Soil improvement and construction methods in peat - Geotechnics of Organic Soils and Peat - page 140

Figure 6.16 The steps in the ras-columns system ( after Raito Kogyo, 2006) and its mixer (SDFEC, 2007;
Kazemian and Huat, 2009b).
Figure 6.17 (a) CDM machine with two augers ( after Raito Kogyo, 2006), (b) CDM machine with
three augers ( after Keller, 2005), (c) two augers which have been parted-off ( after Balvac,
2008).
(Figure 6.16 (1)). This is followed by penetration, whereby after passing through a dry
excavation zone slurry should be injected without any jetting (Figure 6.16 (2)). The
third step is churning or moving the head up and down to mix the soil and cement
thoroughly (Figure 6.16 (3)). Finally, in the completion step the head is withdrawn
and the soil-cement column is completed (Figure 6.16 (4)).
6.4.2 Cement deep mixing system (CDM)
The second method is related to DSM and is one of the DMM methods, known as
cement deep mixing (CDM). As mentioned earlier, in this method, a series of overlap-
ping augers and mechanical mixing shafts are used. Figures 6.17(a) and 6.17(b) show
CDM machines with two and three augers respectively. Two augers which have been
parted-off (detached) are shown in Fig. 6.17(c).
CDM is normally used in soft soil that contains mineral soils such as clay or sand. In
some conditions where mineral soils are absent, sand should be added before mixing in