Civil Engineering - Building Construction - Discussion

Please explain the answer in detail.

The maximum depth of a single-stage well point system is typically 5 meters.

This means that if the depth of excavation is 20 meters, then 3 single-stage well points would be needed, one at each 5-meter interval.

The 3 answer is only correct if we don't install the well-stage system at the top of the soil i.e the very first stage is installed at the depth of 5m.
However, it seems to be incorrect because there might be a Water table lying in the very top layer of soil i.e within the top 5m soil layer so the answer must be 4.
The 2nd thing here is that we can't use a well-point stage system for excavation greater than 15m because there is a chance of slope failure.

I am not getting this, please explain me.

Yes, the correct answer is 3 because we install single stage well point on every 5 meters and starting from top leaving 5 meters and at the end there will also be no well. Therefore the answer 3 is right.

The Correct answer is 4.

Anybody can explain it correctly?

I am not satisfied this question.

Properly explain according to excavations depth.

First well point at 5m, so that.

(20-5)/5 = 3.