The Sarushima Battery Ruins located in Yokosuka Port has been over 130 years since its completion in 1884, and deterioration has been observed in the brick structures. Yokosuka City conducted a survey with Asano Taisei Engineering Co., Ltd. in order to restore and preserve historic sites and ensure the safety of visitors to Sarushima, which is also used as a city park. We used 3D laser scanners, UAVs, etc. for the investigation.

Recently, a water spring was observed in the west brick wall of the fortress tunnel. A depression is formed on the west side of the tunnel. It was thought that rainwater may be stagnant in this depression and spring water may be flowing into the west brick wall. The investigation included three-dimensional laser scanner displacement measurement, structure inspection, core extraction, lining thickness, wall thickness and back cavity investigation, topographical and geological exploration, and maintenance methods for preservation were considered.

As a result of the investigation, the results of laser scanner measurements are illustrated. For preservation consideration, developed, cross-sectional, and elevation drawings of the tunnel, ammunition depot, and habitat cover were created. The results of the structural inspection survey were recorded as a damage development map in the development map created this time. Spring water was observed in two holes drilled in the defective side wall of the horizontal part of the tunnel, but the water stopped flowing after about 5 to 20 minutes, which is thought to be caused by water stagnant in the depression.

Based on the survey results, it is recommended to carry out routine long-range visual inspections focusing on water leakage conditions and areas at risk of spalling, regularly check for changes in deformation over time using a 3D laser scanner, and check for damage progress through close-up visual inspections.