RRR-A

Reinforced soil bridge abutment & bridge

Conventional simple girder bridges are often not cost-effective while vulnerable to disasters by earthquakes, floods etc. due to a number of technical deficiencies (★) shown below:

RRR-A technology allows the construction of reinforced-soil bridge abutments that alleviate the above-mentioned problems (★).
RRR-A comprises two sub-technologies:

1) RRR GRS Bridge Abutment
2) RRR Reinforced Soil Integral Bridge
a) RRR GRS Integral Bridge to construct new bridges
b) RRR-NRS lntegral Bridge to reinforce existing old simple girder bridges

1) RRR Geosynthetic-Reinforced Soil (GRS) Bridge Abutment

This type of abutment supports one end of a simple girder by using a fixed bearing arranged on the top of the RC full-height rigid (FHR) facing that is firmly connected to geogrid layers reinforcing the backfill.

2) RRR Reinforced Soil Integral Bridge

This type of bridge structurally integrates both ends of a simple girder to the top of RC vertical walls:

a) RRR GRS Integral Bridge to construct new bridges

b) RRR-NRS lntegral Bridge to reinforce existing old simple girder bridges

a) RRR GRS Integral Bridge

The backfill is reinforced with a number of geogrid layers that are firmly connected to the full-height rigid (FHR) facing. Both ends of a continuous girder are structurally integrated to the top of a pair of FHR facings. In this way, the girder, the FHR facings and the reinforced backfill are all integrated. As a result, RRR GRS Integral Bridges become much more stable than conventional simple girder bridges, in particular against severe seismic loads.

As the bearings are not used to support the girder, the top of the FHR facings is laterally displaced cyclically by seasonal thermal expansion and contraction of the girder. This may result in settlements in the active zone of the backfill and the development of elevated passive earth pressure. With RRR GRS Integral Bridge, however, as the backfill is reinforced with geogrid layers connected to the FHR facings, these phenomena are effectively restrained and associated harmful problems do not take place. The development of a bump at the back of the abutment due to settlement of the backfill caused by traffic loads and seismic loads is also effectively restrained.

The girder and FHR facings become slender due to structural integration. Moreover, as the FHR facing and girder are constructed after the deformation of supporting ground and backfill has taken place, pile foundations becomes unnecessary.

All these features make RRR GRS Integral Bridge highly cost-effective in construction and maintenance while very stable during long lifecycle service and against severe natural disasters by seismic loads and scouring and over-flow by floods and tsunami.

b) RRR NRS Integral Bridge

This technology reinforces existing simple girder bridges maintaining the service of the bridge while not constructing temporary detour bridges and approach roads.

Firstly the existing girder is propped and the backfill of the approach fill is reinforced by installing large-diameter nails from, and connected to, the RC retaining walls of the abutments. The girder is then structurally integrated to the top of the RC retaining walls. As a result, the whole bridge system is fully structurally integrated. The integrated bridge exhibits very high stability against seismic loads, floods and tsunami.

By removing the bearings for the girder, the top of the RC retaining walls of the abutments are laterally displaced cyclically by seasonal thermal expansion and contraction of the girder, which may result in settlements in the active zone of the backfill and development of high passive earth pressure. With RRR NRS Integral Bridge, however, as the backfill is reinforced with nails connected to the retaining walls, these phenomena are effectively restrained. In particular, backfill settlement by long-term traffic loads and seismic loads and associated development of bump at the back of the retaining walls are effectively restrained.

The simple girder of an existing old bridge is stabilized with a propping extending from the abutment.

The backfill is reinforced with large-diameter nails connected to the RC retaining walls of the abutments

The girder is integrated to the RC retaining walls of the abutments by casting-in-place concrete