Development of CPT Based Pile Design for Nebraska Soils September - PowerPoint PPT Presentation

Development of CPT Based Pile Design for Nebraska Soils September 18, 2019

Objectives • Conduct literature review of existing CPT pile bearing capacity prediction methods • LTRC study • Compare NDOT CPT data with dynamic load test data from Pile Driving Analyzer • Large dataset • Evaluate CPT prediction methods • Nebraska soil conditions • Implement Nebraska specific end bearing/skin friction capacity factors • CPT-Pile Capacity Software • Advance existing use of CPT in Nebraska • Modernize design testing/design methods

Background-CPT • Cone Penetration Test (CPT) • Conical tipped penetrometer advanced by cylindrical drill rod • Tip resistance ( q c ) • Sleeve friction ( f s ) Friction sleeve • Pore pressure ( u 2 ) • Continuous profile • 1” resolution • Current NDOT CPT application • Site characterization • MSE walls • Slope investigation • Shallow foundations Cone Porous element CPT diagram and cone sizes (Cabal & Robertson, 2010)

CPT

Literature Review • Survey of bearing capacity prediction applications • Louisiana DOT • Abu-Farsakh & Titi (1999) • Eight CPT bearing prediction methods evaluated • Aoki & De Alencar (1975) • Bustamante & Gianeselli (LCPC) (1982) • De Ruiter & Beringen (European) (1979) • Penpile (1978) • Philipponnat (1980) • Prince & Wardle (1982) • Schmertmann (1978) • Tumay & Fakhroo (1982)

Aoki & De Alencar (1975) Pile type Fb Fs Bored 3.5 7.0 • End bearing Franki 2.5 5.0 q Steel 1.75 3.5 q = ca t F b Precast concrete 1.75 3.5 α s (%) Soil type Soil type α s (%) Soil type α s (%) q ca ~ 4D Sand 1.4 Sandy silt 2.2 Sandy clay 2.4 • Skin Friction Silty sand 2.0 Sandy silt with clay 2.8 Sandy clay with silt 2.8 α Silty sand with clay 2.4 Silt 3.0 Silty clay with sand 3.0 = f q cs F s Clayey sand with silt 2.8 Clayey silt with sand 3.0 Silty clay 4.0 Clayey sand 3.0 Clayey silt 3.4 Clay 6.0

Bustamante & Gianeselli (1982) (LCPC method) Factors Nature of soil (MPa) Group I Group II • End bearing K Soft clay and mud <1 0.4 0.5 c q c Moderately compacted clay 1 to 5 0.35 0.45 = q K q Silt and loose sand < 5 0.4 0.5 p c ca Compacted to stiff clay and > 5 0.45 0.55 • Skin Friction compacted silt q Soft chalk < 5 0.2 0.3 = c f α Moderately compacted sand and LCPC 5 to 12 0.4 0.5 gravel Group I : plain bored piles; mud bored piles; micro piles (grouted under low Weathered to fragmented chalk > 5 0.2 0.4 pressure); cased bored piles; hollow auger bored piles; piers; barrettes. Group II : cast screwed piles; driven precast piles; prestressed tubular piles; Compacted to very compact sand and driven cast piles; jacked metal piles; micro piles (small diameter piles grouted > 12 0.3 0.4 under high pressure with diameter < 250 mm); driven grouted piles (low gravel pressure grouting); driven metal piles; driven rammed piles; jacket concrete piles; high pressure grouted piles of large diameter.

LCPC method (1982) Category Category-IA: plain bored piles; mud f α Coefficients, Maximum limit of (MPa) bored piles; hollow auger bored piles; micropiles (grouted under low pressure); I II I II III cast screwed piles; piers; barrettes. q Category-IB: cased bored piles; driven c A B A B A B A B A B cast piles. (MPa) Nature of soil Category-IIA: driven precast piles; Soft clay and mud <5 30 90 90 30 0.015 0.015 0.015 0.015 0.035 prestressed tubular piles; jacket concrete piles. Moderately compact clay 1 to 5 40 80 40 80 0.035 0.035 0.035 0.035 0.08 > 0.12 (0.08) (0.08) (0.08) Category-IIB: driven metal piles; jacked Silt and loose sand < 5 60 150 60 120 0.035 0.035 0.035 0.035 0.08 - metal piles. Compact to stiff clay and compact silt > 5 60 120 60 120 0.035 0.035 0.035 0.035 0.08 > 0.20 Category-IIIA: driven grouted piles; (0.08) (0.08) (0.08) driven rammed piles. Soft chalk < 5 100 120 100 12 0.035 0.035 0.035 0.035 0.08 - Category-IIIB: high pressure grouted Moderately compact sand and gravel piles of large diameter >250 mm; 5 to 12 100 200 100 200 0.08 0.035 0.08 0.08 0.12 > 0.20 micropiles (grouted under high pressure). (0.12) (0.08) (0.12) Weathered to fragmented chalk > 5 60 80 60 80 0.12 0.08 0.12 0.12 0.15 > 0.20 (0.15) (0.12) (0.15) Compact to very compact sand and > 12 150 300 150 200 0.12 0.08 0.12 0.12 0.15 > 0.20 gravel (0.15) (0.12) (0.15)

de Ruiter and Beringen (1979) (European method) Clayey Soils Sandy Soils • End Bearing • End Bearing • See Schmertmann method q = S = c q N S u p c u N k • N k = 15 to 20 (cone factor) • N c = 9 (bearing capacity factor) • Skin Friction • Skin Friction  f ( CPT ) s  q c ( compressio n )  = β f S 300 s u =  f min s q  c ( tension )  400 • β = 1 (NC soils), 0.5 (OC soils)  1 .2 TSF 

Penpile (1978) • End Bearing • Clay = q 0 . 25 q p c • Sand = q 0 . 125 q p c q c = average of 3 cone tip resistances near pile tip • Skin Friction f = s f + 1 . 5 0 . 1 f s

Philipponnat (1980) • End Bearing k Soil type b + q q q = ( A ) ( B ) Gravel 0.35 k q = q ca ca t b ca ca 2 Sand 0.40 Silt 0.45 • Clay 0.50 q ca & q cb are average cone tip resistances over the distance 3B (B = pile diameter) above and below the pile tip respectively B PILE TIP A 3B 3B B

Philipponnat (1980) (cont) • Skin Friction F Soil type s Clay and calcareous clay 50 α s q = f Silt, sandy clay, and clayey sand 60 cs F s Loose sand 100 Medium dense sand 150 Dense sand and gravel 200 α s =1.25 for driven precast concrete pile

Prince & Wardle (1982) • End Bearing q = k q p b c For driven piles, k b =.35 and k b =.30 for jacked piles • Skin Friction f = k s f s For driven piles, k s = .53, for jacked piles, k s = .62 and for bored piles, k s = .49

Schmertmann (1978) • End Bearing + q q = ≤ c 1 c 2 q 15 MPa p 2 Procedure for calculation of qt by (Schmertmann) method

Schmertmann (1978) • Skin Friction • Sandy Soils   8 D y L   = + F K f A ' f A '   s s s s s 8 D   = = y 0 y 8 D • Clayey soils = α F f A s c s s αc, Design curves for pile side friction in clay (Schmertmann 1978) K , Design curves for pile side friction in sand (after Nottingham 1975)

Tumay & Fakhroo (1982) + • End Bearing q q q = + q c 1 c 2 a t 4 2 • Where q c1 = average q c values 4D below the pile tip, q c2 = average minimum q c values 4D below the pile tip, and q a = average minimum values ranging 8D above the pile tip. • Skin Friction f = mf sa F sa = f t − = + 9 f m 0 . 5 9 . 5 e sa L • Where F t = total CPT friction for the length of pile embedment and L = pile length.

Project & Site Selection PN CN SN 34-6(133) 12425 C05501305P S034 31644 • 17 projects, 20 bridges S034 31644 77-2(1025) 11801 S077 09368 • 93 CPT – PDA comparisons 80-2(106) 51459B S080 08295L 80-9(865) 12492 S080 40436 180-9(519) 11347 S180 00205 77-3(128) 22265 S077 11185 75-2(167) 21849e S034 38219 81-2(1035) 42050A S081 08578 80-9(865) 12492 S080 40436 80-9(838) 12465 S080 41341 159-7(106) 12381a S159 01373 85-2(111) 22203 S085 0042 7066(43) 12785 C006602905 80-9(811) 21929 S080 43555 80-9(828) 12455 S080 42094 80-9(801) 21867 S080 44207 15-3(115) 32132 S015 13411 80-9(830) 12457 S080 41856

Data Collection • Driven Pile • HP 10x42, HP12x53, HP14x89 • Steel pipe pile 12.75” O.D. • Square prestressed concrete 12” • CPT logs • Depth and soil type considerations • Bridge information • As-builts • Boring logs • Pile records

Existing Pile Capacity • NDOT LRFD driving equation �� � = 4� � + .5 • S= pile set (in.), E= W*H (ft-kip), � = 0.7 resistance factor • PDA to CAPWAP • End and Skin bearing portions • Typically higher capacity than driving equation

CPT Bearing Capacity Prediction • PN 77-2(1025) Skin Friction Capaciity Axial Pile Capacity End Bearing Capacity Q in [kips] Qs in [kips] Qp in [kips] 0.00 200.00 400.00 600.00 800.00 0.00 200.00 400.00 600.00 800.00 0.00 100.00 200.00 300.00 400.00 0 0 0 Penpile Philipponnat 10 10 10 Prince & Wardle LCPC 20 20 20 Aoki Schmertmann 30 30 30 European Depth in [ft] Depth in [ft] Tumay 40 40 40 Depth in [ft] 50 50 50 60 60 60 70 70 70 80 80 80 90 90 90

Axial Pile Capacity Q in [kips] 0.00 100.00 200.00 300.00 400.00 500.00 600.00 700.00 800.00 0 Penpile Philipponnat 10 Prince & Wardle CPT Bearing Capacity LCPC 20 Aoki Prediction- Total Schmertmann European 30 Axial Capacity Tumay Depth in [ft] 40 50 60 70 80 90

End Bearing Capacity Qp in [kips] 0.00 50.00 100.00 150.00 200.00 250.00 300.00 350.00 400.00 0 Penpile Philipponna t 10 Prince & Wardle LCPC Aoki CPT Bearing Capacity 20 Schmertma nn European Prediction- End Tumay 30 Bearing Capacity Depth in [ft] 40 50 60 70 80 90