Testing tendon support units under a combination loading scenario
NL Ayres, LJ Gardner
Tendon support systems have been successfully used to stabilize
excavations. Tendon support systems are routinely designed using the
axial load-bearing capacity of tendons, namely the tensile strength. To
attain tensile strength the tendon must be loaded along its length, which
often does not occur in practice. Tendons should optimally be installed at
90° to the surface of the excavation to achieve maximum penetration
depth, yet this is often not physically or practically possible, and installations
at angles less than 90° occur.
Furthermore, the intersection of geological features within the rock
mass frequently results in complex loading situations on tendons. The
position and angle at which loading occurs results in different
combinations of tensile and shear forces acting on the tendon, which can
impact on the support performance of each unit and ultimately the whole
system. All factors that influence the support system should be understood
and taken into account to ensure a sound support design.
Combination loading situations are further investigated and tested to
obtain a better understanding of the mechanisms involved and the effects
on tendon load-bearing capacity. Tendon support units were tested at
different installation angles to establish the tendon performance,
mechanical behaviour, and load capacity during these loading situations.
The results and outcomes are aimed at providing rock engineers with
additional data and improved understanding of how tendons could perform
under certain conditions.
Keywords: tendon support, combination loading, shear strength, tensile strength.