langan dvase pile foundation presentation

Technical Excellence Practical Experience Client Responsiveness

Foundation Design and Construction for our Structural Brethren

Deep Foundation Design Basic Cookbook

A Presentation on Special Foundation Topics to the

Delaware Valley Association of Structural Engineers 4 February 2015


Today’s Presenters

Marc Gallagher, P.E., LEEDAP

Michael Fritzges, P.E.

Senior Principal

New York Office

Project Engineer

Philadelphia Office


Today’s Topics

• Deep Foundations

• Driven Piles – Types

– Benefits - Disadvantages

– Costs

– Equipment

• Drilled Piles – Types

– Benefits - Disadvantages

– Costs

– Equipment


Deep Foundations Introduction

• When do we use deep foundations?

However, we can save 700 lira by not doing borings…..and I don’t think we need piles anyway….


Deep Foundations Introduction

• When do we use deep foundations?

– Soft soils such as marsh/wetlands

– Poor fill in a loose condition

– Liquefiable soils

– High groundwater

– Contamination

– Very high foundation loads

– High loads in limited footprint

– Sensitive adjacent structures (subways)

– Reduce settlement


Types of Deep Foundations

• Driven Piles

– Driven into the ground with impact hammer

• Drilled Elements

– Drilled hole filled with concrete/grout/steel

• Other

– Helical piles

– Rammed piers


Driven Piles

• Basics

• Design theory

• Installation requirements

• Equipment

• Problems in Construction


Driven Piles - Basics

• Pile driving has been around for 1000’s of years

• Pile hammer imparts energy to the pile to drive into

the ground

• Driving into harder material requires more energy

• More energy into the pile yields higher capacity



• Advantages – Relatively inexpensive

• $75-$100/ft for steel/concrete

• $25-$35/ft for timber

– Numerous contractors

– Material readily available

– Equipment fairly standard

– Equipment fairly low-tech



• Disadvantages

– Practically limited to

about 250 to 300 tons with the exception of very large marine applications

– Vibrations

– Noise

– Obstructions



• Timber

• H-Pile

• Pipe Pile

• Taper Piles

• Precast Concrete


Driven Piles – Design Theory

• End bearing

• Side friction

• Combination

• Factor of Safety



tipsideult RRQ

FS

QQ ult

allow



• End bearing

– SPT (limited to 40N)

– Bearing Capacity

tiptiptip AqR *

qfctip NDcNBNq 2

1

B

LNq b

tip **4



• Sand – C=0

– Limited to Df = 10 to 20 * Diameter

• Clay – Last term ~ 0

– Nc = 9

qfctip NDcNBNq 2

1



• Side friction

– Sand

• Normal force & friction coefficient

– Clay

• Depends on the “cohesion” or Su (undrained shear strength)

frictionadhesionf side

perimetersides AfR *



• fs for cohesive reduces to first term

• fs for cohesionless reduces to second term

tan*'verticalsAs kcf

Ca = Adhesion factor relating cohesion to friction along shaft

ks = coefficient of lateral earth pressure (generally 1 to 2)



• Sand

• Rule of Thumb #1 – a 12” pile in dense

sand will give about 1 ton allowable

capacity per foot of embedment

perimeterhorizontaltipqfult AANDQ )tan*()(



• Clay

• Rule of Thumb #2 – Call a geotech for

piles in clay

perimeterAtipult AcAcQ ***9



• Load Transfer

– Load “shed” into soil along shaft

and at tip

– Side friction starts with little

displacement

– End bearing requires significant

displacement but can be up to

50% or more of capacity, even

for “friction” piles



• Group effects

– Acts more like a block than n individual piles

– Reduced capacity • Pgroup ≠ Psingle * n

– Both axial and lateral

– Increased settlement • Sgroup > Ssingle



• Factor of Safety on a design is directly

related to field verification program.


Driven Piles – Installation

Requirements

• Driven to a resistance

• Called the “pile set”

• Referenced as Blows per inch or foot



Requirements

• ENR Formula

– Empirical based on 100 years of pile driving

experience

– Input hammer energy (weight * drop)

– Output required resistance or “set” (s)

01.0

**2

S

HeightWeightQ

DropHammer

allow



Requirements

• Wave Equation Analysis

– WEAP

– Computer analysis based on elastic (spring)

theories

– Input hammer type, pile type, soil properties

– Output a graph showing capacity v blow count

– Indicates estimated pile stresses – CRITICAL

FOR CONTRACTOR!


Driven Piles - Equipment

• Pile driving rig

– Base unit is usually a crane

– Leads hold the pile and hammer

• Fixed

• Hanging

– Hammer


• Hammer Types – Gravity

– Steam

– Diesel

– Hydraulic

• Single Acting

• Double Acting



Driven Piles – Installation Problems


Driven Piles – Installation Problems

• Vibrations

• Obstructions (any)

• Sweep (pipe, tapered, H)

• Dog leg (pipe, tapered, H)

• Crumple (end bearing steel)

• Rupture (pipe, tapered)

• Breaks (timber, concrete)

• Yields (steel)

• Tension cracking (concrete)


Drilled Piles

• Basics

• Design theory

• Installation requirements

• Equipment

• Problems during construction


Drilled Piles - Basics

• Pile is drilled into the ground – not driven

• Very large diameter and very high capacities possible – essentially unlimited


Drilled Piles - Basics • Advantages

– No vibrations – Limited noise – Can penetrate obstructions – Small rigs, limited access/headroom

• Disadvantages – Relatively expensive

• Micro-pile $200-$400/ft • Auger Cast $100-$200/ft • Drilled Shaft/Caissons $500-$2,500/ft

– Limited contractors – Materials can be limited – Equipment is highly specialized – Equipment often high-tech – Can be required to carry “unskilled” union contingent (operator,

mechanic, etc) who are not familiar with drilling



• Micropiles

• Auger cast piles

• Drilled shafts

• Caissons



• Micro-piles (mini-caissons)

– 50 to 500 tons

– 5 to 14 inches

– Casing, grout and reinforcement

– Drill with fluid to flush cuttings

– Pressurized in soil

– Soil or rock socket



• Drilled shafts – 500 to 5,000 tons+

– Very large diameters, up to 12 feet have been drilled

– Very high capacity

– Can be belled at the bottom

– Drilled with slurry to support hole

– Installed with casing

• Temporary or Permanent

– Difficult in glacial and fill areas


Drilled Piles

- Basics

• Drilled

shafts



• Caissons

– Really a drilled shaft into rock

– Large diameters

– Extremely high capacity-10,000 tons highest

to date?

– Casing and/or slurry for support

– Rock socket used for capacity



• Auger cast piles

– 50 tons to 300 tons

– Typically 12 to 30 inches

– Larger diameters more common now

– Fast installation in right environment

– Relatively cheap

– Auger is screwed into the ground, concrete

injected as auger is withdrawn


Drilled Piles – Design Theory

• Who designs drilled piles?

–There is no “I” in Team

• Geotechnical engineer = minimum length and

diameter of the pile, axial reinforcement

• Structural engineer = Pile connection and

verification of axial steel arrangement



• Geotechnical - similar to driven piles – End bearing

– Side friction

– Combination

• Structural – Geotechnical capacity is typically much greater

than driven piles, therefore the structural design is often a limiting factor

– Typical ASD design per building code factors

– Rebar throughout length – “extra” in socket



• Micropiles

– Ignore end bearing because small diameter

– Side friction only

– Gravity grouted

– Pressure grouted

– Typical friction values from published sources

AfP s *



• Friction Values



• Rule of Thumb #3 – “The Mazzo Rule” for dense sands

aves Nf *8.0



• Drilled Shafts – End bearing and Side friction

– Gravity grouted

– FHWA is the main design manual used

– Design is the same as for a driven pile, based on adhesion and friction

Sand

Clay

perimeterhorizontaltipqfult AANDQ )tan*()(

tipsideult RRQ

perimeterAtipult AcAcQ ***9



• Caissons – A drilled shaft in rock

– End bearing and side friction

– Gravity grouted

– Unit side shear and tip resistance based on strength of intact rock samples

• Adjusted for quality of rock mass


Drilled Piles - Equipment

• Micropile rig – External flush

– Duplex

– Reverse

circulation

– Casing

– Tri-cone roller

bit

– Down-the-hole

hammer



• Expanding bit

“Numa” system



• Drilled Shaft

Rig

– Kelly Bar

– Rotary Table

– Augers

– Buckets

– Core Barrels



• Caisson Rig – Cluster drill

– Permanent or temporary casing



• Standard Auger

Cast Piles

– Continuous-flight

hollow-stem auger

– Generates high

volume of spoils



• Drilled

Displacement

– Specialized

drill bit

– Compacts

sidewall as

tool

advanced

– Higher

capacities

– Fewer

cuttings


Drilled Piles – Installation Requirements

• Observations

– Drill pressure

– Speed of penetration

– Cuttings

– Rig reactions

– Grout “take”

– Grout/Concrete Properties

• Video

• Down hole inspection


Drilled Piles – Construction Problems

• Collapse of hole

• Obstructions

• Filter cake on side wall

• Soft bottom

• Disturbance

• Seamy rock

• Unexpected depth increase


Other Miscellaneous Types

• Helical Piles

– Typically for light loads

– Foundation repairs for

small structures

• Rammed Piers

– Drilled hole filled with

aggregate that is then

rammed

– Cheap

– Ground improvement


General Installation Requirements

• Controlled Inspection – Record installation

– Count blows, estimate volumes, watch drill reactions

– Assess damage/problems

• Index Piles – Confirm conditions across site

– Test assumptions

– Calibrate models

• Load Tests – Confirm/Prove capacity


Pile Load Testing

• Load testing required if:

– Design compressive loads are greater than those

specified by Code

– Design load in doubt

– Cast-in-place elements with enlarged base

• At least one load test in each area of uniform soil

conditions


Pile Load Testing

• Load Tests

– ASTM standards (basically same as IBC)

– Apply a test load and hold for period of time • Generally 2x the design load as a minimum (FS=2)

• Generally 24 to 48 hours (creep assessment)

• “Quick” test procedure acceptable in certain circumstances

– Static

– Osterberg Cell (O-cell)

– Statnamic


Pile Load Testing

• Static Load

Test Set Up

– Anchor piles

installed for

reaction


Pile Load Testing

• Static Load

Test Set Up

– Dead weight

for reaction


Pile Load Testing


Pile Load Testing Applied Load vs. Settlement

PILE No. K-10-A

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 25 50 75 100 125 150 175 200 225

Applied Load (tons)

Se

ttle

me

nt

(in

ch

)

Avg. of Dial Gage Settlement

Elastic Comp. (Full Pile Length)

Pile No. K-10-A Tested 2/24-2/25/00

Pile Type: 7-in OD, 0.453" wall Oil Well Casing

Grout Filling: 4,000 psi Reinforcement: #20, #14

Design Load: 95 Tons

Pile Length: ??????

Pile Hammer: N/A - Drilled

Final Driving Resistance: N/A - Drilled

0.496 in.

Elastic Compression

(full load transfer to pile tip)

Measured Pile settlement due to

applied load

160 Ton Design Load

Settlement Approx 0.238 in 0. 469 in.

0.060 in.


Pile Load Testing Applied Load vs. Settlement

PILE No. 294

0.0

0.1

0.2

0.3

0.4

0.5

0 25 50 75 100 125 150

Applied Load (tons)

Sett

lem

en

t (i

nch

)

Avg. of Dial Gage Settlement First Load Cycle

Elastic Comp. (Full Pile Length)

Ave of Dial Gage Reading for Second Load Cycle

Elastic Comp (Load shed along pile within bearing stratum)

Pile No. 294 Tested 7/12-

7/19/00

Pile Type: 14" Butt Diameter, 8" Tip Diameter

Monotube

Concrete Filling: 4000 psi Reinforcement:

None


Pile Length: 42'

0.245 in.

0.133 in.

0.390 in.

Elastic Compression

(full load transfer to pile tip)

Measured Pile settlement due

to first cycle of applied load

70 Ton Design Load

Settlement Approx 0.13 in

Measured Pile settlement due

to second cycle of applied

load

0.055 in.

0.222 in.

Elastic Compression

(load shed along length of

pile embeded in bearing

stratum)


Pile Load Testing Settlement vs. Time for 200% Design Load

PILE No. 294

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.10

100 1000 10000

Time (min)

Se

ttle

me

nt

(in

)

Ave. Incremental Settlement, in

63 hr 111 hr

48 hours0.012 inch/48 hours allowable

settlement as per NYCBC

Section C26-1107.1(e)(2)

0.003 inches

Pile No. 294 Tested 7/12-7/19/00

Pile Type: 14" Butt Diameter, 8" Tip Diameter Monotube

Concrete Filling: 4000 psi Reinforcement: None


Pile Length: 42'

Pile Hammer: Vulcan 08

Final Driving Resistance: 50 blows/12"


Pile Load Testing

• O-Cell Load Test Set Up

• For drilled piles only



O-cell

O-cell


Pile Load Testing

• Statnamic Load

Test Set Up


Pile Load Testing

• Lateral Load Test Set Up


Questions?

Marc Gallagher, PE [email protected]

212-479-5408

Mike Fritzges, PE [email protected]

215-864-0640

Philadelphia – New York – Miami – Washington, DC – San Francisco - Houston

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mailto:[email protected]

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