I would like to use Hilti HUS4 M16 screw-in anchors for fixing to rock, due to simplicity of installation in a tunnel.
The rock is extremely hard 100MPa
Will Hilti screw-in anchors work as intended when installed into such hard rock?
Chemical anchoring is not an option for this project.
Hello Michael,
Thank you for reaching out to Hilti.
As you may know, none of the national or international anchor design code covers anchoring into rock. The heterogeneous nature of the rock makes it very difficult to predict the performance for mechanical anchors (such as HUS4). Also if the rock is very hard, it will be difficult to install screw anchors.
We understand that you are not looking for chemical anchor but at the moment, based on our internal testing and third party research, we can only suggest using HIT RE 500 V4 into rocks and the capacity depends on the material properties of the base material (that is, the Class / Type of rock, shaft adhesion etc).
However, if you would still wish to install HUS4 anchors, we would recommend some trial installations and do on site testing to determine resistance. We leave the final decision of using this anchor based on evaluations of anchor testing up to the design engineer.
The final thing we would point out is that rocks are subject to cracks and changes in their mechanical properties, hence regular inspections of the points are also recommended.
I hope this covers your question but if you still have any doubts, please reach out to our Engineering team >> here.
Kind Regards,
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