Deformation failure mode identification method and system for constructing hybrid rock zone tunnel engineering section

Abstract

The invention discloses a deformation failure mode identification method and system for constructing a hybrid rock zone tunnel engineering section. The constructed hybrid rock zone has the characteristics of complex material composition and geological structure and the like, and becomes a complex engineering geological problem and a frequent geological disaster zone faced by tunnel and underground engineering construction. The method comprises the steps that surrounding rock geologic structure types for constructing the hybrid rock zone tunnel are divided; determining five deformation and failure modes of the tunnel section, and establishing a corresponding relationship between each deformation and failure mode and the surrounding rock geological structure type and the auxiliary identification factor; and obtaining tunnel surrounding rock geological information, and according to the established corresponding relation between the deformation and failure mode and the surrounding rock geological structure type as well as the auxiliary identification factor, identifying the deformation and failure mode of the section to be excavated of the tunnel engineering of the constructed hybrid rock zone. According to the method, the geological safety risk in the tunnel construction process of the structural hybrid rock zone can be prevented and solved.

Description

Technical Field

[0002] This invention belongs to the field of tunnel and underground engineering safety control technology, specifically relating to a method and system for identifying deformation and failure modes of tunnel sections in structural mixed rock zones. Background Technology

[0003] Tectonic mélange zones are characterized by complex material composition and geological structure, rapid spatial variation, and significant differences in engineering geological properties, making them a region prone to complex engineering geological problems and frequent geological hazards in tunnel and underground engineering construction. In summary, tectonic mélange zones are characterized by intense tectonic deformation, diverse lithologies, severe local alteration, and well-developed active faults, specifically manifested as follows: 1) Severe tectonic deformation: folds and faults are well-developed, and rock masses of different types and origins are mixed and deposited.

[0004] 2) Diverse lithologies: Sedimentary blocks, metamorphic blocks, and igneous blocks are all developed, and they are metamorphosed and deformed by tectonic and hydrothermal factors, resulting in a large number of different types of lithologies in the matrix.

[0005] 3) Severe local alteration: destruction of the original rock structure, superposition of multiple types of alteration and tectonic modification characteristics (foliation, mylonitization), reflecting the long-term superposition of hydrothermal activity and stress in the tectonic fracture zone.

[0006] 4) Development of active faults: Multiple Holocene active fault zones are often developed along the tectonic mélange belt.

[0007] Due to the weakness of previous geological work, the understanding of the formation and evolution process and adverse engineering characteristics of tectonic mélange zones is low, and existing theories and technical methods are difficult to meet the needs of engineering construction, which has become an urgent problem to be solved. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, this invention provides a method and system for identifying the deformation and failure modes of tunnel sections in mixed rock zones. By establishing the correspondence between the deformation and failure modes and the geological structure type of the surrounding rock and auxiliary identification factors, the deformation and failure modes of the section to be excavated can be quickly identified.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for identifying the deformation and failure modes of tunnel sections in mixed rock zones includes the following steps: Step 1: Classify the surrounding rock geological structure types of the tunnel in the structural mélange zone. The surrounding rock geological structure types include: I. Matrix-supported type, II. Rock block-supported type, III. Fault-controlled type, and IV. Joint-dense type. The I. Matrix-supported type includes I-1 No rock block matrix support type and I-2 Rock block matrix support type. The II. Rock block-supported type includes II-1 Locally altered rock block support type and II-2 Fault-controlled alteration zone rock block support type. The III. Fault-controlled type includes III-1 Fracture zone developed fault control type, III-2 Micro-fracture control type, and III-3 Active fault / landslide surface fault control type. Step 2: Determine the five deformation and failure modes of the tunnel cross section, and establish the correspondence between each deformation and failure mode and the geological structure type of the surrounding rock and auxiliary identification factors; Step 3: Obtain geological information of the surrounding rock of the tunnel. Based on the correspondence between the deformation and failure modes established in Step 2 and the geological structure type and auxiliary identification factors of the surrounding rock, identify the deformation and failure modes of the sections to be excavated in the tunnel section of the tectonic mixed rock zone.

[0010] Furthermore, in step one, the method for determining matrix-supported type I is as follows: When the tunnel cross-section is mainly composed of matrix and the long side of a single rock block cannot cover the entire diameter of the tunnel cross-section, this type of cross-section is classified as type I matrix-supported. Based on the proportion of rock block area, when the proportion of rock block area is <20%, it is type I-1 without rock block matrix support; when the proportion of rock block area is ≥20%, it is type I-2 with rock block matrix support.

[0011] Furthermore, in step one, the method for determining the support type of rock block II is as follows: When the tunnel cross-section is mainly composed of rock blocks, and the long side of a single rock block can cover the entire diameter of the tunnel cross-section, this type of cross-section is classified as type II rock block support. When the alteration zone is distributed sporadically or in local patches and does not form a continuous tectonic zone, it is type II-1 local alteration rock block support. When the alteration zone develops along the fault tectonic zone and forms a continuous alteration fracture zone, it is type II-2 fault-controlled alteration zone rock block support.

[0012] Furthermore, in step one, the method for determining fracture control type III is as follows: When the width of the fault fracture zone in the tunnel cross section is ≥1m, the area of ​​the fault fracture zone is >30% of the tunnel cross section area, and the rock particle size is <5cm, it is classified as III-1, a fault-controlled type with fracture zone development; when the tunnel cross section only has linear small fractures with a fracture width ≤1m, it is classified as III-2, a minor fracture-controlled type; when the tunnel cross section has active fractures or landslide sliding surfaces, it is classified as III-3, an active fracture / landslide surface fracture-controlled type.

[0013] Furthermore, in step one, the method for determining the density of joint type IV is as follows: When the joint line density of the tunnel cross section is ≥10 lines / m and is concentrated in a belt, it is classified as type IV, which is characterized by dense joints.

[0014] Furthermore, in step two, the five deformation and failure modes of the tunnel cross section are collapse, horizontal convergence, circumferential convergence, bottom heave, and faulting; collapse manifests as the falling, sinking, sliding, or rotation of rock blocks at the arch crown and abutment; horizontal convergence manifests as horizontal extrusion deformation; circumferential convergence manifests as synchronous deformation of the entire cross section; bottom heave manifests as the bulging of the inverted arch; and faulting manifests as the displacement of the tunnel structure.

[0015] Furthermore, in step two, the correspondence between each deformation and failure mode and the surrounding rock geological structure type and auxiliary identification factors is as follows: 1) I-1 type without rock block matrix support When there is no groundwater or a small amount of groundwater and the ground stress is high, the corresponding deformation and failure mode is horizontal convergence; when groundwater is abundant, the corresponding deformation and failure mode is bottom heave or collapse; when the burial depth is <300m and the ground stress is low, the corresponding deformation and failure mode is collapse. 2) I-2 type with rock mass matrix support When groundwater is abundant, the corresponding deformation and failure mode is bottom heave or local collapse; when rock blocks are concentrated, the corresponding deformation and failure mode is collapse. 3) II-1 Locally altered rock block support type When the alteration zone is located at the top of the arch, the corresponding deformation and failure mode is collapse; when the blasting vibration velocity is ≥10cm / s, the corresponding deformation and failure mode is alteration zone fracture and collapse. 4) Block-supported type of alteration zone controlled by fault II-2 When there is high ground stress, the corresponding deformation and failure mode is horizontal convergence of the alteration zone; when there is abundant groundwater and the alteration zone softens, the corresponding deformation and failure mode is collapse. 5) III-1 fracture zone development, fault-controlled type When the burial depth is less than 100m, the corresponding deformation and failure mode is circumferential convergence; when the burial depth is greater than or equal to 100m, the corresponding deformation and failure mode is horizontal convergence; when groundwater is abundant, the corresponding deformation and failure mode is bottom heave or water inrush type collapse. 6) III-2 Microfracture Control Type When the fracture strike is parallel to the tunnel axis, the corresponding deformation and failure mode is horizontal convergence; when the fracture strike is perpendicular to the tunnel axis, the corresponding deformation and failure mode is collapse; when there is high ground stress, the corresponding deformation and failure mode is horizontal convergence. 7) III-3 Active Fault / Landslide Surface Fault Control Type When there is strong active faulting, the corresponding deformation and failure mode is faulting; when there is weak active faulting, the corresponding deformation and failure mode is collapse; when the landslide body is creeping, the corresponding deformation and failure mode is faulting. 8) IV Joint-dense type When the burial depth is less than 100m, the corresponding deformation and failure mode is circumferential convergence; when the burial depth is greater than or equal to 100m, the corresponding deformation and failure mode is collapse; when it is a horizontal joint, the corresponding deformation and failure mode is crown collapse; when it is a steeply dipping joint, the corresponding deformation and failure mode is sidewall convergence.

[0016] Furthermore, step three specifically includes the following steps: Step 3.1: Obtain tunnel geological information; Step 3.2: Based on the geological information obtained in Step 3.1, determine the geological structure type of the surrounding rock; Step 3.3: Extract auxiliary identification factor data; Step 3.4: Based on the geological structure type of the surrounding rock determined in Step 3.2, the auxiliary identification factor data extracted in Step 3.3, the correspondence between the deformation and failure mode and the geological structure type of the surrounding rock and the auxiliary identification factor, determine the deformation and failure mode of the tunnel section. Step 3.5: Verify the rationality of the identification results using real-time data from tunnel monitoring measurements and fiber optic grating monitoring.

[0017] Furthermore, step 3.3 specifically refers to: From the monitoring results in step 3.1, quantitative data on groundwater status, geostress level, construction disturbance intensity, joint orientation, and fault activity are extracted. The specific grading standards are as follows: Groundwater status: Based on the per unit length inflow rate Q, it is divided into three categories: 1) No water: Q < 25 L / (min·10 m); p ≤ 0.1 MPa; 2) Small amount of groundwater: 25 L / (min·10 m) ≤ Q < 125 L / (min·10 m); 0.1 MPa < p ≤ 0.5 MPa; 3) Abundant groundwater: Q ≥ 125 L / (min·10 m); p > 0.5 MPa; Ground stress levels are classified according to the strength-stress ratio Rc / σmax and ground stress σmax: 1) Low ground stress: Rc / σmax>7; σmax<15MPa; 2) Medium ground stress: 4<Rc / σmax≤7, 15MPa≤σmax<30MPa; 3) High ground stress: Rc / σmax≤4, σmax≥30MPa; Construction disturbance intensity: Based on the comprehensive index of displacement evaluation SR and blasting vibration velocity, it is divided into 1) low disturbance: SR < 0.3; blasting vibration velocity < 5 cm / s; 2) medium disturbance: 0.3 ≤ SR < 0.7, 5 cm / s ≤ blasting vibration velocity < 10 cm / s; 3) high disturbance: SR ≥ 0.7; blasting vibration velocity ≥ 10 cm / s; Joint attitude: Based on the joint dip angle α1, it is divided into 1) horizontal joints: α1≤30°; 2) gently dipping joints: 30°<α1<60°; 3) steeply dipping joints: α1≥60°; Fracture activity: 1) Stable fracture: annual sliding rate < 0.1 mm / year; fracture width ≤ 1 m; 2) Weakly active fracture: 0.1 mm / year ≤ annual sliding rate < 1 mm / year; 1 m < fracture width < 5 m; 3) Strongly active fracture: annual sliding rate ≥ 1 mm / year; fracture width ≥ 5 m.

[0018] A deformation and failure mode identification system for tunnel sections in mixed rock zones includes a data acquisition module, a deformation and failure mode determination module, and an early warning module. The data acquisition module is used to acquire geological information of the surrounding rock of the tunnel. The deformation and failure mode determination module is used to identify the deformation and failure mode of the section to be excavated in the tunnel engineering section of the structural mixed rock zone. The early warning module is used to notify the construction party of the determined deformation and failure mode.

[0019] The beneficial effects of this invention are: 1) By establishing the correspondence between deformation and failure modes and the geological structure type of the surrounding rock and auxiliary identification factors, this invention can quickly identify the deformation and failure modes of the section to be excavated, prevent and resolve the geological safety risks faced during the construction of tunnels in tectonic mixed rock zones, and effectively support the construction of tunnels and underground engineering projects. 2) The judgment of the geological structure type of the surrounding rock in this invention has clear quantitative classification standards (such as the area ratio of rock blocks and the width of fractures), avoiding subjective judgment errors and laying an accurate foundation for deformation mode correlation. 3) This invention combines five typical deformation and failure modes of mixed rock tunnels and introduces quantitative auxiliary identification factors such as groundwater and geostress to construct a multi-dimensional correspondence between "surrounding rock type - deformation mode - auxiliary factors" to improve the accuracy of identification; 4) This invention integrates multiple technologies such as advanced geological forecasting and fiber optic grating monitoring to form a closed-loop process of "data acquisition - type determination - factor extraction - pattern locking - real-time verification". It is highly operable and adaptable to the characteristics of varied geological conditions in tectonic mixed rock belts. Attached Figure Description

[0020] Figure 1 This invention provides a process for identifying deformation and failure modes in structural mixed rock tunnels. Figure 2 This invention relates to the type of surrounding rock cross-section for constructing mixed rock tunnels. Detailed Implementation

[0021] The present invention will now be described in detail with reference to specific embodiments.

[0022] This invention establishes a correspondence between deformation and failure modes and the geological structure type of the surrounding rock and auxiliary identification factors, which can quickly identify the deformation and failure modes of the section to be excavated, prevent and resolve geological safety risks encountered during the construction of tunnels in tectonic mixed rock zones, and effectively support the construction of tunnels and underground engineering projects.

[0023] like Figure 1 As shown, the method for identifying the deformation and failure modes of tunnel sections in mixed rock zones according to the present invention specifically includes the following steps: Step 1: As Figure 2 As shown, based on the structure / texture, lithological composition, and mechanical properties of tunnels in tectonic mélange zones, the surrounding rock geological structure types are classified as follows: I. Matrix-supported type, II. Block-supported type, III. Fault-controlled type, and IV. Joint-dense type. I. Matrix-supported type includes I-1 matrix-supported type without blocks and I-2 matrix-supported type with blocks. II. Block-supported type includes II-1 locally altered block-supported type and II-2 fault-controlled alteration zone block-supported type. III. Fault-controlled type includes III-1 fracture zone-developed fault-controlled type, III-2 micro-fracture-controlled type, and III-3 active fault / landslide surface fault-controlled type. 1) Matrix-supported type When the tunnel cross-section is dominated by a matrix with weak rock mechanical properties, and the long side of a single rock block cannot cover the entire diameter of the tunnel cross-section, the rock block cannot provide effective rigid support for the tunnel cross-section. This type of cross-section is classified as type I, matrix-supported. Based on the proportion of rock block area, when the proportion of rock block area is <20%, the cross-section is almost completely filled by the matrix, resulting in extremely poor mechanical stability and susceptibility to overall deformation due to stress and groundwater, it is classified as type I-1, without matrix support. When the proportion of rock block area is ≥20%, the rock blocks are dispersed in the matrix, providing limited local support, but the overall stability is still controlled by the matrix, which is classified as type I-2, with matrix support.

[0024] Engineering characteristics: The substrate is prone to softening when exposed to water, has low strength (saturated uniaxial compressive strength is usually <10MPa), and is prone to plastic deformation under stress. It is a type of foundation that is prone to horizontal convergence, bottom heave and collapse.

[0025] 2) II Rock Block Support Type The tunnel cross-section is mainly composed of rock blocks with strong rock mechanical characteristics. When the long side of a single rock block can cover the entire diameter of the tunnel cross-section, the rock block can form the main rigid support for the tunnel cross-section. This type of cross-section is classified as type II rock block support. When the alteration zone is distributed sporadically or in local patches and does not form a continuous structural zone, and the rock mass integrity index is >0.6, the overall integrity of the rock block is relatively good, which is type II-1 local alteration rock block support. When the alteration zone develops along the fault structural zone and forms a continuous alteration fracture zone, and the rock mass integrity index is <0.4, the integrity of the rock block is severely affected by the fault, which is type II-2 fault-controlled alteration zone rock block support.

[0026] Engineering characteristics: Overall stability is better than matrix-supported type, but the alteration zone and fault area are weak points for deformation, which are prone to local collapse or convergence deformation due to construction disturbance.

[0027] 3) Type III Fracture Control The tunnel cross-section is dominated and controlled by the fracture structure, and the deformation and failure mode is directly related to the degree of development and activity of the fracture. When the width of the fault fracture zone in the tunnel cross-section is ≥1m, the area of ​​the fault fracture zone is >30% of the tunnel cross-section area, and the rock block size is mostly <5cm, the rock mass is highly fragmented and poorly cemented, which is classified as the III-1 fracture zone development and fault-controlled type. When only small linear fractures with a fracture width ≤1m are developed in the tunnel cross-section, the overall lithology is relatively uniform, and the fractures have a limited effect on the segmentation of the cross-section, which is classified as the III-2 micro-fracture-controlled type. When Holocene active faults or landslide sliding surfaces are developed in the tunnel cross-section, there is a significant risk of dynamic deformation (the annual sliding rate may be ≥0.1mm), which is classified as the III-3 active fault / landslide surface fracture-controlled type. Engineering characteristics: The fault zone is a stress concentration area and a groundwater channel, which can easily cause deformations such as collapse, horizontal convergence, and faulting. Among them, faulting caused by active faults / landslide surfaces is highly destructive.

[0028] 4) N4 Joint-dense type The high degree of joint development significantly damages the integrity of the rock mass, forming dense joint zones; When the joint line density of the tunnel cross section is ≥10 joints / m (or the joint spacing is ≤10cm) and is concentrated in a belt (the width of the dense belt is ≥1m), or accompanied by rock mass fracturing (rock mass integrity index <0.5) and abnormal sound waves (sound wave velocity is more than 30% lower than that of intact rock mass of the same lithology), it is classified as type IV joint density.

[0029] Engineering characteristics: The rock mass is cut into fragments by joints, has poor integrity, and is susceptible to collapse or convergence deformation due to gravity, stress and groundwater.

[0030] Step 2: Based on the structural deformation theory of mélange tunnels and combined with deformation data of typical mélange tunnels at home and abroad, five deformation and failure modes of tunnel cross sections are determined: collapse, horizontal convergence, circumferential convergence, bottom heave, and faulting; and the correspondence between each deformation and failure mode and the geological structure type of the surrounding rock and auxiliary identification factors is established. The five deformation and failure modes of the tunnel cross section are as follows: Due to construction disturbances, collapses manifest as the falling, sinking, sliding, or rotation of rock blocks at the arch crown and abutments; they are characterized by being short-lived, sudden, and controllable with support. Timely support (such as pre-anchor bolts + shotcrete) can prevent continuous deformation. Horizontal convergence manifests as horizontal extrusion deformation; soft rock in the surrounding rock, under high ground stress conditions at a depth ≥300m, undergoes slow but significant horizontal extrusion deformation, intruding into the tunnel clearance, increasing the overall volume of the surrounding rock, and in severe cases, the arch waist protrudes significantly; this is a plastic failure, lasting from several hours to several months. Circumferential convergence manifests as the settlement of the tunnel arch crown approaching or reaching the horizontal convergence amount, affecting the entire cross-section; brittle and shear failure induced by shallow burial (<100m) compressive stress, accompanied by... Deformation is caused by discontinuities in the rock mass and gravity-controlled destruction; deformation is continuous, but shorter in duration than horizontal convergence, with the entire cross-section deforming synchronously; bottom heave manifests as an inverted arch uplift, caused by water-rock physicochemical reactions (hydrophilic minerals absorbing water and expanding), which leads to the expansion of the rock mass volume over time, resulting in the inverted arch of the tunnel encroaching on the clearance; it often occurs in expansive surrounding rocks containing kaolinite and montmorillonite, and usually appears several years after the tunnel has been in operation; faulting manifests as tunnel structural displacement, mainly occurring in tunnels crossing active faults and landslides; it is divided into direct faulting caused by rapid sliding of earthquakes / landslides, and rock mass fracture-type faulting caused by pre-earthquake fault creep and slow landslide activity; it is sudden and highly destructive, and engineering measures are difficult to completely protect against.

[0031] The correspondence between each deformation and failure mode and the surrounding rock geological structure type and auxiliary identification factors is shown in Table 1 below: Step 3: Obtain geological information of the surrounding rock of the tunnel. Based on the correspondence between the deformation and failure modes established in Step 2 and the geological structure type and auxiliary identification factors of the surrounding rock, identify the deformation and failure modes of the section to be excavated in the tunnel section of the tectonic mixed rock zone. Step 3 specifically includes the following steps: Step 3.1: Obtain tunnel geological information; employ a combination of various monitoring and detection methods to comprehensively acquire key information such as the structure / texture, lithology, groundwater, and in-situ stress of the tunnel surrounding rock. The technical means and application scenarios are as follows: Advanced geological prediction: including TSP (Tunnel Seismic Wave Detection), transient electromagnetic method, and ground-penetrating radar method; to obtain lithological distribution, location and scale of fractures / joints, and groundwater-rich areas; applicable to all high-risk tunnels, serving as a basic detection method; Advanced drilling: including deepening boreholes (5-8m deep) and advanced horizontal drilling (≥30m deep); targeted exposure of groundwater bodies, the width of fracture zones, and cementation status; suitable for sections with abundant groundwater or well-developed fractures; Working face sketching and observation: Record the lithological composition, rock block size and distribution (photographs + sketch annotations), joint density and attitude (total station measurement), fracture traces, groundwater seepage points and flow rate (measured with graduated cylinder); obtain the current geological features of the cross-section in real time; Tunnel monitoring and measurement: Deploy convergence meters (to monitor convergence around the tunnel) and settlement meters (to monitor crown settlement); record deformation rate and cumulative displacement; predict deformation trends in the section to be excavated; Hydrogeological monitoring: Deploying water level gauges (to monitor groundwater levels) and piezometers (to monitor fissure water pressure); assessing the impact of groundwater on the stability of surrounding rock; applicable to areas with abundant groundwater; In-situ stress testing or long-term monitoring: using hydraulic fracturing method (measured in-situ stress magnitude) and stress relief method (measured in-situ stress direction); applicable to burial depth ≥300m or soft rock sections with large deformation; Fiber Bragg grating monitoring: Utilizing the deformation sensitivity of fiber Bragg gratings, it monitors the stress and strain of tunnel sidewalls and arches; accurately identifies structural / tectonic continuity and lithological abrupt changes; suitable for complex structural / tectonic structures and lithological sections.

[0032] Step 3.2: Based on the geological information obtained in Step 3.1, determine the geological structure type of the surrounding rock; Step 3.3: Extract auxiliary identification factor data; specifically: From the monitoring results in step 3.1, quantitative data on groundwater status, geostress level, construction disturbance intensity, joint orientation, and fracture activity are extracted. Combined with industry standards such as the "Railway Tunnel Design Code" and the "Highway Tunnel Construction Technical Code," as well as statistical data from tunnel engineering cases, the following quantitative grading standards are formulated for core auxiliary identification factors such as groundwater status, geostress level, and construction disturbance intensity. These standards provide operable indicators for accurate identification of deformation modes. Specific grading standards, engineering characteristics, and testing methods are shown in Tables 2, 3, 4, 5, and 6. Table 2 Quantitative Classification Standards for Groundwater Status Table 3 Quantitative Classification Standards for Geostress Levels Table 4 Quantitative Grading Standards for Construction Disturbance Intensity Table 5. Quantitative Grading Standards for Joint Occurrence and Developmental Characteristics Table 6. Quantitative Grading Standards for Fracture Activity Step 3.4: Based on the geological structure type of the surrounding rock determined in Step 3.2, the auxiliary identification factor data extracted in Step 3.3, and the correspondence between the deformation and failure modes and the geological structure type of the surrounding rock and the auxiliary identification factors (Table 1), determine the deformation and failure modes of the tunnel section. Step 3.5: Use real-time data from tunnel monitoring and fiber optic grating monitoring (such as whether the deformation rate matches the identification mode characteristics) to verify the rationality of the identification results; if the monitoring data shows that the deformation trend does not match the identification results (such as the prediction is a bottom bulge, but the actual deformation rate matches the horizontal convergence characteristics), readjust the weights of the auxiliary identification factors and correct the identification conclusion.

[0033] The present invention also provides a deformation and failure mode identification system for tunnel sections in structural mélange zones, comprising a data acquisition module, a deformation and failure mode determination module, and an early warning module; the data acquisition module is used to acquire geological information of the surrounding rock of the tunnel; the deformation and failure mode determination module is used to identify the deformation and failure mode of the section to be excavated in the tunnel section in structural mélange zones; and the early warning module is used to notify the construction party of the determined deformation and failure mode.

[0034] The specific implementation method is as follows: Taking a structurally complex rock tunnel project of the XX Railway as an example, the application process of this invention is explained: (I) Project Background The tunnel traverses a structurally mixed rock zone, is 2.8 km long, has a maximum burial depth of 450 m, and a designed cross-sectional diameter of 6 m. During construction, it is necessary to identify the deformation and failure modes of the sections to be excavated.

[0035] (II) Implementation Steps S1: Determine the geological structure type of the surrounding rock Advanced geological prediction (TSP + ground-penetrating radar) shows that the section to be excavated is mainly composed of argillaceous soft rock (matrix), with the long side of the rock block being about 3m (<6m, which cannot cover the cross-sectional diameter), and the area ratio of the rock block being about 30% (≥20%). Sketch and observation of the working face: The rock blocks are unevenly distributed, locally concentrated, with no obvious fractures, and the joint density is 5 joints / m (<10 joints / m). Judgment result: I-2 rock block support (matrix support type).

[0036] S2: Preliminary screening of possible deformation modes Based on the "type-mode" correspondence, the possible deformation modes corresponding to the I-2 rock block support type are collapse and bottom heave.

[0037] S3: Extract auxiliary identification factors and accurately identify. Hydrogeological monitoring: Water inflow per unit length Q = 130 L / (min・10 m), fissure water pressure p = 0.6 MPa (Table 1, indicating abundant groundwater). Ground stress test: maximum ground stress σmax = 22MPa, strength stress ratio Rc / σmax = 5.5 (Table 2, determined to be medium ground stress). Fiber optic grating monitoring: The stress and strain of the invert arch showed a slow increasing trend (consistent with the early stage of bottom heave), and the deformation rate of the sidewalls was stable (no signs of collapse). Conclusion: The deformation and failure mode of the section to be excavated is bottom heave, with a secondary risk of local collapse.

[0038] Engineering application results: Targeted measures: advance reinforcement of the invert arch (Φ42 anchor bolts, 4m in length), groundwater drainage (advance drilling of the invert arch, 100mm in diameter, 10m in depth), and local advance support (Φ25 hollow grouting anchor bolts, 5m in length). Results: The maximum uplift of the invert arch after construction was less than 5cm, and no collapse occurred. Compared with the traditional support scheme, the cost was reduced by 30% and the construction efficiency was increased by 20%.

[0039] The content of this invention is not limited to the embodiments listed. Any equivalent modifications made by those skilled in the art to the technical solutions of this invention by reading this specification are covered by the claims of this invention.

Claims

1. A method for identifying the deformation and failure modes of tunnel sections in mixed rock zones, characterized in that: Includes the following steps: Step 1: Classify the surrounding rock geological structure types of the tunnel in the structural mélange zone. The surrounding rock geological structure types include: I. Matrix-supported type, II. Rock block-supported type, III. Fault-controlled type, and IV. Joint-dense type. The I. Matrix-supported type includes I-1 No rock block matrix support type and I-2 Rock block matrix support type. The II. Rock block-supported type includes II-1 Locally altered rock block support type and II-2 Fault-controlled alteration zone rock block support type. The III. Fault-controlled type includes III-1 Fracture zone developed fault control type, III-2 Micro-fracture control type, and III-3 Active fault / landslide surface fault control type. Step 2: Determine the five deformation and failure modes of the tunnel cross section, and establish the correspondence between each deformation and failure mode and the geological structure type of the surrounding rock and auxiliary identification factors; Step 3: Obtain geological information of the surrounding rock of the tunnel. Based on the correspondence between the deformation and failure modes established in Step 2 and the geological structure type and auxiliary identification factors of the surrounding rock, identify the deformation and failure modes of the sections to be excavated in the tunnel section of the tectonic mixed rock zone.

2. The method for identifying the deformation and failure modes of tunnel sections in structural mixed rock zones according to claim 1, characterized in that: In step one, the method for determining matrix-supported type I is as follows: When the tunnel cross-section is mainly composed of matrix and the long side of a single rock block cannot cover the entire diameter of the tunnel cross-section, this type of cross-section is classified as type I matrix-supported. Based on the proportion of rock block area, when the proportion of rock block area is <20%, it is type I-1 without rock block matrix support; when the proportion of rock block area is ≥20%, it is type I-2 with rock block matrix support.

3. The method for identifying the deformation and failure modes of tunnel sections in structural mixed rock zones according to claim 1, characterized in that: In step one, the method for determining the support type of rock block II is as follows: When the tunnel cross-section is mainly composed of rock blocks, and the long side of a single rock block can cover the entire diameter of the tunnel cross-section, this type of cross-section is classified as type II rock block support. When the alteration zone is distributed sporadically or in local patches and does not form a continuous tectonic zone, it is type II-1 local alteration rock block support. When the alteration zone develops along the fault tectonic zone and forms a continuous alteration fracture zone, it is type II-2 fault-controlled alteration zone rock block support.

4. The method for identifying the deformation and failure modes of tunnel sections in structural mixed rock zones according to claim 1, characterized in that: In step one, the method for determining fracture control type III is as follows: When the width of the fault fracture zone in the tunnel cross section is ≥1m, the area of ​​the fault fracture zone is >30% of the tunnel cross section area, and the rock particle size is <5cm, it is classified as III-1 fracture zone development and fault control type; when the tunnel cross section only develops linear small fractures with a fracture width ≤1m, it is classified as III-2 micro fracture control type; when the tunnel cross section develops active fractures or landslide sliding surfaces, it is classified as III-3 active fracture / landslide surface fracture control type.

5. The method for identifying the deformation and failure modes of tunnel sections in structural mixed rock zones according to claim 1, characterized in that: In step one, the method for determining the density of joint type IV is as follows: When the joint line density of the tunnel cross section is ≥10 lines / m and is concentrated in a belt, it is classified as type IV, which is characterized by dense joints.

6. The method for identifying the deformation and failure modes of tunnel sections in structurally mixed rock zones according to any one of claims 1-5, characterized in that: In step two, the five deformation and failure modes of the tunnel cross section are collapse, horizontal convergence, circumferential convergence, bottom heave, and faulting. Collapse is manifested as the falling, sinking, sliding, or rotation of rock blocks at the arch crown and abutment. Horizontal convergence is manifested as horizontal extrusion deformation. Circumferential convergence is manifested as synchronous deformation of the entire cross section. Bottom heave is manifested as the bulging of the inverted arch. Faulting is manifested as the displacement of the tunnel structure.

7. The method for identifying the deformation and failure modes of tunnel sections in structural mixed rock zones according to claim 6, characterized in that: In step two, the correspondence between each deformation and failure mode and the surrounding rock geological structure type and auxiliary identification factors is as follows: 1) I-1 type without rock block matrix support When there is no groundwater or a small amount of groundwater and the ground stress is high, the corresponding deformation and failure mode is horizontal convergence; when groundwater is abundant, the corresponding deformation and failure mode is bottom heave or collapse; when the burial depth is <300m and the ground stress is low, the corresponding deformation and failure mode is collapse. 2) I-2 type with rock matrix support When groundwater is abundant, the corresponding deformation and failure mode is bottom heave or local collapse; when rock blocks are concentrated, the corresponding deformation and failure mode is collapse. 3) II-1 Locally altered rock block support type When the alteration zone is located at the top of the arch, the corresponding deformation and failure mode is collapse; when the blasting vibration velocity is ≥10cm / s, the corresponding deformation and failure mode is alteration zone fracture and collapse. 4) Block-supported type of alteration zone controlled by fault II-2 When there is high ground stress, the corresponding deformation and failure mode is horizontal convergence of the alteration zone; when there is abundant groundwater and the alteration zone softens, the corresponding deformation and failure mode is collapse. 5) III-1 fracture zone development, fault-controlled type When the burial depth is less than 100m, the corresponding deformation and failure mode is circumferential convergence; when the burial depth is greater than or equal to 100m, the corresponding deformation and failure mode is horizontal convergence; when groundwater is abundant, the corresponding deformation and failure mode is bottom heave or water inrush type collapse. 6) Ⅲ-2 Microfracture Control Type When the fracture strike is parallel to the tunnel axis, the corresponding deformation and failure mode is horizontal convergence; when the fracture strike is perpendicular to the tunnel axis, the corresponding deformation and failure mode is collapse; when there is high ground stress, the corresponding deformation and failure mode is horizontal convergence. 7) III-3 Active Fault / Landslide Surface Fault Control Type When there is strong active faulting, the corresponding deformation and failure mode is faulting; when there is weak active faulting, the corresponding deformation and failure mode is collapse; when the landslide body is creeping, the corresponding deformation and failure mode is faulting. 8) IV Joint-dense type When the burial depth is less than 100m, the corresponding deformation and failure mode is circumferential convergence; when the burial depth is greater than or equal to 100m, the corresponding deformation and failure mode is collapse; when it is a horizontal joint, the corresponding deformation and failure mode is crown collapse; when it is a steeply dipping joint, the corresponding deformation and failure mode is sidewall convergence.

8. The method for identifying the deformation and failure modes of tunnel sections in structural mixed rock zones according to claim 7, characterized in that: Step three specifically includes the following steps: Step 3.1: Obtain tunnel geological information; Step 3.2: Based on the geological information obtained in Step 3.1, determine the geological structure type of the surrounding rock; Step 3.3: Extract auxiliary identification factor data; Step 3.4: Based on the geological structure type of the surrounding rock determined in Step 3.2, the auxiliary identification factor data extracted in Step 3.3, the correspondence between the deformation and failure mode and the geological structure type of the surrounding rock and the auxiliary identification factor, determine the deformation and failure mode of the tunnel section. Step 3.5: Verify the rationality of the identification results using real-time data from tunnel monitoring measurements and fiber optic grating monitoring.

9. The method for identifying the deformation and failure modes of tunnel sections in structural mixed rock zones according to claim 8, characterized in that: Step 3.3 specifically refers to: From the monitoring results in step 3.1, quantitative data on groundwater status, geostress level, construction disturbance intensity, joint orientation, and fault activity are extracted. The specific grading standards are as follows: Groundwater status: Based on the unit length inflow rate Q and fissure water pressure p, it is divided into 1) No water: Q<25L / (min·10m); p≤0.1MPa; 2) Small amount of groundwater: 25L / (min·10m)≤Q<125L / (min·10m); 0.1MPa<p≤0.5MPa; 3) Abundant groundwater: Q≥125L / (min·10m); p>0.5MPa; Ground stress levels are classified according to the strength-stress ratio Rc / σmax and ground stress σmax: 1) Low ground stress: Rc / σmax>7; σmax<15MPa; 2) Medium ground stress: 4<Rc / σmax≤7, 15MPa≤σmax<30MPa; 3) High ground stress: Rc / σmax≤4, σmax≥30MPa; Construction disturbance intensity: Based on the comprehensive index of displacement evaluation SR and blasting vibration velocity, it is divided into 1) low disturbance: SR < 0.3; blasting vibration velocity < 5 cm / s; 2) medium disturbance: 0.3 ≤ SR < 0.7, 5 cm / s ≤ blasting vibration velocity < 10 cm / s; 3) high disturbance: SR ≥ 0.7; blasting vibration velocity ≥ 10 cm / s; Joint attitude: Based on the joint dip angle α1, it is divided into 1) horizontal joints: α1≤30°; 2) gently dipping joints: 30°<α1<60°; 3) steeply dipping joints: α1≥60°; Fracture activity: 1) Stable fracture: annual sliding rate < 0.1 mm / year; fracture width ≤ 1 m; 2) Weakly active fracture: 0.1 mm / year ≤ annual sliding rate < 1 mm / year; 1 m < fracture width < 5 m; 3) Strongly active fracture: annual sliding rate ≥ 1 mm / year; fracture width ≥ 5 m.

10. A system for identifying the deformation and failure modes of tunnel sections in structural mélange zones, employing the method for identifying the deformation and failure modes of tunnel sections in structural mélange zones as described in claim 9, characterized in that: It includes a data acquisition module, a deformation and failure mode determination module, and an early warning module; The data acquisition module is used to acquire geological information of the surrounding rock of the tunnel. The deformation and failure mode determination module is used to identify the deformation and failure mode of the section to be excavated in the tunnel engineering section of the structural mixed rock zone. The early warning module is used to notify the construction party of the determined deformation and failure mode.

Images