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15 comments
Anonymous Poster

field test to find bearing capacity of soil

05/07/2008 9:56 AM

there are many test can be done to find bearing capacity of a soil. is any one know about a field method for finding out bearing capacity approximately.

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Guru

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#1

Re: field test to find bearing capacity of soil

05/07/2008 6:38 PM

Hmm interesting, I have never had to evaluate bearing directly in the field since at most project sites where bearing capacity may be an issue the more limiting issue is settlement. For what application do you need to determine the bearing capacity. Some code books have established guidelines for acceptable maximum bearing capacities for soils based on soil types, though these may be conservative. Load testing is usually conducted to assess settlement and foundation support. Bearing capacity can be estimated by cone penetrometer testing. Also, standard penetration testing can be used to estimate bearing capacity. The are many correlations to bearing capacity established for such field tests. Though testing would be dependant upon the facility loads on the foundation.

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#2

Re: field test to find bearing capacity of soil

05/07/2008 8:36 PM

You can use the Pennsylvania method. We build an interstate highway on it and, if the highway sinks, we say "Hah, the load was too high!" (And, if you think I forgot the emoticon, I didn't. They really do that.)

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#3
In reply to #2

Re: field test to find bearing capacity of soil

05/09/2008 11:35 AM

Most be a Western PA practice.

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John J Baker
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#8
In reply to #3

Re: field test to find bearing capacity of soil

05/09/2008 12:20 PM

It is. You can see a real difference in road construction somewhere near Blue Mountain. But it balances out - we get bad roads, you get the Iggles.

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#4

Re: field test to find bearing capacity of soil

05/09/2008 11:39 AM

You could always do a nuke test.

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John J Baker
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#6
In reply to #4

Re: field test to find bearing capacity of soil

05/09/2008 12:08 PM

While Nuclear testing is something they could do, it would not tell them anything about bearing strength. "Nuke" tests are to measure in-place density of a soil mass, and moisture content.

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#5

Re: field test to find bearing capacity of soil

05/09/2008 11:46 AM

guest,

To measure compressive strength of in-situ soil, there is a simple, handheld device known as a pocket penetrometer. It operates by pushing a 0.25" dia. loading piston into the material being measured to a set depth (a calibration groove machined on the piston, 0.25" from the end). The compressive strength in tons per sq. ft. or kg per sq. cm. is obtained by noting the position of a sliding indicating ring on the penetrometer's engraved scale.

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#7
In reply to #5

Re: field test to find bearing capacity of soil

05/09/2008 12:14 PM

Hand penetrometers could be used, you would need good correlation tables to soil bearing capacity, and because of the relative size of the samples effectively tested, you'd want a lot of tests for numerous depth intervals and locations. By far the my preference is for CPT, as it has very strong correlations due to a huge amount of data collected, and SPT is the industry standard by which all else is compared so it is always a good choice.

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#9
In reply to #7

Re: field test to find bearing capacity of soil

05/09/2008 12:49 PM

RCE,

I agree, a static cone penetrometer will provide superior information, but at a significantly higher (> > 10x) cost than that of a simple pocket penetrometer. And the pocket penetrometer is hard to beat for portability, as it's about the size of a felt-tip marker.

With respect to "industry standard", I think it depends upon what "industry" you are referring to. In their safety and health regulations for construction (specifically those governing excavations), US-OSHA describes acceptable visual and manual tests for use in classifying soils [29 CFR 1926 Subpart P, App. A, (2), (iv)] - According to this citation: "Estimates of unconfined compressive strength of soils can be obtained by use of a pocket penetrometer or by using a hand-operated shearvane".

(This is the field in which I have the most experience with determining soil characteristics, for excavation safety, using shields, hydraulic and/or timber shoring for trenches, sloping and benching.)

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#10
In reply to #9

Re: field test to find bearing capacity of soil

05/12/2008 3:01 PM

I would guess that since his post was regarding the bearing capacity of soil, the project involves a foundation, and the industry would fall under geotechnical engineering and foundation construction.

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#11
In reply to #10

Re: field test to find bearing capacity of soil

05/12/2008 4:08 PM

RCE,

For foundation construction and / or geotechnical engineering, I would hope that someone would use a method more precise than either type of handheld penetrometer...

Typically, here in the northeast USA at least, whenever geotechnical information is required, a Standard Penetration Test (SPT), pursuant to ASTM method D1586 is run.

Using a 140 lb. (64 kg) driving mass falling free from a height of 30 in. (762 mm), a 2" diameter thick-walled sample tube (aka split spoon sampler) is driven into the ground, with someone "sitting on the borehole" recording the "blow count" for each 6" of sample tube penetration. I've overseen this type of borehole installation, using both hollow stem auger drill rigs, and "Geoprobes" as well.

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Guru

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#12
In reply to #11

Re: field test to find bearing capacity of soil

05/12/2008 5:14 PM

Yes, I agree, as i indicated previously, that SPT is the industry accepted standard, and hand held penetrometers might not be suitable.

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#13
In reply to #12

Re: field test to find bearing capacity of soil

06/13/2008 11:26 AM

Plate load bearing test

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#15
In reply to #5

Re: field test to find bearing capacity of soil

11/14/2008 10:16 AM

There is no way the pocket penetrometer works. Even the product manufactuer itself says it gives wrong information and should not be used for foundation designs (footings)

Throw it out!

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#14

Re: field test to find bearing capacity of soil

07/23/2008 8:21 AM

U can use Plate load test for soil bearing capacity, Thsi information in Soil Mechanics by Rangawala,

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