A paper on the measurement accuracy and measurement mode of high-speed railway engineering

Model paper on measurement accuracy and measurement mode of high-speed railway engineering

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According to the introduction, we have a simple understanding of the current development of high-speed railway survey. First of all, we should know that with the development of modern highway and railway engineering, the development of high-speed railways at home and abroad, especially in recent years, great changes have taken place in railway engineering survey, design, construction and operation organization. These changes are not only reflected in our prediction of the development prospect of railway engineering, but also in our grasp of the present situation of railway development. Railway engineering has developed rapidly, and survey engineers haven't had time to make full technical preparations, but we already need our new development model. Due to the needs of the situation, in addition to learning from foreign advanced technology, more discussion is to improve the measurement accuracy. In fact, in addition to properly improving the measurement accuracy, improving the measurement methods and processes, reducing costs and improving efficiency are the more important topics in railway engineering measurement at present. Below, this article will specifically talk about this aspect, and describe its problems and solutions.

1, the thinking of measurement engineers in various design institutes-from the aspects of economy, efficiency and quality, there are the following difficulties.

Every time the control survey of 1. 1 is upgraded, its funds will increase by about 40% and the observation time will be doubled. As far as the current situation is concerned, the survey period of most engineering projects is very tight. There are many considerations in the measurement of various design institutes, which are constantly being solved. First of all, funding is an important issue. We must ensure that our funds are controlled within a certain range. The effective and reasonable use and planning of funds plays a very important role in the implementation of our project. Without the support of funds, our measurement project can not be well developed and carried out smoothly.

1.2 second-class and third-class control network accuracy

The precision control of control network is an important aspect to ensure the accurate measurement of this project, and it is also an aspect that we should pay attention to. We know that the control network is based on the long side corresponding to ten to dozens of kilometers, and its density can not meet the needs of railway survey. When the short side is further encrypted, its accuracy will fall back to that of the first-class wire.

1.3 The layout of high-grade control network not only requires high accuracy, but also faces other difficulties: for example, there are few first-grade control points to start joint survey, adjustment calculation is different from that of low-grade control network, which is more complicated, astronomy and gravity survey need to be completed by more professional departments, and railway design institutes and engineering bureaus generally do not have survey ability. These problems need to be solved urgently. We must understand the causes and solutions of these problems, so as to fundamentally solve these problems and to a large extent, control these problems within the scope that we can solve and use.

1.4 It is not advisable to establish an independent second-class and third-class control network of high-speed railway without forcibly closing it to the national first-class control network for the following reasons:

1.4. 1 Independent coordinate system is generally used in small areas, and the earth surface can be approximately regarded as a plane without Gaussian projection. The long railway passes through several provinces, and its spherical characteristics can not be ignored.

1.4.2 does not have the ability to carry out high-precision astronomical and gravity surveys, and the control network of several hundred kilometers is narrow and linear, so its accuracy is difficult to control. Precision control is an important aspect in the process of engineering survey, and it is also an aspect that we can actually implement.

1.4.3 existing topographic maps of various scales, roads, rivers, cities, institutions, etc. All the routes along the line are located in the unified geodetic coordinates of the whole country, and the railway has found another way, so it is difficult to straighten out the relevant relations. Topographic map survey is carried out according to the actual situation, and it is also an important way for us to measure railway engineering. We must ensure that the railway survey has a certain realistic foundation and research support.

2. Suggestions for the new measurement process

In order to implement the new survey method, it is an important method for us to solve the high-speed railway engineering survey. In order to reverse this situation and eliminate the systematic error after setting out on the drawings, it is necessary to make the following changes to the railway survey process.

2. 1 One-time network layout combines the original flight control, encryption fourth-class control points, initial survey traverse and fixed survey intersection points into a pair of GPS points with a distance of 3 ~ 5 km or traverse with a side length of 500 ~1000 m, and the relative accuracy is115 ~. In addition to eliminating the systematic difference between topographic map and spot with the same name, it also has the following main functions:

2. 1. 1 Simplify the measurement procedure and reduce the measurement workload. We should simplify the measurement procedure as much as possible and control the measurement workload within our control. At the same time, we will have more confidence in the smooth progress of the project, and the measures implemented will be more effective, which will make us better understand the procedural process.

2. 1.2 survey, design and construction only use the data of laying nets and controlling piles once, and the data is simple and clear with little error. The support of data is the basic guarantee for our engineering investigation, and it is also an important consideration for engineering investigation and design. Simplifying data and procedures is an important aspect and necessary solution to ensure the smooth progress of railway projects.

2.2 If the central line is directly measured from the control point of the primary network, the mode of railway survey can be changed. The accuracy of railway engineering survey has always been a concern of survey engineers, but the accuracy of railway survey has never affected the design and construction. The problem lies in the measurement error and the measurement data processing error. Clarify the relationship between each measurement link, simplify the measurement process to make it more concise, clear and standardized, and gradually replace uncontrollable field measurement with easy-to-control indoor work.

2.3 coordinate control setting-out has obvious advantages.

2.3. 1 Re-survey the middle pile directly from the control point of the primary network, without long-distance and continuous turning points, thus avoiding error accumulation. The progress of a project is bound to be accompanied by engineering errors. How to deal with errors quickly and effectively is an indispensable step in the process of engineering survey, and it is also a step that we should try to avoid. We can't guarantee zero errors, but we can at least guarantee to minimize the occurrence of errors and the wrong solutions.

2.3.2 Any mileage can be measured by cutting in. As long as the line is not changed, there will be no broken chain. This feature makes the mid-line survey discontinuous, and the bridge and tunnel section can be surveyed first, so that the majors of geology, bridges and tunnels can start their work as soon as possible. After improving the accuracy of aerial survey, middle piles can be set only in key sections, and general subgrade can be measured directly on aerial survey model.

2.4 Measuring transverse profile from aerial survey model has been studied and put into use by many foreign institutions. Foreign countries adopt 1/3000 ~ 1/5000 large-scale photography, or do small-scale photography at the initial survey, and then do large-scale photography at the final survey. Many domestic units, especially the design institutes under the Ministry of Railways, have carried out research, but the accuracy can not reach the tolerance stipulated in the Code for Surveying New Railway Engineering.

3. Conclusion

As mentioned above, the author puts forward some conclusions and views on the measurement accuracy and measurement methods in the process of railway engineering survey. Railway engineering implementation is an important part of modern railways in China, and railway engineering survey is also an important aspect of railway engineering implementation. These points are closely related and need our joint consideration. Only by doing these preparations well, and at the same time doing some preventive measures and error analysis, can we solve the possible problems in the process of railway engineering survey, and also make the development of our railway engineering better and better, and the development of our railway engineering survey will be smoother and smoother.

2 1 Introduction to the Measurement Precision and Measurement Mode of High-speed Railway Engineering

Transportation industry is closely related to the development of national economy. Today, with the rapid development, China is vigorously developing the construction of high-speed railway, and the national requirements for high-speed railway engineering survey are also constantly improving, and the technical requirements for high-speed railway survey are also getting higher and higher. Generally speaking, the traditional measurement technology has some shortcomings, even can't keep up with the development of the times. Therefore, it is necessary to apply advanced measurement technology to high-speed railway engineering survey. China's high-speed railway engineering survey technology has been continuously improved to adapt to the development of China's high-speed railway construction. Only by ensuring the accuracy requirements of engineering survey can the development needs of high-speed railway be well met.

2 high-speed railway engineering survey

2. 1 contents of high-speed railway engineering survey

As far as railway construction is concerned, whether it is railway survey and design, engineering construction, acceptance and maintenance after the completion of the project, these are inseparable from the accurate measurement of the project. Engineering survey needs to run through the whole process of high-speed railway construction, which is of great significance to high-speed railway construction. High-speed railway engineering survey also includes track construction survey, high-speed railway plane elevation control survey, railway operation and maintenance survey and many other aspects. The accuracy of these measurements is an important basis to ensure the quality of high-speed railway construction, so railway engineering related staff must attach great importance to engineering measurement.

2.2 The purpose of high-speed railway engineering survey

In the process of high-speed railway engineering construction, all the work is to ensure the quality and safety of high-speed railway engineering, and high-speed railway engineering survey is no exception. Engineering survey is mainly based on the actual situation of high-speed rail project, reasonably designing all levels of plane elevation control network, and then effectively implementing all construction links in the project construction under the control of precision survey network, and finally successfully completing the construction of high-speed rail. Because the construction of high-speed railway has high requirements for all aspects, the construction of railway line should be carried out according to the actual situation of railway engineering and the designed line type when surveying high-speed railway engineering. In order to ensure the smoothness of the track, the accuracy should be controlled in the range of millimeters to ensure the comfort and safety of the vehicle.

2.3 Requirements of high-speed railway survey technology

Track is the key construction link of high-speed railway. High-speed rail track can be generally divided into ballasted track and ballastless track. Ballastless track has better ride comfort and stability than ballasted track, and its durability is also greatly improved. However, it should be noted that ballastless track requires very high quality of engineering foundation. If there are problems such as settlement of engineering foundation, it will not only affect driving safety, but even lead to disaster. This puts forward extremely high requirements for engineering measurement accuracy. In addition, it is difficult to adjust the ballastless track after the construction is completed. Therefore, in order to avoid error accumulation in many links, high-speed rail engineering survey must have strict control network standards.

3 high-speed railway engineering survey technical problems

3. 1 Quality problems caused by measuring instruments

In the actual railway engineering survey, the quality problems and improper use of measuring instruments are important factors leading to the inaccuracy of engineering survey data, which are mainly manifested as follows: ① The measuring instruments are relatively backward and cannot meet the requirements of the current engineering survey standards. In some projects, in order to save costs, new instruments cannot be replaced in time, and old measuring instruments are still used, so the measurement accuracy is difficult to guarantee. (2) When using measuring instruments for engineering survey, surveyors often rely on their own experience to measure the project, and do not use instruments in accordance with relevant specifications, which may easily make the measured data inconsistent with the actual situation and eventually lead to quality problems in railway engineering; (3) the instrument is not managed according to relevant regulations, resulting in instrument distortion. For engineering measuring instruments, management and maintenance need professionals, and other personnel can't use or place them at will to prevent the instrument from losing its accuracy.

3.2 Failure to control the measurement quality.

The quality monitoring of high-speed railway engineering involves not only the quality of railway engineering, but also the safety of people's lives and property, which requires not only the supervision of relevant departments, but also the functional supervision of the government. The government and social supervision should cooperate with relevant departments to carry out project acceptance, and the quality of high-speed rail can not be ignored. However, many project supervisors failed to shoulder their due responsibilities and did not evaluate the project quality according to the requirements of the supervisors. Secondly, some supervisors failed to use suitable measuring instruments to supervise the project, which will greatly affect the quality of supervision.

3.3 Engineering measurement error.

3.3. 1 GPS measurement error

For the first two stages of high-speed rail engineering survey, it is necessary to carry out GPS survey. This method is prone to errors, and the sources of errors can be divided into the following three categories:

(1) Errors related to the control segment, including ephemeris error and satellite clock error, refer to the errors of navigation message parameter values during satellite propagation.

(2) The receiver-related error is usually caused by receiver noise.

(3) The error related to the satellite signal refers to the error caused by the influence of the communication medium between the receiver and the satellite.

3.3.2 CP Ⅲ controls the measurement error.

The measurement method of CP ⅲ control network is the form of free station setting of total station in rear intersection. The main sources of error are:

(1) The free station error caused by observation error is mainly due to the direction observation error;

(2) Relative error of plane position and elevation of two adjacent stations;

(3) The total station measures the error of each point of the track.

4. Solutions to engineering survey problems

4. 1 Promote the technical innovation of engineering survey

Our society is constantly developing, and for railway engineering survey technology, it also needs constant innovation. Applying advanced science and technology to engineering survey can effectively improve the technical level of railway engineering survey. Science and technology are the primary productive forces. In a sense, the improvement of measurement technology and measurement standards can not only reduce the cost of high-speed rail engineering survey, but also ensure the progress and quality of high-speed rail engineering construction. Therefore, China should promote the further development and innovation of high-speed railway engineering survey technology to ensure the smooth development of China's high-speed railway industry.

4.2 Strengthen the formulation and implementation of various systems of high-speed railway engineering survey.

This includes strictly observing relevant management measures in the aspects of retest, handover and construction process of high-speed rail engineering survey results, so as to standardize engineering survey behavior and ensure the quality of high-speed rail engineering survey results. Nowadays, with the continuous development of high-speed railway engineering construction, the accuracy of railway construction technology requirements is getting higher and higher. The person in charge of the high-speed railway project should focus on the long term and introduce advanced and practical equipment and instruments according to the actual development situation, so as to lay a good foundation for improving the measurement quality of the high-speed railway project and provide power for the high-speed railway project in China.

4.3 Strengthen the supervision and management of engineering survey.

Put the supervision of high-speed railway engineering survey in the first place. (1) The staff must know every detail in the process of high-speed railway engineering survey, and abide by the corresponding standards and specifications. The construction personnel cannot only rely on their own work experience to carry out the survey. (2) High-speed rail engineering surveyors should shoulder their own responsibilities, strictly control the survey data, and review the obtained data repeatedly to ensure that the data is foolproof. In the application of high-speed railway engineering survey data to practice, it is necessary to verify the data again. The authenticity and validity of data is the first prerequisite to ensure the quality of railway engineering. Therefore, the supervision work must be effectively implemented.

4.4 weaken the engineering survey error

4.4. 1 Measures to reduce GPS measurement error

The errors caused by satellite clocks are systematic errors, including random errors of clocks and errors caused by frequency offset and clock difference. This error can often be reduced by differential technology and clock error correction method. In addition, there is ephemeris error, and high-precision relative coordinates can be obtained by phase observation difference method, thus weakening or eliminating the error. For high-precision long-distance measurement, precise star history attenuation can be used. In addition, orbit improvement method and synchronous difference method can reduce the overall ephemeris error.

To eliminate the errors related to satellite propagation, we can solve the problem that ionospheric refraction makes the code phase measurement longer and the carrier phase shorter, or we can choose a specific time period to observe and then eliminate the errors by synchronous observation difference method.

The difference method can be used to deal with the errors related to the receiving station. If high-precision positioning is needed, an external frequency standard can be used to provide a high-precision time standard for the receiving station. Or the clock error of the receiver is treated as an independent unknown quantity when solving.

4.4.2 weakening of CP ⅲ control error

We can't completely eliminate the error caused by total station measurement, so we can only take certain measures to reduce the error reasonably. The vertical roughness of each point in the measured trajectory is related to the observation height angle, the observation horizontal direction is related to the horizontal roughness, and the positive vector error is related to the measurement distance and error angle. In order to reduce the error of positive vector, it is necessary to control the error of observation distance and observation angle and minimize the observation distance.

5 conclusion

Engineering survey is a very important link in engineering construction, and the accuracy of engineering survey will play a great role in the construction quality of engineering projects. Before construction, engineering survey technology should be adopted to re-verify the measurement results. Once the survey technology has problems, the whole project may have serious quality problems. The construction of high-speed railway project is a systematic and complicated project, and the smoothness of railway track must be ensured to ensure the safe and stable operation of high-speed trains. Therefore, the technical requirements of high-speed railway engineering survey are very high. In order to make the high-speed railway develop better and faster, it is necessary to continue to study the engineering survey technology and strengthen the supervision of the high-speed railway engineering survey. Under the strict assessment system, the staff will have a highly responsible working attitude and be able to complete their own engineering investigation tasks seriously, thus promoting the rapid development of high-speed railway projects in China.

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