Retaining Wall Question

[djsarata]

I have a retaining wall problem that I could use some guidance on. It's not a typical retaining wall that involves retaining soils. It is a wall that needs to retain trash. There's an open bay door about 28 feet wide that is being filled in with precast planks. The precast design and connection to the columns is not the issue in this post. I need to calculate the worst case uniform load which would act on the bottom most plank. The angle of repose for the trash is about 45 degrees. The density of trash that I am using is 25 PCF to be conservative. I couldn't find alot of information on that. I was looking in my references for some guidance and found examples of retaining walls that dealt only with soils and no angle of repose. It's throwing me off and it shouldn't. I believe there's got to be an easy solution to this. Could someone point me in the right direction?

I attached a sketch for reference. Thanks in advance!

 

[knelli]

djsarata,

This is a great site for advice.... another really good site for technical engineering questions is eng-tips.com. You should receive lots of feedback there! good luck!

 

[MA_PE]

Looks to me like you'd have to calculate an active lateral pressure coefficient based on the internal frcition angle of the trash and then compute the lateral pressure at the bottom plank based on the total height of the trash pile.

 

[GCIII]

i would suggest looking at two failures. Slipping (or sliding) depending on how the wall is built on and Overturning. Each involve knowledge of the underlying material(s). You should be able to drop the weight per unit length of the trash right in the formula with the knowledge of the repose angle. Also the other BIG issue to consider is the weight of water. Is the retaining wall porious (can is drain)? I suspect not as it is a waste material and must be treated. This will add a huge force to the wall. More specifics of the wall are needed. For example, how far into the bottom of wall surface does the wall extend? Is there a "Key"? Is there a footing strip? Is the trash going to extend above the top of wall? Good luck.

 

[djsarata]

i would suggest looking at two failures. Slipping (or sliding) depending on how the wall is built on and Overturning. Each involve knowledge of the underlying material(s). You should be able to drop the weight per unit length of the trash right in the formula with the knowledge of the repose angle. Also the other BIG issue to consider is the weight of water. Is the retaining wall porious (can is drain)? I suspect not as it is a waste material and must be treated. This will add a huge force to the wall. More specifics of the wall are needed. For example, how far into the bottom of wall surface does the wall extend? Is there a "Key"? Is there a footing strip? Is the trash going to extend above the top of wall? Good luck.

I did end up going to eng-tips.com to get some insight. But The precast wall planks will be supported the full height on both ends with a continuous angle anchored to the existing conrete columns. The angles will provide a slot for the wall. That's not an issue. I can handle that design. It was calculating the pressure or uniform force at the bottom of the wall. I wasn't familiar with trash characteristics and how to apply them to soil pressure formulas. It was throwing me off but it shouldn't have. There will be no water at this height because beyond the wall (or on the right side of the sketch) is a 40 foot drop. It's the refuse bunker. The wall is simply creating an enclosure to an opening. It is also being supported by the existing concrete wall, so no foundations are needed.

The situation of having trash build up this high will be a rare occurance but it could happen during a shut down. There's actually a duct opening in the wall enclosure to convey shredded trash into the bunker area. So while the machinery is in operation, it will never build up that high. The machinery and duct hole is very close to the bottom of the new wall.

Thank you for the comments! They are in agreement with the responses I got at eng-tips.com.