State determination and active construction method of self-stable bearing structure of deep soft rock roadway

Abstract

This invention discloses a method for determining the state and actively constructing a self-stabilizing bearing structure in deep soft rock tunnels. First, a database of the physical and mechanical properties of the surrounding rock and a database of arching stress states are established. By comparing layers, the existence and specific height of a stable arching height are determined. If it exists, the plastic deformation of the surrounding rock and the support load are calculated based on this height, and parameters for primary pressure relief and secondary pressure resistance are designed. If it does not exist, the surrounding rock strength is improved through grouting modification, and the determination is re-evaluated. Fracturing is performed near the stable arching height to cut off the deep stress transmission path and induce an active bearing structure. On-site construction follows the sequence of primary support, secondary support, and pre-fracturing. When no stable arching is found, a grouting process is added, and a monitoring system is deployed for dynamic feedback. This invention achieves a shift from empirical design to quantitative analysis. By constructing a deep self-stabilizing bearing structure and allowing controllable deformation in the shallow layer, it effectively controls large deformations in deep soft rock tunnels, balancing safety and economy.

Description

Technical Field

[0001] This invention relates to the field of coal mine roadway support and reinforcement technology, and in particular to a method for determining the state and actively constructing a self-stabilizing bearing structure for deep soft rock roadways. Background Technology

[0002] As coal mining depths continue to increase, the problem of controlling large deformations in deep, high-stress soft rock roadways has become increasingly prominent. The concept of roadway surrounding rock control has evolved from passive lining and active reinforcement to the New Austrian Tunneling Method (NATM), which allows for limited deformation of the surrounding rock. However, these concepts primarily stem from tunnel engineering projects aimed at long-term stability and strict deformation control, and are extremely costly. Coal mine roadways differ fundamentally: they emphasize the stability of the overall structure during their service life, while allowing for limited and controllable deformation of the surrounding rock to adapt to high-stress environments and maintain economic efficiency.

[0003] Currently, the secondary support methods commonly used in engineering still largely rely on experience-based design, lacking a systematic analysis of the self-bearing potential and stress evolution path of the surrounding rock, making it difficult to achieve a scientific match between support parameters and surrounding rock deformation. Existing technologies suffer from the following drawbacks: existing support schemes are mostly determined based on engineering experience or analogy, lacking a systematic quantitative assessment of the mechanical properties of the surrounding rock and the arching effect, leading to a mismatch between support parameters and the actual bearing capacity of the surrounding rock; traditional methods often passively resist surrounding rock pressure, failing to actively identify or construct self-stabilizing bearing structures (such as pressure arches) within the surrounding rock, resulting in high support costs and limited effectiveness; under deep high ground stress conditions, existing technologies lack means to actively intervene in the stress transmission path of the surrounding rock, allowing harmful deep stress to continuously transmit to the surrounding roadway, making deformation difficult to converge; the timing and parameters of primary and secondary support lack scientific basis, often applying rigid support too early or too late, either causing support failure or failing to effectively control deformation; for weak surrounding rock that cannot naturally form an arch, existing technologies do not provide a systematic closed-loop design process for grouting modification before determining the bearing structure. Summary of the Invention

[0004] To address the aforementioned technical shortcomings, the purpose of this invention is to provide a method for determining the state and actively constructing a self-stabilizing bearing structure for deep soft rock roadways. This method is based on engineering geological information to scientifically analyze the stability of the surrounding rock in soft rock roadways in coal mines, and constructs or reconstructs a surrounding rock bearing structure with overall self-stabilizing bearing capacity and locally acceptable deformation, so as to meet the safety and stability requirements of coal mine roadways.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: This invention provides a method for determining the state and actively constructing a self-stabilizing bearing structure in deep soft rock tunnels, comprising the following steps: a. Obtain physical and mechanical property data of the surrounding rock of the roadway roof and establish a primary database characterizing the strength properties of the surrounding rock.W M Furthermore, based on the tunnel design parameters and initial support experience parameters, the arching stress state of the surrounding rock was analyzed, and a second database characterizing the bearing stress requirements of the surrounding rock was established. W S ; b. The first database W M With the second database W S By comparing each layer, it can be determined whether the roof of the tunnel has a stable arch height that can form a self-stabilizing load-bearing structure. If a stable arch height exists h 1, then based on this stable arch height h 1. Calculate the plastic deformation of the surrounding rock and the support load (the intensity of the top pressure on the support components). q 1 and total top pressure Q d ), and then design the allowable deformation of the compression support. d 2. Support force requirements for secondary compression support P 1. Based on this, we can deduce the appropriate timing t1 for secondary compressive support; If there is no stable arch height h 1. Design a grouting modification scheme to improve the strength characteristics of the surrounding rock, and repeat this step based on the strength characteristics of the surrounding rock after grouting modification to determine a new stable arching height. h 2. Therefore, the allowable deformation of the compression support should be redesigned. d 3. Support force requirements for secondary compression support P 2; c. Based on the stable arch height determined in step b, formulate a pre-fracturing scheme for deep rock mass to cut off the transmission of stress field between the arch and the surrounding rock near the pre-fracturing stress arch line, and induce the surrounding rock to form an active bearing structure. d. Based on the judgment results and design of step b and the pre-fracturing scheme of step c, carry out on-site construction in the order of primary support, secondary support and pre-fracturing. In cases where there is no stable arch height, add a grouting modification process after primary support. At the same time, during the construction process, a monitoring system is set up to dynamically monitor and provide feedback on the surrounding rock condition.

[0006] Preferably, in step a, the first database W M =[ M 1, M 2, M 3, M 4,…], M i =[ σ ci , τ 0i , C i , φ i , f i , s ∞ ] T ,in i This is a rock stratum. σ c Uniaxial compressive strength, τ 0 represents shear strength. C For cohesion, φ It is the internal friction angle. f The hardness is based on the Protodyakonov scale. s ∞ For long-term intensity; second database W S =[ S 1, S 2, S 3, S 4,…], S i =[ σ i , τ i ] T , σ i The maximum normal stress in the rock arch. τ i This represents the maximum shear stress at the top of the rock arch.

[0007] Preferably, in step a, the arching stress state is calculated according to the following formula: ; in, The lateral pressure coefficient, For rock normal stress, For rock density, For the width of the alley, This is the height of the arch.

[0008] Preferably, in step b, the method for determining the stable arch height is as follows: starting from the top stratum, compare layer by layer from bottom to top; when a certain height is reached... h When the mechanical strength index in the second database is consistently higher than the mechanical strength index of the corresponding layer in the first database and the excess reaches a preset threshold (furthermore, the preset threshold can be 20%), this height is determined as the stable arch height.

[0009] Preferably, in step b, the plastic deformation of the surrounding rock and the intensity of the top pressure on the support components are calculated based on the stable arch height.q 1 and total top pressure Q d At that time, an elastoplastic mechanical model was used for calculation, specifically: ; in, For Poisson's ratio, For the radius of the plastic zone, For elastic modulus, ρ is the Protodyakonov hardness, and c is the cohesive force.

[0010] Preferably, in step b, when a stable arch height exists, the allowable deformation of the surrounding rock is... d 2. Support strength requirements P 1. Unlike conventional secondary support calculations, this method, based on the self-stabilizing bearing structure of the surrounding rock, allows for a certain amount of deformation in the surrounding rock. d 2 and support requirements P 1. Determine using the following formula: in, φ For internal friction angle, P For the original rock stress, Rp Let r be the radius of the plastic zone and r be the distance between the rock mass under study and the center of the tunnel.

[0011] Preferably, in step b, when there is no stable arching height, the new stable arching height after grouting modification is determined from the first database. W M With the second database W S The mechanical strength indices are obtained under the condition that they are approximately equal.

[0012] Preferably, the pre-fracking scheme in step c is selected from one or more of deep hole blasting, hydraulic fracturing, or supercritical CO2 fracturing.

[0013] Preferably, the monitoring system in step d includes a laser rangefinder or convergence meter for monitoring the convergence deformation of the roadway surface, a deep and shallow hole top plate delamination meter for monitoring delamination inside the rock strata, a borehole inspection instrument for observing the development of fractures inside the surrounding rock, and an anchor bolt force gauge or force-measuring anchor bolt for monitoring the stress on the support structure.

[0014] Preferably, in step d, the timing of implementing secondary compression support is determined based on the inflection point of the surrounding rock convergence-time monitoring curve.

[0015] Beneficial effects: 1. This method establishes a database of rock mass physical and mechanical properties and a database of arching stress state, and compares and determines the stable arching height layer by layer, making the support design based on evidence and significantly improving its scientificity and reliability.

[0016] 2. This method scientifically constructs a phased collaborative support system of "first-stage pressure relief + second-stage pressure resistance". It determines the allowable deformation based on the plastic deformation of the surrounding rock, determines the support force requirement based on the total top pressure, and determines the optimal timing of secondary support based on the convergence-time curve, thus achieving precise matching between the support and the deformation stage of the surrounding rock.

[0017] 3. This method involves deep-hole blasting, hydraulic fracturing, or supercritical CO2 fracturing near the stable arching height to artificially cut off the transmission path of harmful deep stress to the roadway, induce the surrounding rock to form an active bearing structure, and actively intervene in the surrounding rock stress. For cases where natural arching is not possible, the strength of the surrounding rock is improved by grouting modification, and the arching height and support parameters are re-determined, forming a complete closed loop of "evaluation-improvement-re-evaluation-design" to avoid blind support.

[0018] 4. By using equipment such as laser rangefinders, roof delamination meters, borehole inspection instruments, and anchor bolt force gauges, the deformation of the surrounding rock and the stress on the support are monitored in real time, enabling visualized and dynamic optimization control of the construction process. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A flowchart illustrating the state determination and active construction method for a self-stabilizing bearing structure in a deep soft rock tunnel, as provided in an embodiment of the present invention; Figure 2 A diagram for determining whether a rock structure arch exists, provided in an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating a stable arch height as provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of grouting when there is no stable arch height, provided by an embodiment of the present invention; Figure 5 The image shows the pre-compression cracking pattern provided in an embodiment of the present invention. Detailed Implementation

[0021] 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.

[0022] like Figure 1 As shown, this embodiment of the invention provides a method for determining the state and actively constructing a self-stabilizing bearing structure in deep soft rock tunnels, including the following steps: Step 1. Engineering geological investigation and basic database construction: First, in the soft rock tunnel sections requiring stability modification, select representative locations. Using a geological drilling rig, arrange core drilling holes perpendicular to the tunnel roof. The drilling depth should cover a range of 3 to 5 times the tunnel height above the tunnel roof (for example, if the tunnel height is 4 meters, the core drilling depth should be 12-20 meters) to ensure that complete strata information within the potential arching influence area is obtained.

[0023] The extracted rock cores are numbered and sealed according to different lithologies and stratigraphic positions (usually every 1-2 meters or according to obvious lithological changes). The samples are then sent to a laboratory for systematic physical and mechanical property testing according to national standards (such as GB / T50266). At least the following core parameters must be obtained for each rock sample layer: uniaxial compressive strength σ. c Shear strength τ0, cohesion C, internal friction angle φ, Protodyakonov hardness coefficient f, and long-term strength s characterizing the rheological properties of rocks. ∞ All test results are organized by layer, and a mechanical parameter vector is constructed for each layer i: M i =[ σ ci , τ 0i , C i , φ i , f i , s ∞ ] T .

[0024] Ultimately, a database of the physical and mechanical properties of the roof rock mass in this region was formed. W M =[ M 1, M 2, M 3, M 4,…].

[0025] Step 2. Analysis of the effect of surrounding rock stabilization structure in the tunnel and establishment of a stress state database: Using the rock strata information obtained in the above steps, combined with the specific design parameters of the target tunnel (such as the cross-sectional shape of a straight wall semi-circular arch, width × height = 5.0m × 4.0m), burial depth (such as -850m horizontal), original rock stress field (which can be obtained through geostress measurement or empirical estimation), and the parameters of the currently failed or existing primary support (such as anchor bolt length and spacing), a mechanical analysis model of the surrounding rock after tunnel excavation is established.

[0026] Numerical simulation software (such as FLAC3D, UDEC) or analytical methods based on specific theories (such as Protodyakonov's arch theory, Terzaghi's formula) can be used to simulate and calculate the stress redistribution state of the surrounding rock after tunnel excavation. The focus is on analyzing different layers of the roof (related to W...). M The database corresponds to the stresses borne by the rock mass during the natural arching process. For each layer i, the maximum principal stress (which can be considered as the maximum normal stress σ) at its key crown point (or element) is extracted. i ) and maximum shear stress τ i .

[0027] The two calculated stress values ​​for each layer are combined into a stress state vector: S i =[σ i ,τ i ] T The calculation results from all layers are summarized to establish an arch stress state database W. S That is, W S =[S1,S2,S3,…]. This database W S This reflects the inherent strength requirements of the surrounding rock to maintain a self-stabilizing "stable arch".

[0028] Step 3. Determining the arch height of the self-stabilizing structure and quantifying the top slab load: See Figure 2 , will database W M (Intensity of rock “supply”) and W S (The strength of the "demand" in the formation of the arch) is compared and verified layer by layer and indicator by indicator.

[0029] Judgment principle: Starting from the top surface (i=1 layer), compare layer by layer from bottom to top. For each layer i, check its W. S The stress value (σ) i ,τ i Is it less than or equal to W? M The corresponding strength value (σ) ci ,τ 0i A certain proportion (e.g., 80%, i.e., leaving a certain safety reserve) of the rock mass is considered sufficient to form a stable bearing arch. This comparison continues upwards until the kth layer at a certain height h1, where W... S The stress value in the middle began to consistently exceed W.M The stress exceeds 80% of the corresponding strength value (i.e., the stress exceeds the strength by more than 20%). At this point, height h1 is considered the stable arching height, and the rock mass at layer k and above is considered unstable or unable to form an effective arch. Rock mass below height h1 constitutes a "stable bearing arch," see [reference needed]. Figure 3 .

[0030] Based on the determined stable arch height h1 and the mechanical parameters of the rock mass within its range, the cumulative plastic deformation d1 of the rock mass inside the arch under the action of the secondary stress field is calculated using elastoplastic theory (e.g., considering the Mohr-Coulomb yield criterion).

[0031] Furthermore, based on the weight, plastic zone range, and stress distribution of the rock mass within the arch, a mechanical model is established to calculate the top pressure distribution pattern (such as uniform distribution or parabolic distribution) acting on the roadway support structure. Based on this distribution, the top pressure intensity q1 (unit: kPa) and total top pressure Q of the support components (such as the scaffolding) can be derived and calculated. d (Unit: kN / m). The specific calculation formula is as follows: ; Step 4. Design of phased collaborative support parameters: Based on the judgment result of step three, implement branch design: Scenario A (with a stable arch height h1): The design of single-stage pressure-release support aims to allow the surrounding rock to release some deformation energy while ensuring safety. An allowable deformation d2 is set, which should be less than the theoretical plastic deformation d1. Typically, d2 = (0.6~0.8) * d1, and determined based on engineering experience. Support methods include extendable rock bolts (such as structural stretchable rock bolts) and flexible metal mesh. Installation should occur immediately after tunnel excavation.

[0032] Secondary compression support design: The goal is to provide final stable support after the deformation rate of the surrounding rock has significantly decreased. The required support force P1 must satisfy: P1≥k*(Q) d The support width is defined as follows: k is the safety factor (usually taken as 1.2~1.5). High-strength, high-rigidity structures are selected for the support, such as U-shaped steel collapsible supports or high-prestressed anchor cable trusses.

[0033] Determining the timing of support: By analyzing the convergence-time monitoring curve of the surrounding rock in this mining area or similar roadways, the inflection point where deformation transitions from the acceleration phase to the deceleration or uniform phase is identified. The estimated time t1 corresponding to this inflection point (e.g., 20-35 days after excavation) is the reasonable time to implement secondary compressive support.

[0034] Case B (no stable arch height h1): See Figure 4 ; Grouting modification process: First, design and implement grouting reinforcement of the surrounding rock. Cement-based or chemical grout can be used as the grouting material, and the grouting parameters (pressure, hole depth, grout mix ratio) are determined based on the degree of rock fragmentation and fracture development. The goal is to significantly improve the cohesion (C-value), internal friction angle (φ-value), and overall integrity of the shallow surrounding rock.

[0035] Parametric redesign: After grouting, the rock mass in the improved area is sampled and tested, or the improvement in its mechanical parameters is estimated based on experience, and the database W is updated. M The analysis of steps two and three was repeated to verify the stable arch height h2 after grouting. Based on the stable arch height h2, the allowable deformation d3 for the first pressure relief and the secondary compressive support force requirement P2 were recalculated and determined.

[0036] Step 5. Design of pre-fracturing scheme with active arching control: To optimize the bearing capacity of the arch and achieve active control of surrounding rock stress, this embodiment provides a pre-fracturing intervention scheme. The core of this pre-fracturing intervention scheme is to apply pre-fracturing intervention along the predetermined arching boundary line on both sides and the roof of the roadway (see...). Figure 5 A series of deep fracturing boreholes will be constructed near the stable arch height h1 or h2, with the borehole depth required to penetrate the predetermined arch line. Depending on the lithological conditions, three fracturing methods can be selected: For rock formations with high hardness, deep-hole blasting is used to create a through-crack at the arch line by controlling the amount of explosive and the detonation sequence. In low-permeability rock formations, hydraulic fracturing is used, which uses high-pressure water injection to generate and expand fractures in the rock mass. Alternatively, supercritical CO2 fracturing, a new environmentally friendly technology, can be used to break rocks by utilizing the special physicochemical properties of supercritical CO2. This method has a wide range of adaptability and is suitable for various lithological conditions.

[0037] The technical objective of this scheme is to create directional mechanically weak surfaces through artificial fracturing, thereby effectively cutting off the direct transmission path of high ground stress from deeper parts of the arch to the surrounding roadway, forcing the pressure arch to clearly form at the designed height of h1 (or h2), and promoting the further integration of the rock mass inside the arch into a complete, stable, and actively load-bearing structural system.

[0038] Step Six. On-site Integrated Construction and Information-based Monitoring: According to the design plan, on-site construction and monitoring are organized according to the following process: First, after the tunnel is excavated, a primary support is promptly implemented, namely, the installation of the designed pressure relief anchor bolts (cables) and flexible metal mesh; if there is no stable arch height (situation B), the surrounding rock needs to be grouted and reinforced according to the design after the primary support.

[0039] Subsequently, after the tunnel has initially stabilized (usually 3-7 days after the first support), deep rock mass pre-fracturing operations are carried out as planned. Next, based on the optimal timing t1 determined by monitoring data, secondary compression support construction is conducted, installing support structures such as high-strength metal scaffolding or high-prestressed anchor cables. Simultaneously, a full-process monitoring system is deployed from the start of tunnel excavation. The monitoring network mainly includes deploying laser rangefinders or convergence meters on the tunnel cross-section to monitor surface convergence deformation; installing deep and shallow benchmark roof delamination meters to monitor internal delamination of the rock strata; deploying anchor bolt (cable) force gauges and force-measuring anchor bolts to monitor the stress on the support structure in real time; and using borehole inspection instruments to periodically observe the development of internal fractures in the surrounding rock. All monitoring data are collected and analyzed in real time and compared with design prediction values. Once abnormal deformation or stress is detected, subsequent support parameters or construction timing can be dynamically adjusted, thereby achieving information-based and dynamic optimized design and construction control.

[0040] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for determining the state and actively constructing a self-stabilizing bearing structure in deep soft rock tunnels, characterized in that, Includes the following steps: a. Obtain physical and mechanical property data of the surrounding rock of the roadway roof and establish a primary database characterizing the strength properties of the surrounding rock. W M Furthermore, based on the tunnel design parameters and initial support experience parameters, the arching stress state of the surrounding rock was analyzed, and a second database characterizing the bearing stress requirements of the surrounding rock was established. W S ; b. The first database W M With the second database W S By comparing each layer, it can be determined whether the roof of the tunnel has a stable arch height that can form a self-stabilizing load-bearing structure. If a stable arch height exists h 1, then based on this stable arch height h 1. Calculate the plastic deformation of the surrounding rock and the intensity of the top pressure on the support components. q 1 and total top pressure Q d Therefore, the allowable deformation of the compression support is designed. d 2. Support force requirements for secondary compression support P 1. Based on this, we can deduce the appropriate timing t1 for secondary compressive support; If there is no stable arch height h 1. Design a grouting modification scheme to improve the strength characteristics of the surrounding rock, and repeat this step based on the strength characteristics of the surrounding rock after grouting modification to determine a new stable arching height. h 2. Therefore, the allowable deformation of the compression support should be redesigned. d 3. Support force requirements for secondary compression support P 2; c. Based on the stable arch height determined in step b, formulate a pre-fracturing scheme for deep rock mass to cut off the transmission of stress field between the arch and the surrounding rock near the pre-fracturing stress arch line, and induce the surrounding rock to form an active bearing structure. d. Based on the judgment results and design of step b and the pre-fracturing scheme of step c, carry out on-site construction in the order of primary support, secondary support and pre-fracturing. In cases where there is no stable arch height, add a grouting modification process after primary support. At the same time, during the construction process, a monitoring system is set up to dynamically monitor and provide feedback on the surrounding rock condition.

2. The method for determining the state and actively constructing the self-stabilizing bearing structure of deep soft rock tunnels according to claim 1, characterized in that, In step a, the first database W M =[ M 1, M 2, M 3, M 4,…], M i =[ σ ci , τ 0i , C i , φ i , f i , s ∞ ] T ,in i This is a rock stratum. σ c Uniaxial compressive strength, τ 0 represents shear strength. C For cohesion, φ It is the internal friction angle. f The hardness is based on the Protodyakonov scale. s ∞ For long-term intensity; second database W S =[ S 1, S 2, S 3, S 4,…], S i =[ σ i , τ i ] T , σ i The maximum normal stress in the rock arch. τ i This represents the maximum shear stress at the top of the rock arch.

3. The method for determining the state and actively constructing the self-stabilizing bearing structure of deep soft rock tunnels according to claim 2, characterized in that, In step a, the arching stress state T H Calculate according to the following formula: ； in, The lateral pressure coefficient, For rock normal stress, For rock density, For the width of the alley, This is the height of the arch.

4. The method for determining the state and actively constructing the self-stabilizing bearing structure of deep soft rock tunnels according to claim 1, characterized in that, In step b, the method for determining the stable arch height is as follows: starting from the top stratum, compare layer by layer from bottom to top. When a certain height is reached... h When the mechanical strength index in the second database is consistently higher than the mechanical strength index of the corresponding layer in the first database and the excess reaches a preset threshold, that height is determined as the stable arch height.

5. The method for determining the state and actively constructing the self-stabilizing bearing structure of deep soft rock tunnels according to claim 2, characterized in that, In step b, the amount of plastic deformation of the surrounding rock is calculated based on the stable arch height. The intensity of the top pressure on the support components q 1 and total top pressure Q d At that time, an elastoplastic mechanical model was used for calculation, specifically: ； in, For Poisson's ratio, For the radius of the plastic zone, For elastic modulus, ρ is the Protodyakonov hardness, and c is the cohesive force.

6. The method for determining the state and actively constructing the self-stabilizing bearing structure of deep soft rock tunnels according to claim 5, characterized in that, In step b, when a stable arch height exists, the allowable deformation of the surrounding rock is... d 2. Support strength requirements P 1. Unlike conventional secondary support calculations, this method, based on the self-stabilizing bearing structure of the surrounding rock, allows for a certain amount of deformation in the surrounding rock. d 2 and support requirements P 1. Determine using the following formula: in, φ For internal friction angle, P For the original rock stress, Rp Let r be the radius of the plastic zone and r be the distance between the rock mass under study and the center of the tunnel.

7. The method for determining the state and actively constructing the self-stabilizing bearing structure of deep soft rock tunnels according to claim 1, characterized in that, In step b, when no stable arching height exists, the new stable arching height after grouting modification is determined in the first database. W M With the second database W S The mechanical strength indices are obtained under the condition that they are approximately equal.

8. The method for determining the state and actively constructing the self-stabilizing bearing structure of deep soft rock tunnels according to claim 1, characterized in that, The pre-fracking scheme in step c is selected from one or more of deep hole blasting, hydraulic fracturing, or supercritical CO2 fracturing.

9. The method for determining the state and actively constructing the self-stabilizing bearing structure of deep soft rock tunnels according to claim 1, characterized in that, The monitoring system in step d includes a laser rangefinder or convergence meter for monitoring the convergence deformation of the roadway surface, a deep and shallow hole top plate delamination meter for monitoring delamination inside the rock strata, a borehole inspection instrument for observing the development of fractures inside the surrounding rock, and an anchor bolt force gauge or force-measuring anchor bolt for monitoring the stress on the support structure.

10. The method for determining the state and actively constructing the self-stabilizing bearing structure of deep soft rock tunnels according to claim 1, characterized in that, In step d, the timing of implementing secondary compression support is determined based on the inflection point of the surrounding rock convergence-time monitoring curve.

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