4:30 PM - 4:45 PM
[HRE12-05] Collection of geological information in urban areas and research methods
Keywords:Geo-Informatics, Osaka, Database , subsurface geology
In urban areas, it is difficult to carry out a geological survey, and in many cases, it is difficult to secure a survey site even for a boring survey. Therefore, there is a method of creating a database of boring survey data and utilizing it. In the Kansai region, geo-informatics database has been accumulated over the past 30 years or more. At present, the Kansai Geo-Informatics Network (KG-NET) has been formed and is carrying out activities.
Within KG-NET, we focused on each region and conducted a study with the aim of showing examples of utilization of these data. The results of this research were published in the New Kansai Ground Series, covering the Osaka Plain, the Kyoto Basin and so on. In each region, the cross-sectional diagrams of representative subsurface ground, geological stratigraphy, characteristics of sediments, relationships with geological structures, etc. are summarized, and engineering characteristics are also summarized. Therefore, it is used to explain the outline of the geological survey work in the relevant area, to confirm the target strata during the survey, and to plan the survey.
In addition, in areas including harbor areas such as the Osaka Plain, the distribution of seafloor clay layers basically associated with sea level changes is characteristically distributed. On the other hand, in the inland area, the characteristics of the river sediment and hinterland reflecting the rock characteristics of the exposed basement rock were clarified, and the ground characteristics of each region could be summarized. A feature of these reports is that they summarize not only geological content such as geological depositional environment and sedimentary age, but also engineering soil properties and physical properties. The characteristics of the area will be clarified by side-by-side comparison of what has been clarified by the standard boring survey with the data registered in the surrounding boring database. By using this kind of work to understand the stratum distribution and sedimentation conditions, it became clear what kind of sedimentation conditions the geological features with a high risk of construction trouble are distributed in, and points to be noted have also been clarified. For example, the 'sand' layer deposited near land and in areas with moderate currents in Holocene marine sediments deserves attention. The sediments of sandbanks and dunes are distributed with medium-sized grains and are often distributed in spots. On the other hand, fine-grained sand is found here and there near the coast where there is little current in the inner part of the bay. All of them are well culled, and it is generally known that areas with relatively high groundwater levels are at high risk of liquefaction. However, considering it together with construction troubles, it has been found that even during underground excavation such as shield construction, there is a risk of fluidization due to excavation vibrations (Geotechnical Society Kansai Branch (2013), Kitada・Mimura (2021), Kitada (2022)). Furthermore, it has become possible to clarify the extraction of flexural structures associated with fault deformation by grasping the geological distribution over a wide area using boring data. It is possible to extract geological and ground risks that cannot be fully grasped.
It is necessary to fully understand the surface geological ground of urban areas in order to study development and conservation, and it is thought that the attempt of geological study using these new ground information will be developed nationwide in the future.
Within KG-NET, we focused on each region and conducted a study with the aim of showing examples of utilization of these data. The results of this research were published in the New Kansai Ground Series, covering the Osaka Plain, the Kyoto Basin and so on. In each region, the cross-sectional diagrams of representative subsurface ground, geological stratigraphy, characteristics of sediments, relationships with geological structures, etc. are summarized, and engineering characteristics are also summarized. Therefore, it is used to explain the outline of the geological survey work in the relevant area, to confirm the target strata during the survey, and to plan the survey.
In addition, in areas including harbor areas such as the Osaka Plain, the distribution of seafloor clay layers basically associated with sea level changes is characteristically distributed. On the other hand, in the inland area, the characteristics of the river sediment and hinterland reflecting the rock characteristics of the exposed basement rock were clarified, and the ground characteristics of each region could be summarized. A feature of these reports is that they summarize not only geological content such as geological depositional environment and sedimentary age, but also engineering soil properties and physical properties. The characteristics of the area will be clarified by side-by-side comparison of what has been clarified by the standard boring survey with the data registered in the surrounding boring database. By using this kind of work to understand the stratum distribution and sedimentation conditions, it became clear what kind of sedimentation conditions the geological features with a high risk of construction trouble are distributed in, and points to be noted have also been clarified. For example, the 'sand' layer deposited near land and in areas with moderate currents in Holocene marine sediments deserves attention. The sediments of sandbanks and dunes are distributed with medium-sized grains and are often distributed in spots. On the other hand, fine-grained sand is found here and there near the coast where there is little current in the inner part of the bay. All of them are well culled, and it is generally known that areas with relatively high groundwater levels are at high risk of liquefaction. However, considering it together with construction troubles, it has been found that even during underground excavation such as shield construction, there is a risk of fluidization due to excavation vibrations (Geotechnical Society Kansai Branch (2013), Kitada・Mimura (2021), Kitada (2022)). Furthermore, it has become possible to clarify the extraction of flexural structures associated with fault deformation by grasping the geological distribution over a wide area using boring data. It is possible to extract geological and ground risks that cannot be fully grasped.
It is necessary to fully understand the surface geological ground of urban areas in order to study development and conservation, and it is thought that the attempt of geological study using these new ground information will be developed nationwide in the future.