Page 187 - Water Standards
P. 187
completion of the permanent one.
2 The water outside powerhouse area should be directly drain⁃
aged to beyond the upstream and downstream cofferdams.
3 A permanent leakage water sump in the powerhouse should be
constructed in advance and acted as the main drainage measure in
powerhouse constrction.
3 9 4 The layering and blocking division of concrete placement shall
meet the following requirements:
1 The principle of layering and blocking:
1) The layering and blocking shall be done according to the
factors of powerhouse structure characteristics, shape and
stress, as well as equipment installation. No joints shall
be arranged at the stress concentration position and at the
weak zones of the structure. The blocked parts shall not be
of acute angles and thin slices in the geometric shape. The
construction joints and structural joints shall be
coordinated each other to avoid weakening the integrity of
the structure. Formwork, steel bars, embedded parts,
concrete vibrating and the convenience of the second⁃stage
concrete placement shall also be considered in layering
and blocking.
2) The layering thickness shall be decided according to the
structure characteristics and temperature control require⁃
ments. The layer thickness within foundation restraint
zones should be no larger than 2m, and the thickness can
be increased up to 2 5m above the restraint zone. For the
position with a large heat dissipation surface, the layering
thickness can be appropriately increased according to the
specific condition, but shall not be larger than 4 0m.
3) The size of the blocking are shall be decided according to
1 8 0