Page 188 - Water Standards
P. 188

the concrete placement capacity and temperature control
                                requirements, and unnecessary construction joints shall be
                                reduced as many as possible. The length⁃width ratio of the
                                block should not be too large, usually less than 2   5 ∶ 1  
                             4) Anti⁃cracking steel bars shall be arranged at weak parts
                                where division is definitely needed and cracks may occur.
                           2  The types and requirements of layering and blocking:
                             1) Conctete blocks at the lower parts of powerhose should be
                                usually poured in a whole section but with staggered joints.
                                The concrete should be poured in a whole section in small
                                hydro powerhouses.
                             2) Concrete placement layers should be decided according to
                                the bottom slab, tailwater tube, spiral case floor, turbine
                                floor, pier and generator floor. Layers divided can also be
                                considered for reference for powerhouses with tubular and
                                impulse turbines.
                             3 ) The generator unit should be taken as the individual
                                element for a longitudinal joint.
                             4) Blocked concrete placement can be used for the concrete of
                                upstream and downstream walls, as well as left and right
                                walls at the lower part structures. Water sealing facilities
                                shall be set for the parts with anti⁃seepage requirements.
                             5) For the generator floor, where the hydraulic turbine em⁃
                                bedded parts are installed by stages, can be poured as the
                                generator unit as an placement element.
                             6) The joint surface shall be a smooth and vertical plane,
                                and visible irregular joints shall be avoided.
                             7) The overlap length of the staggered joints of the adjacent
                                upper and lower layer should be usually 1 / 2⁃1/ 3 of the
                                pouring thickness, with a minimum of 50cm. Measures
                                                                            1 8 1
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