May/June 2021 - 76

water below the excavator track
surface. This approach allows users to
create more than one anchor below as
needed, based on an engineering study
to determine insertion of the most
suitable lengths and sizes of rods.
The UWA machine is composed of a
Class 450 crawler excavator and a
metal lattice with a semi-automatic
drilling cell on the bottom. This
machine has two operators' cabins -
one to direct movement along the quay
into the position of the anchorage area,
and the other, for drilling activities
using the immersed drilling cell
precisely moved by robot to initiate
drilling for the anchor.
The technical operator can manage
drilling into the quay or the anchoring
operations by managing manual
controls and system " macros " set to
minimize human error. In addition to
an operator on the quay who oversees
pumping of anchor materials and
confirms equipment positions, two
monitors in the cabin provide real-time
images from underwater cameras.
They can be positioned at the most
important points on the drilling cell,
such as the rod loading area, clamping
vices, machine frontal view and coupling
area rotary bar.
In the drilling cell, a diamond core
barrel of suitable diameter is mounted,
through which various materials (e.g.,
steel, concrete and prestressed reinforced
concrete) can pass and through
which the injected underwater anchoring
will be performed. The rod
anchoring is realized by using jet
grouting and an advanced, minijet
grouting technique. In this approach, a
hollow rod equipped with a sacrificial
bit acts as an injection element for jet
grouting and as an element for the
transmission of the load induced by the
quay once the anchor is operational.
The machine has a high-pressure
mixing and pumping plant for jet
grouting, as well as a silo for the storage
of the powdered cement necessary to
prepare the suitably dosed mixture. The
operating machine has an automated
76 * DEEP FOUNDATIONS * MAY/JUNE 2021
Phases of underwater anchoring
carousel loader where up to 10 bars,
each with a unit length of 9.84 ft (3 m),
can be preinserted. This allows for a
maximum anchor length of 98.4 ft
(30 m). The automation makes it unnecessary
to use divers to manually insert a
bar and be involved during drilling
and/or injection activities.
Coupling between one bar and the
next is guaranteed by using a metal
gasket suitable for high-pressure injections;
the best seal during jetting
activities is ensured by performing the
injections at a pressure of about 300 to
400 bar (about 4,300 to 5,800 psi).
Essential jet grouting parameters
are recorded so the cabin operator can
constantly check injection activities.
The need for underwater personnel
is limited to the placement of the loadsharing
elements. These plates will be
positioned only when the cement
mixture has had time to mature, at
which time it will be possible to
perform the appropriate structural
tightness checks.
Ravenna Port Use
Work began on the shipyard at the Port
of Ravenna in 2010. The goal of the
groundworks at the existing docks along
the south bank was to achieve the new
seabed depth at an altitude of -39 ft
(-11.9 m), as prescribed in the Port Operational
Plan. During structural reinforcement,
seismic impacts were
considered as part of recalculations
since many of these works were
designed and built without doing so.
The deepening and anchoring work
extended about 3.1 mi (5,000 m), and
was executed in phases. Anchors
May/June 2021

Table of Contents for the Digital Edition of May/June 2021
