174
X3
Project Description
Mammoet was contracted to perform the heavy lift
and replacement of one complete stator section. This
stator is part of one of the large mills which reduce the
size of the incoming raw unprocessed earth before it
enters a second mill which reduces the particle size for
final processing. The large stator section is assembled
from four quarter sections. Each of the quarter sections
had to be lifted and moved to the waiting system. The
system was then used to move the pieces out of the
building and lower to ground elevation approx. 42’
below. One of the primary challenges in replacing the
stator section is the location of a conveyor belt and
separator tower that is part of the operating plant. It
was requested that impact to the conveyor be minimal
during installation of Mammoet’s equipment to keep the
plant operational until the shutdown started. Mammoet’s
system was designed and installed months before the
actual shutdown of operation and replacement of the
components started. Once the replacement of the 4
components is complete, plant operations can continue
while Mammoet’s equipment is removed.
Structural System
The gantry on this project, like most Mammoet
structures, is assembled from a mix of proprietary
parts and custom components. The lattice towers,
strand jacks and beams were transported in from the
Mammoet yard in Rosharon, Texas. The foundations
were constructed of poured in place concrete and
installed by a local contractor.
Seismic Design
Chile is of special interest to the earthquake engineering
community, as it is one of the most seismically active
regions on earth. The main seismic source in Chile is
the Nazca subduction zone. In this area, the Nazca
tectonic plate subducts with a relatively high velocity
(80 mm/year) to the South America tectonic plate.
As a consequence of this collision, the models of the
seismic source which affects Chile can be described
as: subduction interface, intra-slab and crustal fault. All
these lead to shallow crustal earthquakes, which are
typical for this area.
For these reasons, Mammoet US chose to collaborate
with Mark Flamer P.E., an expert in seismic design
using Scia Engineer, for the analysis of the gantry
system. The results were also peer reviewed by an
industry expert in Chile.
The present seismic design code in Chile is titled NCh
433.Of96 and is based on the 1995 Uniform Building
Code (U.S.). The code offers both static and dynamic
methods for analysis of structures. Due to the size and
geometrical irregularity of the structure, the design
team chose to use the linear dynamic procedure
(Modal Response Spectrum) over the simpler linear
static (Equivalent Lateral Force) method. The design
acceleration values in Chile vary based on seismic
zone. The Collahuasi Copper Mine is located in the
second of 3 zones. The response spectrum analysis
was run with several models simulating the various
positions the gantry and load would be in throughout
the project. The critical load position found was with
the stator at the highest lift point tying the fundamental
period of the gantry and stator together, resulting in the
most mass being mobilized under seismic excitation.
The critical reactions were sent to a Chilean design
team who then specified the foundation system.
Scia Engineer
• The ease and simplicity of Scia’s graphical interface
allowed for time-efficient modeling especially in the
repeating tower structures.
• Load modeling was easily able to account for multiple
load scenarios, ranging from environmental survival
cases to the stator section’s dynamic position on the
system.
• Report generation vastly reduced the amount of
time required for compiling and revising engineering
reports. Graphical outputs and pictures also greatly
aided in communication between Mammoet and the
client as there was often a language barrier.
Software: Scia Engineer
Extraction and Replacement of a Large Stator Assembly - Collahuasi Copper Mine, Chile
Nomination Category 3: Industrial Buildings and Plants
Nomination Category 3: Industrial Buildings and Plants
