Allowable Rock Shear Stress

[GeoGrouting]

I am designing anchors in a rock with RMR value of 40-41. (RQD = 75%)

Could anybody give me some indications about the allowable rock shear stress to be used in NAVFAC anchor design procedure. Could you let me know what would be another good reference for anchor design. Thanks.

 

[ishvaaag]

http://www.rocscience.com/hoek/pdf/14_Rockbolts_and_cables.pdf

http://isddc.dot.gov/OLPFiles/FHWA/009770.pdf

http://www.fhwa.dot.gov/engineering/geotech/pubs/if99015.pdf

Ground Anchors and Anchored Structures
Petros P. Xanthakos
Wiley 1991

http://www.dsigroundsupport.com/pro...tsbrstelpipe-bolts/mechanical-rock-bolts.html

Following a spanish recommendation...

 

[ishvaaag]

Per PTI et alternative theory...

 

[GeoGrouting]

Thank you for your answers.

I am still looking for feedback about typica; values on rock shear stersses in rock anchor design.

 

[ishvaaag]

For a start you can look at the entry table for the input in the anchor to soils 2 (one pdf of those above), there it is given an ultimate shear strength to be divided by (there) a 3 safety factor. Will try to find other resources, anyway.

 

[cntw1953]

I think it depends on the type and composition of the rock mass, a question better answered by a geologist, rather than randomly pick up a number if it is ever exist.

Just a personal thought, good luck.

 

[ishvaaag]

Ultimate values at Table 10 at

http://www.onesteel.com/images/db_images/productspecs/500PLUS_REIDBAR_Design_Manual.pdf

no less than SF=2.5 to be taken.

Another older version of the same or alike gave working loads (tables 5 and 6, see attachment)

 

[ishvaaag]

http://books.google.es/books?id=85d... of grout to fractured rock table MPa&f=false

quoting...

"In the absence of such tests, the ultimate bond stress is often taken as 1/10 of the uniaxial compressive strength of the rock or grout (whichever is less)"

 

[ishvaaag]

From Hanson, Peck and Thornburn, see attachment, the allowable compression for your RQD 75% is 117 kgf/cm^2

Since allowable that would put your shear strength for a compliant grout at 11.7 kgf/cm^2 at the grout-rock interface or slightly above 1 MPa allowable shear stress.

Best wishes ... you can try to find other lookup table, good searches in internet are quite fascinating and there is plenty info on almost everything out there.

 

[ishvaaag]

The attachment...