Method for establishing and measuring long tunnel independent control network

Abstract

The invention discloses a method for establishing and measuring an independent control network of a long and large tunnel, which optimizes the establishment of the control network of the long and large tunnel under an unreasonable condition and minimizes a run-through error. The method comprises the following steps: firstly, calculating whether an engineering actual projection deformation value (a bridge is deformed) is subjected to control network optimization or not, performing compensation surface return-to-zero calculation when the engineering measurement deformation requirement is not met, re-optimizing the projection surface elevation, and establishing a control network in a one-point-one-direction manner; and performing deflection angle calculation according to the maximum transverse offset of the optimized control network, performing field verification of the field control network after secondary rotation, and confirming that the optimized control network is a final construction control network when the transverse offset of the two coordinate systems at the lap joint after rotation is within 5mm.

Description

Technical Field

[0001] The invention belongs to the technical field of plane coordinate control networks, and in particular relates to a method for establishing and measuring an independent control network for a long tunnel. Background Art

[0002] The design length of high-speed railway tunnels ranges from a few kilometers to dozens of kilometers. At present, the longest high-speed railway tunnel reaches 42km. As a long tunnel construction control measurement, the establishment and calculation method of the control network are particularly important. The high-speed railway standard requires that the projection deformation per kilometer should not exceed 10mm / km, and the engineering measurement standard requires 25mm / km. The coordinate system provided by the design basically meets the above requirements. However, there are many objective factors in the construction measurement control, such as instrument accuracy error, observation condition error, construction error, human error and other influencing factors. It is difficult to achieve the expected penetration accuracy. Even if the penetration accuracy is met, there are still tunnel clearance violations in the strict completion acceptance of the high-speed railway, and various dimensions do not meet the specification requirements, resulting in increased costs in the later stage.

[0003] Traditional plane control networks try to expand their scope as much as possible while meeting the requirements of the specifications, mainly to facilitate the measurement of the entire line. However, in actual construction, due to various external environmental influences, the accuracy of the measurement penetration error is ultimately difficult to meet the requirements. Even if the construction measurement meets the specification limit requirements of 10mm / km or 25mm / km, the plane position of the later structures in the tunnel will be greatly affected after the tunnel is penetrated.

[0004] The entrance of Jixinling Tunnel of the TJ04 contract section of Wuzhen Expressway constructed by China Railway 12th Bureau is located in Changchayuanzi Village, Yulin Township, Xujia Town, Wuxi County, Chongqing City, and the exit is located in Sanping Village, Huaping Township, Zhenping County, Shaanxi Province. It is a two-way double-hole four-lane expressway tunnel. This tunnel is an extra-long two-way four-lane large-section highway tunnel with a maximum tunnel burial depth of 1105.7m. The route is north-south and is designed as a separated double-hole six-lane. The distance between the left and right lines is about 40m, and the designed driving speed is 80km / h. The center mileage of the left line of the tunnel is ZK45+633.0, the starting and ending mileages are ZK42+540.0-ZK48+726.0, and the length is 6186.0m. The center mileage of the right line of the tunnel is YK45+645, the starting and ending mileages are YK42+570.0-YK48+720.0, and the length is 6150.0m;

[0005] The original GNSS design coordinates are the first-level control network required by the Highway Survey Specifications (JTGC10-2007). The deformation value K per kilometer is calculated by projection deformation to be 65.2 mm. Calculated according to the full length of the tunnel, without considering the influence of other external conditions, the penetration error is 216.5 mm. Coupled with the influence of various subjective factors, it will directly affect the position of the structure in the tunnel and the clearance limit size of the tunnel. Summary of the invention

[0006] In order to overcome the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a method for establishing and measuring an independent control network for a long tunnel. The measurement technology is mainly to optimize the unreasonable establishment of the control network for a long tunnel and reduce the penetration error to a minimum. First, calculate the actual projection deformation value of the project (the bridge is deformed) to determine whether to optimize the control network. Perform zeroing calculation on the compensation surface when the deformation requirements of the project measurement are not met. Re-optimize the projection surface elevation and establish the control network using one point and one direction. Calculate the deflection angle based on the maximum lateral offset of the optimized control network. After a second rotation, conduct a field verification of the on-site control network to ensure that the lateral deviation of the two sets of coordinate systems at the overlap after rotation is within 5 mm before confirming that the optimized control network is the final construction control network.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A method for establishing and measuring an independent control network for a long tunnel, characterized in that it comprises the following steps:

[0009] Step 1) Before establishing the control network, collect design data and on-site topographic and geological data. Design data includes the plane coordinate system and elevation system of the original design control network. Geological data includes geological data provided by the design and on-site survey, geological longitudinal section and profile;

[0010] Step 2) Survey the actual location of the control points set up by the design institute, and analyze the geological stability and surrounding environment to see if they affect GNSS reception signals;

[0011] Step 3) Calculating the projection deformation value is to check whether the design control network can meet the specification requirements and the tunnel penetration error tolerance. If it does not meet the requirements, the compensation surface calculation should be performed to calculate the sum of the deformation caused by the unreasonable selection of the projection surface elevation of the current design control network and the deviation of the tunnel from the central meridian, and then infer the elevation surface to be used. The calculation formula is as follows:

[0012]

[0013] Wherein, K: projection deformation value (m), M: distance of the tunnel's horizontal coordinate Y value offset from the central meridian (km), R: radius of earth curvature (6371000), H: average tunnel elevation (m), H: design projection elevation (m). When the K value is greater than 10 mm / km, compensation surface calculation should be performed, assuming that the projection deformation K is zero, and using the formula to inversely calculate the actual elevation value of h. The formula is as follows:

[0014]

[0015] Wherein, H: compensation surface projection elevation (m), K: projection deformation value (m), M: tunnel horizontal coordinate Y value offset from the central meridian distance (km), R: earth curvature radius (6371000), H: tunnel average elevation (m);

[0016] Step 4) when calculating deformation value does not meet specification or tunnel penetration requirement, need to set up plane independent coordinate system, one is based on national coordinate system, carry out projection transformation, guarantee to meet the requirement that projection length deformation is not more than 1.0cm / km (highway 2.5cm / km) in survey area or urban area, the independent coordinate system set up, the second is to take a point as starting point, take the direction of this point and another point nearby as starting direction, set up independent coordinate system, take the head and tail one point in coordinate system as starting point to calculate with the actual starting azimuth of head and tail two points, carry out adjustment calculation and obtain coordinate with the corner data of GNSS actual measurement; Comprise to set up independent control network and measure with straight tunnel center line, set up independent control network and measure when tunnel is positioned at curve and set up independent control network and measure three kinds of modes when being parallel to tunnel main axis:

[0017] Step 5) The independent control network of the compensation surface is established. After the independent control network is established in the tunnel, due to the influence of the deformation value, there will be directional (lateral) and mileage (longitudinal) deviations with the adjacent structures of the tunnel. The mileage deviation can be solved by breaking the chain; for the lateral deviation, the independent control network must be rotated twice. The established independent control network is rotated clockwise and counterclockwise by an angle to coincide with the center line of the adjacent structure, so that the entire line is smoothly connected. The rotation angle is calculated by subtracting the lateral deviation of the original construction coordinate system direction point from the lateral deviation of the same point after the independent control network is divided by the total distance and then performing actan (β). Negative values ​​rotate counterclockwise, and positive values ​​rotate clockwise. The calculation method is as follows:

[0018] Calculation formula: β = actan (d / D);

[0019] Where, β: rotation angle, d: lateral distance difference between two coordinate systems G12 and G12' (m), D: distance from G05 to G12 (m), when β angle is positive, it rotates clockwise, when it is negative, it rotates counterclockwise;

[0020] Step 6) The coordinates of the independent control network points are obtained through theoretical calculation through the rotated independent control network. Due to the inconsistency of the projection deformation value of each control point caused by the actual terrain height difference change, the compensation surface elevation calculation is also obtained through theoretical calculation, so the control network after the second rotation must be verified by on-site stakeout before the results can be submitted; two sets of coordinates of the two control points at the tunnel exit are used on-site to stake out at least two mileage points on the center line of the line (the interval mileage should be ≧2m) for verification, and the longitudinal mileage deviation and lateral deviation are measured on-site. The deflection angle is calculated by measuring the lateral deviation and the rotation is repeated. When the lateral deviation is less than 5mm, the independent control network is confirmed as the final control network, and the longitudinal mileage difference is set as a broken link;

[0021] Step 7) Since the projection surface of theoretical calculation is affected by objective factors, there is an error in the connection of the two sets of coordinate center lines on site. The lateral deviation d' is measured by on-site layout and the deflection angle is calculated again for correction. The calculation formula is as follows:

[0022] Calculation formula: β' = β + actan (d' / D);

[0023] Among them, β' is the deflection angle of the secondary calculation, β: rotation angle, d: the lateral distance difference between the two coordinate systems G12 and G12' (m), D: the distance from G05 to G12 (m);

[0024] When the β angle is positive, rotate clockwise, and when it is negative, rotate counterclockwise. Repeat the calculation using the above formula until the lateral deviation of the two sets of coordinates is within 5 mm. The final result of the independent control network can be determined, and the final longitudinal deviation is set as a broken chain.

[0025] The methods for establishing an independent control network and measuring based on the centerline of a straight tunnel include the following:

[0026] The origin of coordinates is the centerline point of the inlet, and the direction is the X-axis azimuth of 0°. To ensure that there are no negative values ​​in the coordinates within the structure, the origin coordinates X and Y can be assigned. The lateral distance of the offset line can be directly seen through the Y value. If a rectangular coordinate system is not established separately, the coordinates provided by the design can be used to take the G05 origin design coordinates as the starting point, and the coordinate system can be established with 05 and G11 inverse azimuths as the calculated azimuths. The projection surface elevation uses the calculated compensation surface elevation for overall adjustment.

[0027] When the tunnel is located on a curve, the methods for establishing an independent control network and measurement include the following:

[0028] A coordinate control network is established with the tangent as the X-axis and the vertical tangent as the Y-axis. The measurement and calculation methods are the same as those established with the centerline of a straight tunnel.

[0029] Methods for establishing independent control networks and measurements when parallel to the main axis of the tunnel include the following:

[0030] Without considering the influence of terrain on the centerline, an open and stable position is selected as the starting point at the tunnel entrance. The designed intersection stakes can also be used. The coordinate values ​​are the designed point coordinates. The direction is the coordinate azimuth calculated by back-calculating a fixed point at the tunnel exit. The projection surface elevation is the calculated compensation surface elevation for overall adjustment.

[0031] The beneficial effects of the present invention are:

[0032] The present invention is mainly to optimize the unreasonable establishment of the control network of long and large tunnels, and reduce the penetration error to the minimum. First, calculate the actual projection deformation value of the project (the bridge is deformed) to determine whether to optimize the control network. Perform zero calculation on the compensation surface when the deformation requirements of the project measurement are not met, and re-optimize the projection surface elevation to establish the control network using one point and one direction. Calculate the deflection angle based on the maximum lateral offset of the optimized control network, and perform field verification of the on-site control network after secondary rotation to ensure that the lateral deviation of the two sets of coordinate systems at the overlap after rotation is within 5mm before confirming that the optimized control network is the final construction control network.

[0033] According to the on-site conditions, we used compensation projection to establish an independent control network, set the projection deformation value to 0, and reversed the actual elevation surface (950m) and the design projection surface (550m), which differed by 400 meters. After secondary rotation, the final tunnel penetration error was only 13.4mm. This achieved economic benefits and reduced the risk of tunnel rework. Through the establishment and calculation method of the independent control network of Wuzhen Expressway, it is believed that this method is simple and easy to understand, easy to calculate, and provides experience for the independent control network of long and large tunnels.

[0034] The present invention improves the tunnel penetration accuracy, promotes the use of independent control networks in the industry, and reduces the cost risk caused by penetration errors. The present invention has a wide range of applications, especially for railways, highways and long tunnels. The use of this method to establish a control network for long-span bridges can greatly improve the relative accuracy of the bridge axis, especially for long-span bridges with large height differences, ensuring that the squat span length meets the specification requirements, providing a reference for the measurement of similar projects.

[0035] Economic Benefits

[0036] The adoption of the present invention greatly improves the penetration accuracy of long and large tunnels, ensures the tunnel clearance and the correct position of various structures, reduces the large penetration error caused by the low and unreasonable control network accuracy, and rework of structures, which greatly saves costs. According to Article 8.6.2 of the "Engineering Surveying Code" (GB50026-2007), the penetration error of the opposite construction center line of the tunnel project on the penetration surface should meet the requirements in the following table.

[0037]

[0038] The construction length of the entrance of this tunnel is 2870m, and the construction length of the exit is 3316m. According to the specification, the tolerance shall not be greater than 150mm. The penetration section of this tunnel is grade IV surrounding rock. The penetration error of the traditional process is 216mm, which is greater than the tolerance requirement, while the penetration error of the present invention is 13.4mm, which fully meets the specification requirements. According to the specification requirements, the excess part needs to be replaced with an arch. The replacement length is calculated based on 200 meters for each opening. The use of the present invention can save at least 1.306 million yuan. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic diagram of a method for establishing a straight tunnel according to the present invention;

[0040] Figure 2 A schematic diagram of a method for establishing a curved tunnel according to the present invention;

[0041] Figure 3 A schematic diagram of a method for establishing a tunnel in parallel with the present invention;

[0042] Figure 4 It is a schematic diagram of the secondary rotation of the present invention;

[0043] Figure 5 It is a schematic diagram of on-site setting out adjustment of the present invention;

[0044] Figure 6 Check the local large-scale drawing for on-site setting out of the present invention;

[0045] Figure 7 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0046] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0047] like Figure 7 As shown, a method for establishing and measuring an independent control network for a long tunnel is characterized by comprising the following steps:

[0048] 1) Before establishing the control network, collect design data and on-site topographic and geological data. The design data includes the plane coordinate system and elevation system of the original design control network.

[0049] 2) Geological data include geological data provided by the design and on-site investigation, investigation of geological longitudinal sections and profiles.

[0050] 3) Survey the actual location of the control points set up by the design institute, and analyze the geological stability and surrounding environment to see if there is any impact on GNSS reception signals.

[0051] 4) Calculating the projection deformation value is to check whether the design control network can meet the specification requirements and the tunnel penetration error tolerance. If it does not meet the requirements, the compensation surface calculation should be performed to calculate the sum of the deformation caused by the unreasonable selection of the projection surface elevation of the current design control network and the deviation of the tunnel from the central meridian, and then infer the elevation surface to be used. The calculation formula is as follows:

[0052]

[0053] K: Projection deformation value (m)

[0054] M: The distance (km) from the central meridian of the tunnel's horizontal coordinate Y value

[0055] R: radius of curvature of the earth (6371000)

[0056] H: average tunnel elevation (m)

[0057] H: Design projection elevation (m)

[0058] When the K value is greater than 10mm / km, the compensation surface calculation should be performed, the projection deformation K is assumed to be zero, and the actual elevation value of h is calculated using the formula. The formula is as follows:

[0059]

[0060] H: Compensation surface projection elevation (m)

[0061] K: Projection deformation value (m)

[0062] M: The distance (km) from the central meridian of the tunnel's horizontal coordinate Y value

[0063] R: radius of curvature of the earth (6371000)

[0064] H: average tunnel elevation (m)

[0065] 5) When the calculated deformation value does not meet the specification or tunnel penetration requirements, it is necessary to establish a plane independent coordinate system. Gaussian plane coordinates are the most commonly used coordinate form. However, in some scenarios, the coordinate system provided by the state or design institute cannot meet the actual needs, and an independent coordinate system needs to be established to solve the problem. There are two ways to establish an independent coordinate system. One is to use the national coordinate system as the basis, perform projection transformation, and ensure that the projection length deformation within the survey area or city is not greater than 1.0cm / km (2.5cm / km for highways). The coordinate system established by this method is also called the compensation coordinate system. It is more suitable for larger cities and larger areas, and has strict conversion parameters with the national 3° and 6° zones. The second is to directly use a point as the starting point, and use the direction of this point and another nearby point as the starting direction to establish an independent coordinate system. This method is suitable for narrow and long structures and small areas. This method mainly uses the head and tail points in the coordinate system as the starting points and the actual starting azimuths of the head and tail points for calculation, and uses the GNSS measured corner data for adjustment calculation to obtain coordinates. Advantages of this method: It reduces the distance difference between GNSS and total station caused by unreasonable selection of projection surface, improves relative accuracy; reduces the number of constraint points, improves the accuracy between constraint points; the selection of projection surface is relatively reasonable, and the penetration accuracy is high:

[0066] like Figure 1 As shown in the method of establishing a straight tunnel, the method of establishing a control network with the center line of a straight tunnel is intuitive and simple. The coordinate origin is the inlet center line point, and the direction is the coordinate X-axis direction 0°. To ensure that there are no negative values ​​in the coordinates within the structure, the origin coordinates can be set to X=10000, Y=10000 (any value can be assigned). This method is also intuitive for construction and layout, and the lateral distance of the offset line can be directly seen through the Y value; if a rectangular coordinate system is not established separately, the coordinates provided by the design can be used to take the G05 origin design coordinates as the starting point, and the coordinate system can be established with 05 and G11 inverse azimuths as the calculation azimuths. The projection surface elevation uses the calculated compensation surface elevation for overall adjustment.

[0067] like Figure 2 As shown in the method for establishing a curved tunnel, method 2 is a method for establishing an independent control network when the tunnel is located on a curve. The coordinate control network is established with the tangent as the X axis and the vertical tangent as the Y axis. The measurement method and calculation method are the same as method 1, as shown in Figure 3 Parallel to the tunnel establishment method shown.

[0068] Method 3 is to establish an independent control network coordinate system parallel to the main axis of the tunnel. This method is relatively simple and does not need to consider the influence of the terrain on the centerline. An open and stable position can be selected at the entrance of the tunnel as the starting point. The design intersection can also be used. The coordinate value uses the design point coordinates, and the direction uses the coordinate azimuth calculated from a fixed point at the tunnel exit. The projection surface elevation uses the compensation surface elevation for overall adjustment. The control network established by this method is simple and flexible, and is commonly used to establish independent control networks for long tunnels.

[0069] 6) Step 5) is only to establish an independent control network for the compensation surface. During construction, it is often divided into several sections for joint construction. Even if there is only one section, after the independent control network is established in the tunnel, due to the influence of the deformation value, there will be directional (lateral) and mileage (longitudinal) deviations with the adjacent structures of the tunnel. The mileage deviation can be solved by breaking the chain; for the lateral deviation, the independent control network must be rotated twice, and the established independent control network must be rotated clockwise and counterclockwise by an angle to coincide with the center line of the adjacent structure, so that the entire line is smoothly connected. The rotation angle is calculated by subtracting the lateral deviation of the direction point of the original construction coordinate system from the lateral deviation of the same point after the independent control network is divided by the total distance and then performing actan (β). Negative values ​​rotate counterclockwise, and positive values ​​rotate clockwise. Calculation method and Figure 4 The schematic diagram of the secondary rotation is as follows:

[0070] Calculation formula: β = actan (d / D)

[0071] β: rotation angle

[0072] d: Horizontal distance difference between two coordinate systems G12 and G12' (m)

[0073] D: Distance from G05 to G12 (m)

[0074] When the β angle is positive, it rotates clockwise, and when it is negative, it rotates counterclockwise.

[0075] 7) The coordinates of the independent control network points are obtained through theoretical calculation after the rotation of the independent control network. Due to the changes in the actual terrain height difference, the projection deformation values ​​of each control point are inconsistent. The compensation surface elevation calculation is also obtained through theoretical calculation. Therefore, the control network after the second rotation must be verified by on-site layout before the results can be submitted. Two sets of coordinates of the two control points at the tunnel exit are used on-site to layout at least two mileage points on the center line of the line (the interval mileage should be ≧2m) for verification. The longitudinal mileage deviation and lateral deviation are measured on-site, and the deflection angle is calculated by measuring the lateral deviation and rotating again. When the lateral deviation is less than 5mm, the independent control network is confirmed as the final control network. At this time, the longitudinal mileage difference is set to a broken link. The on-site layout adjustment is shown as follows Figure 5 As shown:

[0076] 8) If Figure 6As shown in the local large-scale drawing of on-site layout verification, due to the influence of various objective factors on the projection surface of theoretical calculation, there are errors in the connection of the center lines of the two sets of coordinates on site. The lateral deviation d' is measured by on-site layout and the deflection angle is calculated again for correction. The calculation formula is as follows:

[0077] Calculation formula: β' = β + actan (d' / D)

[0078] β' deflection angle of the second calculation

[0079] β: rotation angle

[0080] d: Horizontal distance difference between two coordinate systems G12 and G12' (m)

[0081] D: Distance from G05 to G12 (m)

[0082] When the β angle is positive, it rotates clockwise, and when it is negative, it rotates counterclockwise.

[0083] By repeatedly calculating the above formula until the lateral deviation of the two sets of coordinates is within 5mm, the final result of the independent control network can be determined, and the final longitudinal deviation is set as a broken chain.

[0084] Example

[0085] Jixinling Tunnel starts from Chayuanzi Village, Yulin Township, Xujia Town, Wuxi County, and ends at Sanping Village, Huaping Township, Zhenping County, Shaanxi Province. It is a two-way four-lane highway tunnel with a design speed of 80km / h. The distance between the left and right lines is about 40m. The mountain top elevation in the tunnel site is generally 1100-2100m, and the relative elevation is greater than 1000m. The tunnel runs through Jixinling in a north-south direction. The overall terrain is high in the middle and low at both ends. The lowest point of the axis ground is located at the tunnel entrance, with an elevation of 900m, and the highest point is Jixinling. The top of the mountain has an elevation of 2034m and the maximum buried depth of the tunnel is about 1100m. The center mileage of the left line of the tunnel is ZK45+633.0, the starting and ending mileages are ZK42+540.0-ZK48+726.0, and the length is 6186.0m. The center mileage of the right line of the tunnel is YK45+645, the starting and ending mileages are YK42+570.0-YK48+720.0, and the length is 6150.0m. The total length of the double tunnels is 12331.0 meters. The slope / length of the longitudinal section of the left line is: 2.35% / 123.446m, 1.9% / 6015.162m, -0.842% / 42.392m; the slope / length of the longitudinal section of the right line is: 2.35% / 150.178m, 1.9% / 5971.416m, -0.842% / 28.409m.

[0086] Application status and effects;

[0087] After on-site investigation, there are two problems with the design control network and data of Wuzhen Expressway: First, the original design coordinate results are the first-level control network required by the "Highway Survey Specification" (JTGC10-2007), which has low accuracy and cannot meet the requirements of tunnel construction; second, the original design control network projection surface selection is unreasonable, and the projection deformation is 65.2mm per kilometer, which makes it difficult to ensure the correct penetration of the tunnel. After data analysis and discussion by the survey team, an independent control network was established. On the basis of setting the projection deformation to 0, the projection surface was recalculated, and one point one direction was used for calculation. After secondary rotation and on-site verification, various parameters of the control network were finally determined. After the tunnel was penetrated, the on-site measured lateral penetration error was only 13.8mm, which verified that this method of establishing a high-precision independent control network for the tunnel was reliable and simple to calculate, ensuring that the various structural dimensions of long and large tunnels meet the requirements of the specifications, and reducing the direct economic cost of rework caused by large tunnel penetration errors. The Zaosheng Tunnel of Yinxi Railway and Taibaishan Tunnel of Meitai Expressway in subsequent construction both use this method to establish independent control networks, with high penetration accuracy and significant results, which ultimately produced good economic and social benefits.

Claims

1. A method for establishing and measuring an independent control network for a long tunnel, characterized in that: The steps include: Step 1) Before establishing the control network, collect design data and on-site topographic and geological data. Design data includes the plane coordinate system and elevation system of the original design control network. Geological data includes geological data provided by the design and on-site survey, geological longitudinal section and profile; Step 2) Survey the actual location of the control points set up by the design institute, and analyze the geological stability and surrounding environment to see if they affect GNSS reception signals; Step 3) Calculating the projection deformation value is to check whether the design control network can meet the specification requirements and the tunnel penetration error tolerance. If it does not meet the requirements, the compensation surface calculation should be performed to calculate the sum of the deformation caused by the unreasonable selection of the projection surface elevation of the current design control network and the deviation of the tunnel from the central meridian, and then infer the elevation surface to be used. The calculation formula is as follows: Wherein, K: projection deformation value (m), M: distance of the tunnel's horizontal coordinate Y value offset from the central meridian (km), R: radius of earth curvature (6371000), H: average tunnel elevation (m), H: design projection elevation (m). When the K value is greater than 10 mm / km, compensation surface calculation should be performed, assuming that the projection deformation K is zero, and using the formula to inversely calculate the actual elevation value of h. The formula is as follows: Wherein, H: compensation surface projection elevation (m), K: projection deformation value (m), M: tunnel horizontal coordinate Y value offset from the central meridian distance (km), R: earth curvature radius (6371000), H: tunnel average elevation (m); Step 4) when calculating deformation value does not meet specification or tunnel penetration requirement, need to set up plane independent coordinate system, one is based on national coordinate system, carry out projection transformation, guarantee to meet the requirement that projection length deformation is not more than 1.0cm / km (highway 2.5cm / km) in survey area or urban area, the independent coordinate system set up, the second is to take a point as starting point, take the direction of this point and another point nearby as starting direction, set up independent coordinate system, take the head and tail one point in coordinate system as starting point to calculate with the actual starting azimuth of head and tail two points, carry out adjustment calculation and obtain coordinate with the corner data of GNSS actual measurement; Comprise to set up independent control network and measure with straight tunnel center line, set up independent control network and measure when tunnel is positioned at curve and set up independent control network and measure three kinds of modes when being parallel to tunnel main axis: Step 5) The independent control network of the compensation surface is established. After the independent control network is established in the tunnel, due to the influence of the deformation value, there will be directional (lateral) and mileage (longitudinal) deviations with the adjacent structures of the tunnel. The mileage deviation can be solved by breaking the chain; for the lateral deviation, the independent control network must be rotated twice. The established independent control network is rotated clockwise and counterclockwise by an angle to coincide with the center line of the adjacent structure, so that the entire line is smoothly connected. The rotation angle is calculated by subtracting the lateral deviation of the original construction coordinate system direction point from the lateral deviation of the same point after the independent control network is divided by the total distance and then performing actan (β). Negative values ​​rotate counterclockwise, and positive values ​​rotate clockwise. The calculation method is as follows: Calculation formula: β = actan (d / D); Where, β: rotation angle, d: lateral distance difference between two coordinate systems G12 and G12' (m), D: distance from G05 to G12 (m), when β angle is positive, it rotates clockwise, when it is negative, it rotates counterclockwise; Step 6) The coordinates of the independent control network points are obtained through theoretical calculation through the rotated independent control network. Due to the inconsistency of the projection deformation value of each control point caused by the actual terrain height difference change, the compensation surface elevation calculation is also obtained through theoretical calculation, so the control network after the second rotation must be verified by on-site stakeout before the results can be submitted; two sets of coordinates of the two control points at the tunnel exit are used on-site to stake out at least two mileage points on the center line of the line (the interval mileage should be ≧2m) for verification, and the longitudinal mileage deviation and lateral deviation are measured on-site. The deflection angle is calculated by measuring the lateral deviation and the rotation is repeated. When the lateral deviation is less than 5mm, the independent control network is confirmed as the final control network, and the longitudinal mileage difference is set as a broken link; Step 7) Since the projection surface of theoretical calculation is affected by objective factors, there is an error in the connection of the two sets of coordinate center lines on site. The lateral deviation d' is measured by on-site layout and the deflection angle is calculated again for correction. The calculation formula is as follows: Calculation formula: β' = β + actan (d' / D); Among them, β' is the deflection angle of the secondary calculation, β: rotation angle, d: the lateral distance difference between the two coordinate systems G12 and G12' (m), D: the distance from G05 to G12 (m); When the β angle is positive, rotate clockwise, and when it is negative, rotate counterclockwise. Repeat the calculation using the above formula until the lateral deviation of the two sets of coordinates is within 5 mm. The final result of the independent control network can be determined, and the final longitudinal deviation is set as a broken chain.

2. The method for establishing and measuring an independent control network for a long tunnel according to claim 1, characterized in that: The methods for establishing an independent control network and measuring based on the centerline of a straight tunnel include the following: The origin of coordinates is the centerline point of the inlet, and the direction is the X-axis azimuth of 0°. To ensure that there are no negative values ​​in the coordinates within the structure, the origin coordinates X and Y can be assigned. The lateral distance of the offset line can be directly seen through the Y value. If a rectangular coordinate system is not established separately, the coordinates provided by the design can be used to take the G05 origin design coordinates as the starting point, and the coordinate system can be established with 05 and G11 inverse azimuths as the calculated azimuths. The projection surface elevation uses the calculated compensation surface elevation for overall adjustment.

3. The method for establishing and measuring an independent control network for a long tunnel according to claim 1, characterized in that: When the tunnel is located on a curve, the methods for establishing an independent control network and measurement include the following: A coordinate control network is established with the tangent as the X-axis and the vertical tangent as the Y-axis. The measurement and calculation methods are the same as those established with the centerline of a straight tunnel.

4. The method for establishing and measuring an independent control network for a long tunnel according to claim 1, characterized in that: Methods for establishing independent control networks and measurements when parallel to the main axis of the tunnel include the following: Without considering the influence of terrain on the centerline, an open and stable position is selected as the starting point at the tunnel entrance. The designed intersection stakes can also be used. The coordinate values ​​are the designed point coordinates. The direction is the coordinate azimuth calculated by back-calculating a fixed point at the tunnel exit. The projection surface elevation is the calculated compensation surface elevation for overall adjustment.

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