HRBT TIMELINE

An overview of the complex planning, engineering and construction progress behind the new HRBT twin tunnels.

NORTHISLAND

TUNNELING PROGRESS

SOUTHISLAND

HAMPTON ROADS BRIDGE-TUNNEL EXPANSION PROJECT

New Tunnels

TUNNEL

norfolk

HAMPTON

NORTHISLAND

ISLAND EXPANSIONThe island was doubled in size to accommodate the new tunnels.

JET GROUTINGThe ground is injected with a stabilization fluid to strengthen the soil for the tunnel approaches.

Fall 2020 – Summer 2021

Winter 2022 – Fall 2023

TBM RECEIVING PITThe TBM will break through the receiving pit after completing the first tunnel.

Spring 2022 – Fall 2023

TBM TURNAROUNDIt will take about 6 months to turn the TBM around to begin the second tunnel.

Winter – Summer 2024

BACK

NORTHISLAND

A five-thousand-ton barge slowly cuts through the waters near the City of Hampton, making its way towards the North Island of the Hampton Roads Bridge-Tunnel. On board, six-and-a-half-ton stones from a quarry in Maryland, now destined for life in Virginia as part of the HRBT Expansion. As the stones arrive, crews measure them against “witness stones,” making sure they are the correct size and shape for placement. Finally, a grapple grabs a stone and gently swings it into place, before workers key and lock it in position like a 20-thousand-ton jigsaw puzzle. And so goes the North Island Reclaimation (NIR), a critical portion of the larger HRBT Expansion Project. The NIR will expand the island’s current footprint by about 16 acres and lay the foundation for future elements of the project. The completed NIR will provide space for a receiving pit for Mary, the Tunnel Boring Machine (TBM), as well as an approach roadway for the new, twin tunnels.

Piece By Piece – How To Build An Island

ISLAND EXPANSION

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NORTHISLAND

ISLAND EXPANSION

While it may seem like simple work, the job is extremely complex. Beyond what is visible from the surface there is a larger rock footprint sloping further underwater, carefully designed to support and protect the island interior. The reclamation process includes construction of the bund, or core perimeter layer, as well as an outer, or armor stone layer, to protect the structure from the surrounding waves and currents. From here, several layers of sand are compacted to fill the expansion. It’s a lot of work only to then excavate a portion of this newly expanded island to accommodate the TBM receiving pit. Yet building the full island expansion with the precise soil mix and compaction is necessary in order to maintain the structural integrity as the walls of the receiving pit and new tunnel approaches are constructed. Wind and waves can batter or change artificial islands over time, so it is important to make sure each portion of the NIR is executed correctly, from design to materials. This will help Keep Virginia Moving for at least the next 100 years.

Piece By Piece – How To Build An Island

ISLAND EXPANSION

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NORTHISLAND

ISLAND EXPANSION

Crews are constructing a receiving pit on the North Island. Just as the name implies, this pit is created to “receive” Mary the TBM when she completes her journey from the South Island. At one-third the size of the TBM launch pit on the South Island, the TBM receiving pit is just one circle. Much like the process for the TBM launch pit, slurry walls form the perimeter of a circular receiving pit. After a capping beam is installed to stabilize the receiving pit, crews will excavate to a depth of 75 feet. A concrete slab will support the weight of Mary and form the base for future roadway. When Mary “breaks through” into the receiving pit, she will have completed the first tunnel. In the receiving pit, Mary will be turned around and will start her trek back to the South Island as she bores the second tunnel.

TBM Receiving Pit

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NORTHISLAND

ISLAND EXPANSION

TBM will break through on the North Island and then be partially disassembled and then placed on a turntable section by section to be turned around and start boring the 2nd tunnel.

TBM Turnaround

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NORTHISLAND

ISLAND EXPANSION

Jet grouting, or pressure grouting, is a method of soil stabilization which involves the high-pressure injection of a stabilizing fluid into the subsoil to stabilize ground conditions within the project site. Jet grouting is used to reinforce the surface to make sure it is stable enough to withstand the weight and size of Mary and to facilitate "steering" the TBM.

JET GROUTING

TUNNEL

TUNNEL BORING MACHINE (TBM)Mary the TBM was manufactured in Germany and shipped to the US.

Fall 2020 – Fall 2021

TUNNEL BORINGThe TBM will launch for the South Island excavating and building the first tunnel to the North Island, then turn around and create the second tunnel.

Winter 2023 – Summer 2025

TUNNEL SEGMENTSReinforced pre-cast concrete tunnel segments are being manufactured in Cape Charles and will be barged to the South Island for installation by the TBM.

Spring 2021 – Ongoing

BACK

TUNNEL

ISLAND EXPANSION

The Tunnel Boring Machine (TBM) is the machine to be used to bore new twin tunnels next to the existing Hampton Roads Bridge-Tunnel. Hampton Roads Connector Partners (HRCP), the project's joint construction venture, awarded a contract to Herrenknecht of Germany for design construction of the TBM. It took approximately 14 months to build the 46-feet-high machine, approximately four months to ship it from Germany, and another four-to-five months to assemble the TBM on the HRBT's South Island. The TBM is longer than a football field. As you can see from the picture of the TBM's cutterhead (pictured to the right), the machine is about the height of the HRBT Project Office, which is a four-story building. The price tag for the TBM alone is $101 million which includes construction, shipping and assembly costs.

TBM (Tunnel boring machine)

BACK

TUNNEL

ISLAND EXPANSION

The TBM will launch from the South Island (Norfolk side), and bore (work) at a rate of about 50 feet per day until it reaches the layer of soil known as the Yorktown layer, approximately 50 feet below the current tunnels. The TBM excavates the tunnels with a circular cross section through the soil. The process for both tunnels will take more than two years. Built specifically for the HRBT Expansion Project, the TBM is a central component of the project.

TBM (Tunnel boring machine)

BACK

TUNNEL

ISLAND EXPANSION

The existing ten tunnels in Hampton Roads are immersed cylinders that sink into holes in the waterway bottom. Advances in tunnel technology make the bored-tunnel approach possible for the expansion project. The method has fewer environmental impacts and does not disrupt Navy, marine, or commercial traffic in the busy federal channel.

TUNNEL SEGMENTS

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TUNNEL

ISLAND EXPANSION

The finished concrete tunnel segments, over 150 at a time, will be transported by barge down the Chesapeake Bay to the South Island. Once on the island, the segments will be transported into the tunnel using specialized vehicles. The segments are fed onto a conveyor inside the TBM where a vacuum erector lifts, turns and fits each segment into place.As Mary works to excavate the soil, she will place nine precast concrete segments into a ring that becomes the walls of the tunnel. Mary advances by pushing 54 hydraulic thrust jacks against the newly completed ring of precast concrete segments, leaving a perfectly circular tunnel in her wake.Mary will place 21,492 tunnel lining segments, each weighing 12 tons. She will erect each segment one by one to form a total of 2,388 rings of nine segments each, leaving a perfectly circular tunnel in her trail.

TUNNEL SEGMENTS

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TUNNEL

ISLAND EXPANSION

The new twin tunnels will be constructed using a massive tunnel-boring machine, or TBM, with a rotating cutting head that excavates soil along the tunnel’s path. As the cutter head moves through the soil, concrete liners are set in place by a rotating vacuum powered lift, creating the outer shell of the tunnel. A significant advantage of this construction method has a significantly less environmental impact to marine wildlife than with the immersed-tube approach, which would have required dredging a deep, mile-long trench across the Hampton Roads waterway. Because the tunnel-boring machine excavates from beneath the riverbed, this technology essentially eliminates disruption to commercial and military shipping in one of the nation’s most important navigation channels. The new tunnels will be approximately 50 feet deeper than the current tunnels and each will be 8,000 feet in length.

TUNNEL BORING

BACK

TUNNEL

ISLAND EXPANSION

The HRBT Expansion Project will be VDOT’s first bored tunnel and only the fourth and fifth bored tunnels in the United States. Although the immersed-tube method was used to construct all ten of Hampton Roads’ existing crossings –from the original Downtown Tunnel in 1952 to the new Midtown Tunnel in 2016 – recent technology advances have now made bored tunnels feasible in the region’s soft soils. Preliminary construction work will began in mid-2020 with a 65-foot pit to be excavated on the South Island to accommodate the TBM launch. The TBM will tunnel towards the North Island (Norfolk to Hampton) completing the first tunnel in roughly one year. It will take about four months to turn the TBM around and another year to bore a parallel tunnel back to the South Island.

TUNNEL BORING

SOUTHISLAND

QUAY DOCKA temporary dock was built so that tunnel segments can be unloaded from barges and lowered into the launch pit to the TBM using a gantry crane.

Fall 2020 – Summer 2022

SLURRY TREATMENT PLANT (STP)The STP, manufactured and shipped from France, is used to separate the slurry from the soil that is excavated by the TBM.

Spring 2021 – Fall 2022

TBM LAUNCH PITSlurry walls were placed around the perimeter of a tri-cell which was then excavated to a depth of roughly 65 feet. A concrete base slab and headwall were installed to support the TBM operations.

Fall 2020 – Fall 2022

TBM REASSEMBLY170 pieces of Mary the TBM were reassembled on the South Island in the launch pit.

Spring 2022 – Fall 2022

CONVEYOR BELTA conveyor belt system was installed to move excavated soil from the STP to waiting barges for removal to approved disposal sites.

Summer 2021 – Fall 2022

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SOUTHISLAND

ISLAND EXPANSION

In order to get Mary, the TBM, tunneling, she needs a good start. The HRBT Expansion Project team has been working for months to prepare a home for Mary’s launch from the South Island. The launch pit is constructed in three “cells,” or overlapping circles that form its peanut shape. The first step to prepare the TBM shaft is the installation of the slurry walls, 4' think and 185' deep concrete panels which form the perimeter of the launch pit. Next, crews added struts and a capping beam around the top of the shaft to provide support and stability to the structure as the launch pit was excavated.Since November, crews worked around the clock to excavate the launch pit for Mary. The team uses heavy equipment to dig, including a specialized machine called a teledipper, which has a telescoping arm to remove excavated soils from the pit into an awaiting dump truck for removal. The goal is to excavate to a depth of over 80 feet at the front of the launch pit to accommodate Mary’s cutterhead and the trailing gantries that support the tunnel boring operations. This equates to roughly 120,000 cubic yards of soil that were excavated in preparation for Mary’s journey.

TBM Launch Pit

Preparing the TBM launch pit

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SOUTHISLAND

ISLAND EXPANSION

Once the soil is removed, the slurry walls that form the perimeter of the launch pit are smoothed, and crews install a specially engineered waterproofing system to prevent groundwater from seeping into the pit. This system, comprised of geo-textile material, waterproof PVC membrane, waterstop barriers and seals, is installed on the walls and floor of the shaft.After the waterproofing is complete, crews place a 7- to 9-foot thick concrete base slab that will support Mary’s weight while at the same time providing added weight to counteract buoyancy of the launch pit. While it’s hard to imagine at nearly 4,700 tons that Mary could float, the water pressure underground pushes upwards at a force of up to 5,000 pounds per square foot.

TBM Launch Pit

Preparing the TBM launch pit

Finally, a concrete headwall is installed at what will become the opening of the new tunnel. The TBM will drive and cut directly through the headwall to start her journey. The headwall provides a perpendicular surface ensuring equal pressure across the face of the cutter head to provide traction as Mary starts tunneling. A lot of preparation is needed to get Mary ready, and the reward will be watching her work in the coming year as she constructs VDOT’s first bored tunnel.

FUN FACT:The amount of soil excavated for the launch pit would fill up Harbor Park Stadium to a depth of 8.25’

BACK

SOUTHISLAND

ISLAND EXPANSION

A quay dock is a specially designed dock where barges will deliver the tunnel segments. It’s outfitted with a gantry crane that can take the segments off the barge, move them across into Cell 1 of the launch pit and then lower the segments into the pit to the TBM.

QUAY DOCK

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SOUTHISLAND

ISLAND EXPANSION

Another important component of the HRBT Expansion Project is Mary’s partner in progress, Katherine, the Slurry Treatment Plant (STP). The STP is an equally important part of the construction process, ensuring that the sand, clay and other by-products of the tunneling process are removed from the construction area in an efficient, environmentally responsible manner.You can imagine Mary will excavate a tremendous amount of soil as she digs her way under the seabed. The estimated total volume will be around one and a half million cubic yards of material. This output is often called “spoil” and includes coarser sands, clay and other fine silt materials. Slurry, an engineered mixture of bentonite clay and water, is added to the excavated material to help facilitate pumping and removal. As the TBM tunnels forward, spoils are pumped to the surface through a 22-inch steel pipe to the STP on the South Island.

SLURRY TREATMENT PLANT (STP)

Katherine

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SOUTHISLAND

ISLAND EXPANSION

At this plant, the excavated soil mixture passes through a series of rotating screen filters (called “trommels” and “cyclones”) with progressively smaller mesh sizes to separate particles and finer sands from the slurry. The recovered slurry is reused to feed the TBM, and the remaining spoils are processed through a filter press to squeeze out the residual water. Katherine, the STP, was named in tribute to the pioneering African-American mathematician Katherine Johnson, whose pivotal contributions to NASA’s space- flight program were featured in the motion picture “Hidden Figures”. Just like their real-life namesakes, Katherine the STP and Mary the TBM are a perfect team.

SLURRY TREATMENT PLANT (STP)

Katherine JohnsonMATHEMATICIAN

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SOUTHISLAND

ISLAND EXPANSION

The conveyor belt is designed to remove the soils that are excavated by the TBM. After it’s processed at the slurry treatment plant, the remaining soil is placed on the conveyor belt which takes it to the barge for removal to the designated disposal sites.

CONVEYOR BELT

FUN FACT:It is estimated that the TBM will excavate 1.5 million cubic yards of soil – or enough soil to make more than 840 Mt. Trashmores

BACK

SOUTHISLAND

ISLAND EXPANSION

Mary, the Tunnel Boring Machine, was manufactured in Germany before being disassembled for shipment to the United States. Mary arrived in the U.S. in November 2021 in 140 bulk pieces and 30 containers of parts. Before Mary could be reassembled, special accommodations had to be prepared. Crews have been working for months to excavate the launch pit on the South Island where she will start her tunneling journey. At 4,700 tons, it’s not feasible to move Mary around once fully assembled. While some components can be pre-assembled, the majority of Mary’s assembly must happen inside the launch pit. As crews are busy making the final touches on the launch pit, pieces of the TBM have been welded together to expedite reassembly in the launch pit. At Mary’s face is the cutterhead with a striking design reflecting the Hampton Roads regional flag. The cutterhead features numerous tools called disc cutters, bits, and scrapers that break up the soil. Behind the cutterhead and housed within the shield, Mary’s main drive includes the motor and bearings that move and rotate the cutterhead. Behind the shield comes the tailskin, which is a seal designed to prevent water from seeping in as the TBM works to install the tunnel segments. These three components make up the TBM shield. Behind the shield are four trailing gantries. These movable frameworks provide supporting equipment and services needed for tunnel operations.

TBM REASSEMBLY

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SOUTHISLAND

ISLAND EXPANSION

The first gantry houses the control room for the TBM operator, as well as the oil for the hydraulic station. The second gantry holds the substation that will distribute power across all components of the TBM. The third gantry contains the conduits and pipes for the electrical, air and water utilities needed to operate the TBM. The fourth and final gantry supports the extension of all cables, wires and pipes as the TBM advances. As Mary journeys to the North Island to form the first tunnel and then back to the South Island for the second tunnel, crews will need to extend connections up to 16,000 feet. These extensions carry power, air, water and slurry from the South Island to the TBM.Mary is a complex piece of industrial machinery specifically designed for the HRBT Expansion Project. As she tunnels, crews will perform preventative maintenance including changing out the cutterhead tools as needed, to ensure that Mary stays in shape for peak performance.

TBM REASSEMBLY