Geotechnical magnetic–similitude–gravity model testing method

Abstract

Physical modelling under the gravitational field between 0 and ng plays a key role in both terrestrial- and aerospace-geotechnical engineering. A geotechnical magnetic–similitude–gravity model testing (GMMT) method is newly proposed to provide an alternative approach to the current physical modelling methods. The theoretical criteria for achieving a magnetic field to simulate the gravitational field are presented first, based on which an exact simulation of the stress field is achieved between the physical model and its corresponding prototype. A GMMT equipment is then designed and manufactured, and a related procedure for obtaining its control and input parameters is presented. Accordingly, the preparation of the model material is demonstrated utilising a kind of magnetically sensitive granular (MSG) media. The relationship between mechanical properties, magnetisation, magnetic–similitude–gravity and magnetic powder content of the MSG media are further investigated, and the influences of both magnetising field and magnetisation process are shown to be negligible in terms of mechanical behaviour. A series of physical modelling of the bearing capacity of granular media under low-gravity conditions is finally performed using the GMMT equipment. The results show good agreement with previous data obtained by the parabolic flight aircraft.

Discussion of “Bearing Capacity of Shallow Footings in Simulated Lunar Environments Using Centrifuge Tests” by Hey-Rim Lee, Heon-Joon Park, and Dong-Soo Kim

“…Alternatives of low-gravity simulation are provided as follows: (1) aircraft method with parabolic flight trajectories (Costes et al 1971); (2) microgravity rocket or drop tower method; (3) tilting method (Zou et al 2015); (4) hydraulic gradient similitude method (Dou and Byrne 1996); and (5) magnetic-similitude-gravity method (Li et al 2018).…”