FDEM simulation method and system for large water-based deformation of tunnel expansive rock

Abstract

The invention discloses an FDEM simulation method and system for large water-based deformation of tunnel expansive rock, and relates to the technical field of rock mechanics and rock engineering. The method comprises the following steps: acquiring a water content time history curve, a linear expansion coefficient and function relation data of mechanical property parameters changing along with the water content of an expansive rock sample in a target tunnel; calibrating I-type and II-type fracture energy of the expansive rock sample under different water contents to obtain fracture energy parameters; embedding the water content time history curve, the linear expansion coefficient, the function relation data and the fracture energy parameters into an FDEM program, and constructing an excavation numerical model of the target tunnel; on the basis of the excavation numerical model, hydraulic property large deformation simulation is executed; in the simulation process, an expansive force effect is applied to a triangular unit which is below the water level, is adjacent to the fractured quadrilateral unit and is in contact with water, and a degradation effect of cohesive force and tensile strength is applied to a complete quadrilateral unit adjacent to the triangular unit. According to the invention, fine simulation of large water-rational deformation of the tunnel expansive rock is realized.

Description

Technical Field

[0001] The present invention relates to the field of rock mechanics and rock engineering technology, and in particular to a FDEM simulation method and system for hydraulic large deformation of tunnel expansion rock. Background Art

[0002] During tunneling in major infrastructure projects in my country (such as the Sichuan-Tibet Railway and the Central Yunnan Water Diversion Project) and underground mineral resource mining, tunneling inevitably encounters surrounding rocks containing expansive minerals, such as mudstone (referred to as expansive rock). Under the influence of groundwater infiltration, expansive rock undergoes large hydraulic deformation, threatening project safety. Numerical simulation is an important tool for revealing the catastrophic mechanisms and quantifying the deformation patterns involved.

[0003] However, existing numerical simulation methods have significant limitations: Continuous methods (such as the finite element method) struggle to simulate the initiation, propagation, and fragmentation of surrounding rock fracture networks; discontinuous methods (such as the discrete element method) lack accuracy in characterizing the continuous-discontinuous transition mechanism of rock masses. Neither approach can fully replicate the coupled process of progressive fracture and expansion deformation of surrounding rock at an engineering scale.

[0004] While the coupled finite element method (FDEM) can simulate the entire process from rock mass failure to block motion, its current applications focus on damage caused by mechanical loads (such as excavation unloading and stress concentration). Existing FDEM methods have yet to effectively simulate the unique hydrological mechanisms of expansive rock, where groundwater infiltration triggers expansive forces and mechanical parameter degradation in the surrounding rock, leading to large deformations. This results in a lack of reliable theoretical support for the prediction and prevention of these engineering disasters. Summary of the Invention

[0005] To solve the problems existing in the prior art, the present invention provides a FDEM simulation method and system for the hydraulic large deformation of tunnel expansive rock, which can realize the precise simulation of the hydraulic large deformation of tunnel expansive rock and provide reliable theoretical support for the prediction and prevention of such engineering disasters.

[0006] To achieve the above objectives, the present invention provides a FDEM simulation method for hydraulic large deformation of expansive rock in a tunnel, comprising:

[0007] Obtain the water content time history curve, linear expansion coefficient, and the functional relationship data of mechanical properties parameters with water content of the expansive rock sample in the target tunnel;

[0008] Calibrate the mode I and mode II fracture energies of the expansive rock sample at different water contents to obtain fracture energy parameters;

[0009] embedding the moisture content time history curve, linear expansion coefficient, functional relationship data and fracture energy parameters into an FDEM program, and constructing a numerical model of the excavation of the target tunnel;

[0010] A hydraulic large deformation simulation is performed based on the excavation numerical model. During the simulation, an expansion force effect is applied to the triangular units below the water level that are adjacent to the broken quadrilateral units and in contact with water, and a degradation effect of cohesion and tensile strength is applied to the intact quadrilateral units adjacent to the triangular units.

[0011] Optionally, the moisture content time history curve is obtained by conducting drying and immersion tests on cylindrical expansive rock samples.

[0012] Optionally, the mechanical performance parameters include elastic modulus, tensile strength and cohesion; the functional relationship data of the elastic modulus changing with moisture content is obtained by conducting a uniaxial compression test; the functional relationship data of the tensile strength changing with moisture content is obtained by conducting a Brazilian splitting test; the functional relationship data of the cohesion changing with moisture content is obtained by conducting a triaxial compression test.

[0013] Optionally, when determining the cohesion of expansive rock samples with different water contents in the triaxial compression test, the following formula is used:

[0014]

[0015] Where σ1 is the triaxial compressive strength, σ3 represents the confining pressure, and c is the cohesion of the expansive rock specimen; represents the internal friction angle of the expansive rock specimen and is assumed to be independent of the water content.

[0016] Optionally, the expansion force applied in the expansion force effect is calculated as follows:

[0017]

[0018] Where Δσ xx , Δσ yy are the normal expansion stresses in the x and y directions, Δσ xy , Δσ yx are the shear expansion stress in the x and y directions respectively, K is the bulk modulus, E is the elastic modulus, ν is the Poisson's ratio; β is the linear expansion coefficient, Δw t is the change in moisture content.

[0019] Optionally, the method further includes:

[0020] The nodal forces of the triangular element are determined by the following formula:

[0021]

[0022] Where, f xl 、f ylrepresents the nodal force of the triangle unit node l in the x and y directions, Δσ xx , Δσ yy It represents the expansion force in the x and y directions respectively, x m 、y m In turn, they represent the x and y coordinate values ​​of node m. n 、y n They represent the x and y coordinate values ​​of node n respectively; nodes l, m and n are three nodes arranged counterclockwise in the triangle unit.

[0023] Optionally, applying the expansion force effect includes:

[0024] Calculating a corresponding total expansion force value according to the current moisture content of the triangular unit;

[0025] determining an expansion force application ratio according to a current number of ruptured quadrilateral units adjacent to the triangular unit;

[0026] The total value of the expansion force is applied to the triangular unit according to the expansion force application ratio.

[0027] Optionally, the deterioration effect of applying cohesion and tensile strength includes:

[0028] Determining the corresponding cohesion degradation amount and tensile strength degradation amount according to the current moisture content of the triangular unit;

[0029] The cohesion degradation amount and the tensile strength degradation amount in a preset ratio are applied to the complete quadrilateral unit adjacent to the triangular unit.

[0030] Optionally, the expansion force effect and the degradation effect are both applied while ignoring the time delay of the water infiltration process.

[0031] The present invention also provides a FDEM simulation system for hydraulic large deformation of tunnel expansion rock, comprising:

[0032] A data acquisition unit is used to obtain the water content time history curve, linear expansion coefficient, and functional relationship data of mechanical performance parameters changing with water content of the expansive rock sample in the target tunnel;

[0033] a fracture energy calibration unit, used to calibrate the mode I and mode II fracture energies of the expansive rock sample at different water contents to obtain fracture energy parameters;

[0034] An embedding and construction unit, for embedding the moisture content time history curve, linear expansion coefficient, functional relationship data and fracture energy parameters into an FDEM program, and constructing an excavation numerical model of the target tunnel;

[0035] A simulation unit is used to perform hydraulic large deformation simulation based on the excavation numerical model; during the simulation process, an expansion force effect is applied to the triangular units below the water level that are adjacent to the broken quadrilateral units and in contact with water, and at the same time, a degradation effect of cohesion and tensile strength is applied to the intact quadrilateral units adjacent to the triangular units.

[0036] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0037] The FDEM simulation method for large hydraulic deformation of expansive rock in tunnels provided by the present invention obtains the water content time-history curve, linear expansion coefficient and mechanical performance parameters as a function of water content of the expansive rock specimen, and calibrates the Type I and Type II fracture energy parameters dynamically associated with the water content, thereby completely embedding the hydraulic action mechanism into the FDEM numerical framework for the first time. It can accurately construct a numerical model of the excavation of an expansive rock tunnel, and during the simulation process, apply the expansion force effect to the triangular units below the water level that are adjacent to the broken quadrilateral units and in contact with water, and simultaneously apply the degradation effect of cohesion and tensile strength to the adjacent intact quadrilateral units, thus breaking through the limitation of the existing FDEM method that can only simulate mechanical load failure.

[0038] The present invention completely reproduces the chain reaction process of expansive rock: "groundwater infiltration - generation of expansive force - degradation of mechanical parameters - hydraulic large deformation disaster", and realizes the FDEM fine simulation of the tunnel hydraulic large deformation disaster process, providing reliable data support for the prediction and prevention of hydraulic large deformation disasters of expansive rock in major projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0040] Figure 1 This is a schematic diagram of a method flow of a FDEM simulation method for hydraulic large deformation of expansive rock in a tunnel according to an embodiment of the present invention;

[0041] Figure 2 A schematic diagram of a time history curve of water content of a mudstone sample according to an embodiment of the present invention;

[0042] Figure 3 This is a schematic diagram of a fitting curve showing the relationship between the elastic modulus and the water content of a mudstone sample according to an embodiment of the present invention;

[0043] Figure 4 A schematic diagram of a fitting curve showing the relationship between the tensile strength and water content of a mudstone sample according to an embodiment of the present invention;

[0044] Figure 5 A schematic diagram of a fitting curve showing the relationship between the cohesion and water content of a mudstone sample according to an embodiment of the present invention;

[0045] Figure 6 A schematic diagram of a numerical model for excavation of an expansive rock tunnel according to an embodiment of the present invention;

[0046] Figure 7 A schematic diagram of the conversion principle of the expansion force into the triangular unit node force shown in an embodiment of the present invention;

[0047] Figure 8 This is a schematic diagram illustrating the calculation principle of the expansion force of a triangular unit and the parameter degradation of a quadrilateral unit according to an embodiment of the present invention;

[0048] Figure 9 This is a schematic diagram of the simulation results of large hydraulic deformation of expansive rock in a tunnel according to an embodiment of the present invention;

[0049] Figure 10 This is a schematic diagram of the module structure of the FDEM simulation system for hydraulic large deformation of tunnel expansive rock shown in an embodiment of the present invention. DETAILED DESCRIPTION

[0050] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0051] See also Figure 1 , Figure 1 The FDEM simulation method for large hydraulic deformation of tunnel expansion rock is shown in the following flow chart. The FDEM simulation method for large hydraulic deformation of tunnel expansion rock includes the following steps:

[0052] Step 101: Obtain a water content time history curve, a linear expansion coefficient, and functional relationship data of mechanical property parameters varying with water content of an expansive rock sample in a target tunnel.

[0053] The moisture content time history curve can be obtained by conducting drying and immersion tests on cylindrical expansive rock samples. For example, the cylindrical expansive rock sample is completely dried for at least 24 hours, then immersed for different periods of time, and the moisture content of the expansive rock sample is determined using the following formula:

[0054]

[0055] Where w t is the moisture content of the sample, m tis the mass of the water sample, and m0 is the mass of the dry sample.

[0056] In application, the processed cylindrical expanded rock sample can be thoroughly dried to constant weight, and its dry mass can be recorded. The dried expanded rock sample is then completely immersed in water, taken out at different immersion time points, and the surface is quickly wiped dry before being weighed. Using the mass data before and after, the moisture content corresponding to each time point is calculated (i.e., the mass percentage of water in the sample), and then these moisture content values ​​are connected in chronological order to form a curve describing the change of moisture content over time (moisture content time course curve); this curve reflects the speed at which the sample absorbs water and the saturation state that can eventually be reached. Taking the expanded rock specifically mudstone as an example, see Figure 2 , Figure 2 The water content time history curve of the mudstone sample is shown.

[0057] The linear expansion coefficient characterizes the degree of length expansion caused by a unit change in moisture content after water absorption. In practice, specialized linear expansion tests can be used to accurately measure the length change of a rock specimen in a specific direction (usually the axial direction) during saturation. This can then be calculated based on the rock's initial length and the corresponding change in moisture content.

[0058] Mechanical properties primarily include elastic modulus, tensile strength, and cohesion. In practice, uniaxial compression, Brazilian splitting, and triaxial compression tests are performed on expansive rock specimens with varying moisture contents to determine how these mechanical properties change with moisture content.

[0059] Specifically, the functional relationship data of elastic modulus and moisture content are obtained by conducting uniaxial compression tests; the functional relationship data of tensile strength and moisture content are obtained by conducting Brazilian splitting tests; and the functional relationship data of cohesion and moisture content are obtained by conducting triaxial compression tests.

[0060] The following formula was used to determine the cohesion of expansive rock samples with different water contents during the triaxial compression test:

[0061]

[0062] Where σ1 is the triaxial compressive strength, σ3 represents the confining pressure, and c is the cohesion of the expansive rock specimen; represents the internal friction angle of the expansive rock specimen and is assumed to be independent of the water content.

[0063] In the application, triaxial compression tests with the same confining pressure were carried out on multiple expansive rock samples with different water contents. At the same time, the cohesion was calculated using the above formula, so as to fit and determine the relationship function between cohesion and water content.

[0064] See also Figure 3 、 Figure 4 and Figure 5, taking the swelling rock sample, specifically the mudstone sample, as an example, Figure 3 、 Figure 4 and Figure 5 The fitting curves of the relationship between the elastic modulus, tensile strength and cohesion of mudstone samples and water content are shown in turn.

[0065] Step 102: Calibrate the mode I and mode II fracture energies of the expansive rock sample at different water contents to obtain fracture energy parameters.

[0066] Among them, mode I fracture energy represents the energy consumed by the rock to resist the expansion of opening cracks (tensile failure), while mode II fracture energy represents the energy consumed by the rock to resist the expansion of sliding cracks (shear failure).

[0067] In practice, calibration must be performed separately for expansive rock specimens at different moisture contents. Because rock fracture energy characteristics are significantly affected by moisture content, and the softening effect of water absorption alters the energy required for crack propagation, a single dry fracture energy value cannot be used. The specific calibration method can follow the standard process described in the invention patent "A Precise Fracture Energy Calibration Method to Eliminate Loading Rate Effects" (Patent No.: ZL202211201119.6).

[0068] For expansive rock specimens with different water contents, it is only necessary to recalibrate the mode I and mode II fracture energies. The joint penalty, normal contact stiffness, and tangential contact stiffness can be obtained using the following formula:

[0069]

[0070] Where, P f is the joint penalty value, E0 is the initial elastic modulus of the sample when it is not immersed in water, P n is the normal contact stiffness, P t is the tangential contact stiffness.

[0071] Step 103: The moisture content time history curve, linear expansion coefficient, functional relationship data, and fracture energy parameters are embedded into the FDEM program, and a numerical excavation model of the target tunnel is constructed.

[0072] In this application, after acquiring and calibrating the key parameters of the expansive rock specimens, these parameters must be systematically integrated into the coupled finite element and discrete element method (FDEM) computational framework. Specifically, the acquired water content time history curves, linear expansion coefficient, and data characterizing the functional relationships between elastic modulus, tensile strength, and cohesion as a function of water content, along with the calibrated Mode I and Mode II fracture energy parameters at different water contents, must be integrated into the FDEM tunnel excavation simulation program.

[0073] This embedding process enables the FDEM program to dynamically read and process these parameters. Specifically, the moisture content time history curve is converted into a time-varying input sequence to drive the simulation of the hydraulic process in the model; the linear expansion coefficient is directly introduced as a key constant for calculating expansion stress; the functional relationship between mechanical parameters (elastic modulus, tensile strength, cohesion) and moisture content is programmed as a real-time query or interpolation module to ensure that unit properties can be dynamically adjusted according to their current simulated moisture content; and the fracture energy parameter is assigned to the corresponding mesh units in the model according to their moisture content status.

[0074] After embedding is completed, the excavation numerical model of the target tunnel is constructed using the above FDEM. For example, the constructed excavation numerical model can be found in Figure 6 , Figure 6 Schematic diagram of the numerical model for excavation of expansive rock tunnel.

[0075] In application, a detailed three-dimensional or two-dimensional grid including the tunnel outline, initial geostress field, surrounding rock material partition (especially the expansive rock area) and preset water level can be established based on the geological and geometric conditions of the actual project. In the excavation numerical model, the grid is usually composed of triangular elements (representing the continuous rock mass) and quadrilateral elements connecting them (preset potential fracture surfaces). Model initialization requires accurate setting of the initial geostress state to reflect the in-situ stress environment before tunnel excavation. The simulation of the excavation process is achieved by dynamically removing the grid elements within the tunnel face according to the construction steps in the program.

[0076] Step 104: Perform hydraulic large deformation simulation based on the excavation numerical model.

[0077] During the simulation, the expansion force effect is applied to the triangular elements below the water level that are adjacent to the broken quadrilateral elements and in contact with water, while the degradation effects of cohesion and tensile strength are applied to the intact quadrilateral elements adjacent to the triangular elements.

[0078] During the simulation calculation process, the FDEM program dynamically triggers two key effects based on the preset physical mechanism. On the one hand, the expansion force effect is applied to the triangular elements that meet specific conditions in the area below the water level. Such triangular elements must meet three conditions at the same time: they are located within the groundwater infiltration range, adjacent to the broken quadrilateral elements (representing the actual cracks), and in direct contact with water. The calculation of the expansion force is essentially to determine the tensile stress generated by water absorption and expansion, and the value is determined by the current change in moisture content, the linear expansion coefficient and the bulk modulus of the material. The calculated expansion force acts on the triangular element in the form of a nodal force, and the equivalent distribution from continuous stress to field discrete nodal force is achieved through a preset conversion mechanism (such as coordinate mapping relationship).

[0079] In application, the calculation formula of the expansion force applied in the expansion force effect is:

[0080]

[0081] Where Δσ xx , Δσ yy are the normal expansion stresses in the x and y directions, Δσ xy , Δσ yx are the shear expansion stress in the x and y directions respectively, K is the bulk modulus, E is the elastic modulus, ν is the Poisson's ratio; β is the linear expansion coefficient, Δw t is the change in moisture content.

[0082] Further, see Figure 7 , Figure 7 The following is a schematic diagram of the conversion principle of expansion force to triangular element nodal force. In application, the expansion force can be converted to the nodal force of the triangular element using the following formula:

[0083]

[0084] Where, f xl 、f yl represents the nodal force of the triangle unit node l in the x and y directions, Δσ xx , Δσ yy It represents the expansion force in the x and y directions respectively, x m 、y m In turn, they represent the x and y coordinate values ​​of node m. n 、y n They represent the x and y coordinate values ​​of node n respectively; nodes l, m and n are three nodes arranged counterclockwise in the triangle unit.

[0085] On the other hand, the mechanical parameter degradation effect of intact quadrilateral elements adjacent to the aforementioned expansion force element is synchronously triggered. "Intact" here refers to quadrilateral elements that have not yet fractured, that is, quadrilateral elements that do not have the function of conducting water to adjacent triangular elements. These quadrilateral elements act as potential fracture surfaces, controlling the continuous-discontinuous transition behavior of the rock mass. The degradation effect manifests itself as a reduction in cohesion and tensile strength. The degree of reduction can be calculated in real time based on the functional relationship data obtained above, and is directly related to the change in water content experienced by the adjacent triangular elements.

[0086] It should be noted that there is a spatial transmission logic between the expansion force and the degradation effect: water penetrates into the adjacent triangular units through the broken cracks (i.e., the broken quadrilateral units), causing expansion. The expansion deformation further weakens the mechanical properties of the adjacent intact quadrilateral units, forming a chain mechanism of "quadrilateral unit rupture and water conduction - contacting triangular units expand - adjacent intact quadrilateral units deteriorate."

[0087] In one embodiment, applying the expansion force effect includes:

[0088] Calculate the corresponding total expansion force according to the current moisture content of the triangular element;

[0089] Determining the expansion force application ratio according to the current number of ruptured quadrilateral elements adjacent to the triangular element;

[0090] The total expansion force is applied to the triangular element according to the expansion force application ratio.

[0091] During the actual simulation process, when a quadrilateral unit ruptures, the adjacent triangular unit absorbs water and expands. The total expansion force of the triangular unit can be calculated based on its current moisture content (the calculation method of the expansion force can be found in the above content). Then, the application of the total expansion force is determined based on the rupture of the quadrilateral units adjacent to the triangular unit. Specifically, when only one quadrilateral unit ruptures, only 1 / 3 of the total expansion force is applied to the triangular unit. When another quadrilateral unit ruptures, 2 / 3 of the total expansion force is applied. Only when all three adjacent quadrilateral units rupture is the full total expansion force applied.

[0092] See also Figure 8 , Figure 8 Schematic diagram of the calculation principle for triangular element expansion forces and quadrilateral element parameter degradation. Physical rationality is ensured during the simulation through a unique distribution rule, where the expansion force is applied in stages based on the number of adjacent fractured quadrilateral elements. A single fractured quadrilateral element causes one-third of the total expansion force on adjacent triangular elements, with the remaining two-thirds shared by the triangle element's two associated quadrilateral elements.

[0093] In one embodiment, the degradation effects of cohesion and tensile strength are applied, including:

[0094] According to the current moisture content of the triangular element, the corresponding cohesion degradation and tensile strength degradation are determined;

[0095] A preset ratio of cohesion degradation and tensile strength degradation is applied to the complete quadrilateral elements adjacent to the triangular elements.

[0096] See also Figure 8In the actual simulation process, when a triangular unit absorbs water and expands to produce an expansion force effect, if there is a complete quadrilateral unit among the quadrilateral units adjacent to the triangular unit, a degradation effect is applied to the complete quadrilateral unit. When applying the degradation effect, the corresponding degradation amount can be applied to the complete quadrilateral unit according to a preset ratio (such as 1 / 2). That is, the total cohesion degradation amount and tensile strength degradation amount are calculated according to the current moisture content of the triangular unit, and then the corresponding cohesion degradation amount and tensile strength degradation amount are applied to the adjacent complete quadrilateral units according to the preset ratio, for example, 1 / 2 of the cohesion degradation amount and 1 / 2 of the tensile strength degradation amount are applied.

[0097] Among them, the cohesion degradation amount can be calculated based on the functional relationship between cohesion and moisture content (such as Figure 5 The tensile strength degradation can be determined based on the functional relationship between tensile strength and moisture content (as shown in Figure 4 as shown) to confirm.

[0098] If an expansion force is also applied to a triangular element adjacent to the intact quadrilateral, a preset proportion of the degradation is also applied; in other words, the final degradation of the intact quadrilateral is the sum of the effects of the triangular elements on both sides. This distribution method reflects the multi-source degradation effect transmission mechanism of the fracture surface medium and can accurately quantify the impact of different moisture paths on the attenuation of mechanical parameters.

[0099] See also Figure 9 , Figure 9 This is a schematic diagram of the simulation results of large hydraulic deformation of tunnel expansion rock. Figure 9 As shown in the figure, the simulation results can clearly show the disaster of large hydraulic deformation of tunnel expansion rock under the action of groundwater infiltration, providing data support for the subsequent prevention and control of large hydraulic deformation disasters.

[0100] In one embodiment, the expansion force effect and the degradation effect are both applied while ignoring the time delay of the water infiltration process.

[0101] In the application, in order to simplify the computational complexity, the temporal nature of the water infiltration process is ignored during the simulation. It is assumed that the expansion force effect and the parameter degradation effect are instantaneous and are applied to the triangular elements on both sides of the quadrilateral element at the moment of its rupture.

[0102] Corresponding to the aforementioned embodiment of the method for realizing the application function, the present invention also provides a FDEM simulation system for hydraulic large deformation of expansive rock in a tunnel and corresponding embodiments.

[0103] See Figure 10 , Figure 10 Schematic diagram of the module structure of the FDEM simulation system for large hydraulic deformation of expansive rock in tunnels.

[0104] The FDEM simulation system for large hydraulic deformation of tunnel expansion rock includes:

[0105] The data acquisition unit 11 is used to obtain the water content time history curve, linear expansion coefficient, and functional relationship data of the mechanical performance parameters changing with the water content of the expansive rock sample in the target tunnel.

[0106] The fracture energy calibration unit 12 is used to calibrate the type I and type II fracture energies of the expansive rock sample at different water contents to obtain fracture energy parameters.

[0107] The embedding and construction unit 13 is used to embed the moisture content time history curve, linear expansion coefficient, functional relationship data and fracture energy parameters into the FDEM program and construct an excavation numerical model of the target tunnel.

[0108] The simulation unit 14 is used to perform hydraulic large deformation simulation based on the excavation numerical model. During the simulation, an expansion force effect is applied to the triangular units below the water level that are adjacent to the broken quadrilateral units and in contact with water, and at the same time, a degradation effect of cohesion and tensile strength is applied to the intact quadrilateral units adjacent to the triangular units.

[0109] In one embodiment, the simulation unit 14 is further configured to:

[0110] The nodal forces of the triangular element are determined by the following formula:

[0111]

[0112] Where, f xl 、f yl represents the nodal force of the triangle unit node l in the x and y directions, Δσ xx , Δσ yy It represents the expansion force in the x and y directions respectively, x m 、y m In turn, they represent the x and y coordinate values ​​of node m. n 、y n They represent the x and y coordinate values ​​of node n respectively; nodes l, m and n are three nodes arranged counterclockwise in the triangle unit.

[0113] Regarding the system in the above embodiment, the specific manner in which each unit module performs operations has been described in detail in the embodiment of the method, and will not be elaborated again here.

[0114] While various embodiments of the present invention have been described above, the above descriptions are intended to be illustrative, non-exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or improvements to existing technologies, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A FDEM simulation method for large hydraulic deformation of tunnel expansion rock, characterized by: include: Obtain the water content time history curve, linear expansion coefficient, and the functional relationship data of mechanical properties parameters with water content of the expansive rock sample in the target tunnel; Calibrate the mode I and mode II fracture energies of the expansive rock sample at different water contents to obtain fracture energy parameters; embedding the moisture content time history curve, linear expansion coefficient, functional relationship data and fracture energy parameters into an FDEM program, and constructing a numerical model of the excavation of the target tunnel; A hydraulic large deformation simulation is performed based on the excavation numerical model. During the simulation, an expansion force effect is applied to the triangular units below the water level that are adjacent to the broken quadrilateral units and in contact with water, and a degradation effect of cohesion and tensile strength is applied to the intact quadrilateral units adjacent to the triangular units.

2. The FDEM simulation method for large hydraulic deformation of tunnel expansion rock according to claim 1 is characterized in that: The moisture content time history curve is obtained by carrying out drying and water immersion tests on cylindrical expansive rock samples.

3. The FDEM simulation method for hydraulic large deformation of tunnel expansion rock according to claim 1 is characterized in that: The mechanical performance parameters include elastic modulus, tensile strength and cohesion; the functional relationship data of the elastic modulus changing with moisture content is obtained by conducting a uniaxial compression test; the functional relationship data of the tensile strength changing with moisture content is obtained by conducting a Brazilian splitting test; the functional relationship data of the cohesion changing with moisture content is obtained by conducting a triaxial compression test.

4. The FDEM simulation method for large hydraulic deformation of tunnel expansion rock according to claim 3 is characterized in that: When determining the cohesion of expansive rock samples with different water contents in the triaxial compression test, the following formula is used: Where σ1 is the triaxial compressive strength, σ3 represents the confining pressure, and c is the cohesion of the expansive rock specimen; represents the internal friction angle of the expansive rock specimen and is assumed to be independent of the water content.

5. The FDEM simulation method for large hydraulic deformation of tunnel expansion rock according to claim 1 is characterized in that: The calculation formula of the expansion force applied in the expansion force effect is: Where Δσ xx , Δσ yy are the normal expansion stresses in the x and y directions, Δσ xy , Δσ yx are the shear expansion stress in the x and y directions respectively, K is the bulk modulus, E is the elastic modulus, ν is the Poisson's ratio; β is the linear expansion coefficient, Δw t is the change in moisture content.

6. The FDEM simulation method for large hydraulic deformation of tunnel expansion rock according to claim 5 is characterized in that: The method further comprises: The nodal forces of the triangular element are determined by the following formula: Where, f xl 、f yl represents the nodal force of the triangle unit node l in the x and y directions, Δσ xx , Δσ yy It represents the expansion force in the x and y directions respectively, x m 、y m In turn, x represents the x and y coordinate values ​​of node m. n 、y n They represent the x and y coordinate values ​​of node n respectively; nodes l, m and n are three nodes arranged counterclockwise in the triangle unit.

7. The FDEM simulation method for large hydraulic deformation of tunnel expansion rock according to claim 1 is characterized in that: The applying of the expansion force effect comprises: Calculating a corresponding total expansion force value according to the current moisture content of the triangular unit; determining an expansion force application ratio according to a current number of ruptured quadrilateral units adjacent to the triangular unit; The total value of the expansion force is applied to the triangular unit according to the expansion force application ratio.

8. The FDEM simulation method for large hydraulic deformation of tunnel expansion rock according to claim 1 is characterized in that: The deterioration effect of the applied cohesion and tensile strength includes: Determining the corresponding cohesion degradation amount and tensile strength degradation amount according to the current moisture content of the triangular unit; The cohesion degradation amount and the tensile strength degradation amount in a preset ratio are applied to the complete quadrilateral unit adjacent to the triangular unit.

9. The FDEM simulation method for hydraulic large deformation of tunnel expansion rock according to claim 1 is characterized in that: The application of the expansion force effect and the degradation effect both ignores the time delay of the water infiltration process.

10. A FDEM simulation system for large hydraulic deformation of tunnel expansion rock, characterized by: include: A data acquisition unit is used to obtain the water content time history curve, linear expansion coefficient, and functional relationship data of mechanical performance parameters changing with water content of the expansive rock sample in the target tunnel; a fracture energy calibration unit, used to calibrate the mode I and mode II fracture energies of the expansive rock sample at different water contents to obtain fracture energy parameters; An embedding and construction unit, for embedding the moisture content time history curve, linear expansion coefficient, functional relationship data and fracture energy parameters into an FDEM program, and constructing an excavation numerical model of the target tunnel; A simulation unit is used to perform hydraulic large deformation simulation based on the excavation numerical model; during the simulation process, an expansion force effect is applied to the triangular units below the water level that are adjacent to the broken quadrilateral units and in contact with water, and at the same time, a degradation effect of cohesion and tensile strength is applied to the intact quadrilateral units adjacent to the triangular units.

Images