8/26/2010 1 THE PRESSUREMETER: THE PRESSUREMETER: SOME CONTRIBUTIONS TO SOME CONTRIBUTIONS TO FOUNDATION ENGINEERING FOUNDATION ENGINEERING Jean Jean-Louis BRIAUD Louis BRIAUD President of ISSMGE President of ISSMGE Jean-Louis Briaud – Texas A&M University President of ISSMGE President of ISSMGE Professor, Texas A&M University, USA Professor, Texas A&M University, USA • TEXAM TEXAM vs vs Menard Pressuremeter Menard Pressuremeter • PMT results PMT results vs vs Other Tests Results Other Tests Results • Shal Shal Found : Scale & Embedment Effect? Found : Scale & Embedment Effect? • Shal Shal. Found.: Scale & Embedment Effect? . Found.: Scale & Embedment Effect? • Shal Shal. Found.: Load . Found.: Load-Settlement Curve Settlement Curve • Deep Found.: Lat. Load, Reference Case Deep Found.: Lat. Load, Reference Case • Deep Found.: Lat. Load, Complex Cases Deep Found.: Lat. Load, Complex Cases Jean-Louis Briaud – Texas A&M University Deep Found.: Lat. Load, Complex Cases Deep Found.: Lat. Load, Complex Cases • Deep Found.: Vert. Load, Downdrag Deep Found.: Vert. Load, Downdrag • Future Work Future Work
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8/26/2010
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THE PRESSUREMETER:THE PRESSUREMETER:
SOME CONTRIBUTIONS TO SOME CONTRIBUTIONS TO FOUNDATION ENGINEERINGFOUNDATION ENGINEERING
JeanJean--Louis BRIAUDLouis BRIAUD
President of ISSMGEPresident of ISSMGE
Jean-Louis Briaud – Texas A&M University
President of ISSMGEPresident of ISSMGE
Professor, Texas A&M University, USAProfessor, Texas A&M University, USA
Elastic SettlementE0 = 30 Mpa, B = 38 m, p = 141 kPa, γ = 0.35
S(t0) = 0.88(1 – 0.352)x141x38/30000 = 138 mm
Long Term Settlements(t)/s(to) = (t/to)n
s(to) = 138 mm, t = 70 yrs, to = 5 min, n = 0.045
Jean-Louis Briaud – Texas A&M University
S(70 years) = 138 (70 x 365 x 24 x 60 / 5) 0.045
S(70 years) = 325 mm
Jean-Louis Briaud – Texas A&M University
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LATERAL LOAD ON PILES : REFERENCE CASE
Jean-Louis Briaud – Texas A&M University
LATERAL LOAD-DEFLECTION CURVE
Jean-Louis Briaud – Texas A&M University
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Jean-Louis Briaud – Texas A&M University
Jean-Louis Briaud – Texas A&M University
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Jean-Louis Briaud – Texas A&M University
ULTIMATE HORIZONTAL LOAD, Hou
Hou = ¾ pl B Dv
pl = limit pressure from PMTB = projected pile widthDv = (π/4) lo with lo = (4EI / K)1/4 for L > 3 loDv = L/3 for L < loE = modulus of pile materialI = moment of inertia of pile
Jean-Louis Briaud – Texas A&M University
I moment of inertia of pileK = 2.3 EoEo = PMT first load modulus of soilL = pile length
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Jean-Louis Briaud – Texas A&M University
HORIZONTAL DISPLACEMENT yo @ Hou/3
y = 2 H / l K for L > 3lyo = 2 Ho / lo K for L > 3lo
yo = 4 Ho / L K for L < lo
Ho = Hou/3 = horizontal load at ground surface
Jean-Louis Briaud – Texas A&M University
K = 2.3 Eo = horizontal modulus (line load/deflection)
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Jean-Louis Briaud – Texas A&M University
INTERACTION DIAGRAM FOR COMBINED HORIZ. LOAD AND OVERTURNING MOMENT
Jean-Louis Briaud – Texas A&M University
ANY COMBINATION OF H AND M ON THE DIAGRAM GIVES THE SAME DEFLECTION
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LATERAL LOAD ON PILES : COMPLEX CASES
Jean-Louis Briaud – Texas A&M University
H (t)/H (t ) = (t/t )-n
LONG TERM LATERAL LOAD
Hou(t)/Hou(to) = (t/to) n
y0(t)/yo(to) = (t/to)n
Jean-Louis Briaud – Texas A&M University
n = 0.01 to 0.03 in sandsn = 0.02 to 0.08 in clays
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ΔR(t)/ΔR(t ) = (t/t )-n
n VALUES FROM PMT TESTS
ΔR(t)/ΔR(to) = (t/to) n
n = -log(ΔR(t)/ΔR(to) / log(t/to)
Jean-Louis Briaud – Texas A&M University
n = 0.01 to 0.03 in sandsn = 0.02 to 0.08 in clays
Jean-Louis Briaud – Texas A&M University
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CYCLIC LATERAL LOAD
yN = y1 N a
a averages 0.1 for clays (one way and two way)
a averages 0 08 for sands under one way loading
Jean-Louis Briaud – Texas A&M University
a averages 0.08 for sands under one way loading
a averages 0 for sands under two way loading
ΔR /ΔR = N a
a FROM PMT TESTS
ΔRN/ΔR1 = N a
a = log (ΔRN/ΔR1) / log N
Jean-Louis Briaud – Texas A&M University
PMT only applicable to one way cyclic loading
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Jean-Louis Briaud – Texas A&M University
Jean-Louis Briaud – Texas A&M University
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Jean-Louis Briaud – Texas A&M University
LATERAL LOAD NEAR A TRENCH
Jean-Louis Briaud – Texas A&M University
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Htrench = λ Hno trench
λ
Jean-Louis Briaud – Texas A&M University
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Acceleration of truck
20Vehicle Acceleration
‐30
‐20
‐10
0
10
Acceleration (g)
‐50
‐40
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40
Time (sec)
Raw acc
50ms
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Impact Force (X ,Y and Z directions)
300
500
50ms Vehicle Force
‐700
‐500
‐300
‐100
100
Force (kN)
‐1500
‐1300
‐1100
‐900
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40
Time (sec)
X‐dir
Y‐dir
Z‐dir
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Full‐scale K‐12 Test and Numerical simulation(LS‐DYNA ) Drucker‐Prager γ= 21 kN/m3, E= 50 MPa, c=20 kPa, φ=40 ˚, ψ=20˚
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3m embedded Single Post in Very Dense SandDrucker‐Prager γ= 22 kN/m3, E= 32 MPa, c= 4 kPa, φ= 40 ˚, ψ= 15˚
THE PREBORING PRESSUREMETERTHE PREBORING PRESSUREMETER
DISADVANTAGESDISADVANTAGES
•• Influence of borehole qualityInfluence of borehole quality
•• Uncontrolled drainageUncontrolled drainage
•• Limited use for slopes and wallsLimited use for slopes and walls
Jean-Louis Briaud – Texas A&M University
Limited use for slopes and wallsLimited use for slopes and walls
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THE PREBORING PRESSUREMETERTHE PREBORING PRESSUREMETER
ADVANTAGESADVANTAGES
CC i ii i• Can be doneCan be done in many soilsin many soils•• Gives in situ stress strain curveGives in situ stress strain curve•• In situ “load test”In situ “load test”•• Inexpensive Inexpensive equipmentequipment•• Quality of test from shapeQuality of test from shape of curveof curve
Jean-Louis Briaud – Texas A&M University
Q y pQ y p•• Laterally loaded pilesLaterally loaded piles•• Shallow foundationsShallow foundations•• End bearing pilesEnd bearing piles