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# Is There a Way to Estimate Coefficient Friction Without Testing?

08/07/2015 2:09 PM

Hello, I am designing a Concrete Retaining Wall, I have the Internal Friction ∅, but don't have the Friction µ. Can i get the Coefficient Friction by this formula? µ = tan(∅) Thanks and Regards

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#1

### Re: Is There a Way to Estimate Coefficient Friction Without Testing?

08/07/2015 2:18 PM

Look it up on Matweb.

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#2

### Re: Is There a Way to Estimate Coefficient Friction Without Testing?

08/07/2015 5:15 PM

How much concrete to you want to retain?

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#3

### Re: Is There a Way to Estimate Coefficient Friction Without Testing?

08/08/2015 9:51 AM

Honestly, you should already know this value if you have any experience designing concrete retaining walls.

I am assuming here that you needs this value to resist the wall from sliding?

Obtain a copy of "Foundation Analysis and Design", by Joseph E. Bowles.

It is THE "bible" for structural and soil engineering, and contains industry-wide accepted values for various soil types that you will encounter.

Make sure that you use a conservative "lower" value for the coefficient of friction to take into effect wet and/or saturated subbase material, or otherwise you're in deep Sheep Do-Do. Just another valid reason to incorporate retaining wall weep holes and perforated footing drains, to insure that the retained soil and subbase soils remain relatively dry!

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#4

### Re: Is There a Way to Estimate Coefficient Friction Without Testing?

08/08/2015 12:35 PM

Thanks for these information, appreciate, I will look deeply into the book you provided.

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#5

### Re: Is There a Way to Estimate Coefficient Friction Without Testing?

08/08/2015 2:43 PM

You are very welcome leecan.

Good luck!

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#6

### Re: Is There a Way to Estimate Coefficient Friction Without Testing?

08/22/2015 7:01 PM

The Bowles book is certainly a fine book, and the newer the edition, the better (I think the fourth is the latest, but maybe not.)

If your CMU retaining wall is more than 2 feet high, then you should need a Permit to build it.

A Permit should require some kind of a design review.

A cmu retaining wall should include an engineering design that specifies height, length, grout mix, horizontal and vertical reinforcing steel, at the very least.

And, it should be based on soil characteristics established in a proper geotechnical engineering report written by a licensed Geotechnical Engineer.

So, tell us what does your Geotech. report say

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#8

### Re: Is There a Way to Estimate Coefficient Friction Without Testing?

08/23/2015 1:13 PM

Thanks for these information, Well I am doing program for designing a retaining wall. That is why, I am trying to avoid entering lot of information. I was saw at Bowles book, that I can estimate roughly the Coefficient friction according to the type of soil.

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#10

### Re: Is There a Way to Estimate Coefficient Friction Without Testing?

09/23/2015 10:36 PM

By the way, if the surcharge is great enough, even a retaining wall with only 2 foot of exposed wall height could require a analysis.

Since you did not specify what kind of retaining wall, I intended that my discussion was to refer to all retaining walls, from the simplest, most common type of small retaining wall, starting from a simple cmu wall, through cast-in-place concrete walls, all the way up through any of the more recently developed wall types, which used to be collectively referred to as ''cribbing''.

Also, if the jurisdiction in which your wall is to be located is a large enough one, they will have standard designs that will ''govern''. Thus, under those circumstances, the local Building Officials won't allow anything less than completely conforming to their Standards, and only their Standards...

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#11

### Re: Is There a Way to Estimate Coefficient Friction Without Testing?

09/24/2015 11:14 AM

I use both RetainPro and RetainWall. Both are excellent platforms.

You can also perform manual calculations to design and analyze retaining walls, although MSE Segmental Retaining walls are much more difficult to do so.

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#12

### Re: Is There a Way to Estimate Coefficient Friction Without Testing?

09/28/2015 5:24 PM

When you want to get serious about retaining wall design, you could consider the ''PYWALL'' software from < www.ensoftinc.com > for about \$850.00 (USD), along with detailed treatments of various foundation topics, specialty books, seminars, software, etc.

( I'd give you my old (Sowers & Sowers) for free, but my second edition Bowles is not for sale at all, still...)

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#7

### Re: Is There a Way to Estimate Coefficient Friction Without Testing?

08/22/2015 7:38 PM

I believe that the OP stated he was designing a concrete retaining wall, not specifically a CMU retaining wall, but your other statements remain very valid and hold true.

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#9

### Re: Is There a Way to Estimate Coefficient Friction Without Testing?

08/26/2015 11:54 AM

@ page 648, Mass concrete or masonry on the following: Clean sound rock µ = tan(35) Clean gravel, gravel-sand mixtures, coarse sand µ = tan(∅) Clean fine tomedium sand, silty medium tocoarse sand, silty orclayey gravel µ = tan(∅), Clean fine sand, silty orclayey fine to medium sand µ = tan(∅), Fine sandy silt, nonplastic silt µ = tan(∅), Very stiff andhard residual orpreconsolidated clay µ = tan(∅), Medium stiff andstiff clay andsilty clay µ = tan(∅), in some places, i saw for some type of soil, we have µ = 2/3 tan(∅) is that correct?

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