soil friction angle question
soil friction angle question
(OP)
I am hoping someone can help me out a little with this.
I need to confirm that the soil friction angle will equal the angle that the failure wedge makes with the horizontal. Specifically, say I have a retaining wall with soil on the left and a friction angle of 30 degrees. I am now going to draw the soil failure plane from the bottom of the wall to the top of the soil. I draw a line that extends from the bottom of the wall (up and to the left) until it reaches the soil. The acute angle formed between the horizontal at the base of the wall and the failure plane I just drew will be 30 degrees.
Is this a correct statement?
I may be looking in the wrong places, but I can't find it in my geotech book, or foundations book, and I don't have my soils notes at work.
I need to confirm that the soil friction angle will equal the angle that the failure wedge makes with the horizontal. Specifically, say I have a retaining wall with soil on the left and a friction angle of 30 degrees. I am now going to draw the soil failure plane from the bottom of the wall to the top of the soil. I draw a line that extends from the bottom of the wall (up and to the left) until it reaches the soil. The acute angle formed between the horizontal at the base of the wall and the failure plane I just drew will be 30 degrees.
Is this a correct statement?
I may be looking in the wrong places, but I can't find it in my geotech book, or foundations book, and I don't have my soils notes at work.






RE: soil friction angle question
45+phi/2. And phi being the angle of friction.
The situation that you are describing is related to slope stabilty without retaining wall.
RE: soil friction angle question
Look up Culmann's graphical solution also.
This information can be found in Principles of Geotechnical Engineering by Das.
Why do you need to draw failure planes, out of curiosity?
RE: soil friction angle question
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RE: soil friction angle question
I am assuming the 45+-phi/2 is not valid for at-rest pressure? What would you use for at-rest pressure failure plane?
RE: soil friction angle question
The classical retaining wall system must consider active earth pressure. This is due to the fact that it takes just a little bit of lateral movement to mobilize active condition in the soil mass. And the amount of deflection in all retaining wall system (that at least we design) deflect enougn to create active condition.
RE: soil friction angle question
DO NOT take the liability yourself.
Mike McCann
McCann Engineering
RE: soil friction angle question