3.3.4 Displacement transducers

Displacement meters are generally divided into two categories; contact type and no-contact type. The contact type is a displacement converter of the LVDT (Linear Variable Differential Transformer). Photo 4(a) shows the LVDT (left-hand side) and a mount (right-hand side). No-contact type is a laser displacement meter based on the triangulation principle as seen in Photo 4(b). An application is shown in Photo 5 where a miniature shield tunneling machine is equipped with laser displacement meters. The ground surface settlement is measured by laser displacement meters with high resolution. Displacement meters are controlled by means of an exclusive driving motor so that the cross-sectional profile of the settlement is obtained.

(a) contact type

(b) no-contact type

Photo 4. Displacement meters

Ueno, K., Nakatomi, T., Mito, K. and Kusakabe O. (1994) : Influence of initial conditions on bearing characteristics of sand, Proc. of CENTRIFUGE 94, pp. 541- 546.

Imamura, S., Nomoto, T., Mito, K., Ueno, K. and Kusakabe, O. (1996) : Design and Development of Underground Construction Equipment in a Centrifuge, Proc. of Int. Symp. on Geotechnical Aspects of Underground construction in Soft Ground, London, U.K., pp. 531-536.