Foundation grouting （灌浆） for concrete dam foundations prior to concreting is usually limited to shallow holes and hence does not delay over-all construction to the extent that foundation treatment delays earth dam construction. Deep drilling of both grout and drain holes is done from the foundation galleries（廊道） in the dam after concreting is substantially complete and this operation is seldom a schedule factor in over-all dam completion. The principal objectives of grouting in a rock foundation are to establish an effective barrier to seepage under the dam and to consolidate the foundation. Spacing, length, and orientation of grout holes and the procedure to be followed in grouting a foundation are dependent on the height of the structure and the geologic characteristics of the foundation. Since the characteristics of a foundation will vary for each site, the grouting plan must be adapted to suit existing conditions. Grouting operations may be performed from the surface of the excavated foundation, from the upstream fillet （内圆角、缘条）of the dam, from the top of concrete placements for the dam, from galleries within the dam, and from tunnels driven into the abutments, or any combination of these locations. The general plan for grouting the foundation rock of a dam provides for preliminary low-pressure, shallow consolidation grouting to be followed by high-pressure, deep curtain grouting（帷幕灌浆）. As used here, “high pressure” and ''low pressure" are relative terms. The actual pressures used are usually the maximum that will result in filling the cracks and voids as completely as practicable without causing any uplift or lateral displacement of foundation rock. www.m448中国最庞大的资料库下载