A numerical simulation and parameter optimization method for TBM double-cutterhead rock breaking based on FEM-SPH adaptive conversion

Abstract

This invention relates to the field of numerical simulation of rock breaking and optimization of tunnel boring machine (TBM) parameters. It provides a numerical simulation and parameter optimization method for TBM double-roller rock breaking based on FEM-SPH adaptive transformation, comprising the following steps: constructing a three-dimensional double-roller rock breaking calculation model; assigning an elastic-plastic damage constitutive relation to the rock model and setting an adaptive transformation criterion; applying boundary conditions to the model and implementing step-by-step loading control with indentation followed by cutting; performing FEM-SPH adaptive coupling solution; extracting response data and dividing the process into stable cutting stages based on load characteristics, discarding transient transition stage data; evaluating the synergistic rock breaking effect of the double-roller cutters under different cutter spacing and / or different penetration depth conditions, and outputting optimal parameters. This scheme not only improves the realism and stability of the numerical simulation of the cutter rock breaking process but also provides engineering-convincing technical support for the optimization of TBM cutter layout and construction parameters.

Description

Technical Field

[0001] This invention relates to the field of numerical simulation of rock breaking and optimization of tunnel boring parameters, specifically to a numerical simulation and parameter optimization method for TBM double-roll cutter rock breaking based on FEM-SPH adaptive transformation. Background Technology

[0002] Full-face tunnel boring machines (TBMs) are core equipment for efficient mechanized construction in underground engineering. The disc cutter, as a key component directly acting on the rock mass for rock breaking, directly affects rock breaking efficiency, cutter wear rate, cutterhead structural safety, and overall machine efficiency due to its stress characteristics, penetration depth, cutting trajectory, and the synergistic effect between adjacent cutters. Cutter rock breaking is not a simple static crushing process, but a complex dynamic evolution involving localized impact, high stress concentration, elasto-plastic deformation, microcrack initiation and propagation, rock fragmentation, and debris dispersion. Especially in dual-cutter or multi-cutter collaborative rock breaking scenarios, mismatch between cutter spacing and penetration depth can easily lead to abnormal loads, ineffective rock stripping, increased energy consumption, and abnormal cutter wear. Therefore, establishing numerical analysis and parameter optimization methods that can realistically reflect the cutter-rock interaction process is of great significance for optimizing cutterhead parameter configuration.

[0003] Existing research on roller cutter rock breaking typically combines theoretical analysis, laboratory experiments, and numerical simulation. While the finite element method (FEM) is relatively mature in analyzing stress fields in continuous media, it faces significant shortcomings in simulating roller cutter rock breaking: First, the large local deformation, crack propagation, and rock fragment scattering under the action of the roller cutter lead to severe mesh distortion, resulting in decreased computational accuracy or even solution interruption. Second, conventional element deletion techniques easily cause mass loss, distortion of fragment volume, and inaccurate tracking of subsequent fragment movement, making it difficult to fully reproduce the evolution path of crack initiation, peeling, and scattering. Third, the explicit dynamic loading method of directly applying a constant thrust has poor numerical stability, and the initial transient contact effect interferes with the extraction of load characteristics in the steady-state rock breaking stage, hindering the unified comparison of parameters under different working conditions.

[0004] For the aforementioned problems of large deformation and discontinuous failure, the Smooth Particle Hydrodynamics (SPH) method possesses inherent adaptability due to its independence from fixed meshes. However, the computational cost of using the pure SPH method across the entire computational domain is high, and it has limitations in terms of the accuracy of the initial response of the continuum and boundary treatment, making it difficult to achieve efficient computation for large-sized rock masses and multi-parameter conditions. Furthermore, existing optimization studies on double-roll cutter arrangement parameters mostly focus on the analysis of the influence of single factors, lacking stable and engineering-applicable evaluation methods for the weakening characteristics of rock ridges between cutters under the coupled effect of cutter spacing and penetration, the load evolution law in the stable cutting stage, and its quantitative correlation with rock breaking efficiency.

[0005] In summary, existing technologies suffer from the following main drawbacks: traditional finite element methods struggle to effectively handle large local deformations and discontinuous fractures during rock breaking; conventional element deletion easily leads to mass non-conservation and distortion of the breaking process; constant thrust loading methods exhibit poor numerical stability and insufficient comparability; and there is a lack of parameter optimization analysis methods for dual-roller cutters that balance computational stability, physical realism, and engineering applicability. Therefore, a novel numerical simulation and parameter optimization scheme for roller cutter rock breaking is urgently needed. Summary of the Invention

[0006] To address the problems existing in the background technology, this invention proposes a numerical simulation and parameter optimization method for TBM double-roller rock breaking based on FEM-SPH adaptive transformation. It aims to solve the technical problems of existing pure finite element simulation, such as mesh distortion, poor calculation stability under constant thrust loading, and insufficient consistency of parameter comparison, which are prone to occur in the large deformation and fracture splash stages of roller rock breaking. It provides a reliable numerical basis for the selection of roller layout and tunneling parameters that takes into account both calculation accuracy and efficiency.

[0007] To achieve the above objectives, the present invention adopts the following solution:

[0008] A numerical simulation and parameter optimization method for TBM twin-roll cutter rock breaking based on FEM-SPH adaptive transformation includes the following steps: Step 1: Construct a three-dimensional double-roll cutter rock breaking calculation model. The calculation model includes a rock model and a double-roll cutter model, and defines the contact relationship, boundary conditions and loading path of the calculation model. Step 2: Assign the rock model an elastic-plastic damage constitutive relation and set an adaptive conversion criterion for finite element elements to smooth particle hydrodynamics (SPH) particles. Step 3: Apply boundary conditions to the model and perform step-by-step loading control, which involves pressing in first and then cutting. Step 4: Perform FEM-SPH adaptive coupling solution. In the initial stage, the rock is described with a finite element mesh. During the solution process, when the local rock elements satisfy the adaptive transformation criterion, the fracture evolution of the material is characterized by the state inheritance particle transformation method so that it can continue to participate in subsequent calculations. Step 5: Extract response data and divide the stable cutting stage according to load characteristics, and discard data from the transient transition stage; Step 6: Evaluate the rock-breaking effect of the dual-roll cutter synergy under different cutter spacing and / or different penetration depth conditions, and output the optimal parameters.

[0009] Optionally, in step 1, the rock model is divided into a core rock-breaking zone and a peripheral rock mass zone; wherein, the core rock-breaking zone is located directly below the running trajectory of the double cutter and in the inter-cutter interference region between the two cutters, and the grid density of the region is higher than that of the peripheral rock mass zone; the cutters in the double cutter model are defined as discrete rigid bodies, and the translation and rotation of the cutters are centrally controlled through a central reference point.

[0010] Optionally, in step 2, the rock elastoplastic damage constitutive relation is constructed by combining the pressure-related yield criterion with the shear damage model; wherein, the pressure-related yield criterion is the linear Drucker-Prager yield criterion. The adaptive transformation criterion is used in the core rock-breaking zone, and unit replacement is performed when any of the following conditions are met: Equivalent plastic strain criterion, i.e., the cumulative equivalent plastic strain of the rock unit reaches a preset critical failure strain, the expression of which is: , In the formula, The equivalent plastic strain of the rock element, The critical failure strain. To convert trigger parameters Damage variable criterion, that is, the damage variable of the rock element reaches the preset failure threshold.

[0011] Optionally, in step 3, a completely fixed constraint is applied to the bottom surface of the rock model, a normal displacement constraint is applied to the four sides of the rock model, and the top surface of the rock model is set as a free surface; a general contact algorithm is used to construct contact interaction between the cutter and the rock; the step-by-step loading includes a first step of simultaneously pressing the double cutters into the rock to a preset penetration depth, and a second step of applying a horizontal velocity to complete the cutting simulation while keeping the penetration depth unchanged.

[0012] Optionally, in step 4, the state inheritance particle transformation method includes: deleting the failed finite element elements from the computational domain; Smooth particle hydrodynamic particles are generated at the corresponding positions of the failed finite element elements. The newly generated smooth particle hydrodynamic particles inherit the mass, momentum, and stress-strain state variables of the original finite element at the moment of failure. This allows the smooth particle hydrodynamic particles to continue to interact with the undamaged unit and the surface of the hob.

[0013] Optionally, in step 5, the response indicators include at least the hob vertical force, hob rolling force, plastic strain, damage variable, fracture volume, crack penetration characteristics, and cutting coefficient; the analysis of the response data is only for the load data in the stable cutting stage, and the statistical analysis includes extracting the average value, peak value, minimum value, standard deviation, fluctuation amplitude, and other relevant statistics of the load data.

[0014] Optionally, in step 6, the optimization of the cutter spacing parameters includes: setting multiple different cutter spacing conditions under the same penetration depth, extracting the crushing volume, cutter-to-cutter ridge damage index, crack penetration index, average vertical force, and average rolling force for each condition; evaluating each cutter spacing condition using a comprehensive evaluation function or rule-based discrimination method, with the optimization objectives being increased crushing volume, sufficient weakening of cutter-to-cutter ridges, crack penetration, and no excessive increase in load, to determine the optimal cutter spacing and optimal range.

[0015] Optionally, the optimization of the penetration parameters includes: setting multiple different penetration conditions under the same cutter spacing, extracting the crushing volume, synergistic rock-breaking index, spalling efficiency index, average vertical force, average rolling force, and unit rock-breaking energy consumption for each condition; evaluating each penetration condition using a comprehensive evaluation function or rule-based discrimination method, with the optimization objectives of enhancing synergistic rock-breaking effect, improving spalling efficiency, and reducing unit rock-breaking energy consumption, while simultaneously meeting the constraints of equipment load-bearing capacity and cutter life, and determining the optimal penetration and optimal range.

[0016] Optionally, the comprehensive evaluation function is constructed according to the following steps: The extracted evaluation indicators for each working condition were dimensionless, with the gain-type indicators using a normalization formula: , Cost indicators are normalized using the following formula: , In the formula, For the first i Normalized values ​​of the evaluation indicators corresponding to each working condition after dimensionless processing; For the first i The measured or calculated value of this evaluation index under each working condition; This represents the maximum value of the evaluation index across all comparison conditions. This is the minimum value of the evaluation index across all comparison conditions. Establish a comprehensive evaluation function, the expression of which is: , In the formula, J i For the first i The comprehensive evaluation value of each working condition; Vb,i , D r,i , F n,i , E s,i The first i The dimensionless value of the index corresponding to each working condition; w 1. w 2. w 3. w 4 represents the weight of each indicator, satisfying: , Calculate the comprehensive evaluation value for each working condition. J i ,by J i The working condition that has the maximum load and meets the preset load constraints is selected as the preferred working condition, and the adjacent interval of the better working condition is determined as the preferred range.

[0017] Optionally, the rule-based discrimination method is performed according to the following steps: For each working condition, extract the crack penetration index, the rock ridge weakening index between the cutter, the average vertical load, and the average rolling force or average rolling moment. Set a significant threshold for crack penetration, a sufficient threshold for weakening of rock ridges, an upper limit threshold for vertical load, and an upper limit threshold for rolling force or rolling moment, respectively. If a certain working condition simultaneously satisfies the following conditions: crack penetration index is not less than the significant crack penetration threshold, the ridge weakening index is not less than the sufficient ridge weakening threshold, the average vertical load is not greater than the upper limit threshold of the vertical load, and the average rolling force or average rolling moment is not greater than the corresponding upper limit threshold, then the working condition is determined to be the preferred working condition. If multiple working conditions meet the above conditions, then the crushing volume and unit rock-breaking energy consumption of each working condition are further compared. The working condition with a larger crushing volume and lower unit rock-breaking energy consumption is selected as the optimal working condition, and the adjacent working condition intervals that meet the conditions are determined as the preferred range.

[0018] The beneficial effects of this invention are as follows: This solution solves the technical problems of existing pure finite element simulations, such as mesh distortion, poor calculation stability under constant thrust loading, and insufficient consistency of parameter comparison, which are prone to occur during the large deformation and fracture spatter stages of cutter rock breaking. It provides a reliable numerical basis for the optimization of cutter layout and tunneling parameters, taking into account both calculation accuracy and efficiency. Specifically: (1) This scheme divides the core rock breaking zone and the outer rock mass zone in the rock model and implements a differentiated grid density arrangement. While ensuring high-precision analysis in the area directly affected by the cutter, it effectively controls the overall calculation scale of the model and is suitable for engineering needs of multi-condition parameter sensitivity analysis.

[0019] (2) The double roller cutter of this scheme adopts a three-dimensional discrete rigid body and controls translation and rotation through the reference point of the roller cutter center. Combined with the two-step loading path of pressing in first and then cutting with a fixed penetration, it can accurately simulate the whole process of TBM disc cutter from intrusion to rolling cutting, and reproduce the collaborative rock breaking characteristics such as the formation of rock ridges between cutters, weakening and block spalling.

[0020] (3) This scheme overcomes the problem of distortion in the description of fracture volume caused by conventional element deletion methods by setting an adaptive transformation criterion based on equivalent plastic strain or damage variables and adopting a state inheritance particle transformation method to transform finite element elements that meet the failure conditions into smooth particle hydrodynamic particles. The transformed SPH particles can continue to interact with unfailed rock mass elements and cutter surfaces, making the numerical simulation results closer to the actual rock breaking process.

[0021] (4) This scheme achieves quantitative evaluation of the rock-breaking effect of dual roller cutters under multiple working conditions through a comprehensive evaluation function or rule-based discrimination method, avoiding the subjectivity of traditional qualitative judgment. It can scientifically balance rock-breaking efficiency with cutter load and energy consumption, output optimal parameters and reasonable ranges, and provide engineering-convincing technical support for the optimization of TBM roller cutter layout and construction parameters. Attached Figure Description

[0022] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a schematic diagram of the three-dimensional double-roll cutter rock-breaking calculation model in an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the division of load time history stages and the extraction of indicators for the stable cutting stage in an embodiment of the present invention; Figure 4 This is a schematic diagram comparing the rock-breaking effect of dual roller cutters under different cutter spacing conditions in an embodiment of the present invention; Among them, (a) is Figure 4 (a) Equivalent plastic strain PEEQ contour plot of double roller cutter synergistic rock breaking under the condition of cutter spacing S=6mm; (b) is Figure 4 Equivalent plastic strain PEEQ contour plot of double roller cutter synergistic rock breaking under the condition of cutter spacing S=7mm; (c) is Figure 4 Equivalent plastic strain PEEQ contour plot of double roller cutter synergistic rock breaking under the condition of cutter spacing S=8mm; (d) is Figure 4 Equivalent plastic strain PEEQ contour plot of double roller cutter synergistic rock breaking under the condition of cutter spacing S=9mm; Figure 5 This is a schematic diagram comparing the rock-breaking effects of dual roller cutters under different penetration depths in embodiments of the present invention; wherein (a) is Figure 5 (a) Equivalent plastic strain PEEQ contour plot of double roller cutter synergistic rock breaking under the condition of intermediate penetration P=1.0mm; (b) is Figure 5 Equivalent plastic strain PEEQ contour plot of double roller cutter synergistic rock breaking under the condition of intermediate penetration P=1.0mm; (c) is Figure 5 Equivalent plastic strain PEEQ contour plot of double roller cutter synergistic rock breaking under the condition of intermediate penetration P=1.0mm; (d) is Figure 5 Equivalent plastic strain PEEQ contour plot of double roller cutter synergistic rock breaking under the condition of medium penetration P=1.0mm; Figure 6 This is a schematic diagram of the TBM hoisting and assembly in an embodiment of the present invention; Figure 7 This is a schematic diagram of a geological profile in an embodiment of the present invention; Figure 8 This is the finite element model in the embodiments of the present invention; Figure 9 This is a schematic diagram of the plastic strain of a double-roller cutter rotating and cutting granite in an embodiment of the present invention; Figure 10 This is a schematic diagram illustrating the influence of the tool spacing on the force on the hob in an embodiment of the present invention; Figure 11 This is a schematic diagram illustrating the effect of penetration on the force on the hob in an embodiment of the present invention. Detailed Implementation

[0023] To make the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the given embodiments are merely one implementation method and do not represent all embodiments.

[0024] Example 1 Combination Figure 1 This invention provides a numerical simulation and parameter optimization method for TBM double-roller rock breaking based on FEM-SPH adaptive transformation. It aims to solve technical problems in existing pure finite element simulations, such as mesh distortion during large deformation and fracture spatter stages of roller rock breaking, poor computational stability under constant thrust loading, and insufficient parameter consistency. This provides a reliable numerical basis for optimizing roller layout and tunneling parameters, balancing computational accuracy and efficiency. The method specifically includes the following steps: Step 1: Construct a three-dimensional twin-roll cutter rock-breaking calculation model, such as... Figure 2 As shown. The computational model includes a rock model and a double-roll cutter model, and defines the contact relationships, boundary conditions, and loading paths of the computational model.

[0025] The rock model is used to characterize the rock mass region to be fractured, and its geometric dimensions can be set differently according to different research objectives. In this embodiment, to balance the computational accuracy under the verification conditions and the computational efficiency of subsequent parameter analysis, the rock model is set as both a verification model and a parameter analysis model. The verification model is used to check the reliability of the numerical simulation, and the parameter analysis model is used to conduct sensitivity analysis on a series of conditions related to cutter spacing and penetration depth.

[0026] The dual-roller cutter model is used to characterize the synergistic rock-breaking effect of adjacent disc cutters. In this embodiment, the cutter is defined as a three-dimensional discrete rigid body, and its translation and rotation are uniformly controlled through the cutter center reference point. This setting can highlight the control effect of nonlinear failure of rock material on the overall response while ensuring solution efficiency.

[0027] To balance computational accuracy and cost, a local mesh refinement strategy is adopted in the rock model. Specifically, the area directly below the running trajectory of the double cutter and the interference region between the two cutters is designated as the core rock-breaking zone. A high-density finite element mesh is arranged in the core rock-breaking zone to improve the analytical ability of local behaviors such as crushing under the cutter, crack initiation, weakening of rock ridges, and block spalling. A sparser mesh is used in the outer rock mass far from the cutter action area to reduce the overall computational load.

[0028] By adopting the above modeling method, we can effectively improve the overall computational efficiency of the model while ensuring the accuracy of numerical solution in the action area of ​​the hob, and lay a reliable foundation for subsequent FEM-SPH adaptive transformation analysis.

[0029] Step 2: Establish the rock constitutive model and adaptive transformation criterion. After completing the geometric and mesh model construction in Step 1, assign the rock model an elastic-plastic damage constitutive relation and set an adaptive transformation criterion for finite element elements to SPH particles.

[0030] In this embodiment, a rock constitutive model is established by combining a pressure-dependent yield criterion with a shear damage model. Preferably, the pressure-dependent yield criterion is the linear Drucker-Prager yield criterion, whose yield function is expressed as: , In the formula, The equivalent stress is a deviatoric stress function. For equivalent hydrostatic pressure, Let be the friction angle. This is the cohesion parameter.

[0031] The advantage of using the above-mentioned linear Drucker-Prager yield criterion is that its yield surface is smooth in the principal stress space, which overcomes the convergence difficulty caused by sharp corners in the numerical calculation of Mohr-Coulomb type yield surfaces. It is suitable for the calculation of pressure-related brittle materials such as rocks and concrete in an explicit dynamic framework.

[0032] In this embodiment, equivalent plastic strain is used as the primary criterion for the rock to enter plastic yield and subsequent failure process, while damage variable is used as an auxiliary descriptive quantity. After the rock enters plastic yield, a shear damage model is introduced to describe the material stiffness degradation and bearing capacity reduction. The damage variable D is used to characterize the evolution degree of microcrack initiation, propagation, and aggregation within the material, and establishes a monotonically increasing relationship with the cumulative equivalent plastic strain. As the equivalent plastic strain accumulates, the damage variable gradually increases; when the cumulative equivalent plastic strain reaches the preset critical failure strain, the element enters a macroscopic failure state and triggers the adaptive transformation from FEM to SPH. The two are usually related through a damage evolution equation, namely: , in, This represents the cumulative equivalent plastic strain. The damage variable is not generated independently of the equivalent plastic strain, but rather gradually increases from 0 to 1 as the equivalent plastic strain accumulates. A linear relationship is adopted, i.e.: , For cumulative equivalent plastic strain; The equivalent plastic strain at the onset of damage; The critical equivalent plastic strain corresponding to complete failure; D ∈[0,1], where D =0 indicates no damage. D =1 indicates that the material has completely failed.

[0033] To achieve a local adaptive conversion from finite element method to SPH particle method, based on the aforementioned rock plastic damage and macroscopic failure judgment logic, an adaptive conversion criterion directly related to plastic strain accumulation and damage evolution is established in the core rock-breaking zone. Unit replacement is executed when any of the following conversion trigger conditions are met: Equivalent plastic strain criterion: The cumulative value of the equivalent plastic strain of the rock element reaches the preset critical failure strain; Damage variable criterion: The damage variable of the rock element reaches the preset failure threshold.

[0034] The expression for the equivalent plastic strain criterion is as follows: , In the formula, The equivalent plastic strain of the rock element, The critical failure strain. This is for converting trigger parameters.

[0035] when When the value reaches or exceeds 1, the rock element is considered to have undergone macroscopic fracture, triggering an adaptive transformation from finite element element to SPH particle. By setting the transformation criterion to be related to plastic strain and / or damage variables, the particle transformation can be made to better reflect the actual physical process of rock transitioning from a continuous medium state to a fragmented discrete state.

[0036] Step 3: Apply boundary conditions and perform step-by-step loading control within the explicit dynamics framework to realistically simulate the rock-breaking process of the TBM cutter penetrating, rolling, and shearing on the rock surface.

[0037] Specifically, regarding the application of boundary conditions: a completely fixed constraint is applied to the bottom surface of the rock model to limit the overall rigid body displacement; normal displacement constraints are applied to the four sides of the rock model to reduce the interference of boundary reflection and unreasonable lateral free deformation on the local rock breaking process; the top surface of the rock model is set as a free surface to allow the rock surface to undergo real deformation and spalling under the action of the roller cutter.

[0038] In addition, in this embodiment, a general contact algorithm is used to establish the contact relationship between the cutter and the rock. Specifically, the normal contact behavior adopts a hard contact model to prevent non-physical penetration between the cutter and the rock; the tangential contact behavior adopts a Coulomb friction model to reflect the frictional resistance of the cutter-rock interface during the rolling cutting process.

[0039] This embodiment differs from the traditional method of directly applying constant thrust. It employs a two-step loading path with a fixed penetration depth, comprising: First, applying vertical displacement control to the cutter reference point, causing the two cutters to simultaneously press into the rock to the preset penetration depth; Second, while maintaining a constant penetration depth, applying a constant horizontal velocity along the cutting direction to the cutter reference point and releasing the rotational freedom of the cutters around their central axis, allowing the cutters to passively rotate under the action of rock-cutting friction, thereby simulating the actual cutting process. This two-step loading method, first pressing in and then cutting, effectively avoids numerical oscillations and solution instability problems caused by directly applying constant thrust. It also enables a unified standard for loading control methods under different working conditions, improving the comparability of cutter load and rock-breaking performance.

[0040] Step 4: Perform FEM-SPH adaptive coupling solution using an explicit dynamics solver.

[0041] In this embodiment, during the initial solution stage, the entire rock model is described by a finite element mesh to fully leverage the efficiency of the finite element method in stress wave propagation, contact boundary treatment, and constitutive coupling in continuous media. When a local rock element satisfies the adaptive transformation criterion under the action of the roller cutter, the material fracture evolution is characterized by a state inheritance particle transformation method to continue participating in subsequent calculations, specifically including: (1) Remove the failed finite element from the original finite element calculation domain so that it no longer bears subsequent loads in the form of a continuum element; (2) Generate one or more SPH particles at the corresponding positions of the failed finite element elements to continue characterizing the fragmentation evolution of the region in the form of discrete particles. (3) The newly generated SPH particles inherit the mass, momentum, stress, strain, velocity and other state variables of the original finite element at the moment of failure, thereby ensuring the continuity of mass and momentum transfer before and after the conversion; (4) The SPH particles continue to interact with the unfailed rock units and the cutter surface through a general contact algorithm to simulate the crack propagation, block separation and debris scattering process.

[0042] Compared to traditional unit deletion failure algorithms, this embodiment adopts a state inheritance-based particle transformation method, which can effectively avoid defects such as model quality loss and fragmentation volume distortion caused by direct unit deletion; at the same time, it can retain the subsequent motion trajectory and contact collision behavior information of rock fragments, thereby more realistically restoring the evolution characteristics of the entire process of rock breaking by the roller cutter.

[0043] Step 5: Extract response data and divide the process into stable cutting stages based on load characteristics, and discard data from transient transition stages.

[0044] After completing the coupled solution, the response data of the entire cutting process is first extracted, identified, and statistically analyzed. The response indicators include at least the hob vertical force, hob rolling force, plastic strain, damage variables, fracture volume, crack penetration characteristics, and cutting coefficient. Specifically, the vertical force and rolling force are obtained through the hob reference point reaction force; the plastic strain and damage distribution are obtained through field variable output; the fracture volume is obtained through fracture region volume statistics or particle region statistics; and the cutting coefficient is calculated through the relationship between the vertical force and the rolling force.

[0045] To improve the consistency of parameter comparisons under different working conditions, this embodiment divides the rock-breaking process of the roller cutter into a loading stage and a stable cutting stage based on the load time history. Specifically, the time history curves of the vertical force and / or rolling force of the roller cutter are first extracted, with the moment when the roller cutter initially contacts the rock as the starting point for analysis. The loading stage corresponds to the process of the roller cutter gradually pressing in from initial contact until a stable groove is formed. During this stage, the roller cutter and the rock gradually establish a stable contact area, the load rises rapidly and usually shows a significant peak, exhibiting obvious transient characteristics. When the load curve, after experiencing the initial peak, enters a segment that fluctuates slightly around a certain mean and the overall trend no longer continues to rise or fall, this segment is determined to be the stable cutting stage. To improve the objectivity of the division, the moving average curve, the rate of change of slope, and the fluctuation range can be used for auxiliary judgment: when the moving average slope of the load time history approaches zero and the load fluctuation remains within a preset range for a continuous period of time, the roller cutter is considered to have entered the stable cutting stage. During the stable cutting phase, the hob continues cutting while maintaining a predetermined penetration and cutting speed. The load fluctuates around a certain average value, exhibiting periodic or quasi-periodic characteristics of crushing, crack propagation, and rock fragment detachment. For example... Figure 3 As shown in the figure, the phased changes in the time history response of the vertical force of the cutter during the rock-breaking process of the double-roller cutter are reflected. The figure clearly divides the rock-breaking process into a loading stage and a stable cutting stage: in the loading stage, the cutter and rock gradually establish a stable contact relationship from initial contact, and the vertical force rapidly increases and reaches its initial peak; in the stable cutting stage, the vertical force fluctuates around a relatively stable average value, indicating that the rock-breaking process enters a cyclical evolution state of "local crushing - crack propagation - rock fragment spalling". The figure also illustrates that extracting only the statistical indicators of the stable cutting stage can more accurately reflect the stress and collaborative rock-breaking characteristics of the cutter under different working conditions.

[0046] Therefore, based on the above, to avoid interference from the initial transient contact and indentation processes on the evaluation results of different working conditions, this embodiment excludes transient data during the loading stage and only performs statistical analysis on the load data during the stable cutting stage, extracting the average, peak, minimum, standard deviation, fluctuation amplitude, and related statistics. The average value is used to characterize the overall stress level of the hob during the stable rock-breaking process; the peak value reflects the instantaneous load response caused by local crack penetration or rock fragment spalling; and the fluctuation amplitude and standard deviation are used to measure the strength of load fluctuations within the stable cutting stage. Through the above classification and analysis methods, the accuracy and consistency of comparisons of parameters such as tool spacing and penetration depth can be effectively improved.

[0047] Step 6: Evaluate the rock-breaking effect of the dual-roll cutter synergy under different cutter spacing and / or different penetration depth conditions, and output the optimal parameters.

[0048] In this embodiment, a comprehensive evaluation function or rule-based discrimination method is used to evaluate the working conditions of each cutter spacing and each penetration depth. The comprehensive evaluation function is used to uniformly quantify and compare the rock-breaking effect of the dual-roller cutter under different working conditions. Its basic process is as follows: first, extract rock-breaking effect indicators, cutter-to-cutter ridge damage indicators, load indicators, and energy consumption indicators for each working condition; then, eliminate dimensional differences through dimensionless processing; finally, construct a comprehensive evaluation value according to set weights, and select the working condition with the highest comprehensive evaluation value as the optimal result. The specific steps are as follows: Step 6.11: Extract evaluation indicators for each working condition.

[0049] Regarding the first i For each working condition, the following indicators are extracted: (1) Crushed volume V b,i It is used to characterize the degree of overall rock erosion and fragmentation. V b,i The larger the value, the better the rock-breaking effect; (2) Damage index of inter-knife rock ridge D r,i The average equivalent plastic strain of the rock ridge region between the blades, the volume fraction of the damage element, or the proportion of the plastic zone area can be used to characterize it. D r,i The larger the value, the more thoroughly the inter-ridge weakens; (3) Average vertical force F n,i This index is used to characterize the normal load level of the hob. The smaller the index, the better it is for controlling tool wear and equipment load. (4) Energy consumption per unit of rock breaking E s,i This value characterizes energy utilization efficiency, with a lower value being better. Unit rock-breaking energy consumption can be defined as the ratio of input work to the volume of rock broken during the stable cutting stage, i.e. , In the formula, W i For the first i The input work during the stable cutting phase of a given operating condition. This can be further expressed as: , In the formula, F n It is a vertical force. F r For rolling force, and These represent the velocities in the corresponding directions; when the penetration depth remains constant during the stable cutting phase, it can also be approximated as follows: , In the formula, To stabilize the average rolling force during the cutting stage, L i This represents the effective cutting displacement of the hob.

[0050] Step 6.12: Perform dimensionless processing on the indicators.

[0051] Because different indicators have different dimensions, they need to be normalized. For gain-type indicators that are "the larger the better," such as crushing volume... V b and rock ridge damage index D r ,use: , For cost-related indicators where "the smaller the better," such as average vertical force... F n Energy consumption per unit of rock breaking E s ,use: , In the formula, For the first i Normalized values ​​of the evaluation indicators corresponding to each working condition after dimensionless processing; For the first i The measured or calculated value of this evaluation index under each working condition; This represents the maximum value of the evaluation index across all comparison conditions. This is the minimum value of the evaluation index among all the comparison conditions.

[0052] After processing, the dimensionless values ​​of each indicator are all in the range of [0,1], and the larger the value, the better the indicator.

[0053] Step 6.13: Construct a comprehensive evaluation function.

[0054] After dimensionless transformation, a comprehensive evaluation function is established: , in, J i For the first i The comprehensive evaluation value of each working condition; V b,i , D r,i , F n,i , E s,i The first i The dimensionless value of the index corresponding to each working condition; w 1.w 2. w 3. w 4 represents the weight of each indicator, satisfying: , In this embodiment, if a greater emphasis is placed on the rock-breaking effect, the [performance rating] can be appropriately increased. w 1 and w 2; If greater emphasis is placed on tool life and construction economy, the tool life can be appropriately increased. w 3 and w 4. For example, one could take: , The primary goal is to maximize the volume of rock breaking, while also taking into account the sufficient weakening of rock ridges between the cutters, reasonable control of vertical force, and reduction of energy consumption per unit of rock breaking.

[0055] Step 6.14: Determine the preferred operating conditions and preferred range.

[0056] Calculate the comprehensive evaluation value for each working condition. J i Then, sort them according to the numerical value. When a certain working condition... J i When the value is at its maximum, this operating condition is determined as the preferred operating condition; when several adjacent operating conditions are at their maximum... J i When all parameters are close to their maximum values, and simultaneously meet constraints such as vertical force not exceeding the equipment's allowable upper limit and unit rock-breaking energy consumption not significantly deteriorating, the parameter ranges corresponding to these working conditions are determined as the preferred ranges.

[0057] Furthermore, in this embodiment, for the evaluation of cutter spacing, multiple cutter spacing conditions are set up for numerical simulation, and the vertical load of the cutter, rolling torque, rock fragmentation volume, degree of plastic strain development of rock ridges between cutters and crack penetration and propagation characteristics are calculated and analyzed under each condition.

[0058] When the cutter spacing is too small, the overlapping areas of the double-roller cutter's rock-breaking action are too high. Although this can effectively weaken the rock ridges between the cutters, it easily leads to excessive rock fragmentation and a significant increase in ineffective energy consumption. When the cutter spacing is too large, the rock-breaking areas of each double-roller cutter tend to be independent, making it difficult for the rock ridges between the cutters to undergo sufficient plastic failure, and the collaborative rock-breaking effect of the rollers is significantly weakened. Based on this, this embodiment uses increasing the fragmentation volume, sufficient weakening of the rock ridges between the cutters, and crack penetration without excessive load increase as comprehensive optimization objectives to determine the optimal range of cutter spacing.

[0059] Specifically, the optimal range of cutter spacing is quantitatively determined based on numerical simulation results by establishing a comprehensive evaluation criterion that considers rock breaking effect, ridge weakening, and load control through a comprehensive evaluation function. The specific steps are as follows: Step 6.21: Set different tool spacing conditions under the same penetration depth, for example...S Numerical simulations of rock breaking with dual roller cutters were performed for cutter spacing of 6, 7, 8, 9, and 10 mm, respectively, and the response results during the stable cutting stage were extracted. For each cutter spacing condition, the following evaluation indicators were extracted: (1) Crushed volume V b Used to characterize the overall degree of rock fragmentation and spalling; the larger the fragmented volume, the better the rock breaking effect. (2) Weakening index η between the rock ridges: It can be characterized by the average equivalent plastic strain of the rock ridge area between the rock ridges, the proportion of the area that reaches the plastic threshold, or the volume fraction of the damaged area. The larger η is, the more fully the rock ridge between the rock ridges is weakened. (3) Crack penetration index λ: It can be determined by whether the plastic zone between the two cuts is connected and whether the crack penetrates the rock ridge area. The higher the degree of crack penetration, the more obvious the synergistic rock breaking effect. (4) Average vertical force With average rolling force These parameters are used to characterize the load level of the hobbing cutter. If both are too high, it indicates that although rock breaking is enhanced, tool wear and equipment load increase simultaneously, which is not conducive to engineering applications.

[0060] Step 6.22: Normalize the above indicators and construct a comprehensive evaluation function. For example, the fracture volume, ridge weakening index, and crack penetration index can be used as gain-type targets, while the average vertical force and average rolling force can be used as constraint-type or penalty-type targets, establishing the following comprehensive evaluation formula: , in, w 1 w 5 is the weighting coefficient, which can be set according to the research focus; when more emphasis is placed on rock-breaking efficiency, it can be appropriately increased. w 1. w 2. w 3; When more attention is paid to tool life and equipment safety, the appropriate increase can be made. w 4. w 5.

[0061] Step 6.23: Under the premise that the load does not exceed the preset upper limit, evaluate the comprehensive value of each tool spacing working condition. J The selection process is as follows: If the crushing volume increases significantly under a certain cutter spacing, the plasticity of the rock ridge between the cutters is sufficiently weakened, the cracks can be stably connected, and the average vertical force and average rolling force do not show abnormal increases, then the cutter spacing is determined to be the preferred cutter spacing; if multiple adjacent cutter spacings perform well under the same conditions, then they are determined to be within the preferred range.

[0062] Combination Figure 4When the cutter spacing is 6 mm, the overlap of the two cutter action zones is too strong. Although the rock ridge between the cutters is significantly weakened, there is local over-crushing, resulting in excessive ineffective energy consumption. When the cutter spacing is 9 mm, the action zones of the two cutters tend to be independent, making it difficult for the rock ridge between the cutters to fully enter the plastic failure state, resulting in poor crack penetration and weakened synergistic rock-breaking effect. In contrast, when the cutter spacing is 7 mm, the plastic strain distribution in the rock ridge area between the cutters is more balanced, cracks are more likely to form and penetrate effectively, the crushing volume is larger, and the roller load does not increase significantly, resulting in the best overall effect. Although the 8 mm condition still has a certain synergistic rock-breaking effect, it has weakened compared to 7 mm. Therefore, in this embodiment, 7 mm can be determined as the preferred cutter spacing, and 7-8 mm can be determined as the preferred cutter spacing range.

[0063] In addition, in this embodiment, for the evaluation of penetration depth, multiple penetration depth conditions are set up to carry out numerical simulations, and the grooving width, failure depth, inter-tool coordination degree and load response in the stable cutting stage are compared under different penetration depth conditions.

[0064] As the penetration depth increases, the contact area between the cutter and the rock gradually expands, the stress level acting on the rock increases accordingly, the crack propagation capacity is enhanced, and the synergistic rock-breaking effect of the dual cutters usually improves. However, at the same time, the vertical load and rolling torque on the cutter also show a significant upward trend, leading to accelerated tool wear and increased equipment operating load. Therefore, this embodiment, while taking into account the constraints of equipment load-bearing capacity and tool life, focuses on enhancing the synergistic rock-breaking effect, improving stripping efficiency, and reducing unit rock-breaking energy consumption as the core optimization objectives, and optimizes the penetration depth parameter to determine its reasonable value range.

[0065] Specifically, the optimal penetration parameters are determined quantitatively based on numerical simulation results by establishing a comprehensive evaluation criterion that considers synergistic rock breaking effect, spalling efficiency, energy consumption, and load constraints through a comprehensive evaluation function. The specific operational steps are as follows: Step 6.31: Under the same cutter spacing condition, set different penetration depth conditions, such as P=1.0, 1.5, 2.0, 2.5, and 3.0 mm, and complete the numerical simulation of dual-roller cutter collaborative rock breaking respectively, and extract the response results of the stable cutting stage. For each penetration depth condition, extract the following evaluation indicators: (1) Crushed volume V b Used to characterize the overall spalling and fracturing effect of rocks; the larger the fracturing volume, the stronger the rock-breaking ability. (2) Synergistic rock breaking index η: can be characterized by the average equivalent plastic strain of the rock ridge area between the cutters, the proportion of the plastic zone area or the volume fraction of the damaged zone. The larger η is, the more obvious the synergistic effect of the double roller cutters is. (3) Peeling efficiency index λ: It can be characterized by the degree of crack penetration, the range of rock fragments peeling or the formation of continuous peeling. The larger λ is, the easier it is for the rock to form stable peeling. (4) Average vertical force With average rolling force Used to characterize the hob load level; if both increase significantly, it means that tool wear and equipment operating load are increasing simultaneously. (5) Energy consumption per unit of rock breaking E s Used to evaluate energy utilization efficiency, it can be determined by the ratio of the work done by the hobbing cutter to the crushing volume during the steady cutting stage. E s The smaller the value, the lower the energy required to break up a unit volume of rock, and the better the economic efficiency.

[0066] Step 6.32: Normalize the above indicators and construct a comprehensive evaluation function. For example, the crushing volume, synergistic rock-breaking index, and stripping efficiency index can be used as gain-type objectives, while the unit rock-breaking energy consumption, average vertical force, and average rolling force can be used as constraint-type or penalty-type objectives, establishing the following comprehensive evaluation formula: , in, w 1 w 6 is a weighting coefficient, which can be set according to the engineering focus; when rock breaking efficiency is emphasized, it can be appropriately increased. w 1. w 2. w 3; When more attention is paid to tool life, equipment safety, and construction economy, the appropriate increase can be made. w 4. w 5. w 6.

[0067] Step 6.33: Under the constraints of equipment load-bearing capacity and tool life, evaluate the comprehensive value of each penetration depth condition. J The parameters are sorted. If the volume of broken rocks increases significantly, the plasticity of the rock ridges between the cutters is sufficiently weakened, the crack penetration and rock fragment spalling are relatively stable at a certain penetration depth, and the unit rock breaking energy consumption is low, and the average vertical force and average rolling force do not show abnormal increases, then the penetration depth is determined to be the preferred penetration depth; if multiple adjacent penetration depth conditions all perform well, then it is determined to be within a reasonable range.

[0068] Combination Figure 5When the penetration depth is 1.0-1.5 mm, the cutting edge has a shallow impact on the rock mass, the plastic zone is limited, the rock ridges between the cutters are difficult to weaken sufficiently, and the crack penetration and stable spalling effects are weak. When the penetration depth increases to 2.0 mm, the plastic zone and crack propagation range increase significantly, and the synergistic rock-breaking effect is enhanced. When the penetration depth is 2.5 mm, the rock ridges between the cutters are weakened more fully, cracks are more likely to form and effectively penetrate, rock spalling is more stable, the broken volume is significantly increased, and the unit rock-breaking energy consumption remains at a reasonable level, and the cutting edge load has not increased excessively. Through simulation, when the penetration depth continues to increase to 3.0 mm, although the rock-breaking ability is further enhanced, the average vertical force and average rolling force increase significantly, the cutter wear and equipment load increase simultaneously, and the overall economic efficiency decreases. Based on the above results, 2.5 mm can be determined as the preferred penetration depth, and 2.0-2.5 mm can be determined as the reasonable penetration depth range.

[0069] In another embodiment, parameter optimization can also be carried out using rule-based discrimination based on actual engineering needs: First, key indicators such as crack penetration, weakening of rock ridges between cutters, vertical load, and rolling moment are extracted for each working condition. These are then compared with preset thresholds. If a working condition simultaneously meets all the optimal conditions, it is determined to be the optimal working condition. If multiple working conditions meet the conditions, they are further sorted according to the principles of larger crushing volume, lower unit rock-breaking energy consumption, or more stable load to determine the optimal parameters or preferred range. The specific steps are as follows: Step 6.41: Extract discriminant indicators.

[0070] For the i-th operating condition, the following indicators are extracted: (1) Crack penetration index λ i This is used to characterize whether an effective connection has been formed between two hobs; (2) Weakening index η of inter-knife ridge i It is used to characterize whether the rock ridges between the blades have fully entered the state of plastic failure or damage; (3) Average vertical load F n,i , used to characterize the normal force level of the hob; (4) Average rolling torque M i or average rolling force F r,i It is used to characterize the rolling cutting resistance level of a hob.

[0071] Among them, the crack penetration index λ i The determination can be made based on whether the plastic zone between the two cuts is connected, whether the damaged zone is penetrating, or whether the crack path crosses the rock ridge between the cuts; the weakening index η of the rock ridge between the cuts. iIt can be expressed by the average equivalent plastic strain of the rock ridge region between the blades, the volume fraction of damage, or the proportion of the plastic zone area.

[0072] Step 6.42: Set the rule discrimination threshold.

[0073] Based on engineering experience, equipment load-bearing capacity, and the statistical range of simulation results, the following discrimination criteria are set: (1) Significantly continuous crack: , Where, λ c The threshold for determining crack penetration; (2) The rock ridges between the knife-edges are sufficiently weakened: , Where, η c The threshold for weakening rock ridges; (3) The vertical load does not exceed the allowable upper limit: , (4) The rolling torque or rolling force does not exceed the allowable upper limit: , in, F n,lim , M lim or F r,lim This is a pre-set upper limit based on the equipment's load-bearing capacity, tool strength, and safety margin.

[0074] Step 6.43: Perform rule discrimination.

[0075] If a certain working condition is met simultaneously: ; Then the operating condition is determined to be the preferred operating condition and output.

[0076] If rolling force is used as the criterion, it can be written as: ; Step 6.44: Determine the optimal operating conditions or preferred range.

[0077] When only one working condition meets the above rules, it is directly determined as the optimal working condition; when multiple working conditions simultaneously meet the above rules, their crushing volumes are further compared. V b,i Unit rock-breaking energy consumption E s,i Or load fluctuation amplitude Δ FiThe optimal working condition is selected based on the following criteria: larger crushing volume, lower unit rock-breaking energy consumption, and more stable load fluctuation. If multiple adjacent working conditions perform well, their corresponding parameter ranges can be determined as the preferred range. For example, in the optimization of the cutter spacing parameter, if both S=7mm and S=8mm satisfy the conditions of significant crack penetration, sufficient weakening of rock ridges between cutters, and no load exceeding the limit, and S=7mm has a larger crushing volume and lower unit rock-breaking energy consumption, then S=7mm is determined as the optimal cutter spacing, and 7-8mm is determined as the preferred range. Similarly, in the optimization of the penetration parameter, if both P=2.0 mm and P=2.5 mm satisfy the above rules, and P=2.5 mm has a more stable crack penetration and spalling effect, then P=2.5 mm is determined as the optimal penetration, and 2.0-2.5 mm is determined as a reasonable value range.

[0078] Ultimately, the results output by the method in this embodiment include, but are not limited to: optimal cutter spacing, optimal penetration, load level under corresponding working conditions, crushing volume, cutting coefficient, and a comprehensive evaluation conclusion on the rock-breaking effect of the dual-roll cutter synergy, providing accurate parameter support for practical engineering applications.

[0079] Simulation Example: To verify the effectiveness and accuracy of the numerical simulation and parameter optimization method for TBM double-roll cutter rock breaking based on FEM-SPH adaptive conversion proposed in this invention, this embodiment combines the actual working conditions of a TBM construction section of a certain urban rail transit project to explain in detail the specific implementation process and verification results of this method.

[0080] The left line of this section has a construction length of approximately 819 m (two sections), and the right line has a length of approximately 648 m. The tunnel adopts a standard single-bore, single-track circular cross-section. The horizontal alignment of the section is a straight section with a line spacing of 14-16 m, a soil cover thickness of 20-29 m, and a maximum longitudinal slope of 25‰.

[0081] Within this section of the site, the Quaternary overburden thickness ranges from 0.40 to 12.20 meters, primarily composed of Quaternary Holocene artificial fill, Holocene alluvial-diluvial deposits, and Upper Pleistocene alluvial-diluvial silty clay layers. The bedrock is Late Yanshanian intrusive granite, with localized granite porphyry and fine-grained granite dikes. Due to faulting, some boreholes reveal tectonic rocks of corresponding lithologies. The geological profile of the site is as follows. Figure 7 As shown.

[0082] Based on the numerical calculation model established above, the following steps are implemented sequentially according to the process described in this invention: Step A1: Establish a three-dimensional rock-breaking calculation model for double-roll cutters, such as... Figure 8As shown; among them, the rock size of the verification model is 100 mm × 100 mm × 40 mm, the rock size of the parameter analysis model is 80 mm × 120 mm × 30 mm, and the diameter of the double roller cutter is 40 mm.

[0083] Step A2: Assign the linear Drucker-Prager yield criterion and shear damage model to the rock, set the core rock breaking zone below the cutter trajectory and in the inter-cutter interference area, and assign the FEM-SPH adaptive transformation property.

[0084] Step A3: Apply boundary conditions and loading path, where the hobbing cutter adopts a two-step loading method with a fixed penetration depth: First, apply vertical displacement control to the two hobbing cutters simultaneously, pressing them into the rock surface to the preset penetration depth value; Second, while keeping the penetration depth constant, apply a horizontal velocity along the cutting direction to the hobbing cutter, and at the same time release the rotational degree of freedom of the hobbing cutter around its own central axis, so that the hobbing cutter passively rotates under the action of friction, so as to realistically simulate the actual cutting process.

[0085] Step A4: Perform FEM-SPH coupled solution under the explicit dynamics framework to continuously track the complete failure evolution process of the rock from local crushing, crack initiation and propagation, rock ridge penetration to rock block spalling and debris dispersion.

[0086] Step A5: Extract the complete time history curve of the vertical force of the hob, and divide it into the transient loading stage and the stable cutting stage according to the load characteristics. Extract the vertical force, rolling force, plastic strain, crushing volume and cutting coefficient of the stable cutting stage to ensure the consistency and objectivity of the data comparison between working conditions.

[0087] Step A6: Conduct tool spacing and penetration analysis separately, with tool spacing set to 6 mm, 7 mm, 8 mm, 9 mm and 10 mm, and penetration set to 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm and 3.0 mm; finally, based on the statistical results of the stable cutting stage, compare and analyze the different working conditions and complete the parameter optimization.

[0088] After completing the numerical simulations for the above working conditions, the rock-breaking characteristics and stress response under typical working conditions were extracted and analyzed, and the results are as follows: like Figure 9The plastic strain diagram of double-roller cutting granite with experimental parameters is presented. As shown in the figure, the equivalent plastic strain exhibits significant localization in spatial distribution: high strain is mainly concentrated near the circular motion trajectory of the two rollers, forming a continuous annular strain concentration zone; the rock mass area far from the cutter track is dominated by low strain, indicating that deformation and damage evolution are mainly controlled by the contact indentation and rolling shearing of the rollers, and the overall failure range is limited to the contact area between the rock and the rollers. Analysis based on the preset fracture strain threshold of 0.234 shows that the annular strain zone is mainly distributed in bluish-green to yellow, corresponding to PEEQ values ​​of approximately 0.06~0.20, indicating continuous plastic accumulation and compressive-shear failure in the contact area. Simultaneously, discrete high-strain points ranging from yellow to orange appear locally in the annular zone, with PEEQ values ​​close to 0.20-0.234, indicating that the strain further approaches the fracture strain threshold, reflecting the discontinuous failure characteristics of the rock breaking process: overall, it exhibits strain accumulation in a stable cutting groove, while localized rock fragments are spalled off by intermittently reaching the fracture threshold. Overall, the annular grooves in the rock are basically consistent with the shape of the test.

[0089] Figure 10 The influence of cutter spacing on the force characteristics of the hob is presented. The results show that, under the same penetration depth, the rolling force generally increases with increasing cutter spacing, indicating that increasing the cutter spacing will steadily increase the resistance required in the rolling direction. Furthermore, the greater the penetration depth, the higher the rolling force, and the increase in rolling force is more significant when the cutter spacing is larger, indicating that changes in cutter spacing have a greater impact on cutting resistance under high penetration depths.

[0090] Figure 11 The influence of penetration depth on the force on the hob is presented. As shown in the figure, the rolling force increases monotonically with increasing penetration depth P. At the same penetration depth, the larger the cutter spacing, the greater the rolling force. The curves do not intersect and show a consistent trend. With increasing penetration depth, the slope of the curve increases, and the growth of rolling force exhibits a non-linear accelerating characteristic. Simultaneously, the difference between different cutter spacings increases at higher penetration depths, indicating that increasing penetration depth makes the rolling force more sensitive to cutter spacing.

[0091] The above embodiments demonstrate that the method proposed in this invention successfully reproduces the entire process of cutter penetration into rock, crack propagation, ridge weakening, and block spalling. The simulated groove morphology matches the experimental results well, and the cutter stress variation pattern is consistent with engineering experience. Through multi-condition comparative analysis of the stable cutting stage, the influence trends of cutter spacing and penetration on rock-breaking performance can be effectively identified, and optimal parameter combinations can be determined. This verifies the effectiveness and accuracy of the method of this invention in numerical simulation of the cutter rock-breaking process, and can provide convincing technical support for the optimization of TBM cutter layout and construction parameters.

[0092] The specific embodiments of the present invention have been described in detail above with reference to the figures, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A numerical simulation and parameter optimization method for TBM twin-roll cutter rock breaking based on FEM-SPH adaptive transformation, characterized in that, Includes the following steps: Step 1: Construct a three-dimensional double-roll cutter rock breaking calculation model. The calculation model includes a rock model and a double-roll cutter model, and defines the contact relationship, boundary conditions and loading path of the calculation model. Step 2: Assign the rock model an elastic-plastic damage constitutive relation and set an adaptive conversion criterion for finite element elements to smooth particle hydrodynamics (SPH) particles. Step 3: Apply boundary conditions to the model and perform step-by-step loading control, which involves pressing in first and then cutting. Step 4: Perform FEM-SPH adaptive coupling solution. In the initial stage, the rock is described with a finite element mesh. During the solution process, when the local rock elements satisfy the adaptive transformation criterion, the fracture evolution of the material is characterized by the state inheritance particle transformation method so that it can continue to participate in subsequent calculations. Step 5: Extract response data and divide the stable cutting stage according to load characteristics, and discard data from the transient transition stage; Step 6: Evaluate the rock-breaking effect of the dual-roll cutter synergy under different cutter spacing and / or different penetration depth conditions, and output the optimal parameters.

2. The numerical simulation and parameter optimization method for TBM twin-roll cutter rock breaking based on FEM-SPH adaptive conversion as described in claim 1, characterized in that: In step 1, the rock model is divided into a core rock-breaking zone and a peripheral rock mass zone. The core rock-breaking zone is located directly below the running trajectory of the double cutter and in the inter-cutter interference area between the two cutters, and the grid density of the core rock-breaking zone is higher than that of the peripheral rock mass zone. The cutters in the double cutter model are defined as discrete rigid bodies, and the translation and rotation of the cutters are centrally controlled through a central reference point.

3. The numerical simulation and parameter optimization method for TBM twin-roll cutter rock breaking based on FEM-SPH adaptive conversion as described in claim 2, characterized in that: In step 2, the constitutive relation of rock elastoplastic damage is constructed by combining the pressure-related yield criterion with the shear damage model; wherein, the pressure-related yield criterion is the linear Drucker-Prager yield criterion. The adaptive transformation criterion is used in the core rock-breaking zone, and unit replacement is performed when any of the following conditions are met: equivalent plastic strain criterion, i.e., the cumulative value of the equivalent plastic strain of the rock element reaches the preset critical failure strain; damage variable criterion, i.e., the damage variable of the rock element reaches the preset failure threshold; wherein, the expression for the equivalent plastic strain criterion is: ， In the formula, The equivalent plastic strain of the rock element, The critical failure strain. This is for converting trigger parameters.

4. The numerical simulation and parameter optimization method for TBM twin-roll cutter rock breaking based on FEM-SPH adaptive conversion as described in claim 1, characterized in that: In step 3, a completely fixed constraint is applied to the bottom surface of the rock model, a normal displacement constraint is applied to the four sides of the rock model, and the top surface of the rock model is set as a free surface; a general contact algorithm is used to construct contact interaction between the cutter and the rock; the step-by-step loading includes the first step of simultaneously pressing the double cutters into the rock to a preset penetration depth, and the second step of applying a horizontal velocity to complete the cutting simulation while keeping the penetration depth unchanged.

5. The numerical simulation and parameter optimization method for TBM twin-roll cutter rock breaking based on FEM-SPH adaptive conversion as described in claim 1, characterized in that: In step 4, the state inheritance particle transformation method includes: deleting the failed finite element units from the computational domain; Smooth particle hydrodynamic particles are generated at the corresponding positions of the failed finite element elements. The newly generated smooth particle hydrodynamic particles inherit the mass, momentum, and stress-strain state variables of the original finite element at the moment of failure. This allows the smooth particle hydrodynamic particles to continue to interact with the undamaged unit and the surface of the hob.

6. The numerical simulation and parameter optimization method for TBM twin-roll cutter rock breaking based on FEM-SPH adaptive conversion as described in claim 1, characterized in that: In step 5, the response indicators include at least the hob vertical force, hob rolling force, plastic strain, damage variable, fracture volume, crack penetration characteristics, and cutting coefficient; the analysis of the response data is only for the load data in the stable cutting stage, and the statistical analysis includes extracting the average value, peak value, minimum value, standard deviation, fluctuation amplitude, and other relevant statistics of the load data.

7. The numerical simulation and parameter optimization method for TBM twin-roll cutter rock breaking based on FEM-SPH adaptive conversion as described in claim 1, characterized in that: In step 6, the optimization of the cutter spacing parameters includes: setting multiple different cutter spacing conditions under the same penetration depth, extracting the crushing volume, cutter-to-cutter ridge damage index, crack penetration index, average vertical force, and average rolling force for each condition; evaluating each cutter spacing condition using a comprehensive evaluation function or rule-based discrimination method, with the optimization objectives being increased crushing volume, sufficient weakening of cutter-to-cutter ridges, crack penetration, and no excessive increase in load, to determine the optimal cutter spacing and optimal range.

8. The numerical simulation and parameter optimization method for TBM twin-roll cutter rock breaking based on FEM-SPH adaptive conversion as described in claim 7, characterized in that: The optimization of penetration parameters includes: setting multiple different penetration conditions under the same cutter spacing, extracting the crushing volume, synergistic rock breaking index, spalling efficiency index, average vertical force, average rolling force, and unit rock breaking energy consumption for each condition; evaluating each penetration condition using a comprehensive evaluation function or rule-based discrimination method, with the optimization goals of enhancing synergistic rock breaking effect, improving spalling efficiency, and reducing unit rock breaking energy consumption, while meeting the constraints of equipment load-bearing capacity and cutter life, and determining the optimal penetration and optimal range.

9. The numerical simulation and parameter optimization method for TBM twin-roll cutter rock breaking based on FEM-SPH adaptive conversion as described in claim 8, characterized in that: The comprehensive evaluation function is constructed according to the following steps: The extracted evaluation indicators for each working condition were dimensionless, with the gain-type indicators using a normalization formula: ， Cost indicators are normalized using the following formula: ， In the formula, For the first i Normalized values ​​of the evaluation indicators corresponding to each working condition after dimensionless processing; For the first i The measured or calculated value of this evaluation index under each working condition; This represents the maximum value of the evaluation index across all comparison conditions. This is the minimum value of the evaluation index across all comparison conditions. Establish a comprehensive evaluation function, the expression of which is: ， In the formula, J i For the first i The comprehensive evaluation value of each working condition; V b,i , D r,i , F n,i , E s,i The first i The dimensionless value of the index corresponding to each working condition; w 1. w 2. w 3. w 4 represents the weight of each indicator, satisfying: ， Calculate the comprehensive evaluation value for each working condition. J i ,by J i The working condition that has the maximum load and meets the preset load constraints is selected as the preferred working condition, and the adjacent interval of the better working condition is determined as the preferred range.

10. The numerical simulation and parameter optimization method for TBM twin-roll cutter rock breaking based on FEM-SPH adaptive conversion as described in claim 8, characterized in that: The rule-based judgment method is performed according to the following steps: For each working condition, extract the crack penetration index, the rock ridge weakening index between the cutter, the average vertical load, and the average rolling force or average rolling moment. Set a significant threshold for crack penetration, a sufficient threshold for weakening of rock ridges, an upper limit threshold for vertical load, and an upper limit threshold for rolling force or rolling moment, respectively. If a certain working condition simultaneously satisfies the following conditions: crack penetration index is not less than the significant crack penetration threshold, the ridge weakening index is not less than the sufficient ridge weakening threshold, the average vertical load is not greater than the upper limit threshold of the vertical load, and the average rolling force or average rolling moment is not greater than the corresponding upper limit threshold, then the working condition is determined to be the preferred working condition. If multiple working conditions meet the above conditions, then the crushing volume and unit rock-breaking energy consumption of each working condition are further compared. The working condition with a larger crushing volume and lower unit rock-breaking energy consumption is selected as the optimal working condition, and the adjacent working condition intervals that meet the conditions are determined as the preferred range.

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