Monitoring of supporting soil during construction of 330-m supertall building on spread foundation in Tokyo

The Mori JP Tower is a newly constructed 330-m supertall building located in Tokyo, Japan. As the tallest building in Japan, as of 2025, it is directly supported by the Kazusa Group, which is a Pleistocene stratum with a shear wave velocity of more than 400 m/s via a spread foundation. The building was constructed using a combination of the bottom-up and top-down methods. Owing to the unprecedented scale of buildings in Japan and the complexity of the construction process, the supporting soil may exhibit complex behaviors that are difficult to predict accurately. Therefore, it is crucial to monitor the movement of the supporting soil to ensure construction quality. This paper reports on the monitoring methods, vertical displacement, and changes in stiffness of the supporting soil during the construction process. The following results were obtained: (1) The supporting soil at the center of the tower showed a rebound of 35 mm by the end of the excavation and then settled 42 mm by the end of the construction. (2) The vertical displacement of the supporting soil was affected by changes in the groundwater level. (3) The shear wave velocity of the supporting soil showed a confining-pressure dependency, particularly in the sandy sand–clay mixture strata. (4) The rebound and settlement during the construction, as well as the confining-pressure dependency of the soil, were generally in line with previous reports.