Wojciech Janusz (red.) - Monographic Series No 14
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Improvement of rules and methods of metrological verfication of leveling staffs and geodetic monitoring of displacement
Part 1.
Wojciech Janusz
Galibration of the sets: digital level – code staff
Chapter 1 includes description of the works aimed at construction of comparator for checking code staffs in vertical position with the use of laser interferometer and digital levels. In 2002 comparator adjusted to checking deviations from staff metric graduation was constructed at the Department of Applied Geodesy, Institute of Geodesy and Cartography; the method of checking was based on fixed staff and vertically movable digital level. In 2003 the comparator was modified in such a way, that digital level was stabilized, while staff was moved. In this method lower part of 3-meter (or longer) staff was tested in its normal vertical position, while upper part in reverse position with simultaneous inversion of readouts of digital level.
In 2007 comparator was modified once again, so now the whole staff can be checked in normal vertical position. Description of this re-construction and its background was given in chapter 2.
Procedures of measurements and calibration calculations were included in chapter 3. Using the constructed comparator random and systematic deviations of graduation from nominal division are checked every 10 cm, which is assumed as optimal interval (certainly it is possible to make checking in smaller intervals). Procedure of making measurements used for comparing lengths of graduation measured with digital level and laser interferometer was presented. The author also presented procedure of calculating random deviations v and random errors mh of graduation lengths expressed in μm, as well as systematic deviations A of graduation lengths and errors mA expressed in μm/m.
In chapter 4 exemplary examinations of the selected staffs, applied for technical leveling performed with the use of digital levels, were described.
4 fiberglass sliding staffs T for technical leveling, used in conjunction with DL101C digital level, were tested, as well as 2 telescope staffs used in conjunction with Leica DNA 03 digital level. It was found, that random errors dh of sliding staffs reach 25 – 35 μm, while systematic deviations are within 0 – 90 μm/m. Telescope staffs were characterized by similar random errors of graduation of segments as sliding staffs, however it was found, that gross errors appear in places of segment joints, reaching even 800 μm.
In chapter 5 exemplary examinations of code staffs for precise leveling using digital levels were discussed.
Two LD13 staffs for precise leveling, which are used with DiNi12 digital levels, were examined. It was found, that random errors of graduation for both staffs checked with the use of both digital levels reached mh = 4 μm, while deviations v were distributed randomly. Systematic deviations A determined with the use of both levels reached 7 and 7 μm/m for first staff, while 4 and 5 μm/m for second staff, respectively. These results reveal, that both checked staffs and both levels proved to be accurate, qualifying them for precise leveling. The results also confirmed high accuracy of calibration measurements.
It results from the experience gained during examining several tens of staffs in the period 2003 – 2007, that in case of staffs with good graduation, not disturbed locally when compared with nominal graduation, random errors mh determined with the use of digital level on IGiK comparator are between 4 – 5 μm, while systematic deviations A, determined with mA = 1 μm/m, are within +/- 15 μm/m. More frequently staff graduations are characterized by positive value of A parameter; it means that tape in the staffs is tensed less than nominally.
In chapter 6 construction-practical features of staffs for precise leveling, which are important for keeping high quality of graduation made on invar tape, were discussed. Special attention was put to cause and effect analysis of the results of calibration of those staffs, which have too high errors mh, nonrandom distribution of deviations v and too large systematic deviations A of staff graduation. The results of comprehensive analysis of reasons of excessive errors mh , which was done at calibration laboratory at the Mining-
Metallurgical Academy in Cracow, were cited. Additional analysis of the effects of deviations, which have impact on repair works and on possibilities of further use of staffs, was also carried out.
Part 2.
Jerzy Janusz, Wojciech Janusz
Examination of Displecement and thermal changes of intake chamber of pumped-storace power station "Żarnowiec" due to emptying water reservoir
Method of conducting supplementary computations, concerning measurements of displacements of points and benchmarks located on the construction and inside it, was the scope of the presented work, as well conclusions derived from the results of computations.
In most cases geodetic monitoring of displacements is completed, when displacements of points located on the construction and inside it are measured and computed. In the presented work the determined displacements of points, further treated as pseudo-observations, were used for additional calculations, aimed at determination of parameters of displacements of the whole construction or its particular fragments. This approach enables to observe behaviour of the construction itself, not only of the geodetic points, which were located on it. Such supplementary calculations and analysis of their results are the element of geometric interpretation of the results of measurements, which is done by surveyor responsible for monitoring and can help designers in making causal consecutive interpretation of the measurements.
Geometrical interpretation should be treated as a “bridge” between specialists dealing with various aspects of monitoring of safety of built and exploited constructions. It helps in improving evaluation of the results of measurements in the process of detecting causes of specific behaviour of constructions and their foundations.
Horizontal displacements of 4 points and vertical displacements of 24 benchmarks located on ferroconcrete water construction were additionally analysed in the presented work. These displacements occurred due to emptying the adjoining water reservoir and due to increase of air temperature.
Part 3.
Jerzy Janusz, Wojciech Janusz, Andrzej Kaliński
Preliminary examination of deflection of base under water reservoir
At first part of the work authors presented the results of measurements of displacements of outer part of embankments and terrain around water reservoir due to its filling and emptying. It was found, that as a result of filling reservoir with 15 mln m3 of water, i.e. increase of loading of base under reservoir depending on depth from 0 to 3 kG/cm2, settlements can be observed at its surroundings, which are characterized by unit indices wHj (displacements due to 1-meter change of water level), equal to 0.7 mm/m on the top of embankment and 0.5 mm/m at the edge zone of outer escarpment of embankment. The settlements due to changes of loading reservoir disappear at the distance of 200 – 250 m. It was also found, that while filling reservoir horizontal displacements appear on the top of embankment; their vectors are directed towards reservoir. Unit index wPj characterizing decrease of figure created by points on the embankment due to loading reservoir reaches 0.8 ppm/m (0.000 0008 for 1 m of difference of water level).
Shape of deflection of base on the area surrounding reservoir suggests, that within reservoir vertical displacements caused by changes in filling can be much higher.
The concept of determining vertical displacements of reservoir bottom was presented; it is based on trigonometric levelling measurements of displacements of metal masts fixed on the bottom. Method of measurements and results concerning displacements of bottom of reservoir close to its center were discussed. As a result of measurements vertical displacement reaching –29 mm was observed; it was caused by increase of water level by 10 m.