 Selection of Grout and Additives
Grout Mix Formulations Grouting Equipment Grouting Procedure The following section provides a primer on the pressure grouting of rock joints particularly as it is performed in underground mines. However, the method of grouting rock is also applicable to grouting dam foundations on rock or rock-concrete contact around tunnel plugs. The emphasis is on grouting with cement suspension grouts, which is the most commonly used grout for underground rock grouting applications. Grouting is simply the injection of fluids or fluid suspensions into the joints of a rock under pressure for the purposes of reducing the hydraulic conductivity of the rock mass or for improving the strength of the rock mass. In order to inject grout, holes are drilled to the required depth usually with rotary-percussion holes Grouting has often been viewed in the past as a "black art" since there was rarely an engineered approach that could be used in a wide variety of situations. In many cases, unstable grout cement suspensions were forced into the rock joints under enormous pressure with little or no consideration given to hydraulic jacking. In other cases, very "thin" grouts have been used and grouting performed much longer than necessary when the grout simply flowed through the joints, without staying on the joint surfaces. In recent years, there has been more research in the area of grouting for such things as dam seepage cut-offs and underground nuclear waste disposal. It is now possible to take a more professional approach to rock grouting. This approach involves frequent monitoring of the response of the ground to grouting and adjustment of the grouting design, grouting mixes, and grouting pressure based on measured response. Technological advances in the form of relatively inexpensive electromagnetic flowmeters and chemical admixtures such as superplasticizers have contributed to the success of modern rock grouting.
| 
