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Transcript of 14.528 DRILLED DEEP FOUNDATIONS Soil...
Revised 9/2012
14.528 DRILLED DEEP FOUNDATIONSSoil Exploration/Determination of Soil Properties
Slide 1 of 125
REQUIREMENTS FOR ALL SUCCESSFULDEEP FOUNDATION PROJECTS
1st Leg:Design
3rd Leg:Inspection
2nd Leg:Construction
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14.528 DRILLED DEEP FOUNDATIONSSoil Exploration/Determination of Soil Properties
Slide 2 of 125
SELECTED REFERENCES YOU SHOULD HAVE IN YOUR LIBRARY
EPRI EL-6800Manual for Estimating
Soil Properties for Foundation Design
(Kulhawy & Mayne 1991)
Naval Facilities Command (NAVFAC)
Soil Mechanics(DM7.01, 1986)
FHWA Manual on Subsurface
Investigations(NHI-01-031, 2001)
FHWA Evaluation of Soil & Rock Properties(IF-02-034, 2002)
AVAILABLE ON COURSE WEBSITE!
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14.528 DRILLED DEEP FOUNDATIONSSoil Exploration/Determination of Soil Properties
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OBJECTIVES OF SUBSURFACE EXPLORATION
Three (3) General Objectives for Subsurface Exploration:
1. Define Soil and Rock Stratigraphy and Structure within Proposed Construction Zone of Influence.
2. Obtain Groundwater Data.- Level at Time of Testing.- Seasonal Fluctuations.
3. Determine Engineering Properties of Subsurface Materials for Use in Foundation Design.
- Collect samples for laboratory testing.- Determine insitu engineering properties.
Photograph courtesy of www.cmeco.com
Revised 9/2012
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GENERAL SUBSURFACE INVESTIGATION METHODS
METHOD Abbrv. ASTM SAMPLING MAX. DEPTH (ft)
Hand Auger Borings HABD1452-07a
D4700-91(06)Yes Typ. 6 - 8
20 (w/difficulty)
Test/Excavation Pits TP None YesLimits of
equipment(Typ. 20 ft)
Soil Test Borings STBD420-98(03)D1452-07a
D4700-91(06)Yes
~ 300 ft(dependent of
various factors)
Green – Near Surface : Red – Near and Deep
D420-98(2003) Standard Guide to Site Characterization for Engineering, Design, and Construction Purposes
Revised 9/2012
14.528 DRILLED DEEP FOUNDATIONSSoil Exploration/Determination of Soil Properties
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HAND AUGER BORINGS (HAB)
Two Man OperationPhotograph courtesy of
http://cees.ou.edu/ugrad/reu/
Typical HAB Cross-SectionFigure courtesy of
WPC Engineering Inc.
• Requires Manual Labor.
• Typical Depths up to 6 to 8 ft.
• Standard Diameter: 3¼ in(Other Diameters Available).
• Allows for soil samples (disturbed) to be collected for classification and laboratory testing (if desired).
Revised 9/2012
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TEST/EXCAVATION PITS (TP)• Requires Appropriate
Construction Equipment (e.g. backhoe).
• Typical Depths up to 20 ft (limited by equipment).
• Pit size determined by needs.
• Allows for soil samples (disturbed) to be collected for classification and laboratory testing (if desired).
• Allows for greater examination of insitu soils by geotechnical engineers and engineering technicians.
Photographs courtesy of www.ees1.lanl.gov, photos.orr.noaa.gov, & www.kerrville.org
Revised 9/2012
14.528 DRILLED DEEP FOUNDATIONSSoil Exploration/Determination of Soil Properties
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Failing Truck Mounted Rig CME750 All-Terrain Rig
SOIL TEST BORING (STB) RIGS
Photographs courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
14.528 DRILLED DEEP FOUNDATIONSSoil Exploration/Determination of Soil Properties
Slide 8 of 125
MoDOT Track Mounted Rig
SOIL TEST BORING (STB) RIGS
Water Boring from Barge for Bridge Crossing
Wireline Rig for Kaolin MinesMacon, GA
Photographs courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
14.528 DRILLED DEEP FOUNDATIONSSoil Exploration/Determination of Soil Properties
Slide 9 of 125
• Continuous flight augers, added in 5-ft increments.
• Limited to non-caving soils and depths < 30 ft.
• Solid flight augers are removed prior to soil sampling, thus labor-intensive.
• Auger diameters from 4 in to 8 in.
• Front end has finger or fish-tail bit to loosen soil.
• Spoil collects around top of borehole.
SOIL TEST BORINGS (STB)Solid Flight Augers
Solid Auger and Drill BitText & Photographs courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
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SOIL TEST BORINGS (STB)Solid Flight Augers
Photographs courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
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• Continuous hollow flight augers, added in 5 ft increments.
• Hollow stem augers allow soil sampling without removal.
• Act as temporary casing to stabilize borehole.
• Center stem and plug are inserted down the hollow center during boring advance.
• HSA range from about 6 to 12 inch O.D. with 3 to 8 inch I.D.
• HSA generally limited to depths < 100 ft.
• HSA should not be used in loose silts and sands below the GWT.
Truck-Mounted Rig with
Hollow-Stem Augers
SOIL TEST BORINGS (STB)Hollow Stem Augers (HSA)
Text & Photographs courtesy of FHWA NHI Course 132031 Subsurface Investigations
HSA outer and inner assemblywith stepwise
center bit
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• Rotary wash techniques are best for borings extending below GWT.
• Rotary wash can achieve great depths > 300+ ft.
• Drilling bits:– Drag bits for clays– Roller bits for sand
• In rotary wash method, borehole is stabilized using either temporary steel casing or drilling fluid.
• Fluids include water, bentonite or polymer slurry, foam, or Revert that are re-circulated in tub or reservoir at surface.
SOIL TEST BORINGS (STB)Rotary Wash Borings
Truck Rig conducting rotary wash boring
Text & Photographs courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
14.528 DRILLED DEEP FOUNDATIONSSoil Exploration/Determination of Soil Properties
Slide 13 of 125
SOIL TEST BORINGS (STB)Rotary Wash Borings
Schematic(Hvorslev 1948)
Photographs courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
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• Bucket auger drills are used for obtaining large disturbed or undisturbed samples.
• Diameters range from 0.6 m (2 ft) to 1.2 m (4 ft).
• Increment of 0.3 m to 0.6 m depths (1 to 2 feet).
• Good for gravelly soils and cobbles.
• Same rigs used for constructing Drilled Shafts.
Setup of rig for Bucket Auger Boring(ASTM D4700)
SOIL TEST BORINGS (STB)Bucket Auger Borings
Text and Figure courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
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• Disturbed Sampling (Most Common)– Bulk samples (from auger cuttings or TP
excavations).– Bucket samples (borrow pits).– Drive samples (e.g. split-spoon).– Laboratory Tests: Grain size, Atterberg
Limits, Specific Gravity, Organic Content, Hydraulic Conductivity (coarse grained), Shear Strength (coarse grained).
• Partially Undisturbed (ASTM D1587)– Continuous Hydraulic Push.
• Undisturbed Sampling (ASTM D1587)– Push Tubes (e.g. Shelby, Piston, Laval)– Rotary & Push (e.g. Denison, Pitcher)– Block Samples– Laboratory Tests: Consolidation, Hydraulic
Conductivity (cohesive), Shear Strength (cohesive)
SOIL SAMPLING
Text & Photographs courtesy of FHWA NHI Course 132031 Subsurface Investigations
Split Spoon Sampler
Thin Wall Samplers
Revised 9/2012
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UNDISTURBED SAMPLESSampling Disturbance
PhotoelasticityStudies
Radiography (X-rays) of Tubes
Photographs courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
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INSITU TESTING METHODSMETHOD Abbrv. ASTM SAMPLING MAX. DEPTH (ft)
Dynamic ConePenetrometer
DCP D6951-03 Yes(via HAB)
6 – 8 Typ.20 (w/difficulty)
Standard Penetration Test SPT D1586-08a Yes > 300 ft
(dependent on boring method)
Cone Penetration Test CPTD3441-05 D5778-07
No > 300 ft(typically 100 – 150 ft max)
Flat Plate Dilatometer DMT D6635-01 No > 300 ft(typically 100 – 150 ft max)
Pressuremeter PMT D4719-07 Yes (via boring)
> 300 ft(dependent on boring)
Vane Shear Test VST D2573-08 Yes (via Boring)
> 300 ft(dependent on boring)
Green – Near Surface : Red – Near and Deep
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• Labor Intensive (Can be done with one person, better with two).
• Several types in use:- Scala (1956)
- Sowers (Sowers and Hedges, 1966) (Common in Southeast US)
- Dual Mass (Army COE)
• Mainly used for residential construction and pavement subgrade evaluations.
• Conducted in conjunction with HAB’s (therefore, soil samples can be collected).
• Depth limited by soil type. 6 – 8 ft typical, 20 ft maximum (if lucky).
DYNAMIC CONE PENETROMETER (DCP)
Figure courtesy of WPC Engineering Inc.
Revised 9/2012
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INSITU TESTING METHODS
Figure courtesy of FHWA NHI Course 132031Subsurface Investigations
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• Very common test worldwide
• 1902 - Colonel Gow of Raymond Pile Co.
• Split-barrel sample driven in borehole.
• Conducted on 2½ to 5 ft depth intervals.
• ASTM D1586 guidelines
• Drop Hammer (140 lbs falling 30 inches)
• Three increments of 6 inches each; Sum last two increments = “SPT N value" (blows/ft)
• Correlations available with all types of soil engineering properties.
• Disturbed Soil Samples Collected
STANDARD PENETRATION TEST (SPT) (ASTM D1586-08a)
Text courtesy of FHWA NHI Course 132031 Subsurface Investigations
Marking of 6 inch Increments for SPT Test Photograph courtesy of physics.uwstout.edu
Revised 9/2012
14.528 DRILLED DEEP FOUNDATIONSSoil Exploration/Determination of Soil Properties
Slide 21 of 125Figures courtesy of J. David Rogers, Ph.D., P.E., University of Missouri-Rolla & FHWA NHI Course 132031
STANDARD PENETRATION TEST (SPT) (ASTM D1586-08a)
Typical Setup
Split Spoon Dimensions (after ASTM D1586)
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STANDARD PENETRATION TEST (SPT) (ASTM D1586-08a)
Figure courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
14.528 DRILLED DEEP FOUNDATIONSSoil Exploration/Determination of Soil Properties
Slide 23 of 125Figure courtesy of http://www.civil.ubc.ca
STANDARD PENETRATION TEST (SPT) (ASTM D1586-08a)
Revised 9/2012
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STANDARD PENETRATION TEST (SPT)Factors Affecting SPT (after Kulhawy & Mayne, 1990 & Table 8. FHWA IF-02-034 )
Cause Effects Influence on N Value
Inadequate Cleaning of Borehole SPT not made in insitu soil, soil trapped, recovery reduced Increases
Failure to Maintain Adequate Head in Borehole Bottom of borehole may become quick Decreases
Careless Measure of Drop Hammer Energy varies Increases
Hammer Weight Inaccurate Hammer Energy varies Inc. or Dec.
Hammer Strikes Drill Rod Collar Eccentrically Hammer Energy reduced Increases
Lack of Hammer Free (ungreased sleeves, stiff rope, more than 2 turns on cathead, incomplete release of drop, etc.) Hammer Energy reduced Increases
Sampler Driven Above Bottom of Casing Sampler driven in disturbed soil Inc. Greatly
Careless Blow Count Recording Inaccurate Results Inc. or Dec.
Use of Non-Standard Sampler Correlations with Std. Sampler Invalid Inc. or Dec.
Coarse Gravel or Cobbles in soil Sampler becomes clogged or impeded Increases
Use of Bent Drill Rods Inhibited transfer of energy to sampler Increases
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CARE & PRESERVATION OF SOIL SAMPLES• Mark and Log samples upon
retrieval (ID, type, number, depth, recovery, soil, moisture).
• Place jar samples in wood or cardboard box.
• Should be protected from extreme conditions (heat, freezing, drying).
• Sealed to minimize moisture loss• Packed and protected against
excessive vibrations and shock.
Text and Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
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TEST RESULTS(i.e. BORING LOG)
STANDARD PENETRATION TEST (SPT) (ASTM D1586-08a)
Shows the following:
Soil Profile (determined from sampling and boring information) with respect to depth and/or elevation.
Groundwater Table (GWT).
SPT N Values.
Laboratory Test Results (if available).
Boring Log courtesy of WPC Engineering Inc.
ASTM D5434-09 Standard Guide for Field Logging of Subsurface Explorations of Soil and Rock
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• Electronic Steel Probes with 60° Apex Tip• Hydraulic Push at 20 mm/s• No Boring, No Samples, No Cuttings, No
Spoil• Continuous readings of stress, friction,
pressure• With Pore Pressure Measurements (CPTu)• With Shear Wave Measurements (SCPT)
CONE PENETRATION TEST (CPT) (ASTM D5778-07)
Text and Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
14.528 DRILLED DEEP FOUNDATIONSSoil Exploration/Determination of Soil Properties
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CONE PENETRATION TEST (CPT) (ASTM D5778-07)
Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations
Shear Wave Velocity (Vs)
qc
Vs
u2
fs
Penetration Porewater Pressure (U2)
Sleeve Friction (fs)
Cone Tip Resistance (qc)
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CONE PENETRATION TEST (CPT) RIGS
Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations & WPC Engineering Inc.
Revised 9/2012
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0 100 2000
4
8
12
16
20
24
28
32
36
40
44
48
52
56
60
64
68Dep
6.89
0 1 2 0 2 4 6 0 2 4 6
Very s tiff fine grained (9)C la yey s il t to s i l ty c lay (4)
C la ys , c lay to s i lty c lay (3)
C la yey s il t to s i l ty c lay (4)
Sil ty sand to sandy s il t ( 5)
Sil ty sand to sandy s il t ( 5)C la ys , c lay to s i lty c lay (3)
C la ys , c lay to s i lty c lay (3)
Sil ty sand to sandy s il t ( 5)
C la yey s il t to s i l ty c lay (4)C la ys , c lay to s i lty c lay (3)Sil ty sand to sandy s il t ( 5)
C le an sands to s il ty sands (6)
Sil ty sand to sandy s il t ( 5)
C la ys , c lay to s i lty c lay (3)
C la yey s il t to s i l ty c lay (4)
CONE PENETRATION TESTING (CPT) RESULTSqc fs uo, u2 FRSoil Profile
CPT Results courtesy of WPC Engineering Inc.
Revised 9/2012
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CONE PENETRATION TESTING(CPT)
Factors Affecting CPT ResultsFigure 9-2. FHWA NHI Course 132031 Subsurface Investigations
qc
Vs
U2
fs
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• Direct push of stainless steel plate at 20-cm intervals; No borings; no cuttings.
• Introduced by Marchetti (1980).
• 18o angled blade
• Pneumatic inflation of flexible steel membrane using nitrogen gas
• Two pressure readings taken (A and B) within about 1 minute
FLAT PLATE DILATOMETER (DMT) (ASTM D6635-01(2007))
• B
• A
Figures and Text courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
14.528 DRILLED DEEP FOUNDATIONSSoil Exploration/Determination of Soil Properties
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FLAT PLATE DILATOMETER (DMT) (ASTM D6635-01(2007))
Figure courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
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• Calibrations: A, B (positive values)• Readings: contact pressure "A" and
expansion pressure "B" with depth• Corrections for membrane stiffness in air:
p0 = 1.05(A + A) - 0.05(B - B)p1 = B -B
• DMT INDICES:• ID = material index = (p1-po)/(po-uo)• ED = dilatometer modulus = 34.7(p1-po)• KD = horizontal stress index
= (po-uo)/vo’
FLAT PLATE DILATOMETER (DMT) (ASTM D6635-01(2007))
• B
• A
Text courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
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Marchetti Device (ASCE JGE, March 1980; ASTM Geot. Testing J., June 1986)
FLAT PLATE DILATOMETER (DMT) (ASTM D6635-01(2007))Manual Reading System (Standard)
Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
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FLAT PLATE DILATOMETER (DMT) (ASTM D6635-01(2007))Computerized System (Standard)
Figure courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
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FLAT PLATE DILATOMETER (DMT) (ASTM D6635-01(2007))Results – Charleston, SC Project
Soil BehaviorClassification
ED with Depth
Raw Data & Calibrations
DMT Results courtesy of WPC Engineering Inc.
Revised 9/2012
14.528 DRILLED DEEP FOUNDATIONSSoil Exploration/Determination of Soil Properties
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0
2
4
6
8
10
12
14
160 200 400 600 800
Modulus ED (atm)
0
2
4
6
8
10
12
14
16
0 500 1000 1500
Pressure (kPa)
Dep
th (m
eter
s)
PoP1
0
2
4
6
8
10
12
14
16
0 1 10
Material Index ID
Clay Silt
0
2
4
6
8
10
12
14
16
0 5 10 15
Horiz. Index KD
FLAT PLATE DILATOMETER (DMT) (ASTM D6635-01(2007))Results - Piedmont Residuum, Charlotte, NC
DMT Results courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
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Also see Hajduk, E.L., Meng, J., Wright, W.B., and Zur, K.J. (2006). “DilatometerExperience in the Charleston, South Carolina Region”, 2nd International Conference onthe Flat Dilatometer, Washington, D.C.
SPT-CPT-DMT COMPARISON
From Local Project in
Charleston, SC Area (2000)
Revised 9/2012
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PRESSUREMETER TEST (PMT) (ASTM D4719-07)
Figure courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
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0
1
2
3
4
5
0 100 200 300 400 500 600Volume Change (cc)
Pres
sure
(tsf
)
0
1
2
3
4
5
0 10 20 30 40 50 Creep (cc/min)
Pres
sure
(tsf
)
PRESSUREMETER (PMT) (ASTM D4719-07)Results – Utah DOT Project
PMT Results courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
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• Performed at bottom of boring or by direct push placement of device• Four-sided blade pushed into clays and silts to measure following:
suv (peak) = Peak Undrained Strength
suv (remolded) = Remolded Strength (after 10 revolutions)
Sensitivity, St = suv(peak)/suv
(remolded)
VANE SHEAR TEST (VST) (ASTM D2573-08)
Scandinavian Vanes
Pictures and text courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
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VANE SHEAR TEST (VST) (ASTM D2573-08)
Figure courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
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Dutch Vane Equipment, Holland VST in Upstate NY
VANE SHEAR TEST (VST) (ASTM D2573-08)Vane Shear Devices
Pictures courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
14.528 DRILLED DEEP FOUNDATIONSSoil Exploration/Determination of Soil Properties
Slide 45 of 125
0
5
10
15
20
25
30
0 10 20 30 40 50 60 70 80
Vane Strength, suv (kPa)
Dep
th (m
eter
s)
Peak
Remolded
0
5
10
15
20
25
30
0 1 2 3 4 5
Sensitivity, St
Dep
th (m
eter
s)
VANE SHEAR TEST (VST) (ASTM D2573-08)Results - San Francisco Bay Mud, MUNI Metro Station
VST Results courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
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INSITU TEST METHOD ADVANTAGES/DISADVANTAGES
Method Advantages Disadvantages
DCP • Quick• Low cost
• Limited depth range• Limited correlations of DCP values to soil properties.
SPT
• Obtain Sample + Number• Simple & rugged device at low cost• Suitable in many soil types• Can perform in weak rocks• Available throughout the U.S. and worldwide.• Many correlations with soil engineering properties exist
• Obtain Sample + Number• Disturbed sample (index tests only)• Crude number for analysis• Not applicable in soft clays and silts• High variability and uncertainty• Many correlations with soil engineering properties exist
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INSITU TEST METHOD ADVANTAGES/DISADVANTAGES
Method Advantages Disadvantages
CPT
• Fast and continuous profiling of strata.• Economical and productive.• Results not operator-dependent.• Strong theoretical basis for interpretation.• Particularly suited to soft soils.
• High capital investment• Requires skilled operator for field use.• Electronics must be calibrated & protected.• No soil samples.• Unsuited to gravelly soils and cobbles.
DMT
• Simple and Robust Equipment.• Repeatable and Operator-Independent.• Quick and Economical.• Theoretical Derivations for elastic modulus, strength, stress history.
• Difficult to push in dense and hard materials.• Primarily established on correlative relationships.•Needs calibration for local geologies.
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INSITU TEST METHOD ADVANTAGES/DISADVANTAGES
Method Advantages Disadvantages
VST
• Assessment of undrained shear strength of clays.• Simple test and equipment.• Measure inplace sensitivity.• Long history of use in practice, particularly embankments, foundations, & cuts.
• Limited to soft to stiff clays & silts with suv< 200 kPa• Slow & time-consuming• Raw suv needs empirical correction• Can be affected by sand seams and lenses
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• Geophysical Methods
• Geologic Mapping (need qualified geologists)
• Drilling and Coring
• Exploration Test Pits
ROCK EXPLORATION
UML Health and Social Sciences BuildingLowell, MA
June 14, 2011
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ROCK EXPLORATIONDrilling and Coring
Sinkhole in Limestone TerrainOrlando, FL
• STB Refusal– Auger refusal
– SPT refusal (> 50 blows per 1 inch penetration)
• Coring (ASTM D2113)• Noncore Drilling
• Percussive Methods
Text and Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations
ASTM D2113-08 Standard Practice for Rock Core Drilling and Sampling of Rock for Site Investigation
Revised 9/2012
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Air-Tracks Drilling for Dynamite Placement Penobscot, Maine
Photograph courtesy of FHWA NHI Course 132031Subsurface Investigations
ROCK EXPLORATIONPercussive Drilling
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ROCK EXPLORATIONDrilling – Rotary Wash
Tricone, Roller,Plug Bits Roller Bits
Drill Rig
Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
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ROCK EXPLORATIONCoring
• Diamond Bits. Best and hardest, producing high quality core. Fastest cutting rates. Expensive.
• Synthetic Bits. Less expensive. Generally good quality cores.
• Tungsten Carbide Bits. Least expensive. Slower coring rates.
Photograph courtesy of www.ackerdrill.com
Carbide Type Bits
Diamond, Carbide Tungsten, SawtoothDiamond
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• Most rugged, least expensive.
• Consists of head section, core recovery tube, reamer shell, & cutting bit.
• Often used as starter when beginning core operations
ROCK EXPLORATIONCoring – Single Tube Core
Text & Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations
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• Double tube core barrel is the standard. • Outer barrel rotates with cutting bit.• Inner barrel is either fixed or swivel type
(with bearings) that retains core sample.• Core diameters generally range from 21
to 85 mm (0.85 to 3.35 inch).• NX core: standard diameter = 54 mm
(2.15 inches).• ASTM C42: The diameter of cores for
determining f’c in load bearing structural members shall be at least 3.70 in.
ROCK EXPLORATIONCoring – Double Tube Core
Text & Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations
Outer Barrel Assembly
Inner Barrel Assembly
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• Good for obtaining core samples in fractured rock and highly weathered rocks.
• Outer core barrel for initial cut and second barrel to cut finer size. Third barrel to retain cored samples.
• Reduces frictional heat that may damage samples.
ROCK EXPLORATIONCoring – Triple Tube Core
Text & Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
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Slide 57 of 125Text & Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations
• Rotary wash with water, foam, or drilling mud (bentonitic or polymeric slurries).
• Fluids reduce wear on drilling and coring bits by cooling.
• Fluids remove cuttings & rock flour.
• Re-circulate to filter fluids and to minimize impact on environment
ROCK EXPLORATIONCoring – Drilling Fluids Notes
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Slide 58 of 125Text & Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations
• Stabilizes boreholes• Driven casing • Drilled-in casing• Dual wall reverse circulation
method• Use in areas with expected
large losses in drilling fluid• Inner section for sampling• Outer casing maintains fluids
for drilling
ROCK EXPLORATIONCoring – Casing
Drilled-In Dual Wall
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14.528 DRILLED DEEP FOUNDATIONSSoil Exploration/Determination of Soil Properties
Slide 59 of 125Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations
ROCK EXPLORATIONCore Recovery
• Core Runs taken in either 5- or 10-foot sections.
• Log the amount of material recovered.
• Core Recovery is percentage retained.
• RQD (Rock Quality Designation) is a modified core recovery.
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Slide 60 of 125Text & Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations
ROCK EXPLORATIONCore Recovery
• Cores should be stored in either wooden boxes or corrugated cardboard box.
• Box marked with boring number, depth of core run, type core, bit type, core recovery (CR), rock type, RQD, and other notes.
• Core operations should be documented:• Loss of fluid• Drilling rates• Sudden drop in rods• Poor recovery• Loss of core
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Slide 61 of 125Text & Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations
ROCK EXPLORATIONCare & Preservation• Routine: Core boxes
• Special: Plastic sleeves• General: Avoid
exposure to shock and vibration during handling and transport.
• Non-natural fractures may result from excessive movements, temperatures, and exposure to air.
• Store for future reference
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GEOPHYSICAL METHODS – MECHANICAL WAVES
Crosshole Tests (CHT)(FHWA NHI-01-031 Figurer 5-25)
Seismic Refraction (SR)(courtesy of www.enviroscan.com)
Also Available:Downhole Tests (DHT)Spectral Analysis of Surface Waves (SASW)
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Ground Penetrating Radar (GPR)(photographs courtesy of http://www.geomodel.com)
GEOPHYSICAL METHODS – ELECTROMAGNETIC WAVES
Electrical Resistivity (ER) Survey Results(FHWA NHI-01-031 Figurer 5-35)
Other Methods:Magnetometer Surveys (MS)Resistivity Piezocone (RCPTu)
Electromagnetic (EM) Survey(FHWA NHI-01-031 Figurer 5-35)
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ADVANTAGES OF GEOPHYSICSNondestructive and/or non-invasive
Fast and economical testing Theoretical basis for interpretation
Applicable to soils and rocks
DISADVANTAGES OF GEOPHYSICSNo samples or direct physical penetration
Models assumed for interpretationAffected by cemented layers or inclusions.Results influenced by water, clay, & depth.
GEOPHYSICAL METHODS
GPR Results for UST(FHWA NHI-01-031 Figure 5-33)
MS Results for Oil Well Location(FHWA NHI-01-031 Figure 5-37)
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SUBSURFACE EXPLORATION PLANNINGSubsurface Exploration Plan:Function of
- Type and Critical Nature of Structure- Foundation Loads- Topographical Information- Site Geology (Soil and Rock Formations)- Location of Bedrock
• 1.5 m core to confirm• >3 m core required for foundations
on rock- Engineer’s Experience- Project Requirements
Consequences of Poor Subsurface Explorations
(photographs courtesy of NHI 13231)
USACE EM1110-1-1804“There are no hard and fast rules stating the
number and depth of samples for a particular geotechnical investigation.”
ASTM D420-98(2003) Standard Guide to Site Characterization for Engineering, Design, and Construction Purposes
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SUBSURFACE EXPLORATION PLANNINGIBC (2009) Section 1802.4.1The scope of the soil investigation including the number and types ofborings or soundings, the equipment used to drill and sample, the in-situ testing equipment and the laboratory testing program shall bedetermined by a registered design professional.
LET THE ENGINEERDECIDE!
Are Soil Explorations as Costly as the Repair?(Photographs courtesy of http://www.dot.state.co.us/geotech/geotechphotos.cfm)
YOU WILL NEED 1 BORING TO 100 ft TO DETERMINESEISMIC SITE CLASSIFICATION FOR IBC 2009
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The Massachusetts State Building Code
(7th Edition)780 CMR 1802.0 FOUNDATION AND
SOILS INVESTIGATIONS1802.5 Borings, Sampling and
Testing. The scope of the subsurface exploration, including the number and
types of borings, soundings or test pits, the equipment used to drill and sample, the in-situ testing equipment and the laboratory testing program,
shall be determined by a registered design professional.
LET THE ENGINEERDECIDE!
Photograph courtesy of TTU Center for Multidisciplinary Research in Transportation
(www.depts.ttu.edu/techmrtweb)
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SUBSURFACE EXPLORATION PLANNINGIBC (2009) Section 1803.3.1 (8th Edition of MSBC)The scope of the soil investigation including the number and types ofborings or soundings, the equipment used to drill and sample, the in-situ testing equipment and the laboratory testing program shall bedetermined by a registered design professional.
AGAIN,LET THE ENGINEER
DECIDE!
YOU WILL STILL NEED 1 BORING TO 100 ft TO DETERMINESEISMIC SITE CLASSIFICATION FOR IBC 2009
780 CMR (8th MSBC) Section 1803.2 Investigations Required.Exceptions: The building official shall be permitted to waive the requirement for a geotechnical investigation: 1. Where satisfactory data from adjacent areas is available that demonstrates an investigation is not necessary to meet the requirements of this chapter or,2. For unoccupied structures that do not pose a significant risk to public safety in the event of failure; or 3. For structures used for agricultural purposes.
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StructureFHWA
(NHI-01-031)USACE
(Table 2-4 EM1110-1-1804)NAVFAC
(DM7.01)
Min. # Spacing Min. # Spacing Min. # SpacingRigid Frame Structure 1 per 230m² 50 ft spacing
Low-Load Warehouse 4 @ Corners
Isolated Rigid Ftg < 2500ft² 2 @ O.C.
Isolated Rigid Ftg < 10,00ft² 3 around Per.
Houses – Subdivisions 1 per 8000m² 200 to 400 ft
Houses – Individual Lots 1 per lot
Bridge Piers1 (< 30m wide)2 (> 30m wide)
1
Retaining Walls 1 ≤ 60 m
Roads – 2 Lane ≤ 60 m 1 per 150 m @ CL
Roads – Multi Lane 1 per 75 m @ CL
Cuts and Embankments 1 ≤ 60 m
Culverts 1 60 to 120 m
Levees 6 to 12 m high 230 m100 to 200 ft
Levees 12 to 18 m high 150 m
SUBSURFACE TEST LAYOUT GUIDELINES
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SUBSURFACE TEST LAYOUT GUIDELINESSCDOT Geotechnical Design Manual (2010)
Foundation Type Min. Geotechnical Site Investigation ReferenceBridge Pile Foundation Minimum one testing location per bent1 Table 4-1
Bridge Single Foundation – Drilled Shaft Minimum one testing locations per foundation location Table 4-1
Bridge Multiple Foundation – Drilled Shaft2 Minimum two testing locations per bent location Table 4-1
Bridge Shallow Foundation – Founded on Soil Minimum three testing locations per bent location Table 4-1
Bridge Shallow Foundation – Founded on Rock Minimum two testing locations per bent location Table 4-1
Retaining Wall (within 150 of bridge abutment) Minimum one testing location at least every 75 ft Section 4.3.2
Retaining Wall (within 150 of bridge abutment) Minimum one testing location at least every 75 ft Section 4.3.2
Embankments Minimum one testing location at least every 500 ft Section 4.3.3
Cut Excavations Minimum one test locations every 300 ft along cut area Section 4.3.4
Culverts Minimum one testing locations @ each end of culvert and at every 100 ft of new crossline culvert2 Section 4.3.5
Sound Barrier Walls Dependant on shallow or deep foundation used2 Section 4.3.6
Misc. Structures (Light poles, overhead signs) Minimum of one test location per foundation location Section 4.3.7NOTES:
1. Spacing between testing locations may be increased, but shall be approved prior to field operations and shall include justification.Spacing may not exceed 100 ft.
2. See SCDOT Geotechnical Manual for additional details.
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Structure FHWA(NHI-01-031)
USACE(Table 2-4 EM111-1-1804)
Spread FootingsLf ≤ 2B, Min. Depth = 2B Min. Depth = 1½B
(4.5m for houses or to unweathered rock)
Lf ≥ 5B, Min. Depth = 4B
2B < Lf < 5B, Extrapolate
Deep Foundations (Soil)Min. Depth = 6m below
anticipated foundation tip elevation
Min. Depth = 1½B of imaginary footing @ 2/3
expected pile depthDeep Foundations (Rock) Min. Depth = 3m, 3D, or 2Bgroup
below foundation tip
Roadways Min. 2mMin. 3m below finished grade
(0.75m into rock)
Embankments/Culverts Min. 2x Embankment Height Height of Levee
Cuts Min. 5m below cut elevation
SUBSURFACE TEST DEPTH GUIDELINES
NOTE: B = Footing Width
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SUBSURFACE TEST DEPTH GUIDELINESSCDOT Geotechnical Design Manual (2010)
Foundation Type Minimum Depth Reference
Deep FoundationBorings shall extend below the anticipated pile or drilled shaft tip elevation a minimum of 20 ft or a minimum of 4 times the minimum pile group dimension, whichever is deeper.
Section 4.3.1
Bridge Shallow FoundationL ≤ 2B, Minimum test depth = 2BL ≥ 5B, Minimum test depth = 4B2B ≤ L ≤ 5B, Minimum test depth = 3B
Table 4-2
Retaining Walls At least 2X wall height beneath the anticipated bearing elevation or to auger refusal, whichever is shallower. Section 4.3.2
EmbankmentsAt least 2X embankment height beneath the anticipated bearing elevation (i.e. to a depth sufficient to characterize settlement and stability issues) or to auger refusal, whichever is shallower.
Section 4.3.3
Cut Excavations At least 25 feet below the anticipated bottom depth of the cut or to auger refusal, whichever is shallower. Section 4.3.4
CulvertsAt least 2X the embankment height beneath the anticipated bearing elevation or in accordance with the bridge spread footing criteria, whichever is deeper (or auger refusal)
Section 4.3.5
Sound Barrier Walls Dependant on shallow or deep foundation used1 Section 4.3.6
Misc. Structures (Light poles, overhead signs)
Same depth criteria as specified for the bridge test locations for the same type of foundation. Section 4.3.7
NOTES:1. See SCDOT Geotechnical Manual for additional details.
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TEST LOCATION PLAN (EXAMPLE)
Test Location Plan Example(Courtesy of WPC Inc.)
Scale
Shows test locations relative to site
Symbol key differentiates between test types
Project Information
Other Useful Data:- North Arrow- Topographic Information
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SUBSURFACE TEST LAYOUT & DEPTH GUIDELINESOther Guidelines
HUD Directive 4460.1 Rev 2 (1995)Shallow Foundations: 1 boring per 2,500 ft² Deep Foundations: 1 boring per 1,600 ft²
Borings must be at least to the bottom of proposed footings and deep enough to locatebearing strata that will support the proposed structure. When rock is encountered, depth ofdrilling into rock shall be at least 5 feet or enough to establish rock quality regarding voids,fissures and strength, or whether it is a boulder.
Hospital and Office Buildings (Sowers and Sowers, 1970)Boring Depth = 3(Number of Stories)0.7 (for light steel or narrow concrete buildings)Boring Depth = 6(Number of Stories)0.7 (for heavy steel or wide concrete buildings)
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SUBSURFACE TEST LAYOUT & DEPTH GUIDELINESOther Guidelines
ASCE (1972)
1. Determine for planned foundation.
2. Determine 'o with Depth.3. Determine Depth D1 at which =
0.1q (q = applied footing load)4. Determine Depth D2 at which
'o = 0.055. Minimum Depth is the smaller of
D1 and D2.
Figure 10.1. Das FGE (2005)
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From Paul W. Mayne, PhD, P.E., Professor, Civil Engineering, GT
DATA COLLECTION, INTERPRETATION, & ANALYSIS TO GEOTECHNICAL SOLUTIONS FLOW CHART
PRIOR INFORMATION• Reconnaissance• Topography• Geology• Hydrology• Environment
SITE EXPLORATION• Geophysics• Drilling and Coring• Sampling• In-situ Testing
LABORATORY TESTING• Index Properties• Strength• Stiffness/Compressibility• Flow/Permeability
INTERPRETED SOIL PARAMETERS
• Geostatic Stress State• Strength: Drained &
Undrained Cases• Stiffness & Rate Effects• Anisotropy, Dynamic
Response, Rheology
THEORETICAL EVALUATIONS
• Constitutive Models• Numerical Simulation• Analytical Solutions
PRIOR EXPERIENCE
• Statistical Trends• Empirical Correlations
ENGINEERING ANALYSIS
• Judgment• Hand Calculations• Computer Simulations• Chart Solutions• Experience
ANALYTICAL METHODS
• Elastic Theory• Theorem of Plasticity• Limit Equilibrium
GEOTECHNICAL SOLUTION• Safe• Feasible• Economical
NUMERICAL METHODS
• Finite Elements• Boundary Elements• Discrete Elements• Finite Difference
COLOR CODE:Blue: 14.330 & 14.333Red: 14.431
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N
DR = relative densityT = unit weightLI = liquefaction index' = friction anglec' = cohesion intercepteo = void ratioqa = bearing capacityp' = preconsolidationVs = shear waveE' = Young's modulus = dilatancy angleqb = pile end bearingfs = pile skin frictionSAND
cu = undrained strengthT = unit weightIR = rigidity index' = friction angleOCR = overconsolidationK0 = lateral stress stateeo = void ratioVs = shear waveE' = Young's modulusCc = compression indexqb = pile end bearingfs = pile skin frictionk = permeabilityqa = bearing stress
CLAY
STANDARD PENETRATION TEST
Courtesy of FHWA NHI Course 132031 Subsurface Investigations
What Do We Need? How Do We Get It?
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CORRECTIONS TO SPT N VALUENmeasured = Raw SPT Value from Field Test (ASTM D1586-08a)
N60 = Corrected N values corresponding to 60% Energy Efficiency(i.e. The Energy Ratio (ER) = 60% (ASTM D4633-10)
Note: 30% < ER < 100% with average ER = 60% in the U.S.
Factor Term Equipment Variable Correction
Energy Ratio CE = ER/60Donut HammerSafety Hammer
Automatic Hammer
0.5 to 1.00.7 to 1.20.8 to 1.5
Borehole Diameter CB
65 – 155 mm150 mm200 mm
1.001.051.15
Sampling Method CSStandard Sampler
Non-Standard Sampler1.0
1.1 to 1.3
Rod Length CR
3 – 4 m4 – 6 m6 – 10 m> 10 m
0.750.850.951.00
N60 = CECBCSCRNmeasured
For Guidance Only. Actual ER values should be measured per ASTM D4633
SPT CorrectionsFrom Table 9
FHWA IF-02-034
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Data from Robertson, et al. (1983), Courtesy of FHWA NHI Course 132031 Subsurface Investigations
CORRECTIONS TO SPT N VALUEEXAMPLE OF DATA FROM SAME SITE
4
6
8
10
12
14
16
0 10 20 30 40 50
Measured N-values
Dep
th (m
eter
s)
Donut
Safety
Sequence
ER = 34 (energy ratio)
45
40
41
41
39
47
56
5560
5663
63
63
64
69
4
6
8
10
12
14
16
0 10 20 30 40 50
Corrected N60
Dep
th (m
eter
s)
Donut
Safety
Trend
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Courtesy of FHWA NHI Course 132031 Subsurface
Investigations
EQUIVALENT ELASTIC MODULUS
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EQUIVALENT ELASTIC MODULUS WITH STRAIN LEVEL
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NORMALIZED SPT N VALUE (N1)60
(N1)60 = N60 values normalized to 1 atmosphere overburden stress.
(N1)60 = CNN60
Where:CN = (Pa/'vo)n
Pa = Atmospheric Pressure (1 atm = 14.7 psi = 2116 psf = 1.06 tsf)'vo = Insitu Vertical Effective Stressn = 1 (clays) and 0.5 to 0.6 (sands)
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CORRECTIONS TO CPT MEASUREMENTS (WITH U2)
Need to correct tip resistance (qc) for pore
pressure @ U2 location.
qc → qt
U2 = UbPore Pressure
Measurement behind Tip
Porous Element for U2Materials: Sintered Metals, Ceramics, Plastics (disposable)Saturation of Porous Elements: Water, Glycerine, SiliconeProcedures: Vacuum for 24-hours, Pre-Saturated Elements, Prophylactic to maintain fluids
Courtesy of FHWA IF-02-034
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WHAT DO WE NEED FOR GEOTECHNICAL DESIGN?1. Geostratigraphy:
- Layering- Soil Types- Depth to Strata
2. Total and Effective Soil Stresses:- Soil Unit Weight ( or sat = t)- GWT Location (u)
3. Shear Strength:- Effective Friction Angle (')- Effective Cohesion Intercept (c')- Undrained Shear Strength (Su)
4. Stress State:- Maximum Past Pressure (’vm).- Overconsolidation Ratio (OCR)- Coefficient of Earth Pressure at Rest (Ko)
5. Stiffness and Moduli:- Elastic Modulus (E)- Shear Modulus (G)- Compression Index (Cc)
6. Consistency:- Void Ratio (e)- Relative Density (Dr)
7. Flow Parameters:- Coefficient of Permeability (k)- Coefficient of Consolidation (cv, ch)
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INSITU TESTS – APPLICABLE SOIL PROPERTIESSoil Property SPT CPT DMT
Soil Classification USCS Behavior BehaviorGroundwater Table Yes Yes Possible
Effective Friction Angle (') (Sands) Yes Yes YesRelative Density (Dr) (Sands) Yes Yes Yes
Unit Weight () Yes Yes YesUndrained Shear Strength (Su) Possible1 Yes Yes
Maximum Past Pressure ('vm or 'p) Possible1 Yes Yes
Overconsolidation Ratio (OCR) Yes
Shear Wave Velocity (Vs) Yes (SCPTu) Yes (SDMT)
Small Strain Shear Modulus (Gmax) Yes (SCPTu) Yes (SDMT)
Small Strain Young’s Modulus (Emax) Yes (SCPTu) Yes (SDMT)
E (Young’s Modulus) Possible1 Possible1 Yes
Coefficient of At-Rest Earth Pressure (Ko) Yes Yes
IBC Site Classification Yes (N) Yes (Vs, Su) Yes (Su)
NOTES:1. Possible, but not recommended for use.
After Table 10. FHWA IF-02-034
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COEFFICIENT OF VARIATION (V) FOR GEOTECHICAL PROPERTIES AND INSITU TESTS (after Duncan, 2000)
Measured or Interpreted Parameter
V(%)
Unit Weight () 3 to 7
Effective Friction Angle (') 2 to 13
Undrained Shear Strength (Su) 13 to 40
Undrained Shear Ratio (Su/'vo) 5 to 15
SPT N Value 15 to 45
Electric CPT Tip Resistance (qt) 5 to 15
Also see Chapter 8 – Applying Judgment in Selecting Soil and Rock Properties for Design (FHWA IF-02-034).
Coefficient of Variation: A measure of dispersion of a probability distribution.
after Table 52. FHWA IF-02-034
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SOIL BORINGS – DETERMINATION OF SOIL STRATIGRAPHY
Figure 9-1. FHWA NHI Course 132031 Subsurface Investigations
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CONE PENETRATION TEST (CPT)DETERMINATION OF SOIL STRATIGRAPHY
CPT Soil Behavior Classification(Based on qt, FR or Bq)
Figure 9-3. FHWA NHI Course 132031 Subsurface Investigations
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CONE PENETRATION TEST (CPT)DETERMINATION OF SOIL STRATIGRAPHY
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0 100 2000
4
8
12
16
20
24
28
32
36
40
44
48
52
56
60
64
68Dep
6.89
0 1 2 0 2 4 6 0 2 4 6
Very stiff fine grained (9)C la yey s il t to s ilty c lay (4)
C la ys , c lay to s il ty c lay (3)
C la yey s il t to s ilty c lay (4)
Si lty sand to sandy s ilt (5)
Si lty sand to sandy s ilt (5)C la ys , c lay to s il ty c lay (3)
C la ys , c lay to s il ty c lay (3)
Si lty sand to sandy s ilt (5)
C la yey s il t to s ilty c lay (4)C la ys , c lay to s il ty c lay (3)Si lty sand to sandy s ilt (5)
C le an sands to s il ty sands (6)
Si lty sand to sandy s ilt (5)
C la ys , c lay to s il ty c lay (3)
C la yey s il t to s ilty c lay (4)
CONE PENETRATION TESTING (CPT) RESULTSqc fs uo, u2 FRSoil Profile
CPT Results courtesy of WPC Engineering Inc.
LAYER 1
LAYER 2
LAYER 3LAYER 4
LAYER 5
LAYER 6
LAYER 8
LAYER 7
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00
01,upppIIndexMaterial D
p0
p10.1 1 10
Material Index (ID)
0.6 1.8
Clay Silt Sand
FLAT PLATE DILATOMETERDETERMINATION OF SUBSURFACE DATA
Courtesy of FHWA NHI Course 132031 Subsurface Investigations
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FLAT PLATE DILATOMETERDETERMINATION OF SUBSURFACE DATA
Figure 43. FHWA IF-02-034
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SOIL PROFILE (EXAMPLE)
Plan View(Boring Locations)
Soil Profile(Cross-Section)
Figure courtesy of FHWA
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SOIL PROFILE (EXAMPLE)
Boring Location PlanFigure 45. FHWA IF-02-034
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SOIL PROFILE (EXAMPLE)
Figure 46. FHWA IF-02-034
Soil Profile
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Triaxial Database from Frozen Sand Samples
20
25
30
35
40
45
50
55
0 10 20 30 40 50 60Normalized (N1)60
Frict
ion
Ang
le,
' (de
g)
Sand (SP and SP-SM)
Sand Fill (SP to SM)
SM (Piedmont)
H&T (1996)
' = [15.4(N1)60]0.5+20
EFFECTIVE FRICTION ANGLE (') FOR SANDS - SPT
Figure 9-12. FHWA NHI Course 132031 Subsurface Investigations
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0
10
20
30
40
50
60
25 30 35 40 45 50
Effective Friction Angle, ' (deg)
Dep
th (fe
et) SPT-N
Triaxial
EFFECTIVE FRICTION ANGLE (') FOR SANDS - SPTComparison of ' from SPT and Laboratory Tests
Peidmont Residuum (GT Campus) – Silty Sand (SM)
Courtesy FHWA NHI Course 132031 Subsurface Investigations
0
10
20
30
40
50
60
0 10 20 30 40 50
SPT N-values (bpf)
Dep
th (fe
et)
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25
30
35
40
45
50
55
10 100 1000Normalized Tip Stress, qt/vo'
Frict
ion
Ang
le, '
(de
g)
Frankston Sand
Ticino Sand
Edgar Sand
Hokksund Sand
Lone Star Sand
R&C (1983)
' = arctan[0.1 + 0.38 log (qt/vo')]
EFFECTIVE FRICTION ANGLE (') FOR SANDS - CPT
Figure 9-13. FHWA NHI Course 132031 Subsurface Investigations
Revised 9/2012
14.528 DRILLED DEEP FOUNDATIONSSoil Exploration/Determination of Soil Properties
Slide 100 of 125
SOIL SHEAR STRENGTH CORRELATIONSFROM INSITU TESTING
Shear Strength
Parameter
Insitu Testing Method
SPT CPT DMT
Effective Soil Friction
Angle (′)
See Slide 24 arctan[0.1+0.38log(qt/′vo)] 28°+14.6°log(KD)-2.1°log2KD
See Slide 24 Robertson and Campanella(1983)
Marchetti et al. (2001)ISSMGE TC 16 Report
Undrained Shear
Strength (Su)
NO ACCEPTABLE CORRELATIONS
(qt-vo)/Nkt(Nkt = 15 for CHS) 0.22′vo(0.5KD)1.25
Aas et al. (1986) Marchetti et al. (2001)ISSMGE TC 16 Report
NOTES:1. (N1)60 = N60(Pa/′vo)0.5 for sands. Pa = Atmospheric Pressure = 1 bar ≈ 1 tsf.2. ′vo = Insitu Effective Overburden Pressure = Insitu Vertical Effective Stress.3. vo = Total Overburden Pressure = Insitu Vertical Total Stress.
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SOIL SHEAR STRENGTH CORRELATIONSFROM INSITU TESTING
Equation Reference
' = 54° - 27.6034*exp(-0.014(N1)60)
Peck, Hanson, & Thorton (1974) from Kulhawy & Mayne (1990)
' = [20*(N1)60]0.5 + 20°for 3.5 (N1)60 30
Hatanaka & Uchida (1996)
' = 27.1° +0.3*(N1)60 –0.00054(N1)2
60
Peck, Hanson, & Thorton (1974)
from Wolff (1989)
' = [15.4(N1)60]0.5 + 20°Mayne et a. (2001)
based on Hatanaka &
Uchida (1996)
' = [15(N1)60]0.5 + 15°for (N1)60 > 5 and 45°
JRA (1996)
Effective Soil Friction Angle (′) summary from NCHRP Report 651 (2010)
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Slide 102 of 125
after Fang et al. (1991) and EM 1110-1-1905.NOTE: 1 MPa = 10.44 tsf
Soil Density/Consistency N qt(MPa)
t(pcf)
′(°)
SANDS
V. Loose 0-4 0-2 90-105 <30
Loose 5-10 2-5 95-110 30-35
Medium Dense 11-30 5-15 105-120 35-38
Dense 31-50 15-25 115-130 38-41
Very Dense >50 >25 125-140 41-44
COHESIVE SOILS
Very Soft 0-2 0-0.5 90-100
NA
Firm 2-8 0.5-1.5 90-110
Stiff 9-15 1.5-3 105-125
Very Stiff 15-30 3-6 115-135
Hard >30 >6 120-140
SOIL ENGINEERING PROPERTY CORRELATIONSFROM INSITU TESTING (TABLE 1)
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SOIL ENGINEERING PROPERTIES DETERMINATIONMaximum Allowable Shear Strengths (SCDOT, 2010)
Cannot be exceeded with laboratory testingAND
written permission from SCDOT
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SOIL ENGINEERING PROPERTIES DETERMINATIONMaximum Allowable Shear Strengths (SCDOT, 2010)
Cannot be exceeded with laboratory testingAND
written permission from SCDOT
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Slide 105 of 125
EXAMPLE INTERPRETATION –
SPT Given Data
Provided:- Soil Stratigraphy- USCS Classification- Groundwater Table(@ Time of Testing)
- SPT N Values(No Energy Measurements)
- Drilling Method (HSA)- Date Started/Ended
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14.528 DRILLED DEEP FOUNDATIONSSoil Exploration/Determination of Soil Properties
Slide 106 of 125t from Table 1 (Lecture Notes)
EXAMPLE INTERPRETATION – SPTDetermination of Nave, t, and 'vo
0 1000 2000'vo (psf)
25
20
15
10
5
0
Dept
h (f
t)
0
460
9201030
14801565
0 10 20 30B-7 N (bpf)
25
20
15
10
5
0
Dep
th (f
t)
SAND - Silty SANDNave = 17
use t = 115 pcf
Sandy SILTNave = 4
use t = 110 pcf
Clayey SILT (MH)/MARLNave = 4
use t = 115 pcf
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Calculate Nave for sand layer from 0 to 8 ft.
Simple Way:Using Table 1 (Lecture Notes)
Nave = 17, therefore ' ≈ 36°
Formula Way:Use Mayne et al. (2001)
' = [15.4(N1)60]0.5 + 20° and (N1)60 = N60(Pa/'vo)0.5
Use Nave = 17, 'vo,ave = 460 psf, and Pa = 2115 psfTherefore, (N1)60 = 17(2115/460)0.5 = 36
Using equation ' = [15.4(N1)60]0.5 + 20°, ' = 44°
USE ' = 36°
EXAMPLE INTERPRETATION – SPTDetermination of Effective Friction Angle (')
0 10 20 30B-7 N (bpf)
25
20
15
10
5
0
Dep
th (f
t)
SAND - Silty SANDNave = 17
use t = 115 pcf
Sandy SILTNave = 4
use t = 110 pcf
Clayey SILT (MH)/MARLNave = 4
use t = 115 pcf
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qt (tsf) fs (tsf) Uo, U2 (tsf) FRSoil Profile
EXAMPLE INTERPRETATION – CPT Given DataD
epth
(ft)
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Slide 109 of 125
qt (tsf) fs (tsf) Uo, U2 (tsf) FRSoil ProfileEXAMPLE INTERPRETATION – CPT Soil Layers
7ft
Dep
th (f
t)
17ft
GWT @ 9ft
SAND
SANDY SILT
SILTY CLAY(MARL)
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EXAMPLE INTERPRETATION – CPTDetermination of qt,ave, t, and 'vo
0 1000 2000'vo (psf)
25
20
15
10
5
0
Dep
th (f
t)
0
405
8051025
1170
1405
1590
1775
t from Table 1 (Lecture Notes)
0 100 200 300C-7 qt (tsf)
25
20
15
10
5
0
Dep
th (f
t)
SAND - Silty SANDqt,ave 125 tsf
use t = 115 pcf
Sandy SILTqt,ave 22 tsf
use t = 110 pcf
Silty CLAY - CLAYqt,ave 26 tsf
use t = 115 pcf
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EXAMPLE INTERPRETATION – CPTDetermination of Effective Friction Angle (')
Calculate qt,ave for sand layer from 0 to 7 ft
Simple Way:Using Table 1 (Lecture Notes)
qt,ave ≈ 125 tsf ≈ 12 MPatherefore ' ≈ 37°
Formula Way:Using Robertson and Campanella (1983) formula.
' = arctan[0.1+0.38log(qt/ 'vo)]
Use qt,ave ≈ 12 MPa (250000 psf) & 'vo,ave = 405 psf for layer.Using equation, ' = 49°
USE ' ≈ 37°0 100 200 300
C-7 qt (tsf)
25
20
15
10
5
0
Dep
th (f
t)
SAND - Silty SANDqt,ave 125 tsf
use t = 115 pcf
Sandy SILTqt,ave 22 tsf
use t = 110 pcf
Silty CLAY - CLAYqt,ave 26 tsf
use t = 115 pcf
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EXAMPLE INTERPRETATION – CPTDetermination of Undrained Shear Strength (Su)
Calculate qt,ave for Sandy Silt from 7 to 17 ftCalculate qt,ave for Silty Clay from 17 to 24 ft
Formula Way:use Aas et al. (1986)
Su = (qt-vo)/NktNkt = 15 for CHS (Lecture Slides)
Sandy SILT LayerUse qt,ave ≈ 22 tsf & vo,ave = 1355 psfSu = 2850 psf
Silty CLAY LayerUse qt,ave ≈ 26 tsf & vo,ave = 2310 psfSu = 3300 psf0 100 200 300
C-7 qt (tsf)
25
20
15
10
5
0
Dep
th (f
t)
SAND - Silty SANDqt,ave 125 tsf
use t = 115 pcf
Sandy SILTqt,ave 22 tsf
use t = 110 pcf
Silty CLAY - CLAYqt,ave 26 tsf
use t = 115 pcf
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EXAMPLE INTERPRETATION – SPT & CPTComparison of Soil Engineering Properties
SPT CPT
Two Tests ~ 15 ft Apart
Method t(pcf)
'(°)
SPT - Table 1 115 36
SPT - Formula NA 44
CPT - Table 1 115 37
CPT - Formula NA 49
Sand Layer Properties
0 10 20 30B-7 N (bpf)
25
20
15
10
5
0
Dep
th (f
t)
SAND - Silty SANDNave = 17
use t = 115 pcf
Sandy SILTNave = 4
use t = 110 pcf
Clayey SILT (MH)/MARLNave = 4
use t = 115 pcf
0 100 200 300C-7 qt (tsf)
25
20
15
10
5
0
Dept
h (ft
)
SAND - Silty SANDqt,ave 125 tsf
use t = 115 pcf
Sandy SILTqt,ave 22 tsf
use t = 110 pcf
Silty CLAY - CLAYqt,ave 26 tsf
use t = 115 pcf
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INDEX PROPERTIES OF INTACT ROCK• Specific Gravity of Solids (Gs)
• Unit Weight ()• Porosity (n)• Ultrasonic Velocities (Vp and Vs)• Compressive Strength (qu)• Tensile Strength (T0)• Elastic Modulus, ER (at 50% of qu)
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Revised 9/2012
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SPECIFIC GRAVITY OF ROCK MINERALS
0 1 2 3 4 5 6 7 8
Specific Gravity of Solids, Gs
halitegypsum
serpentinequartz
feldsparchloritecalcite
dolomiteolivinebaritepyrite
galena
Speci f i c G rav i t i es of Rock Mi
Reference Value(fresh water)
Common MineralsAverage Gs = 2.70
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Revised 9/2012
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UNIT WEIGHTS OF ROCKS
14
16
18
20
22
24
26
28
0.0 0.1 0.2 0.3 0.4 0.5 0.6
Porosity, n
Satu
rate
d Unit
Weigh
t,
T (kN
/m3 )
Dolostone GraniteGraywacke LimestoneMudstone SiltstoneSandstone Tuff
sat =water [ Gs(1-n) + n]
Gs = 2.80 2.65 2.50
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ULTRASONIC VELOCITIES OF ROCKSSeismic Velocities for Intact Rock Materials
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
Compression Wave, Vp (m/s)
Shea
r W
ave,
Vs (m
/s)
Limestone Chalk Marble SchistTuff Slate Anhydrite GrandioriteDiorite Gabbro Granite DuniteBasalt Dolostone Mudstone Siltstone
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STRENGTH OF INTACT ROCKS
• Compressive Strength, u = qu
• (Direct) Tensile Strength, *T0
• (Indirect) Brazilian Strength, T0
• Shear Strength,
– Across the intact rock
– Along the planar surface (joints)Courtesy of FHWA NHI Course 132031 Subsurface Investigations
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LAB DATA ON INTACT ROCKS (GOODMAN, 1989) qu T0 ER Ratio Ratio
Intact Rock Material (MPa) (MPa) (MPa) (-) qu/T0 ER//qu
Baraboo Quartzite 320.0 11.0 88320 0.11 29.1 276Bedford Limestone 51.0 1.6 28509 0.29 32.3 559Berea Sandstone 73.8 1.2 19262 0.38 63.0 261Cedar City Tonalite 101.5 6.4 19184 0.17 15.9 189Cherokee Marble 66.9 1.8 55795 0.25 37.4 834Dworshak Dam Gneiss 162.0 6.9 53622 0.34 23.5 331Flaming Gorge Shale 35.2 0.2 5526 0.25 167.6 157Hackensack Siltstone 122.7 3.0 29571 0.22 41.5 241John Day Basalt 355.0 14.5 83780 0.29 24.5 236Lockport Dolomite 90.3 3.0 51020 0.34 29.8 565Micaceous Shale 75.2 2.1 11130 0.29 36.3 148Navajo Sandstone 214.0 8.1 39162 0.46 26.3 183Nevada Basalt 148.0 13.1 34928 0.32 11.3 236Nevada Granite 141.1 11.7 73795 0.22 12.1 523Nevada Tuf f 11.3 1.1 3649.9 0.29 10.0 323Oneota Dolomite 86.9 4.4 43885 0.34 19.7 505Palisades Diabase 241.0 11.4 81699 0.28 21.1 339Pikes Peak Granite 226.0 11.9 70512 0.18 19.0 312Quartz Mica Schist 55.2 0.5 20700 0.31 100.4 375Solenhofen Limestone 245.0 4.0 63700 0.29 61.3 260Taconic Marble 62.0 1.2 47926 0.40 53.0 773Tavernalle Limestone 97.9 3.9 55803 0.30 25.0 570
Statistical Results: Mean = 135.5 5.6 44613 0.29 39.1 372.5S.Dev. = 93.7 4.7 25716 0.08 35.6 193.8
Note: 1 MPa = 10.45 tsf = 145.1 psi
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CLASSIFICATION FOR ROCK MATERIAL STRENGTH
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ROCK MASS CLASSIFICATIONS• RQD - Early form of rating rock mass
• Geomechanics System - Rock Mass Rating (RMR) by Bieniawski (1984, 1989)
• Q-System - Norwegian Geotechnical Institute (Barton, et al. 1974)
• Geological Strength Index, GSI (Hoek, et al., 1995)
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Slide 122 of 125Text & Figures courtesy of FHWA NHI Course 132031 Subsurface Investigations
ROCK QUALITY DESCRIPTION(RQD)
• The RQD is a modified core recovery.
• Measure of the degree of fractures, joints, and discontinuities of rock mass
• RQD = sum of pieces > 100 mm (4 inches) divided by total core run.
• Generally performed on NX-size core.
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ROCK MASS RATING (RMR)• RMR based on five parameters:
– Uniaxial strength (qu)– Rock Quality Designation (RQD)– Spacing of Discontinuities– Condition of the Discontinuities– Groundwater Conditions
• RMR = R1+R2+R3+R4+R5
• Adjustment for Joint Orientation relative to construction
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02468
10121416
0 50 100 150 200 250 300
Unconfined Compressive Strength, qu (MPa)
RM
R R
atin
g R
1
0
5
10
15
20
25
0 10 20 30 40 50 60 70 80 90 100Rock Quality Designation, RQD
RM
R R
atin
g R
2
0
5
10
15
20
25
0.01 0.1 1 10Joint Spacing (meters)
RM
R R
atin
g R
3
0
5
10
15
20
25
30
35
0 1 2 3 4 5 6Joint Separation or Gouge Thickness (mm)
RM
R R
atin
g R
4 Slightly Rough Weathered
Slickensided Surface or Gouge-Filled
Soft Gouge-Filled
Rough/Unweathered
ROCK MASS RATING (RMR)Geomechanics Systems (CSIR) [after Bieniawski, 1984, 1989]
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0
2
4
6
8
10
12
14
16
0 0.1 0.2 0.3 0.4 0.5 0.6Joint Water Pressure Ratio, u/1
RM
R R
atin
g R
5
u = joint water pressure1 = major principal stress
Al ter nate 2 Def i ni t
f or P ar ameter R5
0
2
4
6
8
10
12
14
16
1 10 100 1000
Inflow per 10-m Tunnel Length (Liters/min)
RM
R R
atin
g R
5
Al t er nat e 1 Def i ni t i
f or P arameter R5
Dry
Damp
Wet
Dripping
Flowing
ROCK MASS RATING (RMR) also CSIR System 5
Geomechanics System - (Bieniawski, 1984, 1989) RMR = Ri Geomechanics Classification for Rock Masses i = 1 CLASS DESCRIPTION RANGE of RMR
I Very Good Rock 81 to 100 NOTE: Rock Mass Rating is obtained by summing the five index II Good Rock 61 to 80 parameters to obtain an overal rating RMR. Adjustments for dip III Fair Rock 41 to 60 and orientation of discontinuities being favorable or unfavorableIV Poor Rock 21 to 40 for specific cases of tunnels, slopes, & foundations can also beV Very Poor Rock 0 to 20 considered.
ROCK MASS RATING (RMR)Geomechanics Systems (CSIR) [after Bieniawski, 1984, 1989]
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