Stability Analysis of Limestone Quarry

[geomtl]

We have been asked to determine the stability of the rock faces of an existing limestone / dolomite quarry. The owner is proposing a residential development inside of the quarry. (it has an open side to the river)

We did some initial structural mapping and discovered two major joint sets, which are basically vertical and at 90 degrees to each other. The other major feature is the bedding planes, which are horizontal. The overall height of the quarry face may reach 22m. (75ft)

I am wondering what methods are out there to determine the overall stability of the cliff face, given the structural discontinuties mentioned above.

Thanks for any insight to get this started.

 

[jdonville]

geomtl,

I suggest that a firm with rock or mining engineering experience be retained to analyze the stability of the quarry walls. This is not a good area for experimentation.

For a previous project I was involved with, the geotechnical consultant retained Chuck Brawner as a specialist consultant for analyzing and making recommendations for the stability of a sheer limestone rock face. cobrawner@lightspeed.bc.ca

Alternately, the engineering firm of Consoer, Townsend, Envirodyne Engrs. Inc. in Chicago has been involved with at least one limestone quarry wall investigation and engineering project for the Chicago Underflow Plan (Thornton Transitional Reservior). You may try contacting Nick Textor or Bridget Hamman for more information.

http://www.cte.aecom.com/Office/38/47/index.jsp

Jeff

 

[MSEMan]

Absolutely agree with Jdonville. You've properly identified the major issues (joint sets and bedding planes) but how stable these may be, and the implicaitons for design, are an issue for a real rock jock.

 

[Mccoy]

geomtl,
sure 22 m ain't a small face. Residential development means people walking around. Risky situation.

Anyway, how about the 2 vertical joint sets, they may cause a toppling hazard if (sub) parallel to a quarry face.

horizontal layering is allright.

Vertical joints may host water which acts as a jack when frozen. If the survey has been accurate some nailing/anchoring to avoid toppling would suffice.

Hopefully you did not miss any joints inclined toward the development area. That would be tough shoot indeed if slidign occurred.

One more hazard would be potential fall of debris of various sizes. Hard to say more without seeing the actual place.

a preliminary method would be Romana's Slope Mass Rating (SMR), I applied it in situations similar to yours (albeit in smaller faces) with good results.

Also, Rocscience 's Roclab, freeware, gives out a max height for a vertical face given a visual comparison to rock mass classes (GSI method, an evolution of Bjieniawski's RMR).

More methods and specific softwares are available, you might want to browse Rocscience's site.