We have completed an epochal and new style segment joints “JicLoc” and ShuLoc” for RC segments for shield tunnels that realized a shorter construction period and compact size at the same time.
Product features: JicLoc
While enhancing the function to absorb the errors in position and posture when constructing the segment, the coupling load previously required to be 3tons was reduced to about 0.03ton to improve the assemblability of the segment. It also has a lock release function in case of incorrect joining.
Product features: ShuLoc
The conventional joint composed of male and female joint, has been simplified to one type. Furthermore, by changing from conventional casting production to forging production, we have achieved to improve strength and mass productivity while realizing miniaturization of 36% or more by weight.
*1 What is a Shield Tunnel?
It is a tunnel for highways, high-speed railways, sewers, etc. constructed by the shield method.
It is constructed by drilling a tunnel with a cylindrical device called “Shield machine” with a rotating blade at the front end, while jointing a block-shaped outer wall called “Segment” at the rear of the machine.
*2 What is an RC (reinforced concrete) Segment?
It is a block-shaped wall member made of reinforced concrete used in the shield method.
Each segment is in the shape of a circular arc block obtained by dividing a cylinder both in the axial and the circumferential direction. It is pre-manufactured in the factory and assembled while being joined to each other on site. In some cases, the unit weight exceeds 10 tons.
*3 What is a Segment Joint?
It is a joint member that tightly connects RC segments together. It is required to have the followings: Strength that does not loosen after fastening, Ability to support and withstand the load applied to the tunnel from the super heavy segment and surroundings, Shortening of work hours due to the simplified fastening work, Function to absorb the errors in the position and posture between segments.
There are 730,000 road bridges nationwide, out of the social capital. Among them, the percentage over 50 years after the construction will reach 60% in 10 years. (according to the published materials by the Ministry of Land, Infrastructure, Transport and Tourism).
The total length of a highway bridge using reinforced concrete floor slabs, which requires immediate large-scale renewal, is approximately 230km. For this reason, NEXCO East, NEXCO Central and NEXCO West plan to replace these floor slabs with a cost of approximately 1.65 trillion yen altogether.
(According to the presentation materials by NEXCO 3 companies)
On the other hand, how to construct a highway bridge using the current reinforced concrete slab, is to pre-manufacture reinforced concrete floor slab in the factory, then to arrange them at regular intervals in the site of construction, and lastly the floor slabs are connected to each other by placing "filling concrete" at the intervals.
This work requires not only a lot of manpower and heavy equipment, but also a huge amount of time especially for positioning the floor slabs. For example, under the current situation, it takes 30 minutes or more just to arrange one floor slab at regular intervals.
New joint “VanLoc” for replacement floor slabs
"VanLoc" has realized an epoch-making construction method using precast PC floor slabs to eliminate filling concrete, which has been nowadays considered unavoidable.
It is an innovative joint that can complete the floor slab connection and floor slab misalignment just by tightening one single bolt.
Features of "VanLoc"
●The padding width between floor slabs can be made as small as possible, eliminating bar arrangements and concrete placements in the padding section.
●Because of both connecting floor slabs and correcting floor slabs misalignment with just one bolt, it takes a few minutes to install the floor slabs. Positional misalignment can be corrected in three directions: the bridge axis direction, the direction perpendicular to the bridge axis, and the vertical direction.
●"VanLoc" makes it possible to absorb the level difference between adjacent floor slabs in order to respond to changes in cross slope.
Development status of "VanLoc"
●Development as a product has been completed, and we are currently working on the development for mass production.