SPIDER® Rock protection system - Geobrugg AG

SPIDER ® Rock protection system / Technical documentation / March 2010
Fig. 3: Blow-out niche as test terrain
Fig. 4: Anchorage arrangement
Fig. 5: General view of the Calanda
massif, west of Chur, Switzerland with
the test location
4
TEST CONCEPT
The objectives of the large scale fi eld tests were to investigate under the
most realistic conditions the supporting behavior of the rock protection
system, the interaction between the system components and the direction,
also the level of the forces transferred from the unstable block via the net
into the individual anchorage points in a 1:1 scale under different boundary
conditions.
For this purpose an ideal site was found at the foot of the Calanda massif
in the district of Felsberg west of Chur, Grisons, Switzerland, which was accessible
to transport vehicles and satisfi ed the work safety requirements.
Thanks to the support of the local community and a local contractor, the
test installation was speedily erected and the necessary auxiliary equipment
made available without problems.
This comprised a U-shaped blow-out niche, open at the bottom. The sliding
surface slopes forward at an angle of approx. 55°, therefore away from the
Rheintal. In this area the banking thickness of the solid limestone is approximately
0.40 m and corresponds to the thickness of the blown-out slab.
The carbonate formation belongs to the Helvetian blanket and was steeply
inclined through the mountain folding process.
The width of the niche is approximately 2.5 m at the top widening to approximately
4.0 m towards the bottom. The length viewed in the line of dip
measures approximately 3.5 m. The lower area of the test site is formed
more or less vertical over a height of approximately 2.5 m.
Directly above the test site a light-weight fence was erected as a work
protection from dislodged small stones, for example by rock goats or by
weathering.
Three nails type GEWI with D = 28 mm were installed above, below and at
both sides of the niche for the point anchorage of the net. In addition two
anchors were installed at the side in the niche itself. This arrangement permitted
tests, taking into account different anchor confi gurations.
Test location