Adra Diamond Award 2011

8/6/2019 Adra Diamond Award 2011

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DIAMOND AWARD 2011 DEMOLITION OF TONALAS BRIDGE

1- INFORMATIONSOLUCIONES TECNICAS Y

PROFESIONALES A DRA SA DE CV

ADDRESS: Otomies 507

Las Bugambilias

C.P. 37270

Leon Guanajuato

Mexico

Phone: (52) (477) 212 27 97

(52) (477) 212 28 58

Fax : (52) (477) 711

Email. [email protected]

site: www.adra.com.mx

ADRA was founded in 2005. Our main activities are shotcrete and bolts, demolition,concrete sawing and drilling and civil construction. ADRA has been a member of the

CSDA (Concrete Sawing & Drilling Association) since 2007 and is also a member of

the ASA (American Shotcrete Association).

This contribution was made by Eng. Raul Bracamontes on 1 September, 2010.

Should ADRA win a Diamond Award, myself (Raul Bracamontes) and Adriana

Plascencia would attend the award ceremony and would depart from Leon Guanajuato

airport in Mexico.

2- DESCRIPTION

The whole project involved the rebuilding of one of two bridges that cross the Tonolariver in Mexico, following a collapse. The 252-meter-long and 9.5-meter-wide bridge

had collapsed on Friday 17 July 2009 and a new bridge was to be built immediately.

The bridge is located 41 kilometers on the 180 federal highway from Cardenas, Tabasco

to Coatzacoalcos, Veracruz. It is one of the main highways that connects five southern

Mexican states with the center of the country.

Picture of the Tonalas fallen bridge, day of the accident


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The reason for the collapse of the bridge was the deterioration of the foundations, which

gave way under the long-term flow of the river.

The bridge was built in 1958; it had seven superstructures, consisting of segments of

reinforced concrete that each measured 35 meters long. Each of the superstructures were

supported by four pre-stressed beams. Each segment was supported by eight reinforced

concrete pillars 10 meters high (substructures) with one foundation per pile of eightsteel pilots measuring 0.24 inches in diameter. In 1988 the bridge was reinforced with

pre-stressed concrete to satisfy the actual load needs, and in 2003 a new deck slab was

poured.

The project plan was to build a new bridge 30 meters upstream from the original while

contractors demolished the collapsed structure.

The concrete cutting work involved cutting the fallen bridge into pieces between 30 and

40 tons, so that they could be removed from the bottom of the river.

The cutting work on the project consisted of mostly underwater demolition. We planned

to cut the superstructures into pieces (about 18 pieces per structure), each weighing lessthan 40 tons. The piles were also to be cut into eight sections.

The pieces would then be removed by two 60-ton cranes mounted on floating working

platforms called chalans or flexi-boats. The cranes were employed to move the piece

to shore, and once the cut sections were on land they were to be demolished by

hydraulic hammers.

To complete the concrete cutting work as quickly and efficiently as possible, we had

one cutting team of three divers and one sawing and drilling operator, while one support

team of another three divers and one diving coordinator helped us drag all the mud out,

cut the exposed pre-stressed cables and extract the pieces out of the water. A

superintendant was present at all times.

We used a hydraulic power unit, a remote control, a Husqvarna CS2512 cutting head,

directional pulleys and 10-millimeter-diameter diamond wire.

We worked on this job from 1 November, 2009 to 12 august 2010, a total of 160

working days. We removed a total of 4,480 tons of reinforced concrete. Of this quantity,

3,920 tons was cut underwater, made up of five superstructures each weighing 560 tons

and four 280-ton substructures. A further 560 tons was cut above the water, consisting

of two more substructures.

3- COMPLEXITY OF PLANNING AND EXECUTIONWe encountered several problems during the project.

To start, this was the first project of its kind in Mexico and was a complex job to

undertake. All of the sunken sections from the collapsed bridge needed to be removed

from the river because they were acting like dam structures, interrupting the flow of the

river and interfering with local wildlife. Some telephone lines also had to be removed

before we started work, as adequate space was required to use the cranes.


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The main problem, however, was that almost all of the sunken pieces were buried in the

mud and we needed to dig tunnels below them to allow the diamond wire to pass

through for the cuts. These tunnels were made with the help of one landjet to cut the

hard mud and one mud pump to remove it. We dredged about 700 m3 of mud to allow

us to find the pieces and cut them.

Another major problem was that the entire job was underwater with zero to limitedvisibility. The water has a lot of small particles in suspension and the divers were

unable to see more than 15 centimeters in front of them.

All the equipment, scuba station and cutting equipment, was set up in a chalan or flexi-

boat. Our chalan was made of three 3 x 7-meter flexi-boats connected together by steel

wire and 1-1/2 pins.

The cranes were set on other chalan. The extraction chalan, where the cranes were

placed, was made of seven 3 x 7-meter flexi-boats. When the cranes were pulling from

the water, their load capability decreased by about 40%.

The chalans were moved with the help of two diesel winches. One boat took one end ofa cable and tied it to the other side of the river, while another boat took a second cable

and tied it to a different place. The winches pulled and recoiled the cables, allowing the

chalans to move in all directions.

Because we had extremely limited visibility, we needed to perform all the cuts on the

surface were we could direct the pulleys. We set one steel platform at one side of the

chalan to set up the husqvarna cutting head CS2512, the pulleys and the 10-millimeter

diamond wire. We place the chalan over the piece to be cut and tied at four points trying

to avoid any movement to get straight cuts. Sometimes the current was so strong that we

could not avoid movement and made the cut more difficult because with the movement

of the chalan changed tension of the wire.

Our demolition procedure was as follows:

1) Dive to survey and identify the cut sections.Because we were diving in the Tonala River, with zero visibility, the first dive

(made by support and cutting divers) was to have a general view of the piece.

The recognition was made by touching the surface of the piece and describing

the shape before measuring the piece to find how much mud needed to be

removed. The diver wore a Kirby helmet with one infrared camera on the top,

providing full communication with the support personnel at the surface. By

using this technology on the surface we had about 0.5 meters of visibility, better

than what the divers had under the water.


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Picture of the diver

The second dive was more detailed to mark the piece were we need to cut

2) Preparation of the cutOnce the recognition of the piece was complete, the position was confirmed,

how much of the piece was buried, if it was broken or not, if it was on or under

another piece, if it had objects around or under (trees, trash, rubbish, etc.) and if

it was necessary to dredge under it, we were ready to create the cutting plan. We

decided how the cutting should be carried out, including where to start, how to

move the equipment, were to position the chalan and where to start the dredging

work.

Example of cutting diagram of superstructure and substructure No.4, blue lines indicate were

the cut was done, size in meters , red number indicates de weight of each piece in tons

Once the cutting plan was devised, the support divers marked the pieces where

we needed to create an opening (or a window) to allow us to pass the diamond

wire. The team cut all the exterior pre-stressed reinforcements with emery and


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broco torches. To create the windows, support divers broke the concrete with a

pneumatic hammer and then used the broco torch to cut the reinforcement.

Before they used the broco torch it was necessary to create an opening with the

pneumatic hammer to allow air to escape. This would help to avoid any

incidents when they the torch was used to cut the exterior reinforcement, as an

accumulation of oxygen below the slab could create an explosive atmosphere.Some of these windows were used to pass the wire between the pieces. Some

pieces were necessary to dredge the bottom sludge to create a channel were we

can pass the wire for the cut

Use of broco tourchto cut the exterior pre-stressed reinforcements

Almost all the pieces cut had similar sizes and dimensions. There were some

that needed to be cut differently because they were broken or were not stable

enough to move in one large piece.

3) The cutting divers passed the wire through the holes. Due to limited visibility,once the window was made a rope also went through the hole to tie the diamond

wire and to avoid setting pulleys on the piece to be cut. We did all the cutting

work from one single position. We set the equipment at the edge of the chalan

and we put the wire around the piece, cutting from the bottom to the top.


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Picture cutting one structure set up of the equipment

4) Once we started the cut we used one cutting diver to set wedges as needed,while helped us to free the stuck wire.

Picture dive setting wedges

5) Once the piece was cut, the chalan carrying the cranes moved in to extract thepiece. Two support divers tied straps around the piece and the two 60-ton cranes

pulled the piece out the water. This process took around three hours per piece

because the cranes needed to move from the shore to the site were the piece was

located.


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Picture extract of the piece

6) On the shore, one hydraulic hammer broke the cut pieces into smaller sections torecover the steel, before the concrete was loaded onto trucks and taken to its

final destination.

Picture cutting pieces at shore and hydraulic hammer breaking the pieces

In The Scuba station we had:1 compressor 185 cfm, which we used for the pneumatic hammer, landjet, and

air tools.

2 compressor hoses 50' long

2 dive compressor

2 Diving helmets

1 Diving Mask

1 Console Diving

1 Radio communication


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1 Umbilical-video communication

1 Umbilical communication

1 welding current generator

1 Brocco underwater cutting tourch, with Power switch and Gauge and 2 oxygen

tanks

1 Pump type firefighter for dredge the bottom sludge

personal diving equipment (wetsuit, belt, fins)2 Diving Hoses

1 hydraulic unit 8 gal per minute to operate some hydraulics tools like emery

In the cutting station we have:

1 diesel generator 110 kva

1 hydraulic unit

3 gas pumps 1 horse power

1 Husqvarna cutting head CS2512,

8 directional Pulleys

1 lighting tower diesel

The Tonala River changes every day. Sometimes we have two currents, in the morningfrom the river to the ocean and in the afternoon from the ocean to the river. For three

months the river was full of seawater and lots of jellyfish. In some instances, the

jellyfish stuck in the dive umbilical and would burn the divers and support personnel.

Divers wore neoprene, and on the surface we had vinegar and medicine to neutralize the

burns.

The deeper cuts we performed were 20 meters below the surface. Diving time was

limited to less than four hour per dive.

As the new bridge was being constructed next to the fallen one, we needed to coordinate

with the construction company, Puentes y Construcciones S.A de C.V., because when

they were doing the pile driving for the cementation of the new bridge, the sunken

pieces moved with the vibration and put our divers at risk. In addition, there were six

flexi-boats in the river at the same time for several months, requiring close coordination.

Picture of the foundation of the new bridge, the extraction chalan and cutting chalan


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Picture of the extraction of the pieces superstructure 7

Aside from the problems already documented, we suffered one of the worst floods in

recent years due to a severe cold front in November 2009. The fallen bridge structures,

coupled with the increased rainfall, dramatically raised the water level in the river over

a 6 kilometer stretch, and we needed to wait 15 days to start the job.

After the floods had subsided, mosquitoes were a problem. The job location was one of

zones with the most cases of dengue disease in Mexico.

Sometimes the river carried many lilies. When it rained in the mountains, floating plants

and trees were carried down and they accumulated next to the chalans and ropes. On

two occasions, poisonous snakes used the plants and ropes to climb up to the chalans.

We used our boat to move the lilies and avoid accumulations so that it could flow to the

ocean.

We were working in the outdoor conditions, and we needed to deal with weather like

rain, fog, wind and then hot, sunny conditions.

For the two substructures (pile 2 and 3) outside of the water the cutting proceeding was

as follow:

With one working platform we did 16 holes (8 per face) of 6 diameter with the

help of one electric drill to allow us to pass the straps once the piece was cut.


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Picture cutting the body of the substructure 2 the body of substructure 3 was already removed

We set up the Husqvarna cutting head CS2512 on the pile and made the cut the

same way that we were doing it, first we removed the body, when we cut the

foundation, the canes were holding the piece to allow the dive to use the broco

torch and cut the pipes at floor level two per time. Once the pipes were cut we


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started the cutting of the foundations, one piece at a time. Once we cut one piece

the cranes moved to shore to download the piece and break by hydraulic

hammer. The cranes need to pass under the new bridge.

4- INNOVATIVE ELEMENTS

A project like this has never been done before in Mexico. The complexity and

conditions made this a very challenging job. The team at ADRA gained moreexperienced, and we will be bringing more people in to expand our resources.

We use the safest technology for diving. This project had zero accidents. The work

could not be done in other way due to its complexity, working conditions, restrictions,

and the position of the pieces. By using diamond wire we were able to calculate the size

of the pieces and their exact weight according to the crane capabilities. Cutting from

one single position using diamond wire avoided generating excess debris.

Due to the diamond wire do not generates vibration or impact never were put in risk the

remainder structure, even it was broken. We removed a total of 4,480 tons of reinforced

concrete. Of this quantity, 3,920 tons was cut underwater, made up of five

superstructures each weighing 560 tons and four 280-ton substructures. A further 560tons was cut above the water, consisting of two more substructures.

We did not have any environmental impact we didnt disturb the fishermans activities,

we did not disturb wildlife like migratory birds, sea otter, turtles, snakes, lizards, etc.

We never compromised one of the major oil ducts from Cardenas to Coatzacoalcos,

which is located just a few meters from the bridge.

5- QUALITY SPECIFICATIONS

This work had a lot of supervision, the river divides two states and we had to coordinatewith two port authorities one from Veracruz and one From Tabasco. We had to

demonstrate that all our staff were certified to dive, and we had the experience to do this

job. We had supervision from Communication and Transportation Secretary, from

PEMEX (Mexican Oil Company) due to the close position of their main pipe lines, the

constructor company Puentes y Construcciones S.A. de C.V. and the union.

We offered one demolition method without damage the environment. Fast, clean and

quiet. The only limitation was the size of the pieces, and the distance of the pipe lines

Documents

Adra Diamond Award 2011