Efficient application of radian laser tracker in 3D detection of shield segments

hield segment & tunnel quality and safety

Shield segment is the main assembly component of shield construction and the innermost barrier of tunnel. It bears the role of resisting soil pressure, groundwater pressure and some special loads. Shield segment is the permanent lining structure of shield tunnel. The quality of segment is directly related to the overall quality and safety of tunnel, and affects the waterproof performance and durability of tunnel. Therefore, the measurement and detection of shield segments is very important and the basic guarantee for the smooth implementation of the whole tunnel project. Its detection requirements and standards are also very strict.

Detection requirements

1. The flatness change of segment end face and side needs to be strictly controlled. If the change is too large, it will cause the assembly gap between rings and blocks, resulting in tunnel leakage and other problems.

2. The detection of the internal and external arc length of the segment, if the internal and external arc length of the segment exceeds the limit, will affect the overall assembly, resulting in extrusion or collision of the segment, and the wrong platform is easy to appear in the assembled tunnel.

3. The change of the detection angle of the segment angle will cause the connection difficulty in the segment assembly, and then cause the leakage of the bolt hole.

4. Inspection of segment mould segment mould may be deformed during production and later use. If it cannot be adjusted in time, it will lead to quality problems of the produced segments and further affect the quality of the later assembled tunnel.

5. With the continuous improvement of engineering quality standards and safety requirements, the accuracy of measurement and detection links in production is also improving. At this stage, the segment detection accuracy is usually required to be 0.25mm.

The traditional detection method of shield segments is mainly manual measurement with measuring tools and tools such as micrometer, template and feeler gauge. However, the manual measurement method is prone to uncertainties in the following links:

(1) Manual measurement is one-sided and can only measure point-to-point results, so it is difficult to feed back the real situation of each position of segment or die more comprehensively;

(2) It is difficult to ensure the measurement accuracy of some complex included angles;

(3) The change of temperature and humidity environment in the construction site is often complex. The large change of temperature and humidity in the morning, evening and noon is easy to cause the thermal expansion and cold contraction of the material itself, and it is difficult to take this part of the error into account in the comprehensive measurement results by manual measurement;

(4) Manual measurement has high technical requirements for operators, and it is difficult for different operators to maintain a high degree of consistency for measurement skills and reading skills, resulting in the increase of non objective factors of measurement;

(5) Manual counting and calculation are cumbersome, complex and error prone.

API solutions

According to the characteristics of shield segments and molds, all measurement requirements can be realized by using API brand radian series Laser Tracker for three-dimensional measurement, which is more objective and efficient than manual detection.

Simply set up the radian laser tracker at a suitable position next to the segment or die to be tested to start the measurement. When measuring, The operator holds the tracker target ball with built-in prism (SMR), the radian tracker will shoot laser to the center of the target ball and lock the tracking in real time. The operator only needs to touch the point to be measured with the target ball or slide the target ball against the surface to be measured. The radian tracker will accurately and efficiently collect the three-dimensional data of the position to be measured at the acquisition rate of 1000Hz, and feed back and record it in the software in real time for final analysis. All data will be collected After the collection, the corresponding reference points can be selected in the software to construct various lines, surfaces and bodies, analyze the geometric tolerance, load the digital simulation, and conduct the ratio and equivalence operation between the measured value and the nominal value, so as to achieve the purpose of detection.
Compared with the traditional manual measurement method, the use of radial laser tracker for segment detection has obvious characteristics and advantages:

1. Real time measurement and intensive sampling to fully reflect the real situation of segments or molds;
2. Complex included angle and irregular profile can also be measured accurately;
3. Integrated temperature and humidity compensation system (weather station) to automatically compensate temperature, humidity, altitude and other error factors;
4. Different operators can also achieve high repeatability of measurement and more objective detection data;
5. Automatic data analysis to reduce the calculation error rate to zero;
6. Automatically generate measurement report in the form of list, line chart, color difference chart, histogram, etc., which is efficient and intuitive;
7. Large measurement range and micron level( μ m. 1 / 1000mm) measurement accuracy, which can fully meet the requirements of segment and die detection accuracy.

conclusion
To sum up, the radian laser tracker has powerful functions and friendly operation. It can completely replace the traditional manual measurement method and become a more accurate, objective, efficient and convenient detection method for shield segments / molds.