A method for lightening the underground tunnel traverse survey

Abstract

The application discloses a kind of underground tunnel lightening traverse surveying method, it is related to engineering surveying technical field, comprising the following specific steps: S1: tunnel hole outside control network type is drafted, the through error prediction of hole outside control network is carried out;S2: the simulation model of control network is established, the tunnel in through error is calculated, and the measurement result under the error environment of simulation measurement is simulated;S3: tunnel hole outside GNSS control network arrangement and measurement are carried out;S4: the tunnel in traverse control point position is buried by the determined traverse point position layout scheme;S5: tunnel in traverse measurement and distance are two-corrected, and then traverse measurement result is used to guide tunnel excavation.The application effectively controls error accumulation, improves the reliability of hole control network, completely eliminates traditional error, prism insertion can be observed, ensures the consistency of multi-measurement return, long-period observation data, reduces the load of survey personnel, reduces operation cost, improves measurement efficiency.

Description

Technical Field

[0001] This invention relates to the field of engineering surveying technology, and in particular to a lightweight traverse surveying method for underground tunnels. Background Technology

[0002] Underground tunnel control surveying is divided into two parts: outside the tunnel and inside the tunnel. The purpose of establishing a tunnel control network is to ensure that the tunnel can be accurately completed, so that all buildings and structures can be built according to their designed positions and geometric shapes without encroaching on the building clearance. Different types of projects have different tunnel completion error requirements.

[0003] When surveying underground tunnels, satellite signals cannot be obtained inside due to the special environment. Therefore, traverse surveying methods must be used. However, existing traverse surveying methods are very expensive, require a lot of manpower, and have low efficiency.

[0004] There are generally two control survey methods currently used for underground tunnels: traverse and geodetic quadrilateral or 4-6-sided double traverse. Traverse is laid out linearly and advances along a single line. Its advantages are simple and flexible layout, and low surveying workload. Its disadvantages are a lack of redundant observations and low accuracy. Geodetic quadrilateral double traverse involves setting up pairs of points at each location, with each station observing two targets before and after the current point, totaling four target points. Its advantages are a significant increase in redundant observations, increased traverse closure check conditions, and improved overall network reliability and accuracy. Its disadvantages are a large workload and the need for six people on-site. The 4-6-sided double traverse has the same point layout as the geodetic quadrilateral double traverse, requiring observations along 4-6 sides forming a loop. Its accuracy is slightly lower than the geodetic quadrilateral double traverse, and it is currently a commonly used method for tunnel control network surveying. However, it requires at least five people on-site, resulting in high labor costs and low surveying efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a lightweight traverse surveying method for underground tunnels to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A novel tunnel control network is established using a new method for simulating tunnel penetration error. Control points are laid out on the bottom slab and the secondary lining sidewalls. The bottom slab points are centering points, and the sidewall points are insertion-type forced centering control points. Traverse measurements are performed on the bottom slab control points on the same side and the control points on both sidewalls. The traverse measurement method includes the following specific steps: S1: Based on the tunnel length and the visibility at the tunnel entrance, determine the network type of the external control network and estimate the connection error of the external control network; S2: Establish a simulation model of the control network, calculate the tunnel breakthrough error inside the tunnel, and combine it with the breakthrough error outside the tunnel to obtain the comprehensive breakthrough error inside and outside the tunnel. Establish random functions for angle observation and distance observation, simulate the measurement results under the error environment of actual measurement, and form a batch of simulation results by comparing with theoretical values ​​and determine whether they meet the breakthrough requirements. S3: Conduct GNSS control network layout and measurement outside the tunnel, perform data processing, and complete the prediction of tunnel breakthrough error after verification; S4: The work of laying out the control points of the traverse in the tunnel is carried out by using the determined traverse point layout plan. S5: Conduct traverse surveys and distance corrections within the tunnel, perform adjustment and accuracy assessments, and then use the traverse survey results to guide the tunnel excavation.

[0007] Preferably, the configuration of the tunnel external control network in step S1 is as follows: Based on the tunnel length, select the measurement accuracy level; based on the visibility at the tunnel entrance, select GNSS control points outside the tunnel, determine the type of control network outside the tunnel, and predict the connection error of the control network outside the tunnel. The mean square error of the lateral breakthrough outside the tunnel is calculated using formulas for angle measurement and distance measurement. The mean square error of the lateral breakthrough before the control survey is:

[0008] In the formula, These are the projected lengths of the coordinate errors of the inlet and outlet GNSS control points on the through surface, respectively. These are the lengths from the inlet and outlet GNSS control points to the breakthrough point, respectively. These are the azimuth mean square errors of the GNSS connection line at the inlet and outlet, respectively. These are the angles between the line connecting the entrance and exit control points to the connection point and the normal line of the connection point; After verification following GNSS measurements, the mean square error for lateral penetration is:

[0009] In the formula, , , Let x and y represent the variance and covariance of the difference between the x and y coordinates calculated from the inlet and outlet to the connection point, respectively. Indicates the azimuth angle of the through surface.

[0010] Preferably, the simulation model establishment method in step S2 is to simulate the tunnel control network, draw the diagram in the mapping software, measure angles and distances to establish the model table, calculate the error ellipse of the weakest point in the tunnel based on the model, compare it with the theoretical value, form a batch of simulation results, and determine whether the simulation data and data standard deviation meet the requirements for tunnel breakthrough.

[0011] Preferably, the formula for predicting the lateral penetration error of the calculation model in step S2 is:

[0012]

[0013] In the formula, E represents the mean square error of the lateral connection; E represents the major semi-axis of the ellipse representing the calculation error of the traverse point model; F represents the minor semi-axis of the ellipse representing the calculation error of the traverse point model. The tangent azimuth of the tunnel breakthrough face is the coordinate azimuth of the tunnel axis; T is the azimuth corresponding to the major axis E of the error ellipse.

[0014] Preferably, the random function for simulating the error in the measured data in step S2 is implemented with a mean of 0 and a standard deviation of the mean error of the measurement accuracy class. In Excel, taking a tunnel with a second-order angle of 1.3″ and a distance of 2mm as an example, the implementation method is as follows: Angle = NORMINV(RAND(),0,0.00013); Distance = NORMINV(RAND(),0,0.002).

[0015] Preferably, the formula for calculating the standard deviation distribution of the simulated measured data in step S2 is:

[0016] Where m is the sample standard deviation. The deviation between the traverse points of each through-face and the simulated value is given. for The sum of n, where n is the total number of samples.

[0017] Preferably, the error ellipse calculation step for the weakest point inside the hole in step S2 is as follows: The error ellipse parameters of the weakest point inside the tunnel are calculated using the variance-covariance matrix of the traverse network. The weakest point inside the tunnel is usually near the tunnel breakthrough face. The parameters include the major semi-axis, minor semi-axis, and azimuth. The requirement is that the mean square error of the plane position of the weakest point and the mean square error of the tunnel breakthrough limit after comprehensive calculation outside the tunnel meet the requirement, ensuring that the breakthrough error is within the allowable range.

[0018] Preferably, in step S3, the arrangement and measurement of the GNSS control network outside the tunnel is carried out using a dual-frequency GNSS receiver, through static observation, and the instrument leveling and centering are completed before the observation. The traverse network layout adopts the method of double forced centering points on the side walls. When measuring the traverse at each station inside the tunnel, one tripod, one base, three single prisms, and two prism inserts are required for the foresight and backsight. The work of foresight and backsight includes inserting two forced centering prisms and setting up one tripod for prism centering and leveling. All the work of foresight and backsight is completed by one person.

[0019] Preferably, in step S4, the timing for burying the control points inside the tunnel is as follows: the bottom slab control points should be buried after the bottom slab concrete is poured and reaches the design strength, and the side wall control points should be buried after the secondary lining concrete is poured, the formwork is removed, and the secondary lining concrete strength meets the standard. The control points of the base plate are drilled by impact drill. After cleaning the debris in the holes, epoxy resin mortar is injected, and a locating pin with forced centering is inserted. The top of the locating pin is flush with the surface of the base plate, and the surrounding area is sealed with sealant to prevent moisture.

[0020] The side wall insertion forced centering control point adopts a customized insertion embedded part. The fixing sleeve is pre-embedded before the secondary lining concrete is poured. The centering rod is installed after the concrete is formed. The deviation between the centering rod center and the design point is ≤±1mm.

[0021] Preferably, in step S5, according to the predetermined tunnel control measurement accuracy level, the tunnel traverse measurement is carried out to complete the field distance measurement and side measurement work; then, the distance is corrected by two-dimensional adjustment, and the adjustment and accuracy evaluation are performed. In the field, the horizontal angle was measured by the repetition method, and the control points of the bottom plate on the same side and the control points of the side walls on both sides were observed simultaneously. In the data processing, the distance was corrected for meteorological and projection corrections. First, meteorological corrections were performed, and then projection corrections were performed. Adjustment calculations were performed using traverse network adjustment software to perform plane coordinate adjustment and elevation adjustment of closed traverses or attached traverses. Based on the adjustment results, the tunnel breakthrough error should be recalculated. If the error exceeds the expected range, the cause should be analyzed, and measures including but not limited to supplementary measurement, remeasurement, or densification of control points should be taken.

[0022] The technical effects and advantages of this invention are as follows: (1) This invention utilizes the formulation of the tunnel external control network type and the establishment of the model to calculate the tunnel breakthrough error. By combining the breakthrough error inside and outside the tunnel and establishing random functions of angle observation and distance observation, it simulates the measurement results under the error environment of actual measurement. Before the formal measurement, it can predict whether the breakthrough error exceeds the limit, realizing the transformation from post-correction to pre-control, greatly reducing the risk of measurement failure or rework, and improving the reliability of the tunnel internal control network. (2) The present invention adopts a new type of control network, which takes into account the traditional invert arch point while adding control points for the secondary lining side wall. The forced centering control point of the side wall eliminates the human error and leveling error of the traditional optical centering. The prism can be inserted for observation, ensuring the consistency of multiple measurement and long-term observation data, reducing the load on the surveyors, reducing the operating cost, and improving the measurement efficiency. (3) This invention establishes a complete distance reduction process including meteorological correction to projection correction, and introduces a weighting strategy based on measured accuracy and post-test variance component estimation in the adjustment, which ensures seamless connection between the measured ground distance and the construction coordinate system, avoids deviation caused by length deformation, and improves the authenticity and reliability of the output point coordinates. Attached Figure Description

[0023] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a flowchart illustrating the overall steps of the present invention; Figure 2 This is a diagram of the wire mesh of the present invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] This invention provides, for example Figures 1-2 This paper presents a lightweight traverse surveying method for underground tunnels.

[0026] Example 1: A novel tunnel control network was established using a new method for simulating tunnel breakthrough error. Control points were set up on the bottom slab and the sidewalls of the secondary lining. The bottom slab points were set up as centering points, and the sidewall points were set up as insertion-type forced centering control points. Traverse measurements were taken of the bottom slab control points on the same side and the control points on both sides of the sidewalls. The number of observation targets at each station was consistent. There were 2 forced centering control points on the sidewalls and 1 bottom slab control point on the same side. The double forced centering points on the sidewalls were used.

[0027] The traverse measurement method includes the following specific steps: S1: Based on the tunnel length and the visibility at the tunnel entrance, determine the network type of the external control network and estimate the connection error of the external control network; The proposed network type for the control network outside the tunnel is as follows: Based on the tunnel length, the measurement accuracy level is selected, and the accuracy level is selected according to the technical requirements of tunnel plane control measurement. Based on the visibility at the tunnel entrance, the selection of external GNSS control points, the determination of the external control network type, and the prediction of the connection error of the external control network are carried out. The selected external GNSS control points should be located in areas with stable foundations, no settlement, good visibility, and far away from vibration sources (such as construction machinery and main traffic roads). The spacing between the points should meet the observation requirements, and the visibility conditions with the control points inside the tunnel should be good. The mean square error of the lateral breakthrough outside the tunnel is calculated using formulas for angle measurement and distance measurement. The mean square error of the lateral breakthrough before the control survey is:

[0028] In the formula, These are the projected lengths of the coordinate errors of the inlet and outlet GNSS control points on the through surface, respectively. These are the lengths from the inlet and outlet GNSS control points to the breakthrough point, respectively. These are the azimuth mean square errors of the GNSS connection line at the inlet and outlet, respectively. These are the angles between the line connecting the entrance and exit control points to the connection point and the normal line of the connection point; After verification following GNSS measurements, the mean square error for lateral penetration is:

[0029] In the formula, , , Let x and y represent the variance and covariance of the difference between the x and y coordinates calculated from the inlet and outlet to the connection point, respectively. Indicates the azimuth angle of the through surface.

[0030] S2: Establish a simulation model of the control network. The modeling process involves drawing in professional engineering modeling software, such as AutoCAD or Southern CASS, according to the actual tunnel axis, control point layout scheme, observation distance and angle. The coordinates of the GNSS control points outside the tunnel and the coordinates of the planned traverse points inside the tunnel are entered. The simulation model is established by simulating the tunnel control network, measuring angles and distances to create a model table, calculating the error ellipse of the weakest point inside the tunnel based on the model, calculating the tunnel breakthrough error according to the formula, and combining it with the breakthrough error outside the tunnel to obtain the comprehensive breakthrough error inside and outside the tunnel. The steps for calculating the error ellipse of the weakest point inside the cave are as follows: The variance-covariance matrix of the traverse network, a commonly used technique in existing surveying, is used to calculate the error ellipse parameters of the weakest point inside the tunnel. The weakest point inside the tunnel is usually near the tunnel breakthrough surface. The parameters include the major semi-axis, minor semi-axis, and azimuth. The requirement is that the mean square error of the plane position of the weakest point and the mean square error of the tunnel breakthrough limit after comprehensive calculation outside the tunnel must meet the requirement, ensuring that the breakthrough error is within the allowable range.

[0031] The formula for predicting the lateral penetration error of the calculation model is as follows:

[0032]

[0033] In the formula, E represents the mean square error of the lateral connection; E represents the major semi-axis of the ellipse representing the calculation error of the traverse point model; F represents the minor semi-axis of the ellipse representing the calculation error of the traverse point model. The tangent azimuth of the tunnel breakthrough face is the coordinate azimuth of the tunnel axis; T is the azimuth corresponding to the major axis E of the error ellipse.

[0034] Establish random functions for angle and distance observations, simulate measurement results under experimental error conditions, generate batch simulation results by comparing with theoretical values, and determine whether they meet the requirements for consistency. That is, compare with the theory to determine whether the simulation data and data standard deviation meet the requirements for consistency. Random function setting: Based on the standard error of the selected measurement accuracy level, a normal distribution random error model is constructed to simulate the error of the measured angle and distance. The random function for simulating the standard error of the measured data is implemented with a mean of 0 and a standard deviation of the standard error of the measurement accuracy level. The implementation method in Excel, taking a tunnel with a second-order angle of 1.3″ and a distance of 2mm as an example, is as follows: Angle = NORMINV(RAND(),0,0.00013); Distance = NORMINV(RAND(),0,0.002).

[0035] The formula for calculating the standard deviation distribution of simulated measured data is:

[0036] Where m is the sample standard deviation. The deviation between the traverse points of each through-face and the simulated value is given. for The sum of n, where n is the total number of samples; The judgment criteria are as follows: if the positional deviation of most simulation results (recommended ≥90%) is ≤ twice the mean error in mm, and the sample standard deviation is close to the mean error value of the network type, then the observation scheme meets the requirements for continuity accuracy; otherwise, the measurement accuracy level needs to be adjusted or the network type needs to be optimized.

[0037] S3: Based on the GNSS control points selected in S1, the tunnel external GNSS control network is laid out and measured. This is done using a dual-frequency GNSS receiver, equipped with a forced centering base, tripod, antenna height measuring ruler, etc., through static observation, with instrument leveling and centering completed before observation. Data processing is then performed, and the tunnel external connection error is predicted. Rigorous adjustment is used for data processing, including unconstrained and constrained adjustments. Unconstrained adjustment is used to verify the internal consistency of the network shape and eliminate baselines with excessive closure errors. Constrained adjustment uses known high-level control points as a benchmark to determine the coordinates of the external GNSS control points, constructing a new traverse control network. All relevant technical indicators and selected measuring equipment adhere to conventional traverse surveying technical standards.

[0038] When measuring traverse stations inside the tunnel, only one tripod, one base, three single prisms, and two prism inserts are needed for both forward and backward sightings. The work for both forward and backward sightings consists only of inserting two forced-centering prisms and setting up one tripod for prism centering and leveling. Portable insertion prisms are used on the sidewalls. These portable insertion prisms use forced centering, eliminating the need for leveling operations. They offer high repeatability, high accuracy, and speed, greatly improving orientation accuracy while reducing weight. Compared to the traditional method where each group required five tripods, four prism sets, and five to six people, this method only requires three people to complete the traverse measurement work. This allows for the addition of a work group to accelerate the measurement progress and significantly increase measurement efficiency.

[0039] By setting up tripods and prism sets, the load can be reduced. Originally, each group required 5 tripods and 4 prism sets, and each group required 5-6 people to work. Now, only 3 people are needed to complete the traverse measurement work. An additional working group can be added to speed up the control of the measurement progress and increase the measurement efficiency many times over.

[0040] S4: The work of laying out the control points of the traverse in the tunnel is carried out by using the determined traverse point layout plan. The timing for installing control points inside the tunnel is as follows: control points for the bottom slab should be installed after the bottom slab concrete has been poured and reached the design strength; control points for the side walls should be installed after the secondary lining concrete has been poured, the formwork has been removed, and the secondary lining concrete has reached the required strength. The control points of the base plate are drilled by impact drill. After cleaning the debris in the holes, epoxy resin mortar is injected, and a locating pin with forced centering is inserted. The top of the locating pin is flush with the surface of the base plate, and the surrounding area is sealed with sealant to prevent moisture.

[0041] The side wall insertion forced centering control point adopts a customized insertion embedded part. The fixing sleeve is pre-embedded before the secondary lining concrete is poured. The centering rod is installed after the concrete is formed. The deviation between the centering rod center and the design point is ≤±1mm.

[0042] S5: Conduct traverse surveying and distance correction within the tunnel. Based on the predetermined accuracy level of the tunnel control survey, carry out traverse surveying within the tunnel and complete the field distance measurement and side measurement work. Then, perform distance correction, adjustment and accuracy evaluation, and use the traverse survey results to guide the tunnel excavation.

[0043] Field distance measurement employs the repetition method to observe horizontal angles, simultaneously observing the traverse points on the same side of the base plate and the control points on both side walls. In indoor data processing, meteorological and projection corrections are applied first, followed by projection corrections. Adjustment calculations are performed using traverse network adjustment software, including plane coordinate adjustment and elevation adjustment for closed or attached traverses. The principle of meteorological correction is that electromagnetic wave distance measurement is affected by atmospheric temperature (t), air pressure (P), and humidity (e), and the actual wave velocity differs from the standard meteorological conditions used in the instrument's design. During operation, the average temperature and air pressure during observation are substituted to calculate the meteorological correction for each side. The corrected slope distance is:

[0044] Where K is the meteorological correction factor, and the meteorological correction factor is provided by different instrument manufacturers; The principle of tilt correction is to convert the tilt distance D' after meteorological correction through a vertical angle. Alternatively, the elevation difference h can be converted into the horizontal distance L between the measuring station and the mirror station, using the following formula: ; The principle of projection transformation is to reduce the horizontal distance L on the ground to the Gaussian projection reference surface defined by the construction coordinate system. Tunnel construction usually uses an independent coordinate system or a 3° Gaussian projection. However, there is a height difference between the ellipsoid (or geoid) where the ground horizontal distance is located and the projection surface, which will cause length deformation. The formula is as follows:

[0045] in, The difference (m) between the average elevation of the two endpoints of the ranging edge and the elevation of the projected surface; R is the average radius of curvature of the reference ellipsoid in the direction of the ranging edge (usually taken as 6371 km or a local precise value); during operation, the horizontal distance L is added to the projection correction. This yields the final Gaussian plane distance S used for adjustment; (When Hm is positive, the distance becomes longer).

[0046] The adjustment calculation employs indirect or conditional adjustment methods. Traverse network adjustment software (such as Cosa, SYADJ, and Southern Adjustment Easy) is used to calculate the most probable coordinates (X, Y) and their positional errors for each traverse point (base point and sidewall point). Simultaneously, the unit weight error is obtained to verify the rationality of the prior weights. If the verified unit weight error differs significantly from the prior value, the weights need to be recalculated and the adjustment repeated until the results converge.

[0047] Accuracy assessment is achieved through accuracy indicators and analysis. The accuracy indicators are the verified values ​​of the positional error of the weakest point, the relative error of the side length, and the angular measurement error. It is required that the plane positional error of the weakest point meets the calculation requirements (for the through surface), and the relative closure error of the entire traverse meets the specification requirements (e.g., 1 / 100000).

[0048] Stability analysis involves comparing the coordinate changes of the current adjustment results with those of the previous measurement (or the initial measurement). Special attention is paid to the coordinate changes of the forced centering point on the sidewall. If the change exceeds twice the point's positional error, it indicates that the point may have shifted due to surrounding rock deformation. This point should be removed or downweighted in subsequent tunneling measurements, and the stable floor point or the far sidewall point should be used as the benchmark.

[0049] The traditional traverse control network is transformed into the new control network in this embodiment. The number of observation targets at each station is the same, with two forced centering control points on the front and back walls plus one base plate control point on the same side. The double forced centering points on the side walls are adopted.

[0050] When measuring each station of the traverse inside the tunnel, only one tripod, one base, three single prisms, and two prism inserts are needed for the foresight and backsight. The work of foresight and backsight only involves inserting two forced centering prisms and setting up one tripod prism for centering and leveling. All the work of foresight and backsight can be completed quickly by one person.

[0051] For tunnels where fourth-order elevation control can meet the requirements for tunnel breakthrough, this measurement method is adopted. The elevation control measurement is carried out using the mid-sight method without measuring the height of the station, with the double-sided wall prisms as the survey lines, and a closed triangular elevation line with two entries and two exits.

[0052] Example 2: Based on Example 1, this example uses an 8km long double-track railway tunnel being excavated from opposite directions to illustrate the application of this method in detail. Step S1: Design the control network outside the tunnel, which runs north-south. The tunnel is 8km long. Select the measurement accuracy level. Select second-order GNSS for external measurement and second-order traverse for internal measurement. Select GPS points JKDW1, JKDW2, JKDW3, CKDW1, CKDW2, and CKDW3 at the tunnel entrance. Among them, JKDW1 and JKDW2 are the entrance directional edges with an angle of 5° to the normal of the penetration surface, and CKDW1 and CKDW2 are the exit directional edges with an angle of 3° to the normal of the penetration surface.

[0053] The positional error projection of points JKDW1 and CKDW1 on the through surface is 10mm. The length from the inlet / outlet to the through surface is 4000m. The angular error of the two directional sides is 1.3″.

[0054] The theoretical error in tunnel penetration was calculated as follows:

[0055] The distance outside the tunnel is 0.014m < 0.045m, which meets the requirements.

[0056] Step S2: Design the control network pattern for the conductors inside the tunnel.

[0057] First, based on the tunnel length, the traverse control network level is selected as Class II, and the average side length of the traverse is determined to be 400m. Then, control points are arranged inside the tunnel, with one group of points every 400m, including two on the sidewalls and two on the floor. The traverse survey network diagram on the tunnel entrance side is then determined as follows. Figure 2 As shown; Then, the side lengths and angles are measured station by station to form the theoretical in2 file. The data in the file is shown below:

[0058] Then, this file is used to perform adjustment calculations for the traverse control network. The calculation results are shown in the following figure:

[0059] The weakest point is the penetration point JK22. Based on E / F / T, the lateral penetration error is calculated as follows:

[0060] The requirements were met, proving that the method is theoretically feasible.

[0061] The mean square error of the overall connection between the inside and outside of the tunnel = =4.35cm < 8.0cm, the plan is feasible.

[0062] Then, establish random functions for angle and distance observations. In Excel, use the following formulas: Angle variable simulation = NORMINV(RAND(),0,0.00013, Distance variable simulation = IF(ISBLANK(C8),"",NORMINV(RAND(),0,0.002)). Here, the conversion formula DD.MMSS+DD.MMSS is needed to obtain the observation values ​​with random numbers added. The formula for the random function is shown below: =LET(total_sec,SIGN(X)*(INT(ABS(X))*3600+INT((ABS(X)-INT(ABS(X)))*100)*60+MOD((ABS(X)-INT(ABS(X)))*100,60)),abs_sec, ABS(total_sec),deg, INT(abs_sec / 3600), min_part,MOD(abs_sec,3600), min, INT(min_part / 60), sec, MOD(min_part,60), sign_result, SIGN(X), ROUND(sign_result*(deg+min / 100+sec / 10000),6)).

[0063] Where X is the original angle ddmmss observation, and the output is the ddmmss observation with random numbers added.

[0064] The measurement results under simulated error conditions are compared with theoretical values ​​to form a batch of simulated results. The data and standard deviation are compared with the theoretical data to determine whether they meet the requirements for consistency.

[0065] Ten simulations were performed, and data from traditional quadrilateral and hexagonal geodetic control networks were also simulated. The distribution of the data is shown in the table below:

[0066] Based on the data simulation distribution results and standard deviation, it can be concluded that the accuracy of the new control network and the traditional hexagonal control network is consistent, and the results can be used in practical applications, ensuring the smooth completion of the tunnel.

[0067] S3: Conduct GNSS control network layout and measurement outside the tunnel. Based on the control network points outside the tunnel determined in the first step, carry out point burial layout and field observation. After the field observation is completed, carry out indoor data processing and complete the prediction of tunnel breakthrough error after verification.

[0068] S4: Install control points for the traverse inside the tunnel. Based on the layout plan of the traverse points determined by the technical design, install the points when the tunnel construction reaches the design mileage.

[0069] S5: Conduct traverse surveying and distance correction within the tunnel. Based on the predetermined accuracy level of the tunnel control survey, carry out traverse surveying within the tunnel and complete the field distance measurement and side measurement work. Then, perform distance correction, adjustment and accuracy evaluation, and use the traverse survey results to guide the tunnel excavation.

[0070] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A lightweight traverse surveying method for underground tunnels, characterized in that, A novel tunnel control network was established using a new method for simulating tunnel breakthrough errors. Control points were laid out on the bottom slab and the secondary lining sidewalls. The bottom slab points were established using centering points, and the sidewall points were established using insertion-type forced centering control points. Traverse measurements were performed on the same side of the bottom slab control points and the control points on both sides of the sidewalls. The traverse measurement method includes the following specific steps: S1: Based on the tunnel length and the visibility at the tunnel entrance, determine the network type of the external control network and estimate the connection error of the external control network; S2: Establish a simulation model of the control network, calculate the tunnel breakthrough error inside the tunnel, and combine it with the breakthrough error outside the tunnel to obtain the comprehensive breakthrough error inside and outside the tunnel. Establish random functions for angle observation and distance observation, simulate the measurement results under the error environment of actual measurement, and form a batch of simulation results by comparing with theoretical values ​​and determine whether they meet the breakthrough requirements. S3: Conduct GNSS control network layout and measurement outside the tunnel, perform data processing, and complete the prediction of tunnel breakthrough error after verification; S4: The work of laying out the control points of the traverse in the tunnel is carried out by using the determined traverse point layout plan. S5: Conduct traverse surveys and distance corrections within the tunnel, perform adjustment and accuracy assessments, and then use the traverse survey results to guide the tunnel excavation.

2. The lightweight traverse surveying method for underground tunnels according to claim 1, characterized in that, The proposed network type of the tunnel external control network in step S1 is as follows: Based on the tunnel length, select the measurement accuracy level; based on the visibility at the tunnel entrance, select GNSS control points outside the tunnel, determine the type of control network outside the tunnel, and predict the connection error of the control network outside the tunnel. The mean square error of the lateral breakthrough outside the tunnel is calculated using formulas for angle measurement and distance measurement. The mean square error of the lateral breakthrough before the control survey is: ; In the formula, These are the projected lengths of the coordinate errors of the inlet and outlet GNSS control points on the through surface, respectively. These are the lengths from the inlet and outlet GNSS control points to the breakthrough point, respectively. These are the azimuth mean square errors of the GNSS connection line at the inlet and outlet, respectively. These are the angles between the line connecting the entrance and exit control points to the connection point and the normal line of the connection point; After verification following GNSS measurements, the mean square error for lateral penetration is: ; In the formula, , , Let x and y represent the variance and covariance of the difference between the x and y coordinates calculated from the inlet and outlet to the connection point, respectively. Indicates the azimuth angle of the through surface.

3. The lightweight traverse surveying method for underground tunnels according to claim 1, characterized in that, The simulation model establishment method in step S2 is to simulate the tunnel control network, draw the diagram in the mapping software, measure angles and distances to establish the model table, calculate the error ellipse of the weakest point in the tunnel based on the model, compare it with the theoretical value, form a batch of simulation results, and determine whether the simulation data and data standard deviation meet the requirements for tunnel breakthrough.

4. The lightweight traverse surveying method for underground tunnels according to claim 1, characterized in that, The formula for predicting the lateral penetration error of the calculation model in step S2 is as follows: ; ; In the formula, E represents the mean square error of the lateral connection; E represents the major semi-axis of the ellipse representing the calculation error of the traverse point model; F represents the minor semi-axis of the ellipse representing the calculation error of the traverse point model. The tangent azimuth of the tunnel breakthrough face is the coordinate azimuth of the tunnel axis; T is the azimuth corresponding to the major axis E of the error ellipse.

5. The lightweight traverse surveying method for underground tunnels according to claim 1, characterized in that, In step S2, the random function for simulating the error in the measured data is implemented with a mean of 0 and a standard deviation of the mean error of the measurement accuracy class. In Excel, taking a tunnel with a second-order angle of 1.3″ and a distance of 2mm as an example, the implementation method is as follows: Angle = NORMINV(RAND(),0,0.00013); Distance = NORMINV(RAND(),0,0.002).

6. The lightweight traverse surveying method for underground tunnels according to claim 1, characterized in that, The formula for calculating the standard deviation distribution of the simulated measured data in step S2 is as follows: ; Where m is the sample standard deviation. The deviation between the traverse points of each through-face and the simulated value is given. for The sum of n, where n is the total number of samples.

7. The lightweight traverse surveying method for underground tunnels according to claim 3, characterized in that, The error ellipse calculation steps for the weakest point inside the hole in step S2 are as follows: The error ellipse parameters of the weakest point inside the tunnel are calculated using the variance-covariance matrix of the traverse network. The weakest point inside the tunnel is usually near the tunnel breakthrough face. The parameters include the major semi-axis, minor semi-axis, and azimuth. The requirement is that the mean square error of the plane position of the weakest point and the mean square error of the tunnel breakthrough limit after comprehensive calculation outside the tunnel meet the requirement, ensuring that the breakthrough error is within the allowable range.

8. The lightweight traverse surveying method for underground tunnels according to claim 1, characterized in that, In step S3, the layout and measurement of the GNSS control network outside the tunnel are carried out using a dual-frequency GNSS receiver, through static observation, and the instrument leveling and centering are completed before the observation. The traverse network layout adopts the method of double forced centering points on the side walls. When measuring the traverse at each station inside the tunnel, one tripod, one base, three single prisms, and two prism inserts are required for the foresight and backsight. The work of foresight and backsight includes inserting two forced centering prisms and setting up one tripod for prism centering and leveling. All the work of foresight and backsight is completed by one person.

9. The lightweight traverse surveying method for underground tunnels according to claim 1, characterized in that, In step S4, the timing for burying the control points inside the tunnel is as follows: the bottom slab control points should be buried after the bottom slab concrete has been poured and reached the design strength, and the side wall control points should be buried after the secondary lining concrete has been poured, the formwork has been removed, and the secondary lining concrete has reached the required strength. The control points on the base plate are drilled using an impact drill. After cleaning the debris from the holes, epoxy resin mortar is injected, and a locating pin with a forced centering is inserted. The top of the locating pin is flush with the surface of the base plate, and the surrounding area is sealed with sealant to prevent moisture. The side wall insertion forced centering control point adopts a customized insertion embedded part. The fixing sleeve is pre-embedded before the secondary lining concrete is poured. The centering rod is installed after the concrete is formed. The deviation between the centering rod center and the design point is ≤±1mm.

10. The lightweight traverse surveying method for underground tunnels according to claim 1, characterized in that, In step S5, according to the predetermined tunnel control measurement accuracy level, the tunnel traverse measurement is carried out to complete the field distance measurement and side measurement work; then the distance is corrected by two-dimensional adjustment, and the adjustment and accuracy evaluation are performed. In the field, the horizontal angle was measured by the repetition method, and the control points of the bottom plate on the same side and the control points of the side walls on both sides were observed simultaneously. In the data processing, the distance was corrected for meteorological and projection corrections. First, meteorological corrections were performed, and then projection corrections were performed. Adjustment calculations were performed using traverse network adjustment software to perform plane coordinate adjustment and elevation adjustment of closed traverses or attached traverses. Based on the adjustment results, the tunnel breakthrough error should be recalculated. If the error exceeds the expected range, the cause should be analyzed, and measures including but not limited to supplementary measurement, remeasurement, or densification of control points should be taken.

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