Akyazı / Sakarya
Site Conditions
- The existing bridge approach embankments, constructed using wrap-around faced geogrid-reinforced soil wall technology and already serving vehicular traffic, had longitudinal grades of approximately 7%–8.5%. For driving safety, these grades were required to be reduced to 5%.
- The local ground profile consisted of highly compressible soil layers extending to depths of approximately 35–40 m.
- Additional fill had to be constructed over the existing approach embankments in order to reduce the longitudinal grade to 5%.
- A project-specific solution was required to prevent the additional stresses generated by the new fill from adversely affecting both the internal stability of the existing geogrid-reinforced approach embankments and the external stability of the system.
Designed Solution
- Controlled partial excavation and benching of the existing geogrid-reinforced soil embankment to satisfy bearing capacity and settlement criteria for the foundation soil.
- Construction of the additional bridge approach fills using geofoam block technology to achieve a 5% longitudinal grade without imposing substantial additional stresses on the underlying ground and existing reinforced soil system.
- Implementation of a hybrid solution combining two different geotechnical technologies.
Advantages of the Applied Geotechnology
- The additional fill required to reduce the longitudinal grade could be constructed without adversely affecting the internal stability of the wrap-around faced geogrid-reinforced soil walls or causing external stability problems such as bearing capacity failure, excessive total settlement or differential settlement.
- The project was completed within a substantially shorter construction period compared with conventional construction methods.
- The solution provided a more economical alternative in terms of overall project cost compared with complete removal of the existing reinforced soil approach embankments, ground improvement of the foundation soils and reconstruction of the approaches using reinforced soil technology.
Performance Under Service Loads
- A comprehensive instrumentation program using settlement plates was implemented.
- Periodic measurements were collected for one year after the roadway was opened to traffic in July 2021.
