soil nail wall

[shorebob]

Are soil nails AS EFFECTIVE when drilled into old concrete slurry fill as when drilled into the weathered bedrock we thought was there ? This is under a structure which must be supported by the soil nail wall. If the concrete/slurry is NOT competent as a foundation mat'l., it'll have a failure plane similar to, but different from, the soil nail 'least F.S.' plane. Has anyone any experience with this ?

 

[PEinc]

To answer that question, you would need the engineering and physical properties of both the concrete slurry fill and the weathered rock. There's more to designing a soil nail wall than just knowing the bond stress of the nails' grout to the ground (rock, soil, concrete slurry, etc.). Design of soil nail walls is basically a slope stability analysis. You need properties.

 

[MSEMan]

My first question would be why is the slurry wall there? If it hasn't been flagged up in any of the geotechnical reports chances are that it was probably built because another contractor on site found something unexpected (unpleasantly so no doubt.)

While its almost inconceivable that the wall doesn't add something to the stability of the cutting, I would be very worried that it may have been put there because the previous contractor thought they were going to find weathered rock and actually found something significantly poorer.

My advice is to knock this one straight back to the Engineer.