Volume Volume2\Architecture
Entry# 771. I. ON FISSURES IN WALLS.
Contents: Vol. 1 | Vol. 2
I.
ON FISSURES IN WALLS.
First write the treatise on the causes of the giving way of walls
and then, separately, treat of the remedies.
Parallel fissures constantly occur in buildings which are erected on
a hill side, when the hill is composed of stratified rocks with an
oblique stratification, because water and other moisture often
penetrates these oblique seams carrying in greasy and slippery soil;
and as the strata are not continuous down to the bottom of the
valley, the rocks slide in the direction of the slope, and the
motion does not cease till they have reached the bottom of the
valley, carrying with them, as though in a boat, that portion of the
building which is separated by them from the rest. The remedy for
this is always to build thick piers under the wall which is
slipping, with arches from one to another, and with a good scarp and
let the piers have a firm foundation in the strata so that they may
not break away from them.
In order to find the solid part of these strata, it is necessary to
make a shaft at the foot of the wall of great depth through the
strata; and in this shaft, on the side from which the hill slopes,
smooth and flatten a space one palm wide from the top to the bottom;
and after some time this smooth portion made on the side of the
shaft, will show plainly which part of the hill is moving.
Footnote: See Pl. CIV.
The cracks in walls will never be parallel unless the part of the
wall that separates from the remainder does not slip down.
WHAT IS THE LAW BY WHICH BUILDINGS HAVE STABILITY.
The stability of buildings is the result of the contrary law to the
two former cases. That is to say that the walls must be all built up
equally, and by degrees, to equal heights all round the building,
and the whole thickness at once, whatever kind of walls they may be.
And although a thin wall dries more quickly than a thick one it will
not necessarily give way under the added weight day by day and thus,
16 although a thin wall dries more quickly than a thick one, it
will not give way under the weight which the latter may acquire from
day to day. Because if double the amount of it dries in one day, one
of double the thickness will dry in two days or thereabouts; thus
the small addition of weight will be balanced by the smaller
difference of time 18 .
The adversary says that _a_ which projects, slips down.
And here the adversary says that _r_ slips and not _c_.
HOW TO PROGNOSTICATE THE CAUSES OF CRACKS IN ANY SORT OF WALL.
The part of the wall which does not slip is that in which the
obliquity projects and overhangs the portion which has parted from
it and slipped down.
ON THE SITUATION OF FOUNDATIONS AND IN WHAT PLACES THEY ARE A CAUSE
OF RUIN.
When the crevice in the wall is wider at the top than at the bottom,
it is a manifest sign, that the cause of the fissure in the wall is
remote from the perpendicular line through the crevice.
Footnote: Lines 1-5 refer to Pl. CV, No. 2. Line 9 _alle due
anteciedete_, see on the same page.
Lines 16-18. The translation of this is doubtful, and the meaning in
any case very obscure.
Lines 19-23 are on the right hand margin close to the two sketches
on Pl. CII, No. 3.
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