construction and refurbishment of earthen irrigation channel banks

etween the soil sample and the water should be carefully examined. Theoccurrence of a colloidal cloud at this interface is an identification of dispersivesoil. With a highly dispersive soil it will have dispersed into a dense cloud in thattime, whilst a less dispersive soil will have a local cloud encircling the original soilparticle. With a non-dispersive soil, the area around the soil particle will be clear.A variation on the above test is to use two glass jars, one containing distilled waterand the other a sample of the proposed channel water. If the channel water becomesquite cloudy in the lower part of the jar, then it is probable that a bank built of thetest clay will pipe if special precautions are not taken. If there is little sign of adispersive cloud of clay fines in the channel water jar, but definite cloudiness in thejar of distilled water, piping is not likely, but scouring by rainwater is probableunless there is a protective cover.Care should be taken to ensure that the sample is representative. It is advisable toduplicate the test for each soil. Stirring or shaking the water must be avoided.Sometimes it will be noted that the whole soil mass breaks down rapidly whenplaced in water. This is not dispersion, it is slaking.Construction and Refurbishment of Earthen Channel Banks