Hello, I am in need of assistance regarding a mini project of designing a retaining wall, Geotechnical, and structural design. If you could help please kindly reply to this post
Hi, PEinc hence why I kindly asked for engagement, thanks for the reply. I have a series of questions but the first questions asked us to design the cantilevered RW I have attached my initial workings, the confusion I have is how do I calculate the surcharge caused by the water tank? and where does it act, on the sloped portion? or straight?
according to the above-sent workings how would you calculate the surcharge by the water tank? N.B the area is prone to floods snd supporting a water wank my initial solution was having the water table all the way up(which is not economical but in dealing with floods I think it's conservative, and we were only given 1 gamma, not Gamma saturated. Yes, the soil is cohesive c=40kpa The original question looks like this without the retaining wall drawing.
There are different ways to calculate the lateral load to a wall from a surcharge behind the wall. You can consider an area surcharge where ps = q x ka. Or, you can use a Boussinesq analysis which accounts for offset distance between the back of the wall and the front edge of the surcharge. Which method has your professor taught?
Your bigger task may be to calculate the lateral earth pressure due to the broken slope soil behind the wall. Did your professor talk about the sloped ground surface behind the wall?
The surcharge from the water tank includes the weight of water, the tank weight, the slab weight, and any tank roof surcharge load like snow. depending on the tank height, there could also be some additional surcharge due to wind load against the tank.
In your wall design, you also need to consider drained and undrained conditions for your cohesive soil behind the wall.
thanks for the reply.Yes, we did Boussinesq in our Geotech 1 class to estimate vertical stresses imposed on the ground. For sloped surfaces behind the wall,we were introduced to Mor Coulumbs law+Culmanns Graphucal proccedure to compute our lateral earth pressures,but our professor suggested/warned that using coulomb to compute passive pressures may yield way to high values. Please I ask for your patience,I will now work out the Boussinesq method and I'll re post for some clarity. Some questions I have is:
1.The method I used to size the wall is just a procedure to have initial sizes, I heard its possible to use Euroode 7 combination 2 to size our structures, are you aware of this method? If so how do we apply it?
For the lateral surcharge, use the Boussibesq equation for lateral preasure, not vertical stress. You may need to convert your circular tank base area to an equivalent rectangular area to use in the equation.
