Vol.9 No.2 2016

Research paper : Three-dimensional urban geological map (T. NAKAZAWA et al.)−76−Synthesiology - English edition Vol.9 No.2 (2016) results are presented as borehole logs[10] according to the specifications of the Japan Construction Information Center (JACIC). When conducting the standard penetration tests, the samples available are not undisturbed all-core samples, and in many cases, the person entering the data is not a geological expert but a civil engineer or an on-site drilling operator, and therefore, the description of the strata is simple. Drilling surveys for civil engineering and construction work are basically terminated at the point when the depth of the stratum that is the support base of the structure is reached. Although the depth varies according to the geological conditions, many are about 10 to several tens of meters deep. Therefore, most construction borehole data are only to the depth of several tens of meters.Recently, the massive borehole data of the civil engineering and construction work have been accumulated by the Government and local governments as mentioned before, and are being organized as electronic databases. Currently, the electronic borehole data format that has become a de facto standard is set by the MLIT.[11] This is the XML format of the JACIC specified borehole logs that includes the standard penetration test data explained earlier. Since the borehole data that are electronically delivered as geological survey reports to the local governments of prefectures or major cities are in this format, the electronically delivered borehole data can be stored in the database as they come, as long as the database is unified to this file format. Therefore, recently many databases store the borehole data in the JACIC spec XML format, but there are still databases with various data formats. In order to make secondary use easy, it is desirable to convert the data with other formats to the JACIC spec XML format to create the database. At any rate, to conduct the organization of borehole data and the use of borehole data for the geological structure analysis, it is necessary to gain the understanding and cooperation from the local governments for the geoinformation organization effort. Also, for the management and conversion of the local governments’ borehole data to the standard format, it is important that AIST provide technical support if needed.3.2 Drilling surveyThe local governments have aggregated enormous amount of borehole data for public works from the past, and these may be great merit for geoinformation organization. On the other hand, since the main purpose of such data, as mentioned before, is the presentation of engineering data (standard penetration test data), they normally do not include the descriptions of volcanic ash layers or chronological data that are the basis of a wide range strata correlation (Table 1). The descriptions of strata are extremely simple, and the sedimentary structure, fossil occurrence, and detailed Fig. 2 Outline of 3D geological maps for urban areasTable 1. Comparison of standard borehole data and borehole data of public works Standard borehole data: data originally surveyed by AIST Existing borehole data: display all database from local governments and other institutions Outcrop log: show boring logs published in papers(Topographic map: Geospatial Information Authority of Japan) Determine landform based on elevation data etc. Reflect distribution of surface sediments Cross-section, contour map, 3D display【Basic content】GeologicalmapEstablish a new style of geological maps that enables visualization of subsurface geological structuresOrganization of easy to understand, easy to use, and highly reliable geoinformation, assuming delivery over webProvide data in easy-to-use formatLandform classification3D geological modelBorehole and outcrop logs (data archive)FaultFaultHillHillLowlandUplandUplandMountainAbout 10~60 mBasic survey for civil engineering and construction workBorehole data of public worksEngineering data Rock and soil classification Observation Standard penetration test data Water level in borehole etc.About 40~120 mGeological data + engineering data Sedimentary facies Chronological data Volcanic ash layer Fossil Grain size Physical property data such as velocity logging etc.Academic researchOrganization of reference dataStandard borehole dataCharacteristicDrilling depthItemObjectiveAlthough there are not too many survey points, high precision information that serves as reference for strata comparisonsThey are mainly of standard penetration test data and simple descriptions of strata, but there is accumulation of massive amount of data from the past


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