Civil Engineering Reference
In-Depth Information
and a convenient constant of set is measured from one to the other at each of
the four angles of the rising joint. When the rising joint of the second block has
been dressed to the plane so established, the setting is a straightforward matter of
levering the second block into position.
h e circumstances, however, are markedly dif erent when the bed joints are not
horizontal and/or not continuous. Particularly in the latter instance (because of
the indented bed) there may arise dii culties in setting which require a block to
be lowered into position. When the block is a massive one weighing several tons
then the proceedure to ef ect this is not obvious. As yet no practical study of these
questions is published.
It is now necessary to direct attention to a salient characteristic of Egyptian
monumental masonry: the battered external face of outer walls. It is this feature
which gives Egyptian monuments their air of grave repose. As the wall face rises
it inclines inward from the vertical at an angle of about 6° (or with a retreat in the
proportion to the vertical height of ca 1:10). To obtain this inclination has ot en
been considered as requiring specii c devices of some complexity, e.g. L shaped
constructions erected beyond the angles of the building on which the proi le of the
battered wall face is painted in red. h us the line of the wall face at any height can
be obtained by sighting or by running a cord from one painted proi le to the other
at the opposite end of the wall. Such devices undoubtedly existed, but it will be
found that all the literature relating to them (e.g. W.M.F. Petrie,
Medum
, London
1892, pp. 11-13) refers to underground structures, massifs rather than walls.
Alternatively it is suggested that the batter was controlled by measuring inwards
from a plumb line or other vertical erected at the foot of the wall. Instances are
reported where this proceedure was used to cut at intervals rising channels in
the rough masonry face of walls dei ning the required angle of batter so that the
intervening panels could be dressed true by reference to them.
In fact, however, the problem is virtually non-existent.
If one rising joint is dressed true prior to setting the block and for this purpose
the adjacent marginal draught on the face of the block is cut, then this marginal
draught will incorporate the angle of batter (obtained by applying a bevel at the
correct angle). h us since at least one rising joint on each block is cut to incorporate
the angle of batter, then this is provided everywhere for the wall face. If, on the
other hand, no marginal draught is cut at the rising joints prior to setting blocks,
then the retreating line of the outer face of each course is very simply obtained
by directly measuring out the breadth of the wall at the upper bed joint of each
course. h is is given by the formula b—s, where b is the breadth of the wall at the
upper bed joint of the preceeding course and s is the
s q d
, the inward inclina-
tion from the vertical = the diminution in breadth of the wall. h is is measured
and marked out on the angle blocks at each extremity of the wall. A sighted line
Battered
external
wall faces
161
48
167, 168
