Challenging weather, difficult sites, and a tight timeframe were no match for Redi-Rock engineered retaining walls.
The Olympic Games are one of sports' greatest spectacles.
They not only showcase the physical prowess of athletes from across the globe, but also shine a spotlight on the lengths that host cities and countries go to upgrade their infrastructure before the festivities.
The $114.5 million Olympic Sliding Centre is an example of a world-class facility made possible by the ingenuity of Precast Modular Block (PMB) retaining walls, despite the stress of tight timelines and additional challenges.
The challenge: getting PyeongChang ready to host the Winter Olympic Games
In September 2011, PyeongChang, South Korea, secured the right to host the 23rd Winter Olympic Games, to be held in 2018.
While PyeongChang had built seven competition venues to boost its chances of securing the games after two previous unsuccessful bids, significant infrastructure improvements still remained.
The planning committee got to work on transitioning the area, with a population of less than 50,000 people, into a collection of venues ready to host the millions of visitors who attend the competitions.
One of the most notable remaining facilities was the Olympic Sliding Centre, which would host the bobsleigh, luge, and skeleton competitions.
The mountain pass of Daegwallyeong, located in Gangwon-do Province and nestled between the Alpensia and Yongpyong ski resorts, was selected for the venue.
Originally named the Alpensia Sliding Centre, the $114.5 million compound would include seven buildings, a 2018-metre (6,620-foot) sliding surface, and occupy 177,000 square metres (44 acres).
The site ranged in altitude from 940 metres (3,084 feet) above sea level to 800 metres (2,625 feet) above sea level.
The rugged, uneven terrain – coupled with the need to provide entrances and exits for thousands of competitors, officials, and spectators – demanded the installation of a series of retaining walls.
The solution: Redi-Rock's precast modular block walls
The general contractor for the project, DL E&C, determined that four retaining walls were needed at the site – along access roads near the starting line, finish line, and finish house, and adjacent to the sliding surface to support the spectator grandstand.
A fifth location – an access road joining the centre to the nearby OCEAN700 resort – included two walls and was added to the project later.
DL E&C, in collaboration with the PyeongChang Organizing Committee for the 2018 Olympic & Paralympic Winter Games, considered many retaining wall solutions.
These included precast concrete panel mechanically stabilized earth (MSE) walls, cast-in-place (CIP) reinforced concrete walls, and Redi-Rock’s precast modular block (PMB) walls.
Ultimately, they selected South Korean manufacturer and installer SEKOROCK Co. to fabricate and install Redi-Rock PMB walls for the five locations.
Redi-Rock was the product choice for several reasons.
Solutions for any wall challenge
The Redi-Rock selection of wall solutions consists of a variety of block sizes and types, allowing for extreme versatility so that an engineer can solve many kinds of problems.
Launched in 2000, Redi-Rock gravity, MSE, freestanding, or hybrid walls have been used in bridges and highways, stadiums and amphitheaters, storm detention and seawalls.
For this project, one product line could meet the engineering demands of each of the five walls, providing uniformity of appearance across the venue.
Quality, durability, and appearance
Redi-Rock PMBs are made with wetcast, air-entrained concrete in a controlled environment.
Compared to drycast blocks, they hold up to harsh freeze-thaw conditions, as well as roadway applications where salt may be used.
In addition, the wetcast concrete provides a rich, textured appearance and can be coloured to suit the site.
Redi-Rock’s blocks can feature multiple textures modeled after natural stacked stone that blends with surrounding structures and landscapes. This gives the finished product a beautiful, native look.
The ledgestone texture with the appearance of stacked stone was selected for the Olympic Sliding Centre.
The need for speed
Redi-Rock was selected for this project in large part because of its shortened installation window, compared to other retaining wall products.
Redi-Rock blocks have front face areas ranging from 0.25-1 square metres (396-1,656 square inches) and the length from the front face can vary between 711-2,440 millimetres (28-96 inches).
With weights from 530 to 2,190 kilograms (1,160 to 4,840 pounds), these blocks are set with equipment such as a small excavator during installation.
Set with heavy-duty equipment, each block covers 0.5 to 1 square metre (5.75 to 11.5 square feet).
The blocks’ large size coupled with the interlocking knob-and-groove technology, which creates strong interface shear connection and consistent wall setbacks, mean the blocks can be dry stacked like giant Lego blocks to meet the timeline constraints.
Less intrusive installation
As well as speed, Redi-Rock retaining wall systems can often be installed in a reduced footprint and with smaller crews.
This can be done by taking advantage of the blocks in a gravity system wall without the need for geogrid reinforcement, which requires more excavation.
Redi-Rock gravity walls can be designed up to 6 metres (20 feet) in height depending on site conditions.
The streamlined size of the crew and smaller overall footprint were a big benefit to the competing construction demands of the site.
The installation: constructing in challenging weather conditions
The challenging construction of the centre began in 2014, steadily progressing until the winter of 2017, when weather threatened its timely completion.
Heavy rain and snow, coupled with one of the coldest winters on record, caused frequent icing on the unpaved mountain paths.
The unreliable roadways prevented the use of typical 25-metric ton construction trucks to transport materials beyond the city of PyeongChang.
Redi-Rock blocks, however, could be transported to the site on smaller 7-metric ton cargo crane trucks better suited to handle the challenging route.
Much of the construction of the Redi-Rock walls took place while additional building was done immediately adjacent, sometimes as close as a few metres.
Of particular note was the installation of tiered gravity retaining walls in the finish line area. These walls provided the abutments (supports) for the raised section of track and anchored soil around the piers of the bridge.
The first wall consisted of 240 solid 1,030-millimetre (41-inch) blocks, stretching for 30 metres (98 feet) by 3.65 metres (12 feet) and covering 120 square metres (1,292 square feet).
The base of this wall rested less than a metre from one of the supports, highlighting how effectively Redi-Rock blocks can be used in limited spaces.
The second wall formed the bridge abutment and was constructed from 140 1,030-millimetre (41-inch) solid blocks, measuring 20 metres (65 feet) long by 3.65 metres tall (12 feet), totalling 80 square metres (861 square feet) in area.
The outcome: a durable centre, still in use today
Ultimately, it was determined the installation of Redi-Rock walls shortened the construction period by approximately five times. It met the challenge of installing high-quality, durable retaining walls in a demanding environment within a short timeframe.
All told, 760 square metres (8,180 square feet) of Redi-Rock large block retaining walls were installed at the Olympic Sliding Centre and the nearby access roads.
The walls totalled 240 metres (787 feet) in length, and the project used 1,450 solid 1030-millimetre (41-inch) ledgestone textured blocks.
The Olympic Sliding Centre – having now reverted to its original name (Alpensia Sliding Centre) – has also managed to avoid the fate of many hastily constructed Olympic venues as it remains in use today.
It now serves as a regional training centre for aspiring bobsleigh and skeleton athletes from across south-east Asia, including Vietnam, Cambodia, Malaysia, and Thailand.
To learn more about solving earth retention problems with Redi-Rock, view the International Design Resource Manual.