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100 help planFirst, the scope of application of second-class precision leveling in construction
1. The regional elevation control network is deployed for joint testing and retesting, and the level points are encrypted.
2. Observation of settlement and deformation of structures, including tunnel surface settlement, vault subsidence, etc.
3. The design requires the use of second-class precision level measurement of the project.
2. Technical requirements for precision measurement
1. Requirements for measuring instruments
The instrument of precision leveling shall be determined according to the level of leveling, and the technical requirements of the first and second precision leveling instruments are shown in the following table.
2. Measurement requirements
First- and second-class precision leveling generally adopts single-line round-trip measurement. The round-trip measurement of a line must be carried out with fixed instruments, ruler pads, along the same road, and fixed personnel, that is, to achieve the "four fixes" in the measurement process, and reduce human error and accidental error as much as possible.
When observing the settlement of the structure, the principle of "five determinations" should be adhered to, that is, the reference point, the working base point and the point position of the settlement observation point used in the settlement observation should be fixedThe instruments and equipment used should be stable;Observers should be stable;The atmospheric environmental conditions at the time of observation should be basically the same;The observation route, lens position, procedure and method should be fixed.
The time of observation and the level of meteorological conditions should be observed when the scale reticle imaging is clear and stable. Observations should not be made in the following cases:
Within 30 minutes after sunrise and before sunset.
The sun is about 2h before and after the sky (according to the region, season and meteorological conditions, appropriate increase and decrease, the shortest time is not less than 2h);
When the image of the ruler reticle jumps violently;
When there is a sudden change in temperature;
When the wind is too strong and the ruler and instrument cannot be stabilized.