Page 180 - Water Standards
P. 180

form. Steel form shall be made into a conical shape, with the big front
                       end, and the smal tail end, and the taper is 3‰ - 8‰. The panel
                       shall be flat, and the allowable deviation of the convex⁃concave is 2-
                       3mm. Sliding form lining is divided into covering lining and contra⁃ap⁃
                       erture lining, and priority should be given to the use of covering lin⁃
                       ing.
                           2  Concrete performance, apart from meeting the design re⁃
                       quirements, shall have an initial setting time no less than 1   5 hours,
                       final setting time longer than 4 hours and slump 4-6cm.
                           3   If the inclined shaft slope is between 30° - 45°, a capped
                       chute shall be used for concrete pouring. The capped chute set up a
                       metal baffle every 5 - 8m, and at the end of the chute to avoid the
                       concrete segregation. When the length of the inclined shaft is great,
                       the concrete mixing shall be hoisted to the pouring platform, and then
                       skipping to the position via a chute.
                           4  In the use of sliding form, attention shall be paid to the fol⁃
                       lowing items:
                             1) The roof arch should be poured first. Left and right sides
                                shall be symmetrically poured.
                             2) The sliding time interval, usually around 0   5 hour and
                                maximum of 1 hour, shall be decided through tests. The
                                pull trip of the form should be 5 - 10cm each time, and
                                daily footage should be 2m.
                             3) The form position shall be adjusted at any time, but each
                                time it should not be more than 10cm (radial).
                             4) The form surface shall be kept smooth, to avoid scraping
                                off any concrete during movement.
                       3   8   3  The conditions of and procedures for an underground buried
                       steel pipe shall meet the following requirements:
                           1  Before a steel pipe is installed, the following conditions shall
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