Soft rock gully section tunnel deformation monitoring method

Abstract

The invention provides a soft rock gully section tunnel deformation monitoring method, which belongs to the field of tunnel construction deformation monitoring, and comprises the following steps: selecting a typical monitoring section of an ultra-shallow buried large section tunnel, and arranging a plurality of groups of measuring points on an arch crown, an arch shoulder, a haunch, an arch foot and an arch bottom; a high-precision total station is adopted to collect vault settlement and cavern periphery convergence data in real time, and meanwhile, the monitoring frequency is dynamically adjusted based on the displacement rate; measuring the pressure change of the surrounding rock through the intelligent string-type double-membrane soil pressure box; the stability of the surrounding rock is judged, obtained data are analyzed and processed, and the vault settlement deformation cumulant, the settlement growth rate and the pressure distribution characteristics of the surrounding rock are obtained; calculating and predicting the final settlement amount and the peripheral convergence value of the vault through a fitting formula; and drawing a surrounding rock deformation envelope line through the surrounding convergence change values, and carrying out confluence analysis on surrounding rock pressure change to obtain a surrounding rock pressure envelope line, so as to reveal the form evolution and pressure distribution rule of the surrounding rock cavity of the tunnel. According to the method, the engineering safety and efficiency are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of tunnel construction deformation monitoring, and in particular to a method for monitoring deformation of a soft rock gully section tunnel. Background Art

[0002] In the construction of soft rock tunnels in gully sections, the core challenges faced are ultra-shallow burial and poor surrounding rock stability. Due to the shallow burial depth of the tunnel, the load distribution of the overlying rock and soil is uneven, and the mechanical properties of the soft rock are weak. After excavation, it is easily disturbed and undergoes plastic deformation, leading to arch settlement and accelerated convergence rate of the surrounding area, and even causing disasters such as collapse and surface subsidence. Traditional single arch settlement monitoring fails to fully capture the coupling effect of surrounding rock pressure and convergence deformation, exposing the one-sidedness of the monitoring system. In addition, the special topography of the gully valley bottom leads to complex groundwater seepage paths, and the softening of the surrounding rock under water-rich conditions further exacerbates the deformation risk. Existing research lacks quantitative analysis of the deformation laws of the valley bottom surrounding rock, and construction still relies on engineering analogy methods and lacks targeted monitoring plans.

[0003] Current tunnel deformation monitoring technologies, which primarily rely on manual measurements, have significant limitations. Traditional methods focus solely on single parameters, such as vault settlement or perimeter convergence, while neglecting the coordinated monitoring of key stress indicators such as surrounding rock pressure. This makes it difficult to comprehensively assess the stress state of the support structure. To meet the multi-dimensional monitoring needs of soft rock tunnels in gully sections, a coordinated monitoring system encompassing settlement, convergence, and pressure is urgently needed to enable data-driven deformation analysis and safety early warning.

[0004] Therefore, there is an urgent need in this field for a deformation monitoring method for soft rock gully sections of tunnels that can significantly improve engineering safety and efficiency.

[0005] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the Invention

[0006] To address the above-mentioned issues, the present invention provides a method for monitoring deformation in soft rock gully tunnels. This method significantly improves engineering safety and efficiency through multi-parameter collaborative monitoring and data-driven analysis. The method specifically includes the following steps:

[0007] Select a typical monitoring section of an ultra-shallow large-section tunnel and set up multiple groups of measuring points at the arch crown, spandrel, waist, foot and bottom of the arch;

[0008] A high-precision total station is used to collect real-time data on vault settlement and cavity perimeter convergence, while the monitoring frequency is dynamically adjusted based on the displacement rate.

[0009] The surrounding rock pressure changes are measured using an intelligent string-type double-membrane earth pressure cell;

[0010] Determine the stability of the surrounding rock and analyze the obtained data to obtain the cumulative amount of arch settlement deformation, settlement growth rate and surrounding rock pressure distribution characteristics;

[0011] The final settlement of the vault and the surrounding convergence value are predicted by calculating the fitting formula;

[0012] By plotting the surrounding convergence change values ​​into the surrounding rock deformation envelope, the surrounding rock pressure changes are integrated and analyzed to obtain the surrounding rock pressure envelope, revealing the evolution of the tunnel surrounding rock cavity morphology and pressure distribution law.

[0013] Optionally, the ultra-shallow buried large-section tunnel refers to a tunnel with a buried depth less than 1 times the tunnel span and an excavated cross-sectional area of ​​not less than 80 m2; the typical monitoring section includes a vault settlement monitoring point and a horizontal convergence monitoring point.

[0014] Optionally, the high-precision total station is a Topcon ES-101 model, and the intelligent string-type double-membrane earth pressure cell is a JMZX-5006AM model; the measuring point arrangement includes three points A, B, and C on the arch top, four points D, E, F, and G on the arch waist, and three points H~1, H~2, and H on the arch bottom.

[0015] Optionally, the measuring points are arranged at the axis of the tunnel arch and at 5 meters on both sides of the axis, respectively, a arch settlement measuring point (points A, B, and C), 2 to 4 pairs of peripheral convergence measuring points (points D, E, F, and G, forming two measuring lines DE and FG) are arranged on the same section, and 10 surrounding rock pressure measuring points (A to H2) are arranged at five locations, namely the arch crown, arch shoulder, arch waist, arch foot, and arch bottom.

[0016] Optionally, a high-precision total station can be used to collect real-time data on vault settlement and perimeter convergence, while dynamically adjusting the monitoring frequency based on the displacement rate. For vault settlement measurements, reflective sheets are attached to the measuring points. After tunnel excavation and initial support, embedded components with hooks are buried as test piles.

[0017] Optionally, the specific steps for real-time acquisition of vault subsidence using a high-precision total station and reflective sheets include:

[0018] Check whether the embedded measuring points are damaged or loose, and remove dust;

[0019] Select an appropriate location to set up the measuring station so that the instrument can observe all measuring points;

[0020] (3) Level the instrument and enter the opposite measurement mode;

[0021] (4) Measure after calibrating the backsight point;

[0022] (5) Aim at the vault sinking measurement point to be observed and perform three round trip tests for each measurement to improve accuracy. The difference between each test result should not exceed 0.5mm. Record the average value of the three measurements as the measurement result of the vault sinking;

[0023] (6) Record the observation location, time, data and the number of each measuring point;

[0024] (7) After completing the measurement, the instrument should be promptly arranged in preparation for the next measurement.

[0025] Optionally, the face-to-face measurement mode includes the following steps:

[0026] Measuring points are arranged symmetrically on opposite sides of the tunnel monitoring section. For example, reflective sheet measuring points (A, B, and C) are arranged on the arch axis and 5 meters on both sides, and auxiliary backsight points (D and D') are arranged at symmetrical positions on the left and right sides of the tunnel wall.

[0027] Start the total station and enter the "opposite measurement mode". Aim at the opposite backsight control point (such as spandrel measuring point B) and enter the 3D coordinates. Then rotate the instrument to aim at the auxiliary backsight point on the other side (such as point D'). Use rear intersection to solve the measuring station coordinates and establish the measurement coordinate system.

[0028] The arch measuring points (A, B, and C) are measured three times back and forth, and the Z-axis coordinate difference is calculated as the arch settlement. If the difference in a single measurement exceeds 0.5mm, re-measurement is performed. When the cumulative settlement exceeds 20mm or the daily settlement rate is ≥5mm, an early warning is triggered.

[0029] Optionally, before pre-buried test piles, use a drill to drill holes at the test location, then place the test piles into the holes and fix them with fast-setting cement or early-strength anchoring agents. At the same time, a protective cover is set on the top of the test piles to protect them from damage. For poor rock mass, anchors are arranged after anchor spraying support is carried out.

[0030] Optionally, the perimeter convergence monitoring is performed on the same monitoring section. Two to four pairs of measuring points are arranged on the monitoring section, with four measuring points selected: D, E, F, and G. The method for burying the measuring piles is the same as for measuring vault subsidence, the monitoring frequency standard is the same as for vault subsidence monitoring, and the total station is used in the same manner as for vault subsidence measurement.

[0031] Optionally, when burying the tunnel soil pressure cells, first determine the location and number of the pressure cells, and dig a suitable size pit to place them. Then adjust the pressure cells to ensure the correct horizontal and vertical positions, then fill and fix the surrounding gaps, and finally check and confirm to ensure that they are firmly installed, accurately positioned and free of damage.

[0032] Optionally, in the vault settlement measurement frequency standard, the vault settlement displacement velocity is used as a reference indicator, and the measurement frequency is dynamically adjusted according to real-time changes. The monitoring frequency standard is shown in Table 1:

[0033] Table 1 Monitoring frequency standard table

[0034]

[0035] The frequency standard of the cavity perimeter convergence measurement is the same as that of the arch subsidence measurement, and the surrounding rock pressure measurement frequency is once a day, with a specification of 0.4 MPa.

[0036] Alternatively, the surrounding rock stability judgment standard is based on the Technical Specifications for Highway Tunnel Construction (JTG F60-2009), and the allowable displacement value for shallow tunnels with Class V surrounding rock is 0.2-0.8mm.

[0037] Optionally, the dual-index judgment criteria of the measured displacement value and displacement rate are:

[0038] (1) When U < Un / 3, it indicates that the surrounding rock is stable and excavation can proceed normally;

[0039] (2) When Un / 3<U<2Un / 3, it means that the surrounding rock deformation is slightly larger, and attention should be paid to the surrounding rock changes;

[0040] (3) When 2Un / 3<U, it means that the surrounding rock deformation is very large, and the construction excavation should be stopped immediately and special reinforcement measures should be taken;

[0041] (4) When U≤2Un / 3, it indicates that the surrounding rock and initial support have reached a stable state;

[0042] The judgment standard of surrounding rock stability rate change is:

[0043] When the displacement rate exceeds 1 mm / d, it means that the surrounding rock is in a rapid deformation stage and the dynamic changes of the surrounding rock need to be monitored at all times;

[0044] When the displacement rate is between 1 and 0.2 mm / d, it indicates that the surrounding rock has converged to the slow deformation stage;

[0045] When the displacement rate is less than 0.2 mm / d, it indicates that the surrounding rock is stable;

[0046] Among them, Un is the maximum allowable displacement value, and U represents the measured displacement value.

[0047] Optionally, the analysis and processing of the obtained data includes drawing a vault settlement deformation accumulation diagram, a settlement growth rate diagram, a peripheral convergence data curve and a surrounding rock pressure monitoring curve.

[0048] Optionally, the fitting formula calculation is to perform nonlinear fitting on the vault settlement data and the surrounding convergence data, and the fitting formula is: Where x is the number of monitoring days, Y is the vault settlement, e is a natural constant, and a, b, and c are constants.

[0049] Optionally, the final settlement of the vault and the surrounding convergence value are predicted by fitting formulas and compared with the measured values ​​for verification.

[0050] Optionally, by plotting the surrounding convergence data into a surrounding rock deformation envelope, the change pattern of the cavity morphology over time after tunnel excavation is revealed; the surrounding rock pressure envelope shows the pressure change pattern.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] The present invention provides a deformation monitoring method for soft rock gully tunnels, comprising the following steps: selecting a typical monitoring section of an ultra-shallow, large-section tunnel and deploying multiple sets of measuring points at the vault, spandrel, haunch, foot, and base; using a high-precision total station to collect real-time data on vault settlement and perimeter convergence of the tunnel cavity, while dynamically adjusting the monitoring frequency based on the displacement rate; measuring surrounding rock pressure changes using an intelligent string-type double-membrane earth pressure cell; assessing surrounding rock stability and analyzing the resulting data to obtain cumulative vault settlement and deformation, settlement growth rate, and surrounding rock pressure distribution characteristics; predicting the final vault settlement and perimeter convergence values ​​using a fitting formula; and plotting perimeter convergence change values ​​as a surrounding rock deformation envelope. The surrounding rock pressure envelope is then integrated and analyzed to reveal the morphological evolution and pressure distribution patterns of the tunnel's surrounding rock cavity. Through multi-parameter collaborative monitoring and data-driven analysis, the present invention addresses the problems of delayed deformation prediction and proneness to collapse during construction of shallow soft rock tunnels in gully sections, significantly improving project safety and efficiency and providing a theoretical basis for similar projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0054] Figure 1 A schematic flow chart of a method for monitoring deformation of a soft rock tunnel provided by an embodiment of the present invention.

[0055] Figure 2 This is a schematic diagram of the arrangement of monitoring points in a monitoring section provided by an embodiment of the present invention.

[0056] Figure 3A schematic diagram of the earth pressure box burial site provided by an embodiment of the present invention.

[0057] Figure 4 This is a curve diagram of the cumulative amount of vault settlement deformation provided by an embodiment of the present invention.

[0058] Figure 5 This is a curve of the rate of change of the incremental deformation of the dome provided by an embodiment of the present invention.

[0059] Figure 6 A schematic diagram of a convergence data curve provided by an embodiment of the present invention.

[0060] Figure 7 A schematic diagram of a surrounding rock pressure monitoring curve provided by an embodiment of the present invention.

[0061] Figure 8 Schematic diagram of the surrounding rock deformation characteristic envelope provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0062] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0063] The purpose of the present invention is to provide a method that can significantly improve engineering safety and efficiency.

[0064] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0065] Example 1:

[0066] This embodiment provides a method for monitoring deformation of a soft rock gully tunnel. Figure 1 As shown, the following steps are included:

[0067] Select a typical monitoring section of an ultra-shallow large-section tunnel and set up multiple groups of measuring points at the arch crown, spandrel, waist, foot and bottom of the arch;

[0068] A high-precision total station is used to collect real-time data on vault settlement and cavity perimeter convergence, while the monitoring frequency is dynamically adjusted based on the displacement rate. Changes in surrounding rock pressure are measured using an intelligent string-type double-membrane earth pressure cell.

[0069] Determine the stability of the surrounding rock and analyze the obtained data to obtain the cumulative amount of arch settlement deformation, settlement growth rate and surrounding rock pressure distribution characteristics;

[0070] The final settlement of the vault and the surrounding convergence value are predicted by calculating the fitting formula;

[0071] By plotting the surrounding convergence change values ​​into the surrounding rock deformation envelope, the surrounding rock pressure changes are integrated and analyzed to obtain the surrounding rock pressure envelope, revealing the evolution of the tunnel surrounding rock cavity morphology and pressure distribution law.

[0072] The implementation target is the L2K48+594 section of the left line of Leirong Tunnel. This section is located at the bottom of the gully, with the shallowest burial depth (ultra-shallow burial), poor surrounding rock stability, belonging to Grade V surrounding rock, large excavation span, and prone to disasters such as collapse and surface subsidence.

[0073] The arch settlement measurement points are arranged at the tunnel arch axis (point A) and 5 meters on both sides of the axis (points B and C), for a total of 3 measurement points (such as Figure 2 (As shown). Affix reflective sheets to the measuring points. After excavation and initial support, use a small drill to drill holes and install embedded parts with hooks as measuring piles. Secure with quick-setting cement and install a protective cover on top. For poor rock mass, deploy anchors after anchor spraying.

[0074] The surrounding convergence measurement points are arranged at 4 measurement points (D, E, F, G) on the same monitoring section, forming two measurement lines DE and FG (e.g. Figure 2 The method of burying the measuring piles is consistent with the arch settlement, ensuring that they are located on the same section as the arch measurement point to facilitate collaborative data analysis.

[0075] The rock pressure measurement points are arranged at 10 points in 5 locations: arch crown (A), arch spandrel (B, C), arch waist (D, E), arch foot (F, G), and arch bottom (H1, H2, H). Figure 2 ), bury the intelligent string-type double-membrane soil pressure box (JMZX-5006AM, specification 0.4MPa). When burying, first dig the appropriate pit, adjust the horizontal / vertical position of the pressure box, fill and fix it, and check the firmness (such as Figure 3 shown).

[0076] The vault settlement and perimeter convergence data were collected using the Topcon ES-101 high-precision total station.

[0077] The arch settlement data is the settlement measurement of three points A, B and C at L2K48+594 on the excavation surface.

[0078] The statistical frequency of vault settlement data is once a day, and a total of 44 sets of data are counted.

[0079] The peripheral convergence data collection is to measure the horizontal displacement of four points D, E, F, and G. The displacement direction of the four points is stipulated to be positive away from the central axis, and the distance between two points on the same horizontal line is subtracted from the original distance to obtain the peripheral convergence value of the arch waist measuring lines DE and FG.

[0080] The measurement frequency of the peripheral convergence data is the same as that of the vault, and 44 sets of data are statistically analyzed.

[0081] JMZX-5006AM model earth pressure boxes were buried regularly in the L2K48+594 section for data extraction. One set of test data was extracted every two days, and 44 sets of data were statistically generated.

[0082] According to the Technical Specifications for Highway Tunnel Construction (JTG F60-2009), the maximum allowable displacement value Un for shallow tunnels with Class V surrounding rock is 0.2 to 0.8 mm, and is judged by using two indicators.

[0083] Through 44 sets of monitoring data, a cumulative vault settlement diagram was drawn (such as Figure 4 As shown in the figure), the sedimentation growth rate diagram (as shown in the figure), Figure 5 As shown), the surrounding convergence data curve (as shown Figure 6 As shown) and surrounding rock pressure monitoring curve (as shown Figure 7 shown).

[0084] Nonlinear fitting and prediction of the data of the arch settlement (point A) and the surrounding convergence (DE and FG lines)

[0085] Descending quantity, e is a natural constant, a, b, c are constants.

[0086] The fitting formula obtained by fitting the data of point A of the arch is: The final settlement is predicted to be 10.65 mm by fitting the formula, which is highly consistent with the measured value of 10.49 mm. By performing nonlinear fitting on the cumulative convergence data of DE and FG, the fitting formula is obtained as follows: By performing limit evaluation on the formula, the cumulative convergence values ​​of DE are 12.86 mm and FG are 9.95 mm, which are basically the same as the cumulative convergence values ​​of 12.7 mm and 9.6 mm obtained by measurement.

[0087] Draw the surrounding rock deformation envelope (such as Figure 8 (as shown in the figure), which shows that after tunnel excavation, the shape of the cavity gradually changes from the initial circle to an "oblate" shape (the arch crown sinks and the arch waist expands outward); the surrounding rock pressure envelope is "egg-shaped", with the arch crown having the largest pressure, the arch bottom second, and the arch waist and arch foot being smaller, revealing the law that stress concentrates at the top and bottom.

[0088] Engineering application and effects:

[0089] During monitoring of section L2K48+594, the first seven days after excavation saw a period of rapid deformation. Settlement at point A on the vault accounted for 47.5% of the total, while the surrounding convergence line DE accounted for 42.5%. During this period, monitoring was intensified (once per day) to promptly detect abnormal deformation and strengthen initial support. After the 20th day, the displacement rate was <0.2 mm / day, and secondary lining was applied. Subsequent deformation stabilized, validating the monitoring method's guiding role in construction safety.

[0090] This method achieves precise deformation monitoring and prediction of ultra-shallow soft rock tunnels through the coordinated monitoring of multiple parameters (settlement, convergence, and pressure) and data-driven analysis, addressing the challenges of delayed deformation and uncontrolled collapse risks associated with traditional methods. The standardized monitoring process and quantified judgment indicators provide a replicable technical solution for similar projects, significantly improving the safety and efficiency of tunnel construction.

[0091] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0092] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A method for monitoring deformation of a soft rock gully tunnel, characterized in that: The following steps are involved: Select a typical monitoring section of an ultra-shallow large-section tunnel and set up multiple groups of measuring points at the arch crown, spandrel, waist, foot and bottom of the arch; A high-precision total station is used to collect real-time data on vault settlement and cavity perimeter convergence, while the monitoring frequency is dynamically adjusted based on the displacement rate. The surrounding rock pressure changes are measured using an intelligent string-type double-membrane earth pressure cell; Determine the stability of the surrounding rock and analyze the obtained data to obtain the cumulative amount of arch settlement deformation, settlement growth rate and surrounding rock pressure distribution characteristics; The final settlement of the vault and the surrounding convergence value are predicted by calculating the fitting formula; By plotting the surrounding convergence change values ​​into the surrounding rock deformation envelope, the surrounding rock pressure changes are integrated and analyzed to obtain the surrounding rock pressure envelope, revealing the evolution of the tunnel surrounding rock cavity morphology and pressure distribution law.

2. The method for monitoring deformation of a soft rock gully tunnel according to claim 1, characterized in that: The high-precision total station is a Topcon ES-101 model, and the intelligent string-type double-membrane earth pressure cell is a JMZX-5006AM model; the measuring point arrangement includes three points on the arch top, A, B, and C; four points on the arch waist, D, E, F, and G; and three points on the arch bottom, H~1, H~2, and H.

3. The method for monitoring deformation of a soft rock gully tunnel according to claim 1, characterized in that: A high-precision total station was used to measure the vault subsidence, and a measuring point was arranged at the axis of the tunnel vault and 5 meters on both sides of the axis, for a total of three measuring points. These measuring points were distributed at locations A, B, and C. Reflective sheets were affixed to the measuring points to facilitate measurement, and the size of the measuring points was appropriately adjusted. After tunnel excavation and initial support were completed, embedded parts were arranged as measuring piles.

4. The method for monitoring deformation of a soft rock gully tunnel according to claim 1, characterized in that: The specific steps for real-time acquisition of vault subsidence using a high-precision total station and reflectors include: Check whether the embedded measuring points are damaged or loose, and remove dust; Select an appropriate location to set up the measuring station so that the instrument can observe all measuring points; Level the instrument and enter the opposite measurement mode; Measurements are taken after calibrating the backsight point; Aim at the vault sinking measurement point to be observed and perform three round trip tests for each measurement. The difference between the test results should not exceed 0.5mm. The average value of the three measurements is recorded as the measurement result of the vault sinking. Record the observation location, time, data and the number of each measuring point; After completing the measurement, organize the instrument in time to prepare for the next measurement.

5. The method for monitoring deformation of a soft rock gully tunnel according to claim 3, characterized in that: Before pre-embedding the test pile, use a drilling rig to drill a hole at the test location, then place the test pile into the hole and fix it with fast-setting cement or early-strength anchoring agent; at the same time, set a protective cover on the top of the test pile to protect it from damage; for poor rock mass, arrange anchors after anchor spraying support.

6. The method for monitoring deformation of a soft rock gully tunnel according to claim 1, characterized in that: The peripheral convergence monitoring is arranged in the same monitoring section, with 2 to 4 pairs of measuring points arranged in the monitoring section. Four measuring points, D, E, F, and G, are selected. The method of burying measuring piles is the same as that of arch sinking measuring piles. The monitoring frequency standard is the same as that of arch sinking monitoring frequency standard. The method of using the total station is the same as that of arch sinking measurement.

7. The method for monitoring deformation of a soft rock gully tunnel according to claim 6, characterized in that: When burying tunnel soil pressure cells, first determine the location and number of the pressure cells, and dig a pit of appropriate size to place them. Then adjust the pressure cells to ensure the correct horizontal and vertical positions, then fill and fix the surrounding gaps. Finally, check and confirm to ensure that the installation is firm, the position is accurate and there is no damage.

8. The method for monitoring deformation of a soft rock gully tunnel according to claim 1, characterized in that: In the frequency standard for vault settlement measurement, the displacement velocity of vault settlement is used as a reference indicator, and the measurement frequency is dynamically adjusted according to real-time changes.

9. The method for monitoring deformation of a soft rock gully tunnel according to claim 1, characterized in that: The judgment criteria of the measured displacement value and displacement rate are: (1) When U < Un / 3, it indicates that the surrounding rock is stable and excavation can proceed normally; (2) When Un / 3<U<2Un / 3, it means that the surrounding rock deformation is slightly larger, and attention should be paid to the surrounding rock changes; (3) When 2Un / 3<U, it means that the surrounding rock deformation is very large, and the construction excavation should be stopped immediately and special reinforcement measures should be taken; (4) When U≤2Un / 3, it indicates that the surrounding rock and initial support have reached a stable state; The judgment standard of surrounding rock stability rate change is: When the displacement rate exceeds 1 mm / d, it means that the surrounding rock is in a rapid deformation stage and the dynamic changes of the surrounding rock need to be monitored at all times; When the displacement rate is between 1 and 0.2 mm / d, it indicates that the surrounding rock has converged to the slow deformation stage; When the displacement rate is less than 0.2 mm / d, it indicates that the surrounding rock is stable; Among them, Un is the maximum allowable displacement value, and U represents the measured displacement value.

10. The method for monitoring deformation of a soft rock gully tunnel according to claim 1, characterized in that: The fitting formula calculation is to perform nonlinear fitting on the vault settlement data and the surrounding convergence data. The fitting formula is: Where x is the number of monitoring days, Y is the vault settlement, e is a natural constant, and a, b, and c are constants.

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