BodgeBodge

Thanks! I assume the vertical reinforcement is some kind of rod which runs through the centre of the block? How did the horizontal reinforcements work? Was it a special type of concrete do you recall?

Very cool - I like the sound of your friends project! I was also thinking about the possibility of a big liner - surely the hydrostatic pressure wouldn't be very high? Even if the water table was right up to surface (which it isnt), is the hydrostatic pressure at 3m below surface still relatively low (somewhere around 4.3psi)? Easily enough to get through porous material but surely not through a decent (intact) liner / membrane of some kind? This isn't a topic I know much about so am happy to be corrected!

Yes - understood. Thank you. I did a Google of Bentonite membranes and it came up with some interesting products; "self swelling, self healing waterproofing membrane. The bentonite used in its manufacture is capable of repeated cycles of wetting and drying without deterioration of its sealing properties and has a life expectancy measured in thousands of years (BBA Certified)." 😀

Thanks for the info - will have a look into it!

Thank you - this is good info. I had not heard of Bentonite. Will make a study of swimming pool construction.

The cutter ring method sounds interesting - out of curiosity, do you know how would that be waterproofed? Tanking of some kind on the inner face perhaps?

Interesting. Would it be possible to dig a trench that deep if it were so narrow? Specialist machinery required. Also, it would surely still need shoring up.

You are right but unfortunately, it would not be possible to build a structure that tall in this location

And I am a serious (Mechanical, not Civil) Engineer! 😉 Don't worry, as I said, this is more of a thought experiment...

Hi, This is probably more of a thought experiment in truth but... If I wanted to dig a big hole (area of a single garage and 3m deep) and fit a modified car lift (so that I can get one car underground and one car above ground), what would be a typical means of: 1) Safely shoring up the sides whilst excavating. 2) Fitting a structure which will be watertight. My initial thought would be to build a steel box frame and slowly dig / lower it in to place (I.e. it serves as the shoring and the final structure). The inner faces of the frame would then be welded with a skin of sheet steel and then back filled with concrete. I'm sure someone here would have a better idea? Thanks in advance! Si