New Bridge Structures and Technologies
Japan is 70% mountainous and is one of the most earthquake-prone countries in the world. As a result, we have developed many world-renowned technologies to prevent damage to bridge structures.
At the planning and design stages, we address future structural maintenance issues including cost effectiveness, length of construction, and environmental impact to achieve the most suitable bridge for each construction site. For example, when we build bridges in mountainous areas, we select a simple style and form that blends well with the surrounding environment, taking practical and economic issues into consideration. To cross rivers or seas, we create long-span bridges employing the most suitable and disaster-resistant designs. In flat areas, we use pre-cast segments or large blocks to expedite construction.
These varied approaches reduce the impact of construction on nearby communities and the surrounding environment. They also help to restrain construction costs. Our major advantage comes from our ability to employ a full range of engineering skills to plan, design and build the best bridge for the site.
This highly engineered bridge (The Shin Fujigawa Bridge) is a steel-concrete composite structure. The arch and vertical members are made of concrete to maintain superior compression characteristics. In contrast, the top girders are made of steel to achieve a lightweight bridge structure. The weight and cost are approximately 40% and 20% less than an ordinary concrete arch bridge respectively.
Compact design is essential to constructing bridges in mountainous areas. Strutted box girders achieve a lightweight superstructure,minimizing substructure elements, resulting in cost effective bridge structure.
Three consecutive cable-stayed bridges on the Ise-Wangan Expressway were constructed in Nagoya’s port zone. The bridge sections are 758 meters, 1,170 meters and 700 meters long, respectively, and form a three-lane expressway. These largescale bridges demonstrate our advanced capabilities.
Advanced Construction Technologies for the Most Demanding Projects
Japan’s mountainous terrain makes tunnel construction a vital part of building smoothly aligned, high-standard arterial expressways. This unique challenge has provided us with the opportunities to accumulate a variety of tunnel construction expertise. To optimize efficiency, we select the most suitable technology for the site’s condition. These technologies include, but are not limited to the pilot tunnel excavation method using a tunnel boring machine (TBM), the New Austrian Tunneling Method (NATM), and the open-cut method.
Tunnel construction sites present a multitude of issues, such as fragile ground, fracture zones, spring water outbreaks and topographical deformations. We resolve each issue by drawing on our most valuable assets – expertise and technological know-how gained from years of experience.
The Hida Tunnel is 10.7 kilometers long, with an overburden of 1,000 meters of rock. Since this configuration precluded the placement of vertical ventilation shafts, we employed a longitudinal ventilation system beneath the roadway surface and another ventilation tunnel along the main tunnel.
This new system automatically selects the most efficient ventilation duct among five for the volume of traffic.
To ensure safe tunnel construction, a TBM is used to bore a pilot tunnel. This pilot tunnel provides geological information and allows groundwater to drain before the tunnel is enlarged.
Once the tunnel structure is completed, the excavated soil is backfilled to restore the terrain to its original profile, minimizing the tunnel’s impact on adjacent residential areas.
Building Large-Scale Earthworks to Harmonize with the Surrounding Environment
Some sections of the Shin-Tomei Expressway have embankments with volumes of 1-5 million cubic meters and maximum heights of almost 100 meters. These embankments are built to resist earthquakes and other natural disasters. To complete these large-scale earthworks reliably and efficiently, various state-of-the-art designs and technologies have been employed. For example, “Zoning Design” is a construction technology that divides the intended embankment area into specific segments for better quality management. Another example is the use of over-sized machinery at earthwork sites, making construction more time and cost-efficient. IT is also used to enhance construction efficiency.
When constructing a bridge foundation in a mountainous area, partial excavation methods are used. These methods are time and cost-effective approaches similar to drilling vertical shafts for tunnels. They enable high-quality construction, while minimizing the impact on the environment.
We have created a special excavation method to reduce the areas of slope cutting. This method preserves the maximum amount of natural vegetation and topography of the remaining area.
Heavy machinery like the 35-ton dump truck and backhoe with a 5 or 12m3 bucket, shown below working on the Shin-Tomei Expressway, enables rapid construction on large-scale earthwork.
Our IT-intensive earthwork construction employs GPS digital mapping that streamlines construction management. This method reduces construction time and cost.
We have introduced “porous asphalt” on our roadway surfaces. While conventional pavement is designed to force water to flow over the surface of the roadway, the porous asphalt layer is designed to allow water to penetrate and drain inside the pavement, securing a void ratio of approximately 20%. This pavement system provides the following advantages:
- Because the pavement forms a thinner water membrane on its surface, there is a higher level of skid resistance on rainy days. This effectively shortens vehicle stopping distances and safer driving under rainy conditions.
- It also prevents hydroplaning and uncontrolled skids.
- The voids in porous asphalt absorb roadway noise.
Driving Comfort and Driver Confidence
- By reducing roadway spray on rainy days, porous asphalt ensures better roadway visibility, and reduces headlight glare.
- It also reduces roadway noise inside the vehicle.
- Containing high viscosity materials, porous asphalt provides improved aggregate bonding, resulting in a 50% lower rate of rutting and a longer lifespan than conventional pavement.
Decrease in Accidents in Rainy Conditions
Porous asphalt paved roadways have experienced a remarkable 80% reduction in roadway accidents.