A method for monitoring deformation of underground space lining structure and deep rock-soil body

Abstract

The present application relates to the technical field of subway shield tunnel engineering monitoring, in particular to a method for monitoring deformation of underground space lining structure and deep rock-soil mass, which utilizes the existing grouting hole or hoisting hole of shield tunnel segment to lay radial distributed sensing optical fiber from the inside of the tunnel to the outside, and combines with longitudinal optical fiber on the tunnel inner wall to form a dendritic combined monitoring network. The method can directly obtain key parameters such as horizontal displacement and layered settlement of deep rock-soil mass, fills in the monitoring blind area between lining and ground surface in the traditional method, and establishes a complete monitoring chain from deep soil deformation to lining structure response. The method directly utilizes the existing hole of the segment, does not need to drill new holes on the segment, sends the optical fiber into the external soil body through a half-open pipe, and then pulls out the steel pipe, so that the whole operation process does not damage the tunnel lining structure, ensures the integrity and waterproof performance of the segment, and is suitable for tunnels in operation and tunnels in construction period.

Description

Technical Field

[0001] This invention relates to the field of monitoring technology for subway shield tunnel engineering, specifically a method for monitoring the deformation of underground space lining structures and deep rock and soil. Background Technology

[0002] With the deepening of urbanization in my country, subway construction is characterized by networking, depth, and dense crossings. New lines intersect with existing operating lines, and tunnel depths generally exceed 20 meters. Current monitoring methods often prioritize surface areas over deeper layers and structure over soil, isolating the monitoring of the lining structure from the surrounding soil. Monitoring points are scattered, primarily monitoring lining convergence and settlement within the tunnel and surface settlement. Due to limitations in shield tunnel construction technology, the tunnel segments are jacked off the shield machine shell after assembly, making it difficult to install pressure cells, displacement gauges, and other sensors into the deep soil outside the lining after tunnel formation. Current technologies typically only allow for the deployment of a small number of shallow inclinometer holes or settlement markers from the surface downwards, limiting monitoring depth. Effective synchronous monitoring methods are lacking for key parameters such as horizontal displacement, vertical stratified settlement, and aquifer level changes caused by shield construction.

[0003] Therefore, a significant monitoring blind spot exists between the tunnel lining and the surface soil, making it impossible to predict the formation of potential major slip surfaces or plastic zones. When lining deformation occurs, it is difficult to determine whether it stems from its own quality issues or is driven by large-scale displacement of the external soil, complicating cause analysis and decision-making. Existing monitoring systems fail to establish a complete transmission chain from "construction disturbance source" to "deep soil deformation" and then to "surface structure response," lacking sufficient perception of the interaction mechanism between the lining and deep soil. Therefore, there is an urgent need for a method that can deploy monitoring devices from inside the tunnel to the external deep soil to achieve integrated real-time monitoring of the lining structure and the deep soil. Summary of the Invention

[0004] The technical problem this invention aims to solve is to overcome the shortcomings of existing methods and provide a method for monitoring the deformation of underground lining structures and deep soil and rock masses. This method utilizes existing grouting holes or hoisting holes in shield tunnel segments to deploy radially distributed sensing optical fibers from the inside of the tunnel outwards, combined with longitudinal optical fibers on the tunnel wall, forming a dendritic joint monitoring network. This method can directly acquire key parameters such as horizontal displacement and stratified settlement of deep soil and rock masses, filling the monitoring blind spot between the lining and the ground surface in traditional methods. It establishes a complete monitoring chain from deep soil deformation to the response of the lining structure, effectively solving the problems in the background technology.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for monitoring the deformation of underground space lining structures and deep soil and rock masses, comprising the following steps: S1. Using the existing grouting holes or hoisting holes on the shield tunnel segments, a semi-open thin steel pipe with an inner diameter of 20mm is used to send the distributed sensing optical fiber through the hole into the deep rock and soil outside the segment. Protective rubber tubes or cables can be installed on the outside of the sensing optical fiber. S2. Sensor optical fibers are laid in the deep rock and soil at the crown, 45° shoulders and waist of each monitoring section of the shield tunnel. The sensor optical fibers extend radially along the tunnel. S3. Pull out the half-open pipe, leaving the sensing optical fiber in the soil and rock mass, and inject ultrafine cement grout through the grouting hole with a grouting pressure of less than 0.1 MPa. S4. Longitudinal sensing optical fibers are laid out along the inner wall of the tunnel lining, and the radial sensing optical fibers in the hole are connected to the longitudinal sensing optical fibers. The sensing optical fibers are in a tree-like shape to form a deep rock and soil-lining joint monitoring network. S5. A distributed optical fiber sensing system is adopted, which is based on the Brillouin scattering principle to collect strain data in real time and convert it into soil deformation.

[0006] As a preferred embodiment of the present invention, the radial sensing optical fiber is laid out along the longitudinal direction of the tunnel at 1.5m per ring or 3.0m, 4.5m, 6.0m, 7.5m, and 9.0m intervals, with the laying density adjusted according to the geological risk level.

[0007] As a preferred technical solution of the present invention, the semi-open tube includes a semi-open tube A with an inner diameter of 20 mm and a wall thickness of 5 mm and a semi-open tube B. The semi-open tube A and the semi-open tube B surround the outside of the sensing optical fiber to form a complete steel tube, which can be inserted into the grouting hole or the hoisting hole and then pulled out and separated as a whole.

[0008] As a preferred embodiment of the present invention, the two end faces of the semi-open tube A are provided with grooves that are 2mm wide and 3mm high, and the two end faces of the semi-open tube B are provided with protrusions that are 2mm wide and 3mm high corresponding to the grooves. The semi-open tube A and the semi-open tube B are engaged with each other by the grooves and protrusions.

[0009] As a preferred embodiment of the present invention, at least one set of semi-circular studs is provided on the lower outer surface of both semi-open pipe A and semi-open pipe B. Each set includes two studs, which are symmetrically arranged near the two end faces of semi-open pipe A or semi-open pipe B. After semi-open pipe A and semi-open pipe B are joined to form a complete steel pipe, the corresponding two semi-circular studs are also joined to form a complete threaded joint. Bolts are threaded onto the outer side of the threaded joint, and the two studs are tightened and fixed by the bolts, thereby fixing the lower side of the semi-open pipe. This can prevent the sensing optical fiber from being opened during transportation or operation after semi-open pipe A and semi-open pipe B have surrounded and fixed it. Since the upper part needs to be completely inserted into the grouting hole or lifting hole, semi-circular studs are only provided on the lower outer surface of semi-open pipe A and semi-open pipe B, which can prevent them from getting stuck in the grouting hole or lifting hole and being difficult to remove. Before removing the half-open pipe A and half-open pipe B, the bolts can be removed first. The half-open pipe A and half-open pipe B can then be separated from each other. Either the half-open pipe can be completely removed, or the half-open pipe A and half-open pipe B can be removed one by one.

[0010] As a preferred technical solution of the present invention, the outer side of the radial sensing optical fiber is sleeved with a telescopic cavity ball valve. The telescopic cavity ball valve is composed of multiple hollow frustum-shaped sleeves connected coaxially. Adjacent frustum-shaped sleeves are connected to each other through a small bottom surface or a large bottom surface. That is, the connecting surface of adjacent frustum-shaped sleeves is the small bottom surface or the large bottom surface. The resulting telescopic cavity ball valve can be effectively sealed by shrinking into a semi-open pipe and expanding to accommodate ultrafine cement slurry.

[0011] As a preferred embodiment of the present invention, at least two telescopic cavity ball valves are provided, with at least one disposed on the inner surface of the lining and the other disposed on the outer surface of the lining.

[0012] As a preferred embodiment of the present invention, three telescopic cavity ball valves are provided, two of which are located on the inner surface of the lining and one on the outer surface of the lining. The telescopic cavity ball valve located on the inner surface of the lining and at the end of the sensing optical fiber is fixedly connected to the end folding ball valve. The end folding ball valve is a closed spherical structure. The telescopic cavity ball valves are connected to each other and to each other via rubber tubes.

[0013] As a preferred technical solution of the present invention, the monitoring method is implemented during the tunnel construction period or operation period, and can be deployed before the construction of the underpass project or during the operation period.

[0014] As a preferred technical solution of the present invention, for high-risk sections, circumferential sensing optical fibers are also deployed to form a gridded joint monitoring network with radial and longitudinal sensing optical fibers.

[0015] As a preferred embodiment of the present invention, the distributed optical fiber sensing system is based on Brillouin optical time-domain reflectometry, and the strain monitoring accuracy reaches ±0.5 mm settlement equivalent.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention utilizes existing grouting holes or hoisting holes in shield tunnel segments to deploy radially distributed sensing optical fibers from the inside of the tunnel outwards, combined with longitudinal optical fibers on the tunnel inner wall, forming a dendritic joint monitoring network. This allows for the direct acquisition of key parameters such as horizontal displacement and stratified settlement of deep soil and rock masses, filling the monitoring blind spot between the lining and the ground surface in traditional methods, and establishing a complete monitoring chain from deep soil deformation to the lining structure response.

[0017] 2. This invention directly utilizes the existing holes in the tunnel lining segments, eliminating the need to drill new holes in the segments. The optical fiber is inserted into the external soil through a semi-open pipe and then the steel pipe is pulled out. The entire operation process does not damage the tunnel lining structure, ensuring the integrity and waterproof performance of the segments. It is suitable for both operational tunnels and tunnels under construction.

[0018] 3. This invention allows for flexible adjustment of the monitoring section spacing (1.5m per ring or 3.0m, 4.5m, 6.0m, 7.5m, 9.0m every other ring) according to the geological risk level and the importance of the crossing project. It can be temporarily deployed during the construction period or permanently deployed during the operation period; it can be pre-deployed before the underpass project or supplemented during the operation period, without being restricted by pre-embedding.

[0019] 4. This invention sets a telescopic cavity ball valve and an end folding ball valve on the outer side of the radial optical fiber. Through the multi-stage ball valve structure (inner surface of the lining, outer surface and end) and low-pressure grouting (less than 0.1MPa), it can effectively seal the grout and tightly stop the water in the optical fiber channel, preventing groundwater from seeping into the tunnel along the optical fiber channel. At the same time, the telescopic nature of the ball valve can buffer the compression of the optical fiber by the soil deformation, protecting the optical fiber from being crushed.

[0020] 5. Based on the Brillouin scattering principle and Brillouin optical time-domain reflectometry, this invention employs a distributed optical fiber sensing system, which can continuously and distributedly monitor strain changes at various points along the optical fiber. The strain monitoring accuracy can reach ±0.5mm settlement equivalent, and it can realize remote automated data acquisition and early warning, greatly improving the real-time performance and reliability of monitoring.

[0021] 6. For high-risk sections (such as tunnel crossings and sections with poor geological conditions), circumferential optical fibers can be further deployed to form a gridded joint monitoring network with radial and longitudinal optical fibers, so as to achieve all-round perception of deep soil and lining deformation in multiple directions such as above the tunnel, above the tunnel, and in the horizontal direction of the arch waist. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a side view of the structure of the present invention; Figure 3 This is a schematic diagram of the structure of the semi-open pipe, telescopic cavity ball valve, end-folding ball valve, and measuring optical fiber of the present invention. Figure 4 This is a schematic diagram of the structure of the semi-open tube and the measuring optical fiber of the present invention; Figure 5 This is a schematic diagram of the semi-open tube structure of the present invention; Figure 6 This is a schematic diagram of the telescopic cavity ball valve and the measuring optical fiber of the present invention; Figure 7 This is a schematic diagram of the end-folding ball valve, the telescopic cavity ball valve, and the measuring optical fiber of the present invention. Figure 8 This is a schematic diagram of the structure of the present invention, which includes studs and bolts at the bottom of the semi-open pipe.

[0023] In the diagram: 1. Tunnel segment, 2. Sensor fiber, 3. Half-open pipe A, 4. Half-open pipe B, 5. Telescopic cavity ball valve, 6. End folding ball valve, 7. Stud, 8. Bolt. 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] Please see Figure 1-8 This invention provides a technical solution: a method for monitoring the deformation of underground space lining structures and deep rock and soil masses, comprising the following steps: S1. Using the existing grouting holes or hoisting holes on the shield tunnel segment 1, a 20mm inner diameter semi-open thin steel pipe is used to send the distributed sensing fiber 2 into the deep rock and soil outside the segment. Protective rubber tubes or cables can be installed on the outside of the sensing fiber 2. S2. Sensor fiber 2 is installed in the deep rock and soil at the crown, 45° shoulders and waist of each monitoring section of the shield tunnel. The sensor fiber 2 extends radially along the tunnel. S3. Pull out the half-open pipe, leaving the sensing fiber 2 in the soil and rock mass, and inject ultrafine cement grout through the grouting hole. The grouting pressure is less than 0.1 MPa. S4. Longitudinal sensing fiber 2 is laid out along the longitudinal direction on the inner wall of the tunnel lining, and the radial sensing fiber 2 in the hole is connected to the longitudinal sensing fiber 2. The sensing fiber 2 is dendritic in shape, forming a deep rock and soil-lining joint monitoring network. S5. A distributed optical fiber sensing system is adopted, which is based on the Brillouin scattering principle to collect strain data in real time and convert it into soil deformation.

[0026] Example 1, taking a standard section of a subway shield tunnel as an example, details the specific implementation process of the monitoring method of the present invention.

[0027] I. Preparatory Work First, the spacing of monitoring sections was determined based on the tunnel design data and geological survey report. In this embodiment, tunnel segment 1 has an outer diameter of 6.2m, an inner diameter of 5.5m, and a ring width of 1.5m. A general geological section was selected, and the monitoring sections were arranged in alternating rings, i.e., a longitudinal spacing of 3.0m. Radial monitoring holes were set at the arch crown, the two 45° arch shoulders, and the two arch waists (a total of 5 points) of each monitoring section, using the existing grouting holes (or hoisting holes) on segment 1 as monitoring channels.

[0028] Preparation of the semi-open tube: The semi-open tube consists of semi-open tube A3 and semi-open tube B4. Grooves are formed on both end faces of semi-open tube A3, and protrusions corresponding to the grooves are formed on both end faces of semi-open tube B4. Semi-open tubes A3 and B4 are interlocked by the grooves and protrusions, forming a complete steel tube around the outside of the sensing fiber 2. The inner diameter of this steel tube is slightly larger than the compressed outer diameter of the sensing fiber 2 and the subsequently installed telescopic cavity ball valve 5, and the outer diameter is smaller than the inner diameter of the grouting hole (the grouting hole diameter is usually 20-30mm). In this embodiment, the total length of the steel tube is determined according to the required monitoring depth. For example, if the designed radial depth at the arch is 3m, then the length of the steel tube is 3.2m.

[0029] The sensing fiber 2 is a single-mode tight-buffered distributed optical fiber, with an outer rubber protective tube. Telescopic cavity ball valves 5 are installed at predetermined positions on the sensing fiber 2. In this embodiment, three telescopic cavity ball valves 5 are provided, located as follows: the first stage is near the inner side of the tunnel (i.e., the section where the sensing fiber 2 is located on the inner surface of segment 1), the second stage is near the outer surface of segment 1, and the third stage is an end-folding ball valve 6. The telescopic cavity ball valve 5 is composed of multiple hollow frustum-shaped sleeves coaxially connected vertically. Adjacent frustum-shaped sleeves are interconnected through a small or large base surface, forming a telescopic corrugated tubular structure. The end-folding ball valve 6 is a closed spherical structure, fixedly connected to the outermost end. The ball valves at each stage and the ball valves and the end-folding ball valve 6 are connected by rubber tubes to ensure that grout can enter each stage of the ball valves sequentially during grouting. The telescopic cavity ball valve 5 is in a compressed state when not grouting and can be inserted into the semi-open pipe along with the sensing fiber 2; after grouting, it expands and seals the channel.

[0030] II. Deployment of radial sensing optical fibers Inside the tunnel, operators push the assembled semi-open pipe (containing the sensing fiber optic cable 2 and the compressed telescopic cavity ball valve 5) outward from the tunnel side, through the grouting holes on segment 1, into the deep rock and soil outside segment 1. During the pushing process, semi-open pipes A3 and B4 are kept firmly engaged to prevent premature separation. Pushing is stopped after reaching the predetermined depth (based on the end folding ball valve 6 reaching the designed position).

[0031] 3. Pull out the partially opened pipe and grout to stop the water ingress. After confirming that the sensing fiber optic cable 2 and the ball valve are in place, grasp the tail ends of the semi-open pipes A3 and B4 and pull them outwards radially along the tunnel. Since the semi-open pipes A3 and B4 are only engaged by a groove and protrusion, they can be easily separated during the pulling process and removed section by section from the grouting hole. After the semi-open pipes are completely pulled out, the sensing fiber optic cable 2, the telescopic cavity ball valve 5, and the end folding ball valve 6 remain in the rock and soil, and the channel left by the semi-open pipes can just accommodate the sensing fiber optic cable 2 and the compressed ball valve.

[0032] Subsequently, ultrafine cement grout is injected into the duct through the grouting hole, with the grouting pressure controlled at 0.08 MPa (less than 0.1 MPa). The grout first enters the first-stage telescopic cavity ball valve 5 located on the inner surface of the lining, causing it to expand and adhere tightly to the inner wall of segment 1; grouting continues, and the grout enters the second-stage telescopic cavity ball valve 5 located on the outer surface of the lining through the rubber tube, causing it to expand and adhere tightly to the interface between the outer surface of segment 1 and the surrounding rock; finally, the grout enters the end folding ball valve 6, causing it to expand and form an end spherical seal. After the three-stage ball valves expand in sequence, the entire grouting duct is densely filled, and the expansion of the ball valves effectively prevents groundwater from seeping into the tunnel interior along the sensing fiber optic cable 2.

[0033] IV. Laying and connecting longitudinal optical fibers A main longitudinal sensing fiber optic cable 2 is laid along the longitudinal direction (axial direction) of the tunnel lining. This longitudinal sensing fiber optic cable 2 is closely attached to the inner wall of the tunnel segment 1 and fixed to the arch, shoulder, and other locations using special clips. The inner ends (i.e., the ends remaining inside the tunnel) of each monitoring section and each radial sensing fiber optic cable 2 are connected to the longitudinal sensing fiber optic cable 2 via fusion splices or fiber optic connectors to form a tree-like joint monitoring network. Both ends of the longitudinal sensing fiber optic cable 2 are led to a data acquisition box inside the tunnel wall and connected to a distributed fiber optic demodulator (using a Brillouin optical time domain reflectometer, BOTDR).

[0034] V. Real-time monitoring and data acquisition The distributed fiber optic sensing system is activated, with the laser wavelength set to 1550nm and a sampling interval of 0.5m. The system emits optical pulses in real time and receives and analyzes Brillouin backscattered light. When minute deformations occur in the deep soil, the tightly coupled radial sensing fiber 2 experiences tensile or compressive strain, causing a change in the Brillouin frequency shift (approximately 0.05-0.1MHz frequency shift per 1με strain). The demodulator outputs strain values ​​at different locations using optical time-domain reflectometry (OTDR). Using a pre-calibrated geotechnical model (strain-settlement conversion factor), the strain is converted into the stratified settlement or horizontal displacement of the deep soil. Monitoring data is uploaded to a cloud monitoring platform via a wireless network for real-time early warning. In this embodiment, the distributed fiber optic sensing system, based on Brillouin ODR, achieves a strain monitoring accuracy of ±0.5mm settlement equivalent.

[0035] Implementation Results: This embodiment successfully achieved distributed deformation monitoring of the deep soil outside segment 1 from inside the tunnel without causing any damage to segment 1. The grouting and water-stopping effect was good, and there was no leakage inside the tunnel.

[0036] Example 2: Encrypted monitoring and gridded deployment.

[0037] For high-risk intersections where shield tunnels pass under existing operational lines, a more intensive monitoring scheme is adopted.

[0038] Deployment density: Monitoring sections are set up along the longitudinal direction of the tunnel at each ring (1.5m). Radial sensing optical fibers 2 are deployed at the crown, 45° shoulders on both sides, waist on both sides, and foot of each section. The deployment depth of the radial sensing optical fibers 2 is increased compared to Example 1: 4m deeper into the tunnel segment 1 at the crown and 3m deeper into the tunnel segment 1. At the same time, circumferential sensing optical fibers 2 are deployed in the circumferential direction of the tunnel. The circumferential sensing optical fibers 2 are laid circumferentially along the inner wall of the tunnel segment 1 and are interconnected with the longitudinal sensing optical fibers 2 and the radial sensing optical fibers 2 through connectors to form a gridded joint monitoring network.

[0039] Deployment timing: All sensing fiber optic cables were deployed one month before the underpass construction to obtain initial deformation baseline values. Continuous monitoring was conducted during construction and continued for one year during the operation period.

[0040] Data fusion and analysis: The radial displacement of deep soil monitored by radial sensing fiber optic 2, the longitudinal uneven settlement of the lining monitored by longitudinal sensing fiber optic 2, and the circumferential convergence deformation of the lining monitored by circumferential sensing fiber optic 2 are fused to construct a three-dimensional deformation field. The monitoring system is equipped with multi-level early warning thresholds (yellow warning, orange warning, and red warning). When any indicator exceeds the threshold, the system automatically sends an alarm message to the construction management platform.

[0041] Implementation Results: The grid-based monitoring network successfully revealed the three-dimensional displacement field evolution of the deep soil around the existing tunnel during the shield tunneling process, providing a basis for real-time adjustment of construction parameters (such as earth pressure balance pressure, grouting volume, etc.) and ensuring the safe implementation of the tunneling project.

[0042] Example 3: Supplementary monitoring and analysis of causes of changes during operation.

[0043] In a subway shield tunnel that has been in operation for five years, minor cracks and joint openings were found in some sections (approximately 50m in length) of segment 1. It is necessary to determine whether the cracks are caused by quality issues with segment 1 itself (such as concrete shrinkage or insufficient reinforcement) or by external soil displacement. Since the tunnel is already in operation and the surface above is a main urban road, drilling from the surface is not possible; furthermore, prolonged interruption of operation within the tunnel is not permitted.

[0044] Implementation Method: Utilizing the tunnel's nighttime shutdown window (approximately 3 hours per day), according to the method of this invention, radial sensing optical fibers 2 were inserted into the deep soil outside the tunnel lining segment 1 at the existing grouting holes in the cracked section via semi-open pipes (3 semi-open pipes A and 4 semi-open pipes B). Three monitoring sections were deployed, spaced 4.5m apart. Radial sensing optical fibers 2 were deployed at five points on each section: the arch crown, both sides of the arch shoulders, and the arch waist, with radial depths of 2.5m at the arch crown, 2.0m at the arch shoulders, and 1.8m at the arch waist. Simultaneously, longitudinal sensing optical fibers 2 were laid on the tunnel inner wall, connecting to the radial sensing optical fibers 2. The entire deployment process took only two tunnel windows (approximately 6 hours in total) and did not affect tunnel operation.

[0045] Grouting and water sealing were performed using a three-stage telescopic cavity ball valve 5 and an end-folding ball valve 6, with a grouting pressure of 0.06 MPa. Because the tunnel had been in operation for many years, the pressure was strictly controlled during grouting to prevent excessive grout pressure from adversely affecting the existing structure. After grouting was completed, an inspection was conducted to ensure there was no leakage around the grouting holes.

[0046] Monitoring results: After two weeks of continuous monitoring, continuous horizontal displacement of the deep soil towards the tunnel was observed, with a cumulative displacement of approximately 3.2 mm. The displacement rate was positively correlated with the crack opening. Simultaneously, longitudinal fiber optic sensing 2 detected uneven settlement in the lining (differential settlement of approximately 1.8 mm / 10 m). Based on this, it was determined that the cracks were primarily driven by external soil compression (possibly caused by nearby underground construction or changes in groundwater level), rather than a quality issue with segment 1 itself. This conclusion provided a basis for subsequent reinforcement plans: using surface grouting to reinforce the soil in conjunction with steel supports within the tunnel, instead of replacing the segments, saved on engineering costs.

[0047] Example 4: Comparison and Adjustment of Different Monitoring Densities. This example illustrates how to flexibly adjust the monitoring density according to the formation risk level.

[0048] In a section of water-rich soft soil with poor geological conditions, the tunnel traverses an alternating layer of silt and clay. Based on the risk assessment, the monitoring cross-sections are spaced at 1.5m intervals per ring. Radial sensing fiber optic cables 2 are laid out along the longitudinal direction of the tunnel at 1.5m intervals. The monitoring points for each cross-section include the arch crown, the two 45° arch shoulders, the two arch waists, and the two arch feet, for a total of 7 points.

[0049] For sections with favorable geological conditions and greater burial depth, a ring-like arrangement is used to reduce monitoring costs, with spacings of 3.0m, 4.5m, 6.0m, 7.5m, or 9.0m. The specific spacing is determined based on geotechnical calculations and historical experience: a larger spacing (e.g., 9.0m) is used when the expected deformation impact range is small; a smaller spacing (e.g., 3.0m) is used when crossing fault fracture zones or existing structures. The depth of the radial sensing fiber 2 is also adjusted accordingly: 3.5m for the crown of high-risk sections and 2.0m for general sections.

[0050] All radial sensing optical fibers 2 are equipped with telescopic cavity ball valves 5 on their outer sides. In water-rich soft soil sections, in addition to the three-stage ball valves, an intermediate-stage ball valve is added between the end-face folding ball valve 6 and the second-stage ball valve, for a total of four stages of ball valves, to enhance the reliability of water sealing. The grouting pressure is adjusted according to the formation permeability: 0.05 MPa for silty sand layers and 0.08 MPa for clay layers.

[0051] Monitoring results: In the densely distributed section, the dissipation process of excess pore water pressure in the deep soil caused by shield tunneling and the corresponding stratified settlement were successfully monitored, providing early warning of two potential ground collapse risks. In the sparsely distributed section, monitoring costs were effectively reduced while still capturing the main deformation trends. This embodiment demonstrates that the method of the present invention has a flexible and adjustable deployment density, which can adapt to different engineering needs.

[0052] Example 5 describes another configuration of the semi-open pipes (3 semi-open pipes A, 4 semi-open pipes B) and its key operating points.

[0053] In the aforementioned embodiment, the groove of the semi-open tube A3 is concave, and the protrusion of the semi-open tube B4 is convex. This embodiment employs a dovetail groove structure: dovetail-shaped grooves are formed on both end faces of the semi-open tube A3, and corresponding dovetail-shaped protrusions are provided on both end faces of the semi-open tube B4. The dovetail groove connection is more robust and less prone to accidental separation during pushing, but it can still be easily disengaged during pulling.

[0054] During operation, first place the sensing fiber 2 and the compressed telescopic cavity ball valve 5 into the groove of the semi-open pipe A3. Then, align the protrusion of the semi-open pipe B4 with the groove of the semi-open pipe A3 and push it axially to lock them together into a complete circular pipe. When pushing it into the grouting hole, maintain a uniform speed to avoid violent shaking that could cause premature separation. After reaching the predetermined depth, slightly retract the semi-open pipe about 1-2 cm to allow the friction between the pipe wall and the soil to help loosen the locked parts, and then pull it out evenly. Control the pulling speed at 0.1-0.2 m / s to prevent the sensing fiber 2 from being pulled out.

[0055] In this embodiment, because the dovetail groove structure has high connection strength, it is suitable for deep radial layout (such as arch depth exceeding 4m) or hard strata.

[0056] The specific connection methods mentioned in this application, such as fixed connections or settings, include but are not limited to conventional connection methods such as integral molding, welding, bolt connection, riveting, and adhesive bonding.

[0057] All parts not disclosed in this invention are prior art, and their specific structures, materials, and working principles will not be described in detail. 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 variations 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 method for monitoring deformation of underground space lining structures and deep rock and soil masses, characterized in that, Includes the following steps: S1. Using the existing grouting holes or hoisting holes on the shield tunnel segment (1), the distributed sensing optical fiber (2) is sent into the deep rock and soil outside the segment through the hole using a semi-open pipe. S2. Sensor fiber (2) is installed in the deep rock and soil at the crown, 45° shoulders and waist of each monitoring section of the shield tunnel. The sensor fiber (2) extends radially along the tunnel. S3. Pull out the half-open tube, leaving the sensing fiber (2) in the soil and rock mass, and inject ultrafine cement grout through the grouting hole. The grouting pressure is less than 0.1 MPa. S4. Longitudinal sensing optical fibers (2) are laid out along the longitudinal direction on the inner wall of the tunnel lining, and the radial sensing optical fibers (2) in the hole are connected to the longitudinal sensing optical fibers (2). The sensing optical fibers (2) are in a tree-like shape to form a deep rock and soil-lining joint monitoring network. S5. A distributed optical fiber sensing system is adopted, which is based on the Brillouin scattering principle to collect strain data in real time and convert it into soil deformation.

2. The method for monitoring deformation of underground space lining structures and deep rock and soil masses according to claim 1, characterized in that: The radial sensing fiber (2) is laid out along the longitudinal direction of the tunnel at 1.5m per ring or 3.0m, 4.5m, 6.0m, 7.5m, and 9.0m intervals, with the laying density adjusted according to the geological risk level.

3. The method for monitoring deformation of underground space lining structures and deep rock and soil masses according to claim 1, characterized in that: The semi-open tube includes semi-open tube A (3) and semi-open tube B (4). Semi-open tube A (3) and semi-open tube B (4) surround the outside of the sensing optical fiber (2) to form a complete steel pipe, which can be inserted into the grouting hole or the hoisting hole and then pulled out and separated as a whole.

4. The method for monitoring deformation of underground space lining structures and deep rock and soil masses according to claim 3, characterized in that: The two end faces of the semi-open tube A (3) are provided with grooves, and the two end faces of the semi-open tube B (4) are provided with protrusions corresponding to the grooves. The semi-open tube A (3) and the semi-open tube B (4) are engaged with each other through the grooves and protrusions.

5. The method for monitoring deformation of underground space lining structures and deep rock and soil masses according to claim 4, characterized in that: The lower outer surfaces of the semi-open pipe A (3) and the semi-open pipe B (4) are symmetrically provided with two semi-circular studs (7). After the semi-open pipe A (3) and the semi-open pipe B (4) are joined together to form a complete steel pipe, the corresponding two semi-circular studs (7) are also joined together to form a complete threaded joint. The threaded joint is connected to a bolt (8) on the outside.

6. The method for monitoring deformation of underground space lining structures and deep rock and soil masses according to claim 5, characterized in that: A telescopic hollow ball valve (5) is sleeved on the outside of the radial sensing fiber (2). The telescopic hollow ball valve (5) is composed of multiple hollow frustum-shaped sleeves connected coaxially on the top and bottom. Adjacent frustum-shaped sleeves are connected to each other through a small bottom surface or a large bottom surface.

7. The method for monitoring deformation of underground space lining structures and deep rock and soil masses according to claim 6, characterized in that: At least two telescopic cavity ball valves (5) are provided, with at least one provided on the inner surface of the lining and the other provided on the outer surface of the lining.

8. The method for monitoring deformation of underground space lining structures and deep rock and soil masses according to claim 1, characterized in that: There are three telescopic cavity ball valves (5), two of which are located on the inner surface of the lining and one on the outer surface of the lining. The telescopic cavity ball valve (5) located on the inner surface of the lining and at the end of the sensing optical fiber (2) is fixedly connected to the end folding ball valve (6). The end folding ball valve (6) is a closed spherical structure.

9. A method for monitoring deformation of underground space lining structures and deep rock and soil masses according to any one of claims 1-8, characterized in that: The monitoring method is implemented during the tunnel construction or operation period and can be deployed before the construction of the underpass project or during its operation.

10. The method for monitoring deformation of underground space lining structures and deep rock and soil as described in claim 1, characterized in that: For high-risk sections, circumferential sensing optical fibers (2) are also deployed to form a gridded joint monitoring network with radial sensing optical fibers (2) and longitudinal sensing optical fibers (2).

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