What bond strength and stiffness is recommended for swellex bolts?

The RS2 Online Help presents typical values for Swellex bond strength and bond shear stiffness.  These parameters come from a review of lab and field tests performed by different organizations worldwide, as indicated by Atlas Copco (2006).

To quote the correspondence received in 2006:

The parameters we are providing come from a review of many lab testings and field tests done throught out different organizations around the planet. We suggest that you implement theses parameters in your modelling package so that any future users will start with the most representative parameters caracterizing swellex. 


In hard rock:

Mn12 et Pm12:  Bond strength:  0.17 Mn/m
               Bond shear stiffness: 100 Mn/m/m

Mn24 et Pm24: bond strength:  0.3 Mn/m
               bond shear stiffness:  200 Mn/m/m

In weak rock with a low Young Modulus, reduce the values to:


Mn12 et Pm12:  Bond strength:  0.12 Mn/m
               Bond shear stiffness: 75 Mn/m/m

Mn24 et Pm24: bond strength:  0.2 Mn/m
               bond shear stiffness:  150 Mn/m/m

 

For estimating bond shear stiffness, the following equation for Kbond is also recommended.  This equation comes from Itasca, and Kbond is the same as the bond stiffness in RS2.  Note that the default properties in RS2 are for rock, and it is suggested that these be factored by 10 for soil.

groutShearStiffness.png

Description of Kbond equation (Itasca)

 

There is also a book on cable bolting by Hutchinson and Diederichs, and a handbook by Stillborg.  These have some properties.

Hutchinson, D.J. & Diederichs, M.S. 1996. Cablebolting in Underground Mines, BiTech Publishers.

Stillborg, B. 1994. Professional users handbook for rock bolting, 2nd edn. Clausthal-Zellerfeld: Trans Tech Publications.

 

Finally, another reference is the Rockbolts and Cables chapter of Hoek's Practical Rock Engineering.