Dynamic Testing Applications for driven piles using Pile Driving Analyzer & CAPWAP

Transcription

1 Dynamic Testing Applications for driven piles using Pile Driving Analyzer & CAPWAP by Garland Likins Pile Dynamics, Inc. Cleveland, OH, USA 2013, Pile Dynamics, Inc. Load Testing. Static Load Testing ASTM D1143 Deadload Testing React. Piles/Anchors Static Load Tests are the standard Costly: Need 100% load + long time Pile structural integrity must be adequate Static Analysis Methods are not accurate 3 SLT International Prediction Event Behaviour of Bored, CFA, and Driven Piles in Residual Soil, ISC 2 Experimental Site, 2003, by Viana da Fonseca and Santos This is WHY we test 3

2 CAPWAP - Results SLT +20% -20% CAPWAP 4 Likins, Rausche, Correlation of CAPWAP with Static Load Tests. Proc. 7th Int l Conf. on Application of Stresswave Theory to Piles: Malaysia Testing reduces uncertainty in capacity Static testing Dynamic Testing Wave Equation Dynamic Formula Static Analysis testing no testing Better verification methods, and more testing, results in lower S.F. and therefore less cost. 8

3 Design Concepts - Factors of Safety Allowable Stress Concept Q d < R u / F.S. σ < σ a ; σ a = σ y /F.S. Load and Resistance Factor Design (LRFD) φ R u > f D L D + f L L L + f i L i + φ σy > (1/A){f D L D + f L L L + f i L i + } AASHTO FACTORS of SAFETY (15th Ed. 1992) code for bridges R u (F.S.) Q d F.S. =3.50 Subsurface+ Static Analysis+Dyn Formula = 2.75 Ss +SA +Wave Equation = 2.25 Ss +SA +WE + Dyn. Testing (CAPWAP) = 2.00 Ss +SA +WE + Static Load Test = 1.90 Ss +SA +WE + Dyn.Test +SLT AASHTO American Association of State Highway and Transportation Officials AASHTO standard PDCA specifications LRFD R u Application: (F.S.) Q d 2000 ton column load, 200 ton ultimate capacity piles design load piles F.S. per pile needed /3.50 = 57.1 t 35 dyn. formula /2.75 = 72.7 t 28 wave equation /2.25 = 88.9 t 23 dynamic test /2.00 = 100 t 20 Static (SLT) /1.90 = t 19 SLT + dynamic lower F.S. fewer piles less cost

4 AASHTO ( LRFD PDCA 2010) LRFD D L look at D/L = 3 D = 1500: L = x x 1.75 = 2750 Application: 2000 ton column load 2750 ton factored load 200 ton ult capacity piles ( nominal resistance ) factored resistance piles phi per pile needed *0.40 = 80 t 35 Gates formula *0.50 = 100 t 28 wave equation *0.65 = 130 t 22 2%, 2# dynamic *0.70 = 140 t 20 ODOT dynamic *0.75 = 150 t 19 SLT or 100% dyn *0.80 = 160 t 18 SLT and 2%,# dyn AASHTO Comparison ASD vs LRFD # piles in example ASD LRFD Gates Wave Equation Dynamic testing Static testing % Dyn testing x 19 Static + Dynamic AASHTO Example continued 2750 ton (27,000 kn) factored load Choose 20 piles: 450 mm sq PSC each pile : 1350 kn Factored Resistance PHI φ R ult,req Q i f Li /φ EB 5,000 kpa Req d Rshaft 50 kpa Req. L pen kn kn kn m Static Test 100% DLT Dyn. Test 2% Wave Equation Static Formula $ $$$

5 Application: PDCA LRFD Eurocode 2000 ton column load, 200 ton ult capacity piles design load piles A1 case GF (SF ) per pile needed 1.35D + 1.5L /2.17 = 92.2 t 22 #2 dyn (D/L =3) /2.23 = 89.7 t 23 #1 SLT /2.04 = 98 t 21 #5 dyn /2.07 = 98 t 21 #2 SLT /1.96 = 102 t 20 #10 dyn /1.92 = 104 t 20 #3 SLT /1.93 = 104 t 20 #15 dyn /1.77 = 113 t 18 #4 SLT /1.90 = t 19 #20 dyn /1.60 = 125 t 16 #5 SLT Standards Australia AS2159 (2009) Assess weighted Average Risk Rating (ARR) 1. Geological complexity (site uniformity) [weight factor 2] 2. Extent of ground investigation [2] 3. Amount / quality of geotechnical data (lab, CPT, SPT) [2] 4. Foundation experience in similar site conditions [1] 5. Method to assess geotechnical parameters for design [2] 6. Design method [1] 7. Method to use in situ test data and installation data [2] 8. Level of construction control [2] 9. Performance monitoring after construction [0.5] Australia has used LRFD since 1995 moderate risk Australia AS2159 F.S.=LF/PHI

6 Australia AS2159 PDCA 2009 LRFD D + 1.5L look at D/L = 3 D = 1500: L = x x 1.5 = 2550 Application: 2000 ton column load 2550 ton factored load 200 ton ult capacity piles ( nominal resistance ) factored resistance piles phi per pile needed *0.65 = 130 t 20 Static 0.5% *0.69 = 138 t 19 Static 1% *0.75 = 150 t 17 Static 2% *0.65 = 130 t 20 dynamic 1% *0.69 = 138 t 19 dynamic 2% *0.77 = 154 t 17 dynamic 10% Number of piles required for example case AASHTO ASD AASHTO LRFD Dynamic formula Eurocode Australia AS 2159 Wave equation Dynamic test Max (2# or 2%) 22 Dynamic test 100% ODOT 20 2# % 19 or 20 (high or low redundancy) Static test to 16 1# to 5# Dynamic test and Static test % dyn 1 static 19 or 20 (1%) (high or low redundancy) 18 to 20 (2%) (high or low redundancy) LRDF (Load & Resistance Factor Design) φ Ru > f D L D + f L L L + f i L i + LRFD - Different Loading Factors ACI, AISC 1.2D + 1.6L AASHTO 1.25D L Eurocode 1.35D + 1.5L Australia 1.20D + 1.5L need different phi factors ( φ ) for same equivalent F.S.

7 Pile Costs: $2.5M / $123.6 M = 2% Test / driven pile cost Year Drilled Shaft Driven Pile Total 2005 $9,438,000 $10,705,041 $20,143, $10,728,331 $18,836,927 $29,565, $11,193,633 $15,948,151 $27,141, $9,669,093 $26,591,945 $36,261, $7,470,894 $25,308,605 $32,779, $9,064,681 $26,211,622 $35,276,304 Total $57,564,633 $123,602,290 $181,166,923 Test Costs: Year Dynamic Static Total 2005 $290,421 $15,500 $305,921 Peter Narsavage 2006 $273,315 $40,000 $313,315 Ohio Dept of Transportation 2007 $379,750 $379, PDCA DICEP program, 2008 $528,076 $59,806 $587,882 Orlando 2009 $380,863 $70,000 $450, $483,557 $35,000 $518,557 Total $2,335,982 $220,306 $2,556,288 Pile Costs: $2.5M / $123.6 M = 2% Test / driven pile cost Test Costs: Year Drilled Shaft Driven Pile Total 2005 $9,438,000 $10,705,041 $20,143, $10,728,331 $18,836,927 $29,565, $11,193,633 $15,948,151 $27,141, $9,669,093 $26,591,945 $36,261, $7,470,894 $25,308,605 $32,779,499 Method 2010 $9,064,681 AASHTO PHI $26,211,622 Relative cost $35,276,304 Savings Total $57,564,633 $123,602,290 of piles$181,166,923 Formula (Gates) % GRLWEAP Year Dynamic 0.5 Static 0.80 Total 20% % PDA $290, $15, $305,921 38% 2006 $273,315 $40,000 $313,315 2 # PDA Ohio DOT $379, % $379, %PDA 2008 or SLT $528, $59, $587,882 47% PDA SLT $380, $70, $450,863 50% 2010 $483,557 $35,000 $518,557 Total $2,335,982 $220,306 $2,556,288 Dynamic Pile Monitoring For each blow determine Capacity at time of testing Pile integrity Pile stresses Hammer performance Last three items detect or prevent problems for driven piles

8 Most Sites Have Set-up (defined as capacity gain with time) Caused by reduced effective stresses in soil during pile driving (temporary) Pore pressure effects - clay Arching (lateral motions) - sand Soil structure (e.g. chemical bonds) Cookie cutters Measure it by Dynamic Tests on Both End of Drive and Restrike North Section Intermodal Transit System Guideway Orlando International Airport Boring 8 final plan Original Design Load 100 T for 24 pipe at 120 ft depth Design/Build Proposal: save$ 18 pipe, shorter depth Ref: Wayne Waters, Ed Waters & sons, PDCA Winter Roundtable, Orlando 2004 Proving the point. Proof test > 250 tons Bent #9 Req. Cap. = 250 tons EOD PDA = 135 tons (9 bl/ft) 5 day BOR = 256 tons (64 b/ft) 303 piles - 10% tested by restrike use set-up $1 million saved vs original design

9 St. John s River Bridge test program Aug 11, 1999 Sept x 0.5 inch c.e.pipe, ICE 120S 152 twice the Energy ST Johns River Bridge PDA test program $650,000 extra soil borings $750,000 increased loads by 33% with substantially shorter piles (set-up considered) Total project (6 bridges): $130 million (estimate) $110 million (actual) $20 million (savings) Ref: Scales & Wolcott, FDOT, presentation at PDCA Roundtable Orlando 2004 caution In rare cases, the pile can lose capacity with time

10 Identifying Soil Relaxation from Dynamic Testing Morgano & White, GRL Engineers Ohio Turnpike (I80) Piles drive in clayey silt (N=30) to weathered siltstone/shale (N=50/1 ) Pre-Construction Wave Equation Analysis suggests: 20 blows per inch (1.3 mm set) at 9.3 ft (2.8m) stroke at 300 tons Pile No. Test Date Blow Count (Blows/inch) Transfer Energy (Kip-ft) Hammer Stroke (ft) Case Method Capacity (tons) Test Type 13 2/15/ EOID 2/16/ BOR1 2/16/ EOR1 2/23/ BOR2 2/23/ EOR2 18 2/23/ BOR1 2/23/ EOR Notes: 1. Pile 13 drove additional 5 inches during restrike sequences 2. Pile 18 drove additional 18 inches during restrike sequences Testing detected capacity problem. Prevented potentially major problem on major project 198 tons Capacity Static test on Undisturbed sister pile

11 Soils with relaxation potential Weathered bedrock formations Weathered shale is most susceptible Rule of thumb: more weathered bedrock = more relaxation Seeping water effectively softens bedrock surface High normal force after driving plastically creeps away with time; reduces friction Rock fracturing from driving adjacent piles Saturated dense to v.dense sands & sandy silts Due to negative pore water pressure during driving increases effective stresses of end bearing Pore water pressure equalizes after wait causing reduced soil strength # Meters of driven piles in Sweden reduced due to higher loads per pile PDA Have doubled design loads on same piles! Ref: Carl-John Gravare, Innovations in Scandinavia DFI2000NYC, Proceedings of 25 th Annual Meeting DFI, Oct 2000 For best dynamic test capacity results allow strength changes with time ( dynamic test during restrike ) set-up results in Lower capacity at EOD; shorter piles, or More capacity per pile; fewer piles Less cost for foundation must fail the soil to activate all resistance ( dynamic test: > 2.5 mm set per blow )

12 Dynamic Pile Monitoring For each blow determine Capacity at time of testing Pile integrity Pile stresses Hammer performance Last three items detect or prevent problems for driven piles SPT energy calibration ASTM D4633 Dynamic testing for Offshore oil projects began in 1970 s

13 Caspian Sea 2009 Caspian Sea 2009 Dynamic Testing of cast-in-situ piles need large drop weight To obtain permanent set approx 2% or more of ultimate capacity prepare pile top excavate or build up pile top top transducer flat top protected by cushion attach sensors analysis method (CAPWAP)

14 Mexico, PDA test on a slurry panel using a diesel hammer PDA 4 strain sensors Traditional F = ma Top transducer Force Pile Velocity F V Accelerometer Strain / Force TOP TRANSDUCER F A

15 11 ton hammer mechanical free release by cable pull Slovenia Germany 6 ton weight drop mechanism: Simple hook Up to 25T hammer system Bahrain

16 Malaysia 20 to 30 ton drop weight 75 ton drop weight Japan 40 ton drop weight as shown. Can be up to 85 tons GRL 40 ton APPLE 2.1m shaft, 750 mm drop hydraulic release Activated over 4000 tons 80 ton unit under construction

17 April 2004 Consequences of no redundancy, site variability, and only minimal testing, caused disastrous sudden failure. TAMPA Tribune Nov 23, 2004 Almost half of the foundations supporting the new elevated portion of the Lee Roy Selmon Expressway need major repairs, and the cost of fixing them has grown to $78 million. (eventual total cost was $120 M) Advantages of dynamic testing More information faster and at lower cost Supplement or replace static tests Optimize foundation design Capacity & distribution from CAPWAP 40 years experience; large database Detect bad hammers Know driving stresses (compression-tension) Develop better installation procedures Detect pile damage Lowers risk of foundation failures Lower overall foundation costs