Shotcrete Meets Challenge of Huge Water Project in Ecuador
By replacing traditional "form and pour" methods with high production
shotcrete, the massive Trasvases Manabi Water Project in Ecuador
finished months ahead of schedule. Contractor Norberto Odebrecht
in conjunction with Shotcrete Technologies Inc., of Denver,
Colorado, and Commercial Shotcrete Inc., of Phoenix, Arizona
placed over six thousand cubic meters of shotcrete in less than
half the time it would have taken by the specified method, and
put the project a whole rainy season ahead.
The Trasvases Manabi Water Project's goal is to optimize that
country's seasonal rainfall patterns by linking a trio of reservoirs
and by constructing pipelines and transfer and delivery tunnels
to control water distribution. The end result will be a constant
supply of water for drinking, irrigation, and industrial use.
General Contractor Norberto Odebrecht from Brazil was hired
by the Centre de Rehabilitacion (CRM) of Manabi, the government
agency responsible for water improvements. Odebrecht is the
largest contractor in Brazil with more than 42,000 employees
on the payroll.
Arriving on site in May of 1999, Odebrecht was charged with
the responsibility of constructing a pumping station to lift
water from La Experanza reservoir into a pipeline that feeds
into an 11.4 KM long tunnel and discharges into the Poza Honda
reservoir to the Mancha Grande River, both to increase the water
supply to Portoviejo, the principal city of the province and
the surrounding regions.
By July of 2001, the project was five months ahead of schedule,
and Danilo Abdanur the construction manager for Odebrecht, began
to realize that they could perhaps complete the entire project
by the Rainy season (late November). The logistical challenge
to maintain the "ahead of schedule pace" on this $140 million-dollar
project called for some creative solutions.
To complete the project by the end of November, 2001 the spillway
walls of the Conguillo dam portion of the project had to be
erected. At twenty five meters high, sixty and one hundred centimeter
thick walls with a 1% tolerance and minimum of six thousand
cubic meters to place, traditional form and pour would not meet
Abdanur's aggressive schedule.
Kristian Loevlie, of Shotcrete Technologies Inc., was called
in to visit the site and meet with Odebrecht, the Owners, and
Engineers to discuss the possibility of erecting these massive
walls using shotcrete. Having done high volume shotcrete projects
all over the world, Loevlie explained that good shotcrete is
a high quality "in-place" concrete, often with much higher compressive
strength. The Group was convinced that this was the answer to
their dilemma and a unanimous decision was made to go full speed
ahead with shotcreting the entire 6000 cubic meters.
Time was of the essence and Shotcrete Technologies quickly pulled
all the logistics together including: application experts, various
mix designs, local supply of materials - sand, aggregate, plasticiser,
and then training local laborers to execute the shotcrete application
and finish. A local naphthalene based Superplastisizer was used
and ST-ALKALI Free Accelerator was used for water control
and temporary ground support.
Commercial Shotcrete Inc. of Phoenix, Arizona was chosen to
partner with Shotcrete Technologies and Odebrecht and supply
equipment as well as expertise and supervision to train and
work with the shotcrete crews.
Developing a good consistent shotcrete mix for this scope of
work is vital to the success of the job. Odebrecht had their
own batch plant on site making it relatively simple to test
all the mix components. After trying various sands, aggregates,
cements, and using as many local materials as possible, the
team came up with a workable/pumpable design which included:
> 420 kg. Cement
> 440 kg. 10 mm aggregate
> 1130kg. Sand
> 1.7% naphthalene super/plasticiser
> W/C ratio of .45
The mix design strength was 24 MPA, and in-place testing produced
32 MPA on average.
Once Commercial Shotcrete's REED pumps arrived, the first two
weeks were primarily focused on training the locals on shotcrete
technique. Alberto Medina, General Manager, and various supervisors
from Commercial Shotcrete supervised the entire application
process, from training the crews to nozzling and pumping and
setting up guide wires and finishing. As soon as the training
was accomplished crews reached a daily production rate of more
than 180 cubic meters of shotcrete using two pumps on two shifts.
The shotcrete was placed through rebar and mesh (as specified)
directly on a twenty-five meter high dirt excavation requiring
extensive temporary support. By using shotcrete, the initial
support and final one meter thick structural walls were done
simultaneously. This continuous process of excavation, reinforcement,
initial support, and final structure was very fast, efficient,
and cost effective, and shaved months off the time traditional
methods would have taken. By the end of November, the spillway
walls were finished and ready for the rainy season.
According to Danilo Abdanur, Construction Manager for Odebrecht,
the key to the project's success was choosing the proper equipment,
setting up an efficient working site, mobilizing adequate support
equipment, having a knowledgeable crew, a workable and consistent
mix design and adhering to a daily maintenance routine. However,
the biggest factor, was taking the perceived risk on a technology
that he had not used for this specific type of application.
Odebrecht also claimed a record for TBM advance following breakthrough
of the project's 4.6 km. Transbasin tunnel.
The Trasvases Project is one of the many innovative projects
around the world for which Shotcrete Technologies, Inc. is known.
For further information contact Shotcrete Technologies at 303.567.4871
or Commercial Shotcrete Inc. at www.fishershotcrete.com.