construction and refurbishment of earthen irrigation channel banks

Direct removal ofmaterial by entrainmentinto the flowing waterDirect removal ofmaterial from the faceof the bankOften a triggermechanism for massfailuresDirect removal ofmaterial forming the toeof the bankFigure 10.7 AttritionContinued lapping leadsto washing of a scarfinto the bankFigure 10.8 Fretting10.2.2 CrackingSoils prone to cracking are highly plastic, swelling when wet and shrinking ondrying. The characteristics of this type of soil is described in more detail in Section15, Material Selection and Testing. In periods of dry weather it is common forminor surface cracking of the channel bank to occur. This is a normal cyclicoccurrence and these minor cracks should seal up during the next period of wetweather. However more serious cracking may occur which can lead to rapid failureof a bank.Where banks are inadequately protected the exposed surface loses moisture and asthe material dries and shrinks, surface cracks begin to open. Once cracking beginsin the surface of the bank, it may become a self-aggravating process. The crackallows air to circulate deep into the soil causing differential drying and leading tofurther cracking at depth.Construction and Refurbishment of Earthen Channel Banks August 2002 - Edition 1.0 10-19