**5.1. Compaction**

and the cutoff wall should be guaranteed. Now, it is a standard way to use one or two linking slabs to connect the cutoff wall with the toe plinth, as exemplified in **Figure 10**. Water stops are installed at the connection points of different components. The width of the toe plinth and the linking slab(s) should be determined based on the allowable hydraulic gradient of the underlying overburden, and on the permitted three-dimensional displacements that are sustainable for the water stop structures. The designing features of connection systems in typical CFRDs are shown in **Table 4**. In these CFRDs, the width of the linking slab(s) usually ranges from 2 to 4 m. The watertight structure for the perimetric joints used in most CFRDs (e.g., Aertash) consists of three layers. A "W"-shaped copper water stop is used at the bottom, and a wavy watertight stripe is used as the middle sealer. Plastic filling material is enclosed by a "Ω"-shaped rubber

**No. Dam Dam** 

16 Dam Engineering

**height (m)**

**Figure 10.** Connection techniques in the Aertash CFRD.

**Table 4.** Designing features of the connection systems of typical CFRDs.

**Overburden thickness (m)**

 Xieka 108.2 100 1.2 4.0 4.0 Nalan 109 24 0.8 8.0 3.0 Miaojiaba 111 48 1.2 6.0 3.0 Jiudianxia 136.5 56 1.2 6.0 4.0 Aertash 164.8 94 1.2 4.0 3.0 + 3.0 Chahanwusu 110 47 1.2 4.0 3.0 + 3.0 Duonuo 112.5 40 0.8 5.0 3.0 Laodukou 96.8 30 0.8 7.0 3.0 + 3.0 Jinchuan 112.0 65 1.2 4.0 4.0 + 4.0 Gunhabuqile 160.0 50 1.2 4.0 2.0 + 4.0

**Thickness of cutoff wall (m)** **Width of toe plinth (m)**

**Width of linking slab (m)**

To provide a firm foundation, vibrating rollers are always used to compact the overburden retained. Dynamic compaction is also commonly used to increase the stiffness and strength of the overburden layers. The authors recommend the Miaojiaba CFRD as an example [9] for dynamic compaction, which was performed before constructing the dam. The average settlement achieved by dynamic compaction was 26.4 cm, and the measured settlement of the overburden during dam operation is about 35–50 cm, indicating that the total settlement may be considerably larger if dynamic compaction has not been performed. Prior to dynamic compaction operations, it is, however, necessary to lower the underground water table.
