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Drilled Shaft Axial Capacity - Makai & Mauka Abutment Analysis Project: Ala Wai Pedestrian Bridge Location: Waikiki, Oahu, Hawaii Project No: 19015 Calculation by: Grant Harrington Date: 2020-06-23

KAI 30% Design Structural Drawing Excerpts: MAKAI

Given (MAKAI):

Drilled Shaft Group (2 total)

D.MAKAI 4 ft * :

shaft diameter

shaft spacing ≥4D = no group effects

s.MAKAI 20.5 ft * :

L.shaft.makai 75 ft * :

(assumed)

KAI 30% Design Structural Drawing Excerpts: MAUKA

Given (MAUKA):

Drilled Shaft Group (6 total)

D.MAUKA 6 ft * :

shaft diameter

shaft spacing ≥4D = no group effects

s.MAUKA 24 ft * :

L.shaft.mauka.B4 100 ft * :

L.shaft.mauka.B5 100 ft * :

30% LOADING PROVIDED BY KAI HAWAII ON 06/17/2020 VIA EMAIL

STRENGTH LIMIT AXIAL LOADING

F.shaft.str.makai F.strength.makai 2 / :

F.strength.makai 510 kip * :

(compression)

F.shaft.str.makai kip 255

F.shaft.str.mauka F.strength.mauka 6 / :

F.strength.mauka 12410 kip * :

(compression)

F.shaft.str.mauka kip 2068

STRENGTH LIMIT LATERAL LOADING

F.strength.lateral.makai 4 kip * :

F.strength.lateral.mauka 90 kip * :

SERVICE LIMIT AXIAL LOADING

F.shaft.serv.makai F.service.makai 2 / :

F.service.makai 270 kip * :

(compression)

F.shaft.serv.makai kip 135

F.shaft.serv.mauka F.service.mauka 6 / :

F.service.mauka 10120 kip * :

(compression)

F.shaft.serv.mauka kip 1687

SERVICE LIMIT LATERAL LOADING

F.service.lateral.makai 6 kip * :

F.service.lateral.mauka 80 kip * :

EXTREME LIMIT AXIAL LOADING

F.shaft.ext.makai 490 kip * :

(compression/tension)

F.shaft.ext.mauka F.extreme.mauka 2 / :

F.extreme.mauka 9180 kip * :

(comp/tension)

F.shaft.ext.mauka kip 4590

EXTREME LIMIT LATERAL LOADING

F.extreme.lateral.makai 220 kip * :

F.extreme.lateral.mauka 510 kip * :

MATERIAL AND SOIL PROPERTIES

Water Table(assume salt water)

γ.sw 64.2 lbf ft 3^/ * :

γ.conc 160 lbf ft 3^/ * :

γ.b γ.conc γ.sw - : lbf ft 3^/ 95.8

w.MAUKA 1 ft * :

w.MAKAI 3 ft * :

(KAI)

Please see Appendix A for Boring Logs and Soil Property Tables for Borings B-2, B-4, & B-5

First Table: Estimated Soil Properties and Lab Testing per Sample

Second Table: Average soil properties per geologic unit and similar density/consistency

Third Table: SHAFT Input Values

See narrative below for explanation of soil parameters presented in Soil Property Tables.

Recorded SPT and MC sampler blow counts were corrected to account for the drill rig hammer energy efficiency and overburden stress using the following equations below. MC blow counts were converted to SPT using the following equation => N(SPT) = 0.55*N(MC). The drill rig used was a Simco 2800 and the hammer efficiency is 83%.

C.N p.a σ'.vo / (0.5^:

Correction Factor

Moisture content (w) and dry density (γd) values based on lab test results. Samples with no lab test data were assigned w & γd values (italicized blue) based on samples with similar blow counts/consistency.

Saturated soil unit weights used in model were determined using Weight-Volume Relationships (Braja Das Textbook):

γ.sat G.s e + (γ.w * 1 e + / :

e G.s γ.w * (γ.d / 1 - :

S w G.s * (e / :

Specific Gravity (Gs) based on lab test results or assumed to be 2.81

Effective Stress Friction Angle and At-Rest Lateral Earth Pressure Coefficient Estimation for Cohesionless Soils (SHAFT INPUT)

Friction angles for cohesionless soils were estimated based on the following Kulhawy and Chen (2007)empirical equation:

Estimated friction angles input in SHAFT were reduced by 20%:

φ'.FS φ' 1.2 / :

At-Rest Lateral Earth Pressure (K0) estimated using the following equations =>

Undrained Shear Strength Estimation for Cohesive Soils (Su - SHAFT INPUT)

Undrained shear strength (Su) for cohesive soils were estimated based on CPT results (B-5) and SPT blow counts (B-2).

SPT Correlation:

f.1 4.5 :

(assumed)

CPT Correlation:

N.k 20 :

(assumed)

Boring B-5: Lean Clay (CL) from 14' to 26' bgs. @ 14' bgs: Su ~ 100 psf @ 24' bgs: Su ~ 3000 psf Average Su = 1600 psf (SHAFT input)

Geotechnical Design for Axial Loading

Assumptions: 1) No base resistance for uplift loading 2) The weight of the drilled shaft is treated as a force effect (negative for uplift and positive for compression loading) rather than a component of resistance and therefore is not subject to a resistance factor 3) Side resistance in uplift is equal to side resistance in compression (with reduction in resistance factor) 4) DUE TO LIQUEFACTION CONCERNS, ASSUME STRESS INFLUENCE ZONE AROUND DRILLED SHAFTS ARE JET GROUTED AND SIDE RESISTANCE IN POTENTIAL LIQUFIABLE ZONES IS NOT IGNORED. IN-SITU SOIL PARAMETERS ARE USED IN ANALYSIS WITHOUT ADJUSTMENT DUE TO GROUT.

List of Design Equations (Cohesionless Soils)

Base Resistance (Cohesionless Soil)

List of Design Equations (Cohesive Soils)

LRFD Limit State Resistance Factors

STRENGTH LIMIT STATE (MAKAI) 2 Shaft Group - (apply 20% reduction)

Side Resistance - Sand (Compression)

φ.str.comp.side.sand.makai 0.55 .8 * :

φ.str.comp.side.sand.makai 0.44

Side Resistance - Sand (Uplift)

φ.str.uplift.side.sand.makai 0.45 .8 * :

φ.str.uplift.side.sand.makai 0.36

Side Resistance - Clay (Compression)

φ.str.comp.side.clay.makai 0.45 .8 * :

φ.str.comp.side.clay.makai 0.36

SERVICE LIMIT STATE (MAKAI)

Side Resistance - Clay (Uplift)

φ.service.makai 1.0 .8 * :

(at 1-inch of settlement)

φ.str.uplift.side.clay.makai 0.35 .8 * :

φ.service.makai 0.8

φ.str.uplift.side.clay.makai 0.28

EXTREME LIMIT STATE (MAKAI)

Tip Resistance - Sand (Compression)

COMPRESSION:

φ.str.comp.tip.sand.makai 0.50 .8 * :

φ.extreme.comp 1.0 .8 * :

φ.extreme.comp 0.8

φ.str.comp.tip.sand.makai 0.4

UPLIFT:

Tip Resistance - Clay (Compression)

φ.extreme.uplift 0.8 .8 * :

φ.extreme.uplift 0.64

φ.str.comp.tip.clay.makai 0.40 .8 * :

φ.str.comp.tip.clay.makai 0.32

STRENGTH LIMIT STATE (MAUKA) - 6 Shaft Group (no reduction in resistance factors)

Side Resistance - Sand (Compression)

Side Resistance - Sand (Uplift)

φ.str.comp.side.sand.mauka 0.55 :

φ.str.uplift.side.sand.mauka 0.45 :

Side Resistance - Clay (Compression)

Side Resistance - Clay (Uplift)

φ.str.comp.side.clay.mauka 0.45 :

φ.str.uplift.side.clay.mauka 0.35 :

Tip Resistance - Sand (Compression)

φ.str.comp.tip.sand.mauka 0.50 :

SERVICE LIMIT STATE (MAUKA):

φ.service.mauka 1.0 :

(at 1-inch of settlement)

EXTREME LIMIT STATE (MAUKA):

COMPRESSION:

φ.ext.mauka.comp 1.0 :

UPLIFT:

φ.ext.mauka.uplift 0.8 :

SHAFT Output Results: MAUKA SIDE (Boring B-2)

D.MAKAI 4 ft * :

L.shaft.makai 75 ft * :

Analysis Method: Ko Method

Unit side resistance limited to 4200 psf for all sand layers------------>

R.sand.ult 2413.74 tonf * :

R.sand.ult kip 4827.5

(per shaft)

Strength Limit Check:

φ.strength.sand R.sand.ult * kip #

F.shaft.sand kip #

OKAY

SAND CONDITION: LOAD-SETTLEMENT CURVE

R.sand.service 2347 tonf * :

(@ 1-inch)

R.sand.service kip 4694

(per shaft)

Service Limit State Check:

φ.service R.sand.service * kip #

F.shaft.sand kip #

OKAY

Extreme Limit State Check: Assume Jet Grout Ground Improvement (no liquefaction)

R.sand.ext 1008.09 tonf * :

R.sand.ext kip 2016.18

(per shaft)

Extreme Limit State Check:

φ.extreme R.sand.ext * kip #

F.shaft.sand kip #

OKAY

SHAFT Output Results: ROCK CONDITION

Analysis Method: Ko Method

D ft #

L.shaft.rock ft #

Strong Basalt Parameters (Skin Friction Only)

ROCK CONDITION: ULTIMATE SIDE FRICTION VS DEPTH

R.rock.ult 3071.21 tonf * :

R.rock.ult kip 6142.42

(per shaft)

Strength Limit Check:

φ.strength.rock R.rock.ult * kip #

F.shaft.rock kip #

OKAY

ROCK CONDITION: LOAD-SETTLEMENT CURVE

R.rock.service 3247 tonf * :

@ 0.33 inch displacement

R.rock.service kip 6494

Service Limit Check:

φ.service R.rock.service * kip #

F.shaft.rock kip #

OKAY

Extreme Limit State Check: Ignore skin resistance within top 130 feet (liquefiable zone)

R.rock.ext 1241.34 tonf * :

R.rock.ext kip 2482.68

(per shaft)

Extreme Limit State Check:

φ.extreme R.rock.ext * kip #

F.shaft.rock kip #

OKAY

Uplift Resistance Example Calculation: Lagoonal Deposits (~20 feet bgs)

γ.sat 109 lbf ft 3^/ * :

N.60 2.2 :

N.1.60 3 :

z.mid 10 ft * :

D 6 ft * :

w.B7 3 ft * :

(bgs)

φ'.FS φ'.1 1.2 / :

φ'.1 27.5 9.2 N.1.60 10 log * + :

φ'.1 32

degrees

φ'.FS 27

degrees

σ'.v1 γ.sat z.mid * (z.mid w.B7 - (γ.sw * - :

σ'.v1 psf 640.6

overburden pressure at middle of Lagoonal Deposits Layer

σ'.p 14.7 psi * (0.15 (* N.60 * :

σ'.p psf 698.544

preconsolidation pressure for gravelly cohesionless soil

OCR σ'.p σ'.v1 / :

OCR 1.0905

K 132 deg * sin - (OCR 32 deg * (^* :

K 0.4934

f.SN1 σ'.v1 K * 27 deg * tan * :

f.SN1 psf 161.0382

R.SN1 π D * 20 * ft * f.SN1 * :

R.SN1 kip 60.7

R.SN1 tonf 30.35

As shown on the right, hand calculated nominal side resistance for Lagoonal Deposits layer is within 5% of the value calculated with SHAFT program

References:

AASHTO LRFD Bridge Design Specifications,8th Edition (2017)

FHWA Drilled Shafts: Construction Procedures and LRFD Design Methods (2010)

SHAFT Technical and User Manuals (2017)