Grouting in Closer Dyke Area

Method Statement The area of closer Dyke is very susceptible means high seepage zone by which water flows through the voids or by filled loose materials and enter into the excavated portion of Dam. The entering of water through such materials creating lots of problem in many cases like excavation which is one of the most important activities hampered by seepage of water. To stop the seepage of water Grouting is only the suggestive method .The main purpose of Grouting in this part is 1) creating a seepage barrier to reduce uplift 2) consolidating the loose or filled material sufficiently to make it act as a monolith. Grouting Materials: The type of Grout used here is the mixture of Portland cement and water in the ratio of 1:4. The grout is forced through holes that having the depth of 3.0m and is oblique to the surface. As it is the primary stage of grouting so no chemicals to be added. Grouting Equipment: Unigrout pumps are used to inject grout in this area. This consists of a tank filled with grout; which is cautiously squeezed out into the holes by means of compressed air (ROC, Atlas Copco). Pressure gauge is installed in the grout pump in order to maintain proper line pressures. Grout Holes: The grout is forced into oblique holes varying from 50 to 80, the diameter of which is 64mm. The holes are drilled with ROC equipment with the pressure of 5kg/sq.cm. The length of the holes are 3.0m and are staggered.The holes pattern are shown below: Grouting Method: The method used for grouting in the closer Dyke area is stage method. In this method the holes are drilled to the seam closest to the surface and then the holes are grouted. The process is repeated, using increasing grouting pressure, until the plan grouting depth is reached. Once the primary holes are grouted successfully then go for the holes of larger depth using the same machine and after increasing the hole depth or by reaching the water table Packer method come in view. In this method the holes are drilled to the full planned depth. A zone of certain thickness then is grouted, and packer is inserted into the hole corresponding to the top of the grouted zone. The overlying zone for a certain thickness then is grouted using decreased pressure. The process is repeated until the hole is grouted.