Control method for large-diameter and large-gradient super-shallow-buried shield launching in volcanic ash stratum

Abstract

The application discloses a control method for large-diameter and large-gradient super-shallow-buried shield launching in a volcanic ash stratum, and the method comprises the following steps: step S1, calculating a stratum reinforcement range based on geological parameters, and reinforcing the stratum at the launching end by directional grouting; step S2, installing a multi-stage sealing device at a shield launching opening, and verifying the sealing property before the opening is broken; step S3, dynamically adjusting the thrust, torque and grouting parameters when the shield is excavated, and controlling the surface settlement to be less than or equal to 3 mm; and step S4, monitoring the shield posture and stratum deformation in real time, and adjusting the construction parameters through data feedback closed-loop regulation. The technical scheme aims to improve the reliability when a large-diameter, large-gradient and shallow-buried tunnel is constructed in a volcanic ash stratum.

Description

Technical Field

[0001] This invention relates to the field of shield tunnel engineering technology, and in particular to a method for controlling the launch of large-diameter, steep-slope, ultra-shallow buried shields in volcanic ash strata. Background Technology

[0002] With the rapid development of urban underground space development, the demand for large-diameter shield tunnels in complex geological formations is increasing. Volcanic ash formations, as a typical adverse geological condition, are characterized by loose structure, high porosity, and strong permeability. Launching large-diameter (diameter > 8 m), steep (slope > 5%), and ultra-shallow (depth < 1 tunnel diameter) shield tunnels in these formations presents numerous technical challenges: First, the poor self-stability of the strata leads to a surge in collapse accidents; second, controlling surface settlement under ultra-shallow conditions is difficult; and third, controlling the shield's attitude under steep slope conditions is challenging.

[0003] Therefore, it is urgent to develop a set of control methods for the launch of large-diameter, steep-slope, ultra-shallow buried shield tunnels in volcanic ash strata to ensure construction safety. Summary of the Invention

[0004] The main objective of this invention is to propose a method for controlling the launch of large-diameter, steep-slope, and shallow-buried shield tunnels in volcanic ash formations, aiming to improve the reliability of tunnels with large diameter, steep slope, and shallow burial in volcanic ash formations.

[0005] To achieve the above objectives, this invention proposes a method for controlling the launch of large-diameter, steep-slope, ultra-shallow-buried shield tunnels in volcanic ash strata. This method includes the following steps:

[0006] Step S1: Calculate the reinforcement range of the strata based on geological parameters, and reinforce the strata at the starting point by directional grouting;

[0007] Step S2: Install a multi-stage sealing device at the tunnel entrance and verify its sealing performance before the tunnel portal is breached;

[0008] Step S3: During shield tunneling, dynamically adjust the thrust, torque, and grouting parameters to control surface settlement ≤3mm;

[0009] Step S4: Monitor the shield attitude and ground deformation in real time, and adjust the construction parameters through data feedback closed loop.

[0010] In some embodiments, the formation reinforcement range is calculated using the following formula:

[0011] Among them, L str Where D is the length of the reinforced zone, β is the diameter of the shield, H is the starting slope angle, and C is the tunnel depth. u For the undrained shear strength of volcanic ash, Sr is the porosity correction factor for volcanic ash, and k is the safety factor.

[0012] In some embodiments, the directional grouting uses cement grout and / or water glass, and the grouting pressure is controlled according to the following formula:

[0013] Among them, P inj For the maximum grouting pressure, σ v For vertical earth pressure, σ h ρ is the horizontal earth pressure, K0 is the coefficient of earth pressure at rest, μ is the grout viscosity, v is the grouting rate, and d is the grouting fluid viscosity. p α is the equivalent diameter of the grouting hole, and α is the correction factor for the volcanic ash formation.

[0014] In some embodiments, the sealing device includes a wire brush sealing ring, an expandable rubber sealing ring, and an emergency airbag sealing layer arranged sequentially from the outside to the inside.

[0015] In some embodiments, a pressure balance zone, such as bentonite grout, is formed in the gap of the sealing device before the portal is broken, the pressure value of which is 1.05 to 1.15 times the static earth pressure.

[0016] In some embodiments, the thrust during shield tunneling is dynamically adjusted and controlled according to the following formula:

[0017] Among them, F t For real-time thrust, γ is the effective bulk density of volcanic ash, and K is the effective bulk density of volcanic ash. p For passive earth pressure coefficient, F add Add resistance to the slope, L con This is the contact length between the shield and the ground.

[0018] In some embodiments, the slope-added resistance F add Calculate using the following formula:

[0019] Where W is the weight of the tunnel boring machine, θ is the real-time tunneling slope angle, and fr is the coefficient of friction of volcanic ash.

[0020] In some embodiments, the real-time monitoring of the shield attitude and ground deformation is achieved by using at least two of the following: a fiber optic grating sensor matrix, a distributed strain sensing fiber, and a three-dimensional laser scanner.

[0021] In some embodiments, when the shield tunneling attitude is monitored in real time, if the shield pitch angle deviation is detected to be >0.3°, an attitude correction procedure is initiated. The attitude correction procedure includes the following steps:

[0022] Adjust the thrust differential between zones to 120%~150% of the design value;

[0023] Inject a high molecular weight polymer drag-reducing agent at the lower side cutter head position;

[0024] Synchronous grouting was carried out using fast-setting grout.

[0025] In some embodiments, synchronous grouting in the initial stage adopts an intermittent pulse grouting mode, and the grouting frequency f and the advancing speed v satisfy the following formula:

[0026] Among them, S t is the density coefficient of volcanic ash, and e is the natural constant.

[0027] The technical solution of this invention systematically optimizes the entire shield tunneling launch process through geological parameterization of strata reinforcement, configuration of multi-level sealing devices, dynamic adjustment of tunneling parameters, and real-time monitoring closed-loop control. It effectively solves the problems of collapse, sand inrush, settlement, and axis instability during the launch of shield tunnels on steep slopes in volcanic ash strata. It has the advantages of significantly reducing the risk of strata collapse, completely suppressing water and sand inrush, accurately controlling surface settlement, and ensuring stable and reliable shield attitude. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0029] Figure 1 The flowchart is a method for controlling the launch of large-diameter, steep-slope, ultra-shallow buried shield tunnels in volcanic ash strata, according to an embodiment of the present invention.

[0030] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0033] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text implies three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0034] Please see Figure 1 This invention proposes a method for controlling the launch of large-diameter, steep-slope, ultra-shallow-buried shield tunnels in volcanic ash strata. This method includes the following steps: Step S1: Calculate the stratum reinforcement range based on geological parameters and reinforce the stratum at the launch end using directional grouting; Step S2: Install a multi-stage sealing device at the shield launch portal and verify its sealing performance before portal breach; Step S3: Dynamically adjust thrust, torque, and grouting parameters during shield tunneling to control surface settlement ≤3mm; Step S4: Monitor shield attitude and stratum deformation in real time and adjust construction parameters through data feedback closed-loop control.

[0035] In existing technologies, urban underground space development faces unique challenges posed by volcanic ash strata. These strata are loosely structured and highly porosilicated, making traditional shield tunneling techniques ill-suited for the demands of large-diameter tunnel construction. Conventional stratum reinforcement methods suffer from calculation errors regarding the reinforcement area, leading to localized collapses during the initial stage. Portal sealing devices are prone to leakage failure under high pressure differential conditions, and conventional grouting processes are ill-suited to the highly permeable geological characteristics. Construction parameter control relies on experience-based judgment and lacks a real-time feedback mechanism, significantly increasing the risk of attitude instability during steep excavation.

[0036] To address the aforementioned issues and the insufficient accuracy in calculating the reinforcement range, the research team discovered that traditional empirical formulas do not consider the influence of volcanic ash porosity on the ductility of the reinforced zone. In the failure analysis of the sealing device, it was found that a single-stage sealing structure is insufficient to adapt to sudden pressure changes under ultra-shallow burial conditions. Through analysis of the coupling relationship between shield thrust and ground deformation, it was recognized that static parameter settings cannot meet the dynamic balance requirements during steep slope tunneling. Based on multi-source monitoring data fusion technology, the necessity of establishing a real-time feedback and adjustment mechanism for construction parameters was proposed.

[0037] Therefore, this application proposes a technical solution including the following steps: Step S1, calculate the stratum reinforcement range based on geological parameters, and reinforce the stratum at the starting end by directional grouting; Step S2, install a multi-stage sealing device at the shield tunneling portal and verify its sealing performance before the portal is breached; Step S3, dynamically adjust the thrust, torque, and grouting parameters during shield tunneling to control surface settlement; Step S4, monitor the shield attitude and stratum deformation in real time, and adjust the construction parameters through data feedback closed-loop adjustment.

[0038] The calculation of the stratum reinforcement range refers to determining the grouting reinforcement area based on the physical characteristics of the volcanic ash strata. This can be achieved using geological exploration data combined with numerical simulation methods. This step ensures that the reinforcement area matches the mechanical properties of the strata. Multi-stage sealing device installation refers to setting up multiple sealing structure layers, such as using a combination of sealing rings of different materials. This structure can absorb pressure fluctuations in stages. Dynamic parameter adjustment refers to correcting construction parameters according to real-time changes in working conditions. This can be achieved through an automatic control system, maintaining mechanical balance during tunneling. Data feedback closed-loop regulation refers to establishing a real-time correlation between monitoring data and construction parameters, for example, using a sensor network to collect data. This mechanism enables precise control of the construction process.

[0039] Specifically, by collecting porosity and shear strength parameters of the volcanic ash strata, a calculation model for the reinforcement range was established to determine the optimal grouting area. Different sealing components were sequentially installed at the tunnel portal structure, and the pressure-bearing capacity of the sealing system was verified through pressure testing. During tunnel boring machine (TBM) advancement, the output parameters of the advancement system were adjusted in real time based on the earth pressure balance. Distributed monitoring equipment was deployed to collect stratum deformation data, and the settlement was fed back to the grouting control system to adjust the grout mix ratio. When the monitoring data exceeded a set threshold, a parameter correction program was automatically triggered to reallocate the cutterhead torque.

[0040] Compared to existing technologies, traditional methods using uniform thickness grouting for reinforcement are prone to material waste. This solution achieves precise reinforcement through geological parameter calculations. Conventional single-stage sealing structures are susceptible to failure under pressure fluctuations; this solution uses a multi-stage sealing device to create a progressive sealing effect. Empirical parameter settings are difficult to adapt to complex working conditions; this solution's dynamic adjustment mechanism improves the controllability of the construction process. Manual monitoring suffers from data lag; this solution's closed-loop feedback system achieves millimeter-level settlement control.

[0041] Through the above technical solutions, this application effectively prevents collapse accidents during the initial stage of volcanic ash formation and ensures the reliability of the tunnel portal sealing system under high pressure differential conditions. Dynamic parameter adjustments maintain earth pressure balance during shield tunneling, reducing the risk of attitude deviation during steep inclines. A real-time data feedback mechanism enables proactive control of surface settlement, avoiding damage to ground structures during ultra-shallow tunnel construction. The synergistic effect of multiple technologies significantly improves the safety and construction efficiency of shield tunneling under complex geological conditions.

[0042] In some embodiments, the formation reinforcement range is calculated using the following formula:

[0043] Among them, L str Where D is the length of the reinforced zone, β is the diameter of the shield, H is the starting slope angle, and C is the tunnel depth. u For the undrained shear strength of volcanic ash, S r is the porosity correction factor for volcanic ash, and k is the safety factor.

[0044] Reinforced zone length L str This refers to the longitudinal extension range that needs to be reinforced at the starting point of the tunnel boring machine. The specific range can be determined through geological exploration data and numerical simulation analysis to ensure that the reinforcement range covers potentially unstable areas.

[0045] The shield diameter D refers to the outer diameter of the shield machine cutterhead, which can be obtained through a laser rangefinder or mechanical measuring device, and directly affects the lateral dimension of the reinforcement range.

[0046] The starting slope angle β refers to the angle between the axis of the shield tunneling starting section and the horizontal plane. It can be measured by a total station or tilt sensor and is used to reflect the impact of steep slope conditions on the stability of the strata.

[0047] Tunnel burial depth H refers to the vertical distance from the top of the tunnel to the ground surface, which can be determined by ground-penetrating radar or borehole data, and is used to assess the earth pressure distribution under ultra-shallow burial conditions.

[0048] Volcanic ash undrained shear strength C u It refers to the shear resistance of volcanic ash formations under rapid loading conditions. Specifically, it can be determined through indoor direct shear tests or in-situ vane shear tests, and is used to characterize the strength properties of the formation.

[0049] Volcanic ash porosity correction factor S r This refers to the adjustment parameter introduced based on the influence of volcanic ash porosity on permeability and compressibility. Specifically, it can be determined through porosity testing and regression analysis of historical engineering data, and is used to correct errors in the calculation of the reinforcement range.

[0050] The safety factor k is a redundancy factor that takes into account construction uncertainties and geological variability. It can be selected according to the project risk level and geological complexity, for example, the value range is 1.2 to 1.5.

[0051] Specifically, by substituting key parameters such as shield diameter, starting slope angle, and tunnel depth into the formula, the reinforcement requirements of volcanic ash strata can be quantified. For example, as the shield diameter increases, the length of the reinforcement zone expands according to the cube root relationship, preventing strata collapse due to insufficient reinforcement; when the porosity correction coefficient increases, the formula automatically increases the reinforcement range to offset the risks posed by the permeability of volcanic ash. Thus, this method, through multi-parameter coupled calculation, accurately matches the reinforcement requirements under complex geological conditions, solving the problem of insufficient or excessive reinforcement range that often occurs in traditional empirical methods in volcanic ash strata.

[0052] Compared with existing technologies, traditional methods for calculating the reinforcement range typically rely on linear estimations based on a single parameter (such as burial depth or shield diameter), neglecting the combined effects of steep slopes, porosity, and shear strength. This proposed solution, however, introduces a cube root function and multiplication relationships with multiple parameters, incorporating stratum strength, geometric conditions, and geological characteristics into a unified model. This significantly improves the scientific rigor and adaptability of the reinforcement range calculation, making it particularly suitable for nonlinear instability problems in volcanic ash strata caused by high parameter sensitivity.

[0053] Through the above technical solutions, this application can precisely control the scope of ground reinforcement, avoiding surface subsidence or collapse accidents caused by insufficient reinforcement under ultra-shallow burial conditions, while also preventing resource waste caused by excessive reinforcement. By dynamically adapting to the characteristics of volcanic ash strata, this method effectively balances construction safety and economy, providing a reliable guarantee for the launch of large-diameter, steep-slope shield tunnels in complex geological conditions.

[0054] In some embodiments, the directional grouting uses cement grout and / or water glass, and the grouting pressure is controlled according to the following formula:

[0055] Among them, P inj For the maximum grouting pressure, σ v For vertical earth pressure, σ h ρ is the horizontal earth pressure, K0 is the coefficient of earth pressure at rest, μ is the grout viscosity, v is the grouting rate, and d is the grouting fluid viscosity. p α is the equivalent diameter of the grouting hole, and α is the correction factor for the volcanic ash formation.

[0056] Cement grout refers to a grouting material primarily composed of silicate cement. Specifically, it can be made by mixing ordinary silicate cement with water in a specific ratio to form a grout, which solidifies into a rigid solidified body. Water glass refers to a sodium silicate solution, specifically a water glass solution with a modulus of 2.4-3.0, which reacts with acidic substances to form a gel. The equivalent diameter of the grouting hole refers to the equivalent pore size calculated based on the arrangement of the grouting pipes. Specifically, it can be calculated using fluid dynamics equivalent formulas when multiple grouting pipes are arranged in parallel, and is used to characterize the equivalent size of the grout diffusion channels. The volcanic ash formation correction factor is a parameter reflecting the influence of the pore structure of volcanic ash on the permeability of the grout. Specifically, it can be determined by fitting data from laboratory permeability tests combined with field pumping tests.

[0057] Specifically, in directional grouting within volcanic ash formations, a dual-liquid grouting system alternately injects cement grout and water glass. The cement grout fills large pores, while the water glass seals small seepage channels. Grouting pressure is calculated by real-time acquisition of formation stress data, substituting vertical and horizontal earth pressures into a formula to determine the baseline pressure value, and then superimposing the grout flow resistance component to form a dynamic control threshold. When the grouting equipment detects that the pressure is approaching the calculated value, it automatically adjusts the grouting pump's discharge parameters to ensure that the actual grouting pressure remains below the formation fracturing critical value. For example, in areas with high porosity, increasing the equivalent diameter of the grouting holes can reduce the flow resistance component, preventing pressure buildup that could lead to formation disturbance.

[0058] Compared to existing technologies, traditional grouting pressure control methods only consider the static earth pressure component and do not account for the influence of grout rheological properties and grouting rate. This can easily lead to excessive pressure causing formation fracturing or insufficient grouting resulting in reinforcement failure. This solution introduces a viscosity-velocity coupling term to establish a dynamic pressure control model, which can adapt to the grouting needs of formations with different porosity structures. Existing technologies using a single grout material cannot simultaneously meet the dual requirements of pore filling and fracture sealing, while this solution employs a composite grouting system of cement grout and water glass, achieving multi-scale reinforcement effects.

[0059] Through the above technical solution, this application can precisely control the grouting pressure within a safe range, ensuring that the grout effectively fills the pores of the volcanic ash formation while avoiding damage to the formation structure due to excessive pressure. The dual-liquid grouting system can simultaneously achieve macroscopic reinforcement and microscopic sealing, significantly improving the overall stability of the formation at the starting end and creating safe operating conditions for subsequent shield tunneling. The rheological parameter introduced into the pressure control formula can effectively compensate for the flow loss of the grout in complex pore channels, ensuring uniform and reliable grouting results.

[0060] In some embodiments, the sealing device includes a wire brush sealing ring, an expandable rubber sealing ring, and an emergency airbag sealing layer arranged sequentially from the outside to the inside.

[0061] A wire brush sealing ring is a ring-shaped sealing structure formed by braiding metal wires, specifically using a cross-weaving process with stainless steel wires. The wire diameter can be, for example, 0.3 mm to 0.5 mm. Multiple layers are stacked to form a dense barrier, preventing the intrusion of ground particles. An expandable rubber sealing ring is a rubber component with water-swellable properties, specifically made of butyl rubber and water-absorbing resin composites. It expands in volume upon contact with groundwater to compensate for sealing gaps. An emergency airbag sealing layer is a polymer sealing component with a built-in inflation chamber, specifically made of polyurethane composite material. Dynamic sealing is achieved through air pressure regulation to cope with sudden pressure fluctuations.

[0062] Specifically, before the tunnel portal is breached, the wire brush sealing ring forms the first physical barrier through mechanical interlocking, preventing loose particles from the volcanic ash strata from entering the starting area. The expandable rubber sealing ring expands during tunnel boring machine (TBM) advancement by absorbing seepage water, filling sealing gaps caused by TBM attitude deviations. The emergency airbag sealing layer initiates an inflation process upon detecting abnormal pressure, forming an emergency sealing interface through airbag expansion to prevent mud and water seepage from causing ground instability.

[0063] Compared to existing technologies, traditional shield tunneling starting sealing devices typically employ a single-layer rubber curtain structure, which is prone to grout leakage under the high permeability conditions of volcanic ash formations. This solution utilizes a triple-sealing structure to create gradient protection. The wire brush sealing ring intercepts large particles, the expandable rubber sealing ring achieves dynamic adaptive sealing, and the emergency airbag sealing layer provides emergency protection. The combined effect of these three elements can adapt to complex formation pressure changes under ultra-shallow burial conditions.

[0064] Through the above technical solution, this application can effectively prevent mud and water leakage caused by the failure of the tunnel portal seal during the initial stage of shield tunneling, maintain the pressure balance of the excavation face, and reduce the risk of surface subsidence caused by seal failure. It is especially suitable for volcanic ash strata environments with high porosity and high permeability.

[0065] In some embodiments, a pressure balance zone, such as bentonite grout, is formed in the gap of the sealing device before the portal is broken, the pressure value of which is 1.05 to 1.15 times the static earth pressure.

[0066] Bentonite grout refers to a thixotropic grout with sodium-based bentonite as its main component. It can be prepared using a water-to-bentonite mass ratio of 1:8 to 1:12. Its water-swelling property allows it to fill the gaps between the sealing device and the tunnel boring machine (TBM) shell. The pressure balance zone is a ring-shaped closed area with a specific pressure threshold formed by grouting. This can be achieved through interlocking control between pressure sensors and the grouting pump, used to counteract the impact of ground pressure fluctuations on the sealing structure during TBM launch. The pressure range of 1.05 to 1.15 times refers to a dynamic control range based on measured static earth pressure values. This can be achieved by real-time acquisition of ground pressure data and feedback to the grouting system. This range prevents grout leakage while avoiding overloading of the sealing structure.

[0067] Specifically, before the concrete removal operation at the tunnel portal, bentonite grout is injected into the annular gap of the multi-stage sealing device through pre-embedded grouting pipes. The grout forms a pressure-maintaining gel layer between the sealing wire brush and the rubber ring. The pressure of this layer is maintained between 1.05 and 1.15 times the static earth pressure by a closed-loop control system. When the tunnel boring machine begins to advance, the thixotropic properties of the bentonite grout transform it into a dense, water-resistant layer under mechanical compression. Simultaneously, the pressure balance zone counteracts changes in ground pressure by adjusting the grouting volume in real time, preventing external water and soil from seeping in through the gap between the shield shell and the sealing device.

[0068] Compared to existing technologies, traditional shield tunneling starting seals rely solely on the static clamping force of mechanical seals, which can easily lead to grout leakage in highly permeable volcanic ash formations with fluctuating pore pressure. This solution constructs an adjustable pressure balance zone, ensuring that the pressure at the sealing interface is always higher than the external formation pressure, thus forming a dynamic pressure barrier.

[0069] Through the above technical solution, this application effectively solves the problem of high leakage risk at the shield tunneling starting sealing interface in volcanic ash strata. The pressure adaptive characteristics of bentonite slurry and the multi-stage sealing device work together to ensure the reliability of the tunnel portal sealing system during the shield tunneling starting stage.

[0070] In some embodiments, the thrust during shield tunneling is dynamically adjusted and controlled according to the following formula:

[0071] Among them, F t For real-time thrust, γ is the effective bulk density of volcanic ash, and K is the effective bulk density of volcanic ash. p For passive earth pressure coefficient, F add Add resistance to the slope, L con This is the contact length between the shield and the ground.

[0072] Real-time thrust refers to the shield propulsion force calculated in real time based on geological conditions. This is achieved through the linkage of pressure sensors and the propulsion cylinder control system, and its function is to match changes in ground resistance. Effective bulk density of volcanic ash refers to the unit volume weight of soil after deducting pore water pressure. This is determined through on-site sampling combined with indoor triaxial tests, and is used to accurately calculate the lateral pressure generated by the soil's own weight. Passive earth pressure coefficient refers to the lateral pressure coefficient of soil in a passive limit equilibrium state. This is calculated using Rankine's earth pressure theory combined with the internal friction angle of volcanic ash, and is used to characterize the squeezing effect of the soil on the shield shell during shield propulsion. Slope-induced additional resistance refers to the extra frictional resistance generated by the shield machine's own weight component during inclined propulsion. This is calculated by measuring the tunneling inclination angle in real time using attitude sensors and calculating the component, and is used to compensate for propulsion force deviations under steep slope conditions. The shield-to-ground contact length refers to the actual contact range between the shield shell and the reinforced soil area. This is determined by monitoring the stress distribution of the shield shell using distributed strain sensing fiber optics, and is used to reflect the interaction area between the shield and the ground.

[0073] Specifically, during the tunnel boring machine's (TBM) advancement, real-time data collection of ground parameters and equipment status is used to input parameters such as the effective unit weight of volcanic ash and the passive earth pressure coefficient into the thrust calculation formula. Combined with dynamic compensation for slope-related additional resistance, a closed-loop control system is formed. For example, when the TBM's climbing angle is detected to be increasing, the control system automatically increases the calculation weight of Fadd, synchronously adjusting the total thrust output. Simultaneously, based on real-time changes in the contact length, the influence of soil shear strength on thrust is dynamically corrected to avoid thrust calculation errors caused by changes in the contact surface.

[0074] Compared with existing technologies, traditional shield tunneling thrust control often relies on fixed empirical coefficients or single parameter adjustments, failing to comprehensively consider the influence of self-weight components under steep slope conditions and the dynamic changes in contact characteristics of volcanic ash strata. This scheme establishes a multi-parameter coupled thrust calculation model, achieving coordinated feedback of geological conditions, equipment attitude, and construction parameters, significantly improving thrust control accuracy under complex conditions.

[0075] Through the above technical solutions, this application effectively solves the problems of machine jamming caused by insufficient thrust and ground disturbance caused by excessive thrust during the advancement of shield tunneling on steep slopes. By dynamically compensating for the additional resistance of the slope and correcting the contact length parameters in real time, it ensures that the thrust of the shield machine in the volcanic ash strata is always in balance with the ground resistance, providing precise mechanical protection for controlling surface subsidence and attitude deviation.

[0076] In some embodiments, the slope-added resistance F add Calculate using the following formula:

[0077] Where W is the weight of the tunnel boring machine, θ is the real-time tunneling slope angle, and fr is the coefficient of friction of volcanic ash.

[0078] The weight of a tunnel boring machine (TBM) refers to the overall mass of the equipment, which can be calibrated using load cells or factory parameters to quantify the impact of the equipment's weight on slope construction. The real-time tunneling slope angle refers to the instantaneous angle between the TBM's axis and the horizontal plane, which can be dynamically monitored using a high-precision inclinometer to reflect actual slope changes during tunneling. The volcanic ash friction coefficient refers to the frictional characteristic parameter of the contact surface between the TBM shell and the volcanic ash stratum, which can be obtained through on-site direct shear tests or geological survey data to characterize the frictional resistance of the stratum to the TBM's movement.

[0079] Specifically, during the tunnel boring machine's (TBM) excavation along a steep slope, the machine's own weight creates additional resistance along the slope. By collecting real-time data on the machine's weight, inclinometer angle, and ground friction coefficient, the additional resistance value is dynamically calculated. This resistance value is added to the basic thrust formula to form a real-time total thrust control target. For example, when the slope angle increases to 7%, the system automatically increases the thrust output to overcome the increased sliding force and prevent the TBM from slipping due to insufficient thrust; when the slope angle decreases, the thrust output is reduced accordingly to prevent over-pushing and ground disturbance.

[0080] Compared to existing technologies, traditional methods typically use fixed empirical coefficients to estimate the additional resistance due to slope, neglecting the dynamic coupling between real-time slope changes and formation friction characteristics. This solution establishes a mechanical model to quantify the product relationship between slope angle, equipment weight, and friction coefficient, achieving accurate calculation of the additional resistance. For example, when fluctuations in the porosity of volcanic ash formations cause changes in the friction coefficient, the system can automatically correct the calculation parameters, avoiding thrust control errors caused by deviations in friction coefficient values.

[0081] Through the above technical solution, this application effectively solves the problem of insufficient thrust control accuracy in steep slope shield tunneling. By dynamically calculating the additional resistance of the slope, it ensures that the thrust output is accurately matched with the actual working conditions of the stratum, avoiding equipment slippage due to insufficient thrust or stratum squeezing damage caused by excessive thrust, thereby improving the stability of shield attitude control and the effect of surface settlement control.

[0082] In some embodiments, the real-time monitoring of the shield attitude and ground deformation is achieved by using at least two of the following: a fiber optic grating sensor matrix, a distributed strain sensing fiber, and a three-dimensional laser scanner.

[0083] A fiber optic grating sensor matrix refers to a monitoring system formed by arranging multiple fiber optic grating sensors in a spatial array. Specifically, it can use wavelength modulation technology to continuously measure the strain distribution in the formation, and its high sensitivity allows it to capture millimeter-level deformations. Distributed strain sensing fiber refers to a continuous distributed measurement device based on the principle of optical time-domain reflectometry. Specifically, it can reconstruct the strain field across the entire cross-section by detecting the micro-bending loss of the fiber, and its spatial resolution advantage makes it suitable for large-scale formation monitoring. A 3D laser scanner is a spatial coordinate acquisition device based on the principle of laser ranging. Specifically, it can use multi-site cloud stitching technology to achieve three-dimensional measurement of the tunnel boring machine's posture, and its non-contact measurement characteristics are suitable for dynamic construction environments.

[0084] Specifically, during the tunnel boring machine (TBM) advancement process, a fiber optic grating sensor matrix is ​​deployed along the tunnel axis to provide real-time feedback on ground compression deformation data; distributed strain sensing fibers are wound circumferentially around the shield to synchronously monitor circumferential stress distribution; and a 3D laser scanner is installed behind the launching shaft to periodically acquire the TBM's 3D coordinates. These three systems establish a coupled model of the TBM's attitude and ground deformation through a data fusion algorithm. When the detected pitch angle deviation exceeds a threshold, it automatically triggers zone thrust adjustment and synchronous grouting parameter optimization.

[0085] Compared with existing technologies, traditional shield tunneling monitoring often uses a single type of sensor, such as relying solely on a total station for point measurements, which cannot acquire continuous strain field data and is highly susceptible to interference from construction vibrations. This solution, through the collaborative work of multi-source heterogeneous sensors, not only ensures the spatial integrity of attitude measurement but also achieves distributed sensing of ground deformation, effectively solving the problem of delayed identification of abrupt deformation changes in volcanic ash formations.

[0086] Through the above technical solutions, this application achieves synchronous and accurate monitoring of shield attitude and ground deformation, can promptly identify the mismatch of construction parameters under complex geological conditions, and suppresses the risk of surface subsidence within a controllable range through a closed-loop control mechanism, thus ensuring the safety of shield launch under steep slope and ultra-shallow burial conditions.

[0087] In some embodiments, when the shield tunneling attitude is monitored in real time, if the shield pitch angle deviation is detected to be >0.3°, an attitude correction procedure is initiated. The attitude correction procedure includes the following steps:

[0088] Adjust the thrust differential between zones to 120%~150% of the design value;

[0089] Inject a high molecular weight polymer drag-reducing agent at the lower side cutter head position;

[0090] Synchronous grouting was carried out using fast-setting grout.

[0091] Pitch angle deviation refers to the angular offset between the tunnel boring machine's axis and the design axis in the vertical plane. Specifically, it can be achieved by measuring the strain distribution of the tunnel boring machine's shell through a fiber optic grating sensor matrix, which is used to determine whether the tunnel boring machine is pitching up or down.

[0092] Among them, the attitude correction program refers to the control process of restoring the attitude of the shield tunnel through multi-parameter collaborative adjustment. Specifically, it can be implemented using a graded response mechanism, which automatically triggers execution when the deviation exceeds the threshold.

[0093] Among them, the zone thrust difference refers to the thrust difference generated by each hydraulic zone of the shield propulsion system, which can be achieved by adjusting the pressure distribution of the hydraulic pump station to generate a corrective torque.

[0094] Among them, the polymer drag reducer refers to a non-Newtonian fluid material with shear thinning properties, which can be achieved by using an aqueous solution of polyacrylamide to reduce the frictional resistance at the contact surface between the cutterhead and the formation.

[0095] Among them, fast-setting grout refers to cement-based materials with an initial setting time of less than 30 minutes. Specifically, it can be achieved by using a composite formula of sulfoaluminate cement and accelerator, which is used to quickly fill the voids at the tail of the shield.

[0096] Specifically, when the fiber optic grating sensor detects that the strain difference between the front and rear of the tunnel boring machine (TBM) reaches a preset threshold, the control system determines that the pitch angle deviation exceeds the allowable range. At this time, the thrust difference between the propulsion system zones is automatically increased to 1.2-1.5 times the original design value, generating a corrective torque by increasing the thrust difference between the front and rear. Simultaneously, a high-molecular polymer material is injected in front of the descending cutterhead. This material's viscosity decreases under shearing action, penetrating to the contact surface between the cutterhead and the ground to form a lubricating layer. This is combined with synchronous grouting using fast-setting grout, which rapidly solidifies after the shield tail separates to form a supporting structure.

[0097] In some specific implementations, the injection amount of polymer drag-reducing agent can be adjusted in real time according to the change in cutterhead torque, and injection is stopped when the torque decreases by 15%. The setting time of the fast-setting grout can be controlled within the range of 5-15 minutes by adjusting the dosage of the accelerator, and the grouting pressure is maintained at 0.8-1.0 times the static earth pressure of the stratum.

[0098] Compared to existing technologies, current shield tunneling attitude correction methods often rely on a single thrust adjustment approach, which can easily exacerbate ground disturbance. This solution utilizes a triple mechanism of thrust differential adjustment, drag-reducing agent lubrication, and rapid support to maintain ground stability while correcting the tunnel's attitude. In existing technologies, grout setting time typically exceeds one hour; this solution employs fast-setting materials, reducing support response time by over 60%.

[0099] Through the above technical solutions, this application enables rapid active correction in the early stages of pitch angle anomalies, preventing shield jamming accidents caused by accumulated deviations. The injection of drag-reducing agents effectively reduces additional ground disturbance during the correction process, while the fast-setting grout promptly forms a support structure to prevent soil collapse. The synergistic effect of these three measures improves the efficiency of shield attitude recovery while controlling surface settlement increments to within 1 mm.

[0100] In some embodiments, synchronous grouting in the initial stage adopts an intermittent pulse grouting mode, and the grouting frequency f and the advancing speed v satisfy the following formula:

[0101] Among them, S t is the density coefficient of volcanic ash, and e is the natural constant.

[0102] Intermittent pulse grouting mode refers to a non-continuous grouting method achieved by periodically opening and closing grouting valves. Specifically, it can be implemented using a solenoid valve assembly linked with a PLC control system. This mode controls the interval between grout injections, allowing the grout to fully fill the formation pores under high-pressure pulses. Grouting frequency refers to the number of grouting pulses per unit time, which can be adjusted by regulating the solenoid valve's operating cycle. This parameter has a dynamic matching relationship with the tunnel boring machine's (TBM) advancement speed. The volcanic ash density coefficient is a dimensionless parameter reflecting the degree of cementation between volcanic ash particles. It can be determined through indoor triaxial tests. This coefficient is used to correct the adaptability of the grouting frequency to formation permeability.

[0103] Specifically, during the initial stage of tunnel boring machine (TBM) advancement, the grouting system dynamically calculates the optimal grouting frequency based on real-time collected advance speed data using the formula f=2v / D e^(-0.02S_t). As the advance speed increases, the grouting frequency increases linearly to ensure sufficient grouting per unit distance, while simultaneously compensating for the permeability characteristics of the volcanic ash formation through an exponential function term. For example, in a volcanic ash formation with a density coefficient St=50, when the TBM advances at a speed of 20mm / min, the grouting frequency can be controlled at 3-4 pulses per minute, with each pulse lasting 8-10 seconds. This method utilizes pressure fluctuations to induce root-like diffusion paths in the loose strata, while avoiding excessive grout diffusion caused by continuous grouting.

[0104] Compared to existing technologies, traditional synchronous grouting often employs a constant-rate continuous grouting method. In volcanic ash formations, this method is prone to pressure attenuation due to continuous grout penetration, resulting in insufficient effective grout diffusion radius. Intermittent pulse grouting, on the other hand, maintains grout penetration dynamics through periodic pressure impacts. Simultaneously, the pulse interval provides a time window for the dissipation of pore water pressure in the formation, which is beneficial for forming a dense reinforcement layer. Existing technologies often rely on empirically set grouting parameters, while the frequency-velocity mathematical model established in this scheme achieves dynamic coupling control of grouting and tunneling parameters.

[0105] Through the above technical solution, this application effectively resolves the technical contradiction between excessive grout penetration and grout pressure attenuation during grouting in volcanic ash formations. The periodic pressure impact formed by pulse grouting ensures both the effective diffusion range of the grout and prevents large amounts of grout from being lost to unreinforced areas. This control method ensures precise matching between the grouting body and the tunneling progress, forming a continuous and uniform reinforcement ring under ultra-shallow burial conditions, providing a reliable guarantee for controlling surface subsidence.

[0106] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for controlling the launch of large-diameter, steep-slope, ultra-shallow buried shield tunnels in volcanic ash strata, characterized in that... Includes the following steps: Based on geological parameters, the range of strata reinforcement was calculated, and directional grouting was used to reinforce the strata at the starting point. A multi-stage sealing device was installed at the tunnel entrance of the shield tunnel, and its sealing performance was verified before the tunnel entrance was breached. During shield tunneling, the thrust, torque, and grouting parameters are dynamically adjusted to control surface settlement to ≤3mm. Real-time monitoring of shield tunnel attitude and ground deformation, and adjustment of construction parameters through data feedback in a closed loop; The range of ground reinforcement is calculated using the following formula: Among them, L str Where D is the length of the reinforced zone, β is the diameter of the shield, H is the starting slope angle, and C is the tunnel depth. u For the undrained shear strength of volcanic ash, S r is the porosity correction factor for volcanic ash, and k is the safety factor; The dynamic adjustment of thrust during shield tunneling is dynamically controlled according to the following formula: Among them, F t For real-time thrust, γ is the effective bulk density of volcanic ash, and K is the effective bulk density of volcanic ash. p For passive earth pressure coefficient, F add Add resistance to the slope, L con The contact length between the shield and the ground; Slope-induced additional resistance F add Calculate using the following formula: Where W is the weight of the tunnel boring machine, θ is the real-time tunneling slope angle, and f r The coefficient of friction of volcanic ash.

2. The method for controlling the launch of large-diameter, steep-slope, ultra-shallow buried shield tunnels in volcanic ash strata according to claim 1, characterized in that, The directional grouting uses cement grout and / or water glass, and the grouting pressure is controlled according to the following formula: Among them, P inj For the maximum grouting pressure, σ v For vertical earth pressure, σ h ρ is the horizontal earth pressure, K0 is the coefficient of earth pressure at rest, μ is the grout viscosity, v is the grouting rate, and d is the grouting fluid viscosity. p α is the equivalent diameter of the grouting hole, and α is the correction factor for the volcanic ash formation.

3. The method for controlling the launch of large-diameter, steep-slope, ultra-shallow buried shield tunnels in volcanic ash strata according to claim 1, characterized in that, The sealing device includes a wire brush sealing ring, an expandable rubber sealing ring, and an emergency airbag sealing layer arranged sequentially from the outside to the inside.

4. The method for controlling the launch of large-diameter, steep-slope, ultra-shallow buried shield tunnels in volcanic ash strata according to claim 3, characterized in that, Before the tunnel portal is breached, bentonite grout is injected into the gap of the sealing device to form a pressure balance zone, the pressure value of which is 1.05 to 1.15 times the static earth pressure.

5. The method for controlling the launch of large-diameter, steep-slope, ultra-shallow buried shield tunnels in volcanic ash strata according to claim 1, characterized in that, The real-time monitoring of the shield attitude and ground deformation is achieved by using at least two of the following: a fiber optic grating sensor matrix, a distributed strain sensing fiber, and a three-dimensional laser scanner.

6. The method for controlling the launch of large-diameter, steep-slope, ultra-shallow buried shield tunnels in volcanic ash strata according to claim 5, characterized in that, When monitoring the shield tunneling attitude in real time, if the detected pitch angle deviation is >0.3°, the attitude correction program is initiated. The attitude correction program includes the following steps: Adjust the thrust differential between zones to 120%~150% of the design value; Inject a high molecular weight polymer drag-reducing agent at the lower side cutter head position; Synchronous grouting was carried out using fast-setting grout.

7. The method for controlling the launch of large-diameter, steep-slope, ultra-shallow buried shield tunnels in volcanic ash strata according to claim 1, characterized in that, The initial stage of synchronous grouting adopts an intermittent pulse grouting mode, and the grouting frequency f and the advancing speed v satisfy the following formula: Among them, S t is the density coefficient of volcanic ash, and e is the natural constant.

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