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Previous in Forum: How to Cut 2"D X 1W" Wide Channel in Concrete? Next in Forum: Frame Analysis in MS Excel Format
V.Ravi
Bearing Capacity of Soil
Member
02/10/2009 11:47 PM
Join Date: Feb 2009 Posts: 9
A Simple way to find bearing capacity of soil? IS CBR related to Bearing capacity? IS density of the soil related to bearing capacity?
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#4 "Re: Bearing Capacity of Soil" by Anonymous Poster on 02/12/2009 1:25 PM (score 5) Comments rated to be "almost" Good Answers: Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
#3 "Re: Bearing Capacity Of soil---V.Ravi" by omw7 on 02/12/2009 2:40 AM (score 1)
ba/ael
#1
Re: Bearing Capacity Of soil---V.Ravi
Guru
02/11/2009 1:12 AM
Join Date: Nov 2007 Location: Sherwood Park, Alberta, Canada Posts: 1226 Good Answers: 73
(1) Get a soil report. (2) Yes. (3) Yes. __________________ Bruce
V.Ravi Member
02/11/2009 1:18 AM
Join Date: Feb 2009 Posts: 9
The soil has mdd of 1.85t/m3 and CBR of 8.
omw7
#2 In reply to #1
Re: Bearing Capacity Of soil---V.Ravi
#3 In reply to #2
Re: Bearing Capacity Of soil---V.Ravi
Power-User
02/12/2009 2:40 AM
Join Date: Apr 2007 Posts: 272 Good Answers: 18
CBR = 8 gives a medium sand: i.e. not loose nor compact but inbetween the two. You will probably have a bearing capacity of about 150 to 200 kN/m2. You need to ask your soil report provider what the recommended bearing capacioty for design purposes is and, preferably, what are his recommended foundations for the use that you propose. Give him the approximate loads to the foundations (as a sketch is very useful) and the type of loading: static, variable etc. Your CBR is only good for the soil in which it is taken: is this CBR value for the first 2m of soil or is it for the top layer only? __________________ omw7 No more "Almost" Good Answers.
5
Anonymous Poster
#4
Re: Bearing Capacity of Soil 02/12/2009 1:25 PM
To answer your questions in the order they were posed: 1. The CBR is a timed loading test of granular soils for pavement design. It only tests the upper layer, the few inches below the loading piston. It is not used for foundation design. 2. The density of soil is related to its strength and somewhat related to the bearing capacity. The most common way of determining the bearing capacity of the soil is by means of the Standard Penetration Test (SPT)ASTM-D1586, driving a 2" OD x 2 foot long standard split spoon sampler into the soil with an energy equivalent of a 140 lb hammer falling 30 inches, and recording the blows to advance the sampler. Usually it is recorded over the entire 2 foot run and the middle 12 inches recorded as the "N" number. A soil sample for laboratory or field classification is obtained in the sampler at the same time it is advanced. The sampler is emptied after each run of the test, the samples placed into moisture-proof containers, then the sampler is re-assembled, tripped back down the hole and advanced the next 2 foot run. The SPT is performed using a soil boring rig while at the same time advancing a test boring which keeps the hole open to the sampling depths and provides additional information about the subsurface condiitons. The total depth of the sampling depends on the proposed foundation loading, type of structure and site geology. Of particular concern in northern climates are the conditions at 4 to 6 feet below the surface as these depths correspond with the frost depths and typically shallow foundations are constructed at these depths, provided a decent bearing capacity is achieved there. One can go into various bearing capacity charts with the N number and obtain a preliminary value for an allowable bearing capacity. Of special concern is the presence of any weak layers and/or the water table below the planned depth of the foundation, as these will cause a reduction in the allowable bearing capacity. The actual design bearing capacity is dependent on not only the "N" value but the presence of a water table, the soil type, the site geology, the presence of weaker layers, the proposed foundation loadings and the settlement tolerance of the structure. It may be, that considering the type of structure and soil conditions, a shallow foundation type is not ther best choice, then the designer will have to consider an alternative "deep" foundation such as piles or caissons, and these require an entirely different set of subsurface considerations. A considerable amount of engineering judgement goes into the whole bearing capacity process from the depths and types of test borings to the actual determination of the design bearing capacity and ultimate foundation type. Thus, for a structure of any degree of critical importance, it is best to rely on a geotechnical engineer to make these determinations. Dave Sanford, PE Geotechnical Engineer. No more Good Answers. Go to first "Almost" Good Answer
didit
#5
Re: Bearing Capacity of Soil 02/17/2009 7:36 AM
Member
As the basic, we use cohesion and angle of internal friction to determine soil bearing capacity. There are other parameters which can also affect soil bearing capacity, but those 2 parameters are the very basic parameters. And somehow, soil density is related to soil bearing capacity. Join Date: Aug 2007 Location: Indonesia Posts: 6
For CBR, its relation to bearing capacity is already explained by the posts above. It is usually used in pavement design to determine thickness of pavement. The best way to meet your need of soil bearing capacity is with soil test such as the SPT mentioned above. if we may know, what will you do with the bearing capacity? __________________ -- Love of Power vs Power of Love --
Anonymous Poster dave_chandran
#6 In reply to #5
Re: Bearing Capacity of Soil 02/18/2009 3:34 AM
#7
Re: Bearing Capacity of Soil
Member
03/30/2009 4:06 AM
Join Date: Oct 2007 Posts: 7
The bearing capacity can be the ultimate or the safe. The ultimate bearing capacity is computed to find limit of shear strength of soil whereas the safe bearing capacity on dividing with suitable FOS incorporates risk due to settlement. Notwithstanding , settlement analysis is to be carried out (subject to the signihficance of structure) For ultimate bearing capacity calculation, you can use the formula by Terzaghi or the comprehensive one by Brinch Hansen . Any soil mechanic book will have the detail write up. The formula takes into consideration the unit weight ( so directly related to density of the soil , unit weight , = density x 9.81).
Anonymous Poster
#8
Re: Bearing Capacity of Soil 09/15/2010 7:07 AM
A Simple way to find bearing capacity of soil
engr.fawad
#9
Re: Bearing Capacity of Soil
Participant
07/13/2012 7:13 AM
Join Date: Jun 2011 Posts: 2
found this article on soil bearing capacity
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Comments rated to be Good Answers: These comments received enough positive ratings to make them "good answers".
#4 "Re: Bearing Capacity of Soil" by Anonymous Poster on 02/12/2009 1:25 PM (score 5) Comments rated to be "almost" Good Answers: Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
#3 "Re: Bearing Capacity Of soil---V.Ravi" by omw7 on 02/12/2009 2:40 AM (score 1)
Users who posted comments: Anonymous Poster (3); ba/ael (1); dave_chandran (1); didit (1); engr.fawad (1); omw7 (1); V.Ravi (1)
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