IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE) e-ISSN: 2278-1684,p-ISSN: 2320-334X, Volume 17, Issue 2 Ser. II (Mar - Apr 2020), PP 40-44 www.iosrjournals.org DOI: 10.9790/1684-1702024044 www.iosrjournals.org 40 | Page Computational modeling and simulation for unexploded ordnance disposal problem at the seabed Yoshikazu Higa 1 , Hirofumi Iyama 2 and Shigeru Itoh 3 1 Professor, Department of Mechanical Systems Engineering, National Institute of Technology (KOSEN), Okinawa College, Japan 2 Professor, Department of Mechanical & Intelligent Systems Engineering, National Institute of Technology (KOSEN), Kumamoto College,Japan 3 Chief Director, Institute of Shockwave Advanced Technology (ISAT), Japan Corresponding Author: Yoshikazu Higa Abstract:The main objective of our research is to contribute to the technique of unexploded bomb disposal such as an establishment of evacuation area based on computational mechanics. The computational simulation for undersea explosive problems was designed and demonstrated using Smoothed Particle Hydrodynamics schemes by HyperWorks (Altair®)–RADIOSS® software. The technique was to reveal the fragment behavior such as the amounts of charge and seabed soils. In this report, a study about the effect of a 50 kg general-purpose bomb and sea depth on the shock wave phenomena is presented. As a result, by conducting a series of computational simulations, it was observed and visualized that the fragment behavior significantly depends on charge amounts, depth of sea, and seabed soil. Key Word:Unexploded Ordnance, Computational Simulation, Seabed Soil, SPH --------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 12-03-2020 Date of Acceptance: 27-03-2020 --------------------------------------------------------------------------------------------------------------------------------------- I. Introduction This experiment was conducted in Okinawa, where the only ground battle occurred in the Pacific War (The Greater East Asian War), with violent bombing and combat on the southern main island of Okinawa, where important points of the Japanese Army and Navy were located. Approximately 200,000 tons of bombs were detonated by the end of the war, including bombardment [1]. On the other hand, about 7% to 8% of fuses at the time were reported to have been unexploded because of malfunctions. This comprised about 5500 tons under US military rule and about 2000 tons after returning to the mainland of Okinawa on May 15, 1972. Although it has been processed, it is estimated that at least 70 years after the war, about 2000 tons of unexploded bomb (UXB) still remain buried [1]. According to the latest FY2018 results [2], 678 cases were found in public and private works including the carryover in FY2017, and the treated weight was 20.7 tons. However, it is estimated that it will take about 70 years to process all unexploded ordnance. Therefore, considering the situation not only in Okinawa but also in Japan, where urgent safety treatment of UXBs is required, (1) the improvement of discovery technology and (2) the development of treatment technology are important issues. Until recently, the authors have developed the theoretical evacuation areas and actively reduced the evacuation area. This is to contribute to the development of unexploded ordnance safety disposal technology from a viewpoint based on computational mechanics. Hence, we construct a simple simulator for soil explosion problems using commercial finite element analysis software [3]. On the other hand, experiments using a high- speed camera optically captured how the shock wave from the explosion transmits and reflects through the unique Okinawan soil. The soil characteristics have been identified by comparing the experimental and numerical results and also confirmed the verification of the soil parameters' validity [4,5]. However, we have created a soil explosion problem simulator based on the Smoothed Particle Hydrodynamics (SPH) scheme and have conducted the computational experiments to visualize the fragment behavior generated during UXB explosion using particle imaging [6]. In addition, to propose the design and construction of a processing pit, which will actively reduce the evacuation areas, a numerical simulation with a protective wall using liner plate application was performed while the effect of suppressing fragments due to differences in exit shapes was also examined [7]. On the other hand, in underwater bomb disposal problem targeted in this paper, about 10% of the annual disposal results of unexploded ordnance have been processed on the seabed, and many of which were