Advanced reinforcement method for arranging double-layer large pipe shed behind shield for TBM construction
By setting up a double-layer large pipe roof during TBM tunnel excavation and using discrete element numerical simulation software to monitor pressure changes, the problem of insufficient surrounding rock stability was solved, surrounding rock deformation control and machine jamming risk were reduced, and construction safety and efficiency were improved.
Patent Information
- Application Number
- CN202511527889.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-24
- Publication Date
- 2026-02-10
AI Technical Summary
During the excavation of deep-buried TBM tunnels, the surrounding rock has poor stability, which can easily lead to rock bursts, large deformations in soft rock, and machine jamming accidents. Existing technologies lack effective advanced support methods and systematic numerical simulation evaluation methods, resulting in poor support effects and difficulty in preventing and extricating the machine from getting stuck.
Discrete element numerical simulation software was used to create a scale model to monitor the pressure changes between the TBM shield and the surrounding rock. By setting up a double-layer large pipe roof behind the shield, the pressure changes during drilling and grouting were monitored in stages to evaluate the support effect.
It effectively controls surrounding rock deformation, reduces the risk of TBM jamming, improves construction safety and efficiency, provides a reliable basis for numerical analysis, and optimizes support timing and parameters.
Smart Images
Figure CN121503182A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a TBM construction technology, and more particularly to a method for pre-reinforcement of the shield by setting up a double-layer large pipe shed behind the shield during TBM construction. Background Technology
[0002] Currently, during the excavation of deep-buried TBM tunnels, the stability of the surrounding rock faces severe challenges when traversing adverse geological sections such as faults, fault fracture zones, weak surrounding rock, water-rich strata, high ground stress, and karst development. Existing technologies, lacking effective pre-support methods, are prone to rock bursts, large deformations in soft rock, and collapses. Especially during TBM excavation, these hazards not only severely impact construction progress but can also lead to major accidents such as TBM equipment jamming. Traditional support methods often suffer from delayed support timing and limited support effectiveness, making it difficult to control surrounding rock deformation in a timely and effective manner. Although the double-layer large pipe roof support scheme behind the shield in the arch pipe roof working area can alter the stability variation pattern of the surrounding rock to some extent, existing technologies lack systematic numerical simulation evaluation methods, making it impossible to accurately predict and evaluate the support effect. This results in low efficiency in the extrication of TBMs after jamming and fails to provide reliable technical references for preventing TBM jamming and extrication. Therefore, existing technologies urgently need improvement to address these issues. Summary of the Invention
[0003] The purpose of this invention is to provide a method for pre-reinforcement of the TBM construction by setting up a double-layer large pipe shed behind the shield. By comparing and analyzing the pressure values between the shield and the surrounding rock in two schemes, namely, no pipe shed support and double-layer large pipe shed support set up behind the shield in the arch pipe shed working area, the stability effect of the double-layer large pipe shed support scheme on the TBM surrounding rock is determined.
[0004] The objective of this invention is achieved through the following technical solution: a method for pre-reinforcement of the shield behind a double-layer large pipe shed during TBM construction, the method comprising the following steps: 1) Select discrete element numerical simulation software; 2) Model the tunnel to scale based on the actual dimensions of the tunnel construction site; 3) Using the pipe-free roof support scheme as a comparative test, the servo mechanism in the simulation software was used to monitor the TBM shield pressure-surrounding rock pressure, and this was used as a parameter index. 4) During the drilling and support stages of the double-layer large pipe shed, the servo mechanism in the simulation software was used to monitor the change law of the TBM shield-surrounding rock pressure value. 5) Compare and analyze the results of the two schemes, and evaluate the effect of the double-layer pipe roof support scheme on the stability of the surrounding rock by the variation law of TBM shield-surrounding rock pressure value.
[0005] In step 2), the tunnel excavation parameters are first collected to determine the model size; then the material and contact mechanical properties are defined; next, the model boundary conditions are set to create the actual initial geostress environment of the tunnel; finally, the surrounding rock and pipe roof particles are generated in sections to complete the establishment of a proportional digital model.
[0006] In step 2), a pipe roof work area is arranged within a 180° range behind the TBM shield, a double-layer large pipe roof is constructed within a 150° range, and continuous boreholes with a diameter of 15cm are drilled within a 180° range around the shield.
[0007] In step 2), the numerical model is established with the TBM as the center and the surrounding rock with the TBM shield boundary as the inner boundary.
[0008] In step 2), the surrounding rock is divided into three parts according to the interaction between the surrounding rock and the TBM, as well as the arrangement of the pipe roof working area: the pipe roof working area, the surrounding rock disturbance area, and the surrounding rock undisturbed area. The pipe roof work area is used for drilling, installation and grouting of pipe roofs. Temporary work platforms and equipment arrangements need to be set up in this area so that construction personnel can operate drilling rigs and other equipment. The disturbed area of the surrounding rock is the area affected by radiation after TBM excavation and double-layer pipe roof support; The undisturbed zone of the surrounding rock is the area where the surrounding rock is not affected by radiation after TBM excavation and double-layer large pipe roof support. This zone, together with the model boundary, provides the initial ground stress for the model.
[0009] Furthermore, in step 4), the monitoring of the TBM shield pressure-surrounding rock pressure value change pattern using the servo mechanism in the simulation software is divided into two stages. The first stage is drilling. After drilling is completed, it provides energy release space for the surrounding rock, which can reduce the surrounding rock pressure acting on the TBM shield. The second stage is the reinforcement by double-layer large pipe roof grouting, which forms a ring support beam above the TBM shield, playing a role in stabilizing the surrounding rock, mitigating deformation, and providing buffer protection.
[0010] By adopting the above-mentioned technical solution, this application provides a method for pre-reinforcement of the shield behind the TBM construction by setting up a double-layer large pipe shed. The effect of the double-layer large pipe shed support is compared and analyzed by discrete element numerical simulation. Combined with pressure monitoring in two stages of drilling and grouting, the deformation of the surrounding rock is effectively controlled and a ring support structure is formed. It has the advantages of improving the timeliness of support, reducing the risk of TBM jamming and improving construction safety. Attached Figure Description
[0011] The accompanying drawings of this invention are described below: Figure 1 This is a schematic diagram of the double-layer large pipe shed support structure for TBM construction according to the present invention; Figure 2 This is a diagram of the numerical analysis model of the present invention; Figure 3 This is a diagram of the double-layer large pipe shed workshop and processing structure of the present invention; Figure 4 This is a model diagram of the pipeless roof support system of the present invention; Figure 5 This is a model diagram of the double-layer large pipe shed support of the present invention; Figure 6 This is the energy release diagram of the surrounding rock according to the present invention; Figure 7 This is a pressure curve diagram of the pipe-free roof support TBM shield of the present invention; Figure 8 This is a pressure curve diagram of the double-layer pipe roof support TBM shield of the present invention.
[0012] Among them, 1. Tunnel outline; 2. Double-layer large pipe shed; 3. TBM cutterhead; 4. Pipe shed working room; 5. TBM shield; 6. Vertical ground stress; 7. Horizontal ground stress; 8. Model boundary; 9. Undisturbed surrounding rock zone; 10. Disturbed surrounding rock zone; 11. Large pipe shed construction range angle 150°; 12. Drilling between shield and surrounding rock. Detailed Implementation
[0013] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. However, the present invention is not limited to these embodiments. Any improvements or substitutions based on the basic spirit of these embodiments shall still fall within the scope of protection claimed by the claims of the present invention.
[0014] Example 1, as Figure 1 As shown, a method for pre-reinforcement of the shield behind a double-layer large pipe shed during TBM construction includes the following steps: 1) Select discrete element numerical simulation software; 2) Model the tunnel to scale based on the actual dimensions of the tunnel construction site; 3) Using the pipe-free roof support scheme as a comparative test, the servo mechanism in the simulation software was used to monitor the TBM shield pressure-surrounding rock pressure, and this was used as a parameter index. 4) During the drilling and support stages of the double-layer large pipe shed, the servo mechanism in the simulation software was used to monitor the change law of the TBM shield-surrounding rock pressure value. 5) Compare and analyze the results of the two schemes, and evaluate the effect of the double-layer pipe roof support scheme on the stability of the surrounding rock by the variation law of TBM shield-surrounding rock pressure value.
[0015] like Figure 2 , 3As shown in Figures 4 and 5, a servo mechanism is used to apply in-situ stresses to the model boundary to meet the environmental conditions of a certain TBM tunnel burial depth, forming the initial boundary conditions. During TBM excavation, the vertical in-situ stress 6 and the horizontal in-situ stress 7 will cause the TBM shield 5 to be subjected to the pressure of the surrounding rock, generating a certain frictional force between the shield and the surrounding rock. Under adverse geological conditions, the frictional force may increase significantly, thereby increasing the risk of TBM jamming. Therefore, the pressure between the shield and the surrounding rock plays a decisive role in TBM jamming accidents.
[0016] Discrete element numerical simulation software refers to simulation tools based on the theory of discontinuous media mechanics, capable of simulating the crushing, slippage, and contact force transmission processes of granular materials. Specifically, software such as PFC2D and 3DEC can be used to capture the details of the interaction between the surrounding rock and the tunnel roof. Proportional modeling refers to constructing a geometric model based on the actual cross-sectional dimensions and geological parameters of the tunnel. This is achieved through reverse modeling using laser scanning or ground-penetrating radar data, ensuring that the model's boundary conditions and material properties are consistent with those on-site. Servo mechanism monitoring refers to the real-time acquisition of pressure data through the software's built-in mechanical feedback system, specifically implemented using contact force sensors and displacement constraint algorithms, used to quantify the dynamic changes in contact pressure between the shield and the surrounding rock. Parameter indices refer to the ratio or difference between the shield pressure and the surrounding rock pressure, specifically generated through data normalization processing, serving as a quantitative benchmark for evaluating the stability of the surrounding rock.
[0017] Specifically, firstly, a model incorporating surrounding rock particles, pipe roof structures, and shield components was established using discrete element method (DEM) software, with boundary conditions set based on the initial geostress field. In the pipe roof-less scheme, simulations were run and the peak and fluctuation range of the shield pressure were recorded, establishing a pressure baseline under natural rock deformation. Subsequently, in the double-layer pipe roof scheme, monitoring was conducted in two stages: during the drilling stage, the formation of a free face was simulated by removing particles, and the shield pressure drop caused by the release of surrounding rock stress was recorded; during the grouting stage, the formation of a ring-shaped support beam was simulated by imparting bonding strength to the pipe roof particles, and the shield pressure recovery amplitude and distribution pattern were monitored. Finally, the pressure curves of the two schemes were superimposed and compared, and the suppression effect of the pipe roof on surrounding rock deformation was determined by indicators such as pressure fluctuation amplitude, peak position, and stabilization time.
[0018] Compared to existing technologies, which often employ elasticity models for single-stage static analysis, this approach fails to capture the stress release effect caused by drilling. Our proposed solution, however, utilizes discrete element dynamic simulation to fully reproduce the entire process from stress release to structural load-bearing capacity, particularly revealing the secondary adjustment effect of grouting reinforcement on shield pressure. Traditional techniques focus only on the final support state, while this solution, through phased monitoring, clarifies the contribution of different construction procedures to surrounding rock stability, providing data support for optimizing borehole spacing and grouting timing.
[0019] Through the above technical solutions, this application can accurately identify the key stages of surrounding rock stress release and guide the targeted optimization of pipe roof support. When the TBM tunnels through fault fracture zones, it can effectively reduce the risk of sudden changes in shield pressure and reduce the range of loosened rock. When the TBM tunnels through fault fracture zones, by analyzing the pressure distribution pattern, the spacing between pipe roof layers can be adjusted to enhance the cooperative bearing capacity, thereby preventing jamming accidents and improving the efficiency of escape response.
[0020] In step 2), the tunnel excavation parameters are first collected to determine the model size; then the material and contact mechanical properties are defined; furthermore, the model boundary conditions are set to create the actual initial geostress environment of the tunnel; finally, the surrounding rock and pipe roof particles are generated in sections to complete the establishment of a proportional digital model.
[0021] Among them, collecting tunnel excavation parameters refers to obtaining actual construction data such as TBM cutterhead thrust, rotation speed, and torque. Specifically, data can be collected through an engineering monitoring system to determine the geometric dimensions and boundary range of the model.
[0022] Defining material and contact mechanical properties refers to assigning physical parameters such as elastic modulus and Poisson's ratio to the surrounding rock particles. Specifically, this can be achieved using the particle bonding model built into the discrete element method software, which is used to characterize the mechanical behavior of the surrounding rock and the pipe roof.
[0023] Setting model boundary conditions refers to applying an initial geostress field that matches the actual situation. This can be achieved through displacement constraints and stress loading, and is used to restore the original stress state before tunnel excavation.
[0024] Among them, the generation of surrounding rock and pipe roof particles by partitioning refers to dividing the model into a pipe roof working area, a surrounding rock disturbance area, and an undisturbed area. Specifically, a region partitioning tool can be used to generate particle assemblies of different particle sizes to achieve differentiated expression of material properties.
[0025] Specifically, a systematic modeling process addresses the issue of insufficient model accuracy. After collecting tunnel excavation parameters, the model size is strictly limited to a scale proportional to the actual working conditions to avoid geometric distortion. Material properties are precisely assigned to the surrounding rock particles and pipe roof structure, and contact mechanics parameters are set to reflect the actual interaction mechanism, providing an accurate calculation basis for pressure monitoring. The initial geostress environment is reconstructed through displacement constraints and stress loading methods, making the simulated working conditions close to real geological conditions. During model construction, the surrounding rock area is divided into a working zone, a disturbed zone, and a undisturbed zone. Different particle generation strategies are used for different zones, ensuring modeling efficiency while providing clear physical boundaries for subsequent analysis.
[0026] Compared with existing technologies, traditional modeling methods often ignore the influence of actual tunneling parameters on model dimensions and fail to establish the correspondence between material properties and contact parameters, resulting in simulation results deviating from engineering reality. This solution integrates construction parameter acquisition, material property definition, geostress reconstruction, and zonal modeling techniques to construct a high-precision, scaled-down digital model, enabling a realistic reflection of the interaction mechanism between the surrounding rock and the support structure.
[0027] Through the above technical solution, this application effectively solves the simulation error problem caused by model parameter distortion, enabling the impact of double-layer large pipe roof support on the stability of surrounding rock to be accurately assessed, providing a reliable numerical analysis basis for preventing TBM jamming accidents, and improving the safety and efficiency of tunnel construction.
[0028] Furthermore, in step 2), a pipe roof work area 4 is arranged within a 180° range behind the TBM shield, a double-layer large pipe roof 2 is constructed within a 150° range, and continuous boreholes with a diameter of 15cm are drilled within a 180° range around the shield.
[0029] Among them, double-layer large pipe roof support plays an important role in improving TBM tunneling conditions, reducing surrounding rock deformation, and enhancing construction safety. Its structure is as follows: Figure 3 As shown, the construction is carried out in the pipe roof working room 4, which is constructed within a 180° range of the tunnel arch and has a height of 0.95m.
[0030] The pipe roof working area refers to the ring-shaped construction space formed behind the tunnel shield, which can be constructed using steel frame supports and temporary support structures. It serves as a safe working area for drilling equipment and personnel. The double-layer large pipe roof refers to two rows of pipe roof structures arranged longitudinally along the tunnel. Specifically, a composite reinforcement layer can be formed using steel pipe grouting technology, and the staggered arrangement enhances the overall bearing capacity of the surrounding rock. Continuous drilling can be carried out using hydraulic rock drills, and standardized hole diameter control ensures effective bonding between the grouting material and the surrounding rock.
[0031] Specifically, a ring-shaped pipe roof working area is formed within a 180° radius behind the shield, providing a stable installation base and operating space for the drilling rig and avoiding construction interference with the shield structure. Double-layered large pipe roofs are laid out in layers within a 150° radius, forming an arched reinforcement zone through the synergistic effect of the upper and lower layers, effectively controlling the surrounding rock pressure. Continuous drilling is performed around the shield's outer 180° perimeter, using standardized borehole diameters to balance stress release and grouting channels. Grouting material penetrates and fills the surrounding rock fissures to form a reinforcement layer. This scheme, through spatial zoning and structural layering design, achieves the dual objectives of surrounding rock stress control and load-bearing structure optimization within a limited construction area.
[0032] Compared to existing technologies, traditional methods typically employ a symmetrical pipe roof layout, which suffers from limited construction space and material waste. This solution limits the layout to a 150° double-layer pipe roof, focusing on strengthening the support in the arch area while reducing redundant reinforcement in non-critical lateral areas. The standardized borehole diameter design for continuous drilling reduces equipment adjustment frequency and improves the consistency of borehole quality compared to traditional variable-diameter drilling processes. The circular layout of the pipe roof work area, compared to a distributed construction platform, shortens equipment movement paths and improves operational safety.
[0033] Through the above technical solutions, this application effectively controls the deformation rate of the surrounding rock when a deep-buried tunnel passes through an adverse geological section, and reduces the peak value of the asymmetric load borne by the TBM shield. The ring layout of the pipe roof working area ensures the continuity of drilling and grouting operations, and the composite support structure formed by the double-layer large pipe roof significantly improves the self-stabilizing capacity of the surrounding rock at the arch. The standardized implementation of continuous drilling ensures the uniform bonding between the grouting reinforcement layer and the surrounding rock, thereby systematically suppressing the risk of machine jamming caused by surrounding rock instability.
[0034] In step 2), the numerical model is established with the TBM as the center and the surrounding rock with the TBM shield boundary as the inner boundary.
[0035] Here, "TBM as the center" means using the TBM shield as the core positioning reference for the entire model. This can be achieved by setting the geometric center of the shield as the origin of the coordinate system in the modeling software, ensuring that the relative positional relationship between the generated range of surrounding rock particles and the shield is consistent with the actual engineering. "Shield boundary as inner boundary" means defining the outer surface of the TBM shield as the inner boundary for the generation of surrounding rock particles. This can be achieved by setting the shield surface as a rigid wall boundary in the discrete element method software, allowing direct contact forces between the surrounding rock particles and the shield interface.
[0036] Specifically, in the discrete element model, the shield interface serves as the inner boundary restricting the generation of surrounding rock particles. These particles extend outwards from the shield surface, forming a ring-shaped distribution structure with the shield as its inner boundary. During the simulation, the contact pressure between the shield interface and the surrounding rock particles is calculated in real-time using the discrete element contact algorithm, directly reflecting the mechanical interaction between the shield and the surrounding rock. This modeling approach avoids the contact surface separation problem caused by simplifying the shield as an independent structure in traditional methods, making the stress distribution in the surrounding rock more closely resemble the mechanical state of the shield compressing the surrounding rock during actual tunneling.
[0037] Through the above technical solution, this application can accurately simulate the pressure transmission characteristics of the contact surface between the TBM shield and the surrounding rock, and effectively capture the stress redistribution law of the surrounding rock under the squeezing action of the shield. This modeling method provides a realistic mechanical environment basis for analyzing the regulatory effect of double-layer large pipe roof support on the pressure change of the shield-surrounding rock, and solves the problem of support effect evaluation deviation caused by the distortion of boundary conditions in traditional models.
[0038] Furthermore, in step 2), based on the interaction between the surrounding rock and the TBM, and the arrangement of the pipe roof working area, the surrounding rock is divided into three parts: the pipe roof working area, the surrounding rock disturbance area 10, and the surrounding rock undisturbed area 9. The pipe roof work area is used for drilling, installation and grouting of pipe roofs. Temporary work platforms and equipment arrangements need to be set up in this area so that construction personnel can operate drilling rigs and other equipment. The surrounding rock disturbance zone 10 is the radiation area affected by the surrounding rock after TBM tunneling and double-layer pipe roof support; The undisturbed zone 9 is the area where the surrounding rock is not affected by radiation after TBM excavation and double-layer large pipe roof support. This area, together with the model boundary, provides the initial ground stress for the model.
[0039] Specifically, during TBM tunnel excavation, the pipe roof working area provides operational space for drilling and grouting through temporary equipment placement, ensuring the feasibility of the construction process. In the disturbed rock zone, stress variation patterns are monitored to clarify the support's effective range, guiding the dynamic adjustment of reinforcement parameters. In the undisturbed rock zone, the initial geostress environment is maintained through interaction with the model boundary, avoiding simulation errors caused by boundary distortion. By dividing the area into three zones, construction resources can be strategically allocated to different areas. For example, equipment placement is prioritized in the pipe roof working area, pressure changes are closely monitored in the disturbed rock zone, and geostress stability is maintained in the undisturbed rock zone.
[0040] Compared to existing technologies, traditional methods fail to clearly delineate the surrounding rock area, leading to ambiguity in construction operations and monitoring scope, making it difficult to accurately control the reinforcement effect. In existing technologies, initial in-situ stress simulations often suffer from distorted boundary conditions, affecting the reliability of the results, and construction interference issues are not addressed through independent spatial design. This solution achieves refined control of the construction process and monitoring scope through functional zoning, while simultaneously ensuring the accuracy of the numerical model.
[0041] Through the above technical solutions, this application solves the problems of rock bursts, large deformations in soft rock, and machine jamming accidents caused by insufficient surrounding rock stability. The independent space design of the pipe roof working area avoids construction interference, the dynamic monitoring of the disturbed surrounding rock zone improves the effectiveness of reinforcement measures, and the boundary condition setting of the undisturbed surrounding rock zone ensures the reliability of simulation results. Thus, by optimizing resource allocation through zoned management, the effect of surrounding rock reinforcement is improved.
[0042] In step 4), the monitoring of the TBM shield pressure-surrounding rock pressure value change law using the servo mechanism in the simulation software is divided into two stages. The first stage is drilling. After drilling is completed, it provides energy release space for the surrounding rock, which can reduce the surrounding rock pressure acting on the TBM shield. The second stage is double-layer large pipe roof grouting reinforcement, which forms a ring support beam above the TBM shield, playing a role in stabilizing the surrounding rock, reducing deformation, and buffering protection.
[0043] The servo mechanism refers to the real-time feedback system built into the numerical simulation software, which is used to dynamically capture pressure change data. Specifically, it can be implemented using displacement control or stress control modes, and can continuously record the pressure fluctuations at the contact surface between the shield and the surrounding rock.
[0044] The drilling stage refers to the construction process of forming cavities through mechanical drilling, which can be achieved using a hydraulic drilling rig. The formation of cavities redistributes the internal stress of the surrounding rock and releases the previously accumulated elastic strain energy.
[0045] The grouting reinforcement stage refers to the process of injecting cement-based grout into the borehole and allowing it to solidify. This can be achieved using a high-pressure grouting pump. After solidification, the grout forms a composite load-bearing structure together with the surrounding rock. The ring support beam refers to a ring-shaped stress system formed by the interaction between the grout and the surrounding rock. This can be achieved by adjusting the grouting pressure and solidification time. This structure can transform localized concentrated stress into uniformly distributed circumferential compressive stress.
[0046] Specifically, during the drilling phase, the internal stress of the surrounding rock is released through the borehole cavity. The servo mechanism monitors the decreasing trend of the shield pressure value in real time, and this data is quantified as the stress release coefficient. During the grouting reinforcement phase, the grout penetrates into the surrounding rock fissures and solidifies to form a support structure. The servo mechanism monitors the shield pressure value gradually stabilizing from a fluctuating state, and this process is recorded as the stress equilibrium time. By comparing the pressure change curves of the two phases, the contribution ratio of the borehole pressure relief effect and the grouting reinforcement effect to the stability of the surrounding rock can be clearly distinguished. For example, during construction in a fault fracture zone, if the pressure drop in the first stage exceeds the set threshold, it indicates that subsequent grouting parameters need to be adjusted to enhance the support stiffness.
[0047] Compared to existing technologies, traditional methods typically monitor drilling and grouting as a continuous process, failing to differentiate the impact of different construction stages on the mechanical behavior of the surrounding rock. This proposed solution, through staged pressure monitoring, can accurately identify the degree of stress release caused by drilling and the support stiffness formed by grouting, thereby establishing a quantitative relationship between construction parameters and support effectiveness. Existing technologies, when using a single monitoring indicator, struggle to determine whether pressure changes originate from natural creep of the surrounding rock or from artificial support. This proposed solution eliminates this technical blind spot through time-series data analysis.
[0048] Through the above technical solution, this application can accurately evaluate the support effectiveness of double-layer pipe sheds at different construction stages, providing data support for optimizing key parameters such as drilling depth and grouting pressure. When traversing water-rich strata, the permeability characteristics of the surrounding rock can be determined based on the pressure drop rate in the first stage, thereby adjusting the setting time of the grouting material. This solution solves the technical deficiency of traditional evaluation methods in being unable to quantify the contribution of each support stage, and avoids the problem of support structure failure caused by improper parameter matching.
[0049] In deep-buried tunnel projects, the surrounding rock possesses extremely high energy under high ground stress. When pipe roof drilling is performed, the borehole temporarily provides a small space for energy release within the surrounding rock, such as... Figure 6 As shown, during this stage, the energy of the surrounding rock was released to a certain extent, and the pressure on the TBM shield was also reduced.
[0050] The servo mechanism monitors and records the pressure changes experienced by the TBM shield under two scenarios, as shown in the following results. Figure 7 , 8 As shown in the figure, the results indicate that after the TBM shield pressure stabilizes, compared to the comparison scheme, the pressure borne by the TBM shield in the double-layer large pipe roof support scheme is reduced by about 27%, and the surrounding rock stabilization effect is obvious.
Claims
1. A method for pre-reinforcement of the shield with a double-layer large pipe shed in TBM construction, characterized in that, The method includes the following steps: 1) Select discrete element numerical simulation software; 2) Model the tunnel to scale based on the actual dimensions of the tunnel construction site; 3) Using the pipe-free roof support scheme as a comparative test, the servo mechanism in the simulation software was used to monitor the TBM shield pressure-surrounding rock pressure, and this was used as a parameter index. 4) During the drilling and support stages of the double-layer large pipe shed, the servo mechanism in the simulation software was used to monitor the change law of the TBM shield-surrounding rock pressure value. 5) Compare and analyze the results of the two schemes, and evaluate the effect of the double-layer pipe roof support scheme on the stability of the surrounding rock by the variation law of TBM shield-surrounding rock pressure value.
2. The method for pre-reinforcement of the shield behind the TBM construction shield as described in claim 1, characterized in that, in In step 2), firstly, tunnel excavation parameters are collected to determine the model size; then, material and contact mechanical properties are defined; next, model boundary conditions are set to create the actual initial geostress environment of the tunnel; finally, surrounding rock and pipe roof particles are generated in sections to complete the establishment of a proportional digital model.
3. The method for pre-reinforcement of the shield behind the TBM construction shield as described in claim 2, characterized in that: in In step 2), a pipe roof work area is arranged within a 180° range behind the TBM shield, a double-layer large pipe roof is constructed within a 150° range, and continuous boreholes with a diameter of 15cm are drilled within a 180° range around the shield.
4. The method for pre-reinforcement of the shield behind the TBM construction shield as described in claim 3, characterized in that: in In step 2), the numerical model is established with the TBM as the center and the surrounding rock with the TBM shield boundary as the inner boundary.
5. The method for pre-reinforcement of the shield behind the TBM construction shield as described in claim 4, characterized in that: in In step 2), based on the interaction between the surrounding rock and the TBM, and the layout of the pipe roof working area, the surrounding rock is divided into three parts: the pipe roof working area, the surrounding rock disturbance area, and the surrounding rock undisturbed area. The pipe roof work area is used for drilling, installation and grouting of pipe roofs. Temporary work platforms and equipment arrangements need to be set up in this area so that construction personnel can operate drilling rigs and other equipment. The disturbed area of the surrounding rock is the area affected by radiation after TBM excavation and double-layer pipe roof support; The undisturbed zone of the surrounding rock is the area where the surrounding rock is not affected by radiation after TBM excavation and double-layer large pipe roof support. This zone, together with the model boundary, provides the initial ground stress for the model.
6. The method for pre-reinforcement of the shield behind the TBM construction shield as described in claim 5, characterized in that: in In step 4), the monitoring of the TBM shield pressure-surrounding rock pressure value change law using the servo mechanism in the simulation software is divided into two stages. The first stage is drilling. After the drilling is completed, it provides an energy release space for the surrounding rock. The second stage is double-layer large pipe roof grouting reinforcement, which forms a ring support beam above the TBM shield.