Environmental Engineering Reference
In-Depth Information
Figure 11. an illustration of the material encountered
at the heading of the excavation.
Figure 12. a collapse of the heading is shown that
ceased when the natural slope of the materials involved
reached 45 degrees.
the rock fall y fill the void left on top of the gal-
lery prior to proceed further inside. This problem
caused a delay of several months.due to collapse at
the front (see Figure 12 ) .
in Figure 13, can be observed the emerging of
the grout as well as a slight stratification toward
the right side wall.
We started injecting a water-cement grout in
advance of the heading to be excavated. (see
Figure 14 ) .
The shield was left in place but the rods were
replaced by galvanized steel pipes used to inject the
water-cement mix. The stones were obtained at the
job site and in this way, since the pipes remained
embedded in the cement grout we could build a
reinforced concrete dome overhead and above the
trusses.
Grouting was quite sensitive in terms of pres-
sure as well as dosing. if the mix was too thick and
applied with low pressure, only a bulb surround-
ing the pipe could be obtained; whereas if the mix
was very fluid and under a high pressure, a water-
proof the flow of water from the spring and that
could alter our route to the Fuente santa could be
obtained. shortcrete was applied to the heading
and the excavation could then proceed at a slow
but uninterrupted rate.
Ten meters further from the beginning of this
second phase, boulders began appearing at the
foot of the heading. They were the largest parti-
cles found at the heading and therefore were used
to pack the extrados of the gallery. These boulders
were the pebbles of the former beach; the sea shore
was and this was confirmed after finding barna-
cles seashells among the stones. Thickness of car-
ried material progressively increased until almost
reaching the height of the roof and subsequently
decreasing in thickness. only a dozen meters far
inside the old cliff. was detected.
Figure 13.
change of the excavation procedure: cement
grouting.
Figure 14. it can be observed the stabilization obtained
using, in addition to grouting, the application of short-
crete, in this case at the roof and right side wall.
 
 
 
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