SETTING OUT STOMPDRIFT DAM
I accurately
measured a base line by tape, and established a series of setting-out points by
triangulation. With the aid of an electric Olivetti Divisuma calculator, I
calculated the co-ordinates of the upstream and downstream intersections of the
joints with the intrados and extrados of the arches at the various pouring
levels, as well as the exact centre of the extrados. This was before the advent
of computers, and was a very laborious calculating task, involving the
solutions of thousands of quadratic equations. In addition I calculated the
co-ordinates of the intersection of two lines: the line from the left hand
extrados intersection to the right hand intrados intersection and the line from
the right hand extrados intersection to the left hand intrados intersection. To
establish this point of intersection on the concrete of a previously cast box,
angles were calculated from three of the setting-out beacons. The surveyor’s
assistant – Elias, whom I brought along from Ebenezer, had a tripod fitted with
an optical plumb bob. He was directed by me from the one beacon to mark two
points along the calculated line, and mark that line by pencil on the concrete.
I then set up on the second beacon, to enable the assistant to mark the
intersection. I then went on the box with my tachy, orientated towards the
beacons I had used, and checked whether I was on the correct position by
pointing to a third beacon, thus not only checking the setting out, but also
the triangulation calculations. After that, I had the assistant marking the
direction of the lines towards the four corners of the box and to the centre of
the extrados, which also had been previously calculated. The corner points
themselves could not be marked directly, because three of the four corners were
then in mid-air, because of the overhang of the arch, as well as the joints.
The carpenters were supplied with a drawing showing the calculated distances
from the setting-out point to the corners and the centre of the extrados, as
well as the calculated offset at the centre of the extrados and other
calculated dimensions, such as the thickness. These enabled the carpenters to
check their work, as well as my own work, because any error would be shown,
whatever its source. As can be imagined, all these calculations were very
laborious indeed, and took up many man-months of high-level staff. Later, when
I was transferred to head-office, I attended a computer programming course from
IBM. As a practical problem, I calculated all these data for the Kat River Dam,
then under construction, which greatly facilitated things there. Also attached
are the instructions I drew up for that purpose.
I accurately
measured a base line by tape, and established a series of setting-out points by
triangulation. With the aid of an electric Olivetti Divisuma calculator, I
calculated the co-ordinates of the upstream and downstream intersections of the
joints with the intrados and extrados of the arches at the various pouring
levels, as well as the exact centre of the extrados. This was before the advent
of computers, and was a very laborious calculating task, involving the
solutions of thousands of quadratic equations. In addition I calculated the
co-ordinates of the intersection of two lines: the line from the left hand
extrados intersection to the right hand intrados intersection and the line from
the right hand extrados intersection to the left hand intrados intersection. To
establish this point of intersection on the concrete of a previously cast box,
angles were calculated from three of the setting-out beacons. The surveyor’s
assistant – Elias, whom I brought along from Ebenezer, had a tripod fitted with
an optical plumb bob. He was directed by me from the one beacon to mark two
points along the calculated line, and mark that line by pencil on the concrete.
I then set up on the second beacon, to enable the assistant to mark the
intersection. I then went on the box with my tachy, orientated towards the
beacons I had used, and checked whether I was on the correct position by
pointing to a third beacon, thus not only checking the setting out, but also
the triangulation calculations. After that, I had the assistant marking the
direction of the lines towards the four corners of the box and to the centre of
the extrados, which also had been previously calculated. The corner points
themselves could not be marked directly, because three of the four corners were
then in mid-air, because of the overhang of the arch, as well as the joints.
The carpenters were supplied with a drawing showing the calculated distances
from the setting-out point to the corners and the centre of the extrados, as
well as the calculated offset at the centre of the extrados and other
calculated dimensions, such as the thickness. These enabled the carpenters to
check their work, as well as my own work, because any error would be shown,
whatever its source. As can be imagined, all these calculations were very
laborious indeed, and took up many man-months of high-level staff. Later, when
I was transferred to head-office, I attended a computer programming course from
IBM. As a practical problem, I calculated all these data for the Kat River Dam,
then under construction, which greatly facilitated things there. Also attached
are the instructions I drew up for that purpose.
I accurately
measured a base line by tape, and established a series of setting-out points by
triangulation. With the aid of an electric Olivetti Divisuma calculator, I
calculated the co-ordinates of the upstream and downstream intersections of the
joints with the intrados and extrados of the arches at the various pouring
levels, as well as the exact centre of the extrados. This was before the advent
of computers, and was a very laborious calculating task, involving the
solutions of thousands of quadratic equations. In addition I calculated the
co-ordinates of the intersection of two lines: the line from the left hand
extrados intersection to the right hand intrados intersection and the line from
the right hand extrados intersection to the left hand intrados intersection. To
establish this point of intersection on the concrete of a previously cast box,
angles were calculated from three of the setting-out beacons. The surveyor’s
assistant – Elias, whom I brought along from Ebenezer, had a tripod fitted with
an optical plumb bob. He was directed by me from the one beacon to mark two
points along the calculated line, and mark that line by pencil on the concrete.
I then set up on the second beacon, to enable the assistant to mark the
intersection. I then went on the box with my tachy, orientated towards the
beacons I had used, and checked whether I was on the correct position by
pointing to a third beacon, thus not only checking the setting out, but also
the triangulation calculations. After that, I had the assistant marking the
direction of the lines towards the four corners of the box and to the centre of
the extrados, which also had been previously calculated. The corner points
themselves could not be marked directly, because three of the four corners were
then in mid-air, because of the overhang of the arch, as well as the joints.
The carpenters were supplied with a drawing showing the calculated distances
from the setting-out point to the corners and the centre of the extrados, as
well as the calculated offset at the centre of the extrados and other
calculated dimensions, such as the thickness. These enabled the carpenters to
check their work, as well as my own work, because any error would be shown,
whatever its source. As can be imagined, all these calculations were very
laborious indeed, and took up many man-months of high-level staff. Later, when
I was transferred to head-office, I attended a computer programming course from
IBM. As a practical problem, I calculated all these data for the Kat River Dam,
then under construction, which greatly facilitated things there. Also attached
are the instructions I drew up for that purpose.
I accurately
measured a base line by tape, and established a series of setting-out points by
triangulation. With the aid of an electric Olivetti Divisuma calculator, I
calculated the co-ordinates of the upstream and downstream intersections of the
joints with the intrados and extrados of the arches at the various pouring
levels, as well as the exact centre of the extrados. This was before the advent
of computers, and was a very laborious calculating task, involving the
solutions of thousands of quadratic equations. In addition I calculated the
co-ordinates of the intersection of two lines: the line from the left hand
extrados intersection to the right hand intrados intersection and the line from
the right hand extrados intersection to the left hand intrados intersection. To
establish this point of intersection on the concrete of a previously cast box,
angles were calculated from three of the setting-out beacons. The surveyor’s
assistant – Elias, whom I brought along from Ebenezer, had a tripod fitted with
an optical plumb bob. He was directed by me from the one beacon to mark two
points along the calculated line, and mark that line by pencil on the concrete.
I then set up on the second beacon, to enable the assistant to mark the
intersection. I then went on the box with my tachy, orientated towards the
beacons I had used, and checked whether I was on the correct position by
pointing to a third beacon, thus not only checking the setting out, but also
the triangulation calculations. After that, I had the assistant marking the
direction of the lines towards the four corners of the box and to the centre of
the extrados, which also had been previously calculated. The corner points
themselves could not be marked directly, because three of the four corners were
then in mid-air, because of the overhang of the arch, as well as the joints.
The carpenters were supplied with a drawing showing the calculated distances
from the setting-out point to the corners and the centre of the extrados, as
well as the calculated offset at the centre of the extrados and other
calculated dimensions, such as the thickness. These enabled the carpenters to
check their work, as well as my own work, because any error would be shown,
whatever its source. As can be imagined, all these calculations were very
laborious indeed, and took up many man-months of high-level staff. Later, when
I was transferred to head-office, I attended a computer programming course from
IBM. As a practical problem, I calculated all these data for the Kat River Dam,
then under construction, which greatly facilitated things there. Also attached
are the instructions I drew up for that purpose.
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