Method and device for testing upward arch deformation during excavation and unloading of soft rock cutting

Abstract

The invention provides a soft rock cutting excavation unloading upward arch deformation test method and device, and relates to the technical field of railway construction, and the method comprises the steps: arranging an optical fiber in a pore channel formed by pre-drilling; optical fiber dependent variables in the soft rock cutting excavation and unloading process are collected; on the basis of the optical fiber dependent variable corresponding to the optical fiber arranged on the bending section and a preset temperature correction coefficient, calculating the upward arch deformation of the bending section; calculating the upward arch deformation of the vertical section based on the optical fiber dependent variable and the temperature correction coefficient corresponding to the optical fiber arranged on the vertical section; and obtaining the total arch deformation amount. According to the method, the optical fibers are arranged in the pre-drilled hole, the strain capacity of the optical fibers is collected and analyzed in real time, the upwarp deformation of different sections is calculated on the basis of considering temperature correction, and the total deformation is obtained, so that accurate monitoring of the upwarp deformation in the soft rock cutting excavation process is achieved, the real-time performance and the accuracy of data are improved, and the working efficiency is improved. And a reliable basis is provided for safety assessment of geotechnical engineering.

Description

Technical Field

[0001] The present invention relates to the technical field of railway construction, and more particularly, to a method and device for testing the arching deformation caused by excavation and unloading of soft rock cuttings. Background Art

[0002] In recent years, the arching phenomenon in soft rock cutting sections has been a severe challenge for the deformation control of high-speed railway subgrades. The base arching phenomenon has occurred in the tunnel sections and deep cutting sections of many existing high-speed railway lines. The arching deformation will significantly reduce the vertical smoothness of the line and even endanger the safety of high-speed train operation, requiring timely and effective treatment.

[0003] The main reasons for the arching are the rebound arching caused by the excavation and unloading of deep cuttings under high in-situ stress conditions, and the swelling of soft rocks caused by the infiltration of rainwater or the change of the groundwater level after excavation. Among them, the rebound arching caused by excavation and unloading is not easy to accurately measure because the excavation of the cutting will affect or even damage the pre-installed testing device. The existing testing methods mainly include precise measurement with an electronic level and testing with a borehole layered magnetic ring. The former is greatly affected by the weather, and at the same time, the excavation will damage the observation points. In addition, how to continuously measure data during the excavation process is a difficult problem; the testing accuracy of the latter is greatly reduced because it is difficult to accurately fix the position of the magnetic ring in the borehole. Therefore, it is urgent to develop an accurate testing device and method for the excavation and unloading of soft rock cuttings that are not interfered by the excavation construction. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and device for testing the arching deformation caused by excavation and unloading of soft rock cuttings to improve the above problems. To achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0005] In a first aspect, the present application provides a method for testing the arching deformation caused by excavation and unloading of soft rock cuttings, including:

[0006] Placing an optical fiber in a hole formed by pre-drilling, the hole consisting of a horizontal section, a bending section, and a vertical section;

[0007] Collecting the strain of the optical fiber during the excavation and unloading of the soft rock cutting through a modulation and demodulation instrument connected to the optical fiber, the strain of the optical fiber including the length change amount and the temperature change amount;

[0008] Calculating the arching deformation of the bending section based on the strain of the optical fiber corresponding to the optical fiber disposed in the bending section and a preset temperature correction coefficient to obtain a first deformation amount;

[0009] Calculating the arching deformation of the vertical section based on the strain of the optical fiber corresponding to the optical fiber disposed in the vertical section and the temperature correction coefficient to obtain a second deformation amount;

[0010] Calculate the sum of the first deformation amount and the second deformation amount to obtain the total upward arch deformation amount.

[0011] In a second aspect, the present application also provides a test device for the upward arch deformation of the excavation and unloading of a soft rock cutting, including:

[0012] An optical fiber, disposed in a pre-drilled hole and tightly connected to the hole, for real-time sensing of the strain generated during the excavation and unloading of the soft rock cutting;

[0013] A dedicated modulation and demodulation instrument, connected to the optical fiber, for collecting the optical fiber strain data during the excavation and unloading of the soft rock cutting;

[0014] A data processing unit, connected to the dedicated modulation and demodulation instrument, for processing the collected optical fiber strain data and calculating the total upward arch deformation amount of the soft rock cutting.

[0015] The beneficial effects of the present invention are as follows:

[0016] By arranging an optical fiber in a pre-drilled hole, collecting and analyzing the optical fiber strain in real time, calculating the upward arch deformation of different sections and obtaining the total deformation amount on the basis of considering temperature correction, the present invention can realize the precise monitoring of the upward arch deformation during the excavation process of the soft rock cutting, improve the real-time performance and accuracy of the data, and provide a reliable basis for the safety assessment of geotechnical engineering.

[0017] Other features and advantages of the present invention will be described in the subsequent specification, and part of them will become obvious from the specification or be understood by implementing the embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 It is a schematic flow chart of the test method for the upward arch deformation of the excavation and unloading of the soft rock cutting described in the embodiments of the present invention;

[0020] Figure 2 It is a schematic structural diagram of the test device for the upward arch deformation of the excavation and unloading of the soft rock cutting described in the embodiments of the present invention.

[0021] Reference numerals in the figures: 1, hole; 2, optical fiber; 3, temperature sensing device. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. Components of the embodiments of the present invention generally described and illustrated in the drawings herein can be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] It should be noted that like reference numerals and letters denote like items in the following drawings. Therefore, once an item is defined in one drawing, it does not require further definition and explanation in subsequent drawings. Meanwhile, in the description of the present invention, terms such as "first" and "second" are only used for descriptive distinction and cannot be construed as indicating or implying relative importance.

[0024] Embodiment 1:

[0025] This embodiment provides a test method for the arching deformation caused by excavation and unloading of soft rock cuttings.

[0026] Refer to Figure 1 , which shows that this method includes steps S10, S20, S30, S40 and step S50:

[0027] Step S10. The optical fiber is arranged in a hole formed by pre-drilling. The hole consists of a horizontal section, a bent section and a vertical section;

[0028] Specifically, as Figure 2 shown, it can be seen that the optical fiber from left to right is successively a horizontal section, a bent section and a vertical section. Among them, the position corresponding to the vertical section is the position to be measured.

[0029] Specifically, step S10 specifically includes steps S11 to S13:

[0030] Step S11. Use a drill with a bendable drill bit to drill a hole along a preset path to form a hole;

[0031] Specifically, in this application, a drill with a turning ability is used to drill a hole according to a preset path to form a hole. Among them, the depth of the vertical section of the hole is not less than 10 meters, and the vertical section generally should enter the slightly weathered rock layer. Once the hole is formed during the drilling process, the hole should be cleaned in time to remove the loose soil and crushed stones in the hole.

[0032] Step S12. After the hole is formed, the optical fiber and the grouting pipe are synchronously placed;

[0033] Specifically, after the pore formation, the optical fiber and the grouting pipe are inserted synchronously. Before being inserted into the pore, the optical fiber should be straightened. The optical fiber is used for real-time deformation monitoring, while the grouting pipe is used for subsequent fixing operations to ensure that the optical fiber is stably and reliably embedded in the pore. In this application, armored optical fibers are used for testing. The outside of the armored optical fiber is coated with metal or high-strength materials, making it have stronger compressive and tensile abilities under complex geological conditions and not easily breaking or being damaged due to the influence of rock mass movement or external forces during construction.

[0034] Step S13. Inject the cement mortar through the grouting pipe under pressure to tightly connect the optical fiber with the pore;

[0035] Specifically, inject the cement mortar through the grouting pipe and apply pressure to tightly combine the optical fiber with the pore. This process can enhance the contact stability between the optical fiber and the rock mass, improve the accuracy of data collection, and prevent the optical fiber from affecting the measurement results due to loosening or displacement during long-term monitoring. The cement mortar should be injected under pressure after the armored optical fiber and the grouting pipe are inserted, and the grade of the cement mortar should not be lower than M25.

[0036] Step S20. Through the modulation and demodulation instrument connected to the optical fiber, collect the optical fiber strain during the excavation and unloading process of the soft rock cut. The optical fiber strain includes the length change amount and the temperature change amount;

[0037] Specifically, considering that during the excavation of the soft rock cut, stress release and deformation will occur, and the optical fiber arranged in the pore will elongate or contract with the deformation of the rock mass. Through optical fiber sensing technology, the length change of the optical fiber can be accurately measured by the modulation and demodulation instrument, so as to calculate the deformation of the rock mass. On the other hand, considering that temperature changes may affect the measurement results of the optical fiber, it is necessary to synchronously record the temperature information for compensation or correction in subsequent data processing. For example, Figure 2 in, the black squares in the bending section and the vertical section are temperature sensing devices, which can be thermometers or thermistors, and there is no special limitation here.

[0038] Step S30. Based on the optical fiber strain corresponding to the optical fiber arranged in the bending section and the preset temperature correction coefficient, calculate the upward arch deformation of the bending section to obtain the first deformation amount;

[0039] Specifically, step S30 specifically includes steps S31 to S36:

[0040] Step S31. Before the excavation and unloading of the soft rock cut, evenly divide the optical fiber arranged in the bending section into multiple segments to obtain multiple segments of bending optical fibers with target lengths;

[0041] Specifically, before the excavation and unloading of the soft rock cutting, the optical fibers laid in the bending section are divided into multiple sections of bending optical fibers with a target length, which is convenient for refined measurement and calculation. The number of bending optical fibers can be divided according to the required accuracy of the calculation results. The more the number of divided sections, the greater the calculation amount and the more accurate the result.

[0042] Step S32. After the excavation and unloading of the soft rock cutting, obtain the angle between each section of the bending optical fiber and the horizontal direction as the bending optical fiber angle.

[0043] Step S33. Take the temperature change amount corresponding to the temperature sensing device closest to the center position of each section of the bending optical fiber as the temperature change amount of the bending optical fiber.

[0044] Specifically, obtain the temperature change amount of the temperature sensing device closest to the center position of each section of the bending optical fiber as the corresponding temperature for temperature compensation to reduce the influence of temperature on the calculation of the strain.

[0045] Step S34. Determine the bending optical fiber length change amount of each section of the bending optical fiber based on the length change amount.

[0046] Specifically, according to the length change amount of the optical fiber, calculate the length change amount of each section of the bending optical fiber, which provides a basis for the final deformation calculation.

[0047] Step S35. Calculate the deformation amount of each section of the bending optical fiber based on the bending optical fiber length change amount, bending optical fiber angle, bending optical fiber temperature change amount, and temperature correction coefficient.

[0048] Specifically, step S35 specifically includes steps S351 to S353:

[0049] Step S351. Calculate the product of the temperature correction coefficient, the temperature change amount of the bending optical fiber, and the target length to obtain the first product.

[0050] Step S352. Calculate the sum of the first product and the bending optical fiber length change amount to obtain the summation result.

[0051] Step S353. Calculate the product of the sine function value of the bending optical fiber angle and the summation result to obtain the deformation amount of the bending optical fiber.

[0052] Specifically, the deformation amount of each section of the bending optical fiber is:

[0053] s 1i =(△l 1i +α*△t1i*l 1i )*sinθ i

[0054] Where, s 1i is the deformation amount of the i-th section of the bending optical fiber; △l 1iis the length change of the i-th section of the bent optical fiber; l 1i is the target length of the i-th section of the bent optical fiber; α is the temperature correction coefficient; △t 1i is the temperature change of the i-th section of the bent optical fiber; θ i is the angle of the i-th section of the bent optical fiber; i ∈ n, where n is the number of bent optical fibers.

[0055] Step S36. Calculate the sum of the deformations of all bent optical fibers to obtain the first deformation;

[0056] Specifically, the sum of the deformations of all bent optical fibers in the bent section is calculated as:

[0057]

[0058] where S1 is the first deformation; S 1i is the deformation of the i-th section of the bent optical fiber; i ∈ n, where n is the number of bent optical fibers.

[0059] Through multi-segment division measurement + temperature compensation + bending angle correction, the deformation calculation is made more accurate and the error is reduced. Temperature changes will affect the strain of the optical fiber, and this method is corrected through the temperature correction coefficient to improve the measurement reliability.

[0060] Step S40. Based on the optical fiber strain and the temperature correction coefficient corresponding to the optical fiber arranged in the vertical section, calculate the upward arch deformation of the vertical section to obtain the second deformation;

[0061] Specifically, step S40 specifically includes steps S41 to S45:

[0062] Step S41. Before the excavation and unloading of the soft rock cutting, obtain the overall length of the optical fiber arranged in the vertical section as the vertical optical fiber length;

[0063] Step S42. After the excavation and unloading of the soft rock cutting, obtain the average value of all temperature changes corresponding to the optical fiber arranged in the vertical section as the vertical optical fiber temperature change;

[0064] Specifically, after the excavation and unloading, obtain the average value of all temperature changes corresponding to the optical fiber arranged in the vertical section as the vertical optical fiber temperature change for subsequent temperature compensation calculation.

[0065] Step S43. Determine the vertical length change of the optical fiber arranged in the vertical section based on the length change;

[0066] Step S44. Calculate the product of the temperature correction coefficient, the vertical optical fiber temperature change, and the overall length to obtain the second product;

[0067] Step S45. Calculate the sum of the second product and the vertical length change to obtain the second deformation;

[0068] Specifically, the deformation of the vertical-section optical fiber is:

[0069] S2 = △l2 + α * △t2 * l2

[0070] Wherein, S2 is the second deformation; △l2 is the length change of the vertical-section optical fiber; α is the temperature correction coefficient; △t2 is the temperature change of the vertical-section optical fiber; l2 is the length of the vertical-section optical fiber.

[0071] By obtaining the overall length of the vertical optical fiber and combining the temperature correction and length change data, the deformation in the vertical direction can be accurately evaluated. And by using the temperature correction coefficient and the average value of the temperature change for compensation, the measurement stability is improved to ensure accurate calculation of the deformation.

[0072] Step S50. Calculate the sum of the first deformation and the second deformation to obtain the total upward arch deformation;

[0073] Specifically, to calculate the total upward arch deformation, add the deformation of the bending section (the first deformation) and the deformation of the vertical section (the second deformation) to obtain the total upward arch deformation generated during the excavation and unloading process of the soft rock cut. Through the integration of the deformation data of the bending section and the vertical section, the upward arch deformation of the overall rock mass can be accurately characterized, providing a reliable basis for engineering safety assessment. Thus, the deformation of each part during the excavation process of the soft rock cut can be accurately measured, providing data support for risk control, support optimization, and safety maintenance during the construction process, and improving the engineering stability.

[0074] Embodiment 2:

[0075] As Figure 2 shown, this embodiment provides a test device for the upward arch deformation during the excavation and unloading of a soft rock cut, including:

[0076] An optical fiber 2, disposed in a hole 1 formed by pre-drilling and tightly connected to the hole 1, for real-time sensing of the strain generated during the excavation and unloading process of the soft rock cut;

[0077] A special modulation and demodulation decoder, connected to the optical fiber 2, for collecting the strain data of the optical fiber 2 during the excavation and unloading process of the soft rock cut;

[0078] A data processing unit, connected to the special modulation and demodulation instrument, for processing the collected strain data of the optical fiber 2 and calculating the total upward arch deformation of the soft rock cut

[0079] Specifically, by laying the optical fiber 2 in the pre-drilled hole 1 and ensuring its tight connection with the hole 1, the real-time perception of the strain during the excavation and unloading process of the soft rock cutting is realized. The dedicated modulation and demodulation instrument is responsible for collecting the strain data of the optical fiber 2 and transmitting it to the data processing unit, which analyzes and processes the data to calculate the total upward arch deformation of the soft rock cutting, so as to provide accurate deformation monitoring results.

[0080] The hole 1 is formed by a drill that can turn during drilling. The hole 1 is successively a horizontal section, a bending section, and a vertical section along the drilling process.

[0081] The grouting pipe is synchronously placed into the hole 1 with the optical fiber 2. The grouting pipe is used to inject cement mortar to tightly consolidate the optical fiber 2 with the hole 1. After the optical fiber 2 and the grouting pipe are placed, the cement mortar is grouted, and the grade of the cement mortar is not lower than M25 to provide sufficient bonding strength and durability, thereby improving the long-term monitoring reliability of the optical fiber 2.

[0082] Circular protrusions and temperature sensing devices 3 are evenly spaced along the length direction on the outer side of the optical fiber 2. The optical fiber 2 used in this application has circular protrusions with a diameter of not less than 2 mm on its outer surface, and the spacing of the protrusions is 5 mm, which is used to strengthen the connection between the cement slurry and the armor and ensure their coordinated deformation; at the same time, along the length direction of the optical fiber 2, a thermometer (or thermistor) is set every 5 m to measure the temperature change of the optical fiber 2.

[0083] The bending radius of the optical fiber 2 in the hole 1 is not less than 25 times the diameter of the optical fiber 2. To ensure the stability and signal transmission quality of the optical fiber 2 in the hole 1, the bending radius of the optical fiber 2 is not less than 25 times its diameter. This design can effectively reduce the signal loss of the optical fiber 2 at the bending point and avoid structural damage or strain measurement errors caused by excessive bending. At the same time, this bending radius requirement also helps to improve the reliability of the optical fiber 2 in long-term monitoring and ensure that it can accurately reflect the deformation situation during the excavation and unloading process of the soft rock cutting.

[0084] It should be noted that regarding the devices in the above embodiments, the specific ways in which each module performs operations have been described in detail in the embodiments related to the method, and will not be elaborated here.

[0085] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0086] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A test method for the upward arching deformation of the excavation and unloading of soft rock cuttings, characterized in that, Including: Placing an optical fiber in a pre-drilled hole, the hole consisting of a horizontal section, a bent section, and a vertical section; Collecting the optical fiber strain during the excavation and unloading process of the soft rock cutting through a modulation and demodulation instrument connected to the optical fiber, the optical fiber strain including the length change and the temperature change; Calculating the upward arch deformation of the bent section based on the optical fiber strain corresponding to the optical fiber in the bent section and a preset temperature correction coefficient to obtain a first deformation amount; Calculating the upward arch deformation of the vertical section based on the optical fiber strain corresponding to the optical fiber in the vertical section and the temperature correction coefficient to obtain a second deformation amount; Calculating the sum of the first deformation amount and the second deformation amount to obtain the total upward arch deformation.

2. The test method for the arching deformation caused by excavation and unloading of soft rock cuttings according to claim 1, characterized in that , Placing an optical fiber in a pre-drilled hole includes: Using a drill that can turn during drilling to drill a hole along a preset path; After the hole is formed, synchronously inserting the optical fiber and the grouting pipe; Pressurizing and grouting cement mortar through the grouting pipe to tightly connect the optical fiber and the hole.

3. The test method for the arching deformation of the soft rock cutting excavation and unloading according to claim 1, wherein , Calculating the upward arch deformation of the bent section based on the optical fiber strain corresponding to the optical fiber in the bent section and a preset temperature correction coefficient to obtain a first deformation amount, including: Before the excavation and unloading of the soft rock cutting, evenly dividing the optical fiber in the bent section into multiple segments to obtain multiple bent optical fibers with target lengths; After the excavation and unloading of the soft rock cutting, obtaining the angle between each bent optical fiber and the horizontal direction as the bent optical fiber angle; Taking the temperature change amount corresponding to the temperature sensing device closest to the center position of each bent optical fiber as the temperature change amount of the bent optical fiber; Determining the length change amount of each bent optical fiber based on the length change amount; Calculating the deformation amount of each bent optical fiber based on the length change amount of the bent optical fiber, the bent optical fiber angle, the temperature change amount of the bent optical fiber, and the temperature correction coefficient; Calculating the sum of the deformation amounts of all bent optical fibers to obtain the first deformation amount.

4. The test method for the upward arching deformation caused by excavation and unloading of soft rock cuttings according to claim 3, characterized in that , Calculating the deformation amount of each bent optical fiber based on the length change amount of the bent optical fiber, the bent optical fiber angle, the temperature change amount of the bent optical fiber, and the temperature correction coefficient, including: Calculating the product of the temperature correction coefficient, the temperature change amount of the bent optical fiber, and the target length to obtain a first product; Calculating the sum of the first product and the length change amount of the bent optical fiber to obtain a summation result; Calculating the product of the sine function value of the bent optical fiber angle and the summation result to obtain the deformation amount of the bent optical fiber.

5. The test method for the upward arching deformation caused by excavation and unloading of soft rock cuttings according to claim 1, characterized in that , Calculating the upward arch deformation of the vertical section based on the optical fiber strain corresponding to the optical fiber in the vertical section and the temperature correction coefficient to obtain a second deformation amount, including: Before the excavation and unloading of the soft rock cutting, obtaining the overall length of the optical fiber in the vertical section as the vertical optical fiber length; After the excavation and unloading of the soft rock cutting, obtaining the average value of all the temperature change amounts corresponding to the optical fiber in the vertical section as the temperature change amount of the vertical optical fiber; Determining the vertical length change amount of the optical fiber in the vertical section based on the length change amount; Calculating the product of the temperature correction coefficient, the temperature change amount of the vertical optical fiber, and the overall length to obtain a second product; Calculate the sum of the second product and the vertical length change amount to obtain the second deformation amount.

6. A test device for the arching deformation caused by excavation and unloading of soft rock cuttings, characterized in that, Including: An optical fiber is disposed in a pre-drilled hole and is tightly connected to the hole for real-time sensing of the strain generated during the excavation and unloading of the soft rock cut. A dedicated modulation and demodulation instrument is connected to the optical fiber to collect the optical fiber strain data during the excavation and unloading of the soft rock cut. A data processing unit is connected to the dedicated modulation and demodulation instrument for calculating the total upward arch deformation of the soft rock cut based on the collected optical fiber strain data.

7. The test device for the up-arching deformation caused by excavation and unloading of soft rock cuttings according to claim 6, wherein The hole is formed by a drill with a bendable drill bit. The hole is successively a horizontal section, a bent section, and a vertical section along the drilling process.

8. The test device for the upward arching deformation caused by excavation and unloading of soft rock cuttings according to claim 6, characterized in that, Including a grouting pipe, the grouting pipe is synchronously placed into the hole with the optical fiber, and the grouting pipe is used to inject cement mortar to tightly consolidate the optical fiber and the hole.

9. The test device for the upward arching deformation caused by excavation and unloading of soft rock cuttings according to claim 6, characterized in that, Circular protrusions and temperature sensing devices are uniformly spaced along the length direction on the outer side of the optical fiber.

10. The test device for the arching deformation caused by excavation and unloading of soft rock cuttings according to claim 7, wherein, The bending radius of the optical fiber in the hole is not less than 25 times the diameter of the optical fiber.

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