING

• CONTRACTOR SHAFT EXCAVATION = THIN SILT AT 2 ‐3 FT INTERVALS

• DEWATERING VERY PROBLEMATIC

• SWITCHED TO MICROTUNNEL = CHANGE ORDER $$

• TEST PITS – BETTER OBSERVATION OF SILT

• CONTINUOUS SAMPLING AT TUNNEL HORIZON

DENVER 72‐IN STORM DRAIN

• LARGE WATERLINE PROJECT

• AUGER BORINGS/SPLIT SPOON 

• GBR USED – SILT, SAND, GRAVEL, OCCASIONAL COBBLES

MANY COBBLES 

VERY HIGH UCS

CONFIRMED  COBBLES WITH

BUCKET AUGER HOLES 

MTBM RESCUE SHAFTS

• TEST PITS /

LARGE DIAMETER BORINGS 

SEATTLE WATERLINE

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• 36 – IN PIPE

• SAND, GRAVEL, WEAK BEDROCK (SILTSTONE, CLAYSTONE, SANDSTONE)

• OPEN SPACE PARK CROSSING

CONTRACTOR ENCOUNTERED LIMESTONE (HIGH UCS)

DESTROYED SOIL CUTTING TOOLS

RESCUE SHAFTS NOT ALLOWED IN OPEN SPACE

OPEN SPACE LIMESTONE – SEISMIC REFRACTION, CORE BORING

GEOPHYSICS TO AUGMENT BORINGS

DENVER INTERCEPTOR SEWER

• TEST PITS

• LARGE DIAMETER BORINGS

• GEOPHYSICS

• PILOT BORE

• VACUUM BORE

UNCONVENTIONAL EXPLORATION METHODS

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• METHOD

• OPEN EXCAVATION

• DEWATERING

• ADVANTAGES

• LARGE “SAMPLE SIZE”

• OBSERVE PIT WALL

• OBSERVE SOIL BEHAVIOR

• DEWATERING VOLUME

• CONTINUOUS SAMPLING

• COST

• $125 ‐ $175/HR BACKHOE OPERATOR/EQUIPMENT

• DEWATERING EXTRA

TEST PITS

• METHOD

• 18 TO 30‐IN AUGER/BUCKET AUGER

• DIRECTLY OBSERVE SOIL 

• CONTINUOUS SAMPLING

• ADVANTAGES

• LARGE “SAMPLE SIZE”

• OBSERVE SOIL BEHAVIOR

• OBSERVE GROUNDWATER 

• COST

• $200 ‐ $250/HR

• LOGISTICAL SUPPORT EXTRA

LARGE DIAMETER BORINGS

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• METHOD

• SEISMIC REFRACTION

• CROSS‐HOLE SEISMIC

• GROUND PENETRATING RADAR

• ELECTRICAL SURVEY

• ADVANTAGES

• FILL IN BETWEEN BORINGS

• MAP BEDROCK SURFACE

• FIND BURIED OBSTRUCTIONS

• COST

• $5,000 TO $7,000/DAY

GEOPHYSICS

• METHOD

• HDD OR PILOT TUBE BORE 

• BORE TUNNEL HORIZON

• ADVANTAGES

• DIRECT OBSERVATION OF TUNNEL HORIZON

• FIND OBSTRUCTIONS

• FIND COBBLES/BOULDERS

• COST

• $500/HR HDD RIG & CREW

PILOT BORE

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• METHOD

• VACUUM EXCAVATION/TRUCK

• LOOK FOR UTILITIES

• LOOK FOR OBSTRUCTIONS

• ADVANTAGES

• DIRECT OBSERVATION OF UTILITY OR OBSTRUCTION

• OBSERVE BORE WALL

• OBSERVE SOIL BEHAVIOR

• COST

• $200/HR VAC TRUCK AND CREW

• DEWATERING EXTRA

VACUUM BORE

• DENVER URBAN DRAINAGE STORM DRAIN

• FORT COLLINS STORM DRAIN

• DENVER WATER STORM DRAIN

CASE EXAMPLES

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DENVER URBAN DRAINAGE

Proposed 48” Steel Pipe4 to 17-ft Deep to Invert240-ft Long

48” Storm Sewer

Parallel with Tunnel

8” WaterlineInterfered with Tunneling PitNeeded to be Raised

Restricted AccessCDOT Access LinesCDOT Barrier LinesFHWA PermitFRICO Ditch RoadPrivate Property to the West

Cobbles & Boulders

Groundwater

Test Pits

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HDD TRIAL BORE

GUIDED RAMMING OR MICROTUNNELING?

• VERY LOW COVER/BELOW DIVIDED HIGHWAY

• SAND, SILT, GRAVEL BELOW GROUNDWATER

• SOME C0BBLES

QUESTION: GUIDED RAMMING OR MICROTUNNELING??

USE TEST PITS AND HDD BORE

• COBBLES AND GROUNDWATER/DEWATERING

• FEASIBILITY OF PILOT TUBE PUSH

DENVER URBAN DRAINAGE ‐ SUMMARY

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FORT COLLINS STORM DRAIN

RAISED VERTICAL ALIGNMENT

TEST PITS:

CONFIRMED HIGH GROUNDWATER

CONFIRMED FLOWING GROUND

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PILOT TUBE MICROTUNNEL  ‐GUIDE RAILS

DENVER WATER STORM DRAIN

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Back in the day – 1800’s

Another view from 1916 on the other side of the tracks. Note the bridge and the pipe foundation

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Vacuum Exploration

CONCRETE BRIDGE ABUTMENT

WIRE ROPE/DEBRIS

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DIFFICULT!

PIPE RAMMING BEST CHANCE OF SUCCESS

AVOID KNOWN CONCRETE OBSTRUCTIONS

SUMMARY

TRADITIONAL EXPLORATIONS – STANDARDIZED, REPEATABLE, WELL‐UNDERSTOOD

OTHER METHODS PROVIDE: DIRECT OBSERVATION OF SOIL/SOIL BEHAVIOR

LARGER SAMPLE SIZE

COBBLES, BOULDERS, OBSTRUCTIONS

CONSIDER ALL OPTIONS – PROJECT SUCCESS

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THANK YOU

Tracy Lyman110 16th St., Suite 700Denver, CO 80202Tel: 303‐534‐1100

Email: [email protected]