2001 Burmister Lecture
Department of Civil Engineering and Engineering Mechanics
Columbia University
 

What is New in Drilled Shaft Foundations?
 

by
 

Prof. Jorj Osterberg

Professor Emeritus
Northwestern University
 

November 7, 2001
2:30 - 3:30 p.m.

Davis Auditorium
Columbia University



 
 
 
 
 
 
 
 
 
 
 
 
 


Abstract
    Rememberances of Donald Burmister. -  The drilled shaft industry has made enormous progress over the past fifty years, advancing from small diameter concrete filled bored holes in soils to depths above the ground water table, to large diameter shafts (up to 20 ft. diameter) and 300 or more feet in depth with reinforcement to the entire depth. The advances were made possible by development of large very high torque drilling machines and introducing methods learned largely from the oil well drilling industry for stabilizing holes below the water table. The new machines can drill sockets in most any hard rock. These developments have made it possible in many cases to substitute one large drilled shaft for many driven piles with a pile cap for less cost.  Unfortunalely, similar progress has not been made in the design of drilled shfts.  Many engineers do not understand the forces acting on the shafts as they are loaded and hence the designs are much too conservative.  Building codes are also much too conservative and gross inconsistencies exist from state to state and city to city. Conventional load tests are expensive and they tie up space and time and are limited in load capacity.  The writer has developed a method of pushing up from or near the bottom using the side shear to resist the force due to end bearing enabeling the determination of separate load-upward movement curves and load-downward movement end bearing curves.  Tests have been made to load capacities up to 17,000 tons.  Also, with the method, loads can be applied for any length of time, can be cycled any number of cycles and can be reapplied over time intervals. A test on a large diameter driven pile has been in progress for three years in which it has been shown that the side shear (commoly called side friction) has more than doubled.  Results of many tests on full scale shafts socketed in rock are discussed. These developments have made it possible to design drilled shafts safely and more economical than in the recent past.


 
Jorj Osterberg has degrees from Columbia, Harvard and Cornell Universities. During his formal education he worked during summers and for short periods for foundation contractors.  His first full time employment was a three year period with the Corps of Engineers at the Waterways Experiment Station in Vicksburg, Mississippi, after which he entered the academic world.  While at Northwestern University, he rose through the ranks to Chair Professor. He designed and built the soils laboratory, and developed the Osterberg Hydraulic Piston Sampler. Since his retirement he has been active in consulting and developing the Osterberg Load Cell method for load testing drilled shafts and driven piles.  He holds 10 patents. 

        Osterberg is a former Chairman of the Soil Mechanics and Foundation Division of the ASCE. He is an Honorary Member of ASCE, and is a member of the National Academy of Engineering.  He delivered the Terzaghi Lecture in 1985, and later received the Terzaghi Award.  He is one of the few surviving founding members of the International Society of Soil Mechanics and Foundation Engineering, and the only survivor two both attended and had a paper in the proceedings of the first International meeting of the Society in 1936 and in the fifteenth meeting this year. He has received the Distinguished Service Award from the Deep Foundations Institute and the Lifetime Achievement Award from the Association of Drilled Shaft Contractors. 

Osterberg, as a student of Professor Burmister, had taken his undergraduate and graduate courses in Soil Mechanics. He did his C.E. degree thesis under Burmister, worked for him in the Soil Mechanics Laboratory, and received his first job through Burmister for a contractor driving piles for the 1938 World's Fair.

Read also the introduction given by Prof. Krizek during the 21st Terzaghi Lecture (from Journal of Geotechnical Engineering, Vol. 115, No. 11, 1989)

Note: Professor Osterberg passed away on May 31, 2008. Born in 1915, he was 93. [6/4/08]

Other links:
 National Academy of Engineering
 Osterberg Cell
 Deep Foundation Institute