Muography as a novel complementary technique for geotechnical surveys&amp;#160;

&amp;lt;p&amp;gt;Muography is an imaging technique that can utilize cosmic-ray muons for remote and non destructive exploration of large-sized natural and human-made structures [1]. We applied mobile gaseous-detector-based muography instruments [2] for surveying different human-made structures in Japan:&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;(1) A buried reinforced concrete pillar (that is a standard pillar along Japanese railways) was installed inside a mound, and muography was blind tested from a three meter deep shaft located three meters away from the pillar [3]. Our muographic surveys revealed the bottom of the pillar at the depth of 80 cm with a spatial resolution of 15 cm within a few days.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;(2) Debris dams are applied to prevent the catastrophic impacts of fast debris flows on the landscapes in mountain areas. We muographically measured the density-lengths through different debris dams (e.g., see in Ref. [4]) with a spatial resolution of below 50 cm within 2-4 weeks. The muographic surveys detected a weak zone inside a debris dam of Karasugawa river in consistency with elastic wave tomography survey.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;(3) Muographic inspection of the Imashirozuka burial mound was conducted for detecting physical evidences related to a past earthquake [5]. This mound collapsed after a landslide generated by the 1596 Fushimi earthquake. Bidirectional muographic surveys detected a 4-8 m width low-density region at the top of the mound. These were interpreted as large-scale vertical cracks that caused the translational collapse process behind the rotational landslide that was already found in prior trench-survey-based works. The observations revealed that the mound already had intrinsic problem with the stability of the basic foundation before the earthquake.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;These proof of concepts demonstrate the applicability of muography for geotechnical surveys and encourage the further studies for improving the protection of landscapes, economies and societies.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;[1] Ol&amp;amp;#225;h, L., Tanaka, H. K. M., and Varga, D. Muography: Exploring Earth's Subsurface With Elementary Particles, 1st ed., Geophysical Monograph Series, Vol. 270, American Geophysical Union and John Wiley &amp;amp; Sons, ISBN 9781119723028, 2022.&amp;lt;br&amp;gt;[2] Ol&amp;amp;#225;h, L., et al.: CCC-based muon telescope for examination of natural caves, Geosci. Instrum. Method. Data Syst., 1, 229, https://doi.org/10.5194/gi-1-229-2012, 2012.&amp;lt;br&amp;gt;[3] Ol&amp;amp;#225;h, L., et al.: The first prototype of an MWPC-based borehole-detector and its application for muography of an underground pillar. Geophysical Exploration (J-STAGE), 71, 161-178, https://doi.org/10.3124/segj.71.161, 2018.&amp;lt;br&amp;gt;[4] Sakatani, Y., et al.: Research on the development of soundness analysis technology for Sabo-related infrastructure by muography (Part 1), Journal of the Japan Society of Erosion Control Engineering, ISSN 2433-0477, 85, 69, 2020. (In Japanese)&amp;lt;br&amp;gt;[5] Tanaka, H. K. M., Sumiya, K., and Ol&amp;amp;#225;h, L.: Muography as a new tool to study the historic earthquakes recorded in ancient burial mounds, Geosci. Instrum. Method. Data Syst., 9, 357, https://doi.org/10.5194/gi-9-357-2020, 2020.&amp;lt;/p&amp;gt;