Retaining Wall - Driving Moments Greater Than Resisting Moments
Retaining Wall - Driving Moments Greater Than Resisting Moments
(OP)
I have a retaining wall (floodwall) with water on the left hand side and the soil only about 2 ft above the heel and the toe. So the retaining wall is being driven from left to right. I am making point A at the bottom of the toe (which is on the right side). Due to the loads and limited construction space I plan to put this retaining wall on piles.
When I calculate the driving moment (Water, At Rest Pressures, and Uplift) and resisting moment (Weight of water above heel, weight of concrete, weight of soil and passive pressure)about point A (Bottom of Toe) the Driving Moments are Greater than the Resisting Moment. So when I Sum the moments I obtained a moment in the clockwise direction.
When I try to figuere out the location of the Vertical resultant (pointing up), the resultant has to be to the right of Point A (not within footing), for the Sum of the Moments to be equal to zero.
I guess typically, the Resisting Moments are greater than the Driving Moments so you have a counterclose-wise moment at point A, resulting in the Vertical Resulant Point Up, and to the left of point A (within footing).
Does it make sense to have the Vertical resultant to the right of point A (not within footing) because of the Driving Moments are greater than the Resisting Moments? Or is this something that is not appropriate and need to consider another proccess?
THANKS, Really Appreciate Your Comments.
When I calculate the driving moment (Water, At Rest Pressures, and Uplift) and resisting moment (Weight of water above heel, weight of concrete, weight of soil and passive pressure)about point A (Bottom of Toe) the Driving Moments are Greater than the Resisting Moment. So when I Sum the moments I obtained a moment in the clockwise direction.
When I try to figuere out the location of the Vertical resultant (pointing up), the resultant has to be to the right of Point A (not within footing), for the Sum of the Moments to be equal to zero.
I guess typically, the Resisting Moments are greater than the Driving Moments so you have a counterclose-wise moment at point A, resulting in the Vertical Resulant Point Up, and to the left of point A (within footing).
Does it make sense to have the Vertical resultant to the right of point A (not within footing) because of the Driving Moments are greater than the Resisting Moments? Or is this something that is not appropriate and need to consider another proccess?
THANKS, Really Appreciate Your Comments.






RE: Retaining Wall - Driving Moments Greater Than Resisting Moments
Looks more like a dam for me.
Why not try dam & earth retaining fora here.
Otherwise i would simply try to change the dimentions so i would not have such a big diference in the moments.
for a dams if i am not mistaken(please corct me team)you should never get an uplifting at the back of the foundation.
The other thing to take into account is the type of the soil. Make sure the water do not pas underneath your wall.
Y
RE: Retaining Wall - Driving Moments Greater Than Resisting Moments
I recommend that you check out the Corps of Engineers Engineering Manual (online) to get some idea of what your doing....sounds like a beginning effort.
Regards,

Qshake
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
RE: Retaining Wall - Driving Moments Greater Than Resisting Moments
DaveAtkins
RE: Retaining Wall - Driving Moments Greater Than Resisting Moments
Shouldn't your piles be providing uplift resistance? This could be your problem. Note that uplift is not usually included in overturning calculations as an external force. Usually any buoyancy issues are addressed by modifying the submerged unit weight of the materials.
Jeff
Jeffrey T. Donville, PE
TTL Associates, Inc.
www.ttlassoc.com
The views or opinions expressed by me are my own and do not necessarily reflect the views or opinions of my employer.
RE: Retaining Wall - Driving Moments Greater Than Resisting Moments
Appreciate your advice and any suggestions on what I should might consider doing.
THANKS
RE: Retaining Wall - Driving Moments Greater Than Resisting Moments
You should have a net restoring moment and the issue should be whether or not the resultant is in the middle third of the base, or whatever criteria you feel comfortable with.
RE: Retaining Wall - Driving Moments Greater Than Resisting Moments
So now I looking into designing a pile supported retaining wall. I am using the methodoly by Foundation Engineering: Peck, Hanson and Thorburn.
I have increased my footing width to make the resisting moments (173 k-ft) greater than the overturning moments (165 k-ft). I know this is just by 8 k-ft. Also by doing this the resultant is within the footing area - but just barely.
Should my intent still be to place the resultant within the middle 1/3 even if I am using piles? Appreciate all your help and advice.
THANKS
RE: Retaining Wall - Driving Moments Greater Than Resisting Moments
RE: Retaining Wall - Driving Moments Greater Than Resisting Moments
DaveAtkins
RE: Retaining Wall - Driving Moments Greater Than Resisting Moments
LOADINGS THEN HAVE TO BE TAKEN AS FOR A SEMI-SATURATED SOIL AS THE TERMINOLOGY GOES AND OF COURSE SOME SEEPAGE TOLERATED AT THE REAR WALL SITE
OR OF COURSE JUST RAISE AND BED THE SEDIMENTS ABOVE THIS BUT THIS ADDS TO THE SURGE TOWARD THE FLOOD.
REGRADING ALWAYS LEADS TO SOME SETTLEMENT WHICH YOU WILL HAVE BEEN TRYING TO AVOID ACCORDING TO YOUR DESCRIPTION AND I CONCUR WITH THE INSTABILITY COMMENTS MADE BY OTHERS REPLYING.
THE ONLY ANSWER WITH MATHEMATICS IS TO STAY WITH THE FORMULAE AND PRECEPTS FOR DESIGN AND IF IT DOES NOT WORK OUT THEN THINK OF SOMETHING ELSE AND TELL THE CLIENT SO.
CLIENT DEMANDS MAY TRY OPTIONS AND I HAVE PROGRAMMES THAT WILL PROVIDE HUNDREDS AS I WAS TIRED OF PEOPLE PRODUCING ONE ANSWER BECAUSE THE DATA DID NOT EXIST, THE DATA HAD TO BE ASSESSED EVERY TIME AND CALCULATIONS TOOK SO LONG. THIS LEADS TO RISKS AND STOPS STUDENTS FORMING ONE DESIGN AND GOING FOR COFFEE FOR THE REST OF LIFE
BUT THEY DO NEED A CAREFUL CE APPROACH AND KNOWLEDGE OF YOUR EXPECTED END RESULT, WHICH YOU DO HAVE CLEARLY.
THE ANSWER IS MUCH THE SAME, TRY OPTIONS OF MOVING THE WALL, CHANGING THE CONFIGURATION, OR POSSIBLE TRENCH IN THE BASE AND RE-DESIGN OF THE FOUNDATION, BUT AS WE ALL KNOW IF THE BIG RIVER SCOURS OUT THE BASAL SEDIMENTS WE ARE ALL IN IT, SOMETHING POLITICIANS FAIL TO APPRECIATE
MIKE STAGG
RE: Retaining Wall - Driving Moments Greater Than Resisting Moments
RE: Retaining Wall - Driving Moments Greater Than Resisting Moments
Yes, I am designing this floodwall/wall with piles using the EM 1110-2-2502. I am using 50% passive pressures and including those in Overturning and Sliding ananlysis. And I am using At-rest pressures for the soil on the waterside.
I have also placed the water to the pool elevation on the water side. I am aware that I also have to design this floodwall for the water to be at the top of the wall per the EM.
One thing that I am still trying to get info. is the location of the water on the landside. Currently I have the water on the land side to the bottom of the footing, which gives me a triangular uplift pressures. I am not sure if I should raise the water on the landside to the top of the soil, which will give me a trapezoidal pressure BUT will also give me resistance due to the horizontal pressure.
At the momoent, I have increased my footing to 14 ft and now my resultant is about 4 feet from the toe. When I design for water at the pool elevation I have all my piles in compression, but when I place the water to the top of wall I have the piles near the heel in tension.
I guess here is another question I have and would really appreciate your feedback on it any other issue I sould look into:
1. What will give me a more conservative desgin, placing the water on the landside on the bottom of the footing or to the top of the soil?
Really Appreciate Your Feedback and Advice.
gman1
RE: Retaining Wall - Driving Moments Greater Than Resisting Moments
RE: Retaining Wall - Driving Moments Greater Than Resisting Moments
Does anyone have experience with sheet piling, and have an idea if it could be design to be water tight and hold approximately 15 ft of water?
THANKS