Active pressure in bedrock + thanks

[shorebob]

First, my deep thanks to all respondants who helped with experiential insight re: wood lagging left in place. The compilation of replies helped turn the tide and, on this job, it will now be permitted.
Now, does anyone have a reference for development of active pressure values for bedrock. Specifically, this stuff is phyllite, highly to moderately weathered, foliated (30 deg to 60 deg.) and highly fractured (irregular breaks). P-wave velocities vary from 1200 fps near top to 11,000 fps near B/excav. The G-tech has spoken, but I'd like to check an independent reference. Thanks.

 

[BigH]

I can't see active earth pressures, per se, in unweathered rock unless
1. The foliations are directed into the excavation (e.g., into the wall such that the rock mass is sliding into the wall - hence you'd have the rock mass pressures pushing against your wall - not traditional active earth pressure.
2. the rock would have a bit of a swelling potential - such that water seeping down between the wall and the rock might cause swelling pressures - again, not traditional active earth pressures.
3. the rock contains brecciated zones or joints of significant soil infill - then, you might have earth pressures - but pressures would be relative to the rock structure - i.e., is the brecciated zone or the joint breaking down into the wall? If so, see 1 and 2 above.

If you have moderately to highly weathered rock (e.g., residual soil), you will have earth pressures to deal with and it is not so straight forward. Estimates of the weathered properties (effective phi or undrained shear) would have to be made in order to derive the active pressures.

Anyway - the above is my initial take on the subject.