Non-Target Soil Deformation Mapping by Photogrammetry for Underground Tunnel Model Test
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pISSN 1226-7988, eISSN 1976-3808 www.springer.com/12205
DOI 10.1007/s12205-020-5080-1
Surveying and Geo-Spatial Engineering
Non-Target Soil Deformation Mapping by Photogrammetry for Underground Tunnel Model Test Changno Lee
a
and Jaehong Oh
b
a
Member, Dept. of Civil Engineering, Seoul National University of Science and Technology, Seoul 01811, Korea Member, Dept. of Civil Engineering, Korea Maritime and Ocean University, Busan 49112, Korea
b
ARTICLE HISTORY
ABSTRACT
Received 15 June 2020 Accepted 28 July 2020 Published Online 23 October 2020
A complex urban environment requires frequent underground tunneling to resolve heavy traffic congestion. With new underground lines being constructed close to existing underground lines the soil deformation around the underground tunnels should be studied and analyzed with proper tunnel model tests. Therefore, we conducted non-target soil deformation mapping using photogrammetry for two different underground tunnel models of sandy soil and clay. Selfcalibrated cameras were used to acquire before and after images of the models with the loading test. With accurately estimated exterior orientation parameters (EOPs), the soil deformation was measured via image matchings between two images. Different image matching parameters were tested and the effect of filtering was investigated to produce soil deformation vectors on the images. Experimental results showed that sandy soil and clay required different matching window sizes for the best results. In addition, the deformation vector filtering was helpful to suppress outliers only when an image matching threshold was not applied. With proper matching parameter setup and filtering, the visually informative soil deformation vector map could be generated using photogrammetry.
KEYWORDS Soil deformation Underground tunnel model Geotechnical Photogrammetry Mapping Non-target
1. Introduction Recently, more and more underground tunneling has been carried out to resolve heavy traffic congestion in a complex urban environment. With increasing underground tunneling, new underground lines are currently being constructed in close proximity to existing underground lines. One example is a divergence tunnel that gains high attention because it is used not only for interchange but for a ramp between surface road and underground road. With these complex underground environment, the soil deformation around the underground tunnels should be studied and analyzed with proper tunnel model tests. Soil load test is a type of load testing used in geotechnical investigation to determine the bearing capacity including stress and strain. The results from in-situ or laboratory soil tests are used as basic data for the structure design in civil engineering. In-situ soil tests are widely used to estimate bearing capacity of soil in field but they have limitations to be used for the underground soil deformation. Therefore laboratory soil tests are required with proper scale of models (Lee, 2006) and they have CORRESPONDENCE Jaehong Oh
[email protected]
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