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.
172088 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 - 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.

bearing capacity

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...

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...

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...

Mod-01 Lec-07 Shallow Foundation : Bearing Capacity - II

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

Mod-01 Lec-08 Shallow Foundation : Bearing Capacity - III

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

172088 videos foundNext > 

1271 news items

 
Artemis.bm (blog)
Fri, 21 Nov 2014 08:41:15 -0800

The traditional and non-traditional reinsurance markets would certainly have an appetite to provide risk bearing capacity to the NFIP. A similar process is underway in the UK with Flood Re, which will look to the private markets (including alternative ...
 
Times of India
Thu, 20 Nov 2014 13:45:00 -0800

However, Metrowater officials say quality of the pipes has nothing to do with leaks. "Chennai's soil is mostly clay and the load bearing capacity is always shifting. Even a change in the load bearing capacity beneath a pipeline can result in a leak," a ...

Greenroofs.com

Greenroofs.com
Wed, 19 Nov 2014 12:37:30 -0800

“The judges who reviewed Xero Flor this year praised the submitted ultra-lightweight system as an ideal solution for green roof installations on older buildings where roof load bearing capacity is a limitation. They also commended Xero Flor as the only ...

CleanTechnica

CleanTechnica
Wed, 19 Nov 2014 09:34:38 -0800

Type IX EPS is used under the footings because of its higher load bearing capacity. The roof is made from prefabricated wood trusses and features 12 inches of polyisocyanurate insulation. A self adhering rubberized asphalt membrane installed over the ...

Marine Technology News

Marine Technology News
Thu, 20 Nov 2014 01:57:19 -0800

His paper 'Bearing capacity on sand overlying clay soils,' published in 'Géotechnique' and coauthored with Winthrop Professor Mark J. Cassidy and Winthrop Professor Mark F. Randolph, both of the Center for Offshore Foundation Systems (COFS) at the ...

The Independent

The Independent
Tue, 18 Nov 2014 16:00:43 -0800

As we take in the wild sea views, he stands on the cliff edge and explains the thickness of the rope and the load-bearing capacity of each carabiner: the exact figures are lost to a jitter of nerves, but suffice to say those small metal curls could ...
 
Inquirer.net
Wed, 19 Nov 2014 22:45:00 -0800

Other measures to be adopted by the contractor include: “appropriate plastering to be done on the CHB walls to include field density testing on the soil bearing capacity, compliance with appropriate construction methods and section 705 national ...

GhanaWeb

GhanaWeb
Sun, 16 Nov 2014 23:52:30 -0800

“We intend to use this crane for preparation and completion of the hub -- the crane has crawling equipment which can be moved anywhere provided the bearing capacity of the land can carry it,” he added. He pointed out that the assembling of the crane ...
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