Page 144 - Water Standards
P. 144

1  Jointing and blocking shall follow the following principles:
                             1) Jointing positions shall comply with structure layout re⁃
                                 quirements and geological conditions.
                             2) The longitudinal jointing layout shall comply with stress re⁃
                                 quirements of the dam section, with uniform blocking and
                                 convenience for union⁃grid pouring.
                             3) Blocking size shall be adapted to the pouring capacity.
                             4) Blocking size shall comply with not only the requirements
                                 for quality and schedule, but also economic rationality.
                           2  Both segmentation and blocking of concrete placement shall
                       meet the design requirements. If there is no specific design require⁃
                       ment, the distance between two adjacent transverse joints may be set
                       to 15-20m; and for section at which the powerhouse locates, the dis⁃
                       tance may be extended to 20-25m; the distance for longitudinal joints
                       may be set at 15-30m.
                           3  Concrete pouring thickness shall be determined by calculation
                       according to the allowable temperature difference. The layer thickness
                       within the range restricted by the foundation should be 1 - 2m, and
                       that outside the foundation⁃restricted range 3-6m. In the same block,
                       the elevations of horizontal construction joints of adjacent pouring
                       blocks shall be staggered. If a horizontal construction joint intersects
                       with the gallery crown, it should be connected with skewback in a
                       gradient of 1 ∶ 1 - 1 ∶ 1   5, or the distance between horizontal con⁃
                       struction joints above the gallery crown shall be no less than 1   5m.
                           4  The interval time between two adjacent upper and lower con⁃
                       crete layers should be controlled within 5-7 days, and the maximum
                       value should not exceed 10 days.
                           5    During construction, each dam block should be raised
                       uniformly, the elevation difference between adjacent blocks should
                       not be larger than 6m, and the maximum value should not exceed
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