Reinforcing method for fault fracture zone in TBM (Tunnel Boring Machine) construction

Abstract

The invention discloses a reinforcing method for a fault fracture zone in TBM construction, and belongs to the technical field of tunnel construction engineering. Comprising the steps that the grouting reinforcement range is determined according to geological parameters such as the width of a fracture zone, the fracture development degree and the underground water condition, then a composite grouting material containing superfine cement, nano-silicon dioxide and a water glass solution is prepared, and material components and performance parameters are adjusted according to the fracture development degree and the underground water pressure; a segmented retreating grouting technology is adopted, grouting hole sets are formed in the tunneling direction at intervals, high-pressure grouting is conducted on holes in the outermost side to form a closed curtain, then layered grouting is conducted on holes in the inner layer, and after the grouting amount reaches a design value 80%, grout is supplemented to the design value after initial setting; the outer layer of the composite reinforced structure is a cement-silicon dioxide crystal layer, and the inner layer of the composite reinforced structure is a nano-silicon dioxide modified reinforced layer. The method can effectively enhance the surrounding rock stability of the fault fracture zone, and is suitable for stratum reinforcement when the TBM tunnel passes through the fault fracture zone.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel construction engineering and relates to a method for reinforcing a fault fracture zone during TBM construction. Background Art

[0002] Tunneling projects using tunnel boring machines (TBMs) through fault fracture zones present complex geological challenges. Fault fracture zones typically feature fragmented rock mass, dense fissures, and complex groundwater conditions. This significantly reduces the surrounding rock's self-stabilizing capacity, making construction prone to engineering hazards such as collapse, water and mud inrush, and other hazards that pose a serious threat to construction safety and delays the project schedule. Effectively improving the stability of the surrounding rock in fault fracture zones and controlling groundwater seepage are key technical issues that urgently need to be addressed in TBM construction.

[0003] In the existing technology, grouting reinforcement methods are mostly used for the reinforcement of fault fracture zones, but there are the following deficiencies in actual applications: First, the determination of the grouting reinforcement range lacks a dynamic response mechanism to geological parameters. The reinforcement range is often determined based on empirical formulas or fixed ratios, without fully considering the differentiated effects of the fracture zone width, the degree of crack development, and the groundwater pressure. Second, traditional grouting materials are mostly single components or fixed ratios, and their performance cannot be dynamically adjusted according to geological conditions. In actual construction, insufficient prediction of geological conditions and poor adaptability of materials and processes often lead to uneven reinforcement effects and even cause engineering accidents. Therefore, there is an urgent need to develop a fault fracture zone reinforcement method based on dynamic adjustment of geological parameters to solve the technical problems of surrounding rock stability control and groundwater prevention and control in TBM construction. Summary of the Invention

[0004] An object of embodiments of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages to be described hereinafter.

[0005] When reinforcing the fault fracture zone in existing TBM construction, the grouting reinforcement range, the ratio of composite grouting materials and the grouting process are not dynamically adjusted according to geological parameters, resulting in poor reinforcement effect, poor surrounding rock stability, and easy occurrence of water and mud bursts.

[0006] The problem that the existing method for determining the scope of grouting reinforcement does not fully combine geological parameters such as the width of the fracture zone, the number of cracks and groundwater pressure, resulting in an unreasonable reinforcement scope and inability to effectively adapt to different geological conditions is solved.

[0007] The problem that the existing grouting reinforcement scope is determined without considering the influence of the uniaxial compressive strength of the surrounding rock on the reinforcement requirements, resulting in insufficient accuracy of the reinforcement scope for surrounding rocks of different strengths and possible excessive or insufficient reinforcement, is solved.

[0008] The solution is to solve the problem that the existing grouting reinforcement range spatial mapping and grouting hole arrangement lack accurate support from three-dimensional geological models, resulting in low matching between the grouting area and the fault fracture zone, and unreasonable setting of the grouting hole spatial coordinates and angles.

[0009] The invention solves the problem that the existing segmented backward grouting process lacks clear specifications for grouting hole group setting, grouting pressure stage control and construction sequence, resulting in uneven slurry diffusion, low grouting efficiency and unstable reinforcement effect.

[0010] The invention solves the problem that the grouting pressure, injection timing and injection amount of different layers in the existing layered grouting process lack differentiated control, resulting in inconsistent reinforcement effects of each layer, waste of slurry or loose reinforcement.

[0011] The invention solves the problem that the existing composite grouting materials have insufficient slurry stability, adhesion and impermeability under conditions of high crack development or high groundwater pressure, which affects the grouting reinforcement effect.

[0012] The problem that the existing grouting pressure control in the steady-pressure infiltration stage lacks a dynamic feedback mechanism and is difficult to adjust in real time according to the slurry diffusion radius, resulting in the grouting pressure being too high or too low, affecting the reinforcement range and quality, is solved.

[0013] The invention solves the problems of poor transition between the cement-silica crystal layer and the reinforcement layer, insufficient overall toughness, and easy cracking due to stress concentration or deformation in existing reinforced structures.

[0014] The invention solves the problem that the existing axial magnetic field application method lacks phased optimization of the directional arrangement of carbon fiber short fibers and the control of magnetic field intensity during the formation of the transition layer, resulting in insignificant reinforcement effect of the transition layer.

[0015] To this end, the technical solution provided by the present invention is: A method for reinforcing a fault fracture zone during TBM construction comprises the following steps: 1) Determine the scope of grouting reinforcement based on the geological parameters of the fault fracture zone, including fracture zone width, fracture development, and groundwater conditions. The fracture zone width is obtained through geological radar detection, the fracture development is characterized by the fracture density of drill core samples, and the groundwater conditions are determined through borehole water pressure testing. 2) preparing a composite grouting material according to the geological parameters in step 1), wherein the composite grouting material comprises, by weight, 55-65 parts of ultrafine cement with a particle size of 5-10 μm, 3-5 parts of nano-silicon dioxide, 10-15 parts of a water glass solution, and 15-32 parts of water, wherein the water glass solution has a modulus of 2.4-2.8 and a Baume degree of 35-40°Bé; When the degree of development of the cracks is ≥20 / m, the amount of nano-silica used is 4-5 parts and the modulus of the water glass solution is adjusted to 2.6-2.8; when the groundwater pressure is ≥0.2 MPa, the Baume degree of the water glass solution is adjusted to 38-40°Bé and the particle size of the ultrafine cement is adjusted to 5-7 μm; 3) Using a segmented backward grouting process, grouting hole groups are set up every 2-3m along the TBM excavation direction. Each group contains 6-8 radial grouting holes evenly distributed along the circumference of the tunnel. The grouting pressure is controlled at 1.5-2.5MPa. 4) When grouting, first perform high-pressure grouting on the outermost grouting holes to form a closed curtain, and then perform layered grouting on the inner grouting holes in sequence. Stop grouting when the grouting volume of each grouting hole reaches 80% of the design value. After the grouting liquid has initially set, replenish grouting to the design value. 5) After grouting is completed, a composite reinforcement structure with a gradual change from the outside to the inside is formed. The outer layer is a cement-silica crystal layer generated by the reaction of water glass and ultrafine cement, and the inner layer is a reinforcement layer modified by nano-silica.

[0016] Preferably, in the method for reinforcing a fault zone during TBM construction, the method for determining the grouting reinforcement range in step 1) comprises the following steps: The width of the fracture zone L was obtained by geological radar detection, the number of cracks per meter in the core samples was used to characterize the degree of crack development, and the groundwater pressure P was measured by borehole water pressure testing. When P≤0.1MPa, the grouting reinforcement range has a horizontal width of 1.5L+0.2N and a vertical depth of 1.2L; When 0.1MPa<P≤0.3MPa, the lateral width is 1.8L+0.3N and the longitudinal depth is 1.5L.

[0017] The unit of L is meter, the unit of N is bar / meter, and the calculation result is rounded up to 0.5 meter accuracy.

[0018] Preferably, in the reinforcement method for the fracture zone during TBM construction, in step 1), the uniaxial compressive strength Rc of the surrounding rock is measured by drilling and coring samples, in units of MPa, and the calculated result is rounded up to an accuracy of 0.5 meters. When the uniaxial compressive strength of the surrounding rock mass Rc is less than or equal to 30 MPa, the horizontal width is corrected to (1.5L + 0.2N) × (1 + 0.02 × (30-Rc)), and the vertical depth is corrected to 1.2L × (1 + 0.015 × (30-Rc)); When the uniaxial compressive strength of the surrounding rock mass Rc>30MPa, the transverse width is corrected to (1.8L+0.3N)×(1-0.01×(Rc-30)), and the longitudinal depth is corrected to 1.5L×(1-0.008×(Rc-30)).

[0019] Preferably, in the method for reinforcing a fractured zone during TBM construction, step 1) further comprises: The calculation result of the grouting reinforcement range is spatially mapped using a three-dimensional geological model to generate a wedge-shaped grouting area that matches the strike of the fault fracture zone. The method for spatial mapping the three-dimensional geological model includes: The fracture zone width L, number of fissures N, and groundwater pressure P are input into a three-dimensional geological model built on the SKUA-GOCAD platform. The three-dimensional geological model is based on rock mass structure data from drill core samples and uses the Kriging interpolation algorithm to generate the three-dimensional spatial distribution of the fault fracture zone. Based on the calculation results of the lateral width and longitudinal depth, a hexahedral grid is divided along the tunnel axis in the three-dimensional geological model with a unit of 0.5 m, and the lateral width value is mapped to the radial reinforcement thickness of each grid unit; Based on the dip angle α and inclination β of the fault fracture zone, a wedge-shaped grouting area is generated using the geological interface fitting module in the three-dimensional geological model. The top boundary of the wedge-shaped grouting area is fitted to the hanging wall interface of the fault fracture zone using the least squares method, and the bottom boundary is parallel to the footwall interface and the vertical distance from the footwall interface is 1.1-1.3 times the longitudinal depth. A thickness gradient zone is set between the wedge-shaped grouting area and the tunnel contour line, and the thickness of the gradient zone decreases according to a linear function from the bottom surface of the wedge-shaped grouting area to the tunnel contour line, with a decreasing gradient of 0.15-0.25 times the longitudinal depth per meter; the three-dimensional geological model outputs the spatial coordinates and drilling angles of the grouting hole group through a finite element meshing algorithm, wherein the angle γ between the axial direction of the grouting hole group and the direction of the fault fracture zone is calculated by vector projection as γ=90°-α±5°.

[0020] Preferably, in the method for reinforcing the fractured zone during TBM construction, the segmented retreat grouting process in step 3) comprises the following steps: Grouting hole groups are set up every 2-3m along the TBM excavation direction. The 6-8 radial grouting holes in each grouting hole group are evenly distributed along the circumference of the tunnel. The central angle between adjacent grouting holes is 45°-60°. The drilling depth H of the radial grouting holes satisfies H=1.2L+0.1N and H≤1.5L. When H>1.5L, H=1.5L, where L is the width of the fracture zone and N is the degree of fracture development. The pressure in the initial grouting stage is 1.5-1.8 MPa and continues until the grouting volume reaches 50% of the design value; The pressure in the steady-pressure infiltration stage is 2.0-2.2 MPa and continues until the grouting volume reaches 80% of the design value; The construction sequence of the grouting hole group is: backward grouting is carried out from the far end to the near end of the broken zone along the excavation direction, and grouting is performed at intervals of 2 holes in the same circumferential section, and the time interval between grouting of adjacent holes is greater than 30 minutes.

[0021] Preferably, in the method for reinforcing the fractured zone during TBM construction, the layered grouting in step 4) includes the following steps: The outermost grouting hole is continuously grouted to 80% of the design value at a grouting pressure of 2.3-2.5 MPa. After the slurry viscosity reaches 200-300 mPa·s, additional grouting is performed at a pressure of 1.8-2.0 MPa to 105-110% of the design value. The middle layer grouting holes are grouting to 80% of the design value at a grouting pressure of 1.8-2.0 MPa. After the initial setting time reaches 70% of its gel time, grouting is performed at a pressure of 1.5-1.8 MPa to 100-105% of the design value. The innermost grouting hole is grouting to 90% of the design value at a grouting pressure of 1.5-1.8 MPa. When the slurry viscosity reaches 150-180 mPa·s, it is grouting to the design value at a pressure of 1.2-1.5 MPa. The injection volume is adjusted according to the degree of crack development N. When N≥15 cracks / meter, the injection volume is increased by 5-8% of the design value.

[0022] Preferably, in the method for reinforcing the fracture zone during TBM construction, the composite grouting material in step 2) further comprises: 0.3-0.8 parts by weight of hydroxypropyl methylcellulose, wherein: When the crack development degree N ≥ 25 / m, the amount of hydroxypropyl methylcellulose added is 0.5-0.8 parts; When the groundwater pressure P≥0.25MPa, the amount of hydroxypropyl methylcellulose added is increased to 0.6-0.8 parts; The corresponding relationship between the addition amount Q of the hydroxypropyl methylcellulose and the grouting pressure P is: Q=0.3+0.02×(N-15)+0.015×(P / 0.1), where the unit of P is MPa.

[0023] Preferably, in the method for reinforcing a fault fracture zone during TBM construction, the pressure control in the steady-pressure infiltration stage adopts dynamic feedback regulation, including: During the steady-pressure infiltration stage, the slurry diffusion radius R is monitored in real time by a fiber optic sensor pre-buried in the grouting hole. When R is less than 0.8L, the grouting pressure is increased at a rate of 0.1MPa / min to an upper limit of 2.5MPa; when R is greater than or equal to 1.2L, the grouting pressure is decreased at a rate of 0.2MPa / min to 2.0MPa. The calculation formula of the diffusion radius R is: , where V is the cumulative grouting volume, N is the crack density, δ is the average crack width and δ = 0.1N −0.6 .

[0024] Preferably, in the method for reinforcing the fracture zone during TBM construction, a transition layer is further provided between the cement-silicon dioxide crystal layer and the reinforcement layer, and the transition layer is formed by: During the filling phase of the outermost grouting holes in step 4), short carbon fiber filaments accounting for 5-8% of the weight of the ultrafine cement are added to the filling slurry, and the filling slurry is injected into the range of 0.3-0.5 m from the inner edge of the cement-silicon dioxide crystal layer through a directional grouting pipe, while applying a 0.3-0.5 T axial magnetic field; the grouting outlet end of the directional grouting pipe is 0.2-0.3 m away from the crystal layer-flexible layer interface, and the fiber length of the short carbon fiber filaments is 6-8 mm and the diameter is 15-20 μm.

[0025] Preferably, in the method for reinforcing the fault fracture zone during TBM construction, the method for applying the 0.3-0.5T axial magnetic field is: A permanent magnet array is coaxially arranged in the grouting hole. The permanent magnet array is composed of NdFeB magnet blocks uniformly distributed along the circumference of the outer wall of the grouting pipe. The spacing between adjacent magnet blocks is 20-30 mm. The magnetic flux density on the surface of the magnet blocks is 0.4-0.6 T, and the magnetic field direction is parallel to the tunnel axis. The magnetic field intensity is regulated in two stages during the grouting process: Before initial coagulation, set the magnetic field strength to 0.5T and continue for 3-5 minutes; The magnetic field strength is set to 0.3 T and maintained for 1-2 minutes in the initial setting stage, when the slurry viscosity reaches 150-300 mPa·s.

[0026] The embodiments of the present invention have at least the following beneficial effects: This method establishes a precise coupling mechanism between geological conditions and reinforcement solutions by dynamically adjusting the grouting range, composite grouting material ratio, and grouting process based on geological parameters, addressing the "one-size-fits-all" approach of traditional methods. A composite system of ultrafine cement and nanosilica can fill fractures of varying sizes. The parameters of the water glass solution dynamically adjust with water pressure and fracture density, ensuring that the slurry quickly solidifies in a hypertonic environment to form an effective curtain. Segmented, backward grouting combined with a layered refilling process achieves gradient reinforcement from the outside in, significantly improving the overall stability of the surrounding rock and reducing the risk of water and mud inrush.

[0027] This method uses geological radar detection and borehole testing to obtain key geological parameters and establishes a quantitative calculation model for grouting range based on groundwater pressure. This model directly correlates the horizontal width and vertical depth with the degree of fracture development and water pressure. Compared to traditional empirical methods, this method avoids the safety hazards caused by insufficient reinforcement coverage or the waste of resources caused by excessive reinforcement. Especially under high water pressure (P>0.1MPa), this method enhances the water-blocking effect by expanding the reinforcement scope, improving the scientific nature and adaptability of grouting design.

[0028] This method incorporates the uniaxial compressive strength of the surrounding rock into the reinforcement range correction parameter, using different correction factors for soft rock (Rc ≤ 30 MPa) and hard rock (Rc > 30 MPa). In soft rock conditions, the reinforcement range is expanded to compensate for insufficient rock mass self-stabilization, while in hard rock conditions, the range is appropriately reduced to avoid redundant reinforcement. This addresses the issue of differentiated reinforcement requirements for surrounding rock of varying strengths, making the reinforcement plan more tailored to actual geological characteristics and improving resource utilization efficiency.

[0029] This method utilizes a three-dimensional geological model to accurately map the spatial extent of the grouting area. The three-dimensional distribution of the fault fracture zone is constructed using a Kriging interpolation algorithm. Combined with a wedge-shaped grouting area and a gradient thickness zone design, the reinforcement range is precisely matched to the fault strike and dip. The grouting hole coordinates and angles output by the finite element meshing algorithm ensure that the grout diffuses along the dominant fracture path, avoiding blind spots and overlaps caused by traditional two-dimensional designs. This improves the spatial matching and overall effectiveness of the reinforced structure.

[0030] This invention systematically standardizes the process parameters for staged, retreating grouting, defining formulas for calculating the spacing, angle, and drilling depth of grouting hole groups. This approach, combined with a "distal-to-proximal" retreating construction method and a skip-hole grouting sequence, reduces cross-linking and ensures layer-by-layer grouting. Staged pressure control (low-pressure penetration in the initial stage, followed by medium-pressure diffusion during the stabilization phase) adapts to the development of fractures, preventing surrounding rock splitting caused by high pressure or insufficient diffusion caused by low pressure, significantly improving grouting uniformity and the stability of the reinforcement effect.

[0031] This invention employs differentiated pressure control and injection strategies for grouting holes in different layers: high-pressure grouting in the outer holes creates a high-strength curtain, while low-pressure injection in the inner holes ensures the filling of fine cracks. The injection volume is linked to the crack density to avoid slurry waste. By dynamically controlling the injection timing based on the slurry's viscosity and initial setting time, this solves the problem of uneven reinforcement across layers in traditional layered grouting. This results in an impermeable outer layer and toughened inner layers, creating a composite reinforcement with gradient mechanical properties.

[0032] This invention introduces hydroxypropyl methylcellulose into the composite grouting material. Its added amount is linearly correlated with fracture density and water pressure. Through the adsorption and bridging effects of polymer chains, it improves the slurry's cohesiveness and resistance to water dilution in hypertonic environments. When N ≥ 25 fractures / meter or P ≥ 0.25 MPa, increasing the cellulose content effectively inhibits slurry loss, prolongs the injection time, and improves the slurry's late-stage strength development, resolving the technical challenges of poor slurry stability and loose reinforcement under high fracture water pressure.

[0033] This method uses fiber optic sensors to monitor the slurry diffusion radius in real time, establishing a dynamic feedback mechanism between grouting pressure and diffusion effect. When diffusion is insufficient, the pressure is gradually increased to expand the range; when diffusion is excessive, the pressure is reduced to avoid energy waste. Combined with a quantitative calculation model of crack density and width, this method enables intelligent regulation of grouting pressure. This method avoids the blindness of traditional fixed-pressure processes, ensuring that the slurry covers the designed reinforcement range while minimizing surrounding rock damage, improving grouting efficiency and controllable reinforcement quality.

[0034] This invention incorporates a carbon fiber staple-reinforced transition layer between the crystallization layer and the reinforcement layer. Directional grouting and an axial magnetic field align the staple fibers along the stress transfer direction, creating a rigid-flexible transition structure. The carbon fibers' bridging effect effectively alleviates interfacial stress concentration, while the magnetic field regulates fiber orientation and enhances interlayer bond strength. This solves the cracking problem associated with conventional reinforced structures caused by sudden interface changes, enhancing the composite structure's deformation resistance and overall durability.

[0035] This method regulates the axial magnetic field intensity in stages. A strong magnetic field (0.5T) before initial solidification promotes rapid alignment of the carbon fibers, while a weak magnetic field (0.3T) during the initial solidification phase maintains fiber orientation stability, preventing magnetic interference with the slurry's solidification process. The uniform distribution of NdFeB magnets around the periphery ensures magnetic field uniformity, resolving issues such as uneven fiber dispersion and disrupted solidification processes associated with traditional magnetic field application methods. This improves fiber orientation in the transition layer by over 30%, significantly enhancing interlaminar shear strength and crack resistance.

[0036] Other advantages, objectives, and features of the embodiments of the present invention will be reflected in part through the following description, and in part will be understood by those skilled in the art through study and practice of the embodiments of the present invention. DETAILED DESCRIPTION

[0037] The embodiments of the present invention are further described in detail below in conjunction with the embodiments so that those skilled in the art can implement the invention with reference to the description.

[0038] The present invention provides a method for reinforcing a fault fracture zone during TBM construction, comprising the following steps: 1) Determine the scope of grouting reinforcement based on the geological parameters of the fault fracture zone, including fracture zone width, fracture development, and groundwater conditions. The fracture zone width is obtained through geological radar detection, the fracture development is characterized by the fracture density of drill core samples, and the groundwater conditions are determined through borehole water pressure testing. 2) preparing a composite grouting material according to the geological parameters in step 1), wherein the composite grouting material comprises, by weight, 55-65 parts of ultrafine cement with a particle size of 5-10 μm, 3-5 parts of nano-silicon dioxide, 10-15 parts of a water glass solution, and 15-32 parts of water, wherein the water glass solution has a modulus of 2.4-2.8 and a Baume degree of 35-40°Bé; When the degree of development of the cracks is ≥20 / m, the amount of nano-silica used is 4-5 parts and the modulus of the water glass solution is adjusted to 2.6-2.8; when the groundwater pressure is ≥0.2 MPa, the Baume degree of the water glass solution is adjusted to 38-40°Bé and the particle size of the ultrafine cement is adjusted to 5-7 μm; 3) Using a segmented backward grouting process, grouting hole groups are set up every 2-3m along the TBM excavation direction. Each group contains 6-8 radial grouting holes evenly distributed along the circumference of the tunnel. The grouting pressure is controlled at 1.5-2.5MPa. 4) When grouting, first perform high-pressure grouting on the outermost grouting holes to form a closed curtain, and then perform layered grouting on the inner grouting holes in sequence. Stop grouting when the grouting volume of each grouting hole reaches 80% of the design value. After the grouting liquid has initially set, replenish grouting to the design value. 5) After grouting is completed, a composite reinforcement structure with a gradual change from the outside to the inside is formed. The outer layer is a cement-silica crystal layer generated by the reaction of water glass and ultrafine cement, and the inner layer is a reinforcement layer modified by nano-silica.

[0039] In this embodiment, the grouting range is determined based on the geological parameters of the fault fracture zone. Geological radar (such as the commercially available LTD-2100) can be used to detect the fracture zone width L. A coring drill (such as the XY-1) can be used to determine the number of fractures per linear meter (N). A hydraulic pressure tester (such as the YT-2000) can be used to measure the groundwater pressure (P). When P ≤ 0.1 MPa, the horizontal width is 1.5 L + 0.2 N, and the vertical depth is 1.2 L. When 0.1 MPa < P ≤ 0.3 MPa, the horizontal width is 1.8 L + 0.3 N, and the vertical depth is 1.5 L. When preparing composite grouting materials, use an electronic scale (such as an ACS-30) to weigh the raw materials. The weight percentages are: 55-65 parts ultrafine cement with a particle size of 5-10 μm (such as commercially available PO 42.5 grade ultrafine cement), 3-5 parts nanosilica (commercially available product with a purity ≥99%, particle size 20-30 nm), 10-15 parts water glass solution (industrial grade, modulus 2.4-2.8, Baume 35-40°Bé), and 15-32 parts clean water. When the number of cracks is ≥20 / meter, adjust the nanosilica dosage to 4-5 parts and the water glass solution modulus to 2.6-2.8. When the groundwater pressure is ≥0.2 MPa, adjust the water glass Baume to 38-40°Bé and the ultrafine cement particle size to 5-7 μm. All raw materials are purchased from conventional suppliers and evenly mixed at the mixing plant using a mixer (such as the JB-500). "Linear meter" refers to the length per meter extending along a specific direction (such as the borehole axis, tunneling direction, etc.). Number of fractures per linear meter refers to the number of fractures (cracks) counted per meter along the axis of the rock mass (such as a drilled core sample), measured in fractures per meter. "Number of fractures per linear meter" is a core parameter describing the degree of rock fragmentation, directly affecting the calculation of grouting reinforcement range and the adjustment of material ratios. It must be obtained through standardized drilling, coring, and fracture counting processes.

[0040] A segmented, backward grouting process is employed, with grouting hole groups set up every 2-3 meters along the TBM's excavation direction. Each group consists of 6-8 radial grouting holes evenly spaced along the tunnel circumference (center angles between adjacent holes are 45°-60°). A drilling rig (such as the ZDY-4000S) is used to drill holes at the tunnel face at the designed spacing, with a depth of H = 1.2L + 0.1N and H ≤ 1.5L (1.5L is used if the limit is exceeded). Grouting pipes (Φ50mm steel or PVC pipes are acceptable) are installed. Grouting equipment uses a grouting pump (such as the KBY-50 / 70). Initial grouting pressure is maintained at 1.5-1.8MPa and continues until the grouting volume reaches 50% of the designed value. During the steady-pressure infiltration phase, the pressure is increased to 2.0-2.2MPa and continued until the grouting volume reaches 80%. Grouting is performed in a backward-moving sequence, from the far end of the fracture zone toward the near end. Within the same section, grouting is performed two holes at a time, with intervals of >30 minutes between adjacent holes. Grouting pipes are evenly distributed along the tunnel circumference at the tunnel face. Equipment is installed near the tunnel face, and pressure sensors (such as the MPM480) monitor pressure changes in real time. During grouting, the outermost grouting holes are first grouted continuously at a pressure of 2.0-2.5 MPa to 80% of the design value. Once the grout viscosity reaches 200-300 mPa·s, additional grouting is performed at a pressure of 1.8-2.0 MPa to 105-110% of the design value, forming the outer cement-silica crystalline layer. The intermediate holes are grouted at a pressure of 1.8-2.0 MPa to 80% of the design value. Once the initial setting time reaches 70% of the gel time, additional grouting is performed at a pressure of 1.5-1.8 MPa to 100-105%. The innermost holes are grouted at a pressure of 1.5-1.8 MPa to 90% of the design value. Once the grout viscosity reaches 150-180 mPa·s, additional grouting is performed at a pressure of 1.2-1.5 MPa to the design value, forming the inner nano-silica modified reinforcement layer. The additional grouting volume is adjusted based on the N value, increasing by 5-8% when N is ≥ 15 lines / meter. During the grouting process, the grouting pipe outlet is located at the designed depth of the holes in different layers. By adjusting the pressure in stages, the grouting liquid diffuses layer by layer to fill the cracks. This ultimately forms a composite structure that gradually changes from the outside to the inside. The outer layer is formed by the reaction of water glass and ultrafine cement to form a dense crystalline layer, while the inner layer is modified by nano-silica filling to improve toughness, effectively blocking groundwater infiltration and enhancing the integrity of the surrounding rock. This embodiment dynamically adjusts the grouting range and material ratio through geological parameters, and combines it with the segmented and layered grouting process to solve the problems of blind reinforcement range, poor material adaptability, and uneven grouting effect in traditional methods. It can significantly improve the stability of the surrounding rock in the fault fracture zone and reduce the risk of water and mud inrush during TBM construction. It is suitable for geological conditions with different degrees of fracture development and groundwater pressure.

[0041] In one embodiment of the present invention, preferably, the method for determining the grouting reinforcement range in step 1) comprises the following steps: The width of the fracture zone L was obtained by geological radar detection, the number of cracks per meter in the core samples was used to characterize the degree of crack development, and the groundwater pressure P was measured by borehole water pressure testing. When P≤0.1MPa, the grouting reinforcement range has a horizontal width of 1.5L+0.2N and a vertical depth of 1.2L; When 0.1MPa<P≤0.3MPa, the lateral width is 1.8L+0.3N and the longitudinal depth is 1.5L.

[0042] The unit of L is meter, the unit of N is bar / meter, and the calculation result is rounded up to 0.5 meter accuracy.

[0043] In this embodiment, the width L of the fracture zone is detected by geological radar. Common geological radar equipment on the market can be used. Its transmitting antenna and receiving antenna are installed on the tunnel face or side wall. They move and scan along the tunnel axis, and the boundary position and width data of the fracture zone are obtained by using the principle of electromagnetic wave reflection. A coring machine is used to arrange holes around the tunnel. The drilling depth penetrates the fracture zone. The core samples taken out are placed in the core box. The number of cracks per linear meter N is counted manually or with image recognition software to characterize the degree of fracture development. The groundwater pressure P is obtained through a borehole water pressure test. A pressure sensor can be installed in the borehole. The sensor probe is located in the aquifer of the fracture zone and connected to a data acquisition instrument to monitor the water pressure value in real time. The calculation intervals are divided according to different thresholds of groundwater pressure (P): When P ≤ 0.1 MPa, the lateral width of the grouting reinforcement range is 1.5 L + 0.2 N, and the vertical depth is 1.2 L. When 0.1 MPa < P ≤ 0.3 MPa, the lateral width is adjusted to 1.8 L + 0.3 N, and the vertical depth is adjusted to 1.5 L. L is expressed in meters, and N is expressed in bars / meter. The measured values ​​are directly substituted into the calculation. For example, if L = 5 meters, N = 10 bars / meter, and P = 0.08 MPa, the lateral width is 1.5 × 5 + 0.2 × 10 = 9.5 meters, and the vertical depth is 1.2 × 5 = 6 meters. If P = 0.2 MPa, the lateral width is 1.8 × 5 + 0.3 × 10 = 12 meters, and the vertical depth is 1.5 × 5 = 7.5 meters. The calculations can be performed using an engineering calculator or computer software, and the results are rounded to one decimal place. The data obtained by geological radar, coring machines and pressure sensors need to be calibrated and verified to ensure the accuracy of the parameters. The calculation results of the horizontal width and vertical depth are used as the basic parameters for grouting design to determine the layout range and depth of the grouting holes. In actual construction, the boundaries of the grouting area can be delineated on both sides of the tunnel according to the calculated horizontal width, and the vertical depth corresponds to the drilling depth of the grouting holes. For example, when the vertical depth is 6 meters, the drill needs to drill the grouting hole to 6 meters outside the tunnel outline to ensure that the slurry covers the entire reinforcement range. This method avoids the blindness of the traditional empirical method by quantifying the relationship between geological parameters and reinforcement range, making the grouting design more in line with actual geological conditions. This embodiment obtains key parameters through geological radar, core drilling and water pressure testing, and combines them with quantitative calculation formulas under different water pressure conditions to solve the problem of the lack of dynamic response of traditional grouting reinforcement range determination methods. It can accurately calculate the reinforcement range based on the width of the fracture zone, the number of cracks and the groundwater pressure, improve the scientific nature and effectiveness of the grouting design, and ensure that a reliable reinforcement area can be formed under different hydrogeological conditions.

[0044] In one embodiment of the present invention, preferably, in step 1), the uniaxial compressive strength Rc of the surrounding rock is measured by drilling core samples, in units of MPa, and the calculated result is rounded up to an accuracy of 0.5 meters. When the uniaxial compressive strength of the surrounding rock mass Rc is less than or equal to 30 MPa, the horizontal width is corrected to (1.5L + 0.2N) × (1 + 0.02 × (30-Rc)), and the vertical depth is corrected to 1.2L × (1 + 0.015 × (30-Rc)); When the uniaxial compressive strength of the surrounding rock mass Rc>30MPa, the transverse width is corrected to (1.8L+0.3N)×(1-0.01×(Rc-30)), and the longitudinal depth is corrected to 1.5L×(1-0.008×(Rc-30)).

[0045] In this embodiment, a core drill is used to drill holes around the tunnel. The drilling locations can be selected from representative areas such as the tunnel vault, haunch, and sidewalls. The drilling depth must penetrate the fault fracture zone and enter the intact rock layer by at least 0.5 meters. The length of the core sample removed must meet the requirements for processing into standard specimens (50 mm diameter and 100 mm height). The core sample is transported to the laboratory and processed into cylindrical specimens with parallel ends using a rock cutter and grinder. The uniaxial compressive strength test is performed using a pressure testing machine. During the test, the specimen is placed at the center of the upper and lower pressure plates of the pressure testing machine and uniformly loaded at a rate of 0.5-1.0 MPa / s until failure. The peak load is recorded and the uniaxial compressive strength Rc is calculated in MPa. The measured Rc value is rounded up to an accuracy of 0.5 meters. For example, if the calculated result is 28.3 MPa, it is rounded to 28.5 MPa; if it is 30.1 MPa, it is rounded to 30.5 MPa. Using 30 MPa as the threshold, two correction scenarios are defined: when Rc ≤ 30 MPa, the surrounding rock is judged to be soft or medium-hard rock, and the grouting reinforcement scope needs to be expanded; when Rc > 30 MPa, the surrounding rock is judged to be hard, and the reinforcement scope can be appropriately reduced. This threshold is determined based on the surrounding rock strength classification standard in rock mechanics and the basic requirements for surrounding rock stability during TBM construction. When Rc ≤ 30 MPa, the lateral width is corrected to (1.5L + 0.2N) × (1 + 0.02 × (30 - Rc)), and the longitudinal depth is corrected to 1.2L × (1 + 0.015 × (30 - Rc)). For example, if L = 6 meters, N = 12 bars / meter, and Rc = 25 MPa, the lateral width is (1.5 × 6 + 0.2 × 12) × (1 + 0.02 × 5) = 11.4 × 1.1 = 12.54 meters, and the longitudinal depth is 1.2 × 6 × (1 + 0.015 × 5) = 7.2 × 1.075 = 7.74 meters. When Rc > 30 MPa, the lateral width is corrected to (1.8L + 0.3N) × (1 - 0.01 × (Rc - 30)), and the longitudinal depth is corrected to 1.5L × (1 - 0.008 × (Rc - 30)). For example, if Rc = 35 MPa, the horizontal width correction factor is 1-0.01 × 5 = 0.95, and the vertical depth correction factor is 1-0.008 × 5 = 0.96. The corrected values ​​serve as the basis for the final grouting range design, guiding the grouting hole layout and drilling depth control. This example introduces the uniaxial compressive strength parameter of the surrounding rock mass to establish a dynamic correction mechanism for the grouting range based on rock mass strength. For soft surrounding rock, the reinforcement range is appropriately expanded to compensate for insufficient self-stabilization capacity, while for hard surrounding rock, the range is reasonably reduced to avoid resource waste. This addresses the problem of traditional methods not considering differences in surrounding rock strength, making the grouting design more consistent with actual geomechanical properties, improving the targetedness and cost-effectiveness of the reinforcement scheme, and ensuring construction safety and reinforcement effectiveness under conditions of varying surrounding rock strengths.

[0046] In one embodiment of the present invention, preferably, step 1) further includes: The calculation result of the grouting reinforcement range is spatially mapped using a three-dimensional geological model to generate a wedge-shaped grouting area that matches the strike of the fault fracture zone. The method for spatial mapping the three-dimensional geological model includes: The fracture zone width L, number of fissures N, and groundwater pressure P are input into a three-dimensional geological model built on the SKUA-GOCAD platform. The three-dimensional geological model is based on rock mass structure data from drill core samples and uses the Kriging interpolation algorithm to generate the three-dimensional spatial distribution of the fault fracture zone. Based on the calculation results of the lateral width and longitudinal depth, a hexahedral grid is divided along the tunnel axis in the three-dimensional geological model with a unit of 0.5 m, and the lateral width value is mapped to the radial reinforcement thickness of each grid unit; Based on the dip angle α and inclination β of the fault fracture zone, a wedge-shaped grouting area is generated using the geological interface fitting module in the three-dimensional geological model. The top boundary of the wedge-shaped grouting area is fitted to the hanging wall interface of the fault fracture zone using the least squares method, and the bottom boundary is parallel to the footwall interface and the vertical distance from the footwall interface is 1.1-1.3 times the longitudinal depth. A thickness gradient zone is set between the wedge-shaped grouting area and the tunnel contour line, and the thickness of the gradient zone decreases according to a linear function from the bottom surface of the wedge-shaped grouting area to the tunnel contour line, with a decreasing gradient of 0.15-0.25 times the longitudinal depth per meter; the three-dimensional geological model outputs the spatial coordinates and drilling angles of the grouting hole group through a finite element meshing algorithm, wherein the angle γ between the axial direction of the grouting hole group and the direction of the fault fracture zone is calculated by vector projection as γ=90°-α±5°.

[0047] In this embodiment, parameters such as the width L of the fracture zone, the number N of cracks, and the groundwater pressure P are input into the three-dimensional geological model. The model can be constructed based on the commonly used SKUA-GOCAD software platform on the market. First, the rock structure data of the drill core samples are imported, including lithology, fracture occurrence, filling type, etc. The data is spatially interpolated using the Kriging interpolation algorithm to generate a three-dimensional spatial distribution model of the fault fracture zone, which intuitively displays the spatial morphology of the fracture zone, such as the strike, dip, and inclination. When inputting data, parameter entry and model rendering can be completed through the graphical interface of the computer terminal. The model accuracy can be set to a 0.5-meter grid resolution to ensure consistency with actual geological conditions. In the three-dimensional geological model, a hexahedral grid is divided along the axis of the tunnel with a unit of 0.5 meters, and each grid unit corresponds to a grouting section in the longitudinal direction of the tunnel. According to the lateral width value calculated according to claim 2, it is mapped to the radial reinforcement thickness of each grid unit. For example, if the calculated lateral width value of a unit is 10 meters, the radial reinforcement thickness of the tunnel surrounding the unit is 10 meters, and the grouting holes need to be drilled into the broken zone rock within this thickness range. The grid division and thickness mapping process are completed by the grid subdivision tool provided by the model to ensure that the reinforcement range is evenly distributed in the three-dimensional space and avoid grouting blind spots or overlapping areas. Based on the dip angle α and inclination β of the fault fracture zone, the model's geological interface fitting module generates a wedge-shaped grouting zone. The top boundary is fitted to the hanging wall interface of the fault fracture zone using the least squares method. The bottom boundary is parallel to the footwall interface and has a vertical distance from the footwall interface of 1.1-1.3 times the longitudinal depth (for example, for a longitudinal depth of 8 meters, the bottom distance is 8.8-10.4 meters). A thickness gradient zone is defined between the wedge and the tunnel outline. The thickness of the gradient zone decreases linearly from the bottom of the wedge to the tunnel outline, with a gradient of 0.15-0.25 times the longitudinal depth per meter (for example, for a longitudinal depth of 10 meters, the gradient is 1.5-2.5 meters per meter). The 3D model uses a finite element meshing algorithm to output the spatial coordinates and drilling angles of the grouting hole group. The angle γ between the grouting hole axis and the fault strike is calculated as γ = 90° - α ± 5°. For example, when α = 60°, γ is between 25° and 35°. During construction, the drilling rig locates the drilling holes on the tunnel face according to the output coordinates and angles, ensuring that the grouting holes penetrate the broken zone along the optimal path. This embodiment achieves precise spatial mapping of the grouting range through a three-dimensional geological model, resolving the mismatch between the reinforced area and the fault spatial morphology in traditional two-dimensional design. The Kriging interpolation algorithm ensures that the model accurately reflects the distribution of the fracture zone. The wedge-shaped and gradient zone designs are adapted to the fault's dip characteristics, and finite element calculations enable precise positioning of the grouting holes. This method dynamically couples the grouting range with the geological structure, improving the effectiveness of slurry diffusion and the spatial matching of the reinforced structure. It reduces the blind grouting caused by traditional empirical methods and ensures the reliability and uniformity of fault fracture zone reinforcement during TBM construction.

[0048] In one embodiment of the present invention, preferably, the segmented retreat grouting process in step 3) includes the following steps: Grouting hole groups are set up every 2-3m along the TBM excavation direction. The 6-8 radial grouting holes in each grouting hole group are evenly distributed along the circumference of the tunnel. The central angle between adjacent grouting holes is 45°-60°. The drilling depth H of the radial grouting holes satisfies H=1.2L+0.1N and H≤1.5L. When H>1.5L, H=1.5L, where L is the width of the fracture zone and N is the degree of fracture development. The pressure in the initial grouting stage is 1.5-1.8 MPa and continues until the grouting volume reaches 50% of the design value; The pressure in the steady-pressure infiltration stage is 2.0-2.2 MPa and continues until the grouting volume reaches 80% of the design value; The construction sequence of the grouting hole group is: backward grouting is carried out from the far end to the near end of the broken zone along the excavation direction, and grouting is performed at intervals of 2 holes in the same circumferential section, and the time interval between grouting of adjacent holes is greater than 30 minutes.

[0049] In this embodiment, grouting hole groups are set up every 2-3 meters along the TBM's excavation direction. Each group contains 6-8 radial grouting holes, evenly spaced around the tunnel circumference, with the central angle between adjacent holes being 45°-60° (e.g., approximately 51.4° for 7 holes). Before drilling, the hole locations are marked on the tunnel face using a surveying instrument. The holes are evenly spaced around the tunnel circumference, 0.5-1.0 m from the tunnel outline. Drilling is performed using a drilling rig, with the drilling depth H calculated according to the formula H = 1.2L + 0.1N, with H ≤ 1.5L (L is the width of the fracture zone, and N is the degree of fracture development). For example, when L = 4m and N = 15 bars / meter, H = 1.2 × 4 + 0.1 × 15 = 6.3m. Since 6.3m ≤ 1.5 × 4 = 6m does not hold, H = 6m. When L = 3m and N = 10 bars / meter, H = 1.2 × 3 + 0.1 × 10 = 4.6m. Since H ≤ 4.5m does not hold, H = 4.5m. After drilling, install the grouting pipe, with the end of the pipe 0.2-0.3m from the bottom of the hole and the outer end fixed to the tunnel face. The grouting process is divided into the initial grouting stage and the pressure-stabilizing infiltration stage. In the initial stage, the pressure is controlled at 1.5-1.8MPa, and the slurry is injected into the hole through the grouting pump, and the grouting volume continues until the grouting volume reaches 50% of the design value. For example, the designed grouting volume of a hole is 1000L, and when 500L is injected, it enters the next stage. During the pressure-stabilizing infiltration stage, the pressure is increased to 2.0-2.2MPa, and grouting continues to 80% of the design volume (i.e. 800L). Pressure control is monitored in real time by a pressure sensor installed at the outlet of the grouting pump. When the pressure exceeds the set upper limit, the grouting pump automatically adjusts the flow rate to reduce the pressure; when the pressure is insufficient, the pump pressure is gradually increased to the target range. The grouting pipe is connected to the grouting pump through a high-pressure hose, and a pressure gauge is installed on the hose to facilitate on-site operators to observe pressure changes. Grouting holes are constructed using a backward grouting method, that is, construction is carried out sequentially from the far end of the fracture zone to the near end (in the opposite direction of excavation). After each grouting group is completed, the TBM advances 2-3 meters before the next grouting group is carried out. Within the same circumferential section, a skipping grouting sequence is used, with intervals of two holes. For example, when an eight-hole arrangement is used, holes 1, 4, and 7 are grouted first, followed by holes 2, 5, and 8, and finally holes 3 and 6. The interval between grouting of adjacent holes is greater than 30 minutes. Skipping grouting can prevent interference between slurries in adjacent holes and reduce slurry cross-flow. During the grouting process, the grouting holes are sealed with grouting plugs. The grouting plugs are installed 1-2 meters inside the hole mouth and fixed with expansion bolts to prevent slurry backflow.

[0050] This embodiment addresses the issues of uneven grouting, crosstalk, and blind pressure control in traditional grouting by clarifying the calculation method for grouting hole group spacing, angles, and depths, combined with staged pressure control and a backward-stepping skip-hole construction sequence. Staged pressure control adapts to the permeability characteristics of fractures, backward-stepping construction ensures that the reinforcement coverage gradually expands with tunneling progress, and the skip-hole sequence reduces the impact of adjacent holes, thereby improving grouting uniformity and the stability of the reinforcement effect, ensuring TBM construction safety and the quality of surrounding rock reinforcement.

[0051] In one embodiment of the present invention, preferably, the layered grouting in step 4) includes the following steps: The outermost grouting hole is continuously grouted to 80% of the design value at a grouting pressure of 2.3-2.5 MPa. After the slurry viscosity reaches 200-300 mPa·s, additional grouting is performed at a pressure of 1.8-2.0 MPa to 105-110% of the design value. The middle layer grouting holes are grouting to 80% of the design value at a grouting pressure of 1.8-2.0 MPa. After the initial setting time reaches 70% of its gel time, grouting is performed at a pressure of 1.5-1.8 MPa to 100-105% of the design value. The innermost grouting hole is grouting to 90% of the design value at a grouting pressure of 1.5-1.8 MPa. When the slurry viscosity reaches 150-180 mPa·s, it is grouting to the design value at a pressure of 1.2-1.5 MPa. The injection volume is adjusted according to the degree of crack development N. When N≥15 cracks / meter, the injection volume is increased by 5-8% of the design value.

[0052] The outermost grouting hole in this embodiment is located at the farthest end of the tunnel perimeter and serves to form a closed curtain. During construction, a composite grouting material is injected into the hole using a grouting pump, initially using a grouting pressure of 2.0-2.5 MPa and continuing grouting until the grouting volume reaches 80% of the designed value. At this point, grouting is suspended, and a viscometer is used to sample the slurry at the hole mouth to test the viscosity. When the viscosity reaches 200-300 mPa•s (indicating that the slurry has begun to set but has not completely solidified), the process switches to the replenishment phase, adjusting the pressure to 1.8-2.0 MPa and continuing to replenish the slurry to 105-110% of the designed value. The grouting pump can be a common piston grouting pump on the market. A pressure sensor is installed at the outlet of the grouting pump to monitor pressure changes in real time. The end of the grouting pipe extends to the bottom of the outermost hole to ensure that the slurry covers the outermost layer of the reinforcement range. The middle layer grouting holes are located between the outermost and innermost holes. Their primary function is to fill the cracks in the middle region and enhance interlayer adhesion. After grouting to 80% of the design value using a grouting pressure of 1.8-2.0 MPa, grouting is paused and the grouting time is recorded. By calculating the slurry gel time (which can be determined through on-site gel time testing), when the initial setting time reaches 70% of the gel time (for example, if the gel time is 60 minutes, wait 42 minutes), the refilling procedure is initiated, reducing the pressure to 1.5-1.8 MPa and refilling to 100-105% of the design value. During construction, the grouting pipe must be fixed in the middle of the hole to prevent the slurry from directly eroding the hole wall and causing cracks to expand. During refilling, the grouting line can be switched using a three-way valve to ensure that the slurry is evenly distributed to the cracks in the middle layer. The innermost grouting hole, located near the tunnel outline, primarily aims to fill fine cracks and strengthen the inner rock mass. Grouting is performed at a pressure of 1.5-1.8 MPa to 90% of the design value. A viscometer is used to monitor the slurry viscosity in real time. When the viscosity reaches 150-180 mPa·s, indicating penetration into the fine cracks, the slurry is then refilled at a pressure of 1.2-1.5 MPa to the design value. The injection volume is adjusted based on the crack density (N). When N is ≥ 15 cracks / meter, the injection volume is increased by 5-8% from the original design value to compensate for slurry losses caused by the high crack density. For example, the design injection volume for a hole is 200 L, but when N is 18 cracks / meter, the injection volume is adjusted to 210-216 L. The grouting equipment is the same as for the outermost hole, with a screened section at the front of the grouting pipe to facilitate slurry penetration into the inner rock mass at low pressure. This embodiment solves the problems of uneven reinforcement, grout waste, or loose filling in traditional layered grouting by setting differentiated pressure control parameters and injection strategies for grouting holes at different levels. High pressure in the outermost holes forms an impermeable curtain, while timely injection in the middle holes enhances the transition. Low pressure in the innermost holes infiltrates and fills fine cracks. The injection volume is dynamically adjusted based on the crack density, resulting in a composite layer with gradually varying strength and impermeability from the outside to the inside of the reinforced structure. This improves overall stability and waterproofing performance, while also avoiding excessive grouting and increasing construction economics.

[0053] In one embodiment of the present invention, preferably, the composite grouting material in step 2) further comprises: 0.3-0.8 parts by weight of hydroxypropyl methylcellulose, wherein: When the crack development degree N ≥ 25 / m, the amount of hydroxypropyl methylcellulose added is 0.5-0.8 parts; When the groundwater pressure P≥0.25MPa, the amount of hydroxypropyl methylcellulose added is increased to 0.6-0.8 parts; The corresponding relationship between the addition amount Q of the hydroxypropyl methylcellulose and the grouting pressure P is: Q=0.3+0.02×(N-15)+0.015×(P / 0.1), where the unit of P is MPa.

[0054] In this example, 0.3-0.8 parts by weight of hydroxypropyl methylcellulose (HPMC) is added to the composite grouting material in step 2). The addition amount is dynamically adjusted based on the fissure density N and groundwater pressure P. When N ≥ 25 fissures / meter, it is considered a high fissure density environment, and the HPMC addition amount is adjusted to 0.5-0.8 parts. When the groundwater pressure P ≥ 0.25 MPa, it is considered a high water pressure environment, and the addition amount is increased to 0.6-0.8 parts. For example, when N = 30 fissures / meter and P = 0.3 MPa, the HPMC addition amount is 0.7 parts; when N = 20 fissures / meter and P = 0.2 MPa, the HPMC addition amount is 0.4 parts. The addition amount is calculated using the formula Q = 0.3 + 0.02 × (N - 15) + 0.015 × (P / 0.1), where N is the measured number of fissures / meter and P is the measured water pressure (MPa). The result is rounded to one decimal place. When preparing the composite grouting material, ultrafine cement, nanosilica, and hydroxypropyl methylcellulose are premixed in a dry mixer for 3-5 minutes to ensure uniform dispersion of the powders. Waterglass solution and water are then added and stirred in a wet mixer for 5-8 minutes until a homogeneous slurry is formed. Dry mixers can be vertical ribbon mixers, while wet mixers can be planetary forced mixers, both of which are common commercially available construction material mixing equipment. During mixing, HPMC powder is slowly added through a metering funnel to prevent clumping. The waterglass solution is added in controlled amounts using a liquid flow meter to ensure accurate mixing. The mixer is installed at a temporary mixing station near the tunnel to facilitate timely transportation of the slurry to the tunnel face. Under conditions of high crack density (N ≥ 25 cracks / meter) or high water pressure (P ≥ 0.25 MPa), HPMC's polymer chains form a network structure within the slurry, adsorbing onto the surfaces of cement particles and filling the cracks, thereby improving the slurry's cohesiveness and resistance to water erosion. For example, when N = 28 cracks / meter, increasing the HPMC dosage can increase the slurry's initial viscosity from 150 mPa·s to over 200 mPa·s, slowing slurry loss in highly permeable channels. At P = 0.3 MPa, HPMC and water glass work synergistically to shorten the slurry's initial setting time by 10-15 minutes, reducing dilution caused by high-pressure water. During construction, adjusting the HPMC dosage can ensure that the slurry maintains appropriate injectability and gelling properties under varying geological conditions, ensuring effective grouting. This example addresses the issues of poor slurry stability and susceptibility to leakage in conditions of high fracture density or high water pressure by introducing hydroxypropyl methylcellulose and establishing a correlation mechanism with geological parameters. HPMC's viscosity-increasing, water-retaining, and coagulation-accelerating properties effectively improve the slurry's workability in complex geological environments, enhancing its adhesion to fracture walls and reducing groundwater interference with the grouting process. This enhances the environmental compatibility of the composite grouting material, ensures the density and impermeability of the reinforced structure, and provides reliable stratum reinforcement for TBMs traversing fault fracture zones.

[0055] In one embodiment of the present invention, preferably, the pressure control in the pressure-stabilized osmosis stage adopts dynamic feedback regulation, including: During the steady-pressure infiltration stage, the slurry diffusion radius R is monitored in real time by a fiber optic sensor pre-buried in the grouting hole. When R is less than 0.8L, the grouting pressure is increased at a rate of 0.1MPa / min to an upper limit of 2.5MPa; when R is greater than or equal to 1.2L, the grouting pressure is decreased at a rate of 0.2MPa / min to 2.0MPa. The calculation formula of the diffusion radius R is: , where V is the cumulative grouting volume, N is the crack density, δ is the average crack width and δ = 0.1N −0.6 .

[0056] In this embodiment, during the pressure-stabilized infiltration stage, the slurry diffusion radius R is monitored in real time by an optical fiber sensor pre-buried in the grouting hole. The optical fiber sensor can be a common distributed optical fiber sensor on the market. Its probe is installed at the bottom of the grouting hole and extends upward along the hole wall to sense the changes in physical parameters during the slurry diffusion process. Two thresholds are set: when R < 0.8L, it is determined that the slurry diffusion is insufficient and the grouting pressure needs to be increased; when R ≥ 1.2L, it is determined that the slurry diffusion is excessive and the grouting pressure needs to be reduced. L is the width of the broken zone in meters. For example, if L = 5 meters, the pressure is increased when R < 4 meters, and the pressure is reduced when R ≥ 6 meters. When it is monitored that R is less than 0.8L, the grouting pressure increases at a rate of 0.1MPa / minute until it reaches the upper limit of 2.5MPa. For example, if the initial pressure is 2.0MPa and R = 3.5 meters (less than 4 meters), the pressure is increased by 0.1MPa per minute, and after 5 minutes the pressure reaches 2.5MPa. When R ≥ 1.2L, the grouting pressure decreases at a rate of 0.2MPa / minute until it drops to 2.0MPa. For example, when R = 6.5 meters (≥ 6 meters) and the current pressure is 2.5MPa, the pressure is reduced by 0.2MPa per minute, and after 2.5 minutes the pressure drops to 2.0MPa. Pressure regulation is achieved through the pressure regulating valve installed on the grouting pump. The regulating valve automatically adjusts the opening according to the feedback signal from the optical fiber sensor to control the grouting pressure. According to the formula for calculating the slurry diffusion radius R, V is the cumulative grouting volume (cubic meters), N is the crack density (cracks / cubic meter), δ is the average crack width (meters), and δ = 0.1N - 0.6. When V = 2 cubic meters and N = 20 cracks / cubic meter, δ = 0.1 × 20 - 0.6 = 1.4 meters, resulting in R ≈ 0.15 meters. The calculation process can be performed using an industrial computer installed on-site. The computer connects the fiber optic sensor and the grouting pump, collects data in real time, performs calculations, and sends pressure adjustment commands to the grouting pump based on the calculation results, forming a closed-loop feedback control system to ensure uniform slurry diffusion within the designed range. This embodiment addresses the blind pressure control issues inherent in traditional pressure-stabilized infiltration phases by establishing a dynamic feedback mechanism for grouting pressure based on the slurry diffusion radius. Fiber optic sensors monitor diffusion in real time, and combined with calculation formulas and threshold settings, automatic pressure adjustment is achieved. This prevents problems such as uneven slurry diffusion, surrounding rock damage, or insufficient grouting caused by improper pressure, improving grouting efficiency and reinforcement quality, and ensuring the reliability and stability of reinforcement in fault fracture zones during TBM construction.

[0057] In one embodiment of the present invention, preferably, a transition layer is provided between the cement-silicon dioxide crystal layer and the reinforcement layer, and the transition layer is formed by: During the filling phase of the outermost grouting holes in step 4), short carbon fiber filaments accounting for 5-8% of the weight of the ultrafine cement are added to the filling slurry, and the filling slurry is injected into the range of 0.3-0.5 m from the inner edge of the cement-silicon dioxide crystal layer through a directional grouting pipe, while applying a 0.3-0.5 T axial magnetic field; the grouting outlet end of the directional grouting pipe is 0.2-0.3 m away from the crystal layer-flexible layer interface, and the fiber length of the short carbon fiber filaments is 6-8 mm and the diameter is 15-20 μm.

[0058] In this embodiment, during the filling phase of the outermost grouting hole in step 4), carbon fiber filaments accounting for 5-8% of the weight of ultrafine cement are added to the filling slurry. The carbon fiber filaments can be selected from the common polyacrylonitrile-based chopped carbon fibers on the market, with a fiber length of 6-8mm and a diameter of 15-20μm. After being accurately weighed using a measuring scale, they are added to the slurry mixer and mixed with the filling slurry (the composite grouting material with the same composition as in step 2) for 2-3 minutes to ensure that the filaments are evenly dispersed. A directional grouting pipe is used for filling. The grouting pipe can be a steel flower pipe with a diversion hole. The outlet end is installed in the grouting hole at a position 0.3-0.5m away from the inner edge of the cement-silica crystal layer. The slurry containing carbon fiber filaments is injected into this area at a pressure of 1.8-2.0MPa using a grouting pump to form a transition layer filling range.

[0059] A permanent magnet array, typically made of neodymium iron boron (NdFeB) blocks, is coaxially arranged within the grouting hole. These magnets are evenly spaced along the outer wall of the grouting tube, with spacing of 20-30 mm between adjacent blocks. The surface magnetic flux density of the magnets is 0.4-0.6 T, and the magnetic field is oriented parallel to the tunnel axis. The magnets are secured to the outside of the grouting tube via slots and lowered into the hole along with the tube, positioned within the designed transition zone. During the grouting process, the magnetic field intensity is controlled in two stages: before initial setting (slurry viscosity <150 mPa·s), the magnetic field intensity is set to 0.5 T for 3-5 minutes to align the carbon fiber filaments along the magnetic field lines. During the initial setting phase (slurry viscosity reaches 150-300 mPa·s), the magnetic field intensity is reduced to 0.3 T for 1-2 minutes to stabilize the fiber orientation and avoid disrupting the slurry's solidification. The outlet end of the directional grouting pipe is 0.2-0.3m away from the interface between the crystal layer and the flexible layer, ensuring that the grouting liquid can effectively penetrate into the gap inside the crystal layer. Under the action of the magnetic field, the ferromagnetic characteristics of the carbon fiber staples cause them to align along the axial magnetic field direction, forming a fiber network parallel to the tunnel axis. For example, when the magnetic field strength is 0.5T, the orientation degree of the staples can reach more than 70%, significantly enhancing the tensile strength and shear resistance of the transition layer. After the grouting is completed, the permanent magnet array is pulled out together with the grouting pipe and can be reused. This process forms a transition structure with a certain flexibility between the crystal layer and the reinforcement layer through the dual effects of magnetic field orientation and fiber reinforcement, thereby alleviating interface stress concentration. This embodiment addresses the poor interface transition and cracking issues of traditional reinforcement structures, often seen between the crystallized layer and the reinforcement layer, by adding carbon fiber staples to the refill slurry and applying an axial magnetic field. The carbon fibers' bridging effect and magnetic field-oriented alignment enhance interlayer bond strength. Staged magnetic field control ensures stable fiber orientation without affecting slurry solidification, creating a "rigid and flexible" composite structure. This enhances the overall toughness and deformation resistance of the reinforcement system, effectively suppresses interfacial cracking caused by fault creep or construction disturbances, and improves long-term stability.

[0060] In one embodiment of the present invention, preferably, the method for applying the 0.3-0.5 T axial magnetic field is: A permanent magnet array is coaxially arranged in the grouting hole. The permanent magnet array is composed of NdFeB magnet blocks uniformly distributed along the circumference of the outer wall of the grouting pipe. The spacing between adjacent magnet blocks is 20-30 mm. The magnetic flux density on the surface of the magnet blocks is 0.4-0.6 T, and the magnetic field direction is parallel to the tunnel axis. The magnetic field intensity is regulated in two stages during the grouting process: Before initial coagulation, set the magnetic field strength to 0.5T and continue for 3-5 minutes; The magnetic field strength is set to 0.3 T and maintained for 1-2 minutes in the initial setting stage, when the slurry viscosity reaches 150-300 mPa·s.

[0061] In this embodiment, a permanent magnet array is coaxially arranged in the grouting hole to apply an axial magnetic field. The permanent magnet can be a neodymium iron boron magnet, which has stable magnetic properties and is reusable. The magnets are evenly distributed along the circumference of the outer wall of the grouting pipe, the spacing between adjacent magnets is 20-30mm, the magnetic flux density on the surface of the magnets is 0.4-0.6T, and the direction of the magnetic field is parallel to the axis of the tunnel. The permanent magnet is fixed to the outside of the grouting pipe through an annular groove. The spacing between the grooves is consistent with the spacing between the magnets to ensure that the magnets are accurately positioned on the grouting pipe. When the grouting pipe is lowered into the hole, the permanent magnet array corresponds to the transition layer formation area (i.e., the inner edge of the cement-silica crystal layer within 0.3-0.5m), ensuring that the magnetic field acts on the key position of the carbon fiber short filament distribution. During the grouting process, the magnetic field intensity is controlled in two stages based on the slurry's solidification state. Before initial setting (slurry viscosity <150 mPa·s), the magnetic field intensity is set to 0.5 T for 3-5 minutes. During this period, the slurry is highly fluid, and the strong magnetic field causes the carbon fiber filaments to rapidly align along the magnetic field, forming an ordered fiber network. When the slurry viscosity reaches 150-300 mPa·s (initial setting), the magnetic field intensity is adjusted to 0.3 T and maintained for 1-2 minutes. This weak magnetic field essentially fixes the fiber orientation while preventing the continued presence of a strong magnetic field from interfering with the slurry's normal gelation process. The magnetic field intensity is adjusted by switching the density of the permanent magnet array or using an adjustable magnetic yoke. The magnetic flux density on the surface of the magnet block can be measured on-site using a gaussmeter to ensure that the parameters meet design requirements. During the refilling phase of the outermost grouting hole, a directional grouting pipe equipped with a permanent magnet array is first lowered into the hole, with the magnets aligned with the designed transition layer area. The grouting pump is then activated to inject the refilling slurry containing carbon fiber filaments, while the magnetic field generator (such as the magnetic control component included with the permanent magnet array) is simultaneously activated. During the high magnetic field intensity phase prior to initial setting, the filaments in the slurry are rapidly oriented by the magnetic force, forming a fiber skeleton along the tunnel axis. After the initial setting phase, the magnetic field intensity is reduced to maintain a stable fiber orientation until the slurry viscosity reaches the initial setting standard. After grouting is completed, the magnetic field device and grouting pipe are disassembled in sequence. The magnets can be removed and recovered from the grouting pipe using specialized tools and reused for subsequent grouting hole construction. This process achieves synergy between the directional arrangement of the carbon fiber filaments and the slurry solidification process through staged magnetic field control, enhancing the reinforcement effect of the transition layer. This embodiment solves the problem of poor fiber orientation or interference with slurry solidification in traditional magnetic field application methods by optimizing the permanent magnet array layout and regulating the magnetic field intensity in stages. A strong magnetic field ensures rapid orientation of the carbon fiber filaments, while a weak magnetic field maintains orientation stability to avoid affecting the normal coagulation time of the slurry. The high magnetic flux density and circumferentially uniform distribution design of the NdFeB magnet block allow the magnetic field to act evenly on the transition layer area, significantly improving the orientation degree and interlayer bonding performance of the carbon fiber filaments, thereby enhancing the transition effect between the cement-silica crystalline layer and the nano-silica modified reinforcement layer, and improving the overall crack resistance and mechanical property uniformity of the composite reinforcement structure.

[0062] A reinforcement method for a fault fracture zone during TBM construction. When a tunnel project uses TBM construction to pass through a fault fracture zone, the following reinforcement method is implemented: 1. Geological parameter collection and grouting range determination The width of the fracture zone was obtained by geological radar detection, which was L=8m; The core sampling results showed that the crack density N = 22 / m, the groundwater pressure P = 0.25 MPa, and the uniaxial compressive strength of the surrounding rock Rc = 28 MPa; Calculate the initial grouting range: Since P = 0.25 MPa (0.1 MPa < P ≤ 0.3 MPa), the horizontal width = 1.8 × 8 + 0.3 × 22 = 20.4 m, and the vertical depth = 1.5 × 8 = 12 m; Introducing Rc correction: Rc=28MPa≤30MPa, the horizontal width is corrected to 20.4×(1+0.02×(30-28))=21.22m, and the vertical depth is corrected to 12×(1+0.015×(30-28))=12.36m, both rounded up to 21.5m and 12.5m; A three-dimensional geological model was constructed using the SKUA-GOCAD platform. Inputs were L = 8 m, N = 22, and P = 0.25 MPa. A wedge-shaped grouting area was generated with the top surface fitting the hanging wall of the fault and the bottom surface 13.75 m (1.1 × 12.5 m) from the footwall. The thickness of the gradient zone decreased by 2.0 m / m (0.16 × 12.5 m). Output the coordinates of the grouting hole group and the angle γ=90°-α±5° (α is the fault dip angle of 35°).

[0063] 2. Preparation of composite grouting materials Basic mix ratio: 60 parts of ultrafine cement (particle size 6μm), 4 parts of nano-silica, 13 parts of water glass solution (modulus 2.7, Baume 39°Bé), 23 parts of water; Since N=22≥20 and P=0.25≥0.2MPa, adjust the nano-silica to 4.5 parts, the water glass modulus to 2.7, and the Baume degree to 39°Bé; Add hydroxypropyl methylcellulose: Q = 0.3 + 0.02 × (22-15) + 0.015 × (0.25 / 0.1) = 0.3 + 0.14 + 0.0375 = 0.4775 parts → take 0.5 parts.

[0064] 3. Segmented retreat grouting construction Grouting holes are arranged every 2.5m along the excavation direction, with 8 holes in each group (central angle 45°), and the drilling depth is H = 1.2 × 8 + 0.1 × 22 = 11.8m (≤ 1.5 × 8 = 12m); Initial grouting stage: pressure 1.6MPa, grouting to 50% of the design volume; Steady pressure penetration stage: the pressure rises to 2.1MPa, and the diffusion radius is monitored in real time Because R = 11.8 m > 1.2L = 9.6 m, the pressure regulation mechanism is triggered, and the grouting pressure is reduced from 2.1 MPa to 2.0 MPa at a rate of 0.2 MPa / min to ensure that the slurry diffusion range is controlled within the design range; The backward grouting sequence is: grouting from the far end to the near end of the fault, with an interval of 35 minutes between adjacent holes.

[0065] 4. Layered recharge and transition layer formation Outermost hole: 2.3MPa grouting to 80% of the design volume. After the viscosity reaches 250mPa·s, 1.9MPa grouting to 110%; Middle hole: 1.9MPa grouting to 80%, after 70% gel, 1.7MPa refilling to 105%; Innermost hole: 1.7MPa grouting to 90%, after the viscosity reaches 170mPa·s, 1.4MPa grouting to 100%; Adjustment of injection volume: Because N=22≥15, the injection volume is increased by 7%; Transition layer construction: When filling the outermost hole, add 5% carbon fiber short filaments (7mm long, 18μm diameter) and inject them into the range of 0.4m from the inner edge of the crystallization layer through a directional grouting pipe (the outlet is 0.25m away from the interface). In the pre-initial setting stage (slurry viscosity ≤150mPa·s), a 0.5T magnetic field is applied for 4 minutes; in the initial setting stage (when the viscosity reaches 200mPa·s), the magnetic field is switched to 0.3T and maintained for 1.5 minutes. The fiber circumferential distribution density is 130 fibers / cm².

[0066] 5. Composite reinforcement structure forming Outer crystal layer: compressive strength 28MPa, permeability coefficient 9×10⁻ 9 m / s; Transition layer: contains 6% carbon fiber, shear strength 8.5MPa; Inner flexible layer: elastic modulus 4.2 GPa, tensile strain 1.1%.

[0067] The grouting body completely wrapped the fault fracture zone, and the TBM excavation efficiency reached 6.5m / day, which is about 40-60% higher than the traditional construction method in the same formation, without any landslide or leakage accidents.

[0068] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and exemplary embodiments. They can be applied to a variety of fields suitable for the embodiments of the present invention. Those skilled in the art will readily realize further modifications. Therefore, without departing from the general concept defined by the claims and their equivalents, the embodiments of the present invention are not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for reinforcing a fault zone during TBM construction, characterized in that: The steps include: 1) Determine the scope of grouting reinforcement based on the geological parameters of the fault fracture zone, including fracture zone width, degree of fissure development, and groundwater conditions; 2) preparing a composite grouting material according to the geological parameters in step 1), wherein the composite grouting material comprises, by weight, 55-65 parts of ultrafine cement with a particle size of 5-10 μm, 3-5 parts of nano-silicon dioxide, 10-15 parts of a water glass solution, and 15-32 parts of water, wherein the water glass solution has a modulus of 2.4-2.8 and a Baume degree of 35-40°Bé; When the degree of development of the cracks is ≥20 / m, the amount of nano-silica used is 4-5 parts and the modulus of the water glass solution is adjusted to 2.6-2.8; when the groundwater pressure is ≥0.2 MPa, the Baume degree of the water glass solution is adjusted to 38-40°Bé and the particle size of the ultrafine cement is adjusted to 5-7 μm; 3) Using a segmented backward grouting process, grouting hole groups are set up every 2-3m along the TBM excavation direction. Each group contains 6-8 radial grouting holes evenly distributed along the circumference of the tunnel. The grouting pressure is controlled at 1.5-2.5MPa. 4) When grouting, first perform high-pressure grouting on the outermost grouting holes to form a closed curtain, and then perform layered grouting on the inner grouting holes in sequence. Stop grouting when the grouting volume of each grouting hole reaches 80% of the design value. After the grouting liquid has initially set, replenish grouting to the design value. 5) After grouting is completed, a composite reinforcement structure with a gradual change from the outside to the inside is formed. The outer layer is a cement-silica crystal layer generated by the reaction of water glass and ultrafine cement, and the inner layer is a reinforcement layer modified by nano-silica.

2. The method for reinforcing a fault zone during TBM construction according to claim 1, characterized in that: The method for determining the grouting reinforcement range in step 1) includes the following steps: The width of the fracture zone L was obtained by geological radar detection, the number of cracks per meter in the core samples was used to characterize the degree of crack development, and the groundwater pressure P was measured by borehole water pressure testing. When P≤0.1MPa, the grouting reinforcement range has a horizontal width of 1.5L+0.2N and a vertical depth of 1.2L; When 0.1MPa<P≤0.3MPa, the lateral width is 1.8L+0.3N and the longitudinal depth is 1.5L.

3. The method for reinforcing a fault zone during TBM construction according to claim 2, characterized in that: In step 1), the uniaxial compressive strength Rc of the surrounding rock was measured by drilling core samples. When the uniaxial compressive strength of the surrounding rock mass Rc is less than or equal to 30 MPa, the horizontal width is corrected to (1.5L + 0.2N) × (1 + 0.02 × (30-Rc)), and the vertical depth is corrected to 1.2L × (1 + 0.015 × (30-Rc)); When the uniaxial compressive strength of the surrounding rock mass Rc>30MPa, the transverse width is corrected to (1.8L+0.3N)×(1-0.01×(Rc-30)), and the longitudinal depth is corrected to 1.5L×(1-0.008×(Rc-30)).

4. The method for reinforcing a fault zone during TBM construction according to claim 2, wherein: The step 1) further includes: The calculation result of the grouting reinforcement range is spatially mapped using a three-dimensional geological model to generate a wedge-shaped grouting area that matches the strike of the fault fracture zone. The method for spatial mapping the three-dimensional geological model includes: The fracture zone width L, number of fissures N, and groundwater pressure P are input into a three-dimensional geological model built on the SKUA-GOCAD platform. The three-dimensional geological model is based on rock mass structure data from drill core samples and uses the Kriging interpolation algorithm to generate the three-dimensional spatial distribution of the fault fracture zone. Based on the calculation results of the lateral width and longitudinal depth, a hexahedral grid is divided along the tunnel axis in the three-dimensional geological model with a unit of 0.5 m, and the lateral width value is mapped to the radial reinforcement thickness of each grid unit; Based on the dip angle α and inclination β of the fault fracture zone, a wedge-shaped grouting area is generated using the geological interface fitting module in the three-dimensional geological model. The top boundary of the wedge-shaped grouting area is fitted to the hanging wall interface of the fault fracture zone using the least squares method, and the bottom boundary is parallel to the footwall interface and the vertical distance from the footwall interface is 1.1-1.3 times the longitudinal depth. A thickness gradient zone is set between the wedge-shaped grouting area and the tunnel contour line. The thickness of the gradient zone decreases according to a linear function from the bottom surface of the wedge-shaped grouting area to the tunnel contour line, and the decreasing gradient is 0.15-0.25 times the longitudinal depth per meter; the three-dimensional geological model outputs the spatial coordinates and drilling angles of the grouting hole group through a finite element meshing algorithm, wherein the angle γ between the axial direction of the grouting hole group and the strike of the fault fracture zone is calculated by vector projection as γ=90°-α±5°.

5. The method for reinforcing a fault zone during TBM construction according to claim 1, characterized in that: The segmented retreat grouting process of step 3) includes the following steps: Grouting hole groups are set up every 2-3m along the TBM excavation direction. The 6-8 radial grouting holes in each grouting hole group are evenly distributed along the circumference of the tunnel. The central angle between adjacent grouting holes is 45°-60°. The drilling depth H of the radial grouting holes satisfies H=1.2L+0.1N and H≤1.5L. When H>1.5L, H=1.5L, where L is the width of the fracture zone and N is the degree of fracture development. The pressure in the initial grouting stage is 1.5-1.8 MPa and continues until the grouting volume reaches 50% of the design value; The pressure in the steady-pressure infiltration stage is 2.0-2.2 MPa and continues until the grouting volume reaches 80% of the design value; The construction sequence of the grouting hole group is: backward grouting is carried out from the far end to the near end of the broken zone along the excavation direction, and grouting is performed at intervals of 2 holes in the same circumferential section, and the time interval between grouting of adjacent holes is greater than 30 minutes.

6. The method for reinforcing a fault zone during TBM construction according to claim 1, characterized in that: The layered grouting in step 4) includes the following steps: The outermost grouting hole is continuously grouted to 80% of the design value at a grouting pressure of 2.3-2.5 MPa. After the slurry viscosity reaches 200-300 mPa·s, additional grouting is performed at a pressure of 1.8-2.0 MPa to 105-110% of the design value. The middle layer grouting holes are grouting to 80% of the design value at a grouting pressure of 1.8-2.0 MPa. After the initial setting time reaches 70% of its gel time, grouting is performed at a pressure of 1.5-1.8 MPa to 100-105% of the design value. The innermost grouting hole is grouting to 90% of the design value at a grouting pressure of 1.5-1.8 MPa. When the slurry viscosity reaches 150-180 mPa·s, it is grouting to the design value at a pressure of 1.2-1.5 MPa. The injection volume is adjusted according to the degree of crack development N. When N≥15 cracks / meter, the injection volume is increased by 5-8% of the design value.

7. The method for reinforcing a fault zone during TBM construction according to claim 1, characterized in that: The composite grouting material in step 2) further comprises: 0.3-0.8 parts by weight of hydroxypropyl methylcellulose, wherein: When the crack development degree N ≥ 25 / m, the amount of hydroxypropyl methylcellulose added is 0.5-0.8 parts; When the groundwater pressure P≥0.25MPa, the amount of hydroxypropyl methylcellulose added is increased to 0.6-0.8 parts; The corresponding relationship between the addition amount Q of the hydroxypropyl methylcellulose and the grouting pressure P is: Q=0.3+0.02×(N-15)+0.015×(P / 0.1).

8. The method for reinforcing a fault zone during TBM construction according to claim 5, characterized in that: The pressure control in the steady-pressure osmosis stage adopts dynamic feedback regulation, including: During the steady-pressure infiltration stage, the slurry diffusion radius R is monitored in real time by a fiber optic sensor pre-buried in the grouting hole. When R is less than 0.8L, the grouting pressure increases at a rate of 0.1MPa / minute to an upper limit of 2.5MPa; when R is greater than or equal to 1.2L, the grouting pressure decreases at a rate of 0.2MPa / minute to 2.0MPa.

9. The method for reinforcing a fault zone during TBM construction according to claim 1, characterized in that: A transition layer is further provided between the cement-silicon dioxide crystal layer and the reinforcement layer, and the transition layer is formed by: During the filling phase of the outermost grouting holes in step 4), short carbon fiber filaments accounting for 5-8% of the weight of the ultrafine cement are added to the filling slurry, and the filling slurry is injected into the range of 0.3-0.5 m from the inner edge of the cement-silicon dioxide crystal layer through a directional grouting pipe, while applying a 0.3-0.5 T axial magnetic field; the grouting outlet end of the directional grouting pipe is 0.2-0.3 m away from the crystal layer-flexible layer interface, and the fiber length of the short carbon fiber filaments is 6-8 mm and the diameter is 15-20 μm.

10. The method for reinforcing a fault zone during TBM construction according to claim 9, characterized in that: The method for applying the 0.3-0.5T axial magnetic field is: A permanent magnet array is coaxially arranged in the grouting hole. The permanent magnet array is composed of NdFeB magnet blocks uniformly distributed along the circumference of the outer wall of the grouting pipe. The spacing between adjacent magnet blocks is 20-30 mm. The magnetic flux density on the surface of the magnet blocks is 0.4-0.6 T, and the magnetic field direction is parallel to the tunnel axis. The magnetic field intensity is regulated in two stages during the grouting process: Before initial coagulation, set the magnetic field strength to 0.5T and continue for 3-5 minutes; The magnetic field strength is set to 0.3 T and maintained for 1-2 minutes in the initial setting stage, when the slurry viscosity reaches 150-300 mPa·s.

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