Swimming plumb bob
The swimming plumb line (also referred to as the inverted plumb line ) is a structure for determining the plumb line and its deviations. This is used in civil engineering for observations of behavior and stability.
Instead, as in normal string pendulum solders ( weight Slot ) to use a weight for tensioning a wire at the lower end, the solder wire is anchored in the float line at the lowest point and the Lotspannung by the lift ( buoyancy generated) of an upper-end float, located in can move freely in an oil or water-filled container. This aligns the wire so that it is perpendicular through the fixed point.
A coordiscope can be installed for manual measurement and a telelot for automated measurement.
Use in dams
From an inspection pass at the foot of the dam, a vertical hole is made that extends so deep into the ground that it can be assumed that this point will not shift even if the dam moves.
This makes it possible to determine displacements of the barrier relative to the ground. Usually swimming plumb bobs and a weight plumb bob are designed in such a way that they can be mathematically linked. This makes it possible to reference the relative displacements that are determined with the weight plumb bob absolutely relative to the fixed point of the floating plumb bob.
By using a solder wire deflection probe, a point can be assumed as a temporary fixed point at any depth of the hole and the corresponding deflection of the solder wire read off. This makes it possible to determine the bending line.
The deflection probe consists of a guide tube with a longitudinal slot, which is guided in the center of the bore by rollers mounted on the ends. The solder wire is fed through the longitudinal slot into the probe and held in the center by additional rollers. The probe is then inserted into the hole and lowered to the desired depth using a pull rope.
literature
- Heribert Kahmen: Applied Geodesy: Surveying. Walter de Gruyter, Berlin 2006, ISBN 978-3-110-18464-8 .
- Peter Rißler: dam practice. R. Oldenburg, Munich 1998, ISBN 978-3-486-26428-9 , p. 323 f.
- Konrad Bergmeister , Frank Fingerloos, Johann-Dietrich Wörner: Concrete Calendar 2011: Power Plants, Fiber Concrete. Ernst & Sohn, Berlin 2011, ISBN 978-3-433-02954-1 , p. 250.