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Whetstone <br />Associates <br />Technical Memorandum <br />2. GROUTING THEORY AND CONSIDERATIONS <br />2.1 General Rules for Grouting of Low-Permeability Bedrock <br />Materials used for grouting must have the ability to penetrate even small fracture openings, must be <br />fluid enough to be easily injected into the fractured rock, and must achieve a sufficient strength in a <br />reasonably short time. Selection of the type of grout for each project is based on the grouted <br />formation permeability, and the scope of grouting - the requested flow and permeability reduction. <br />Cement-based grouts are particle suspensions, and the size of particles limits their use for various <br />sizes of fractures. The maximum size of grout particles must be smaller than the size of fractures to <br />be grouted. The other constraint is pressure filtration, which can cause the water drain to off and <br />limit the penetrability of the grout. <br />Extensive research of cement-based grouts has been conducted by the U.S. Bureau of Reclamation, <br />by the U.S. Army Corps of Engineers, and by the DOE Office of Technology Development. <br />Conclusions of the above research work indicated that cement-based grouts can be used to produce <br />low-permeability, high-strength, and high-durability grout curtains in fractured bedrock and soil. <br />Cement-based grouts, with various additives, are used on most mining, tunneling, and dam <br />construction projects, and only in special cases where low permeable rock is to be grouted, microfine <br />and synthetic grouts are used. Microfine cement is a newer version of cement that, because of its <br />fine particle size, can be applied to low-permeability rocks. <br />General experience with cement-based grouts indicates the following ranges of applicability: <br />Portland cement based grout 1 x 10° to 5 x 10-6 cm/sec <br />Microfine grout 1 x 10-3 to 1 x 10-6 cm/sec <br />Based on the observed discharge from the corehole, the fractured bedrock and the damaged 2-inch <br />casing have permeabilities on the order of 10-5 cm./sec and standard Portland cement based grouts <br />should achieve sufficient penetration to adequately seal the corehole and any adjacent fractures. <br />2.2 Grout Mixing <br />The Portland cement based grout will be mixed using high shear "colloidal" type mixer and stored in <br />agitated tanks until pumped into the formation. The holding time for the grout mixture will be <br />monitored and stored batches that exceed a holding time of 1 hour will be discarded (wasted) and not <br />pumped into the formation. Wasted grout will be pumped to a holding tank or sump and allowed to <br />harden before being broken up and removed from the site. Water for grout preparation will be <br />supplied from the domestic well at the Schwartzwalder Mine. Water quality for the domestic well is <br />summarized in Table 1. <br />4109C.110106 2