water-powered drilling in the changuinola 1 rcc dam

Transcription

WATER-POWERED DRILLING IN THE
CHANGUINOLA 1 RCC DAM
PROJECT REPORT
2015.12 PROJECT REPORT - The Changuinola I Dam © LKAB Wassara, All rights reserved.
December 2015
The Changuinola I Dam
PROJECT REPORT
1400092, Project Report: Changuinola I , ENG, 2015.12, © LKAB Wassara, All rights reserved
PROJECT SUMMARY
INTRODUCTION
KEY STAKEHOLDERS
The Changuinola I dam construction project in Bocas del Toro,
will significantly increase Panamá’s hydroelectricity production.
Once it’s complete, the country will be less dependent on other
energy resources – including imported oil – and its CO2 footprint
will be considerably reduced. The power generators in this
new roller-compacted concrete dam will be integrated with the
Province of Bocas del Toro into the Panamánian grid.
• Owner/commissioner/object: Panamánian Ministry for
Energy supported by AES Changuinola I Hydroelectric Project
S. A., a subsidiary of the US-based AES Corporation that
generates and distributes energy in 27 countries.
Wassara technology was used to drill the foundation, drainage
and grouting holes. Water-powered drilling was chosen for this
prestigious project as it has delivered successful results at a
number of similar dam projects around the world.
The drilling was finished more than three months ahead of
schedule, in May 2011.
• Main contractor: Changuinola Civil Works Joint Venture
(Changuinola Civil Works), a consortium comprising of two
Danish firms, E. Phil & Søn and MT Højgaard, in a joint
venture with Alstom Hydro of Brazil
• Main design engineer: Malcolm Dunstan & Associates
engineering and construction company.
• Sub-design engineer within geo-technique and rock
reinforcement as well as supervisor on behalf of AES
Changuinola S. A.: Golder Associates
• Consultant within different stress-relaxation creep behaviour
of RCC to contractor: ARQ Consulting Engineers*.
• Feasibility study: Vattenfall Power Consultant.
* The dam design was based on ARQ’s different stress-relaxation
creep behaviour of different RCC types.
LKAB Wassara AB | www.wassara.com | [email protected] | +46 771 760 100
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December 2015
PROJECT REPORT
TABLE OF CONTENTS
Introduction...........................................................................................................................................................2
Key Stakeholders...................................................................................................................................................2
The Changuinola I dam..........................................................................................................................................3
Background...........................................................................................................................................................4
Project Objectives and Limitations........................................................................................................................4
The Wassara Equipment Description....................................................................................................................7
Results and Experiences.......................................................................................................................................9
Project costs – Evaluation.....................................................................................................................................9
Other outcomes from the project........................................................................................................................10
Drilling Results....................................................................................................................................................11
References...........................................................................................................................................................11
THE CHANGUINOLA I DAM
Installed capacity:
223 Megawatts (15% of the national consumption)
Investment:
563 million US dollars
Power generation:
1 046.3 GWh per year
Construction start:
October 25th, 2007
Construction period:
49 months (of which the drilling with Wassara ~20 months)
Commercial start (planned):
November 19th, 2011
Height / Length:
99.2 m / 595 m (326 ft. / 1 952 ft.)
Reservoir level:
165 m (541 ft.) above sea level
Unload level:
55 m (180 ft.) above sea level
Spillway flow:
11 040 m3 (2 914 560 US gallons/s) per second
Power house:
106.4 MW x 2 Francis turbine-generator
Ecological flow:
13.4 m3 (3 538 US gallons/s) per second, 9.66 MW
3 (12)
December 2015
PROJECT REPORT
BACKGROUND
Illustration from Wikipedia: Panamá relief location map by Alexrk2 (public domain)
GEOGRAPHY
Location of the Changuinola I Dam in Bocas del Toro, Panamá
PROJECT OBJECTIVES
AND LIMITATIONS
POLITICAL GOALS
The Changuinola I construction project in Bocas del Toro is a
key part of the Panamá Government’s plans to increase the
economic growth of Panamá at a lower energy cost per kWh.
The roller-compacted concrete (RCC) hydroelectric dam has
been designed to provide the national energy system with 15%
of current national consumption: 223 megawatts.
Once complete it will decrease the country’s dependence on
other energy resources, such as imported oil, and in doing so
greatly reduce Panamá’s CO2 footprint. The power generators in
this new roller-compacted concrete dam will be integrated with
the Province of Bocas del Toro into the Panamánian grid.
Panamá has a long way to go to reach its final goals, but with
the construction of Changuinola I, the country is making good
progress. Changuinola II– also an RCC dam – is already in the
construction start-up phase, and completion is planned for
2019.
ENVIRONMENTAL CONCERNS
Environmental concerns were raised prior to construction, as the
dam is located on the Changuinola River, which constitutes part
of the La Amistad International Park – a UNESCO World Heritage
site. Despite the recognised value of the region’s biological
diversity – including hundreds of rare, endemic, endangered,
and migratory species – the Panamánian power company,
AES, and the National Environmental Authority (ANAM), failed to
conduct an appropriate environmental impact assessment.
POLITICAL AND SOCIAL CONCERNS
Another concern was the impact on the indigenous groups
living in the La Amistad Biosphere Reserve, the internationallyrecognised protected area also shared with the Republic of
Costa Rica. In the end, the project was started in 2007 and was
completed ahead of schedule, in June 2012.
IMPORTANT TO SEAL-OFF A NEW DAM FROM SEEPAGE
When constructing a new dam, it needs to be sealed-off all
the way down to competent rock in order to minimise seepage
through and beneath the dam body. This is a vital part of the
project in order to maintain dam stability. Water seepage is
common in more or less all dams, therefore there is a constant
need for monitoring, controlling and sealing-off of the seepage.
The most frequent sealing method for minimising seepage is to
drill numerous holes down to competent rock. Grout cement is
then injected through the boreholes, filling any small pockets
around the holes. This creates a so-called grout curtain. The
higher the quality of this curtain, the lower the rate of seepage
and the longer the lifetime of the dam – and ultimately the lower
the risk of the dam collapsing.
The proven Wassara method of borehole water-powered drilling
has shown to be superior in numerous aspects and applications
within dams. Drilling for grout and drainage holes is one such
application. The drilling of foundation, drainage and grouting
started in September 2009 and ended in May 2011.
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December 2015
PROJECT REPORT
PROJECT NEEDS
PLANNING FOR THE DRILLING
During the construction process, delays were out of the
question. Therefore when it came to the drilling of grout and
drainage holes, Wassara technology was the only feasible
drilling choice. This is a well-proven fact, established by the key
stakeholders Golder Associates and the Grouting superintendent
at the Changuinola Civil Works consortium.
The mission set for Wassara technology was to drill the grout
and drainage holes for the new dam without incident. In total,
~30 000 m (~100 000 ft.) was drilled. The body of the dam
itself consisted of hard concrete (80% of the drilling), whereas
the formation beneath the dam was very soft volcanic and
sedimentary rock, e. g., basalt (abrasive) (20% of the drilling),
see figure below.
But it’s not only penetration speed that is a benefit of using
Wassara water-powered technology. Another reason for the
construction company using Wassara equipment is the ability to
drill long straight, clean boreholes that allows cement grout to
reach further into cavities without the interference of dust or oil
traces. Also, the versatile characteristics of the technology (one
hammer can penetrate different geologies) as well as its benign
impact on the geology, was crucial in the decision to choose
Wassara.
DRILLING DESCRIPTION
In brief, the project required around 400 unique holes measuring
Ø 95 mm (3.5”), to be drilled vertically downwards (max.
inclination of +/- 20 degrees to the vertical) and with depths
ranging from 20 to 75 m (66 and 246 ft.) along the 595 m
(1 952 ft.) dam crest, for grout curtain and drainage. This was
done from the two 2.5 m x 2.5 m (8.2 ft. x 8.2 ft.) cross-section
galleries of the concrete dam.
Drilling-of-hole-plan of the Changuinola I Dam
Upstream face
Downstream face
Galleries
for service
and drainage
Diversion
Schematic view of the drilling grout and drainage holes
Drilling holes for the grout
curtain and drainage in a
dam gallery
This is one of the typical dam applications where Wassara drilling technology has proved
to be superior
5 (12)
December 2015
THE DRILLING AND GROUTING PROCEDURE
Drilling and grouting was performed in three steps and included
the essential hydraulic conductivity Lugeon test*:
1. Drill primary holes at c/c: 6 m (20 ft.) down to 25 m (82 ft.),
pressure test the permeability of the hole with max pressure
of 3 bar (44 psi) – with the criteria Lugeon value < 2.
Then refill the hole with grout.
2. Drill down the same hole (after the hardening of the grout);
this time to a depth of 50 m, pressure test the permeability of
the hole in the 20-50 m (66-164 ft.) zone with max pressure
of 2 bar (29 psi) – with the criteria Lugeon value < 2.
3. Drill down the same hole once again (re-grouted) to 70 m
depth, pressure test the permeability of the hole in the 50-70 m
(164-230 ft.) zone with max pressure of 10 bar (149 psi)
– with the criteria Lugeon value < 2.
* The Lugeon test is used to measure the amount of water injected
into a zone of the bored hole under a steady pressure. The Lugeon
value is defined as the amount of water lost to the surrounding
formation, in litres per minute and per m borehole at an overpressure of 10 bar (145 psi).
In case pressure tests do not fulfil the Lugeon criteria value
< 2, a secondary hole is drilled in between two primary holes
(at a c/c: distance of 3 m (9.8 ft.) and the same three procedural
steps (above) are taken.
This project, however, showed to be fortunate in regards of
geology impermeability since only a few of the holes showed
a Lugeon value > 2; meaning that few extra secondary grout
holes had to be drilled.
Drilling in action in one of the galleries
PROJECT REPORT
REQUIREMENTS CONNECTED TO THE GROUTING
PROCEDURE
For the construction of the grout curtain, the main requirement
was to ensure the holes were drilled as straight and parallel
as possible. Max allowed deviation was 2%. Additionally, the
grout hole wall finishing was very important. It had to be up to
standard throughout the entire length of the holes, so as not to
lower the quality of the grout curtain.
The importance of having a clean hole for successful grouting is
described in “Practical handbook on grouting”:
“The cuttings removal method is essential to the cleanliness
of the hole, however, for holes more than 3 m (10 ft.) deep,
standard rotary percussive button head bits are most commonly
used. These literally pulverize the rock, producing very fine
cuttings. Many drillers prefer to blow the cuttings to the surface
with compressed air but this has not proved satisfactory for
grout holes. If the drilling is in moist or wet conditions, as is
common in dams, the cuttings combine with the moisture to
form a fine slurry, which can easily block any cracks or crevices
it comes into contact with. Although contamination of defects
with at least some cuttings is avoidable, water has been found
to be the most innocuous flush medium for use in rock.”
REQUIREMENTS FOR MONITORING INSTALLATION
As stated earlier, borehole accuracy was essential to provide
the tightest possible grout curtain. Also, the holes needed to
be straight so that pendulum-monitoring instruments could be
inserted. These instruments detect deformation behaviour due
to seismic activities – if any – of the dam. Hole straightness is
important in this process since the pendulum, which has a diam
of 25 mm (1”), cannot function properly if it comes into contact
with the borehole wall at any point in the hole.
Water-powered drilling (left) gives cleaner bore holes compared to air drilling (right)
6 (12)
December 2015
PROJECT REPORT
THE WASSARA EQUIPMENT DESCRIPTION
THE WASSARA DRILLING HAMMERS AND CONSUMABLES
DRILLING EQUIPMENT
The Wassara equipment used consisted of hammers and
consumables as well as service equipment tools as shown
below:
The drilling equipment directly connected to the Wassara drilling
activities consisted of:
THE WASSARA SOLUTION – EQUIPMENT DESCRIPTION
6. Drill rig: Comacchio rig MC600
7. High-pressure water pump: Uraca high-pressure cleaning
unit RS3-45E/250 (electric), providing 216 litres/minute
(57 USgpm) at 220 bar (3 190 psi)
8. Water handling: On-site construction consisting of a
container of 1.2 m x 2 m 1.5 m (W x L x H), (3.9 ft. x 6.6 ft.
x 4.9 ft.), to which fresh river water was pumped and then
continuously re-cycled back to the high-pressure pump.
The rig was modified on-site with a Wassara high-pressure
water swivel fitted to it.
6
7
8
5
4
3
2
The top-mounted high-pressure water swivel is adapted to fit the rig
1
TECHNICAL START-UP SUPPORT AND TRAINING – ONE
IMPORTANT KEY TO SUCCESS IN PRODUCTION
1. Drill bit: Ø 95 mm (3.75”)
2. Hammer model W80
3. Check valve
4. Drill rods: Wassara 1 – 2 m (3.3 – 6.6 ft.),
including O-rings; OD 76 mm (3”)
5. High-pressure water swivel
- Service equipment tools incl. service bench built on-site
(not in figure)
The Wassara hammers and consumables were initially
purchased as a package – including technical on-site support
with a drilling expert from Wassara. The rig was easily modified
by attaching a high-pressure water swivel to it. After the
modifications, initial test drillings – 100 m (328 ft.) depth in
basalt – were carried out close to the dam itself to verify that
all components, from water handling to drill bit, were working
together as planned.
7 (12)
December 2015
Initial test drilling down to 100 m (328 ft.) depth
PROJECT REPORT
Pumping the river water from the container into the high-pressure pump
INCOMING AND OUTGOING WATER
Fresh water was taken from the nearby Changuinola river and
pumped in to a 1.2 m x 2.0 m x 1.5 m (3.9 ft. x 6.6 ft. x 49 ft.)
sized container. This water was then filtered and transported
to the high-pressure pump that powered the water hammer at
a rate of up to 180 bar (2 610 psi). In order to keep the water
as clean as possible (particles must be 50 microns or smaller
so as not to impact hammer operation) the water filters were
exchanged for new ones every two months. This ensured
smooth running of the drilling operation.
The Uraca high-pressure pump pressurizes the water to power the hammer
The outgoing water was, together with the borehole cuttings,
pumped out from the galleries into a sedimentation container
from which the water was pumped out to the nearby river. The
remaining cuttings in the container was transported away and
dumped nearby. No control of cuttings or water was considered
needed.
8 (12)
December 2015
PROJECT REPORT
RESULTS AND
EXPERIENCES
PROJECT RESULTS
The drilling project was considered a complete success. The
borehole and grouting results were as hoped for and the costs
of drilling was much lower compared to what alternative core
drilling methods would have cost. In addition, the drilling phase
was finalised well in advance of schedule – three months ahead
to be exact. With alternative methods, such as air powered
or rotary drilling, the project would have taken at least three
months longer than the original proposed schedule and the
labour costs would have been considerably higher.
Two reasons for the success could be derived from the fact
that the key stakeholders were experienced from earlier similar
projects and, thus, understood how to work with waterpowered drilling technology with a limited need of technical
support during the project start-up. One reason that the drilling
project was finished so far ahead of schedule was that the
construction company had on-site technical support and training
in connection with drilling start-up. This is often one of the key
factors to success when drilling with Wassara equipment for the
first time. A few days of training and support for customers and
other members involved in the drilling project will often ensure
any possible issues are easily cleared up: saving time, money
and minimising misunderstandings.
Impoundment at the Changuinola I Dam commenced on May 22,
2012, with closure of the two 9 m x 9 m (30 ft. x 30 ft.) river
diversion culverts. This made it the first RCC arch/gravity dam to
be brought into operation outside of South Africa and China. The
105 m (345 ft.) high dam contains approximately 895 000 m³
(236 280 000 US gallons) of RCC. At 12 midday on Friday, June
25, 2012, the Changuinola I Dam finally reached full capacity
and only started spilling after 33 days filling at an average inflow
of 127 m³ (33.528 US gallons) per second. The completion of
the project now brings urgently needed additional electrical
power to the southern-most country of Central America, where
many towns currently rely on diesel generators.
ANALYSIS AND EVALUATION OF HAMMER AND
COMPONENT WEAR
Based on Wassaras knowledge of the hammers and spare parts,
together with experience from similar projects, a thorough
analysis and evaluation of the drilling could be conducted.
The following conclusions were made:
• Due to abrasive rock conditions, wear of drill bits (high
wear on bit body whilst very low wear of the buttons) and
hammer casing was quite high, giving life length of 1 154 m
(3 786 ft.) and 6 000 m (19 685 ft.), respectively.
• Wear of the chuck was relatively low with life length of
1 579 m (5 180 ft.)
• The component most affected by the water quality and rate
of penetration was the valve, which had an average life of
2 500 m (8 200 ft.)
• The hammer piston had a longer average life than usual, of
2 308 m (7 572 ft.) due to softer rock conditions
• T he average life of the sliding cases was unusually short
at 1 765 m (5 791 ft.). This is probably because they were
incorrectly replaced together with the valve house before
their due time. The normal life time of a sliding case in
similar dam rehabilitation projects is 10 times longer
PROJECT COSTS –
EVALUATION
As stated earlier, the drilling results were very successful both
in regards to borehole quality and drilling speed; the job was
completed three months ahead of schedule. Also, the drilling
cost per m, EUR 27*, was within budget, while the Rate of
Penetration was 49 m (161 ft.) per day on average, or, when
drilling in action 0.5 m (1.64 ft.) per minute.
(* including costs showed in graphics below)
• The average of 49 m per day comes from the fact that
drilling was made on day 1, whilst on day 2 the grouting and
testing of the hydraulic conductivity was made
In brief, the project costs for the drilling-of-grout-and-drainagehole-activities for the ~30 000 m (~100 000 ft.) was kEUR 822,
i. e., EUR 27 per m (kEUR 1.4 per hole).
Summary of figures of interest:
• Average Rate Of Penetration (ROP): 0.5 m/min (1.64 ft/min)
• Average drilled m per day: 49 m (489 ft.), with 1 rig and
2 shifts per day
• T he drilling part of the project was finalized in 20 months;
thanks to Wassara 3-4 months ahead scheduled period of
24 months
• 55% of the total cost for drilling was labour costs
• 1 5% of the total cost was related to the hammers and
consumables incl. service equipment
9 (12)
December 2015
PROJECT REPORT
OTHER OUTCOMES FROM THE PROJECT
MAIN COST CATEGORIES WHEN DRILLING WITH WASSARA (kEUR)
500
455
450
400
350
300
250
200
150
122
100
100
50
0
57
9
35
6
13
17
9
THE DISTRIBUTION OF MAIN COST CATEGORIES WITH WASSARA (%)
Safety & Environment
1%
Media
2%
Hammers & Consumables
15%
Labour
55%
Service
1%
Rig
7%
Pump
4%
Training & Support
2%
Energy/Fuel
12%
Water Handling
1%
10 (12)
December 2015
PROJECT REPORT
DRILLING RESULTS
REFERENCES
Drilling resulted in a ROP of 0.5 m/min (1.64 ft./min) at the
slowest rate and sometimes as fast as 0.8 m/min (2.6 ft./min).
The hole wall finishing was also to the customer’s satisfaction,
particularly as the water-pressure Lugeon tests were successful.
• Lars Bäcklund, Equipment Supervisor at the Changuinola
Civil Works Joint Venture
AWARDED THE “MILESTONE INTERNATIONAL RCC
PROJECT”
• Dr. Lars Hässler, Golder Associates; Supervising consultant
rock re-inforcement at the Changuinola Civil Works Joint
Venture
The Changuinola I Dam in Panamá was recently awarded
“Milestone International RCC Project”, an award supported
by the International Committee on Large Dams, ICOLD that
recognised the dam as being one of the 15 dams to date to
have contributed most significantly to the development of RCC
technology. As the first RCC arch dam outside South Africa
and China, the RCC design of Changuinola I Dam was based
on the South-African consulting company ARQ’s research that
recognises the different stress-relaxation creep behaviour of
different RCC types.
• Peder Petersson, Drilling and grouting Superintendent at the
Changuinola Civil Works Joint Venture
• Practical Handbook of Grouting: Soil, Rock, and Structures
(720 p.) by James Warner, P. E., Copyright © 2004, John
Wiley and Sons, ISBN: 978-0-471-46303-0
• Magnus Hörman, Senior Engineer at LKAB Wassara
• Björn Öderyd, Technical Support at LKAB Wassara
WEBSITES:
• https://en.wikipedia.org/wiki/Changuinola_Dam
• http://www.power-technology.com/projects/changuinola75
CONCLUSIONS
Wassaras water-powered drilling technology has once again
proved to be the optimal choice for this kind of projects. In the
main, this was thanks to in-depth knowledge and extensive
understanding of the technology, as well expert technical
support in the planning, start-up and drilling stages of the
process by the key stakeholders.
Or, as the project’s Supervising consultant rock reinforcement
Lars Hässler, Technology Dr. at Golder Associates, states it:
“The water-powered technology from Wassara was chosen
for the Changuinola I Hydroelectric Project in Bocas del Toro,
Panamá, since it was evaluated to be the most feasible drilling
method to solve the drilling within the given time and quality
frames.”
11 (12)
WASSARA – COST-EFFICIENT AND ENVIRONMENTALLY
FRIENDLY DRILLING
LKAB Wassara is a Swedish company developing and
manufacturing unique water-powered drilling systems for
high performance in surface- as well as underground drilling
operations. The heart of the Wassara drilling system is the
world patented water-powered down-the-hole hammer.
The drilling systems have been used for more than 20 years
in various applications within many industries; mining,
exploration, ground engineering, dams, geothermal, marine,
oil & gas storage. Our experience covers more than 25 million
drilled meters, working in different locations around the world.
Reference studies can be found on our website.
LKAB Wassara was founded in 1988 and is owned by LKAB.
LKAB is an international high-tech minerals group that
produces iron ore products for the steel industry and other
mineral products for many other industries and applications.
Explore more at www.wassara.com

water-powered drilling in the changuinola 1 rcc dam

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