It is not easy to assess the stability of vertical soil walls reinforced by geogrids during and after construction. This paper describes a unique monitoring system called an ‘optical fibre sensor geogrid' in which an optical fibre sensor is installed within a longitudinal member of a geogrid reinforcement material. The structure of the optical fibre sensor and the measuring method to record strain in the geogrid are described. Laboratory tests were first carried out to assess the accuracy of geogrid strain measurements using the optical fibre sensor method. Optical fibre sensor geogrids were then used to measure the strain in embedded geogrid layers in three reinforced soil walls constructed in the field. The system allows the stability of reinforced soil walls to be monitored continuously during and after construction, and a stability evaluation index to be assigned to the walls based on peak strain readings.

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Although the maintenance work of pavement is often planned based on MCI and FWD data, the repeated damages of pavement are observed at many places. This surface damage of pavement is partly originated by the weakness of subgrade, damage of the filled up ground and ground water. In order to avoid repeated maintenance works of pavement, the condition of earthfill structure should be evaluated by an easy logging technique from pavement surface. The automatic technology for surveys and evaluations of pavement and embankment by using surface wave logging and electric resistivity logging has been proposed. In this study, we tried to improve the pavement life by reinforcing the base course using geosynthetics for degraded pavement on the low embankment with multiple box culverts.

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In recent years, cases where reinforced earth walls were adopted in the construction of expressways are increasing.On the other hand, damages and deformations of these walls have been reported. In this paper we will take up deformations that had developed in a geotextile reinforced earth wall using mudstone. Deformations to this earth wall developed one year after construction, and consequently, the wall was rebuilt. Various tests were carried out at the time of the reconstruction to study the case and find the cause of the deformation. Testing and research showed low relative weaknesses of the wall, such as high water content at the upper wall and around the front face of the upper wall, and low shear wave velocity. From the results, we have concluded that the deformation was caused by water penetrating from the road surface and drainage facilities of the reinforced earth wall backfill. In the testing, we were able to confirm the validity of the surface wave exploration and that the strength of the geotextile reinforcements used in the deformed area had lowered.

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