digplanet beta 1: Athena
Share digplanet:

Agriculture

Applied sciences

Arts

Belief

Business

Chronology

Culture

Education

Environment

Geography

Health

History

Humanities

Language

Law

Life

Mathematics

Nature

People

Politics

Science

Society

Technology

In geotechnical engineering, bearing capacity is the capacity of soil to support the loads applied to the ground. The bearing capacity of soil is the maximum average contact pressure between the foundation and the soil which should not produce shear failure in the soil. Ultimate bearing capacity is the theoretical maximum pressure which can be supported without failure; allowable bearing capacity is the ultimate bearing capacity divided by a factor of safety. Sometimes, on soft soil sites, large settlements may occur under loaded foundations without actual shear failure occurring; in such cases, the allowable bearing capacity is based on the maximum allowable settlement.

There are three modes of failure that limit bearing capacity: general shear failure, local shear failure, and punching shear failure.

Introduction[edit]

A foundation is the part of a structure which transmits the weight of the structure to the ground. All structures constructed on land are supported on foundations. A foundation is, therefore, a connecting link between the structure proper and the ground which supports it.

General shear failure[edit]

The general shear failure case is the one normally analyzed. Prevention against other failure modes is accounted for implicitly in settlement calculations.[1] There are many different methods for computing when this failure will occur.

Terzaghi's Bearing Capacity Theory[edit]

Karl von Terzaghi was the first to present a comprehensive theory for the evaluation of the ultimate bearing capacity of rough shallow foundations. This theory states that a foundation is shallow if its depth is less than or equal to its width.[2] Later investigations, however, have suggested that foundations with a depth, measured from the ground surface, equal to 3 to 4 times their width may be defined as shallow foundations.[2]

Terzaghi developed a method for determining bearing capacity for the general shear failure case in 1943. The equations are given below.

For square foundations:

 q_{ult} = 1.3 c' N_c + \sigma '_{zD} N_q + 0.4 \gamma ' B N_\gamma \

For continuous foundations:

 q_{ult} = c' N_c + \sigma '_{zD} N_q + 0.5 \gamma ' B N_\gamma \

For circular foundations:

 q_{ult} = 1.3 c' N_c + \sigma '_{zD} N_q + 0.3 \gamma ' B N_\gamma \

where

 N_q = \frac{ e ^{ 2 \pi \left( 0.75 - \phi '/360 \right) \tan \phi ' } }{2 \cos ^2 \left( 45 + \phi '/2 \right) }
 N_c = 5.7 \ for φ' = 0
 N_c = \frac{ N_q - 1 }{ \tan \phi '} for φ' > 0
 N_\gamma = \frac{ \tan \phi ' }{2} \left( \frac{ K_{p \gamma} }{ \cos ^2 \phi ' } - 1 \right)
c′ is the effective cohesion.
σzD′ is the vertical effective stress at the depth the foundation is laid.
γ′ is the effective unit weight when saturated or the total unit weight when not fully saturated.
B is the width or the diameter of the foundation.
φ′ is the effective internal angle of friction.
K is obtained graphically. Simplifications have been made to eliminate the need for K. One such was done by Coduto, given below, and it is accurate to within 10%.[1]
 N_\gamma = \frac{ 2 \left( N_q + 1 \right) \tan \phi ' }{1 + 0.4 \sin 4 \phi ' }

For foundations that exhibit the local shear failure mode in soils, Terzaghi suggested the following modifications to the previous equations. The equations are given below.

For square foundations:

 q_{ult} = 0.867 c' N '_c + \sigma '_{zD} N '_q + 0.4 \gamma ' B N '_\gamma \

For continuous foundations:

 q_{ult} = \frac{2}{3} c' N '_c + \sigma '_{zD} N '_q + 0.5 \gamma ' B N '_\gamma \

For circular foundations:

 q_{ult} = 0.867 c' N '_c + \sigma '_{zD} N '_q + 0.3 \gamma ' B N '_\gamma \

 N '_c,  N '_q and  N '_y , the modified bearing capacity factors, can be calculated by using the bearing capacity factors equations(for  N_c, N_q, and N_y, respectively) by replacing the effective internal angle of friction(\phi ') by a value equal to  : tan^{-1}\, (\frac{2}{3} tan \phi ') [2]

Factor of Safety[edit]

Calculating the gross allowable-load bearing capacity of shallow foundations requires the application of a factor of safety(FS) to the gross ultimate bearing capacity, or:

 q_{all} = \frac{q_{ult}}{FS} [2]

Meyerhof's Bearing Capacity theory[edit]

In 1951, Meyerhof published a bearing capacity theory which could be applied to rough shallow and deep foundations.[3] Meyerhof (1951, 1963) proposed a bearing-capacity equation similar to that of Terzaghi's but included a shape factor s-q with the depth term Nq. He also included depth factors and inclination factors. For more information click here.

See also[edit]

References[edit]

  1. ^ a b Coduto, Donald (2001), Foundation Design, Prentice-Hall, ISBN 0-13-589706-8 
  2. ^ a b c d Das, Braja (2007), Principles of Foundation Engineering (6th ed.), Stamford, CT: Cengage Publisher 
  3. ^ {{|publisher=CRC Press LLC|id=|}}

External links[edit]


Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Bearing_capacity — Please support Wikipedia.
This page uses Creative Commons Licensed content from Wikipedia. A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia.
163171 videos foundNext > 

Mod-01 Lec-06 Shallow Foundation : Bearing Capacity - I

Advanced Foundation Engineering by Dr. Kousik Deb,Department of Civil Engineering,IIT Kharagpur.For more details on NPTEL visit http://nptel.ac.in.

bearing Capacity

bearing capacity.

bearing capacity

Geotechnical-Footing Size Using Ultimate Bearing Equation

Footing sizing using the ultimate bearing capacity equation and the factor of safety. Great geotech problem for the PE exam. Check out www.civilengineeringac...

Bearing Capacity - CIVIL 3310 - Auburn University

Mod-01 Lec-09 Bearing Capacity of Foundations II

Foundation for Offshore Structures by Dr. S. Nallayarasu,Department of Ocean Engineering,IIT Madras.For more details on NPTEL visit http://nptel.ac.in.

ANULAB SPT Test at MG Road Agra for Soil Bearing Capacity

The standard penetration test (SPT) is an in-situ dynamic penetration test designed to provide information on the geotechnical engineering properties of soil...

Geotech-Bearing Capacity of Footing

Solving for how good your bearing capacity is when you embed your footing. Great geotechnical PE exam problem. Head to www.civilengineeringacademy.com for mo...

Bearing Capacity of Shallow Foundation Example 2 | Geotechnical Engineering

http://bit.ly/Zs46Ep For more FREE video tutorials covering Bearing Capacity of Shallow Foundations and Soil Mechanics. In this video we demonstrate an examp...

Introduction to Bearing Capacity of Shallow Foundations | Geotechnical Engineering

163171 videos foundNext > 

1219 news items

KTIV

KTIV
Fri, 19 Dec 2014 10:45:00 -0800

In the land domain, they tell me they verified load-bearing capacity for all rooftops that the reindeer will land on. In the maritime domain, they say that Aegis radars are calibrated to track Santa and ships are standing by to conduct any lost gift ...
 
Russia Beyond the Headlines
Sat, 20 Dec 2014 00:26:15 -0800

Even though its designers were limited by factors that required the vehicle to be air-transportable and floatable, they were still capable of increasing its troop-bearing capacity by one and a half times compared to the BTR-D. Now 13 paratroopers can ...

AL.com

AL.com
Fri, 19 Dec 2014 09:03:45 -0800

Pieces can also be suspended above the plaza from the adjacent building, provided it does not exceed the load bearing capacity of the structure. The selected artist will be able to work with the landscape architect to coordinate the placement. The ...

KSN-TV

KSN-TV
Fri, 19 Dec 2014 14:51:29 -0800

The structural issues reduce the load-bearing capacity of the bridge. The bridge, located near Pawnee and Broadway in south Wichita, was originally constructed in 1931. The bridge will be limited to loads less than five, nine and fifteen tons for two ...
 
AviationPros.com
Fri, 19 Dec 2014 07:11:15 -0800

It is required to bring the load bearing capacity of the entire runway to the level that will handle all contemplated types of next generation airtankers as well as the Air National Guard operated C-130J airtankers, all operating at their maximum load ...
 
eNews Park Forest
Fri, 19 Dec 2014 15:03:45 -0800

In the land domain, they tell me they verified load-bearing capacity for all rooftops that the reindeer will land on. In the maritime domain, they say that Aegis radars are calibrated to track Santa and ships are standing by to conduct any lost gift ...
 
Utility Products
Wed, 17 Dec 2014 10:00:00 -0800

In the Gulf Coast region where the soils can be very soft, typical allowable ground bearing capacity (AGBC) are between 1,500 - 2,500 psf. One DICA customer chose specially designed FiberMax crane mats to meet their requirements of reducing heavy loads ...

Alamogordo Daily News

Alamogordo Daily News
Mon, 15 Dec 2014 21:16:41 -0800

It is required to bring the load bearing capacity of the entire runway to the level that will handle all contemplated types of next generation airtankers as well as the Air National Guard operated C-130J airtankers, all operating at their maximum load ...
Loading

Oops, we seem to be having trouble contacting Twitter

Support Wikipedia

A portion of the proceeds from advertising on Digplanet goes to supporting Wikipedia. Please add your support for Wikipedia!

Searchlight Group

Digplanet also receives support from Searchlight Group. Visit Searchlight