Saturated Soil Pressures

[akarimjee]

We have situation where a Soakaway 2m diameter, 10m deep has been constructed on top of Tunnel Portal which is at least 70m below the bottom of the Soakaway. The underlying soil is chalk. At present the Soakaway is working perfectly well and there is no detrimental effect on the Tunnel. However, it is known that the Tunnel impermeable roof membrane can only take 2 Bar water pressure. Can anyone with knowledge of Hydrogeotechnics advise whether the Soakaway would have any detrimental effect on the Tunnel Portal in the long run.

 

[ishvaaag]

If what your soak-away device does is to pass water to the ground it might through alteration of the chalk. However there is much distance between your pit and tunnel...I think closer consideration of the morphology is required. If the chalk zone is already under freatic level, no change at all needs to be expected.