Intelligent monitoring and dynamic early warning system for complex geological long tunnel

Abstract

This invention belongs to the field of tunnel safety monitoring technology, specifically disclosing a smart monitoring and dynamic early warning system for complex geological long tunnels. By simultaneously monitoring the displacement of deep surrounding rock and the displacement of shallow support, calculating the transmission ratio of their increments, and combining this with the identification of axial strain gradient reversal sections, the system can determine the separation of the surrounding rock and support interface. It can capture the precursors of the imbalance in the mechanical relationship of the surrounding rock and support before the support structure shows obvious damage, effectively extending the early warning time window. At the same time, based on the judgment of the separation of the surrounding rock and support interface, it further distinguishes between reversible poor contact and irreversible interface separation by monitoring the delay time from the deep displacement step to the shallow response and combining it with vibration events. This makes the judgment of the separation state more accurate and reliable. The graded early warning output can provide differentiated decision-making basis for on-site construction, preventing overreaction that causes work stoppage losses and avoiding safety accidents caused by delayed early warning.

Description

Technical Field

[0001] This invention belongs to the field of tunnel safety monitoring technology, and specifically discloses a smart monitoring and dynamic early warning system for complex geological long tunnels. Background Technology

[0002] Tunnels, as an integral part of modern transportation infrastructure, play an irreplaceable role in traversing terrains such as high mountains and deep valleys. To shorten route mileage, reduce damage to the surface ecology, and improve traffic operation efficiency, the construction of extra-long tunnels is increasing. These tunnels have great burial depth and complex ground stress, which makes the geological environment faced by engineering construction increasingly complex and significantly increases the difficulty of construction safety management.

[0003] Currently, there are technical solutions for tunnel safety monitoring. For example, Chinese invention patent publication number CN119878301A discloses a tunnel lining health monitoring system and method based on acoustic emission. By deploying an acoustic emission receiver matrix on the tunnel lining, the system captures the elastic wave signals released when the lining material cracks. After signal processing, the source point of the acoustic emission events is located and the cumulative number is counted. An alarm is issued when the cumulative number reaches a preset threshold.

[0004] The aforementioned approach focuses on damage detection of the support structure itself for tunnel safety monitoring. However, in extra-long tunnels, multiple lithological units are often traversed. When the tunnel transitions from one lithology to another, sudden changes in surrounding rock pressure levels and stiffness mismatches can trigger separation at the support interface. This separation is not caused by damage to the support structure itself, but rather by a disconnect between the deep surrounding rock compression and the shallow support response. This mechanical imbalance often precedes damage to the support structure. If this interface separation is not effectively monitored, and warnings are issued directly based on support structure damage, the warnings will be delayed, preventing timely reinforcement measures from being taken. Summary of the Invention

[0005] To solve the above-mentioned technical problems, or at least partially solve them, the present invention provides a smart monitoring and dynamic early warning system for long tunnels with complex geological conditions.

[0006] The objective of this invention can be achieved through the following technical solution: a smart monitoring and dynamic early warning system for complex geological tunnels, comprising: a displacement and strain sensing unit: the deep surrounding rock displacement, shallow support displacement and support axial strain distribution are collected by displacement sensing points arranged along the longitudinal direction of the tunnel and strain sensing points laid along the inner wall of the support.

[0007] Vibration sensing unit: Acoustic emission sensors attached to the cross-section of the support structure collect vibration events such as support cracking or surrounding rock detachment.

[0008] Separation identification unit: The real-time transfer ratio is calculated based on the ratio of deep to shallow displacement increments, and the axial strain gradient reversal zone is identified. Combined with the fact that the transfer ratio is lower than the baseline and the reversal zone covers the displacement sensing section, the separation of the surrounding rock support is initially judged.

[0009] Reversibility judgment unit: After initial judgment, monitor the delay time from deep displacement step to shallow response. If the delay time exceeds the limit multiple times and is accompanied by vibration events, output an irreversible signal; otherwise, output a reversible signal.

[0010] Early warning output unit: When an irreversible signal is received, an emergency warning is triggered. When a reversible signal is received, the displacement sensing section is compared with the adjacent section to identify suspected abnormalities. When an abnormality is suspected, a prompt warning is triggered.

[0011] Combining all the above technical solutions, the positive effects of this invention are as follows: 1. By simultaneously monitoring the displacement of deep surrounding rock and the displacement of shallow support, calculating the transmission ratio of their increments, and combining this with the identification of axial strain gradient reversal sections, this invention enables the judgment of the separation of the surrounding rock support interface. Compared with existing technologies that only focus on the damage detection of the support structure itself, this invention can capture the precursors of the imbalance of the mechanical relationship of the surrounding rock support before the support structure shows obvious damage, effectively extending the early warning time window, thereby reducing the safety risks in the construction of long tunnels with complex geology.

[0012] 2. Based on the judgment of the separation of the surrounding rock support interface, this invention further distinguishes between reversible poor contact and irreversible interface separation by monitoring the delay time from deep displacement step to shallow response and combining it with vibration events. This makes the judgment of the separation state more accurate and reliable. The graded early warning output can provide differentiated decision-making basis for on-site construction, which can prevent overreaction and work stoppage losses, and avoid safety accidents caused by delayed early warning. This is conducive to improving the pertinence and practicality of dynamic early warning for complex geological long tunnels. Attached Figure Description

[0013] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the system composition of the present invention;

[0015] Figure 2 This is a flowchart illustrating the process of identifying the axial strain gradient reversal zone in this invention.

[0016] Figure 3 This is a flowchart illustrating the initial determination of the separation of surrounding rock support in this invention. Detailed Implementation

[0017] 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.

[0018] In the construction of extra-long tunnels, the tunnel cross-section often traverses complex geological structures, successively encountering various rock types such as hard rock and soft rock. When the tunnel transitions from one rock type to another, the mechanical parameters of the surrounding rock undergo abrupt changes, leading to a stiffness mismatch between the surrounding rock and the constructed support structure. At this point, the deeper surrounding rock continues to compress into the tunnel, while the shallow support structure, due to its relatively insufficient stiffness or altered contact state with the surrounding rock, cannot synchronously generate the same displacement response, thus triggering separation of the surrounding rock support interface.

[0019] This separation is essentially an interruption of the mechanical transmission chain. It occurs before visible damage such as cracking and spalling appears in the support structure and is an early precursor to the instability of the surrounding rock support. If this interface separation phenomenon is not monitored and treated, the support structure will gradually lose its load-bearing capacity, which may induce local collapse or overall instability, seriously threatening construction safety.

[0020] To address the aforementioned problems, this invention proposes a smart monitoring and dynamic early warning system for long tunnels with complex geological conditions, comprising a displacement-strain sensing unit, a vibration sensing unit, a separation identification unit, a reversibility judgment unit, and an early warning output unit, such as... Figure 1 As shown, the output terminals of the displacement strain sensing unit and the vibration sensing unit are respectively connected to the input terminal of the separation identification unit; the output terminal of the separation identification unit is connected to the input terminal of the reversibility judgment unit; the output terminal of the reversibility judgment unit is connected to the input terminal of the early warning output unit. Each unit is connected in series and cooperates to form a complete link from data acquisition, feature recognition, state determination to graded early warning.

[0021] The specific implementation of the present invention will be described in detail below, unit by unit.

[0022] The displacement and strain sensing unit is used to collect the displacement of deep surrounding rock, the displacement of shallow support, and the axial strain distribution of the support from displacement sensing points arranged along the longitudinal direction of the tunnel and strain sensing points laid along the inner wall of the support.

[0023] Considering that the separation of the surrounding rock and support interface is characterized by the continuous inward compression of the deep surrounding rock into the tunnel, while the shallow support structure fails to undergo synchronous displacement due to stiffness mismatch or changes in contact state, leading to a gradual increase in the relative displacement difference between the two, the primary task in achieving separation judgment is to simultaneously acquire the displacement response of the deep surrounding rock and the shallow support, as well as the strain state of the support structure, in order to establish a quantitative basis for the mechanical transmission relationship. Therefore, multi-level displacement sensing and strain sensing are required.

[0024] Specifically, the displacement and strain sensing unit works as follows: Given that the lithological abrupt change interface refers to the boundary location where the mechanical parameters of the surrounding rock change significantly when the tunnel passes through different rock strata, and the vicinity of this interface is prone to separation of the surrounding rock support interface, during displacement and strain sensing, it is necessary to control this interface to capture the precursors of the mechanical transmission relationship disorder. Therefore, based on the location of the lithological abrupt change interface provided by geological forecasts during tunnel construction, deep displacement sensing points are anchored along the longitudinal direction of the tunnel in the undisturbed surrounding rock on the side away from the tunnel face of the lithological abrupt change interface to obtain the true surrounding rock displacement unaffected by the support. Shallow displacement sensing points at the same longitudinal section are fixed to the shotcrete surface or the flange of the steel arch frame to obtain the response of the support structure to the deformation of the surrounding rock. This longitudinal section is the displacement sensing section, used to establish the spatiotemporal correspondence between deep and shallow displacements. Displacement gauges can be used as the displacement sensing points.

[0025] Strain sensing points are continuously laid along the inner wall of the support. Strain gauges can be used for these points. Each strain sensing point is aligned longitudinally with the nearest displacement sensing section to spatially correlate local strain changes with the displacement differences of the corresponding sections.

[0026] After installation, deep displacement sensing points, shallow displacement sensing points, and strain sensing points are synchronously triggered at a fixed sampling period to read the absolute displacement value of each displacement sensing point and the strain value of each strain sensing point. The absolute displacement value refers to the cumulative spatial change of subsequent measurements relative to the initial displacement reading after the displacement sensing point has stabilized. The strain value reflects the degree of tension or compression of the surface material of the support structure along the tunnel's longitudinal direction.

[0027] The strain values ​​at each strain sensing point are arranged in longitudinal order along the tunnel to form a longitudinal distribution sequence of the support axial strain.

[0028] The vibration sensing unit is used to collect vibration events of support cracking or surrounding rock detachment by acoustic emission sensors attached to the cross-section of the support structure.

[0029] After displacement and strain sensing, it is possible to determine whether the mechanical transmission relationship between the surrounding rock and the support is disordered. However, displacement and strain reflect a macroscopic and relatively slow deformation process, while the vibration signals released instantaneously when the support cracks or the surrounding rock falls off have sudden and localized characteristics, and can more sensitively capture the microscopic fracture signals during the interface separation process. Therefore, the introduction of acoustic emission sensing in this invention helps to verify the authenticity of the separation state and provides evidence for distinguishing between reversible and irreversible separation.

[0030] In one implementation method of the present invention, the vibration sensing unit works as follows: When the support structure develops microcracks due to stress or the surrounding rock blocks detach locally, the strain energy stored inside the material is released instantaneously in the form of elastic waves. These elastic waves propagate in the medium and can be captured by the sensor. Thus, the acoustic emission sensor senses the high-frequency elastic waves released by the support structure in a continuous sampling manner and converts the elastic waves into electrical signals to form the original vibration signal sequence.

[0031] During periods without vibration events, signal amplitude samples are continuously collected for a certain duration. The sample amplitudes are divided into several continuous amplitude intervals. The number of sample points in each interval is counted, i.e., the frequency. An amplitude distribution histogram is generated with amplitude as the x-axis and frequency as the y-axis. The interval with the highest frequency in the histogram is identified as the main peak. The frequency of each interval is checked sequentially along the direction of increasing amplitude to find the first local trough. The amplitude corresponding to the trough is used as the background amplitude threshold.

[0032] When the vibration amplitude of a certain segment in the original vibration signal sequence continuously exceeds the background amplitude threshold, it indicates that the energy of the signal segment has exceeded the normal environmental noise fluctuation range, and it is very likely caused by vibration sources such as support cracking or surrounding rock falling off. The signal segment is marked as a vibration event, and the trigger time of the event is recorded.

[0033] Vibration events and their triggering times are arranged in chronological order to form a vibration event sequence.

[0034] The separation identification unit is used to calculate the real-time transfer ratio from the ratio of deep to shallow displacement increments, and to identify the axial strain gradient reversal zone. Combined with the fact that the transfer ratio is lower than the baseline and the reversal zone covers the displacement sensing section, the separation of the surrounding rock support is initially determined.

[0035] After the displacement-strain sensing unit acquires the absolute displacement of the deep surrounding rock, the absolute displacement of the shallow support, and the axial strain distribution of the support, the mechanical transmission relationship between the surrounding rock and the support can be analyzed using the above data to determine whether interface separation has occurred. The specific judgment process consists of the following three steps:

[0036] Step 1: Calculate the real-time transfer ratio

[0037] During tunnel excavation and support, the stress in the surrounding rock is continuously released, and the deep surrounding rock undergoes slow compression deformation over time. Simultaneously, the shallow support structure also exhibits a corresponding displacement response under the pressure of the surrounding rock. Therefore, the absolute displacement values ​​of both the deep surrounding rock and the shallow support typically change between two adjacent sampling times, resulting in deep displacement increments and shallow displacement increments. The transfer ratio, defined as the ratio of the shallow displacement increment to the deep displacement increment, is used to quantify the efficiency of the transfer of pressure from the deep surrounding rock to the shallow support. When the transfer ratio decreases, it indicates that the support has failed to deform synchronously with the surrounding rock, and interface voids or slippage may occur.

[0038] The specific calculation process is as follows: (11) Based on the deep absolute displacement value and shallow absolute displacement value of two adjacent samplings, calculate the deep displacement increment and shallow displacement increment respectively. The purpose is to obtain the spatial change of the surrounding rock and support within a sampling period, so as to provide basic data for subsequent ratio calculation.

[0039] (12) After each calculation of the deep displacement increment and the shallow displacement increment, considering that the transmission ratio is defined as the ratio of the shallow displacement increment to the deep displacement increment, its physical meaning is the amount of support displacement that can be caused by a unit surrounding rock displacement. This ratio is meaningful only when the surrounding rock continues to squeeze into the tunnel, that is, when the deep displacement increment is positive. If the deep displacement increment is zero or negative, that is, the surrounding rock has not undergone new compression or even rebound, then the ratio is undefined or negative, and cannot correctly reflect the interface mechanical transmission efficiency. Therefore, it is necessary to first determine whether the deep displacement increment is greater than zero.

[0040] a) If the deep displacement increment is greater than zero, it indicates that the surrounding rock is still squeezing into the tunnel. The ratio of the shallow displacement increment to the deep displacement increment is then calculated and used as the real-time transfer ratio at the current sampling moment. This ratio reflects the amount of support displacement caused by a unit of surrounding rock displacement. The closer the transfer ratio is to 1, the more complete the surrounding rock displacement is transferred to the support, indicating good coordinated deformation between the two. A transfer ratio less than 1 indicates a delayed support response, with some surrounding rock displacement being absorbed or consumed by the interface, suggesting a tendency for voiding or slippage. A transfer ratio close to 0 indicates that the support has not moved with the surrounding rock, and the interface has severely separated. The transfer ratio is stored at the tail of a fixed-length first-in-first-out queue. This queue stores historical transfer ratio values ​​from the most recent sampling periods for subsequent statistical feature extraction. Historical transfer ratio values ​​are removed from the head of the queue to ensure that the queue always retains the latest fixed amount of data, preventing unlimited growth.

[0041] b) If the deep displacement increment is not greater than zero, it means that the surrounding rock has not generated new compression displacement or rebound. In this case, the transfer ratio is not calculated and the queue remains unchanged. This is because when the surrounding rock does not move into the tunnel, the mechanical transfer relationship of the surrounding rock-support interface does not change, and the existing queue can be maintained.

[0042] It should be noted that if the transfer ratio is not calculated for three or more consecutive sampling periods because the deep displacement increment is not greater than zero, it indicates that the surrounding rock has not experienced new compression displacement for a long time, and the historical transfer ratio values ​​in the queue may be outdated. In this case, the entire transfer ratio queue should be cleared to avoid retaining invalid data. After clearing, the queue should be reinitialized for the next valid transfer ratio calculation.

[0043] Step 2: Identify the axial strain gradient reversal zone

[0044] The axial strain gradient is the rate of change of strain along the longitudinal direction of the tunnel in the inner wall of the support. Under normal stress, the strain usually decreases monotonically along the excavation direction, i.e., the gradient is negative. When a void occurs in a certain section, the strain distribution will change in the opposite direction, the gradient sign will change from negative to positive or the absolute value will increase abnormally, forming a gradient reversal. Identifying the reversal section is the longitudinal location where the separation occurred.

[0045] See Figure 2 As shown, the specific implementation is as follows: (21) Take the direction pointing to the tunnel face on the tunnel design axis as the tunneling direction, and define the longitudinal interval between two adjacent strain sensing points as a segment along this direction. This step discretizes the continuous support into multiple analysis units, which facilitates the segment-by-segment evaluation of strain changes.

[0046] (22) For each segment, the strain of the next strain sensing point is calculated and the strain of the previous strain sensing point is subtracted to obtain the strain difference. The difference is divided by the longitudinal distance between the two sensing points to obtain the axial strain gradient of the segment. The gradient value reflects the rate of change of strain per unit length.

[0047] (23) Assign a gradient sign according to the positive or negative value of the strain difference. When the strain difference is positive, the gradient sign is recorded as positive, indicating that the strain increases along the tunneling direction, that is, the tensile strain is greater or the compressive strain is smaller closer to the tunnel face, which is an abnormal state. When the strain difference is negative, the gradient sign is recorded as negative, indicating that the strain decreases along the tunneling direction, which is a normal compressive state.

[0048] (24) In order to establish a comparison benchmark under normal stress conditions, it is necessary to obtain the stable period data before the lithological change and when the surrounding rock support is in a good contact state.

[0049] The specific determination method is as follows: In the early stage of tunnel excavation into a new lithological unit, deep displacement values ​​are continuously collected. The difference between two adjacent sampling values ​​is divided by the sampling time interval to obtain the deep displacement change rate during that period. When the deep displacement change rate approaches zero for several consecutive sampling cycles, it is determined that the current period is stable.

[0050] During the stabilization period, the following records are executed segment by segment: Stable value of gradient symbol: The gradient symbol of the segment at all sampling times during the stabilization period is counted, and the symbol with the highest frequency of occurrence is taken as the normal gradient symbol of the segment.

[0051] Fluctuation range of absolute gradient value: Collect the absolute values ​​of axial strain gradient at all sampling times during the stabilization period of this section, and take the minimum and maximum values ​​as the lower limit and upper limit of normal fluctuation, respectively.

[0052] (25) During real-time monitoring, the gradient sign and absolute value of each current segment are compared with the sign and fluctuation range of the corresponding segment recorded during the stable period.

[0053] When the current gradient sign of a certain section is opposite to the gradient sign recorded during the stable period, or when the absolute value of the current gradient exceeds the upper limit of the fluctuation range during the stable period, it indicates that the support stress state of the section has become abnormal, and there is a high probability of local voiding. The longitudinal start and end positions of the section (i.e., the mileage of the strain sensing points at both ends) are marked as gradient reversal sections.

[0054] Step 3: Initial assessment of the separation of surrounding rock support

[0055] The transfer ratio decrease and the gradient inversion section covering the current section are jointly determined to confirm whether separation has occurred. See [link to relevant documentation]. Figure 3 As shown, the specific implementation is as follows: (31) During the stable period before the lithological change and when the surrounding rock support is in normal contact, the minimum value in the real-time transmission ratio queue is taken as the transmission ratio baseline value. This baseline represents the lowest transmission efficiency that the surrounding rock support may reach under normal conditions, and serves as a reference benchmark for subsequent judgment on whether an abnormal decline has occurred.

[0056] It should be noted that if the stabilization condition cannot be met within several consecutive sampling periods, the minimum value of the transfer ratio queue within the current sliding window will be used as a temporary baseline, and monitoring will continue until the stabilization period occurs and then recalibration will be performed.

[0057] (32) During real-time monitoring, the minimum value in the current transmission ratio queue is obtained and compared with the transmission ratio baseline value. If the current minimum value is lower than the baseline, it indicates that the support response has been significantly weakened during the recent rock compression and the interface transmission efficiency has been lower than normal.

[0058] (33) Obtain the longitudinal start and end positions of the most recently identified gradient reversal section and determine whether the gradient reversal section covers the longitudinal position of the current displacement sensing section. This is because the gradient reversal section provides spatial evidence to confirm whether abnormal strain occurs near the current monitoring section.

[0059] If the current minimum transfer ratio is lower than the baseline transfer ratio, and the gradient reversal section covers the current displacement sensing section, then both the decrease in mechanical transfer efficiency and the location of spatial strain anomalies are met simultaneously, and the surrounding rock support is initially judged to be separated.

[0060] The above-mentioned collaborative judgment method for the separation of surrounding rock support effectively avoids false alarms from a single parameter and improves the reliability of the initial judgment.

[0061] The reversibility judgment unit is used to monitor the delay time from deep displacement step to shallow response after the initial judgment. If the delay time exceeds the limit multiple times and is accompanied by vibration events, an irreversible signal is output; otherwise, a reversible signal is output.

[0062] After the initial assessment of the separation of the surrounding rock support is completed, it indicates that the interface has undergone a certain degree of voiding or slippage. However, at this time, the separation may still be in a recoverable stage, such as being able to be re-compacted through grouting, or it may continue to deteriorate and develop into irreversible complete separation. If an early warning is issued directly based on the initial assessment results, it is easy to cause an overreaction; conversely, if no distinction is made, the best time for treatment may be delayed.

[0063] Therefore, based on the initial judgment, the present invention further introduces the delay time between the deep displacement step and the shallow response, and combines it with vibration events to distinguish between reversible poor contact and irreversible interface separation.

[0064] The specific implementation is described in the following example: First, the delay time from deep displacement step to shallow response is monitored.

[0065] After the initial judgment of the separation of the surrounding rock support, the displacement difference between adjacent sampling periods of the deep surrounding rock is tracked. This difference is used to determine whether the surrounding rock has undergone short-term accelerated compression. This is because only when the surrounding rock suddenly produces a significant displacement increment can the response lag of the shallow support be effectively observed. When the difference exceeds the allowable limit, it is considered that a deep displacement step has occurred, and the current time is recorded as the start time of the step, representing that the surrounding rock has begun a significant compression push. The allowable limit refers to the maximum absolute value of the deep displacement increment between two adjacent sampling periods within the normal construction period. For example, within 10 consecutive construction days without blasting disturbance, support cracking, or abnormal deformation records, the absolute value of the deep displacement between adjacent sampling periods can be calculated daily, and the maximum value among all increments can be taken as the allowable limit.

[0066] Shallow displacement is continuously observed from the moment of step start. When the shallow displacement shows a positive increment in two consecutive sampling periods, where the positive increment is an increase in shallow displacement relative to the previous moment, it means that the support has started to move with the surrounding rock. This moment is recorded as the response moment. The reason for needing two consecutive positive increments is to eliminate misjudgments caused by a single random fluctuation and to confirm that the support has indeed started to respond.

[0067] Subtracting the step start time from the response time yields the delay time corresponding to the current deep displacement step. This delay time reflects the time difference required for the support response after the surrounding rock is squeezed, and is a dynamic indicator of the interface mechanical transmission efficiency: the shorter the delay, the better the interface contact; the longer the delay, the more severe the interface slippage or voiding, and the longer the surrounding rock thrust needs to be transmitted to the support.

[0068] Multiple deep displacement step events are captured continuously, with a certain time interval between events to ensure independence, such as an interval of more than several sampling periods. The delay time of each event is calculated for subsequent statistical judgment.

[0069] Then, output an irreversible or reversible confirmation signal.

[0070] Considering the differences in surrounding rock characteristics and support conditions in different tunnel sections, it is necessary to establish a normal delay benchmark for the current tunnel displacement sensing section.

[0071] Specifically, during the stable period before lithological abrupt changes and when the surrounding rock support is in normal contact, the delay times corresponding to all deep displacement steps are statistically analyzed, and the arithmetic mean is calculated as the average delay time of the displacement sensing section. This average value represents the response speed under normal coordinated deformation.

[0072] The actual capture delay time after each initial separation is compared with the average delay time mentioned above.

[0073] Given the difference in delay time between reversible and irreversible separation, the delay time in the reversible state is extended but to a limited extent and is not necessarily accompanied by continuous vibration; while the delay time in the irreversible state will increase and be accompanied by vibration events such as support cracking or surrounding rock collapse.

[0074] Based on this, the following logic applies: if the current delay time exceeds a set multiple of the average delay time, such as twice, and there is at least one vibration event within the time interval from the start of the step to the response time, it indicates that the interface separation has caused significant response lag and is accompanied by microscopic damage, and this is considered irreversible evidence.

[0075] When three consecutive deep displacement steps produce irreversible evidence, it indicates that the separation state continues to deteriorate and cannot be recovered, and an irreversible signal is output.

[0076] If three irreversible pieces of evidence are not accumulated within the set time after the initial judgment of the separation of the surrounding rock support, it means that the interface separation has not reached the irreversible level, and a reversible signal is output. The set time is determined according to the average time window required for three deep displacement step events to occur continuously in the current section under normal construction conditions, that is, the length of time from the start of the first step event to the end of the third step event.

[0077] The warning output unit is used to trigger an emergency warning when it receives an irreversible signal, and to compare the displacement sensing section with the adjacent section to identify any abnormality when it receives a reversible signal. If there is any abnormality, a prompt warning is triggered.

[0078] After the reversibility assessment, the separation state of the surrounding rock support is clearly defined, at which point targeted graded early warning can be carried out.

[0079] When an irreversible signal is received, it indicates that the separation of the displacement sensing section interface has developed into an irreversible severe state, and the support structure is about to or has already lost its load-bearing capacity. At this time, an emergency warning is triggered, the on-site audible and visual alarm is activated, and a work stoppage order is pushed out to buy time for handling.

[0080] If construction continues without triggering an early warning, it could lead to major safety accidents such as landslides.

[0081] When a reversible signal is received, it indicates that although the displacement sensing section has separated, it has not yet reached an irreversible state. At this point, it is necessary to further determine whether the separation is a local isolated phenomenon or a regional problem. For this purpose, anomaly identification is performed to determine whether it is necessary to alert on-site personnel. The specific operation is as follows: After receiving the reversible signal, search along the tunnel longitudinal direction towards the tunnel face (upstream) and the tunnel entrance (downstream) for sections adjacent to the current displacement sensing section that have not yet been identified as rock support separation. Obtain the transfer ratio and axial strain gradient reversal zone status of these adjacent sections. The purpose of this step is to determine whether the separation has spread to adjacent areas.

[0082] If there are sections with a transfer ratio lower than the baseline or gradient reversal sections covering adjacent sections, it indicates that the surrounding rock support separation has occurred in multiple adjacent sections. Even if the displacement sensing section is not yet irreversible, it indicates that the problem may be spreading or is itself a regional geological problem. At this time, an anomaly is identified, triggering a warning to remind on-site personnel to expand the investigation scope.

[0083] If no such anomalies are found in adjacent cross sections, it indicates that only the displacement sensing cross section has local reversible separation, and it does not affect the surrounding area. In this case, no warning is needed, and monitoring can continue.

[0084] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0085] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0086] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0087] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A complex geological long tunnel intelligent monitoring and dynamic early warning system, characterized in that, include: Displacement and strain sensing unit: Displacement sensing points arranged along the longitudinal direction of the tunnel and strain sensing points laid along the inner wall of the support are used to collect the displacement of the deep surrounding rock, the displacement of the shallow support, and the axial strain distribution of the support. Vibration sensing unit: Acoustic emission sensors attached to the cross-section of the support structure collect vibration events of support cracking or surrounding rock falling off. Separation identification unit: The real-time transfer ratio is calculated based on the ratio of deep to shallow displacement increments, and the axial strain gradient reversal zone is identified. Combined with the fact that the transfer ratio is lower than the baseline and the reversal zone covers the displacement sensing section, the separation of the surrounding rock support is initially judged. Reversibility judgment unit: After initial judgment, monitor the delay time from deep displacement step to shallow response. If the delay time exceeds the limit multiple times and is accompanied by vibration events, output an irreversible signal; otherwise, output a reversible signal. Early warning output unit: When an irreversible signal is received, an emergency warning is triggered. When a reversible signal is received, the displacement sensing section is compared with the adjacent section to identify suspected abnormalities. When an abnormality is suspected, a prompt warning is triggered.

2. The intelligent monitoring and dynamic early warning system for complex geological long tunnels as described in claim 1, characterized in that: The displacement sensing points arranged along the longitudinal direction of the tunnel and the strain sensing points laid along the inner wall of the support are arranged in the following manner: Based on the location of the lithological abrupt change interface provided by the geological forecast, deep displacement sensing points are anchored in the undisturbed surrounding rock on the side away from the tunnel face along the longitudinal direction of the tunnel. Shallow displacement sensing points at the same longitudinal section are fixed to the surface of the shotcrete or the flange of the steel arch. This longitudinal section is the displacement sensing section. Strain sensing points are continuously laid along the inner wall of the support, and each strain sensing point is aligned longitudinally with the nearest displacement sensing section.

3. The complex geological long tunnel intelligent monitoring and dynamic early warning system according to claim 1, characterized in that: The process of collecting deep surrounding rock displacement, shallow support displacement, and support axial strain distribution is as follows: The deep displacement sensing point, shallow displacement sensing point and strain sensing point are synchronously triggered with a fixed sampling period, and the absolute displacement value of each displacement sensing point and the strain of each strain sensing point are read. The strain values ​​at each strain sensing point are arranged in longitudinal order along the tunnel to form a longitudinal distribution sequence of the support axial strain.

4. The intelligent monitoring and dynamic early warning system for complex geological long tunnels as described in claim 1, characterized in that: The process of collecting vibration events related to support cracking or surrounding rock detachment is as follows: Acoustic emission sensors detect the original vibration signal sequence generated by the support structure using a continuous sampling method; When the vibration amplitude of a certain segment in the original vibration signal sequence continuously exceeds the background amplitude threshold, the segment of signal is marked as a vibration event, and the trigger time of the event is recorded. Vibration events and their triggering times are arranged in chronological order to form a vibration event sequence.

5. The complex geological long tunnel intelligent monitoring and dynamic early warning system according to claim 3, characterized in that: The process for calculating the real-time transfer ratio is as follows: Based on the deep absolute displacement value and shallow absolute displacement value of two adjacent samplings, calculate the deep displacement increment and shallow displacement increment respectively; After each calculation of the deep displacement increment and the shallow displacement increment, determine whether the deep displacement increment is greater than zero; If the deep displacement increment is greater than zero, the ratio of the shallow displacement increment to the deep displacement increment is calculated as the real-time transfer ratio at the current sampling time. The real-time transfer ratio is stored at the tail of a fixed-length first-in-first-out queue, while the historical transfer ratio value at the head of the queue is removed. If the deep displacement increment is not greater than zero, the transfer ratio is not calculated, and the queue remains unchanged.

6. The complex geological long tunnel intelligent monitoring and dynamic early warning system according to claim 3, characterized in that: The identification of the axial strain gradient reversal zone is carried out according to the following process: The tunneling direction is defined as the direction pointing from the tunnel face on the tunnel design axis. The longitudinal interval between two adjacent strain sensing points along this direction is defined as a segment. For each segment, the strain of the next strain sensing point is subtracted from the strain of the previous strain sensing point to obtain the strain difference. This difference is then divided by the longitudinal distance between the two sensing points to obtain the axial strain gradient of that segment. The gradient sign is assigned according to the sign of the strain difference: the gradient sign is positive when the strain difference is positive, and negative when the strain difference is negative. Before the lithological abrupt change and during the stable period when the surrounding rock support is in normal contact, the stable value of the gradient sign and the fluctuation range of the absolute value of the gradient are recorded segment by segment. During real-time monitoring, the gradient sign and absolute value of each current segment are compared with the sign and fluctuation range of the corresponding segment recorded during the stable period, segment by segment. When the sign of the current gradient in a certain segment is opposite to the sign recorded during the stable period, or when the absolute value of the current gradient exceeds the upper limit of the fluctuation range during the stable period, the vertical start and end positions of the corresponding segment are marked as gradient reversal segments.

7. The complex geological long tunnel intelligent monitoring and dynamic early warning system according to claim 5, characterized in that: The initial assessment of surrounding rock support separation includes the following steps: During the stable period before lithological abrupt change and when the surrounding rock support is in normal contact, the minimum value in the real-time transfer ratio queue is taken as the transfer ratio baseline value. During real-time monitoring, the minimum value in the current transfer ratio queue is obtained and compared with the transfer ratio baseline value; Obtain the longitudinal start and end positions of the most recently identified gradient inversion section, and determine whether the gradient inversion section covers the longitudinal position of the current displacement sensing section. If the current minimum transfer ratio is lower than the baseline transfer ratio, and the gradient reversal section covers the current displacement sensing section, then the surrounding rock support is initially judged to be separated.

8. The complex geological long tunnel intelligent monitoring and dynamic early warning system according to claim 1, characterized in that: The process of monitoring the delay time from deep displacement step to shallow response is as follows: When the surrounding rock support separation is initially judged, the difference between adjacent sampling periods of the deep displacement of the surrounding rock is tracked. When the difference exceeds the allowable limit, the current time is recorded as the step start time. The allowable limit refers to the maximum absolute value of the deep displacement increment between two adjacent sampling periods during the normal construction period. The shallow displacement is continuously observed from the moment of step start. When the shallow displacement shows a positive increment in two consecutive sampling periods, the moment is recorded as the response moment. Subtracting the step start time from the response time yields the delay time corresponding to the current deep displacement step.

9. The intelligent monitoring and dynamic early warning system for complex geological long tunnels as described in claim 8, characterized in that: The irreversible signal is determined according to the following process: The arithmetic mean of the delay times corresponding to all deep displacement steps is calculated as the average delay time during the stable period before lithological abrupt change and when the surrounding rock support is in normal contact. Compare the calculated delay time with the average delay time. If the current delay time exceeds a set multiple of the average delay time, and there is at least one vibration event within the time interval from the start of the step to the response time, it is considered as irreversible evidence. When three consecutive deep displacement steps produce irreversible evidence, an irreversible signal is output. If three irreversible pieces of evidence are not accumulated within the set time period after the initial judgment of the separation of the surrounding rock support, a reversible signal will be output.

10. The complex geological long tunnel intelligent monitoring and dynamic early warning system according to claim 1, characterized in that: The process of comparing the displacement sensing section with adjacent sections to identify suspected anomalies is as follows: After receiving the reversible signal, search along the tunnel longitudinal direction towards the face and the tunnel entrance for sections adjacent to the displacement sensing section that have not yet been identified as separated from the surrounding rock support, and obtain their transfer ratio and axial strain gradient reversal zone. If there are sections with a transmission ratio lower than the baseline or sections covered by reversal sections in adjacent sections, then an anomaly is suspected.

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