Monitoring - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 561

A multiple-point rod extensometer with sufficient length for the deepest anchor allows the
displacement of the rock mass behind the wall of the construction pit to be measured as
a function of depth. This is illustrated in Fig. 17.6 (lower) by means of the example of a
double-point extensometer. In this case, as well as the horizontal total wall displacement
δ H , the horizontal total displacement of anchor 2 can also be calculated as the difference
δ H -

δ 2 (Fig. 17.6, lower).

Figure 17.6 Monitoring of wall displacements of a construction pit due to excavation using
rod extensometers (Wittke 1990)