Grouting curtain parameter design method for structure protection under blasting vibration effect

Abstract

The invention provides a grouting curtain parameter design method for structure protection under the blasting vibration effect, and relates to the technical field of underground engineering and blasting engineering, and the grouting curtain parameter design method comprises the following steps: S1, determining main factors influencing the vibration velocity of a protection structure, and constructing a vibration velocity prediction model containing an undetermined coefficient by adopting a dimension analysis white golden-han theorem; s2, establishing a finite element blasting numerical model, and obtaining structural vibration velocity data under different parameter combinations; s3, fitting the structural vibration velocity data by using the vibration velocity prediction model, and determining an undetermined coefficient in the vibration velocity prediction model; and S4, a relational expression between the structural vibration velocity and stress is established, and grouting curtain design parameters meeting structural safety requirements are determined in combination with engineering conditions. By means of the method, the problem that the grouting curtain damping effect and grouting curtain parameters are difficult to determine in actual engineering is solved, the blasting vibration peak value of the protection structure under the blasting vibration effect is effectively reduced, and a guarantee is provided for underground and ground structure protection and blasting engineering safety construction.

Description

Technical Field

[0001] The invention relates to the technical field of underground engineering and blasting engineering, and in particular to a grouting curtain parameter design method for protecting a structure under blasting vibration. Background Art

[0002] As an efficient and economical rock excavation method, drilling and blasting has been widely used in underground engineering construction. However, unlike mountain tunnel construction, urban underground engineering faces more complex geological conditions and environmental constraints. Urban ground buildings are densely populated, including various civil buildings, transportation facilities and municipal facilities; important infrastructure such as water supply and drainage networks, gas pipelines, power pipelines and subway tunnels are distributed in the underground space, and these structures are more sensitive to blasting vibrations.

[0003] At present, the blasting vibration control technologies used in engineering practice can be mainly divided into three categories: First, reinforcement measures are taken for the protected objects, such as structural reinforcement, wrapping protection, etc., but such methods are often limited by the constructability of existing structures and are relatively costly; second, control of blasting source parameters, including optimization of blasting parameters, use of delayed blasting, control of charge amount, etc., but excessive control of blasting parameters may affect construction efficiency; third, shock reduction measures are taken on the propagation path of blasting seismic waves, mainly including digging shock reduction trenches, setting shock reduction belts, and laying grouting curtains, etc. Among them, grouting curtains have become one of the most commonly used vibration reduction measures due to their advantages such as convenient construction, strong adaptability, and little interference with existing structures.

[0004] However, the existing grouting curtain vibration reduction technology still has the following technical defects:

[0005] The shock absorption effect of grouting curtain is difficult to accurately evaluate. Existing studies are mostly based on empirical formulas or simplified models, which fail to fully consider the coupling effects of multiple factors such as site conditions, explosion source characteristics and curtain parameters, resulting in insufficient prediction accuracy of the shock absorption effect.

[0006] There is a lack of systematic determination method for the design parameters of grouting curtains. At present, the geometric dimensions (height, length, width) and position parameters of curtains in projects are mostly determined based on experience, lacking theoretical basis and quantitative design methods.

[0007] There is a lack of clear correlation mechanism between structural safety control indicators and grouting curtain parameters. The existing design fails to establish a quantitative relationship between the safety threshold of the protective structure and the curtain design parameters, making it difficult to achieve parameter optimization based on safety performance.

[0008] Therefore, how to establish a scientific and reasonable grouting curtain parameter design method to achieve effective protection of the structure under blasting vibration is a key technical problem that needs to be solved urgently. Summary of the invention

[0009] In view of this, the present invention proposes a grouting curtain parameter design method for structural protection under blasting vibration. By establishing a vibration velocity prediction model based on dimensional analysis, conducting numerical simulation verification, and constructing a vibration velocity-stress relationship, an accurate evaluation of the shock absorption effect of the grouting curtain is achieved, a systematic curtain parameter design method is provided, and a quantitative relationship between structural safety control indicators and curtain parameters is established, thereby providing reliable technical support and theoretical guidance for the safety protection of structures under blasting vibration.

[0010] The technical solution of the present invention is implemented as follows: The present invention provides a grouting curtain parameter design method for structural protection under blasting vibration, comprising:

[0011] S1. Determine the main factors affecting the vibration velocity of the protected structure and use the dimensional analysis Buckingham theorem to construct a vibration velocity prediction model including unknown coefficients;

[0012] S2. Establish a finite element blasting numerical model to obtain structural vibration velocity data under different parameter combinations;

[0013] S3. Fitting the structural vibration velocity data using the vibration velocity prediction model to determine the undetermined coefficients in the vibration velocity prediction model;

[0014] S4. Establish a relationship between structural vibration velocity and stress, determine a safety stress threshold based on design specifications, determine a structural vibration velocity safety threshold through the relationship, substitute the structural vibration velocity safety threshold into the vibration velocity prediction model of step S3, and determine the grouting curtain design parameters that meet the structural safety requirements in combination with engineering conditions.

[0015] On the basis of the above technical solution, preferably, the grouting curtain is buried between the protection structure and the blasting source, that is, on the propagation path of the blasting stress wave, to interfere with the propagation of the blasting stress wave.

[0016] On the basis of the above technical solution, preferably, the main factors affecting the vibration velocity of the protection structure include:

[0017] Site parameters, including rock and soil density, rock and soil longitudinal wave velocity, rock and soil transverse wave velocity, soil moisture content and the distance between the protective structure and the explosion source;

[0018] Explosive source parameters, including explosive quantity, charge diameter, blast hole diameter, explosive detonation velocity and explosive density;

[0019] The grouting curtain parameters include the grouting curtain height, grouting curtain length, grouting curtain width and the horizontal distance between the grouting curtain and the protective structure.

[0020] On the basis of the above technical solution, preferably, the specific steps of using the dimensional analysis Buckingham theorem to construct a vibration velocity prediction model including undetermined coefficients in step S1 include:

[0021] Select three factors from the main factors as dimensionally independent factors, and the remaining factors as dimensionally dependent factors, where any dimensionally independent factor cannot be calculated from the other two dimensionally independent factors using basic data;

[0022] Convert dimensionally dependent factors into dimensionless numbers through the π theorem;

[0023] According to the dimensionless homogeneity theorem and combined with dimensionless numbers, a vibration velocity prediction model including unknown coefficients is constructed.

[0024] On the basis of the above technical solution, preferably, the dimensionally independent factors are the amount of explosives, the distance between the protective structure and the explosion source, and the longitudinal wave velocity of the rock and soil mass. The mathematical expression of the vibration velocity prediction model including the undetermined coefficients is as follows:

[0025]

[0026] Where V P is the vibration velocity of the protected structure; η is the shock absorption efficiency; K, α 1 , α 2 , α 3 , α 4 , α 5 is the unknown coefficient, among which, c is the longitudinal wave velocity of the rock and soil mass, ρ is the density of the rock and soil mass; R 1 is the distance between the protection structure and the explosion source; R 2 is the horizontal distance between the grouting curtain and the protective structure; H is the height of the grouting curtain; L is the length of the grouting curtain; W is the width of the grouting curtain; Q is the amount of explosives.

[0027] Based on the above technical solution, preferably, step S2 includes:

[0028] S21. Use ANSYS / LS-DYNA software to establish a three-dimensional finite element model, and set the model size according to the actual range of action of the explosive and the size of the blast hole;

[0029] S22, the model is divided using Lagrangian grids, where the protection structure and its surrounding areas are meshed;

[0030] S23, setting boundary conditions, including: using non-reflection boundary conditions around the model and at the bottom, and using free boundary conditions at the top;

[0031] S24, using the surface-to-surface contact algorithm to describe the soil-structure interaction and setting the corresponding friction coefficient;

[0032] S25, select the material constitutive model, where: the soil adopts the Drucker-Prager constitutive model, the grouting curtain adopts the CONCRETE_DAMAGE_REL3 material model, and input the corresponding physical and mechanical parameters;

[0033] S26. Setting working conditions with different parameter combinations by one of the following two methods: single factor impact analysis method, changing only one main factor at a time; or multi-factor orthogonal analysis method, changing multiple main factors at the same time;

[0034] S27. According to the working condition of each parameter combination, simulation calculation is performed in a three-dimensional finite element model, and the reliability of the calculation results is verified to obtain numerical simulation results under the working conditions of different parameter combinations;

[0035] S28. According to the numerical simulation results under the working conditions of different parameter combinations, the structural vibration velocity data under the working conditions of different parameter combinations are statistically obtained.

[0036] Based on the above technical solution, preferably, in step S27, verifying the reliability of the calculation result includes:

[0037] The soil pressure, acceleration or vibration velocity results of the same point in the numerical simulation and the indoor model test are read through the post-processing software lsprepost. If the waveforms of the two are close, the peak values ​​are not much different, and the errors of each point are within 15%, the numerical simulation results are judged to be reliable.

[0038] On the basis of the above technical solution, preferably, step S4 includes:

[0039] S41. According to wave theory, the functional relationship between structural vibration velocity and stress is derived as follows:

[0040] σ=f(V p )

[0041] Where, σ is the effective stress of the protection structure; V p To protect the structural vibration speed;

[0042] S42. Determine the safety stress threshold based on the design specification:

[0043] [σ] = k·σ 0

[0044] Where [σ] is the safety stress threshold, k is the safety factor, and σ 0 The maximum allowable stress specified in the design specifications;

[0045] S43. The structural vibration speed safety threshold is obtained by inversely deducing the functional relationship between the structural vibration speed and the stress:

[0046] [V p ] = f-1 ([σ])

[0047] In the formula, [V p ] is the structural vibration speed safety threshold, f -1 It is the inverse function of the relationship between structural vibration velocity and stress;

[0048] S44, the structural vibration speed safety threshold [V p ] is substituted into the vibration velocity prediction model of step S3, and the design parameters of the grouting curtain that meet the structural safety requirements are determined in combination with the engineering conditions.

[0049] On the basis of the above technical solution, preferably, the grouting curtain is composed of cement mortar, rubber powder, iron powder and river sand.

[0050] On the basis of the above technical solution, preferably, the protection structure includes:

[0051] Ground structures, including buildings, overhead and high-voltage towers;

[0052] Underground structures include underground pipelines, underground box culverts and underground tunnels.

[0053] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0054] (1) The present invention systematically solves the technical problems of difficulty in determining the shock absorption effect and parameters of grouting curtains in actual engineering through dimensional analysis, numerical simulation, model verification and parameter optimization, and provides reliable technical support for blasting vibration protection of underground and ground structures, which has important engineering application value;

[0055] (2) The present invention adopts the Buckingham theorem of dimensional analysis to construct a vibration velocity attenuation prediction model, comprehensively considers multiple influencing factors such as the amount of explosives, the distance from the blast source, and the geometric parameters of the grouting curtain, and establishes a quantitative relationship between the parameters, thereby overcoming the defect of insufficient precision of the traditional empirical formula and improving the accuracy of vibration prediction;

[0056] (3) The present invention establishes a numerical simulation method based on ANSYS / LS-DYNA, verifies the reliability of the model by comparing it with the indoor model test results, and realizes efficient prediction of the structural vibration response under different working conditions, avoiding a large number of physical tests and significantly reducing the research cost;

[0057] (4) The present invention establishes a functional relationship between structural vibration velocity and stress, and combines the safety control indicators in the design specifications to achieve a scientific determination of the vibration velocity safety threshold, providing a theoretical basis for the optimal design of grouting curtain parameters and ensuring the reliability of the protection scheme;

[0058] (5) The parameter design method proposed in the present invention has strong practicality and versatility. It can flexibly select the geometric parameters of the grouting curtain according to the actual conditions of the project, meet the vibration reduction requirements in different engineering scenarios, and has good engineering adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0060] Figure 1 is a flow chart of a method according to an embodiment of the present invention;

[0061] Figure 2 A numerical model diagram of an embodiment of the present invention;

[0062] Figure 3 A comparison diagram of acceleration time history curves of numerical simulation and indoor model experiment of an embodiment of the present invention;

[0063] Figure 4 It is a schematic diagram of structural vibration velocity and stress fitting in an embodiment of the present invention. DETAILED DESCRIPTION

[0064] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0065] like Figure 1 As shown, the present invention provides a grouting curtain parameter design method for structural protection under blasting vibration, comprising:

[0066] S1. Determine the main factors affecting the vibration velocity of the protected structure and use the dimensional analysis Buckingham theorem to construct a vibration velocity prediction model including unknown coefficients;

[0067] S2. Establish a finite element blasting numerical model to obtain structural vibration velocity data under different parameter combinations;

[0068] S3. Fitting the structural vibration velocity data using the vibration velocity prediction model to determine the undetermined coefficients in the vibration velocity prediction model;

[0069] S4. Establish a relationship between structural vibration velocity and stress, determine a safety stress threshold based on design specifications, determine a structural vibration velocity safety threshold through the relationship, substitute the structural vibration velocity safety threshold into the vibration velocity prediction model of step S3, and determine the grouting curtain design parameters that meet the structural safety requirements in combination with engineering conditions.

[0070] Specifically, in one embodiment of the present invention, the protective structure can be divided into ground structure and underground structure by location, wherein the ground structure is mainly buildings, elevated, high-voltage towers, etc., and the underground structure is mainly underground pipelines, underground culverts, underground tunnels, etc. The grouting curtain is mainly composed of cement mortar, rubber powder, iron powder and river sand in a certain ratio, which has certain energy absorption and shock absorption effects.

[0071] Specifically, in one embodiment of the present invention, the main factors affecting the vibration velocity of the structure under the protection of the grouting curtain mainly include three parts: site parameters, explosion source parameters and grouting curtain parameters. Among them, the site factors mainly include but are not limited to the density of the rock and soil mass, the longitudinal wave velocity of the rock and soil mass, the transverse wave velocity of the rock and soil mass, the moisture content of the soil mass, the distance between the protection structure and the explosion source, etc. The explosion source parameters mainly include but are not limited to the amount of explosives, the diameter of the charge, the diameter of the blasthole, the explosion velocity of the explosives, the density of the explosives, etc.

[0072] In this embodiment, the grouting curtain is mainly buried between the protective structure and the explosion source, that is, on the propagation path of the blasting stress wave, to interfere with the propagation of the blasting stress wave. Therefore, the grouting curtain parameters mainly include but are not limited to the grouting curtain height, grouting curtain length, grouting curtain width and the horizontal distance between the grouting curtain and the pipeline.

[0073] Specifically, in one embodiment of the present invention, the specific steps of using the dimensional analysis Buckingham theorem in step S1 to construct a vibration velocity prediction model including undetermined coefficients include:

[0074] Select three factors from the main factors as dimensionally independent factors, and the remaining factors as dimensionally dependent factors, where any dimensionally independent factor cannot be calculated from the other two dimensionally independent factors using basic data;

[0075] Convert dimensionally dependent factors into dimensionless numbers through the π theorem;

[0076] According to the dimensionless homogeneity theorem and combined with dimensionless numbers, a vibration velocity prediction model including unknown coefficients is constructed.

[0077] The dimensionally independent factors are the amount of explosives, the distance between the protective structure and the explosion source, and the longitudinal wave velocity of the rock and soil. The mathematical expression of the vibration velocity prediction model including the undetermined coefficients is as follows:

[0078]

[0079] Where V Pis the vibration velocity of the protected structure; η is the shock absorption efficiency; K, α 1 , α 2 , α 3 , α 4 , α 5 is the unknown coefficient, among which, c is the longitudinal wave velocity of the rock and soil, that is, the propagation velocity of the longitudinal wave in the medium, ρ is the density of the rock and soil; R 1 is the distance between the protection structure and the explosion source; R 2 is the horizontal distance between the grouting curtain and the protective structure; H is the height of the grouting curtain; L is the length of the grouting curtain; W is the width of the grouting curtain; Q is the amount of explosives.

[0080] In a specific example, the protection structure is used as a pipeline for illustration:

[0081] The peak vibration velocity of the pipeline under the influence of blasting vibration is affected by many factors. In this embodiment, the physical quantities shown in Table 1 are mainly selected for analysis.

[0082] Table 1 Influencing factors and dimensions

[0083] Equation parameters unit dimension <![CDATA[Peak particle velocity V of the pipeline P > <![CDATA[cm·s -1 ]]> <![CDATA[LT -1 ]]> Explosive source quantity Q kg M <![CDATA[Explosion source distance R 1 > m L <![CDATA[Horizontal distance R between the grouting curtain and the pipeline 2 > m L Grouting curtain height H cm L Grouting curtain length L cm L Grouting curtain width W cm L Geotechnical pipe density ρ <![CDATA[g·cm -3 ]]> <![CDATA[ML -3 ]]> The propagation speed of longitudinal waves in the medium is c <![CDATA[m·s -1 ]]> <![CDATA[LT -1 ]]>

[0084] Assume that the vibration velocity V of the pipeline particle is P According to the following physical expression (1):

[0085] V p ·η=F(Q,R 1 ,R 2 ,H,L,W,ρ,c) (1)

[0086] The physical meaning and dimension of each parameter in the formula are shown in Table 1.

[0087] According to the dimensional homogeneity theorem, select Q, R 1 , c are dimensionally independent quantities, and other parameters are dimensionally dependent quantities. The dimensionless number can be obtained as shown in the following formula (2):

[0088]

[0089] Since the product and power of different dimensionless numbers are still dimensionless numbers, based on the above dimensionless numbers, a new dimensionless number can be constructed as follows (3):

[0090]

[0091] According to the π theorem, we can assume that the dimensionless number above satisfies the following relationship (4):

[0092] π=F(π 1 ,π 2 ,π3 ,π 4 ,π 6 ) (4)

[0093] Substituting the meaning of each π value into formula (4), we get formula (5):

[0094]

[0095] Since V P The explosive quantity Q and protection distance R 2 There is a positive correlation between the height H, length L, width W, and explosion source distance R of the grouting curtain. 1 There is a negative correlation. Therefore, it can be assumed that the above parameters satisfy the following formula (6):

[0096]

[0097] For a certain site, c and ρ in the above formula are fixed, so the above formula can be rewritten as formula (7):

[0098]

[0099] So far, formula (7) is the constructed vibration velocity prediction model containing unknown coefficients, where K, α 1 , α 2 , α 3 , α 4 , α 5 are all undetermined coefficients, and

[0100] Specifically, in one embodiment of the present invention, step S2 includes:

[0101] S21. Use ANSYS / LS-DYNA software to establish a three-dimensional finite element model, and set the model size according to the actual range of action of the explosive and the size of the blast hole;

[0102] S22, the model is divided using Lagrangian grids, where the protection structure and its surrounding areas are meshed;

[0103] S23, setting boundary conditions, including: using non-reflection boundary conditions around the model and at the bottom, and using free boundary conditions at the top;

[0104] S24, using the surface-to-surface contact algorithm to describe the soil-structure interaction and setting the corresponding friction coefficient;

[0105] S25, select the material constitutive model, where: the soil adopts the Drucker-Prager constitutive model, the grouting curtain adopts the CONCRETE_DAMAGE_REL3 material model, and input the corresponding physical and mechanical parameters;

[0106] S26. Setting working conditions with different parameter combinations by one of the following two methods: single factor impact analysis method, changing only one main factor at a time; or multi-factor orthogonal analysis method, changing multiple main factors at the same time;

[0107] S27. According to the working condition of each parameter combination, simulation calculation is performed in a three-dimensional finite element model, and the reliability of the calculation results is verified to obtain numerical simulation results under the working conditions of different parameter combinations;

[0108] S28. According to the numerical simulation results under the working conditions of different parameter combinations, the structural vibration velocity data under the working conditions of different parameter combinations are statistically obtained.

[0109] In one embodiment of the present invention, since the blasting vibration problem involves a complex dynamic process, it is difficult to ensure the reliability of the calculation results by relying solely on numerical simulation, and a large number of physical tests have problems such as high cost and long cycle. Therefore, the method of combining indoor model test with numerical simulation can ensure the accuracy of simulation results while controlling research costs. In specific implementation, an indoor model test is first carried out, using a 2m×0.5m×0.5m test box, in which a buried pipeline (length 0.5m, outer diameter 9cm, wall thickness 0.2cm) is laid, a blast hole (diameter 1.2cm, depth 0.275m) is set, and a blasting test is carried out. At the same time, a three-dimensional finite element model with the same size and parameters is established using ANSYS / LS-DYNA software, and the soil pressure, acceleration and vibration velocity data of the same point of the numerical simulation and the indoor model test are read by the post-processing software lsprepost. When the waveforms of the two are relatively close and the peak error is controlled within 15%, it can be determined that the numerical simulation results are reliable, and can be used for subsequent parameter analysis and optimization design. This method not only ensures the scientific nature of the research results, but also improves the research efficiency.

[0110] In this embodiment, specifically, the model building method is:

[0111] The blasting conditions and rock mass physical and mechanical parameters of the model are consistent with the indoor model test plan. The model width should be no less than 30 times the blasthole diameter, and the model depth should be greater than or equal to 1 times the blasthole depth. The specific size should be appropriately adjusted in combination with the actual action range of the explosive. According to the indoor model test design plan, the overall size of the numerical model is determined to be 2×0.5×0.5m, see Figure 2. The fill thickness is 0.5m, the buried pipeline is 0.5m long, the outer diameter is 9cm, the wall thickness is 0.2cm, the blasthole diameter is 1.2cm, the charge is 5cm long, the hole depth is 0.275m, and the cm-g-μs unit system is adopted. The pipeline, blasting mud, and soil layer in the numerical model are divided by Lagrangian grid, and the pipeline and the soil layer in contact with the pipeline are encrypted. The overall grid size of the model is set to 1~2cm, and the pipeline and surrounding grids are 0.5~1cm. The explosive and mud blocking grids are 0.5~2cm.

[0112] Non-reflecting boundary conditions are set around the model and at the bottom, and the top is a free boundary condition. Surface-to-surface contact is used to describe the interaction between pipe and soil. This method is usually used to describe objects of any shape with a large contact area. It is very effective when dealing with a large amount of relative sliding between objects. At the same time, the automatic contact algorithm can determine the contact surface direction of the shell unit by calculation. The contact part between the pipe and the soil is set to automatic surface-to-surface contact, and the static friction coefficient between the pipe and the soil is set to 0.12.

[0113] The material model for silty clay is *MAT_DRUCKER_PRAGER model, with a density of 1.92 g / cm 3 , elastic modulus is 0.039GPa, tensile strength is 0.028MPa, Poisson's ratio is 0.35, cohesion is 0.025MPa, and internal friction angle is 15°. The buried pipeline adopts the *MAT_PLASTIC_KINEMATIC material model with a density of 1.34g / cm 3 , elastic modulus is 2.92GPa, tensile strength is 48MPa, and Poisson's ratio is 0.38. Due to its strength and yield characteristics, the grouting curtain material can use the *MAT_CONCRETE_DAMAGE_REL3 material model with a density of 1.18g / cm 3 , the elastic modulus is 0.042 GPa, the compressive strength is 4.32 MPa, the Poisson's ratio is 0.26, the cohesion is 1.07 kPa, the internal friction angle is 52.3°, and *EOS_TABULATED_COMPATION is used to describe the stress-strain behavior.

[0114] Before model simulation, the parameter combination is set according to the parameters in the main factors. It can be set according to the single factor impact analysis method or the multi-factor orthogonal analysis method. The single factor impact analysis method only changes one parameter at a time, and the other parameters remain unchanged; the multi-factor orthogonal analysis method changes multiple parameters at the same time, and the parameter combination is determined through orthogonal experimental design.

[0115] According to the set parameter combination, one parameter combination is a working condition. In the finite element software, the model is set according to the current parameter combination, and then the blasting test is simulated to calculate the numerical simulation results under different working conditions. The numerical simulation results include soil pressure data, acceleration data, and vibration velocity data.

[0116] The reliability verification of the model results is as follows: the soil pressure, acceleration or vibration velocity results of the same point of the numerical simulation and the indoor model test are read through the post-processing software lsprepost. If the waveforms of the two are similar, see Figure 3 , and the peak values ​​are not much different, and the errors of each point are within 15%. It can be judged that the results of numerical simulation are consistent with reality and are reliable.

[0117] Record the structural vibration velocity data under different working conditions, count the simulation results under each parameter combination, and establish a data table to record the structural vibration velocity data results corresponding to each group of parameters.

[0118] Specifically, in one embodiment of the present invention, the core of step S3 is to use the vibration velocity prediction model derived by dimensional analysis in S1 to fit the structural vibration velocity numerical simulation results under different parameter combinations obtained in S2, so as to determine the undetermined coefficients in the prediction model. This step matches the theoretical model with the numerical simulation results through a mathematical regression method to establish a reliable prediction model. This method ensures that the model has a theoretical basis and has good engineering applicability. The reliability of the fitting result is measured by the correlation index R 2 To evaluate, request R 2 Not less than 0.85 to ensure that the fitting results have good reliability and rationality.

[0119] In this embodiment, the structural vibration velocity data under different parameter combination conditions in step S2 are collected, the data are sorted according to the dimensionless parameter form in the prediction model, and a data table is established to record the vibration velocity results corresponding to each group of parameters. The recorded data are uniformly preprocessed to calculate the value of each dimensionless parameter.

[0120] Substitute the dimensionless parameter values ​​into the mathematical expression of the vibration velocity prediction model of formula (7), logarithmize the model, transform it into a linear equation, and use the least squares method to perform multivariate linear regression to solve the unknown coefficient α 1 , α 2 , α 3 , α 4 , α 5 , calculate the coefficient K value. Calculate the coefficient of determination R 2 , verify R 2 Is it ≥0.85? If it does not meet the requirements, the data needs to be adjusted or refitted.

[0121] After the fitting is completed, the final values ​​of all unknown coefficients are recorded and a complete prediction model expression is given.

[0122] In this embodiment, after fitting according to the specific structural vibration velocity data, the pipeline peak vibration velocity prediction formula considering the grouting curtain parameters, namely, height, length, thickness, relative distance between the explosion source and the pipeline, amount of explosives at the explosion source, and horizontal distance between the grouting curtain and the pipeline is obtained as shown in formula (8):

[0123]

[0124] That is, in this embodiment, according to the specific data table, the α obtained by fitting 1 =0.179,α 2 =-0.215, α 3 =-0.017, α 4 =-0.561, α 5 =1.104, then according to the formula The calculated K value is 9.65.

[0125] Specifically, in one embodiment of the present invention, step S4 includes:

[0126] S41. According to wave theory, the functional relationship between structural vibration velocity and stress is derived as follows:

[0127] σ=f(V p )

[0128] Where, σ is the effective stress of the protection structure; V p To protect the structural vibration speed;

[0129] S42. Determine the safety stress threshold based on the design specification:

[0130] [σ] = k·σ 0

[0131] Where [σ] is the safety stress threshold, k is the safety factor, and σ 0 The maximum allowable stress specified in the design specifications;

[0132] S43. The structural vibration speed safety threshold is obtained by inversely deducing the functional relationship between the structural vibration speed and the stress:

[0133] [V p ] = f -1 ([σ])

[0134] In the formula, [V p ] is the structural vibration speed safety threshold, f -1 It is the inverse function of the relationship between structural vibration velocity and stress;

[0135] S44, the structural vibration speed safety threshold [Vp ] is substituted into the vibration velocity prediction model of step S3, and the design parameters of the grouting curtain that meet the structural safety requirements are determined in combination with the engineering conditions.

[0136] Among them, the design specifications are mainly national standards or industry standards and other documents that have practical engineering guidance and industry recognition. The safety control indicators are mainly the vibration velocity of the protection structure, or other indicators that have a functional relationship with the vibration velocity and can be converted into each other, such as frequency, stress, etc.

[0137] Specifically, step S4 is to establish a correlation between the structural safety control requirements and the grouting curtain parameter design. Under the action of blasting vibration, the safety performance of the structure is usually judged based on the strain or stress size, rather than directly using the vibration velocity. According to wave theory, there is a definite functional relationship between the vibration velocity and stress of the structure. By establishing this relationship, the stress safety control index in the design specification can be converted into a vibration velocity safety threshold, and then combined with the vibration velocity prediction model established in step S3, the grouting curtain design parameters that meet the safety requirements are determined. This method not only ensures the theoretical basis of the design, but also ensures the engineering practicality.

[0138] Specifically, the calculation idea of ​​grouting curtain design parameters can be described as follows:

[0139] a. Complete step S3 to obtain the vibration velocity prediction model of the protection structure considering the shock absorption performance of the grouting curtain;

[0140] b. If the safety control index is a non-vibration velocity index P1, the vibration velocity and P1 data of the protection structure under different working conditions are statistically analyzed, and the relationship between the vibration velocity of the protection structure and P1 is obtained by functional fitting. At the same time, the index safety control value of the protection structure under normal working conditions provided by the design specification is used, combined with the relationship between the vibration velocity of the protection structure and P1 to obtain the maximum allowable safe vibration velocity; if the safety control index is vibration velocity, skip this step.

[0141] c. Based on the engineering conditions, any two of the three main parameters (length, width, and height) of the grouting curtain are assumed, and the data of other influencing factors such as the amount of explosives, the density of the rock and soil, and the horizontal distance between the grouting curtain and the pipeline are substituted into the vibration velocity prediction model of the protective structure to obtain the value of the third parameter of the grouting curtain.

[0142] In a specific example, taking the protection structure as a pipeline as an example, the specific implementation process of step S4 is as follows:

[0143] In the process of monitoring buried pipelines, the vibration velocity can only directly reflect the dynamic response characteristics of the pipeline. Under the influence of blasting seismic waves, the safety performance of the pipeline and the failure mode of the pipeline material are mostly judged based on the strain or stress of the pipeline. According to wave theory, it can be inferred that there should also be a mathematical function relationship between the vibration velocity and stress of the pipeline. Therefore, the data of the two obtained from various numerical model results under complex working conditions are fitted. The fitting results are shown in equations (9) and Figure 4 .

[0144] σ=f(V p )=0.065V P -0.042 (9)

[0145] Where: σ is the peak effective stress of the pipeline, MPa; V P is the peak combined vibration velocity of the pipeline, cm·s -1 .

[0146] The Technical Specification for Buried High-Strength Polyvinyl Chloride Water Supply Pipeline Engineering provides a calculation formula for the maximum allowable stress of the pipe body during normal operation:

[0147] MOP=PN·f t (10)

[0148] Where: MOP is the maximum allowable stress for safe operation, MPa; PN is the nominal pressure, MPa; f t When the life span of the pipeline is required to be 50 years, the reduction coefficient of temperature to pressure is generally calculated as 0.8 at 32°C. The maximum allowable stress calculation formula for safe operation of the PVC pipe body during normal operation given in the "Technical Code for Buried High-Strength Polyvinyl Chloride Water Supply Pipeline Engineering" is used to calculate the maximum allowable stress for safe operation of the pipeline to be 1.76MPa. In addition, considering that the pipeline may have aging problems in actual projects, its actual maximum safe allowable working stress may be slightly reduced, so the pipeline stress safety factor is taken as 0.85, that is, the actual safe operation safety stress threshold [σ] = k·σ 0 =0.85MOP=1.496MPa, combined with the relationship between the stress and vibration velocity of the pipeline under the influence of blasting vibration in the above formula (9), the pipeline vibration velocity threshold [V P ] = f -1 ([σ])=([σ]+0.042) / 0.065=23.66cm·s -1 .

[0149] The pipeline vibration velocity threshold [V P ]Substituting into formula (8) we can get:

[0150]

[0151] According to different projects, by substituting different explosive sources and distances, we can get the relationship between the grouting curtain parameters and the horizontal distance between the grouting curtain and the pipeline. Then, according to the on-site environment and protection requirements, we can select appropriate parameters to design the grouting curtain scheme. In this embodiment, the shock absorption efficiency η = 0.85, the explosive source quantity Q = 20kg and the relative distance R between the explosion source and the pipeline 1 =15m, substituting into formula (11), the grouting curtain design scheme is shown in Table 2.

[0152] Table 2 Grouting curtain design example

[0153] Protection distance / m Grouting curtain length / m Grouting curtain height / m Grouting curtain width / m 1 1 1 0.180 1.5 1 1 0.206 2 1 1 0.225 2.5 1 1 0.242 3 1 1 0.263 3.5 1 1 0.285 4 1 1 0.304

[0154] In summary, the present invention proposes a scientific grouting curtain parameter design method for the engineering problem of structural protection under blasting vibration. The overall idea is to achieve structural protection by setting a grouting curtain on the propagation path of the blasting stress wave, combining theoretical analysis, numerical simulation and engineering practice. Specifically, the dimensional analysis Buckingham theorem is used to construct a vibration velocity prediction model, and the numerical simulation verification is carried out through ANSYS / LS-DYNA software. The vibration velocity-stress conversion relationship is established in combination with the design specifications, and the grouting curtain design parameters that meet the safety requirements are finally determined. The core principle of the present invention is based on wave theory, and the energy absorption and shock absorption effect of the grouting curtain material (a combination of cement mortar, rubber powder, iron powder and river sand) is used to weaken the impact of blasting vibration on the structure. This method is not only applicable to the protection of ground structures (such as buildings, elevated, high-voltage towers, etc.) and underground structures (such as underground pipelines, underground box culverts, underground tunnels, etc.), but also ensures the reliability of the design results through strict theoretical derivation and numerical verification (error control within 15%). The present invention successfully solves the technical problems that the shock absorption effect and parameters of the grouting curtain are difficult to determine in actual engineering, provides a scientific design method and reliable technical support for structural safety protection in blasting engineering, and has important engineering application value.

[0155] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A grouting curtain parameter design method for structural protection under blasting vibration, characterized in that: include: S1. Determine the main factors affecting the vibration velocity of the protected structure and use the dimensional analysis Buckingham theorem to construct a vibration velocity prediction model including unknown coefficients; S2. Establish a finite element blasting numerical model to obtain structural vibration velocity data under different parameter combinations; S3. Fitting the structural vibration velocity data using the vibration velocity prediction model to determine the undetermined coefficients in the vibration velocity prediction model; S4. Establish a relationship between structural vibration velocity and stress, determine a safety stress threshold based on design specifications, determine a structural vibration velocity safety threshold through the relationship, substitute the structural vibration velocity safety threshold into the vibration velocity prediction model of step S3, and determine the grouting curtain design parameters that meet the structural safety requirements in combination with engineering conditions.

2. The grouting curtain parameter design method for structural protection under blasting vibration according to claim 1, characterized in that: The grouting curtain is buried between the protective structure and the blasting source, that is, on the propagation path of the blasting stress wave, to interfere with the propagation of the blasting stress wave.

3. The grouting curtain parameter design method for structural protection under blasting vibration according to claim 2, characterized in that: The main factors affecting the vibration velocity of the protective structure include: Site parameters, including rock and soil density, rock and soil longitudinal wave velocity, rock and soil transverse wave velocity, soil moisture content and the distance between the protective structure and the explosion source; Explosive source parameters, including explosive quantity, charge diameter, blast hole diameter, explosive detonation velocity and explosive density; The grouting curtain parameters include the grouting curtain height, grouting curtain length, grouting curtain width and the horizontal distance between the grouting curtain and the protective structure.

4. The grouting curtain parameter design method for structural protection under blasting vibration according to claim 3 is characterized in that: The specific steps of using the dimensional analysis Buckingham theorem to construct a vibration velocity prediction model including undetermined coefficients in step S1 include: Select three factors from the main factors as dimensionally independent factors, and the remaining factors as dimensionally dependent factors, where any dimensionally independent factor cannot be calculated from the other two dimensionally independent factors using basic data; Convert dimensionally dependent factors into dimensionless numbers through the π theorem; According to the dimensionless homogeneity theorem and combined with dimensionless numbers, a vibration velocity prediction model including unknown coefficients is constructed.

5. The grouting curtain parameter design method for structural protection under blasting vibration according to claim 4, characterized in that: The dimensionally independent factors are the amount of explosives, the distance between the protective structure and the explosion source, and the longitudinal wave velocity of the rock and soil. The mathematical expression of the vibration velocity prediction model including the undetermined coefficients is as follows: Where V P is the vibration velocity of the protected structure; η is the damping efficiency; K, α1, α2, α3, α4, α5 are unknown coefficients, where: c is the longitudinal wave velocity of the rock and soil mass, ρ is the density of the rock and soil mass; R1 is the distance between the protective structure and the explosion source; R2 is the horizontal distance between the grouting curtain and the protective structure; H is the height of the grouting curtain; L is the length of the grouting curtain; W is the width of the grouting curtain; Q is the amount of explosives.

6. The grouting curtain parameter design method for structural protection under blasting vibration according to claim 3, characterized in that: Step S2 includes: S21. Use ANSYS / LS-DYNA software to establish a three-dimensional finite element model, and set the model size according to the actual range of action of the explosive and the size of the blast hole; S22, the model is divided using Lagrangian grids, where the protection structure and its surrounding areas are meshed; S23, setting boundary conditions, including: using non-reflection boundary conditions around the model and at the bottom, and using free boundary conditions at the top; S24, using the surface-to-surface contact algorithm to describe the soil-structure interaction and setting the corresponding friction coefficient; S25, select the material constitutive model, where: the soil adopts the Drucker-Prager constitutive model, the grouting curtain adopts the CONCRETE_DAMAGE_REL3 material model, and input the corresponding physical and mechanical parameters; S26. Setting working conditions with different parameter combinations by one of the following two methods: single factor impact analysis method, changing only one main factor at a time; or multi-factor orthogonal analysis method, changing multiple main factors at the same time; S27. According to the working condition of each parameter combination, simulation calculation is performed in a three-dimensional finite element model, and the reliability of the calculation results is verified to obtain numerical simulation results under the working conditions of different parameter combinations; S28. According to the numerical simulation results under the working conditions of different parameter combinations, the structural vibration velocity data under the working conditions of different parameter combinations are statistically obtained.

7. The grouting curtain parameter design method for structural protection under blasting vibration according to claim 6, characterized in that: In step S27, verifying the reliability of the calculation result includes: The soil pressure, acceleration or vibration velocity results of the same point in the numerical simulation and the indoor model test are read through the post-processing software lsprepost. If the waveforms of the two are close, the peak values ​​are not much different, and the errors of each point are within 15%, the numerical simulation results are judged to be reliable.

8. The grouting curtain parameter design method for structural protection under blasting vibration according to claim 4, characterized in that: Step S4 includes: S41. According to wave theory, the functional relationship between structural vibration velocity and stress is derived as follows: σ=f(V p ) Where, σ is the effective stress of the protection structure; V p To protect the structural vibration speed; S42. Determine the safety stress threshold based on the design specification: [σ]=k·σ0 In the formula, [σ] is the safety stress threshold, k is the safety factor, and σ0 is the maximum allowable stress specified in the design code; S43. The structural vibration speed safety threshold is obtained by inversely deducing the functional relationship between the structural vibration speed and the stress: [V p ]=f -1 ([σ]) In the formula, [V p ] is the structural vibration speed safety threshold, f -1 It is the inverse function of the relationship between structural vibration velocity and stress; S44, the structural vibration speed safety threshold [V p ] is substituted into the vibration velocity prediction model of step S3, and the design parameters of the grouting curtain that meet the structural safety requirements are determined in combination with the engineering conditions.

9. The grouting curtain parameter design method for structural protection under blasting vibration according to claim 1, characterized in that: The grouting curtain is composed of cement mortar, rubber powder, iron powder and river sand.

10. The grouting curtain parameter design method for structural protection under blasting vibration according to claim 1, characterized in that: The protective structure includes: Ground structures, including buildings, overhead and high-voltage towers; Underground structures include underground pipelines, underground box culverts and underground tunnels.

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