Basement Load calculation 4

[GradStructEng]

Help!

I'm designing a basment in London UK, the soil is stiff clay and the basement is to be masonry walls with reinforced concrete in the cavity. It's a domestic three storey structure.The basement is 2.5m from ground level.

Do I need to calculate:

Overturning force
Sliding
Slip circle

And if so how? as this is not the same as calculating a normal retaining wall, or is it?

Best regards

Aaron

 

[kieran1]

Design much the same as a retaining wall, can be a propped wall if supported by the ground floor. Shouldn't think sliding would be a problem if its a true basement on four sides.

Need to design for buoyancy due to a high water table.

Helps if you have a geotechnical site investigation

Kieran

 

[msquared48]

Is the clay an expansive clay? If so, you will need to undertake special some special design measures for the wall strip footing.

As for the wall design and pressures, I agree with kieran1.

I term the propped wall as a basement wall or a non-yielding wall. I also would term a cantilever wall as a yielding wall.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[GradStructEng]

Thanks guys for your help and advice.

The water table is 6m below ground level and the soil is stiff London Clay, with a bulk unit weight of 20 kN/m^3. Do you guys know of any good guide (book/Doc) that can be used to calculate the loading e.g. worked example I could follow. I'm searching everywhere online but am amazed of how little I'm finding on this topic.

Best regards

Aaron

 

[GradStructEng]

Mike I'm inclined towards a raft foundation to prevent differential settlement.

 

[ishvaaag]

Also, masonry for 6 m deep basement walls looks scarcely practical by present standard. I think reinforced concrete is much better suited to the purpose.

 

[hokie66]

ishvaaag,
He didn't say his basement was 6 metres deep...it is 2.5 metres below ground. Reinforced concrete masonry is fine for that.

GSE,
Design for at rest soil pressure with walls braced top and bottom. Notwithstanding the water table being much deeper than your basement, I would allow for hydrostatic pressure due to surface water being retained in cracks in the clay. So my design pressure would be hydrostatic pressure plus the buoyant at rest soil pressure.

Make sure to do a good job of your waterproofing membrane, floor and walls.

 

[csd72]

GradStructEng,

There are some good publications on this type of thing published by IStructE, CIRIA and the like.

I would think that the critical item for this is the selection of an appropriate construction method for the situation you are in.

You have given no indication regarding the surrounding area though as it is in london it can be pretty much assumed that there are adjacent buildings.

It is generally typical to either support adjacent buildings with underpinning or to build a contiguous pile wall.

The questions all sound like things that you should be asking your supervising engineer.

 

[ishvaaag]

Ah yes, watertable. OK.