Secant pile wall question 2

[pelelo]

Engineers,

I am involved in the design of a secant pile wall. There is a house which boundary is exactly on the property line which will be adjacent to a 10 ft deep excavation. Due to this, a secant pile wall will be the best option as support system.

Please refer to the picture attached. It shows the construction of a secant pile wall with weep holes as draining system. Obviously, the water will come out of the wall and drain through the sidewalk.

In my case, since the secant pile wall I am designing will be below ground surface (10 feet below ground), I will not be able to use weep holes as shown in the picture.

I was wondering if anyone knows any other type of draining system that could collect the water coming from the soils between piles?. For you to have an idea, the bottom of the excavation will be a garage.

Please advise.

 

[HTURKAK]

10 ft deep excavation is not deep and probably would be above GWL..
If necessary, sump pumping could be an option..( the set up would be , provide temp. ditch parallel to the secant wall and a sump with a submersible pump ..)

 

[pelelo]

Thanks,

In this case, BOE is way above water level.

I wanted to think of an alternate drainning system to account for surface runnoff and rainwater.

 

[hokie66]

Any drainage you use, including weep holes, will need to daylight above the lower level to do any good. So what is the issue?

I think HTURKAK is talking about a temporary solution, but don't you want something permanent? Could use a grated trench drain, piped to a sump with submersible pump.

 

[EireChch]

if properly designed and waterproofed, a secant piled wall should let through minimal water.

Weep holes are only used for drainage that daylights as Hookie said.

The below link is a very good general reference.

If not experienced you should contact a local waterproofing expert.

https://architecturetoday.co.uk/going-underground-2-waterproofing-complex-basements/

Also, the below standards are a good starting point

1. BRITISH STANDARDS INSTITUTION, BS 8102:2022. Code of practice for the protection of below ground structures against water ingress. BSI, London, March 2022.
2. BRITISH STANDARDS INSTITUTION, BS EN 1992-3. Eurocode 2. Design of concrete structures. Part 3 – Liquid retaining and containing structures. BSI, London, 2006.

 

[pelelo]

Thanks.

I case you want to use the option of drilled shafts, how do you decide to use the option of drilled shafts next to each other (tangent piles) or spacing the drilled shafts at an specific length between each other?. The soil strata is basically medium to stiff clay, above the WT.

 

[EireChch]

A secant (overlapping piles), tangent (touching piles) or contiguous (150mm approx gap) can all be made waterproof through the application of shotcrete.

Obviously secant piles walls over superiors waterproofing as they are overlapped.

Constructability players a big part. In your instance , clay above WT, then a contig wall should work.

If it was below WT a contig wall might work if you also use a pump and your time for construction is small and your ingress is limited. Even then you may still go with a secant wall as it’s messy business to be dealing with ingress.