THE LEANING TOWER OF PISA

GEOTECHNICAL ENGINEERING

Why Geotechnical Engineering?

“Virtually every structure is supported by soil or rock.

Those that aren’t - either fly, float, or fall over.” -Richard Handy, 1995

Case Study I: Building Foundation

Soft Clay Soil

20 ft of sand and gravel

15-ft soft fill and organic silt

Firm Soil or Bedrock

Weight of building (DL + LL) = 37,000 tons

Initial estimated settlement = 1 ft

Weight of excavated soil = 29,000 tons

Estimated settlement due to the net load of

clay (37,000 – 29,000 = 8,000 tons) = 2-3 in.

75 ft

Source: Lambe & Whitman, 1969

Building 10 on M.I.T.’s Campus – Photo by Professor Zoghi, Sept. 1984

•How deep?

•Size of the footing (mat foundation)?

•Groundwater table?

•Dewatering?

•Braced excavation?

•Damage to adjacent buildings?

•Quantity and rate of the estimated settlement?

•Stress distribution?

•Design bearing capacity?

Design and Construction Issues

•Pile type?

•How deep?

•Spacing?

•Maximum allowable load?

•Pile efficiency?

•Driving/drilling?

•Optimum sequence of driving piles?

•How much variation from vertical?

•Adjacent buildings?

Alternative Foundations

Case Study II: Earth Dam

Source: Lambe & Whitman, 1969 Zoned Earth Dam

• Dimensions? (Most economical design)

• Thickness of the rock facing and gravel to keep swelling of clay core

to a tolerable amount?

• The moisture content and compaction technique (lifts, equipment,

etc) to place gravel and clay?

• Permeability and seepage characteristics of the dam?

• Consolidation and settlement characteristics of underlying soil?

• Shearing strength parameters?

• Potential leakage under and through the dam?

• Factor of safety of upstream and downstream slopes?

• Rapid draw down effect?

• Seismic activity?

Design and Construction Issues

http://www.geol.ucsb.edu/~arthur/Teton%20Dam/welcome_dam.html

TETON DAM

The Teton Dam, 44 miles northeast of Idaho Falls in

southeastern Idaho, failed abruptly on June 5, 1976. It

released nearly 300,000 acre feet of water, then flooded

farmland and towns downstream with the eventual loss

of 14 lives, directly or indirectly, and with a cost

estimated to be nearly $1 billion.

Teton Dam Failure - Flood waters advancing through Rexburg, Idaho.

Landslides

In excess of $1 billion in damages and 25 to 50 deaths each year in U.S.

Loss of Support⇒Bridge Collapse – Kobe EQ

Annual Damage in the U.S.

Geo-Environmental

• Municipal Solid Waste

� Approx. 3.6 lbs trash per

person per day

� Total trash = 216 million

tons

� Make up:

40% Cardboard

18% yard waste

9% metals

8% plastic

others

Landfills

Source: Coduto, 1999

How to Prepare?

HISTORICAL PERSPECTIVE

Geotechnical Hall of Fame:

http://www.ejge.com/People/HallFame.htm

Charles Augustin de Coulomb

• Grandfather of the Soil

Mechanics

• 1736-1806 (France)

• Friction and cohesion

concepts

• Lateral earth pressures on

retaining walls

• Structures, Hydraulics,

Mathematics, Electricity,

etc.

William John Maquorn Rankine

• 1820-1872 (Scotland)

• Thermodynamics and

soil mechanics

• Lateral earth pressure

theory

• Pioneering role as an

engineering educator

Karl von Terzaghi

• The Father of Soil Mechanics

• 1883 (Prague) – 1963 (Massachusetts)

• Coined the phrase…

• First publication in 1925

• Great many contributions

Arthur Casagrande

• 1902 – 1981

• Worked closely with Terzaghi

• Started soil mechanics at Harvard

• Received numerous awards

• Fundamental soil mechanics problems…

Ralph Brazelton Peck

• 1912 – Winnipeg, Canada

• Co-authored a textbook

with Terzaghi

• Initially a bridge

designer…

• Several decades as a

pioneering foundation

engineer and educator

• Numerous awards

Alec Westley Skempton

• 1914-2001 (UK)

• Established soil

mechanics at Imperial

College

• Soil mechanics

problems, rock

mechanics, geology,

and history of civil

engineering

Nilmar Janbu

• 1920 -

• NTNU – Norway

• Ph.D. student of Casagrande at Harvard

• Slope stability problems – Janbu Method

• Landslides in quick- clay

Laurits Bjerrum

• 1918-1973

• The First Director of

NGI (1951-1973)

• Quick clay

• Progressive failure of

slopes

• A “Giant”

Harry Bolten Seed

• 1922 – 1989

• Father of Geotechnical

Earthquake

Engineering

• UC Berkley

• Pioneering work in

Geohazards