Grouting in sedimentary and igneous rock with special reference to pressure induced deformations

After a short introduction in Chapter 1, typical properties of sedimentary rocks are given in Chapter 2, exemplified with limestone formations in the Malmö Region in southern Sweden. Two main grouting techniques are defined in Chapter 3, grouting by permeation (pressure not causing fracture in the rock) and grouting by hydraulic fracturing (pressure causing opening of existing fissures or tensile fracture in the rock). The deformations caused by the two methods are discussed. Permeation grouting and permeability of different rock materials are discussed in Chapter 4. The permeability of cement based grouts in soil and rock is often overestimated. In a diagram, a relationship is given between Darcy's coefficient of permeability, k [m/s]; and a crack pattern defined by the number of cracks per meter, n [1/m]; crack widths, t [mm]; and crack volume ratio [%]. Hydraulic fracturing is treated in Chapter 5. For confined conditions, equations and diagrams are given for the maximum gap deformation in the cracks and for the widths of the grouted zone. The equations and diagrams are given as functions of the injected grout volume per round and the ratio of the modulus of Elasticity and the injection pressure. Two loading cases are treated: (a) two-dimensional loading with a grouting zone length L [m] and (b) conical loading with a grouting zone diameter D [m]. For unconfined conditions the risk for spreading of the grout is discussed. The importance of the deformations is illustrated with case studies. Final remarks are given in Chapter 6. One main conclusion is that the injection pressure is not a satisfactory stop criterion. As unintended hydraulic fractures often take place, when permeation grouting is intended, an uncontrolled spread of grout may occur. Instead, the volume of grout injected per stage, or round, should be limited. It is often best to inject small amounts of grout, in several rounds, allowing the grout to stiffen between the rounds. This procedure is illustrated with two examples in an Appendix.Godkänd; 2004; 20080522 (ysko