As we introduce Copperhead Strike, here's a look behind the construction fence at what’s already been set in stone – well, reinforced concrete.
The drilling company that created the foundations for Intimidator is back to perform the excavation work for Copperhead Strike. They began digging on June 4 and are scheduled to complete their portion of the project in October.
Caissons (also called “piers”) are created by auguring a deep hole into the ground, and then filling it with concrete. A drilled pier is a deep foundation system, more commonly referred to as “footers," that is constructed by placing concrete and reinforcing steel into a shaft.
Shafts between 15' - 20' in depth are made while temporary steel casings are used to maintain the sides of the drilled excavation. Three drill rigs are digging caissons for Copperhead Strike, supported by two cranes to move drill bits to the rigs:
Approximately 240 caisson holes will be dug for this project. A caisson is designed to rest on an underlying stratum of rock. Carowinds sits above a shelf of granite that spans the entire park. In some parts, this layer of bedrock is as close as 8 feet from the surface. A rock auger bit, pictured below, is used to cut through the granite. Cages protect poured foundation holes and caps cover exposed reinforcing bars (rebar):
Rebar is inserted into and runs the full length of the hole and then concrete is poured into the caisson. When the concrete sets and hardens around the bars, we get a new composite material, reinforced concrete, which works well in either tension or compression - important for handling the positive and negative gravitational forces created by a roller coaster:
It takes concrete about 28 days to reach its full strength and hardness. Cylinders of concrete from every truck are collected and the compressive strength is tested at 7, 14 and 28-day intervals. The inspection of concrete is essential to check for defects that may require repair.
Once caissons are filled with concrete and rebar, the ground around the shaft is excavated into a square and then more concrete is poured to form a "mud mat":
This concrete layer provides a good work area to keep the rebar and formwork clean while preparing to construct a pier cap:
Anchor bolts, which will eventually secure track supports to the pier cap, are precisely positioned. Two surveyors inspect their orientation prior to being secured in reinforced concrete. Once the concrete sets, the anchor bolts' location in the pier cap are checked for a third time. If done correctly, the slots in the track supports will fit over the anchor bolts like a Lego set:
The first two shipments of track supports arrived on August 7 and were transported to the laydown yard - an area outside the worksite where materials are stored until they are needed:
Most of the work to date has taken place below ground level. We are going vertical in late September, when track supports are secured to the anchor bolts. Over the coming months, there will be so much progress to share. Follow along for more inside looks at the Carolinas' first double launch coaster - COPPERHEAD STRIKE!