2001 JSCE Civil Engineering Design Grand Prize Winner
The rich natural environment of the Shiga Highlands (Shiga Kogen) is located amongst pristine wilderness that is derived from the environment and abundant water sources. When constructing the Shiga Route, we conducted extensive field work and enlisted the advice of experts as much as possible, in order to minimize the impact it would have on the existing ecosystem in the area.
The water that comes from the Shiga Highlands is a crucial resource that is used in a number of ways, such as drinking water for people, a water source for hot springs, and even as a food source for the plants and animals that inhabit the area. The areas that surround these water sources have even been designated as special protection areas within the Joshinetsu Kogen National Park. We chose road designs that specifically avoided impacting these water sources when selecting possible routes for these roads.
We endeavored to preserve the forest vegetation that aligns the route by doing our best to avoid altering any new land, and without any major cross-grade modifications, based on the road alignment along the bedrock of the Shiga Route. In order to protect the environment that the animals of the area inhabit, we wanted to use civil engineering structures to avoid dividing up the area or altering the terrain as much as possible, so we used bridges and tunnels to preserve these animal habitats. Additionally, we installed exclusive animal-use tunnels in numerous places, where dividing up transfer routes was unavoidable. Furthermore, after constructing these transfer routes, we were able to confirm that the animals are using these tunnels.
It is said that it takes anywhere from 100 to 400 years to produce 1cm of topsoil. When starting construction, the first thing we did was carefully collect topsoil for safekeeping, and then hoped to use it as a natural restorative force by relocating it to the newly constructed slopes. Now, trees and shrubs grow along the road slopes, making for a lushly green route. These large-stone retaining walls and topsoil-restored slope formations not only help with preserving vegetation and making for agreeable landscapes, but also function as biotopes for small animals.
The slopes of the Shiga Route were created by applying dry masonry techniques to large stones that were dug out during construction, particularly during tunnel construction. By doing this, we were able to stimulate the breathing of all kinds of trees on the mountain, thus facilitating their growth, and at the same time, we were able to realize a road structure that is in harmony with the natural environment around it.
The three long-span bridges planned for the Shiga Route, as well as other small and medium-span ones, were carefully planned as to alter the abundant surrounding natural environment as little as possible, as well as not to obstruct any existing landscapes.
One of the unified themes in the planning of all these bridges was the adoption of the caisson pile method for foundation work on slopes, as not to alter the natural ground much, and the adoption of steel grinders for the superstructure, which allowed us to select construction methods that minimize the impact to trees and plants in the area. Appropriate column designs for the bridges were considered individually, depending on shape and location.
Moreover, appropriate consideration was given to every detail, including fascia line succession, form adjustments to abutment parts, the processing of auxiliary structures, etc.
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Junisawa Bridge: Octagonal T-Shaped Bridge Column |
Bodaira Bridge: Round T-Shaped Bridge Column |
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Shimizusawa Bridge: Large Beveled Edge Wall-Type Bridge Column |
| Shimizusawa Bridge | Shiga Kogen, Yamanouchi-machi, Shimotakai-gun, Nagano Prefecture |
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| Contractor | Nagano Prefecture Nakano Construction Company |
| Construction Period | 1993-1997 |
