Sandvik tunneling jumbo’s helping to slash Acapulco commute time

Weekend visitors and residents in Acapulco Bay, Mexico, have long been frustrated by the long journey times they face. Tourists are often bemused to face a long journey time from Juan N. Alvarez International Airport to the Acapulco Bay beaches with congestion being a major problem. This is soon to change as Mexican company, Acatunel SA, is completing a 3.2 kilometer tunnel through the Cumbres de Llano Largo Mountain, using to great effect Sandvik, DT820-SC, and DT1131-SC tunneling jumbos.

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The journey faced by tourists and visitors to Acapulco Bay from the airport is a relatively short journey of 12 km. However, to travel this distance they face a scenic but winding trek on a badly congested road. During peak traffic times the trip around the tip of the Cumbres de Llano Largo Mountain to Acapulco Bay can last over two hours. For weekend visitors, many of them from Mexico City, this can be a serious problem, with the long travel times eating into their leisure time. In fact this has proved to be having an adverse effect on tourist numbers. Local residents, who prove to be more stoical, are also running out of patience with long journey times to and from work.

For all of the above reasons, Guerrero state legislators were concerned about the bottleneck. They wanted to protect their holiday resort area from competing and newer Mexican resorts, as well as unjam the roads for everyday Acapulco residents. In 2013 this resulted in legislators allocating 3,500 million pesos ($213.4 million US) for construction of what will be the longest highway tunnel in Mexico. When finished, this will help facilitate a much shorter and quicker journey time to and from the airport, with the investment also leading to the creation of hundreds of new jobs.

Vitally important project

The Acapulco tunnel is of massive importance to the region. It will dramatically change traffic patterns for the city and surrounding area, slash the commute time from the airport to the Acapulco Bay resorts to a few minutes, reduce vehicular accident rates, and spur new economic development around the bay. The infrastructure project is more than just cutting a subterranean path through the mountain: on either end of the tunnel itself, new interchanges and flyovers will be constructed to smoothly channel tunnel traffic. In all, the new toll road running north from the airport through the tunnel will be 8 km long.

A Mexican construction company, Acatunel SA de CV Consorcio ICA – Carso, successfully bid to drill the 3.2 km tunnel through the Cumbres de Llano Largo Mountain, part of the rugged Sierra Madre del Sur range. Tunneling will run from Cayaco on the south side of the mountain to Brisamar on the bay side. To undertake this arduous project Acatunel engineers are relying on Sandvik, DT820-SC and DT1131-SC tunneling jumbo's to methodically punch through the mountain by July of 2016.

Acatunel brings great experience to the project. It is part of Ingenieros Civiles Asociados (ICA), an international company founded in Mexico City 68 years ago and the first Mexican company to be listed on the NYSE. Amongst its recent projects ICA constructed the 750 megawatt hydroelectric dam and plant on the Santiago River at La Yesca. This was one of Mexico's largest infrastructure projects with the power-generation facility being completed in 2012.

Demanding geology

The ambitious nature of the project means that the sight of traffic flowing through the tunnel is at least six months away. Acatunel teams are still inside the mountain and working their way through it in two 12 hour shifts each day. The tunnel is advancing about 7.2 meters each working day. Some days, the progress does not come easily as the Cumbres de Llano Largo geology has proven to be less than perfect for tunneling. The base of Cumbres de Llano Largo Mountain itself is comprised mostly of granite (made up of quartz, mica and felspar) and basalt. These two abrasive and hard types of rock provide a major challenge to both the drilling teams and their equipment.

One particular problem that drillers are encountering is a great deal of water is being encountered. This must be collected and diverted. Some of the rock is riven with fractures, which lead to collapses and landslides. "What happens is that the ceiling of the tunnel falls in, leaving a hollow upper part over the tunnel," says Miguel Angel Banuet Rodríguez, the project's general supervisor. "This hollow space needs to be filled in with shotcrete or hydraulic concrete so as to make it safe. This causes delays."

Safe and effective tunneling solution

In addition to dealing with geological faults, the drilling crews are working on a downward sloping tunnel floor. This worsens the water issues. It also places a premium on the stability of drilling machines. That is not a problem for the Sandvik Construction DT1131-SC. Though the jumbo drill is fully 18 meters long from its rear overhang to the front of its fully-extended booms, its SAHR fail-safe disc brakes securely lock the machine in place.

Furthermore the DT1131-SC rig is a large rig which further enhances its stability in these arduous conditions. Weighing 44 tons the electro-hydraulic tunneling jumbo unit carries three booms that can excavate an area 18 meters across and 11 meters high. The four wheel drive boom carrier is powered by a 148 horsepower diesel engine, and is carried on 14.00-24PR 28 tires, with dual wheels on the front where the long booms are attached.

As would be expected from such a highly respected company, Acatunel stresses safety for its 350 employees. This was one of the major reasons the company states it chose the Sandvik tunneling jumbo for the Acapulco project. Besides being stable in operation, and pairing a powerful engine with fail-safe braking systems, the DT1131-SC boasts an FOPS certified cabin that insulates its operator against the noise and vibration that comes with drilling through rock. Large window areas surround the operator station so that the operator has full view of the moving, swaying 3,300 kilogram booms as well as any auxiliary personnel working nearby.

To meet the challenge where the drilling boom meets the rock, Acatunel is using Sandvik T38-Hex35-R32 16 foot rods, T38-T38 couplings and RD525 drifter shanks with 48 mm bits. Miguel Angel Banuet Rodríguez says the durability of the Sandvik drilling components is helping his crew hammer its way through the mountain. Acatunel has also utilized Sandvik DX680 and DX700 drill rigs to open the tunnel, and create benching for water drainage within the tunnel.

Supporting the project

To fully acquaint Acatunel engineers with the DT1131-SC, Sandvik's Area Manager, Ari Laitinen, traveled from Finland to Acapulco to provide technical training. Miguel Angel Banuet Rodríguez noted that Laitinen's product support visit was of high value as the Sandvik drill components themselves, stating: "Sandvik is a serious company with the best international quality standards. It always is concerned about serving its clients. The company has never let me down."

Not all Sandvik support for the project must be flown in long distance. Some is as close as the Mexico Sandvik Construction headquarters in Guadalajara. Jorge Duarte, Sales Manager for Sandvik Construction in Mexico, the Caribbean and Central America says, "Guadalajara provides critical logistics support to Acatunel, plus parts and service."

Long line of success

The Sandvik DT series traces its heritage back 50 years to Tamrock jumbo drill rigs. The drills' modular design provides them with flexibility and versatility in attacking a wall of rock. Their ability to steadily power through rock coupled with their optimized cycle times, add-up to productive hours at the head of a tunnel. These and other features are examples of an evolving line of equipment that keeps building on its heritage.

"The booms are cleverly mounted, automatically fixed in parallel positions for accurate hole drilling and engineered to provide the widest possible coverage on the face of the rock," says Jair Gonzalez, Sales and Technical Support Representative Sandvik Construction rock tools and parts, He adds: "When you put Sandvik bits in front of all that (tunneling jumbos and drill rigs), you can expect higher penetration rates, longer bit life, and straighter holes. That's the Sandvik story."

An important landmark was achieved on the 25th October 2015 when the upper connection of the tunnel was finalized. Furthermore, as part of the contract, Acatunel has agreed to return to Acapulco after the dedicated tunnel reaches a predicted vehicular traffic saturation rate of 13,500 vehicles a day. At that point, the contractor will again roll out his tunneling jumbos and drill rigs and construct a second, parallel tunnel through the mountain.