Water Power and Dam Construction - Issue November 2009
Подождите немного. Документ загружается.
WWW.WATERPOWERMAGAZINE.COM NOVEMBER 2009 21
GATES
W
ITH more than fifty applications around the world
ranging from 0.9m to 9m in height, the Fusegate
System has gained significant international recog-
nition over the past few years as a reliable spillway
control system. The system is typically used to increase spillway
discharge capacity and/or reservoir storage capacity. Upon success-
ful performance at Terminus dam in California, the US Army Corps
of Engineers (USACE) has been considering the system for more
projects. The Otter Brook and Canton dams are other examples of
the ways this system can be applied to bring dams with undersized
spillways to up-to-date safety standards.
THE FUSEGATE SYSTEM
The Fusegate System is a non-mechanical spillway control technol-
ogy to increase reservoir storage capacity and/or to increase spillway
discharge capacity.
Fusegates are free standing blocks placed side by side on a spill-
way sill to form a watertight barrier. The Fusegate System oper-
ates as a straight or labyrinth crested weir divided into segments
or individual ‘Fusegates’, each forming one component of the weir.
Each gate consists of three components; a bucket made of metal or
reinforced concrete, a base, and an intake well that is connected to a
chamber in the base. Each Fusegate sits on the modified spillway sill
and remains in place only by gravity. Toe abutments (lugs) anchored
into the sill prevent them from sliding in the downstream direction.
Accumulation of seepage water in the bottom chamber is prevented
by providing each chamber with two drains. The joint between adja-
cent Fusegates is sealed with a flat rubber gasket.
Fusegates can increase both spillway capacity and reservoir stor-
age. For a retrofit on an existing spillway, a portion of the ogee crest
is removed and provided with a flat surface. If the goal of the retrofit
is only to increase spillway capacity, the crest of the Fusegates is set
near the original ogee crest elevation. If the purpose is to increase
storage, then the crest of the Fusegates is set above the original ogee
crest elevation. For discharges up to the design flood, the Fusegate
functions like an aerated labyrinth weir. Typically, the design flow
is chosen to be the discharged with a return period of about 100
years or above. For discharges greater than the design flow, water
begins to flow through the well and into the chamber located in the
base of the gate.
When the overtopping flow reaches the selected design pool eleva-
tion, the designated Fusegate(s) will tip downstream, thus increasing
the discharge capacity of the spillway. The tipping is initiated by
water entering into the base chamber of the Fusegate via an intake
well set at tipping design elevation. Once water enters into the base
chamber, the uplift pressure rapidly increases, causing the Fusegate
to rotate about the toe abutments and tumble downstream. By mod-
ifying the ballast provided for each Fusegate and the elevation of the
Hasan T Kocahan, Russell Wyckoff and
Martin Wosnik describe the US’ experience
with the Fusegate spillway control system to
bring dams with undersized spillways up to
current safety standards
Bucket
Side seal
Inlet well Overspilling
crest
Downstream
abutment
block
Downstream
bucket block
Concrete sill
Upstream seal strip
Figure 1:
3-D viewof a Fusegate
Base
Upstream
Downstream
Drain holes
Pressure chamber
Figure 2: Bottom view of a Fusegate
Spillway inadequacy
remediation in the US
22 NOVEMBER 2009 INTERNATIONAL WATER POWER & DAM CONSTRUCTION
GATES
intake well, each Fusegate can be designed to tip at a different (pre-
determined) pool elevation so that an excessive flow increase does
not occur downstream. Small drain holes exist at the base of the
Fusegates to help drain any leakage through the seals so that uplift
pressures do not occur until water elevation reaches intake wells.
The crest of the well in each Fusegate is set at a different eleva-
tion so the gates do not tilt in unison. In this manner, the increase in
discharge over the spillway, as a function of reservoir elevation, can
be precisely controlled. Figures 1 and 2 show the three dimensional
views of a labyrinth crested Fusegate.
Constructing a new auxiliary spillway controlled by Fusegates is
also another way of conducting dam safety upgrades in the case of
severe spillway discharge inadequacies, where the service spillway
modification is not feasible. In this scenario, the services spillway
– usually equipped with mechanical gates – would discharge more
frequent floods and the emergency spillway will only operate during
extreme flood events.
OTTER BROOK APPLICATION
Project background
Otter Brook Dam, located near Keene, New Hampshire, was con-
structed in 1958 as a flood control structure on a tributary of the
Connecticut River. It is owned and operated by the USACE, New
England District. The dam consists of a 40.5m high and 392.6m
long rockfill embankment impounding 22.6Mm
3
of water to con-
trol a basin area of 121.7km
2
. A pool of 6.1m depth is maintained
behind the dam for recreational purposes. The remainder of the
storage volume is available for floodwater containment.
The embankment constitutes a flow restriction, with resultant
outlet capacity of up to 37m
3
/sec with the pool at the spillway crest.
The water is dammed from a channel invert elevation of el. 208.2m,
up to the spillway crest elevation of el. 238m and up to a top of dam
elevation of el. 244.5m.
There was a 44.2m wide concrete ogee spillway with a gently
sloped (1% grade) 91.4m long unlined approach channel and a
more steeply sloping unlined spillway exit channel (8.2% grade,
reducing after 182.9m to 4.7% grade). The discharge capacity of
this spillway was 963m
3
/sec.
Flood routing simulations based on the updated storm data have
revealed that the dam would be overtopped by 0.30 m during a
PMF event as the new spillway discharge capacity requirement was
to pass 1642m
3
/sec.
The shortlist of options considered
Initially, options to raise the dam, widen the spillway, lower the
spillway, store floodwaters, remove the dam, and construct an extra
spillway were reviewed. Six basic options were then selected for
more detailed study:
U
1. Lower the spillway sill by 2.7m and recover the storage with the
installation of 2.7m high Fusegates.
U
2. Raise the dam 0.4m and widen the spillway 15.2m.
U
3. Raise the dam 1m and widen the spillway 7m.
U
4. Add a 20.4m long new auxiliary spillway controlled either by
a fuse plug or a mechanical gate.
U
5. Remove the existing spillway weir and excavate the spillway
channel down 0.9m to obtain a new crest ‘weir’ capable of pass-
ing the PMF.
U
6. Widen the spillway the full 23.8m required to maintain an
acceptable freeboard without raising the dam. Options 5 and 6
increased downstream flows for significant storms smaller than
the PMF, and so some investigation of design and historical
storms needed to be performed.
Proposed Fusegate design
The option to lower the spillway sill and install Fusegates to restore
the normal pool elevation was selected as the most viable, since it
limited the construction to the existing spillway weir structure and
approach channel, requiring wetland mitigation in the upstream
wetland only. Under this scenario, the existing concrete spillway
was removed and its foundation was excavated down to el. 235.3m.
A new broad crested concrete weir was then constructed with the
same top elevation as the existing spillway, which formed the base
for Fusegates. This ensures that the existing capacity of the res-
ervoir and flood attenuation behaviour is not compromised. The
Fusegates will topple over as the upstream water level in the lake is
increased due to the extreme storm, thus increasing the capacity of
the spillway channel. Figure 4 shows the three dimensional view of
a straight crested Fusegate, which offered the most suitable type of
Fusegate for the Otter Brook application.
The choice to excavate the spillway approach channel in order
to enhance the spillway hydraulic performance, rather than raise
the dam, saved the construction costs for a wall on the upstream
side of the dam and avoided the need to raise the threshold of the
control structure. Excavation on the environmentally sensitive east
bank of the downstream channel is avoided through the use of an
80.8m long dike, which is needed to contain the floodwaters within
the spillway discharge channel.
The Otter Brook application includes the installation of six 2.7m
high 7.3m wide straight crested Fusegates on a newly constructed
44.2m long and 3.4m wide concrete spillway platform. The top
of the platform was set at el. 235.3m on the 36.5m long portion
of its right bank and at el. 236.5m on the remaining 7.3m long
section on the left bank. The higher section of the platform was
designed to accommodate the last Fusegate to tip for the full PMF,
thereby protecting the wetland located downstream from frequent
overspilling.
The approach channel was excavated in such a way that it sloped
down to el. 235m at the spillway sill location with a 1% gradient.
No major excavations were required downstream of the new sill.
Abutment walls 0.18m wide were to be constructed on the left and
right banks of the spillway to support the watertight seals that were
installed between the Fusegates and the spillway abutments. A 0.4m
Log boom
Intake tower
Dam
Davis Road
Branch Road
Weir
Outworks
O
t
t
e
r
B
r
o
o
k
V
ertical
seal
Inlet well
Horizontal
slab
Concrete sill
Overspill crest
Toe abutment
Horizontal seal
Figure 3: Otter
Brook dam plan view
Figure 4: 3-D view of a straight crested Fusegate
WWW.WATERPOWERMAGAZINE.COM NOVEMBER 2009 23
GATES
thick pier was also constructed between the lower and elevated sec-
tions of the platform to install the watertightness seals on two adja-
cent Fusegates.
The Fusegates at Otter Brook are designed to tip for extremely
low probability events. The first Fusegate will tip for a flood cor-
responding to 55% of the full PMF. Considering that the first and
only time water has flown through the spillway was in 1987 with
the water level 0.5m above the spillway sill, the magnitude of such
a flow, which creates a 4.7m high water elevation above the sill, can
be better understood.
Construction stage
The construction works at Otter Brook Dam began in May 2005.
The works consisted of removing the existing ogee weir and spill-
way sill from the spillway channel; excavating the spillway channel
floor upstream and downstream of the existing weir; placing a new
concrete sill, a concrete pier and concrete abutment walls on both
sides of the spillway channel; and installing six Fusegates on the new
spillway sill. Associated with this work was also reconstruction of
a wetland upstream of the Fusegates and construction of a dike on
the left side of the spillway channel.
The Fusegates can be manufactured or constructed either in steel
or concrete. Otter Brook Fusegates were made of pre-cast concrete
by Old Castle Precast of Auburn, Maine, with stainless steel inlet
wells. This selected material came out the most economical for Otter
Brook with added advantages in terms of long life expectancy and
extremely low maintenance costs. The Fusegates weighed 40 tons
each at the time of delivery from the plant before their concrete bal-
lasts and inlet wells were attached.
The general contractor for the construction works was George
R. Cairns and Sons, Inc. from Windham, New Hampshire. The
construction works were delayed for about three months due to
45.7cm of rainfall in nine consecutive days during the month of
October 2005. The rain caused the swelling of every local brook,
stream and river, some beyond flood storage, and many roads were
washed away and houses flooded.
After cleaning up works following the October flood, the con-
creting of the new spillway sill began. In the meantime, the pre-cast
Fusegates had been completed and were ready to be shipped to the
dam site.
Before the installation of Fusegates, all concreting works related
to the new spillway sill, toe abutments and the pier separating the
elevated and lower section of the sill were completed except for the
side abutment walls.
Once the Fusegates were delivered to the dam site, they were
directly placed in their final position. Figure 6 shows the placement
of Fusegates and the inlet wells.
Left top: Figure 5 – Downstream view of Fusegates and lugs at Otter Brook
Left bottom: Figure 6 – Upstream view during installation
Below: Figure 7 – Downstream view of Fusegates
24 NOVEMBER 2009 INTERNATIONAL WATER POWER & DAM CONSTRUCTION
GATES
Figure 7 shows an upstream view of Fusegates after the instal-
lation works were completed. The final stage was the excavation
works and dyke construction at the left abutment.
CANTON DAM APPLICATION
Project background
Canton Dam is located on the North Canadian River approximately
125km northwest of Oklahoma City, Oklahoma. It is composed of
an earth filled embankment, 4614.7m in length with a maximum
height of 20.7m above the streambed. The top of the dam is at el.
502.3m.
The dam includes a 237.1m wide service spillway at the right abut-
ment with 16 Tainter gates. Each gate is 12.2m wide and 7.6m high.
The spillway crest elevation is at el. 491.6m.
Hydraulic studies have highlighted that the existing spillway is
unable to discharge the new Probable Maximum Flood and that
the dam is likely to fail during major flood events. The discharge
capacity of the existing service spillway is 9600m
3
/sec and the new
PMF studies revealed a total spillway discharge capacity require-
ment of 17358m
3
/sec.
Alternatives investigated
Eight options have been studied to remedy the hydrologic defi-
ciency:
U
Raise the dam by 2.10 m (maintain the freeboard).
U
Raise the dam by 0.4 (eliminate freeboard).
U
Add an uncontrolled spillway.
U
Additional fuse plug auxiliary spillway.
U
Additional Fusegated auxiliary spillway.
U
Additional gated auxiliary spillway.
U
Reduction of flood control storage.
It was found that constructing an auxiliary spillway would offer the
most feasible option.
Option selected
The proposed plan involves the construction of an auxiliary spill-
way on the right abutment containing nine Fusegates at a sill eleva-
tion of el. 490.7m. The excavated material from constructing the
auxiliary spillway would be spoiled below the left embankment to
address the seepage and seismic issues. The rotation of the Fusegates
would lower the spillway crest elevation, increasing the spillway
capacity by 7762m
3
/sec to sufficiently discharge the PMF without
overtopping the dam.
This alternative was selected as it offered a non-mechanical
spillway control system with more economical feasibility on the
construction and O&M costs. The projected path of the auxiliary
spillway is shown in Figure 11.
Proposed Fusegate design
For Canton Dam, a total of nine Fusegates are required, each 9.75m
high and 16.3m wide. The nine Fusegates will fit into the 146.3m
wide auxiliary spillway channel.
The Fusegates will be accommodated on a broad-crested weir
having an upstream to downstream width of 7.2m at the control
section of the emergency spillway, which is at el. 489.5m. With
9.75m high Fusegates, the normal pool elevation (Fusegates crest)
will be set at el. 499.2m. The approach channel will be maintained
at el.488.7m and there will be a 0.5% slope in the return channel
downstream of the Fusegates.
Figure 12 shows the cross section of the broad crested weir that
will accommodate the Fusegates. The Fusegates will be retrofitted
on the flat section of the sill denoted as L.
The Fusegates are semi-labyrinth crested and will be constructed
in reinforced concrete. The inlet wells will be made of stainless
steel. The watertightness will be maintained by installing EPDM
seals between the Fusegates as well as between the Fusegates and
the spillway sill. The photo of an example of the semi-labyrinth
Fusegates is shown in Figure 13.
Intake wells are normally constructed as part of the Fusegate.
Due to the shallow approach channel and wave action, the intake
wells at Canton are gathered within a protective enclosure (called
wet well tower) equipped with a bottom port and conduit to allow
flow to enter.
Pipes embedded in the concrete sill connect individually the intake
wells to the base chamber of the Fusegates. Such configuration
removes the risk of premature tipping because of surface waves. A
similar arrangement was used in the scope of Terminus Dam project
in California.
Figure 8: Satellite view of the Canton dam service spillway
Figure 9: Upstream view of service spillway
Figure 10: Downstream view of service spillway
WWW.WATERPOWERMAGAZINE.COM NOVEMBER 2009 25
GATES
Hydraulic features
There will be five tipping sequences for the Fusegates, where the
tipping elevations range for a water level between el. 500m and
el.500.4m (Maximum Water Level).
Figure 14 shows the flood routing hydrograph of the PMF
through the Fusegated emergency spillway. It should be noted that
the maximum flow to be simulated is 17840m
3
/sec.
The Fusegates are designed to tip consecutively for extremely
large flood events. At Canton dam, there will be no spilling over the
Fusegates crest before a flood that is in excess of 50% of the PMF.
Moreover, the first Fusegate will tip for a flood corresponding to
over 58% of the PMF. This probability corresponds to an inflow
of 10871m
3
/sec.
Combined numerical and physical model study of the auxiliary
spillway
USACE has decided to perform a model study of the proposed
auxiliary spillway in order to optimize the structures and to ensure
that the selected configuration will pass the PMF. The model
study was performed by Alden Research Laboratory in Holden,
Massachusetts. The physical model was constructed as a fixed-
bed, undistorted model with a geometric scale ratio of 1:54, which
was deemed sufficient to reduce scale effects. The PMF flow rate of
17840m
3
/sec prototype scales to approximately 0.9m
3
/sec.
The approach geometry for both spillways was first optimized
by using Computational Fluid Dynamics (CFD) in order to find
an approach channel configuration that can meet the PMF dis-
charge requirements. Advantages of this combined CFD/physical
model approach are that additional model runs can be made at
comparatively lower costs than in the physical model, and many
iterations can be conducted until a satisfactory configuration has
been achieved. The selected final approach channel design would
then be constructed and validated in the physical model.
The model boundaries were selected to represent the reser-
voir over a distance of 457m upstream of the auxiliary spillway
entrance, or approximately 762m upstream of the service spillway,
and 305m along the dam to the left of the service spillway. This
upstream distance is required to accurately model approach flow
patterns to the two spillways, in particular flow around and over
the peninsula-shape outcropping (max el. 499.6m) immediately to
the left of the service spillway. The downstream model boundaries
were selected to represent the flood plain over a distance of 457m
downstream of the auxiliary spillway exit or approximately 914m
downstream of the service spillway. As a result, the physical model
dimensions were 33.5m x 21.3m. The model Fusegates were cast
from a resin, ‘densified’ with tin powder to obtain a conservative
target density of 2.55g/cc for reinforced concrete in order to accu-
rately simulate their geometry, mass and mass distribution and
their resistance to motion.
Figure 16 shows the construction of the physical model with
the existing spillway in the forefront of the photo. Figures 17 and
18 show the production of the Fusegates that will be used for
testing.
LSill crest level
Approach channel
level
Return channel
level
Slope
700,000
600,000
500,000
400,000
300,000
200,000
100,000
0
1642
1641.5
1641
1640.5
1640
1639.5
1639
1638.5
1638
1637.5
Discharge
(cfs)
Reservoir
level (ft)
Inflow
Outflow
Reservoir level
Nb of Fusegates:9
Height: 30.00ft
Width: 53.33ft
0 20 40 60
Time (hours)
80 100 120 140
Max inflow: 632669cfs
Max outflow: 624064cfs
Max water level: 1641.71ft
Below from top to bottom: Figure 11 – Proposed location of the auxiliary
spillway; Figure 12 – The proposed cross section of the weir at the auxiliary
spillway. Right from top to bottom: Figure 13 – Photo of the 7.6m high semi-
labyrinth Fusegate at Jindabyne dam in Australia; Figure 14 – PMF routing
hydrograph of the Fusegated spillway; Figure 15 – Layout of 1:54 scale physi-
cal model at Alden Research Laboratory. Model footprint is 33.5m x 21.3m.
26 NOVEMBER 2009 INTERNATIONAL WATER POWER & DAM CONSTRUCTION
GATES
The physical model was developed to ensure that (i) the PMF is
safely discharged at maximum pool over both spillways and (ii) the
Fusegates after tipping are properly evacuated from the return chan-
nel. It has also been instrumental to derive the basic data used to
assess the stability of the Fusegates and the water feeding conditions
of the wet well and of the inlet wells.
Time schedule
A civil contractor was selected by USACE in September 2008 to
carry out the excavation of the auxiliary spillway, and detailed
design of the project began in July 2009, with completion sched-
uled for February 2010. The concreting works, which includes a
new highway bridge, the broad crested weir, the apron and the
side walls will start upon completion of the excavation works in
early 2011. The overall completion of the project is planned for
early 2012.
CONCLUSION
For dam safety rehabilitation projects, the Fusegate System offers a
wide variety of reliable and cost effective solutions. Thanks to the
versatility of the system, it can be installed on service or emergency
spillways, and it can also be combined with most other spillway
systems either on the same or separate spillways.
Constructing an auxiliary spillway often offers an attractive solu-
tion to severe spillway discharge inadequacy problems as long as a
suitable location is available. The effectiveness of such alternatives
is in many cases enhanced by the use of a fusible spillway control
system designed to fail automatically in case of exceptional floods
in order to release some of the flood water.
The Fusegates will minimize the size of a spillway as compared to
other non-mechanical spillway control systems such as ogee weirs
or fixed labyrinth weirs. They will offer the same benefit of reliabil-
ity and low cost of operation and maintenance as they are designed
to activate only for extremely low probability flood events usually
over half the PMF.
The authors are: Hasan T. Kocahan, Senior Project
Engineer, Hydroplus Inc, US
Russell Wycoff, Hydraulic Engineer, US Army Corps of
Engineers, Tulsa District, US
Martin Wosnik, Senior Flow Engineer, Alden Research
Laboratory Inc, US
This article is based on a presentation given at the 23rd
International Commission on Large Dams (ICOLD)
Congress, held in Brazil in May 2009. For information on
future ICOLD events, please visit www.icold-cigb.net
References
(1) Falvey, Henry T, Treille P. Hydraulics and design of Fusegates. Journal of
Hydraulic Engineering Vol.121, No 7, July 1005 @ ASCE. USA
(2) Hakin, W.D., Cazaillet O. Safety measures adopted to increase spillway
potential at Jindabyne Dam in the Snowy Mountains. ICOLD Conference,
Barcelona, Spain, June 2006
(3) USACE, Tulsa District. Environmental assessment. Canton Lake dam
safety assurance evaluation supplement. Canton, OK, December 2006.
IWP& DC
Left from top to bottom: Figure 16 – construction of the physical model with
the existing spillway in the forefront; Figure 17 – Rapid-prototyped model
Fusegate; Figure 18 – Custom mould to cast Fusegates; Figure 19 – Canton
Dam CFD model configuration
instrumentation, data acquisition and
structural monitoring systems for
dams, tunnels, rockslopes, anchoring
HUGGENBERGER AG, Tödistrasse 68,
CH-8810 Horgen, Switzerland
Phone +41 44 727 77 00
Fax +41 44 727 77 07
Email info@huggenberger.com
http://www.huggenberger.com
The World Leader in
Pendulum Measuring
Systems
· manual: Coordiscope KK84
· automatic: Telependulum VDD2V4
automatic reading for plumb line
Telependulum VDD2V4
manual reading for plumb line
Inflatable Rubber Dams and Spillway Gates from Dyrhoff
Dyrhoff Inc.
354 West Boylston Street Suite 221
West Boylston, MA 01583-2373, USA
T 508-755-0440
F 508-755-9589
moji@aftinc.com
www.dyrhoffusa.com
Dyrhoff Ltd.
Unit 14, Folkestone Enterprise Centre
Folkestone, Kent, CT19 4RH, UK
T +44 1303 246900
F +44 1303 220664
donmason@dyrhoff.co.uk
www.dyrhoff.co.uk
One company, two solutions. Dyrhoff specialises in the design and supply of both
inflatable rubber dams and pneumatically-operated spillway gates. With over 20
years experience, we will offer the best solution for your particular hydro project.
d
28 NOVEMBER 2009 INTERNATIONAL WATER POWER & DAM CONSTRUCTION
CONSTRUCTION
A
t 5464km long, the Yellow River is the second longest river
in China and provides water to over 12% of the country’s
1.3B people. Its reach falls short, however, in chronically
dry Shanxi Province – a region that only receives about
400mm of rainfall annually, and has in recent years experienced
severe droughts coupled with rapid economic growth.
Bringing water to the area has necessitated one of the country’s larg-
est infrastructure projects, spanning over 10 years and 300km of tunnel.
The Shanxi Wanjiazhai Yellow River Water Diversion Project, initiated
in 2001, will transport water from the Wanjiazhai dam to far-reaching
industrial areas in Taiyuan, Pingsuo and Datong.
The diversion project consists of three extensive waterways: the
general main, south main, and north main lines. While excavation
of the general and south lines is complete, construction of the north
main line is still underway.
The latest instalment of the extensive north main line, known as
the Pinglu tunnel, will be one of the world’s longest tunnels excavated
with a single TBM. In July 2009 the 4.8m diameter Robbins double
shield TBM, which is boring the 25.4km long waterway, set ring
number 15,000 – making the tunnel nearly three quarters complete.
PROJECT BACKGROUND
Work on the massive scheme started when China’s project authority
financed construction of the Wanjiazhai concrete dam on the Yellow River
to create the diversion reservoir. The first section of tunnel – the 22km long,
6m diameter feeder tunnel – was completed in the mid-1990s.
Excavation of the south main line began in 1998, under the Shanxi
Wanjiazhai Yellow River Diversion Project Corporation (YRDPC).
The completed south main travels 100km southward from the diver-
sion sluice in the general main at Xiatuzhai. The design allows for a
supply of water at a rate of 20.5m
3
/sec.
Contracts were divided into five lots, with II, III, and V covering
tunnel works. Lots I and IV addressed pumping stations and sections
of buried pipeline. Lots II and III were awarded to the Wan Long JV,
a partnership of Impregilo (48%) and CMC (42%) with the Bureau
4 of the China Water Conservancy and Hydropower Ministry (10%).
Nearly 90km of tunnels were excavated using five TBMs, including
six Robbins double shield machines.
Five TBMs, ranging from 4.8-4.9m in diameter, utilised variable-
speed electric drives and 432mm disc cutters at lots II and III. Each
machine was launched from its respective portal or adit between
December 1998 and February 1999.
Geology along the tunnel alignment was complex and highly vari-
able. Shanxi Province lies on China’s famed loess steppes, consisting
of a soft compacted material, with underlying homogeneous strata of
sandstone, mudstone and limestone. Rock strengths ranged between
120 to 220MPa with little ground water.
A possibility of karst voids in the limestone was also identified, as
well as clay deposits and zones of shale with coal seams. The dangers
of methane gas are also very real in all of the Yellow River tunnels, as
they are situated close to some of the largest coal deposits and high
volume coal mining operations in the world.
Despite variable geology that periodically hindered machine
advance, rates topped 1821m per month and 121m in one day –
world records prior to the excavation of lot V, which utilised the sixth
Robbins double shield machine at high advance rates.
Excavation of lots II and III was completed by 2001. Lots II and III
of the south main line were bored under a strict contractual schedule
of just 48 months, requiring a new type of segment design to aid in
simultaneous lining and excavation.
In the arid project region, where the Gobi Desert is making a swift
advance into the country, and where karstic geology drains much
of the water available, seepage from the long supply conduit must
be minimised. Water flow through the tunnels is gravity-fed but not
pressurised, necessitating a minimum of water loss. Lining for all of
the TBM-driven tunnels consists of specialised hexagonal segments
for speedy and water-tight tunnelling under the unique environmental
circumstances.
Bringing water from Wanjiazhai
US-based company Robbins is helping to hydrate China’s arid Shanxi province in an ambitious
water diversion project. Desiree Williams gives an update on construction at the Pinglu tunnel,
which is set to be one of the world’s longest tunnels excavated with a single TBM
Below left: The 4.8m diameter Robbins double shield is excavating mixed
ground including soil, hard rock, and sandstone; Right: A Robbins double
shield is about 80% complete with China’s Pinglu tunnel, following an inter-
mediate breakthrough at the halfway point in 2008
WWW.WATERPOWERMAGAZINE.COM NOVEMBER 2009 29
CONSTRUCTION
Hexagonal segments have been used on several earlier projects;
however the Yellow River design differs in that it incorporates spe-
cialised sealing gaskets to keep the tunnels sealed off. The segments
are still in use on the Pinglu tunnel, where they are produced in the
city of Shuozhou about 15km from the Pinglu jobsite. At the casting
plant, segments are produced 24 hours a day using steel forms. A
production cycle consists of concrete casting and steam curing for
three hours at 70˚C. The segments are then left in an indoor curing
area for two days.
The so-called ‘honeycomb’ lining system requires a high degree of
precision and strict tolerances. A 1mm offset is specified for the width
and length of each lining section, while a 0.2mm offset is required on
the contour of the perimeter joints. Dimensions are monitored and
production is managed using a programmable logic controller (PLC).
During tunnelling, segments are placed in rings of four elements, in
a honeycomb configuration staggered longitudinally. The non-bolted
lining requires dowels to assist in accurate placement, as well as pack-
ers to negotiate curves and manage alignment corrections. The annu-
lus is then backfilled with pea gravel and subsequently consolidated
with a thin backfill grout.
Each segment is erected within the tail shield, with the invert seg-
ment placed directly on the excavated surface through a slot in the
tail shield. Pea gravel is then injected into the second ring behind
the segment erector in the tail shield. Short dowels are used on the
longitudinal joints, while rod dowels in the zigzag joints behave as
positioning keys. Non-pressurised back-fill grout, used to bolster the
integrity and stability of the lining, is injected into the invert at the
grouting station on the first back-up trailer, about five rings away
from the ring erector. Mortar is injected into the joints between rings,
and full grouting of the crown and sides is accomplished from 10m
behind the end of the back-up system.
EXCAVATION OF THE PIN GLU TUNNEL
The Robbins machine boring the Pinglu tunnel has been operating
in China since 2000, when it was used to bore the 12km long lot V
tunnel on the south main line. During the course of excavation, the
machine set two world records in its size class of 4-5m: best month
(1855m) and monthly average (1352m). Both records still stand.
The Pinglu tunnel connects the north main line to the general
main tunnel. Work includes about 20km of drill and blast tunnels,
excavated in 2005, as well as the 25.4km long TBM-driven tunnel
that will transfer water to the Pinglu, Shuozhou, and Datong
areas. Additional work underway includes about 120km of 4m
diameter buried pipe. Once completed the north main line will
transfer about 22.2m
3
/sec of water through 147km of tunnel and
buried pipelines.
The double shield machine was refurbished after excavation of lot
V, and is dressed with back-loading 432mm disc cutters. A custom-
built, extended back-up system provides sufficient muck removal
and materials delivery capacity for two TBM strokes, allowing for
increased machine performance.
CHALLENGIN G CONDITION S
The Sino-Austria Hydraulic Engineering Co (SAHEC) is responsible
for the Pinglu tunnel, of which about 5km was left to excavate by late
September 2009. The machine has been boring since 30 September
2006 in mixed strata up to 50MPa UCS.
“We’ve had high output in some very challenging ground condi-
tions, from soil to often sticky, medium hard rock, to highly abrasive
sandstone and traces of coal,” said Paul Bargmann, machinery depart-
ment head for Alpine Bau GmbH, lead partner in the SAHEC JV.
Muck removal is by trains of rota-dump muck cars in two tracks
using California switches. The back-up system is equipped with floor
chain movers to shunt the muck cars as they fill. Ventilation in the
long tunnel is generated at a minimum rate of 5.4m
3
/sec by high-
powered fans. The fans, situated at the portal, deliver fresh air to the
tunnel face via 1.4m diameter flexible ducting.
The machine broke through into the Daliang shaft chamber at the
13km halfway point on 1 October 2008, and was refurbished before
starting up again in December. “Since refurbishment the geology has
been fairly stable, though we have had some sections with ingress of
water up to 30 l/sec that slowed progress,” said Peter Enge, project man-
ager for Alpine Bau GmbH. As of September, the machine has averaged
about 26 rings per working day and has erected about 16,700 rings. The
final breakthrough is scheduled for the end of April 2010.
Desiree Willis is a technical writer for The Robbins
Company, 5866 S. 194th St, Kent, WA 98032, US.
www.therobbinscompany.com
Left: In July 2009, the TBM completed its 15,000th ring on the 25.4km long
Pinglu tunnel; Above: China’s Yellow River Diversion Project spans over 300km,
delivering water from the Yellow River to Pinglu, Shuozhou, and Datong
IWP& DC
IWP&DC brings you details on some of the latest project developments
in the dam construction industry
CONSTRUCTION BRIEFS
30 NOVEMBER 2009 INTERNATIONAL WATER POWER & DAM CONSTRUCTION
CONSTRUCTION
Rockfill and
rollers
Winds of change for dam design
Making modifications
THE ALKUMRU DAM and hydroelectric
power plant is located on the Botan Creek within
the boundaries of the city of Siirt in Turkey’s
Southeastern Anatolia Region. The US$500M
project, which currently employs a total work-
force of some 1250 people, is being undertaken
by Limak HES Yatirimlari AS.
The dam is one of seven adjacent dams to be con-
structed on Botan Brook, a tributary of the River
Dicle, and is expected to be completed at the end
of 2010. As part of the project, a total of 18Mm
3
of clay and rockfill is being compacted to form a
finished structure with a height of 134m from foun-
dation level and a crest length of 909m.
Since the project commenced in 2007,
Sweden-based Dynapac, part of the Atlas Copco
Group, has supplied soil compaction equipment
for the application but also provided the neces-
sary follow-up expertise to ensure its correct and
efficient use.
The rollers chosen for this project consist of
three CA512D smooth drum machines and one
CA512PD padfoot version, all with a drum width
of 2130mm. The smooth drum units are being used
for compacting layers of rockfill whilst the padfoot
machine is working on the cohesive clay areas.
The machines are making three or four passes of
up to 200m in length achieving the required 99%
degree of compaction. The CA512 is powered by
a Cummins turbo-charged engine developing 129
kW (173 hp) at 2200 rpm and has maximum oper-
ating weights of 17 and 17.2 tons in smooth and
padfoot drum versions respectively.
Once completed, the Alkumru Dam and the
power plant is planned to produce 828M kWh
of electric power per annum with its 265MW
installed capacity fulfilling part of the Turkish
Government’s long-term plan to reduce the coun-
try’s dependence on foreign power.
THE LATEST DESIGN from UK architect Laurie
Chetwood has been inspired by the hydro industry
and will replicate the work of a dam.
A wind dam is being erected at Lake Ladoga
in the Pitkyaranta District of Russia. Chetwood,
one of 20 architects at Chetwood Associates, is
working with WSP Finland on the project. It will
be capable of harnessing relatively minimal wind
volumes at low speeds to generate power via a
turbine. Upon completion predicted output will
be in the region of 100-120MW/yr.
The wind dam is tethered between two land
masses strategically located to harness the prevail-
ing wind. Of a spinnaker shape, the dam is similar
to the mainsail of a yacht. The funnelling effect of
a gorge or narrow valley concentrates the mass of
air which is captured by the sail and is diverted
through a turbine, generating electricity.
FEM simulation, wind tunnel testing and vibra-
tion analysis are being carried out for a number of
locations in Russia. For more details contact laurie.
chetwood@chetwoods-london.com
THE US BUREAU of Reclamation has awarded
Alpine Diversified an approximately US$2B con-
struction contract for dam safety modifications at
Dikes 4 and 6 at Folsom Reservoir in California.
As part of the USBR’s Safety of Dams (SOD)
programme, modifications will be made to the
two earthen embankments, which are located on
the north shore of Folsom Reservoir. The SOD
programme is an ongoing multi-year construction
programme to perform required safety modifica-
tions at Folsom Dam and Reservoir in conjunction
with the ongoing Joint Federal Project (JFP)
The principal work to be performed under this
contract includes the partial removal of the down-
stream face of both dikes in order to add features
such as filters and drains to control internal ero-
sion. The filters and drains will be constructed
of high-quality imported materials that will be
obtained commercially and brought onsite via
trucks; other local materials to be utilized in this
project were stockpiled on site during previous
work on Dike 5. After the work is completed, the
contractor will place gravel surfacing on the crest
of Dike 4 and asphaltic concrete pavement on the
crest of Dike 6. The contractor will also construct
a permanent, gravel-surfaced maintenance access
road at the toe of the embankments.
Initiation of construction activities will begin in
September and include site preparation, develop-
ment of signage directing the public to established
trail detours, development of the contractor use
areas, and installation of contractor access.
Construction work on both dikes is expected to
be completed by late-summer 2010.
This project will complete the majority of SOD
construction work on the north shore of Folsom
Reservoir, although minor follow-up activities
such as site restoration will still occur.