Engineering survey paper

Engineering investigation usually refers to various investigation theories, methods and technologies adopted in the investigation, design, construction and management stages of engineering construction. I sorted out the papers on engineering survey below, hoping to be helpful to everyone.

Cross-section surveying and mapping is a very important link in tunnel engineering, but the traditional cross-section surveying and mapping operation mode has the characteristics of complex field survey procedures, low positioning accuracy, heavy workload of indoor data processing and low efficiency, which is mainly due to the great limitations of traditional surveying and mapping methods and data sorting and analysis. Therefore, in order to improve the work efficiency and final accuracy, it is necessary to combine advanced measuring instruments to improve the measuring method, so as to improve the efficiency of drawing and data analysis.

1 tunnel section characteristics and measurement difficulties

Tunnel section has two main characteristics, one is the diversification of shape, and the other is the relatively large area. These characteristics of tunnels have been puzzling the traditional cross-sectional surveying and mapping methods, resulting in some unmeasurable situations. For example, the cross-sections of some diversion tunnels cannot be measured by traditional level or theodolite. With the development of science and technology, the application of electronic measuring instruments in tunnel cross-section measurement is more and more extensive, but there are still some limitations: ① the cross-section is still drawn by hand in the industry; (2) The placement position of the prism will not be in the same section, resulting in a large error; (3) It is not easy to choose the placement position of the prism, especially in large tunnels, cranes and other mechanical equipment are often used.

2 GPS survey and design tunnel engineering control network

The establishment of tunnel engineering control network is basically similar to other projects, and is usually set as an independent control network. The main basis is the tunnel's environmental/topographic conditions, its own length, existing instruments and equipment, and the prescribed breakthrough error.

Using GPS positioning technology to construct tunnel plane control network has many advantages: ① the efficiency of network construction is relatively high, and the observation work can be improved by 5~ 10 times compared with triangulation; (2) (2) GPS network has low requirements for graphic angles or conditions, and the spacing and number of points are optional, so it is only necessary to arrange control points that can intervisibility each other at the mouth of the cave; ③ The workload of calculation and inspection is much lower than that of triangulation, which is easy to meet the specification requirements; ④ No matter how long the tunnel is, it can be used in a wide range.

Study on improved method of tunnel section measurement

3. 1 Use prism-free total station to measure, and use Excel and Auto CAD software to draw sections.

3. 1. 1 data collection method

Data acquisition is mainly carried out by laser, and positioning is carried out by using coordinate system. The X-axis is the cavern axis of the tunnel, and the origin is the starting point of the cavern axis.

3. 1.2 Drawing the section.

After measuring the field data, connect the total station to the computer, open the office software of the total station, and import the data into the Excel table. The sectional view reflects the two-dimensional plane perpendicular to the axis of the cavern, that is, the Y value and the H value. Therefore, when the Y values of tunnel sections are very close, the fixed coefficient of Y values of each section should be increased according to the pile number to generate the section spacing, but the added values of Y values of different points in the same section should be consistent to avoid overlapping when drawing the section automatically (see Figure 1).

3. 1.3 Advantages of this method

Generally speaking, the above method is a feasible and efficient method for surveying and mapping tunnel sections.

Its advantages are: using Auto CAD to draw profile automatically, which solves the trouble of manual drawing and reduces the tasks in the office; ② The positioning accuracy of field work is improved, and the application of advanced electronic equipment simplifies the measurement procedure, usually only two field surveyors are needed; (3) The measurement data is intuitive, and the calculation process is simplified without complicated transformation. According to the statistical results of this method in practical application, this method improves the work efficiency by about 40% [1].

3.2 AMT.3000 profiler application

3.2. 1 AMT.3000 working principle of profiler

AMT.3000 profiler is an organic combination of electronic measuring instrument and laser ranging. Using AMT.3000 profiler, the measured data can be directly stored in memory and imported into the computer. Its ranging principle is simple, that is, the distance can be measured after the laser irradiates the cross section. It can freely rotate 360 in the horizontal direction of the section, and can change the measured density at any time.

3.2.2 operation mode of amt.3000

Mainly divided into the following three steps:

(1) positioning, that is, choose the location of profiler. In general, the profiler is installed at a known position, and the prism is placed at this position to measure the three-dimensional coordinates, and the data will be automatically counted in the memory.

(2) Start the analyzer. After setting up the profiler, follow the prompts in the menu, and automatic measurement will be carried out after starting the profiler. Its field work is controlled by Tun software of Husky handheld measuring computer.

(3) Data analysis and profile drawing. After the positioning measurement data recorded in the profiler memory are imported into the computer, all the data are analyzed by AMT.3000 profiler software. There are usually three ways: interactive, man-machine dialogue and automatic analysis. On this basis, the computer system will automatically draw the profile [2].

3.3 CASS6.0 with prism-free total station

3.3. 1 tunnel section data collection

It adopts the data acquisition method of subsection coding. The tunnel section is closed, and its specific requirements are as follows: ① The station should be erected at the tunnel centerline, and when inputting coordinates, the elevation value is the relative value from the station position to the design section height; (2) When stepping on the points, the first measurable point at the left bottom end of the tunnel direction should be upward in turn, and the code n (that is, the section number) of each point should be recorded, so as to measure the code Mn of zenith distance point to the maximum extent; Then rotate the telescope horizontally by 180, and measure from the first measurable point near the right side of zenith distance, and the last point is the visible point at the bottom of the right side, thus ending the sampling point of the whole section.

3.3.2 Office data processing

(1) measurement data transmission. Different from the above methods, coding, after data transmission, needs to re-determine whether the coding and the order of points are wrong. The basic steps are as follows: after clicking the menu "Engineering Application"-"Generate Mileage File"-"Generate from Coordinate File", the computer will pop up a dialog box for finding data files, find and click the imported file, enter a new file name and save it, and select (2) in the command bar that appears, and the section transformation is completed.

(2) Draw the tunnel section. There are two methods to generate tunnel profile: ① the method of inputting design parameters; ② Choosing the existing design line, the former is more difficult to realize and the latter is more practical. The basic steps are as follows: Click Engineering Application-Earthwork Calculation of Tunnel Section-Draw Section Diagram, and select the data file just imported from the selected mileage file in the dialog box [3] that appears.

3.4 Using image processing to realize tunnel section measurement

3.4. 1 Basic ideas

In order to measure and calculate tunnel section, it is necessary to import the edge information of tunnel section into related systems. However, in the actual engineering construction, the large area illumination of tunnel section is weak, and the edge characteristics are not obvious. At this time, the edge of the tunnel is brightened by the glow device, and the edge of the input image is obvious, and then the Laplace operator template is used for detection.

After the edge detection of the image, the image is thinned and curve-fitted, and an annular directed discrete dot matrix can be generated. Here is a brief introduction to the fitting method of circular thinning graphics. First of all, the grid mentioned above should have a logical midpoint corresponding to it. With this point as the boundary, the screen is divided into 12 parts, and the data points of each part are set in the horizontal direction, and then curve fitting is carried out. Then, the fitting results are adjusted to the original direction to generate a directed ring composed of discrete lattice.

In the above different regions, the rotation formula of coding is different. All areas are arranged counterclockwise, with the vertical axis as the bisector, and the area with positive vertical axis is the first area. The rotation formula is usually:

x2=x 1cos T+y 1sin T

y2=y 1cos T-x 1sin T

Then curve fitting is carried out to restore the results.

Implementation steps

In this method, the tunnel section measurement system is written in Visual Basic, the calculation system is programmed in Fortran and Visual C++, and the measurement data is transmitted by dynamic link library. Its basic steps mainly include the following steps: ① input images through a camera; ② Import the image into the image processing system, and define the coordinate point and scale; ③ Image area processing and curve fitting; ④ Import the section size, define the standard elevation value and calculate the section area value; ⑤ Transform the curve discretization into inverse discrete data lattice; ⑥ Calculate all sections and save the results to a disk file; ⑦ Output data results in the form of tables or graphs.

Example introduction

Through the field measurement of a tunnel by the above method, the table 1 is the comparison between the measurement results of the above method and the manual measurement results, as well as the calculation error. It can be seen that the results processed by the tunnel section measurement system can meet the accuracy required by engineering construction.

4 conclusion

Advanced science and technology have promoted the development of surveying and mapping engineering, provided it with fast, safe and effective measurement methods, and achieved good results. The tunnel conditions are different, so it will play a greater role to choose reasonable and effective methods and combine them in the survey process.

refer to

[1] Peng Yonggang, Cao Bizheng. An Improved Method of Surveying and Mapping Tunnel Section [J]. Northwest Hydropower, February 2006:12 ~13.

Hao Yadong, Guo. Tunnel survey with AMT.3000 profiler [J]. Urban survey, 2004,04: 41~ 44.

[3] Song Yuan Bing. Application of CASS6.0 combined with prism-free total station in tunnel section survey [J]. Journal of Hebei Institute of Civil Engineering and Architecture, 2006,01:78 ~ 79.

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