Underground cavern cyclic excavation blasting method based on ground stress dynamic monitoring

Abstract

This invention provides a method for cyclic excavation and blasting of underground caverns based on dynamic monitoring of ground stress, relating to the fields of geotechnical engineering and controlled blasting technology. The method includes: measuring ground stress and rock parameters to obtain the initial ground stress state and rock mechanical parameters; designing initial blasting units and implementing the first blast to form an initial fracture zone and a dynamic stress disturbance zone; dynamically monitoring the surrounding rock ground stress and inverting the stress field after blasting to obtain the spatiotemporal evolution characteristics of ground stress; optimizing subsequent blasting unit parameters and implementing cyclic blasting, adjusting the charge quantity, charge structure, and detonation sequence based on the inversion results, and repeating the monitoring and optimization steps to complete the excavation. This invention achieves the synergistic effect of blasting load and surrounding rock stress field through dynamic monitoring and cyclic optimization, improving energy utilization efficiency and reducing surrounding rock damage. It is applicable to the excavation of various high-stress underground caverns and has significant engineering practical value.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering and controlled blasting technology, specifically to a cyclic excavation blasting method for underground caverns (such as underground powerhouses, mine chambers, and hydraulic tunnels) based on dynamic monitoring of ground stress. This method introduces dynamic monitoring of ground stress during the excavation and blasting process, combined with multiple rounds of charging and blasting operations, to achieve cyclical control over the evolution of surrounding rock stress and the rock mass failure process, thereby improving the safety, controllability, and quality of underground cavern excavation. Background Technology

[0002] Underground cavern blasting excavation is a critical construction phase in water conservancy and hydropower, mining engineering, and underground space development. Especially under deep burial or high ground stress conditions, the surrounding rock is prone to significant stress redistribution and structural deterioration under blasting disturbance. Blasting loads not only cause local rock mass fracturing but also induce the release, transfer, and reconcentration of ground stress within the surrounding rock area, significantly impacting subsequent excavation processes and cavern stability.

[0003] In existing underground cavern blasting operations, the charge structure, borehole layout, and detonation sequence are often designed in a single phase based on initial geological survey results, empirical formulas, or numerical simulation analysis. These methods typically assume that the stress state of the surrounding rock changes only slightly during construction, or only consider the stress as an initial condition, making it difficult to reflect the dynamic evolution of the surrounding rock stress after blasting. In actual construction, as the number of blasting cycles increases, the stress in the surrounding rock continuously adjusts. If predetermined blasting parameters are still used, it can easily lead to reduced energy utilization efficiency, accumulated damage to the surrounding rock, and local instability.

[0004] In multi-round or zoned excavation of underground caverns, the initial blasting creates fracture zones and unloading zones in the surrounding rock, significantly altering the stress environment of the surrounding rock mass. The geostress state of subsequent blasting units often differs considerably from that in the initial design phase, and their fracture response becomes significantly more sensitive to charge quantity, detonation location, and blasting sequence. However, traditional blasting methods generally lack real-time means of acquiring the geostress state after blasting, failing to effectively incorporate surrounding rock stress evolution information into blasting parameter design. This often leads to problems such as over-excavation, under-excavation, uncontrolled fracture propagation, and unpredictable damage range of the surrounding rock during excavation.

[0005] While existing research has proposed some blasting control and parameter optimization methods, these technologies mainly focus on borehole layout, delay control, and vibration suppression, without dynamically adjusting the surrounding rock stress state throughout the blasting process. For example, patent CN109506529B proposes a composite slotting blasting method that improves tunneling blasting effects by arranging various types of boreholes and millisecond-level delays. However, this technology is still based on preset charge parameters and does not incorporate the post-blasting surrounding rock stress state into the dynamic optimization process of charge and detonation sequence. CN107505043A proposes a method for evaluating surrounding rock blasting damage, assessing the degree of damage through blasting vibration monitoring and rock mass quality classification. However, its monitoring results are used for post-experience evaluation and do not form a control strategy for real-time adjustment of blasting parameters. CN108592725A proposes a detonation sequence design method based on short time difference and void vibration reduction. Its core optimization direction is on fragmentation sequence and vibration control, which differs from the dynamic feedback control mechanism of ground stress that this invention focuses on. Summary of the Invention

[0006] This invention proposes a cyclic excavation blasting method for underground caverns based on dynamic monitoring of in-situ stress. This method is based on the release, transfer, and redistribution of in-situ stress in the surrounding rock during underground cavern excavation under blasting disturbance. By implementing in-situ stress monitoring between multiple blasting operations, the true stress state of the rock mass at different spatial locations at different times is obtained, and adjustments are made accordingly to the subsequent charge position, charge quantity, and blasting sequence. By incorporating the characteristics of in-situ stress evolution into the blasting parameter design process, this invention can guide fracture expansion under favorable stress conditions, achieving proactive control over the rock mass fracturing process.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for cyclic excavation and blasting of underground caverns based on dynamic monitoring of ground stress, comprising the following steps: Step 1, Measurement of ground stress and rock parameters: In the area to be excavated in the underground cavern, in-situ ground stress measurement is carried out on the surrounding rock to obtain the initial ground stress state of the surrounding rock, and mechanical parameter testing is conducted on the surrounding rock to obtain the rock mechanical parameters of the surrounding rock, providing basic data for subsequent blasting parameter design; Step 2, Initial blasting unit design and first blasting: Based on the initial ground stress state and rock mechanical parameters, an initial blasting unit is constructed to trigger the stress redistribution of the surrounding rock. The layout of blasting holes, charge parameters, charge structure and detonation method are determined, and the first blasting operation is carried out to form an initial fracture zone and a dynamic stress disturbance zone in the surrounding rock. Step 3, Dynamic monitoring and stress field inversion of surrounding rock after blasting: After the first blasting is completed, dynamic monitoring of the stress is carried out at predetermined locations around the cavern to obtain information on the change of stress in the surrounding rock under the blasting disturbance. Based on the monitoring results, the stress field of the surrounding rock after blasting is inverted and analyzed to obtain the spatial distribution and evolution characteristics of the stress in the surrounding rock. Step 4, Optimization and cyclic implementation of the charge and detonation sequence of subsequent blasting units based on the stress field after the initial blast: According to the distribution characteristics of the surrounding rock stress field after the blast obtained by inversion, the charge amount, charge structure and detonation sequence of subsequent blasting units are adjusted, and the next round of blasting is implemented. By repeating steps 3 and 4, a cyclic excavation and blasting process for underground caverns that adapts to the evolution characteristics of surrounding rock stress is formed.

[0008] Preferably, in step 1, the in-situ stress measurement uses the hydraulic fracturing method or the hollow inclusion method to determine the vertical stress, and the horizontal stress is calculated using the empirical formula of the lateral pressure coefficient. Among them, the initial in-situ stress of the surrounding rock is obtained, including data on its magnitude, direction and distribution characteristics.

[0009] Preferably, in step 1, the rock mechanical parameter testing includes determining the dynamic tensile strength of the rock through a dynamic tensile test, determining the longitudinal wave velocity using an ultrasonic detector, and determining the elastic modulus and Poisson's ratio through a triaxial compression test.

[0010] Preferably, step 2 specifically includes: in the initial blasting unit design stage, firstly, an engineering model of the underground cavern and its surrounding rock is established, the cavern excavation outline, the range of the surrounding rock structure and the blasting influence area are clarified, and the initial ground stress and rock mechanics parameters of the surrounding rock obtained in step 1 are introduced as the basic conditions for blasting parameter design. After the model is established, the parameters of the initial blasting unit are designed. The surrounding rock excavation area is divided into several blasting units. The arrangement of blasting holes in each blasting unit is determined. The hole diameter, hole depth, hole spacing and charge amount of the blasting holes are set. At the same time, the charge structure and detonation method are determined. Based on the magnitude of the initial ground stress and the direction of the principal stress, the arrangement of blasting holes and the detonation sequence are adjusted, and control measures are taken at the cavern outline boundary and in the non-excavation area. After completing the initial blasting unit design, the first blasting operation is carried out according to the determined blasting parameters and initiation method, so that the surrounding rock forms an initial fracture zone and a dynamic stress disturbance zone.

[0011] Preferably, in step 2, a dynamic load and stress wave propagation model for single-hole blasting is constructed based on explosion mechanics and transient wave theory. The borehole wall pressure is calculated by the explosive density, detonation velocity and adiabatic index. The borehole wall pressure is equivalent to the pulsed body force source term on the rock mass surface. The stress wave propagation law is analyzed by combining the rock mass elastic wave equation and constitutive relation.

[0012] Preferably, step 3 specifically includes: after the initial blasting is completed, deploying ground stress monitoring devices at predetermined locations in the surrounding rock around the cavern to construct a dynamic monitoring system for surrounding rock ground stress; continuously monitoring the change process of surrounding rock ground stress with time and space under the blasting disturbance to obtain surrounding rock ground stress evolution data; and based on the obtained ground stress monitoring data, performing inversion analysis on the surrounding rock ground stress field after blasting to obtain the spatial distribution characteristics and evolution state of surrounding rock ground stress.

[0013] Preferably, in step 3, the ground stress monitoring device is an embedded stress gauge, strain gauge, microseismic sensor or distributed fiber optic sensing system. The stress field inversion is based on static equilibrium conditions, the superposition relationship between initial and dynamic stresses, and the elastic constitutive relationship of the rock mass, combined with monitoring data to obtain the spatiotemporal evolution characteristics of surrounding rock stress.

[0014] Preferably, in step 3, when the maximum principal tensile stress in a local area of ​​the surrounding rock is greater than the dynamic tensile strength of the rock, or the maximum principal shear stress is greater than the dynamic shear strength of the rock, the area is determined to have entered a dynamic stress window range that is conducive to crack initiation and propagation.

[0015] Preferably, in step 4, the charge adjustment coefficient is determined based on the relationship between the dynamic stress peak value at the location of the subsequent blasting unit and the dynamic strength parameters of the rock. The charge amount of the subsequent blasting unit is the product of the baseline charge amount and the charge adjustment function. The charge adjustment function is determined segmentally according to the dynamic stress state, and the charge adjustment coefficient ranges from 0.6 to 1.5.

[0016] Preferably, in step 4, the detonation delay of the subsequent blasting unit is determined based on the propagation characteristics of the initial blasting stress wave and the dynamic stress window range. The detonation delay range is from the start time when the dynamic stress reaches the threshold for promoting crack propagation to the end time, thereby realizing the temporal superposition of the blasting load and the dynamic stress field of the surrounding rock.

[0017] The present invention has the following beneficial effects: 1. This invention provides a method for cyclic excavation blasting of underground caverns based on dynamic monitoring of ground stress. By introducing a dynamic detection and analysis mechanism for surrounding rock stress during cavern blasting, the spatiotemporal evolution characteristics of the surrounding rock stress field after the initial blast are obtained, and dynamic stress action intervals favorable for fracture initiation and propagation are identified. Based on this, the charge amount and detonation sequence of subsequent blasting units are differentiated, allowing the blasting load to act synergistically on the rock mass under favorable dynamic stress conditions, thereby achieving efficient utilization of blasting energy and active control of the rock mass fracturing process. This method overcomes the limitations of traditional empirical methods that neglect the propagation and superposition effects of blasting stress waves, improving the scientific rigor and reliability of underground cavern blasting design.

[0018] 2. The present invention provides a cyclic excavation blasting method for underground caverns based on dynamic monitoring of ground stress, which can be widely applied to high ground stress engineering environments such as deep-buried tunnels, underground caverns, and mine roadways. By constructing a cyclic excavation mode of "blasting-monitoring-analysis-adjustment", the effective fracture zone is expanded under the same charge conditions, promoting the stable propagation of fractures along the design direction and reducing non-target cracks and damage to the surrounding rock.

[0019] 3. The method of the present invention can effectively improve the quality of the tunnel outline formation, reduce the amount of over-excavation and trimming work, and provide a new technical approach for blasting construction and parameter optimization of underground engineering under complex geostress conditions. Attached Figure Description

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] Figure 1 This is a technical roadmap for a specific implementation of the present invention; Figure 2 This is a diagram showing the propagation of stress waves and crack propagation under explosive loads according to the present invention. Figure 3 This is a model diagram of the superposition effect of explosion stress waves and the coupling effect of ground stress in a certain blast hole of the present invention; Figure 4 This is a layout diagram of the cyclic blasting charge scheme of the present invention; Figure 5 This invention presents a comparison of the blasting effects under different methods. Detailed Implementation

[0022] The technical solution of the present invention will be described in detail below with reference to the embodiments.

[0023] Example 1: A method for cyclic excavation and blasting of underground caverns based on dynamic monitoring of ground stress includes the following steps: Step 1, Measurement of ground stress and rock parameters: In the area to be excavated in the underground cavern, in-situ ground stress measurement is carried out on the surrounding rock to obtain the initial ground stress state of the surrounding rock, and mechanical parameter testing is conducted on the surrounding rock to obtain the mechanical parameters of the surrounding rock, providing basic data for subsequent blasting parameter design; Furthermore, the parameters involved in step 1 include vertical ground stress, horizontal ground stress, lateral pressure coefficient, dynamic tensile strength of rock, longitudinal wave velocity of rock, and Poisson's ratio.

[0024] Furthermore, step 1 specifically includes: In the construction area of ​​the tunnel to be blasted, the initial in-situ stress state of the rock mass and the rock mechanics parameters of the surrounding rock are first obtained. Vertical in-situ stress is then determined using the hydraulic fracturing method or the hollow inclusion method. Then, based on the lateral pressure coefficient Empirical formula: (1) Calculation of horizontal stress .in, This is the empirical lateral pressure coefficient of the rock mass, which can be selected or modified according to lithology, burial depth and geological conditions.

[0025] Simultaneously, mechanical parameter tests were conducted on the surrounding rock, and the dynamic tensile strength of the rock was determined through dynamic tensile tests (such as the Hopkinson bar test). The longitudinal wave velocity is obtained using an ultrasonic detector. The elastic modulus of the rock was determined by triaxial compression test. Compared to Poisson Based on the above test results, the distribution characteristics of the geostress field and rock mechanical parameters of the surrounding rock in the construction area were established, providing a basis for subsequent blasting parameter design and dynamic evolution analysis of geostress.

[0026] Step 2, Initial blasting unit design and first blasting: Based on the initial ground stress state and the rock mechanics parameters of the surrounding rock, an initial blasting unit is constructed to trigger the stress redistribution of the surrounding rock. The layout of blasting holes, charge parameters, charge structure and detonation method are determined, and the first blasting operation is carried out to form an initial fracture zone and a dynamic stress disturbance zone in the surrounding rock. Furthermore, the parameters involved in step 2 include density, detonation velocity, and adiabatic index.

[0027] Furthermore, step 2 specifically includes: After obtaining the initial geostress state and rock mechanics parameters of the surrounding rock of the cavern to be excavated, an initial blasting unit is constructed to trigger stress redistribution and fracture evolution in the surrounding rock. The initial blasting unit refers to the minimum blasting system composed of blast hole arrangement, explosive parameters, charge structure, and detonation method in the central area or predetermined location of the cavern. Its purpose is to form a controllable initial fracture zone and dynamic stress disturbance zone, providing reference stress conditions for subsequent cyclic blasting.

[0028] Before constructing the blasting load, the density needs to be determined according to the type of explosive (such as emulsion explosives or ammonium nitrate explosives). , explosive speed and insulation index The above parameters are used to characterize the energy release characteristics during explosive detonation and serve as the basic input for blasting dynamics analysis. Based on explosion mechanics and transient wave theory, a dynamic load and stress wave propagation model induced by single-hole blasting is constructed. Single-hole blasting can be regarded as an instantaneous energy release source, and its borehole wall pressure... It can be calculated from the explosive parameters: (2) The aforementioned pressure, acting as a transient disturbance on the borehole wall, can be equivalent to a pulsed body force source term on the rock mass surface. Its mathematical form is expressed as: (3) In the formula The Dirac function is used to characterize instantaneous and locally applied impulses. For reference distance, To calculate the distance from the point to the center of the blast hole, The time variable is used. After the pulse excitation enters the rock mass, the driving medium generates a displacement response. As an isotropic linear elastic material, the dynamic response of the rock mass satisfies the two-dimensional elastic wave equation: (4) In the formula For rock mass density, It is a displacement vector. and Let Lamé constant be . It is a spatial differential operator used to describe the variation of the displacement field in spatial directions. This refers to the body force source term generated by the explosion. The stress components are determined according to the constitutive relation: (5) The stress disturbance induced by pulse excitation diffuses over time and space, forming compression and shear waves. Considering geometric diffusion and material energy dissipation effects, at any distance outside the point of application... The peak value of the stress wave can be written as: (6) The geometrical attenuation exponent (for two-dimensional plane waves) is taken as... Three-dimensional spherical waves ), is the rock mass material attenuation coefficient.

[0029] Considering rock mass impedance The effect of stress wave propagation can be calculated using the wave impedance matching formula at the interface, considering wave transmission and reflection at the interface. , (7) In the formula The reflection coefficient, The transmittance is the coefficient of light. , These represent the impedances of the rock masses on both sides of the interface.

[0030] Based on the above blasting dynamics model, combined with the cavern geometry and the geostress state and rock mechanics parameters obtained in the above steps, the hole spacing, hole depth, charge amount and detonation method of the blasting holes in the initial blasting unit are determined, and the charge and detonation system layout is completed. The first blasting operation is carried out to form an initial fracture zone and a significant dynamic stress disturbance zone in the surrounding rock, providing initial conditions for subsequent cyclic blasting based on geostress dynamic monitoring.

[0031] Step 3, Dynamic monitoring and stress field inversion of surrounding rock after blasting: After the first blasting is completed, dynamic monitoring of the stress is carried out at predetermined locations around the cavern to obtain information on the change of stress in the surrounding rock under the blasting disturbance. Based on the monitoring results, the stress field of the surrounding rock after blasting is inverted and analyzed to obtain the spatial distribution and evolution characteristics of the stress in the surrounding rock. Furthermore, step 3 specifically includes: After the initial blasting of the initial blasting unit, stress and dynamic response monitoring devices are deployed in the surrounding rock around the cavern and at predetermined monitoring locations to continuously monitor the time-varying evolution of the stress state of the surrounding rock under the influence of blasting disturbance. These monitoring devices include, but are not limited to, embedded stress gauges, strain gauges, microseismic sensors, or distributed fiber optic sensing systems, used to collect time-history data of stress, strain, and vibration signals within the surrounding rock after blasting. This is based on the static equilibrium conditions satisfied by the rock mass: (8) In the formula and These respectively represent the rock mass in direction and Normal stress components in the direction, For the rock mass in Shear stress components on a plane.

[0032] Simultaneously, considering the propagation characteristics of blasting stress waves, the instantaneous stress state at any location in the surrounding rock under initiation can be expressed as the superposition relationship between the initial ground stress field and the dynamic stress field induced by initiation, i.e.: (9) In the formula To compute the position vector of any observation point in the computation domain, For the observation time, This represents the initial geostress of the rock mass. This refers to the dynamic stress disturbance term induced by the detonation.

[0033] After detonation, the dynamic stress disturbance term and the strain response of the surrounding rock satisfy the elastic constitutive relation of the rock mass, and its stress-strain relationship can be expressed as: (10) In the formula The elastic constitutive matrix of the rock mass. The dynamic strain tensor acquired by the monitoring system.

[0034] Based on the stress or strain time history data collected by the monitoring system, and combined with the blasting stress wave propagation model established in step 2, the dynamic stress field of the surrounding rock after detonation is inverted and analyzed. This is achieved by analyzing the arrival time of dynamic stress waves at different monitoring points. Peak pressure Based on a comparative analysis of the attenuation characteristics, the propagation velocity of dynamic stress waves in the surrounding rock can be expressed as: (11) In the formula The distance between adjacent monitoring points; This represents the time difference between the arrival of the corresponding stress peak.

[0035] Furthermore, by combining the stress wave attenuation model, the dynamic stress disturbance at any location in the surrounding rock after detonation is estimated, and its expression is as follows: (12) In the formula, For reference distance, To calculate the distance from the point to the detonation source, The geometric decay exponent, Rock mass material attenuation coefficient This is a function that describes the time history characteristics of stress waves.

[0036] Based on the above inversion results, the spatial and temporal evolution and distribution characteristics of the dynamic stress field of the surrounding rock after detonation are obtained. Further analysis of the dynamic principal stress variation over time is performed when the local area of ​​the surrounding rock satisfies: or (13) At that time, the region was determined to have entered a dynamic stress window range conducive to crack initiation and propagation. Among these, For the maximum principal tensile stress, For the maximum shear stress, and These are the dynamic tensile strength and dynamic shear strength of the rock, respectively.

[0037] Based on the above results of dynamic stress monitoring and stress field inversion after detonation, a dynamic evolution model of surrounding rock stress is constructed to clarify the range of detonation disturbance, stress redistribution characteristics, and the location and scale of potential damage zones, providing quantitative input conditions for subsequent differentiated charge design and detonation sequence optimization based on dynamic stress field evolution.

[0038] Step 4, Optimization and cyclic implementation of the charge and detonation sequence of subsequent blasting units based on the stress field after the initial blast: According to the distribution characteristics of the surrounding rock stress field after the blast obtained by inversion, the charge amount, charge structure and detonation sequence of subsequent blasting units are adjusted, and the next round of blasting is implemented. By repeating steps 3 and 4, a cyclic excavation and blasting process for underground caverns that adapts to the evolution characteristics of surrounding rock stress is formed.

[0039] Furthermore, step 4 specifically includes: Based on the inversion results of the dynamic stress field of the surrounding rock after the initial blasting obtained in step 3, the stress redistribution characteristics at different spatial locations around the cavern are analyzed. According to the magnitude of the dynamic principal stress, the degree of stress concentration, and the spatiotemporal distribution characteristics of the stress window interval at each location, the area to be blasted is divided into multiple subsequent blasting units, and the actual stress state of each blasting unit after the initial blasting is identified.

[0040] For any subsequent blasting element, the dynamic stress peak value obtained from its location is used as the basis. The relationship between the explosive charge and the dynamic strength parameters of the rock is used to determine the corresponding charge adjustment coefficient. The charge amount for subsequent blasting units is then determined. It can be represented as: (14) In the formula, This is the baseline charge amount used under conditions without dynamic stress superposition. This is a charge adjustment function based on the dynamic stress level after detonation.

[0041] The charge adjustment function Determined based on segmentation of dynamic stress state, when: (15) When the blasting unit is determined to be in a favorable fracture stress zone, the charge amount is appropriately reduced to: (16) When the following conditions are met: (17) When the blasting unit is determined to be in a stress-deficient zone, the explosive charge is increased or the blasting effect is enhanced to: (18) Among them, the charge adjustment coefficient The value can be selected from 0.6 to 1.5 based on engineering experience or test calibration.

[0042] Meanwhile, the detonation delay of subsequent blasting units can be determined based on the propagation characteristics of the initial blasting stress wave and the stress window range, and its delay range meets the following requirements. (19) in and These represent the start and end times when the dynamic stress reaches the threshold for promoting fracture propagation. By controlling the initiation of subsequent blasting units within the stress window interval, the temporal superposition of the blasting load and the dynamic stress field of the surrounding rock is achieved.

[0043] After determining the charge and detonation parameters for subsequent blasting units, the next round of blasting is carried out to induce controlled fracturing of the surrounding rock based on the existing stress disturbance. Subsequently, steps 3 and 4 are repeated, namely, the dynamic stress state of the surrounding rock after each round of blasting is detected and inverted, and the charge amount and detonation sequence of subsequent blasting units are continuously adjusted accordingly until the excavation, widening, or shaping excavation of the cavern is completed.

[0044] Through the above-mentioned cyclic blasting and dynamic optimization process, the blasting energy is efficiently utilized in the surrounding rock, realizing the zoned fracturing and orderly expansion of the surrounding rock of the cavern, reducing ineffective energy dissipation and unnecessary damage to the surrounding rock, and improving the excavation quality and construction safety of the cavern.

[0045] Example 2: The following is in conjunction with the embodiments and appendices Figure 2-5 The technical solution of this invention will be described in detail below. This embodiment uses a smooth blasting test of a deep-buried granite water diversion tunnel as an example, but this does not constitute a limitation on the scope of protection of this invention. The technical route of implementation is as follows: Figure 1 As shown.

[0046] Step 1: Measurement of In-situ Stress and Rock Parameters. In the construction area of ​​the tunnel to be blasted, the initial in-situ stress state and rock mechanical parameters of the rock mass are first obtained. Vertical in-situ stress is determined using the hydraulic fracturing method or the hollow inclusion method. Then, based on the lateral pressure coefficient Empirical formula: (1) Calculation of horizontal stress .in, This is the empirical lateral pressure coefficient of the rock mass, which can be selected or modified according to lithology, burial depth and geological conditions.

[0047] Simultaneously, mechanical parameter tests were conducted on the surrounding rock, and the dynamic tensile strength of the rock was determined through dynamic tensile tests (such as the Hopkinson bar test). The longitudinal wave velocity is obtained using an ultrasonic detector. The elastic modulus of the rock was determined by triaxial compression test. Compared to Poisson In this example, the vertical in-situ stress is 30 MPa, the lateral pressure coefficient is selected as 1.5, and the calculated horizontal in-situ stress is 45 MPa. The dynamic tensile strength of the rock is 12 MPa, the longitudinal wave velocity is 4800 m / s, and the Poisson's ratio is 0.23. Based on the above test results, the distribution characteristics of the in-situ stress field and rock mechanical parameters of the surrounding rock in the construction area are established, providing a basis for subsequent blasting parameter design and dynamic evolution analysis of in-situ stress.

[0048] Step 2, Initial Blasting Unit Design and First Blasting Implementation. After obtaining the initial geostress state and rock mechanics parameters of the surrounding rock of the cavern to be excavated, an initial blasting unit is constructed to trigger stress redistribution and fracture evolution in the surrounding rock. The initial blasting unit refers to the smallest blasting system in the central region or predetermined location of the cavern, consisting of the arrangement of blasting holes, explosive parameters, charge structure, and detonation method. Its purpose is to form a controllable initial fracturing zone and dynamic stress disturbance zone, providing reference stress conditions for subsequent cyclic blasting. See details... Figure 2 .

[0049] Before constructing the blasting load, the density needs to be determined according to the type of explosive (such as emulsion explosives or ammonium nitrate explosives). , explosive speed and insulation index In this example, the explosive density is 1200 kg / m³, the detonation velocity is 4500 m / s, the adiabatic index is 2.8, and the borehole radius is 0.04 m. These parameters characterize the energy release characteristics during explosive detonation and serve as the basic input for blasting dynamics analysis. Based on explosion mechanics and transient wave theory, a dynamic load and stress wave propagation model induced by single-hole blasting is constructed. Single-hole blasting can be considered as an instantaneous energy release source, with its borehole wall pressure... It can be calculated from the explosive parameters: (2) The aforementioned pressure, acting as a transient disturbance on the borehole wall, can be equivalent to a pulsed body force source term on the rock mass surface. Its mathematical form is expressed as: (3) In the formula The Dirac function is used to characterize instantaneous and locally applied impulses. For reference distance, To calculate the distance from the point to the center of the blast hole, The time variable is used. After the pulse excitation enters the rock mass, the driving medium generates a displacement response. As an isotropic linear elastic material, the dynamic response of the rock mass satisfies the two-dimensional elastic wave equation: (4) In the formula For rock mass density, It is a displacement vector. and Let Lamé constant be . It is a spatial differential operator used to describe the variation of the displacement field in spatial directions. This refers to the body force source term generated by the explosion. The stress components are determined according to the constitutive relation: (5) The stress disturbance induced by pulse excitation diffuses over time and space, forming compression and shear waves. Considering geometric diffusion and material energy dissipation effects, at any distance outside the point of application... The peak value of the stress wave can be written as: (6) The geometrical attenuation exponent (for two-dimensional plane waves) is taken as... Three-dimensional spherical waves ), is the rock mass material attenuation coefficient.

[0050] Considering rock mass impedance The effect of stress wave propagation can be calculated using the wave impedance matching formula at the interface, considering wave transmission and reflection at the interface. , (7) In the formula The reflection coefficient, The transmittance is the coefficient of light. , These represent the impedances of the rock masses on both sides of the interface.

[0051] Based on the above blasting dynamics model, combined with the cavern geometry and the geostress state and rock mechanics parameters obtained in the above steps, the hole spacing, hole depth, charge amount and detonation method of the blasting holes in the initial blasting unit are determined, and the charge and detonation system layout is completed. The first blasting operation is carried out to form an initial fracture zone and a significant dynamic stress disturbance zone in the surrounding rock, providing initial conditions for subsequent cyclic blasting based on geostress dynamic monitoring.

[0052] Step 3: Post-blasting dynamic monitoring and stress field inversion of surrounding rock. After the initial blasting of the initial blasting unit, stress and dynamic response monitoring devices are deployed in the surrounding rock around the tunnel and at predetermined monitoring locations to continuously monitor the time-varying evolution of the surrounding rock stress state under the blasting disturbance. The detected data are shown in [link to data]. Figure 3 The monitoring devices include, but are not limited to, embedded stress gauges, strain gauges, microseismic sensors, or distributed fiber optic sensing systems, used to collect time-history data of stress, strain, and vibration signals within the surrounding rock after blasting. Based on the static equilibrium conditions satisfied by the rock mass: (8) In the formula and These respectively represent the rock mass in direction and Normal stress components in the direction, For the rock mass in Shear stress components on a plane.

[0053] Simultaneously, considering the propagation characteristics of blasting stress waves, the instantaneous stress state at any location in the surrounding rock under initiation can be expressed as the superposition relationship between the initial ground stress field and the dynamic stress field induced by initiation, i.e.: (9) In the formula To compute the position vector of any observation point in the computation domain, For the observation time, This represents the initial geostress of the rock mass. This refers to the dynamic stress disturbance term induced by the detonation.

[0054] After detonation, the dynamic stress disturbance term and the strain response of the surrounding rock satisfy the elastic constitutive relation of the rock mass, and its stress-strain relationship can be expressed as: (10) In the formula The elastic constitutive matrix of the rock mass. The dynamic strain tensor acquired by the monitoring system.

[0055] Based on the stress or strain time history data collected by the monitoring system, and combined with the blasting stress wave propagation model established in step 2), the dynamic stress field of the surrounding rock after detonation is inverted and analyzed. This is achieved by analyzing the arrival time of dynamic stress waves at different monitoring points. Peak pressure Based on a comparative analysis of the attenuation characteristics, the propagation velocity of dynamic stress waves in the surrounding rock can be expressed as: (11) In the formula is the distance between adjacent monitoring points, and s is the arrival time difference of the corresponding stress peak.

[0056] Furthermore, by combining the stress wave attenuation model, the dynamic stress disturbance at any location in the surrounding rock after detonation is estimated, and its expression is as follows: (12) In the formula, For reference distance, To calculate the distance from the point to the detonation source, The geometric decay exponent, Rock mass material attenuation coefficient This is a function that describes the time history characteristics of stress waves.

[0057] Based on the above inversion results, the spatial and temporal evolution and distribution characteristics of the dynamic stress field of the surrounding rock after detonation are obtained. Further analysis of the dynamic principal stress variation over time reveals that when local areas of the surrounding rock satisfy… or (13) This region was determined to be within a dynamic stress window range conducive to crack initiation and propagation. For the maximum principal tensile stress, For the maximum shear stress, and These are the dynamic tensile strength and dynamic shear strength of the rock, respectively.

[0058] Based on the above results of dynamic stress monitoring and stress field inversion after detonation, a dynamic evolution model of surrounding rock stress is constructed to clarify the range of detonation disturbance, stress redistribution characteristics, and the location and scale of potential damage zones, providing quantitative input conditions for subsequent differentiated charge design and detonation sequence optimization based on dynamic stress field evolution.

[0059] Step 4, Optimization and cyclical implementation of subsequent blasting unit charging and detonation sequence based on the stress field after the initial blast: Based on the inversion results of the dynamic stress field of the surrounding rock after the initial blast obtained in Step 3), the stress redistribution characteristics at different spatial locations around the cavern are analyzed. According to the magnitude of the dynamic principal stress, the degree of stress concentration, and the spatiotemporal distribution characteristics of the stress window interval at each location, the area to be blasted is divided into multiple subsequent blasting units, as detailed in [link to details]. Figure 4 .

[0060] For any subsequent blasting element, the dynamic stress peak value obtained from its location is used as the basis. The relationship between the explosive charge and the dynamic strength parameters of the rock is used to determine the corresponding charge adjustment coefficient. The charge amount for subsequent blasting units is then determined. It can be represented as: (14) In the formula, This is the baseline charge amount used under conditions without dynamic stress superposition. This is a charge adjustment function based on the dynamic stress level after detonation.

[0061] The charge adjustment function Determined based on segmentation of dynamic stress state, when: (15) When the blasting unit is determined to be in a favorable fracture stress zone, the charge amount is appropriately reduced to: (16) When the following conditions are met: (17) When the blasting unit is determined to be in a stress-deficient zone, the explosive charge is increased or the blasting effect is enhanced to: (18) Among them, the charge adjustment coefficient The value can be selected from 0.6 to 1.5 based on engineering experience or test calibration.

[0062] Meanwhile, the detonation delay of subsequent blasting units can be determined based on the propagation characteristics of the initial blasting stress wave and the stress window range, and its delay range meets the following requirements. (19) in and These represent the start and end times when the dynamic stress reaches the threshold for promoting fracture propagation. By controlling the initiation of subsequent blasting units within the stress window interval, the temporal superposition of the blasting load and the dynamic stress field of the surrounding rock is achieved.

[0063] After determining the charge and detonation parameters for subsequent blasting units, the next round of blasting is carried out to induce controlled fracturing of the surrounding rock based on the existing stress disturbance. Subsequently, steps 3) and 4) are repeated, that is, the dynamic stress state of the surrounding rock after each round of blasting is detected and inverted, and the charge amount and detonation sequence of subsequent blasting units are continuously adjusted accordingly until the excavation, widening, or shaping excavation of the cavern is completed.

[0064] Comparison of effects of each example Under the same charge conditions, the underground cavern cyclic excavation blasting method based on dynamic ground stress monitoring of this invention results in blast-induced cracks that steadily propagate along the design direction under the synergistic effect of dynamic stress, leading to a significantly larger and more uniform effective fracture zone. Figure 5As shown, compared to traditional blasting methods, the surrounding rock participates in the fragmentation process under favorable dynamic stress conditions, allowing for more efficient use of blasting energy in both time and space. The damage range to the surrounding rock is effectively controlled, and the quality and extent of the tunnel outline formation are significantly improved. Simultaneously, without increasing the amount of explosives, blasting efficiency is increased, and the workload of blasting and manual finishing is reduced, resulting in an overall blasting effect superior to traditional methods.

[0065] Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many specific modifications under the guidance of the present invention without departing from the spirit of the invention and the scope of protection of the claims, and these modifications all fall within the scope of protection of the present invention.

Claims

1. A method for cyclic excavation and blasting of underground caverns based on dynamic monitoring of ground stress, characterized in that, Includes the following steps: Step 1, Measurement of ground stress and rock parameters: In the area to be excavated in the underground cavern, in-situ ground stress measurement is carried out on the surrounding rock to obtain the initial ground stress state of the surrounding rock, and mechanical parameter testing is conducted on the surrounding rock to obtain the rock mechanical parameters of the surrounding rock, providing basic data for subsequent blasting parameter design; Step 2, Initial blasting unit design and first blasting: Based on the initial ground stress state and rock mechanical parameters, an initial blasting unit is constructed to trigger the stress redistribution of the surrounding rock. The layout of blasting holes, charge parameters, charge structure and detonation method are determined, and the first blasting operation is carried out to form an initial fracture zone and a dynamic stress disturbance zone in the surrounding rock. Step 3, Dynamic monitoring and stress field inversion of surrounding rock after blasting: After the first blasting is completed, dynamic monitoring of the stress is carried out at predetermined locations around the cavern to obtain information on the change of stress in the surrounding rock under the blasting disturbance. Based on the monitoring results, the stress field of the surrounding rock after blasting is inverted and analyzed to obtain the spatial distribution and evolution characteristics of the stress in the surrounding rock. Step 4, Optimization and cyclic implementation of the charge and detonation sequence of subsequent blasting units based on the stress field after the initial blast: According to the distribution characteristics of the surrounding rock stress field after the blast obtained by inversion, the charge amount, charge structure and detonation sequence of subsequent blasting units are adjusted, and the next round of blasting is implemented. By repeating steps 3 and 4, a cyclic excavation and blasting process for underground caverns that adapts to the evolution characteristics of surrounding rock stress is formed.

2. The underground cavern cyclic excavation and blasting method based on dynamic monitoring of ground stress according to claim 1, characterized in that, In step 1, the in-situ stress measurement uses the hydraulic fracturing method or the hollow inclusion method to determine the vertical stress, and the horizontal stress is calculated using the empirical formula of the lateral pressure coefficient. Among them, the initial in-situ stress of the surrounding rock is obtained, including data on its magnitude, direction and distribution characteristics.

3. The underground cavern cyclic excavation and blasting method based on dynamic monitoring of ground stress according to claim 1, characterized in that, In step 1, the rock mechanical parameter testing includes determining the dynamic tensile strength of the rock through dynamic tensile testing, measuring the longitudinal wave velocity with an ultrasonic detector, and determining the elastic modulus and Poisson's ratio through triaxial compression testing.

4. The method for cyclic excavation and blasting of underground caverns based on dynamic monitoring of ground stress according to claim 1, characterized in that, Step 2 specifically includes: In the initial blasting unit design stage, firstly, an engineering model of the underground cavern and its surrounding rock is established to clarify the cavern excavation outline, the range of the surrounding rock structure and the blasting influence area, and the initial ground stress and rock mechanics parameters of the surrounding rock obtained in Step 1 are introduced as the basic conditions for blasting parameter design. After the model is established, the parameters of the initial blasting unit are designed. The surrounding rock excavation area is divided into several blasting units. The arrangement of blasting holes in each blasting unit is determined. The hole diameter, hole depth, hole spacing and charge amount of the blasting holes are set. At the same time, the charge structure and detonation method are determined. Based on the magnitude of the initial ground stress and the direction of the principal stress, the arrangement of blasting holes and the detonation sequence are adjusted, and control measures are taken at the cavern outline boundary and in the non-excavation area. After completing the initial blasting unit design, the first blasting operation is carried out according to the determined blasting parameters and initiation method, so that the surrounding rock forms an initial fracture zone and a dynamic stress disturbance zone.

5. The underground cavern cyclic excavation and blasting method based on dynamic monitoring of ground stress according to claim 4, characterized in that, In step 2, a dynamic load and stress wave propagation model for single-hole blasting is constructed based on explosion mechanics and transient wave theory. The borehole wall pressure is calculated by using explosive density, detonation velocity and adiabatic index. The borehole wall pressure is equivalent to the pulsed body force source term on the rock mass surface. The stress wave propagation law is analyzed by combining the rock mass elastic wave equation and constitutive relation.

6. The method for cyclic excavation and blasting of underground caverns based on dynamic monitoring of ground stress according to claim 4, characterized in that, Step 3 specifically includes: after the initial blasting is completed, deploying ground stress monitoring devices at predetermined locations in the surrounding rock around the cavern to construct a dynamic monitoring system for surrounding rock ground stress; continuously monitoring the change process of surrounding rock ground stress with time and space under the blasting disturbance to obtain surrounding rock ground stress evolution data; and based on the obtained ground stress monitoring data, performing inversion analysis on the surrounding rock ground stress field after blasting to obtain the spatial distribution characteristics and evolution state of surrounding rock ground stress.

7. The method for cyclic excavation and blasting of underground caverns based on dynamic monitoring of ground stress according to claim 6, characterized in that, In step 3, the ground stress monitoring device adopts an embedded stress gauge, strain gauge, microseismic sensor or distributed fiber optic sensing system. The stress field inversion is based on static equilibrium conditions, the superposition relationship between initial and dynamic stresses, and the elastic constitutive relationship of the rock mass, combined with monitoring data to obtain the spatiotemporal evolution characteristics of surrounding rock stress.

8. The method for cyclic excavation and blasting of underground caverns based on dynamic monitoring of ground stress according to claim 7, characterized in that, In step 3, when the maximum principal tensile stress in a local area of ​​the surrounding rock is greater than the dynamic tensile strength of the rock, or the maximum principal shear stress is greater than the dynamic shear strength of the rock, the area is determined to have entered a dynamic stress window range that is conducive to crack initiation and propagation.

9. The method for cyclic excavation and blasting of underground caverns based on dynamic monitoring of ground stress according to claim 1, characterized in that, In step 4, the charge adjustment coefficient is determined based on the relationship between the peak dynamic stress at the location of the subsequent blasting unit and the dynamic strength parameters of the rock. The charge amount of the subsequent blasting unit is the product of the baseline charge amount and the charge adjustment function. The charge adjustment function is determined segmentally according to the dynamic stress state, and the charge adjustment coefficient ranges from 0.6 to 1.

5.

10. The method for cyclic excavation and blasting of underground caverns based on dynamic monitoring of ground stress according to claim 1, characterized in that, In step 4, the detonation delay of subsequent blasting units is determined based on the propagation characteristics of the initial blasting stress wave and the dynamic stress window range. The detonation delay range is from the start time when the dynamic stress reaches the threshold for promoting crack propagation to the end time, thereby realizing the temporal superposition of blasting load and surrounding rock dynamic stress field.

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