A shield closed-loop risk control method for dense railway under water-rich sand layer karst coupled stratum based on multi-source uncertainty field

Abstract

The application discloses a dense railway under rich water sand layer karst coupled stratum shield closed loop risk control method based on a multi-source uncertainty field, and relates to the technical field of urban rail transit shield construction control and complex geotechnical treatment. U(x, y, z) ; a comprehensive risk index R is calculated; according to R , a shield influence area is divided into an upper control subsidence area, a middle stable profile area and a lower water-resisting bearing area, and differentiated reinforcement is implemented on the activated functional area; linkage adjustment is performed on shield working face support parameters, advancing parameters and synchronous grouting parameters; the treatment effect is verified, when the residual risk is higher than a preset threshold, recirculation or reinforcement is performed, and the three-dimensional stratum uncertainty field is reconstructed and the comprehensive risk index is recalculated until the residual risk reaches the preset requirement. The application can significantly reduce the missed risk in the lack of holes, hole moving and geophysical prospecting reference sections, control the railway subgrade settlement and inhibit the rich water sand layer-karst water connected type gushing.

Description

Technical Field

[0001] This invention relates to the field of shield tunneling construction control and complex soil and rock treatment technology for urban rail transit, and more specifically to a closed-loop risk control method for shield tunneling in dense railway water-rich sandy karst coupled strata based on multi-source uncertainty fields. Background Technology

[0002] As urban rail transit construction penetrates deeper into complex geological formations, tunnel sections often need to traverse water-rich sand layers, karst limestone, deep soft soil, and existing railway sensitive protection areas. In such projects, risks such as face instability, water and sand inrush, tunnel head collapse, uneven settlement of railway subgrade, collapse of karst caves and roof slabs at the bottom of the tunnel, and long-term creep during operation are complex and difficult to cover with a single control method.

[0003] From a mechanical-seepage coupling perspective, the risks of shield tunneling in water-rich sand layers stem not only from low stratum strength but also from the seepage erosion chain caused by high permeability, high water pressure, and structural fissures or disturbance channels. When the confined sand layer and the underlying limestone karst water communicate hydraulically through direct contact surfaces, structurally weak zones, or disturbance channels, the strata are prone to water and sand leakage, sudden surface subsidence, and even collapse. Existing research has shown that the combined effect of segment joint leakage and high water pressure in water-rich sand layers can trigger soil erosion and settlement amplification effects.

[0004] For karst exploration, a technical approach has gradually formed in engineering practice: ground geophysical exploration - drilling verification - cross-hole fine characterization. For densely built-up areas with limited drilling conditions, the micro-motion method can identify bedrock interfaces and low-velocity anomaly zones through apparent shear wave velocity profiles. Empirically, apparent shear wave velocities greater than 300 m / s often correspond to limestone strata, while low anomalies of 150–240 m / s may correspond to loose layers, infill, or karst cave anomalies. Meanwhile, urban rail transit engineering monitoring standards require the inclusion of buildings, roadbeds, tunnel structures, and track geometry into a systematic monitoring system.

[0005] Existing publicly available technologies can be broadly categorized into four types. The first type is quantitative solutions, such as determining the volume of karst caves and the amount of grouting based on borehole and fractal parameters. The second type is range-based solutions, such as determining the treatment range of karst caves at the bottom of tunnels through numerical simulation. The third type is predictive solutions, such as using neural networks or machine learning to predict the surface settlement of shield tunnels. The fourth type is single-scenario control solutions, such as directional deep-hole grouting for high-speed railway subgrades, monitoring methods for underpasses of viaducts, or isolation structures for railway pile foundations.

[0006] The above solutions address the issues of how much to inject, the scope of treatment, how to predict settlement, and how to protect individual objects, but they still have the following shortcomings: First, existing solutions often implicitly assume that borehole data, or the true value, is the only basis for assessment. For sections with missing boreholes, shifted boreholes, or sections with only geophysical interpretation, risks are only indicated in words, without considering the reliability of the data itself as a calculable engineering variable that can trigger construction actions. Second, existing solutions primarily rely on geometric dimensions (cavity height, roof thickness, distance from the tunnel, etc.) to determine whether treatment is necessary. They lack an independent quantitative pathway for the key inducing factor of hydraulic connectivity between sand layers and karst water. This easily leads to situations where treatment is missed even though the cavities are geometrically distant but hydraulically highly connected, or where there are cavities geometrically but the impermeable layer is sufficient and therefore does not require treatment. Third, existing solutions often target a single protection objective (such as controlling only subgrade settlement or only controlling tunnel face stability), lacking a unified scheduling framework for the three objectives of controlling upper settlement, stabilizing the middle excavation, and ensuring the lower impermeable bearing capacity. Fourth, existing solutions mostly stop at prediction or monitoring, failing to directly map shield telemetry anomalies and monitoring responses into actionable grouting zones, material selection, and shield control parameter adjustments, thus failing to form a complete construction closed loop.

[0007] Therefore, there is still a lack of a method in this field that can first quantify the reliability of stratigraphic data under conditions of missing boreholes, shifted boreholes, and only local geophysical exploration results, and then combine the degree of sand-karst water connectivity, the stability of the cave roof, the strength of the weak bearing layer, and real-time shield tunneling telemetry anomalies to differentiate, verify, and recharge control the three objectives of upper railway and surface settlement, middle excavation stability, and lower water-resistant bearing capacity.

[0008] In summary, a closed-loop risk control method for shield tunneling in dense railway water-rich sandy strata coupled with karst formations based on multi-source uncertainty fields is proposed to address the difficulties existing in the current technology. Summary of the Invention

[0009] In view of this, the present invention provides a closed-loop risk control method for shield tunneling in dense railway water-rich sandy strata coupled with karst based on multi-source uncertainty fields. This method solves the problems in the prior art, such as the lack of quantitative processing of the uncertainty of exploration data, the failure to separate and assess the geometric risk of karst and the hydraulic connectivity risk, the lack of unified scheduling of the three control targets (upper, middle and lower), and the lack of a construction closed loop for shield tunneling telemetry anomalies and monitoring responses.

[0010] To achieve the above objectives, the present invention provides the following technical solution: A closed-loop hazard control method for shield tunneling in dense railway-supported water-rich sandy-karst coupled strata based on multi-source uncertainty fields includes the following steps: S1. Obtain borehole data, original design borehole location and measured borehole location data, geophysical data, groundwater level and pore pressure data, karst parameters, soft soil parameters, real-time tunneling parameters of the shield tunnel, and monitoring data of the surface, roadbed and tunnel structure. S2. Based on the offset relationship between the original designed borehole positions and the measured borehole positions, the missing borehole situation, the geophysical anomaly zones, and the supplementary verification detection results, a three-dimensional geological uncertainty field distributed along the shield tunnel axis is constructed. U(x,y,z) ; S3. Based on the three-dimensional stratigraphic uncertainty field U(x,y,z) The uncertainty coefficient of the formation is calculated based on the following factors: hydraulic connectivity between sand layer and karst water, stability of the cave roof, condition of weak bearing layer, anomalies in shield tunneling telemetry, and monitoring response. U Hydraulic connectivity coefficient between sand layer and karst water C h Stability coefficient of the cave roof K c , coefficient of weak bearing layer S b Shield tunneling anomaly coefficient A t and monitoring response coefficient M t The weighted sum is used to obtain the comprehensive risk index. R ; S4. Based on the comprehensive risk index R The shield tunneling impact zone is divided into at least one of the following functional zones: upper settlement control zone, middle stability zone, and lower water-resistant bearing zone, and differentiated reinforcement is implemented for the activated functional zone. S5. Based on the comprehensive risk index R Based on its changing trends, the shield tunnel face support parameters, propulsion parameters, and synchronous grouting parameters are adjusted accordingly. S6. After completing the differentiated reinforcement in S4 and the shield tunneling linkage in S5, the treatment effect is verified based on wave velocity recovery, pore pressure attenuation, grouting volume stability, and settlement rate attenuation. When the residual risk exceeds the preset threshold, re-injection or reinforcement is performed, and the process returns to S2 to reconstruct the three-dimensional stratum uncertainty field and recalculate the comprehensive risk index. R Until the residual risk reaches the preset requirements.

[0011] Optionally, in S2, when any measured borehole location deviates more than 2m from the original design borehole location, a displacement attenuation is applied to the ground confidence level within the control range of the measured borehole location; when the distance from the tunnel centerline projection to the nearest measured borehole location in a certain section exceeds 20m, the section is defined as a high uncertainty corridor, and it is required that 2m before the shield tunneling machine enters... D ~5 D Supplementary verification and detection will be carried out within the scope, including D The outer diameter of the tunnel boring machine.

[0012] Optionally, the geophysical data in S1 shall include at least the micromotion inversion of the apparent shear wave velocity profile, and the section with the apparent shear wave velocity greater than 300 m / s shall be regarded as the bedrock candidate area, and the low value anomaly area of ​​150 m / s to 240 m / s shall be regarded as the loose layer or karst cave anomaly candidate area, and the candidate areas shall be corrected in combination with the borehole or front verification detection results.

[0013] Optionally, the formation uncertainty coefficient can be calculated separately in S3. U Hydraulic connectivity coefficient between sand layer and karst water C h Stability coefficient of the cave roof K c , coefficient of weak bearing layer S b Shield tunneling anomaly coefficient A t and monitoring response coefficient M t The weighted sum is used to obtain the comprehensive risk index. R The specific content is as follows:

[0014] in, These are the weighting coefficients. ; when R A value <0.35 is considered low risk; when 0.35 ≤ R A value <0.55 is classified as medium risk; when 0.55 ≤ R A value <0.75 is considered a high-risk level; when R A value ≥0.75 is considered an extremely high risk level.

[0015] Optional, in S4, based on the comprehensive risk index R The shield tunneling impact zone is divided into at least one functional zone from the following: upper settlement control zone, middle stability zone, and lower water-resistant bearing zone. The specific details of implementing differentiated reinforcement for the activated functional zones are as follows: The upper control settlement zone is located 0.3 meters above the tunnel arch. D ~0.8 D Within the range, and extending 1.5 meters forward along the line. D ~3 D Extend backwards by 0.5 D ~1.5 D， in D The outer diameter of the tunnel boring machine; The intermediate stability region is located 0.2 meters outside the tunnel outline. D ~0.6 D Within the circumferential range, D It is the outer diameter of the shield, and at least covers the gap behind the shield tail wall; The lower aquitard bearing zone is located within the influence zone between the tunnel floor and the aquitard, rock surface, or roof of a high-risk karst cave; when the aquitard thickness is greater than 3m and C h When the water level is below the preset threshold, the treatment of the lower water-resistant bearing area will not be initiated.

[0016] Optionally, the upper settling zone uses a low-disturbance, micro-expansion slurry with a funnel viscosity of 35s to 55s, a bleeding rate of no more than 5%, a 7-day uniaxial compressive strength of 0.5MPa to 2.0MPa, and a volume expansion rate of 0.2% to 1.0%. The medium-stable contour zone uses a stable filling grout with an initial setting time of 15 min to 60 min, a water bleeding rate of no more than 3%, and a 28-day uniaxial compressive strength of 2 MPa to 5 MPa. The lower impermeable bearing zone shall be constructed with at least a sealing grout and a reinforcing grout in sequence, wherein the permeability coefficient of the solidified sealing grout shall not exceed 1×10⁻⁶. -7 m / s, the 7-day uniaxial compressive strength of the skeleton slurry is 3MPa~8MPa.

[0017] Optionally, in S5, based on the comprehensive risk index R The specific details regarding the adjustment of shield tunnel face support parameters, propulsion parameters, and synchronous grouting parameters, along with their changing trends, are as follows: When the tunnel boring machine is an earth pressure balance shield, the linkage adjustment variables include earth chamber pressure, screw speed, propulsion speed, total thrust, cutterhead torque, amendment dosage, synchronous grouting pressure, and synchronous grouting volume. When the tunnel boring machine is a slurry balance tunnel boring machine, the linkage adjustment variables include chamber pressure, slurry density, slurry viscosity, circulation flow rate, synchronous grouting pressure, and synchronous grouting volume. when R Increase or A t In case of an anomaly, the system automatically implements a series of coordinated controls, including reducing the advance speed, increasing the support pressure safety factor, improving the real-time filling coefficient of synchronous grouting, and shortening the risk verification cycle.

[0018] Optionally, the following treatment logic is adopted for the geometric-hydraulic dual threshold: when K c low and C h When the level is low, only enhanced monitoring is activated; when K c low and C h When the temperature is high, activate the sealing mode of the lower water-resistant bearing area; when K c High and C hWhen the threshold is low, initiate bridging or fill mode; when K c High and C h When the temperature is high, a combination of blocking, bridging, and filling modes is activated.

[0019] Optionally, in S6, after completing the differentiated reinforcement of S4 and the shield tunneling linkage of S5, the treatment effect is verified based on wave velocity recovery, pore pressure attenuation, grouting volume stability, and settlement rate attenuation. When the residual risk exceeds the preset threshold, the specific content of re-grouting or reinforcement is as follows: When verifying the treatment effect of weak bearing stratum sections, post-grouting holes are reserved along the circumferential direction of the risk section segments. The post-grouting holes are arranged at least at the corresponding positions of the arch shoulder, sidewall, or tunnel bottom. When the settlement rate decreases, the pore pressure decreases, or the residual risk index does not meet the preset requirements after treatment, grouting is carried out in the tunnel through the post-grouting holes.

[0020] Optionally, the following content is included in S6 to determine whether the residual risk meets the preset requirements: Apparent transverse wave velocity Vs Recovery from low-value anomaly areas to bedrock candidate thresholds; The pressure drop of the pore pressure falls below the acceptance threshold. Two consecutive reinjections or subsequent grouting volumes falling below the acceptance threshold and no longer increasing; The settlement rate of the ground surface and roadbed decreased to below 0.1 mm / d; Posterior composite risk index R It has been downgraded by more than one level compared to the previous one.

[0021] As can be seen from the above technical solution, compared with the prior art, the present invention provides a closed-loop risk control method for shield tunneling in dense railway water-rich sandy strata coupled with karst formations based on multi-source uncertainty fields, which has the following beneficial effects: (1) This invention directly quantifies engineering conditions such as borehole displacement exceeding 2m, projection distance exceeding 20m from the nearest actual borehole, and section with only geophysical interpretation into a three-dimensional stratigraphic uncertainty field, and in U The high-level section is forcibly triggered to conduct forward verification exploration, which transforms the uncertainty of the exploration data from textual risk warnings into calculable engineering variables that can trigger construction actions, significantly reducing the risk of missing sections, shifted sections, and sections with only geophysical interpretation but no actual drilling verification. (2) This invention combines the geometric risk of karst with the hydraulic connectivity risk of sand layer-karst water through... K c and C hTwo independent sub-indices are evaluated separately, and the combination of their dual thresholds drives the differentiated selection of four treatment modes: "monitoring / blocking / bridging / filling". This avoids the two types of errors in the existing geometric scale-based approach: "not treating what should be treated" and "over-treating". (3) This invention divides the shield tunneling impact zone into an upper control settlement zone, a middle stability contour zone, and a lower water-resistant bearing zone. The targets of the three zones are separated, but they are governed by a unified comprehensive risk index. R The coordinated start-stop system can reduce the peak settlement of railway subgrade, control the evolution of soil behind the tunnel face and shield tail, and cut off the high-permeability connection path in the lower part without increasing the volume of ineffective reinforcement. (4) This invention will detect shield tunneling anomalies. A t With monitoring response M t Residual risks are introduced and directly mapped to the linkage adjustment instructions of advance speed, support pressure safety factor, synchronous grouting filling coefficient and risk verification cycle, so that the method moves from "seeing risks" to "reducing risks", forming a real-time closed loop that can be applied to the shield construction process. (5) This invention provides clear and verifiable closed-loop termination criteria, including wave velocity recovery, pore pressure attenuation, grouting volume stability, settlement rate attenuation and post-test risk level, and is supplemented by the in-tunnel grouting interface with reserved post-grouting holes in the segments, which can significantly reduce long-term creep and uneven settlement in the weak bearing layer during the operation period. Attached Figure Description

[0022] 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0023] Figure 1 A flowchart of a closed-loop hazard control method for shield tunneling in dense railway water-rich sandy karst coupled strata based on multi-source uncertainty field provided by the present invention; Figure 2 A schematic diagram of a three-dimensional uncertainty field and risk corridor provided for this invention; Figure 3 A schematic cross-sectional view of the upper control zone, the middle stable contour zone, and the lower water-resistant bearing zone provided by the present invention; Figure 4 The geometric-hydraulic dual-threshold treatment decision diagram provided by this invention; Figure 5 This invention provides a timing diagram for the linkage of shield tunneling parameters under conditions of increased risk. Figure 6The diagram provided for the effect verification and recharge termination criteria of the present invention includes 6a as wave velocity recovery criterion, 6b as pore pressure attenuation criterion, 6c as grouting rebound stability criterion, and 6d as settlement rate attenuation criterion. Figure 7 The site monitoring layout plan provided for this invention; Figure 8 The diagram provided by the present invention shows the arrangement of grouting holes reserved for the risk section segments, wherein 8a is the cross section of the segment - the location of the grouting hole, and 8b is the circumferential arrangement of the segments along the axial direction, with the grouting holes reserved for the risk section segments (uniformly arranged along the circumference and arranged ring by ring along the axial direction). Among them, 11-Shield axis; 12-Original designed borehole location; 13-Unimplemented borehole location; 14-Relocated borehole; 15-Measured borehole location; 16-Micro-motion inversion profile section; 17-High uncertainty corridor; 18-Front verification detection; 19-Dense railway; 20-Karst limestone; 21-Cave; 22-Tunnel; 23-Upper control settlement zone; 24-Middle stable profile zone; 25-Lower water-resistant bearing zone; 26-Low disturbance micro-expansion grout; 27-Stable filling grout; 28-Plug grout and skeleton grout; 29-Arch shoulder post-grouting hole; 30-Sidewall post-grouting hole; 31-Tunnel bottom post-grouting hole; 32-Post-grouting construction interface. 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] See Figure 1 As shown, this invention discloses a closed-loop risk control method for shield tunneling in dense railway-supported water-rich sandy-karst coupled strata based on multi-source uncertainty fields, comprising the following steps: S1. Obtain drilling data, original design borehole location and measured borehole location data, geophysical data, groundwater level and pore pressure data, karst parameters, soft soil parameters, real-time tunneling parameters of the shield tunnel, and monitoring data of the surface, roadbed and tunnel structure. S2. Based on the offset relationship between the original designed borehole positions and the measured borehole positions, the missing borehole situation, the geophysical anomaly zones, and the supplementary verification detection results, a three-dimensional geological uncertainty field distributed along the shield tunnel axis is constructed. U(x,y,z) ; S3. Based on the three-dimensional stratigraphic uncertainty field U(x,y,z) The uncertainty coefficient of the formation is calculated based on the following factors: hydraulic connectivity between sand layer and karst water, stability of the cave roof, condition of weak bearing layer, anomalies in shield tunneling telemetry, and monitoring response. UHydraulic connectivity coefficient between sand layer and karst water C h Stability coefficient of the cave roof K c , coefficient of weak bearing layer S b Shield tunneling anomaly coefficient A t and monitoring response coefficient M t The weighted sum is used to obtain the comprehensive risk index. R ; S4. Based on the comprehensive risk index R The shield tunneling impact zone is divided into at least one of the following functional zones: upper settlement control zone, middle stability zone, and lower water-resistant bearing zone, and differentiated reinforcement is implemented for the activated functional zone. S5. Based on the comprehensive risk index R Based on its changing trends, the shield tunnel face support parameters, propulsion parameters, and synchronous grouting parameters are adjusted accordingly. S6. After completing the differentiated reinforcement in S4 and the shield tunneling linkage in S5, the treatment effect is verified based on wave velocity recovery, pore pressure attenuation, grouting volume stability, and settlement rate attenuation. When the residual risk exceeds the preset threshold, re-injection or reinforcement is performed, and the process returns to S2 to reconstruct the three-dimensional stratum uncertainty field and recalculate the comprehensive risk index. R Until the residual risk reaches the preset requirements.

[0026] Furthermore, in S2, when any measured borehole location deviates more than 2m from the original design borehole location, a displacement attenuation is applied to the stratum confidence level within the control range of the measured borehole location; when the distance from the tunnel centerline projection to the nearest measured borehole location in a certain section exceeds 20m, the section is defined as a high uncertainty corridor, and it is required that 2m before the shield tunneling machine enters... D ~5 D Supplementary verification and detection will be carried out within the scope, including D This refers to the outer diameter of the tunnel boring machine.

[0027] Furthermore, the geophysical data in S1 includes at least the micromotion inversion of the apparent shear wave velocity profile, and the section with an apparent shear wave velocity greater than 300 m / s is regarded as the bedrock candidate area, and the low value anomaly area of ​​150 m / s to 240 m / s is regarded as the loose layer or karst cave anomaly candidate area. The candidate areas are corrected in combination with the borehole or front verification detection results.

[0028] Furthermore, in S3, the formation uncertainty coefficient is calculated separately. U Hydraulic connectivity coefficient between sand layer and karst water C h Stability coefficient of the cave roof K c , coefficient of weak bearing layer Sb Shield tunneling anomaly coefficient A t and monitoring response coefficient M t The weighted sum is used to obtain the comprehensive risk index. R The specific content is as follows:

[0029] in, These are the weighting coefficients. ; when R A value <0.35 is considered low risk; when 0.35 ≤ R A value <0.55 is classified as medium risk; when 0.55 ≤ R A value <0.75 is considered a high-risk level; when R A value ≥0.75 is considered an extremely high risk level.

[0030] Furthermore, S4 is based on the comprehensive risk index R The shield tunneling impact zone is divided into at least one functional zone from the following: upper settlement control zone, middle stability zone, and lower water-resistant bearing zone. The specific details of implementing differentiated reinforcement for the activated functional zones are as follows: The upper control settlement zone is located 0.3 meters above the tunnel arch. D ~0.8 D Within the range, and extending 1.5 meters forward along the line. D ~3 D Extend backwards by 0.5 D ~1.5 D， in D The outer diameter of the tunnel boring machine; The intermediate stability region is located 0.2 meters outside the tunnel outline. D ~0.6 D Within the circumferential range, D It is the outer diameter of the shield, and at least covers the gap behind the shield tail wall; The lower aquitard bearing zone is located within the influence zone between the tunnel floor and the aquitard, rock surface, or roof of a high-risk karst cave; when the aquitard thickness is greater than 3m and C h When the water level is below the preset threshold, the treatment of the lower water-resistant bearing area will not be initiated.

[0031] Furthermore, the upper settling zone uses a low-disturbance, micro-expansion slurry with a funnel viscosity of 35s–55s, a bleeding rate of no more than 5%, a 7-day uniaxial compressive strength of 0.5MPa–2.0MPa, and a volume expansion rate of 0.2%–1.0%. The medium-stable contour zone uses a stable filling grout with an initial setting time of 15 min to 60 min, a water bleeding rate of no more than 3%, and a 28-day uniaxial compressive strength of 2 MPa to 5 MPa. The lower impermeable bearing zone shall be constructed with at least a sealing grout and a reinforcing grout in sequence, wherein the permeability coefficient of the solidified sealing grout shall not exceed 1×10⁻⁶. -7 m / s, the 7-day uniaxial compressive strength of the skeleton slurry is 3MPa~8MPa.

[0032] Furthermore, S5 is based on a comprehensive risk index. R The specific details regarding the adjustment of shield tunnel face support parameters, propulsion parameters, and synchronous grouting parameters, along with their changing trends, are as follows: When the tunnel boring machine is an earth pressure balance shield, the linkage adjustment variables include earth chamber pressure, screw speed, propulsion speed, total thrust, cutterhead torque, amendment dosage, synchronous grouting pressure, and synchronous grouting volume. When the tunnel boring machine is a slurry balance tunnel boring machine, the linkage adjustment variables include chamber pressure, slurry density, slurry viscosity, circulation flow rate, synchronous grouting pressure, and synchronous grouting volume. when R Increase or A t In case of an anomaly, the system automatically implements a series of coordinated controls, including reducing the advance speed, increasing the support pressure safety factor, improving the real-time filling coefficient of synchronous grouting, and shortening the risk verification cycle.

[0033] Furthermore, the following treatment logic is adopted for the geometric-hydraulic dual threshold: when K c low and C h When the level is low, only enhanced monitoring is activated; when K c low and C h When the temperature is high, activate the sealing mode of the lower water-resistant bearing area; when K c High and C h When the threshold is low, initiate bridging or fill mode; when K c High and C h When the temperature is high, a combination of blocking, bridging, and filling modes is activated.

[0034] Furthermore, in S6, after completing the differentiated reinforcement of S4 and the shield tunneling linkage of S5, the treatment effect is verified based on wave velocity recovery, pore pressure attenuation, grouting volume stability, and settlement rate attenuation. When the residual risk exceeds the preset threshold, the specific content of re-grouting or reinforcement is as follows: When verifying the treatment effect of weak bearing stratum sections, post-grouting holes are reserved along the circumferential direction of the risk section segments. The post-grouting holes are arranged at least at the corresponding positions of the arch shoulder, sidewall, or tunnel bottom. When the settlement rate decreases, the pore pressure decreases, or the residual risk index does not meet the preset requirements after treatment, grouting is carried out in the tunnel through the post-grouting holes.

[0035] Furthermore, the content of S6 for determining whether the residual risk meets the preset requirements is as follows: Apparent transverse wave velocity Vs Recovery from low-value anomaly areas to bedrock candidate thresholds; The pressure drop of the pore pressure falls below the acceptance threshold. Two consecutive reinjections or subsequent grouting volumes falling below the acceptance threshold and no longer increasing; The settlement rate of the ground surface and roadbed decreased to below 0.1 mm / d; Posterior composite risk index R It has been downgraded by one or more levels compared to the previous one.

[0036] Example 1 includes the following: Step 1: Data Acquisition and Preprocessing: The data acquisition subsystem acquires borehole and hole movement information, micro-motion inversion profiles and supplementary geophysical data, groundwater level and pore pressure data, as well as surface / subgrade / segment monitoring data, real-time telemetry parameters of the shield tunnel, and forward verification detection data of the proposed shield tunnel section. After time synchronization and spatial registration, a multi-source database is formed. Step 2: Reconstruction of the three-dimensional stratigraphic uncertainty field: such as Figure 2 As shown, based on the offset relationship between the original designed borehole position 12 and the measured borehole position 15, the situation of the unimplemented borehole position 13, the relocated borehole 14, and the micro-motion inversion profile section 16, a three-dimensional geological uncertainty field distributed along the shield tunnel axis 11 is constructed. ; Three-dimensional stratigraphic uncertainty field U(x,y,z) Construct it according to the following formula:

[0037] in, The horizontal projection distance from the target point to the nearest drilled hole. The reference characteristic length (taken as the outer diameter D of the shield tunnel); , , These are indicator functions for three events: the nearest borehole is a moved borehole with an offset exceeding 2m, the location is a location where no borehole was drilled, and the location only has geophysical interpretation. , , , These are non-negative calibration coefficients; when When the distance is greater than 20 m, the section is defined as a high uncertainty corridor 17, and forward verification detection 18 is required to be initiated within 2D to 5D before the tunnel boring machine enters in order to correct the uncertainty field in real time.

[0038] Step 3: Calculation of Risk Sub-indices and Comprehensive Risk Index: Based on the three-dimensional stratigraphic uncertainty field and multi-source database, the following six sub-indices are calculated respectively: (i) Formation uncertainty coefficient The result obtained from step 2 The representative value within the neighborhood surrounding the target ring is obtained; (ii) Hydraulic connectivity coefficient between sand layer and karst water It is obtained by comprehensively normalizing the minimum vertical distance between the sand layer and the underlying limestone, the thickness of the impermeable layer, the length of the direct contact section between the sand layer and the limestone, the difference in confined hydraulic head, and the continuity of the anomalous zone. (iii) Stability coefficient of the cave roof The result is obtained by normalized weighting of tunnel height, roof thickness, filling condition, and rock mass integrity. (iv) Coefficient of weak bearing layer The value is obtained by normalizing the thickness of the soft soil layer below the tunnel bottom, the compression modulus, and the standard penetration test blow count, etc. (v) Shield tunneling anomaly coefficient The deviation of the relative baseline mean and standard deviation of remote measurements such as thrust, torque, face pressure, propulsion speed, slag moisture content or mud parameters is obtained by normalization. (vi) Monitoring response coefficient It is synthesized from the normalized values ​​of the relative warning limit and control limit of the displacement, settlement rate and pore pressure increment of the ground surface, roadbed, and segment; Overall Risk Index Calculate using the following weighted formula:

[0039] in, These are the weighting coefficients. ;

[0040] Can take equal weight prior As the initial value, it is then calibrated by the leading segment; when R A value <0.35 is considered a low-risk level, corresponding to conventional tunneling and conventional synchronous grouting; When 0.35≤ R A value <0.55 indicates a medium-risk level, requiring enhanced monitoring and supplementary verification. When 0.55≤ R A value less than 0.75 is considered a high-risk level, corresponding to the activation of the upper control zone and the middle stability zone; when R When the value is ≥0.75, it is determined to be an extremely high risk level, which corresponds to the simultaneous activation of the upper control settlement zone, the middle stabilization zone, and the lower water-resistant bearing zone. Step 4: Three-zone differentiated reinforcement: The shield tunneling impact zone is divided into the upper settlement control zone 23, the middle stability zone 24, and the lower water-resistant bearing zone 25. These three zones are spatially separated and their decision-making is based on... R Linked start / stop, such as Figure 3 As shown; The upper control settlement zone 23 is located 0.3D to 0.8D above the arch of tunnel 22, extending forward by 1.5D to 3D and backward by 0.5D to 1.5D along the shield tunneling direction. Its objective is to control the subgrade and surface settlement of the densely packed railway 19 and suppress over-consolidation and external drainage of soft soil. A low-disturbance, micro-expansion slurry 26 is preferred, with a funnel viscosity of 35s to 55s, a bleeding rate of no more than 5%, a 7-day uniaxial compressive strength of 0.5MPa to 2.0MPa, and a volume expansion rate of 0.2% to 1.0%. The intermediate stabilization zone 24 is located in the circumferential area 0.2D to 0.6D outside the tunnel outline and at least covers the void behind the shield tail wall. Its purpose is to stabilize the soil at the tunnel face and behind the shield tail, suppress over-excavation, water loss and attitude deviation. The preferred material is the shape-stabilizing filling grout 27, which has an initial setting time of 15min to 60min, a bleeding rate of no more than 3%, and a 28-day uniaxial compressive strength of 2MPa to 5MPa. The lower impermeable bearing zone 25 is located below the tunnel bottom within the influence zone between the impermeable layer, rock surface or karst limestone 20, and the roof of the medium-to-high-risk karst cave 21. Its objective is to cut off high-permeability connectivity paths and form a bearing bridge shell. Preferably, sealing grout and skeleton grout 28 are used sequentially: the sealing grout is anti-dispersion, has low bleeding, and its permeability coefficient after consolidation is no greater than 1×10⁻⁶. -7 m / s; the 7-day uniaxial compressive strength of the skeleton mortar is 3MPa~8MPa, and coarse aggregate or mortar can be added to form a bridging shell if necessary.

[0041] The following processing logic is adopted for the geometric-hydraulic dual threshold, such as... Figure 4 As shown, Figure 4 It includes four treatment modes: Q1 treatment mode, Q2 treatment mode, Q3 treatment mode, and Q4 treatment mode. (a) when low and In low-temperature conditions (Q1 treatment mode), only enhanced monitoring is activated, and treatment in the lower water-resistant bearing area is not activated. (b) When low and When the water level is high (Q2 treatment mode), the sealing mode of the lower water-resistant bearing zone is activated, which only performs water-resistant interception and does not fully fill the hole; (c) When High and At low temperatures (Q3 treatment mode), the primary function is to carry out bridging, and bridging or filling mode is activated. (d) When High and When the condition is high (Q4 treatment mode), a combination of blocking, bridging, and filling modes is initiated. (e) When the thickness of the waterproof layer is greater than 3 m and If the water level is below the preset threshold, treatment of the lower water-resistant bearing area may not be initiated. Step 5: Adjustment of shield tunneling parameters in conjunction with the overall risk index. R And its changing trends, to implement real-time linkage adjustments to the parameters of the tunnel boring machine, such as Figure 5 As shown; When the tunnel boring machine is an earth pressure balance shield, the linkage adjustment variables include earth chamber pressure, screw speed, propulsion speed, total thrust, cutterhead torque, amendment dosage, synchronous grouting pressure, and synchronous grouting volume. When the tunnel boring machine is a slurry balance tunnel boring machine, the linkage adjustment variables include chamber pressure, slurry density, slurry viscosity, circulation flow rate, synchronous grouting pressure, and synchronous grouting volume. when R Increase or A t In case of an anomaly, the following linkage controls will be automatically executed: (i) reduce the advance speed to 50% to 80% of the baseline value; (ii) increase the support pressure safety factor from 1.0 to 1.15 to 1.30; (iii) increase the synchronous grouting real-time filling coefficient from 1.4 to 1.7 to 2.0; (iv) shorten the risk verification cycle from every 5 rings to every 1 to 2 rings.

[0042] Step 6: Effect Verification and Closed-Loop Reinjection: After completing differentiated reinforcement and shield tunneling linkage, the treatment effect is verified according to the following criteria: Figure 6 As shown, 6a is the wave velocity recovery criterion, 6b is the pore pressure attenuation criterion, 6c is the grouting rebound stability criterion, and 6d is the settlement rate attenuation criterion. (i) Wave velocity recovery criterion: In supplementary micro-motion or trans-aperture wave velocity testing, the apparent shear wave velocity in the original low wave velocity anomaly area. Vs The speed range was restored from 150m / s to 240m / s to over 300m / s, and showed no degradation in two consecutive retests; (ii) Criterion for pore pressure decay: The pore pressure decays to below the acceptance threshold and shows no upward trend; (iii) Criterion for stable grouting volume: The unit grout volume of a single ring is lower than the acceptance threshold and does not rise again after two consecutive reinjections or subsequent grouting. (iv) Criterion for settlement rate attenuation: The settlement rate of the ground surface and roadbed attenuates to below 0.1 mm / d, and the cumulative settlement does not exceed the limit set by the property owner; (v) Posterior risk level criterion: recalculationR A drop of one or more levels compared to the previous ranking; When the residual risk exceeds the preset threshold, reinforcing or reinforcement is carried out through the pre-reserved grouting holes in the risk section segments or the pre-reserved casings on the ground (e.g., Figure 7 , Figure 8 (as shown), and return to step 2 to reconstruct the three-dimensional stratigraphic uncertainty field and recalculate. R The process continues until the residual risk reaches the preset requirements; when the residual risk reaches the preset requirements, the next tunneling cycle begins.

[0043] Example 2, Numerical Leader Verification

[0044] In this embodiment, a typical composite section of water-rich sand layer and karst coupling is selected as the numerical pilot section. The arch of this section is mainly composed of sand layer and silt, and the sidewalls contain fluid plastic silty clay in some areas. The bottom plate is located on fluid plastic silty clay. The sand layer has a confined water head of about 3m to 9m, and in some sections the sand layer is in direct contact with the underlying limestone. A three-dimensional fluid-structure coupled finite element method was used to establish the model. The model dimensions were: 60m horizontally, 80m vertically, and 55m vertically for the railway line; the outer diameter of tunnel 22 was D=6.4m, and the cutterhead diameter was 6.68m; the representative values ​​of the strata parameters were: silt compression modulus of approximately 2.01MPa, silty soil of approximately 2.87MPa, fluid plastic silty clay of approximately 4.90MPa, plastic silty clay of approximately 6.73MPa, SPT blow count of medium-coarse sand of approximately 17.1 blows, and gravelly sand of approximately 16.4 blows.

[0045] Comparative approach: Pre-grouting along a fixed range throughout the entire section and conventional synchronous grouting are used, without distinguishing between geometric risk and hydraulic connectivity risk, and without considering the uncertainty field of the exploration.

[0046] The present invention solution: Execute steps 1 to 6 sequentially, first calculating... U , C h , K c , S b and R ,according to R Launch the corresponding function area and press A t Linked shield parameters and M t Monitor the response coefficient.

[0047] Numerical results (expected) show that: the maximum settlement of the roadbed and surface decreased from 6.5mm-8.5mm in the comparative scheme to 2.8mm-4.0mm in the scheme of this invention, a reduction of approximately 40%-60%; the additional vertical deformation at the tunnel bottom decreased from 5.0mm-6.5mm to 2.5mm-3.8mm, a reduction of approximately 30%-50%; the length of the post-test high-risk zone was shortened from 18m-24m to 6m-12m; the total grouting consumption per unit length decreased from 1.00 (normalized value) to 0.78-0.86, saving approximately 14%-22%; and the proportion of shield tunneling anomalies decreased from 12%-18% to 5%-9%. These results indicate that the present invention does not win by doing more grouting, but rather by more accurate risk identification and concentrated reinforcement, investing limited resources in the areas that truly determine settlement and inrush chains.

[0048] Example 3: Field Pilot Section Test Design

[0049] This embodiment implements a pilot section test for a composite risk section where the tunnel bottom is located on silty soil or fluid plastic cohesive soil.

[0050] On-site setup (such as) Figure 7 ): Set up no less than 3 roadbed settlement sections and 3 surface settlement sections along the route; 2 sets of pore pressure monitoring sections; perform automatic total station attitude verification every 10 rings; continuously record shield tunneling telemetry in key sections; set up static leveling points along the shield tunnel axis 11; uniformly reserve post-grouting holes along the circumferential direction for the segments in risk sections, and arrange them ring by ring along the axial direction, such as Figure 8 As shown, 8a represents the cross-section of the tunnel segment - post-grouting hole location, and 8b represents the axial ring arrangement of the tunnel segments. Post-grouting holes are reserved in the risk section segments (uniformly arranged along the circumference and arranged ring by ring along the axial direction), respectively located at the arch shoulder post-grouting hole 29, the sidewall post-grouting hole 30, and the tunnel bottom post-grouting hole 31, and connected to the grouting system inside the tunnel through the post-grouting construction interface 32. The monitoring items should cover the vertical displacement of the ground surface and roadbed, differential settlement, horizontal displacement of the tunnel structure, pore pressure, and necessary track geometry.

[0051] On-site implementation steps: (i) Before the shield tunnel enters the pilot section, the uncertainty field reconstruction and preliminary calculation are completed within a range of 2D to 3D. R ; (ii) When U or C h If the threshold is exceeded, a supplementary verification probe will be initiated first; (iii) Based on R Decide whether to activate the upper control zone and the middle stability zone ahead of schedule; (iv) When K c and C hWhen the temperature is too high, the sealing or bridging treatment of the water-resistant bearing area should be initiated in the tunnel bottom influence zone. (v) During the tunnel boring machine crossing, the limit approved by the railway property owner shall be the final control value, and 70% of it shall be used as the early warning value and 90% as the mandatory tightening control value; (vi) After the crossing is completed, continuous monitoring is carried out. If the settlement rate does not decrease sufficiently, grouting is carried out inside the tunnel through the reserved grouting holes.

[0052] Expected on-site results (expressed as normalized values): Maximum cumulative settlement / limit value decreased from 0.80–0.95 in the comparative scheme to 0.45–0.65; peak settlement rate / early warning value decreased from 1.00–1.20 to 0.40–0.70; grouting consumption per unit length decreased from 1.00 to 0.75–0.85; the proportion of abnormal telemetry rings decreased from 10%–16% to 4%–8%; the number of post-grouting times decreased from 3–5 times to 1–2 times; the residual risk in the 10 rings after crossing decreased from medium-high risk to mostly in low-risk areas.

[0053] The core of this embodiment is that once the property unit limit is determined, this method can directly map the limit to early warning, control and reinjection criteria, thus possessing immediate feasibility.

[0054] Example 4: Weight calibration and parameter values

[0055] Weighting coefficient initial value In non-critical sections, establish the baseline mean and standard deviation of each telemetry measurement using no fewer than 20 loops; in the first risk section, use a pilot loop to... A one-time calibration is performed with the grade thresholds (0.35, 0.55, 0.75); when there is historical similar engineering data, Bayesian prior can be used for updating; when there is no historical data, expert prior can be used and iterative correction can be performed on site.

[0056] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0057] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A closed-loop risk control method for shield tunneling in dense railway-supported water-rich sandy-karst coupled strata based on multi-source uncertainty fields, characterized in that, Includes the following steps: S1. Obtain borehole data, original design borehole location and measured borehole location data, geophysical data, groundwater level and pore pressure data, karst parameters, soft soil parameters, real-time tunneling parameters of the shield tunnel, and monitoring data of the surface, roadbed and tunnel structure. S2. Based on the offset relationship between the original designed borehole positions and the measured borehole positions, the missing borehole situation, the geophysical anomaly zones, and the supplementary verification detection results, a three-dimensional geological uncertainty field distributed along the shield tunnel axis is constructed. U(x,y,z) ; S3. Based on the three-dimensional stratigraphic uncertainty field U(x,y,z) The uncertainty coefficient of the formation is calculated based on the following factors: hydraulic connectivity between sand layer and karst water, stability of the cave roof, condition of weak bearing layer, anomalies in shield tunneling telemetry, and monitoring response. U Hydraulic connectivity coefficient between sand layer and karst water C h Stability coefficient of the cave roof K c , coefficient of weak bearing layer S b Shield tunneling anomaly coefficient A t and monitoring response coefficient M t The weighted sum is used to obtain the comprehensive risk index. R ; S4. Based on the comprehensive risk index R The shield tunneling impact zone is divided into at least one of the following functional zones: upper settlement control zone, middle stability zone, and lower water-resistant bearing zone, and differentiated reinforcement is implemented for the activated functional zone. S5. Based on the comprehensive risk index R Based on its changing trends, the shield tunnel face support parameters, propulsion parameters, and synchronous grouting parameters are adjusted accordingly. S6. After completing the differentiated reinforcement in S4 and the shield tunneling linkage in S5, the treatment effect is verified based on wave velocity recovery, pore pressure attenuation, grouting volume stability, and settlement rate attenuation. When the residual risk exceeds the preset threshold, re-injection or reinforcement is performed, and the process returns to S2 to reconstruct the three-dimensional stratum uncertainty field and recalculate the comprehensive risk index. R Until the residual risk reaches the preset requirements.

2. The closed-loop risk control method for shield tunneling in dense railway-supported water-rich sandy-karst coupled strata based on multi-source uncertainty fields, as described in claim 1, is characterized in that... In S2, when any measured borehole location deviates more than 2m from the original design borehole location, a displacement attenuation is applied to the ground confidence level within the control range of the measured borehole location; when the distance from the tunnel centerline projection to the nearest measured borehole location in a certain section exceeds 20m, the section is defined as a high uncertainty corridor, and it is required that 2m before the shield tunneling machine enters... D ~5 D Supplementary verification and detection will be carried out within the scope, including D The outer diameter of the tunnel boring machine.

3. The closed-loop risk control method for shield tunneling in dense railway-supported water-rich sandy-karst coupled strata based on multi-source uncertainty fields, as described in claim 1, is characterized in that... The geophysical data in S1 includes at least the micromotion inversion of the apparent shear wave velocity profile. Sections with apparent shear wave velocities greater than 300 m / s are designated as bedrock candidate areas, and low-value anomaly areas of 150 m / s to 240 m / s are designated as loose layer or karst cave anomaly candidate areas. The candidate areas are then corrected based on borehole or forward verification detection results.

4. The closed-loop risk control method for shield tunneling in dense railway-supported water-rich sandy-karst coupled strata based on multi-source uncertainty fields, as described in claim 1, is characterized in that... Calculate the formation uncertainty coefficient in S3. U Hydraulic connectivity coefficient between sand layer and karst water C h Stability coefficient of the cave roof K c , coefficient of weak bearing layer S b Shield tunneling anomaly coefficient A t and monitoring response coefficient M t The weighted sum is used to obtain the comprehensive risk index. R The specific content is as follows: in, These are the weighting coefficients. ; when R A value <0.35 is considered low risk; when 0.35 ≤ R A value <0.55 indicates a medium risk level; a value ≤0.55 indicates a medium risk level. R A value <0.75 is considered a high-risk level; when R A value ≥0.75 is considered an extremely high risk level.

5. The closed-loop risk control method for shield tunneling in dense railway-supported water-rich sandy-karst coupled strata based on multi-source uncertainty fields, as described in claim 1, is characterized in that... Based on the comprehensive risk index in S4 R The shield tunneling impact zone is divided into at least one functional zone from the following: upper settlement control zone, middle stability zone, and lower water-resistant bearing zone. The specific details of implementing differentiated reinforcement for the activated functional zones are as follows: The upper control settlement zone is located 0.3 meters above the tunnel arch. D ~0.8 D Within the range, and extending 1.5 meters forward along the line. D ~3 D Extend backwards by 0.5 D ~1.5 D， in D The outer diameter of the tunnel boring machine; The intermediate stability region is located 0.2 meters outside the tunnel outline. D ~0.6 D Within the circumferential range, D It is the outer diameter of the shield, and at least covers the gap behind the shield tail wall; The lower aquitard bearing zone is located within the influence zone between the tunnel floor and the aquitard, rock surface, or roof of a high-risk karst cave; when the aquitard thickness is greater than 3m and C h When the water level is below the preset threshold, the treatment of the lower water-resistant bearing area will not be initiated.

6. The closed-loop risk control method for shield tunneling in dense railway water-rich sandy karst coupled strata based on multi-source uncertainty field as described in claim 5, is characterized in that... The upper settling zone uses a low-disturbance, micro-expansion slurry with a funnel viscosity of 35s to 55s, a bleeding rate of no more than 5%, a 7-day uniaxial compressive strength of 0.5MPa to 2.0MPa, and a volume expansion rate of 0.2% to 1.0%. The medium-stable contour zone uses a stable filling grout material with an initial setting time of 15 min to 60 min, a water bleeding rate of no more than 3%, and a 28-day uniaxial compressive strength of 2 MPa to 5 MPa. The lower impermeable bearing zone shall be constructed with at least a sealing grout and a reinforcing grout in sequence, wherein the permeability coefficient of the solidified sealing grout shall not exceed 1×10⁻⁶. -7 m / s, the 7-day uniaxial compressive strength of the skeleton slurry is 3MPa~8MPa.

7. The closed-loop risk control method for shield tunneling in dense railway-supported water-rich sandy-karst coupled strata based on multi-source uncertainty fields, as described in claim 1, is characterized in that... Based on the comprehensive risk index in S5 R The specific details regarding the adjustment of shield tunnel face support parameters, propulsion parameters, and synchronous grouting parameters, along with their changing trends, are as follows: When the tunnel boring machine is an earth pressure balance shield, the linkage adjustment variables include earth chamber pressure, screw speed, propulsion speed, total thrust, cutterhead torque, amendment dosage, synchronous grouting pressure, and synchronous grouting volume. When the tunnel boring machine is a slurry balance tunnel boring machine, the linkage adjustment variables include chamber pressure, slurry density, slurry viscosity, circulation flow rate, synchronous grouting pressure, and synchronous grouting volume. when R Increase or A t In case of an anomaly, the system automatically implements a series of coordinated controls, including reducing the advance speed, increasing the support pressure safety factor, improving the real-time filling coefficient of synchronous grouting, and shortening the risk verification cycle.

8. The closed-loop risk control method for shield tunneling in dense railway-supported water-rich sandy-karst coupled strata based on multi-source uncertainty fields, as described in claim 1, is characterized in that... The following treatment logic is adopted for the geometric-hydraulic dual threshold: when K c low and C h When the level is low, only enhanced monitoring is activated; when K c low and C h When the temperature is high, activate the sealing mode of the lower water-resistant bearing area; when K c High and C h When the threshold is low, initiate bridging or fill mode; when K c High and C h When the temperature is high, a combination of blocking, bridging, and filling modes is activated.

9. The closed-loop risk control method for shield tunneling in dense railway-supported water-rich sandy-karst coupled strata based on multi-source uncertainty fields, as described in claim 1, is characterized in that... In S6, after completing the differentiated reinforcement of S4 and the shield tunneling linkage of S5, the treatment effect is verified based on wave velocity recovery, pore pressure attenuation, grouting volume stability, and settlement rate attenuation. When the residual risk is higher than the preset threshold, the specific content of re-grouting or reinforcement is as follows: When verifying the treatment effect of weak bearing stratum sections, post-grouting holes are reserved along the circumferential direction of the risk section segments. The post-grouting holes are arranged at least at the corresponding positions of the arch shoulder, sidewall, or tunnel bottom. When the settlement rate decreases, the pore pressure decreases, or the residual risk index does not meet the preset requirements after treatment, grouting is carried out in the tunnel through the post-grouting holes.

10. The closed-loop risk control method for shield tunneling in dense railway-supported water-rich sandy karst coupled strata based on multi-source uncertainty fields, as described in claim 1, is characterized in that... The following are the steps in S6 to determine whether the residual risk meets the preset requirements: Apparent transverse wave velocity Vs Recovery from low-value anomaly areas to bedrock candidate thresholds; The pressure drop of the pore pressure falls below the acceptance threshold. Two consecutive reinjections or subsequent grouting volumes falling below the acceptance threshold and no longer increasing; The settlement rate of the ground surface and roadbed decreased to below 0.1 mm / d; Posterior composite risk index R It has been downgraded by one or more levels compared to the previous one.

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