Location and size of the gallery depends on the need and size of the mechanical equipment. It is a gallery made in a dam to provide access to and to house the mechanical equipment required for the operation of gates in outlet conduits, power penstocks or spillway crest. Bhakra dam has galleries aggregating in length to 5 km. It also caters for the drainage, gate and grouting galleries also serve as inspection galleries. It is a gallery to provide access to the interior of the mass comprising the dam with a view to inspect the structure and study the structural behaviour of the dam in post-construction period. It serves for intercepting seepage from the water face and conducting it away from the downstream face and drilling and draining the downstream portion of the foundation. It is a supplementary drainage gallery located parallel to the crest at about 2/3rd of the base width from upstream face and extending usually only through the deepest portion of the dam. It caters for (i) The drainage of water percolating from upstream face or seepage through the foundations in the dam, (ii) Provides space for drilling and grouting of holes from the floor of the gallery for the main grout curtain, and (iii) For drilling foundation drain holes after foundation grouting has been completed. The gallery is of a size suitable for carrying out drilling operations from inside it. A foundation gallery generally extends along the length of the dam near the rock surface conforming in elevation to the transverse profile of the canyon in plan it is nearer and parallel to the axis of the dam. Gallery Parallel to Dam Axis: (a) Foundation gallery.
On the basis of alignment, galleries are classified as parallel to the axis and normal to the axis of the dam, as under.ġ. On the basis of function served, the galleries are classified as drainage gallery, inspection gallery, grouting gallery, access gallery, foundation gallery and gate gallery. Galleries can be classified on the basis of the function served as also according to their alignment. Also to provide access for grouting the construction joints which cannot be done from the face of the dam. Post-construction grouting: To provide space for header and return pipes for post-construction grouting of longitudinal joints of the dam. Operation of gates and control equipment: To provide access to mechanical equipment for the operation of rates and control equipment.ĥ. Drilling: To provide access for carrying out drilling and grouting of foundations, etc.Ĥ.
Inspection: To provide access to the interior of the mass comprising the dam with a view to inspect the structure and study the structural behaviour of the dam in post-construction period.ģ. Drainage: To cater for the drainage of dam section by intercepting seepage from the water face and carry it away from the downstream face.Ģ. The functions for which the galleries are provided are:ġ. The shape and size of the gallery depends on the size of the damned and the function served. They may be provided parallel or normal to dam axis at various elevations The galleries are interconnected by steeply sloping passages or by vertical shafts fitted with lifts.
Galleries are openings or passageways left in the dam body.
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