Deep tunnel circular blasting excavation surrounding rock accumulated damage analysis method and system

Abstract

The invention relates to the technical field of surrounding rock damage analysis, in particular to a deep-buried tunnel circulating blasting excavation surrounding rock accumulated damage analysis method and a deep-buried tunnel circulating blasting excavation surrounding rock accumulated damage analysis system. Further determining the effect of blasting and ground stress on surrounding rock damage during blasting excavation of the deep tunnel; under the action of blasting and ground stress, the influence of single-cycle blasting excavation and multi-cycle blasting excavation on surrounding rock damage is considered, and the cumulative damage variable of the rock mass is calculated; and evaluating the stable state of the surrounding rock according to the calculated accumulated damage variable, and optimizing a blasting design scheme and a support time sequence. According to the method, on the basis of considering the comprehensive action of blasting and ground stress, accurate calculation of the accumulated damage of the surrounding rock during deep-buried tunnel circulating blasting excavation is realized by analyzing the influence of single-circulation multi-section blast hole delayed blasting and multi-circulation blasting on the damage of the surrounding rock, so that a blasting design scheme and a support time sequence are optimized; and the safety of tunnel engineering is improved.

Description

Technical Field

[0001] This invention relates to the field of surrounding rock damage analysis technology, and in particular to a method and system for cumulative damage analysis of surrounding rock during cyclic blasting excavation of deep-buried tunnels. Background Technology

[0002] In the field of deep-buried tunnel blasting excavation, surrounding rock damage analysis is one of the core technologies for ensuring construction safety. In recent years, with the development of blasting mechanics and damage mechanics, scholars have made significant progress in single-hole blasting damage analysis. Currently, research on the damage effects of surrounding rock in deep rock mass blasting excavation mainly considers the combined influence of blasting load and ground stress "inhibition," without considering the impact of transient ground stress unloading on surrounding rock damage. Therefore, when conducting single-hole blasting, the effects of blasting load, ground stress "inhibition," and transient ground stress unloading on surrounding rock damage should be comprehensively considered to reduce safety hazards during deep-buried tunnel blasting excavation.

[0003] However, deep-buried tunnel blasting excavation is typically a cyclical process, with each cycle employing millisecond-delay blasting, proceeding sequentially from the cut hole, auxiliary hole, and peripheral hole. This means that in most actual blasting projects, the degree of damage to the surrounding rock is affected by the repeated disturbance of blasting excavation, leading to cumulative damage zones within the rock mass. Therefore, analyzing the surrounding rock damage during single-hole blasting by comprehensively considering blasting load, ground stress "suppression," and transient ground stress unloading is insufficient and unsuitable for most actual blasting projects. It is necessary to analyze the cumulative damage to the surrounding rock during cyclic blasting excavation of deep-buried tunnels. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method and system for analyzing cumulative damage to surrounding rock during cyclic blasting excavation of deep-buried tunnels.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a method for analyzing the cumulative damage of surrounding rock during cyclic blasting excavation of deep-buried tunnels. The method includes the following steps: analyzing the change history of blasting load and transient unloading of ground stress to determine the effects of blasting and ground stress on the surrounding rock damage during deep-buried tunnel blasting excavation; considering the impact of single-cycle blasting excavation on the surrounding rock damage under the action of blasting and ground stress, calculating the cumulative damage variable of the surrounding rock mass during single-cycle blasting excavation; considering the impact of multi-cycle blasting excavation on the surrounding rock damage based on single-cycle blasting excavation, calculating the cumulative damage variable of the surrounding rock mass during multi-cycle blasting excavation; and evaluating the stability state of the surrounding rock of the deep-buried tunnel based on the calculated cumulative damage variable, thereby optimizing the blasting design scheme and support sequence. This method, considering the combined effects of blasting and ground stress, accurately calculates the cumulative damage to the surrounding rock during cyclic blasting excavation of deep-buried tunnels by analyzing the impact of single-cycle multi-stage borehole delayed blasting and multi-cycle blasting on the surrounding rock. This allows for the optimization of blasting design schemes and support sequence, thereby improving the safety of tunnel engineering.

[0006] Optionally, the analysis of the change history of blasting load and transient unloading of ground stress, and thus the determination of the effects of blasting and ground stress on the surrounding rock during deep-buried tunnel blasting excavation, includes the following steps: obtaining the blasting load intensification time, peak blasting load, and positive pressure duration, and thus determining the blasting load change history; estimating the magnitude, start time, and duration of transient unloading of ground stress, and thus determining the transient unloading change history of ground stress; and determining the effects of blasting and ground stress on the surrounding rock during deep-buried tunnel blasting excavation based on the blasting load change history and the transient unloading change history of ground stress.

[0007] Optionally, the step of considering the impact of single-cycle blasting excavation on the surrounding rock damage under the action of blasting and ground stress, and calculating the cumulative damage variable of the surrounding rock mass during single-cycle blasting excavation, includes the following steps: calculating the first damage variable of the surrounding rock mass of the deep-buried tunnel under the action of blasting and ground stress; based on the first damage variable, considering the impact of single-cycle blasting excavation on the surrounding rock damage, calculating the second damage variable caused by the blasting of each delayed-detonation blast hole; and using the second damage variable to calculate the first cumulative damage variable of the surrounding rock mass during single-cycle blasting excavation.

[0008] Optionally, the second damage variable satisfies the following relationship: in, The second damage variable is caused by the blasting of the i-th delayed detonation borehole; Let be the damage variable under the action of the explosion stress wave when the i-th delayed detonation blast hole is blasted; Let be the damage variable under the action of explosive gas when the i-th delayed detonation hole is blasted; , represents the damage variable under transient unloading of ground stress during the blasting of the i-th delayed detonation borehole; The dynamic Poisson's ratio; is the actual coefficient for the blasting of the i-th delayed detonation blast hole, which is a coefficient related to the tunnel cross-sectional shape and span; Let be the in-situ stress on the free surface of the blasting excavation of the i-th delayed-detonation blast hole; This is the proportionality coefficient under the action of explosive stress wave; The number of cracks caused by the explosive stress wave during the blasting of the i-th delayed detonation borehole. The crack half-length activated by the explosion stress wave during the blasting of the i-th delayed detonation borehole; For dynamic fracture toughness; The first cumulative damage variable after the (i-1)th delayed detonation hole blast; The distance between the centers of the delayed detonation holes of segment i-1 and segment i is denoted by ; Coefficients related to the environment and materials; The peak load on the borehole wall under the action of the explosion stress wave during the blasting of the i-th delayed detonation borehole; The radius of the borehole; The attenuation coefficient; The static Poisson's ratio; This is the proportionality coefficient under the action of explosive gases; and This is the adjustment coefficient; The number of cracks caused by the explosive gas during the detonation of the i-th delayed detonation borehole. The crack half-length activated by the explosive gas during the blasting of the i-th delayed detonation borehole; Static fracture toughness; The peak load on the borehole wall under the action of explosive gas during the blasting of the i-th delayed detonation borehole. is the proportionality coefficient under transient unloading of ground stress; r is the distance from the blast source; The crack half-length is activated by the transient unloading of ground stress during the blasting of the i-th delayed detonation borehole.

[0009] Optionally, the first cumulative damage variable satisfies the following relationship: in, Let be the first cumulative damage variable after the blasting of the i-th delayed-detonation blast hole. Let r be the first cumulative damage variable after the (i-1)th delayed detonation borehole blast, and r be the distance from the blast source. The distance between the centers of the delayed detonation holes of the (i-1)th segment and the i-th segment is [the distance between the centers of the holes]. Let be the variable representing the surrounding rock damage caused by the delayed detonation of the i-th blast hole.

[0010] Optionally, the step of considering the impact of multi-cycle blasting on the surrounding rock damage based on single-cycle blasting excavation and calculating the cumulative damage variable of the surrounding rock mass during multi-cycle blasting excavation includes the following steps: based on single-cycle blasting excavation and considering the impact of multi-cycle blasting on the surrounding rock damage, calculating the third damage variable caused by the delayed initiation blasting of each section of the tunnel face in different cycles of blasting; and using the third damage variable to calculate the second cumulative damage variable of the surrounding rock mass during multi-cycle blasting excavation.

[0011] Optionally, the third damage variable satisfies the following relationship: in, For the blasting of the i-th delayed-detonation blast hole on the face of the nth blasting cycle, the third damage variable is the result of the combined action of the explosion stress wave and the transient unloading of the ground stress on the surrounding rock in the first cycle. For the nth cycle blasting face, the cumulative damage variable is the explosion stress wave acting on the surrounding rock in the first cycle when the i-th delayed detonation hole is blasted. For the nth cycle blasting, the cumulative damage variable is the unloading stress wave on the excavated free surface acting on the surrounding rock in the first cycle when the i-th delayed detonation hole is blasted on the face of the tunnel. The dynamic Poisson's ratio; The correlation coefficient between the tunnel cross-sectional shape and span after the first cycle of blasting; This is the proportionality coefficient under the action of explosive stress wave; The number of cracks in the surrounding rock during the first cycle of blasting is the number of cracks in the first cycle of blasting under the action of the explosive stress wave when the i-th delayed detonation hole is blasted on the face of the n-th blasting cycle. The crack half-length activated by the explosive stress wave acting on the surrounding rock of the first cycle when the i-th delayed detonation hole on the face of the nth cycle blasting; For dynamic fracture toughness; The second cumulative damage variable is the effect of the explosion stress wave and the transient unloading of the ground stress on the surrounding rock of the first cycle after the blasting of the i-1th delayed detonation hole on the face of the nth blasting cycle. Coefficients related to the environment and materials; The load value is the stress wave propagating to the existing damage zone of the first cycle blast after the blasting of the i-th delayed detonation hole on the face of the nth blasting cycle. The intensity of the ground stress suppression effect in the existing damaged area during the nth cycle of blasting; The radius of the borehole; The attenuation coefficient; and This is the adjustment coefficient; The number of cracks in the surrounding rock during the first cycle of blasting is the number of delayed-detonation blast holes on the face of the nth blasting cycle under the transient unloading of ground stress. The load value is the stress wave propagating to the existing damage zone of the first cycle blast after the blasting of the i-th delayed detonation hole on the face of the nth blasting cycle. This is the proportionality coefficient under transient unloading of ground stress; The crack half-length is the crack activated by the unloading stress wave on the first cycle surrounding rock when the i-th delayed detonation hole on the face of the nth blasting cycle is blasted.

[0012] Optionally, the second cumulative damage variable satisfies the following relationship: in, The second cumulative damage variable is the effect of the explosive stress wave and transient unloading of the ground stress on the surrounding rock of the first cycle after the blasting of the i-th delayed detonation hole on the face of the nth blasting cycle. The second cumulative damage variable is the effect of the explosion stress wave and the transient unloading of the ground stress on the surrounding rock of the first cycle after the blasting of the i-1th delayed detonation hole on the face of the nth blasting cycle. The third damage variable refers to the blasting of the i-th delayed-detonation blast hole on the face of the nth blasting cycle, where the explosion stress wave and the transient unloading of the ground stress act together on the surrounding rock in the first cycle.

[0013] Optionally, the step of evaluating the stability state of the surrounding rock of the deep-buried tunnel based on the calculated cumulative damage variable, and then optimizing the blasting design scheme and support sequence, includes the following steps: based on the strain equivalence assumption, the mechanical parameters of the surrounding rock mass are reduced using the calculated cumulative damage variable, and then the surrounding rock safety factor is obtained based on the reduced mechanical parameters; based on the surrounding rock safety factor, the blasting parameters are optimized through numerical simulation methods, and then the blasting design scheme and support sequence are optimized.

[0014] Secondly, the present invention provides a system for analyzing the cumulative damage of surrounding rock in deep-buried tunnel cyclic blasting excavation. This system includes: a data acquisition device, a data output device, a processor, and a storage device. The storage device includes a computer-readable storage medium storing a computer program. The computer program includes program instructions, which, when executed by the processor, cause the processor to implement the method for analyzing the cumulative damage of surrounding rock in deep-buried tunnel cyclic blasting excavation provided by the present invention.

[0015] This method has the following beneficial effects: 1. Based on the combined effects of blasting and ground stress on the damage to the surrounding rock of deep-buried tunnels, the disturbance effect of cyclic blasting was further considered, enabling accurate calculation of the cumulative damage to the surrounding rock during cyclic blasting excavation of deep-buried tunnels, and further improving the accuracy of surrounding rock damage assessment.

[0016] 2. Based on the accurate calculation of the cumulative damage of the surrounding rock during cyclic blasting excavation of deep-buried tunnels, this method optimizes the blasting design scheme and support sequence according to the calculated cumulative damage variables, forming a dynamic closed-loop system that guides construction, ensures safety, and optimizes costs, thereby improving the safety of tunnel engineering.

[0017] 3. A system adapted to this method has been established. This system can run stably and not only improves the practicality of this method, but also facilitates its promotion. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart illustrating a method for analyzing cumulative damage to surrounding rock during cyclic blasting excavation of a deep-buried tunnel, according to an embodiment of the present invention. Figure 2 These are the blasting load variation history curves and the transient unloading variation history curves of ground stress in embodiments of the present invention; Figure 3 This is a schematic diagram illustrating the cumulative damage evolution process of porous delayed-blast rock mass according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the cumulative damage to the surrounding rock under single-cycle blasting conditions according to an embodiment of the present invention; Figure 5This is a schematic diagram of the cumulative damage of surrounding rock in multi-cycle blasting under in-situ stress conditions according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the framework of a system for analyzing the cumulative damage of surrounding rock in cyclic blasting excavation of deep-buried tunnels, according to an embodiment of the present invention. Detailed Implementation

[0020] Specific embodiments of the present invention will now be described in detail. It should be noted that the embodiments described herein are for illustrative purposes only and are not intended to limit the invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other instances, well-known circuits, software, or methods have not been specifically described to avoid obscuring the invention.

[0021] Throughout this specification, references to "an embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases "in an embodiment," "in an embodiment," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. Moreover, those skilled in the art will understand that the illustrations provided herein are for illustrative purposes and are not necessarily drawn to scale.

[0022] It should be noted in advance that, in one alternative embodiment, except for independent descriptions, the same symbols or letters appearing in all formulas have the same meaning and value.

[0023] In one optional embodiment, please refer to Figure 1 This invention provides a method for cumulative damage analysis of surrounding rock during cyclic blasting excavation of deep-buried tunnels, the method comprising the following steps: S1. Analyze the change process of blasting load and transient unloading of ground stress to determine the effect of blasting and ground stress on the surrounding rock damage during deep tunnel blasting excavation.

[0024] Step S1 specifically includes the following steps: S11. Obtain the blast load pressurization time, blast load peak value, and positive pressure action time to determine the blast load change history.

[0025] Specifically, in this embodiment, a trigonometric function or a double exponential function is used to describe the blast load variation history. The trigonometric function expression mainly includes three parameters: blast load inflation time, peak blast load, and barometric pressure duration. The blast load variation history curve is shown below. Figure 2 As shown, its mathematical expression is: in, This represents the change of blast load pressure P with time t.

[0026] For detonation processes and cylindrical charge structures under uncoupled charge conditions, the peak blast load satisfies the following relationship: in, This represents the peak value of the blasting load on the borehole wall. To increase the coefficient, it is generally taken as 8 to 11; The density of the explosive inside the borehole needs to be determined based on the actual type of explosive; VOD is the propagation speed of the detonation wave, which can be obtained by looking up a table based on the type of explosive or by measuring it through a blasting test. The isentropic exponent of the detonation products is typically taken as 3; The diameter of the explosive; The diameter of the borehole; The length of the explosive; This represents the length of the borehole.

[0027] The time for the blast load to build up pressure and the time for the barotropic action can be expressed by the rock volumetric compressibility modulus, the distance from the blast center, the borehole radius, the charge amount, and the Poisson's ratio of the rock. in, is the time for the blasting load to build up pressure; K is the volumetric compressibility modulus of rock, determined experimentally; Q is the charge amount; r is the distance from the blast center. The radius of the borehole; The Poisson's ratio for rocks needs to be determined based on the rock type, and is usually taken as 0.2 to 0.3; This refers to the duration of positive pressure application.

[0028] Furthermore, when the explosive detonates from the bottom of the hole, the detonation wave propagates along the explosive towards the hole opening. Because the detonation wave propagates very quickly, the load rise time for the entire process can be approximately equal to the detonation wave propagation time. Therefore, the blasting load pressurization time can be simplified to... , This refers to the length of the explosive charge inside the borehole.

[0029] S12. Estimate the magnitude, start time and duration of transient unloading of ground stress, and then determine the change process of transient unloading of ground stress.

[0030] Specifically, in this embodiment, for underground projects with significant burial depth, the geostress at their location is often substantial, and the rock mass is in a relatively stable state before excavation. When part of the rock mass is excavated, its stable state is disrupted, the initial stress of the rock mass is released into the excavated area, and the stress field is redistributed and adjusted. The transient unloading process of geostress can generally be described by the magnitude, start time, and duration of the transient unloading.

[0031] First, estimate the magnitude of the transient unloading of ground stress. Under plane strain and biaxial stress conditions, the stress distribution of the surrounding rock during tunnel blasting excavation can be calculated using the following relationship: in, The radial stress on the excavation boundary during the blasting of the i-th borehole is given. , Let be the circumferential stress on the excavation boundary during the blasting of the i-th borehole. Let be the shear stress on the excavation boundary during the blasting of the i-th borehole. Let be the radius of the excavation face formed by the blasting of the i-th blast hole. Let be the radius of the excavation face formed by the blasting of the (i-1)th blast hole. The stress in the original rock in the horizontal direction, This refers to the original rock stress in the vertical direction.

[0032] The magnitude of the transient unloading of ground stress on the excavation boundary during the blasting of the i-th borehole It can be estimated by the change in radial stress at the excavation boundary before and after blasting excavation, that is... , This refers to the radial stress on the excavation boundary before blasting.

[0033] Next, we estimate the start time and duration of the transient unloading of in-situ stress. The process of transient unloading of in-situ stress can be divided into two stages: 1. The initial steady-state stage: Before rock mass excavation, the stress constraint of the excavated rock mass on the surrounding rock can be regarded as applying a reverse load equal to the initial in-situ stress to the surrounding rock; 2. The excavation unloading stage: After the rock mass is removed, the reverse load rapidly decays to zero. In fact, during the rock mass blasting excavation process, when the main crack between the boreholes forms and the rock blocks detach from the original rock, the pressure within the cracks is still greater than the initial in-situ stress, and the stress constraint still exists. Only when the pressure of the explosive gas in the borehole decays to the level of the in-situ stress will the transient unloading phenomenon occur. When the pressure of the explosive gas in the borehole is the same as the atmospheric pressure, the blasting load process and the transient unloading of in-situ stress are completed simultaneously. In the process of transient unloading of in-situ stress, the attenuation of the blasting load is equal to the amount of in-situ stress removed at the tunnel excavation boundary. It can be seen that the process of transient unloading of in-situ stress is the same as the process of blasting load change after the start of unloading.

[0034] Therefore, the start time of transient unloading of ground stress is the moment when the blasting load decays to be equal to the ground stress at the excavation face, and the duration of transient unloading of ground stress is the difference between the termination time of the blasting load and the start time of transient unloading of ground stress. The duration of transient unloading of ground stress is estimated below by refining the blasting load and transient unloading process.

[0035] The process from the detonation of the explosive to the completion of the transient unloading of ground stress can be roughly divided into the following three stages: In the first stage, after the explosive detonates, the detonation wave propagates rapidly along the explosive, the blast load pressure inside the borehole increases rapidly, and the velocity generated in the surrounding rock of the borehole is... The stress wave caused the crack to initiate and continue to crack. The rate of propagation continues until the main crack between adjacent boreholes is completely connected. During this stage, as the detonation products continuously penetrate the crack, and the initial pressure of the detonation products far exceeds the in-situ stress in the surrounding rock of the borehole, the in-situ stress cannot be unloaded. However, the rate at which the detonation products penetrate the crack is lower than the crack propagation rate. Therefore, there will be partial release of in-situ stress in the local area of ​​the crack. However, compared with the entire process of transient unloading of in-situ stress, the stress unloading effect at this stage is negligible.

[0036] In the second stage, after the main crack is completed and the filler material is ejected, the high-pressure detonation products escape, generating a beam with a velocity of... Furthermore, the sparse wave propagates in the reverse direction, and the pressure inside the borehole gradually decreases. During this stage, although the blast load pressure inside the borehole decreases rapidly, its value is still higher than the magnitude of the ground stress, and the ground stress cannot be fully unloaded.

[0037] In the third stage, when the back-propagating rarefaction wave reaches the bottom of the aperture, it is reflected and... The velocity propagates along the borehole towards the orifice, further reducing the pressure inside the borehole until it reaches the same level as atmospheric pressure. During this stage, the pressure of the detonation products typically drops to the tens of megapascals level, and the ground stress begins to be fully unloaded. Once the blast load pressure has completely decayed, the transient unloading of the ground stress is also complete.

[0038] The timeframes encompassed in the three stages mentioned above include the time for the blast load to increase pressure, the time for the main crack to penetrate between holes, the time for the rarefaction wave to propagate from the borehole opening to the bottom of the hole, and the time for the rarefaction wave to propagate from the bottom of the hole to the opening. The time for the main crack to penetrate between holes, the time for the rarefaction wave to propagate from the borehole opening to the bottom of the hole, and the time for the rarefaction wave to propagate from the bottom of the hole to the opening can be calculated sequentially using the following formulas: in, S represents the time it takes for the main crack to penetrate between holes, and S represents the distance between holes. Let be the time it takes for a rarefaction wave to propagate from the orifice to the bottom of the orifice. This refers to the length of the explosive packing section. The time it takes for a rarefaction wave to propagate from the bottom of the hole to the opening is denoted as .

[0039] Based on the above analysis, the start time of transient unloading of ground stress is after the completion of the second stage and before the completion of the third stage, that is: Duration of transient unloading of ground stress It can be represented as: .

[0040] In summary, the transient unloading history of ground stress satisfies the following relationship: in, Transient unloading pressure of ground stress The process of change with time t This represents the start time of the transient unloading of ground stress. , The stopping time of transient unloading of ground stress. This refers to the duration of positive pressure application.

[0041] The final obtained transient unloading history curve of in-situ stress is as follows: Figure 2 As shown. From Figure 2 It is not difficult to see that when using the drill-and-blast method for deep rock excavation, both the blasting load and the transient unloading of ground stress will affect the damage to the surrounding rock, only the duration of their effects differs.

[0042] S13. Determine the effects of blasting and ground stress on the surrounding rock damage during deep-buried tunnel blasting excavation based on the blasting load change history and the transient unloading change history of ground stress.

[0043] Specifically, in this embodiment, the analysis in steps S11 and S12 shows that the damage to the surrounding rock caused by blasting excavation is the result of the coupling effect of blasting load and transient unloading of ground stress. Therefore, when blasting excavation of rock under ground stress conditions, it is necessary to consider the effects of blasting stress waves, explosive gases, and transient unloading of ground stress simultaneously. All three effects will cause varying degrees of damage to the rock mass, but with slight differences in the duration of their effects. In other words, when performing cumulative damage analysis on the surrounding rock of deep-buried tunnel cyclic blasting excavation under ground stress conditions, the effects of blasting and ground stress must be considered simultaneously.

[0044] S2. Under the influence of blasting and ground stress, consider the impact of single-cycle blasting excavation on the damage of the surrounding rock, and calculate the cumulative damage variable of the surrounding rock mass during single-cycle blasting excavation.

[0045] Step S2 specifically includes the following steps: S21. Calculate the first damage variable of the surrounding rock mass of a deep-buried tunnel under the action of blasting and ground stress.

[0046] Specifically, in this embodiment, deep rock masses generally have good integrity and relatively uniform structure. Therefore, the rock mass can be considered as a linear elastic body with uniformly and randomly distributed microcracks within it. According to the theory of micromechanical damage, the rock mass damage variable D can be defined as: in, This represents the elastic modulus of the rock mass after being subjected to load. Let N be the initial elastic modulus of the rock mass, and N be the number of cracks per unit volume of rock mass. The crack is half its length.

[0047] Without considering geostress conditions, the crack half-length can be determined based on the stress intensity factor at the crack tip. To calculate. When Not greater than the fracture toughness of the rock mass At that time, the crack stops cracking. Therefore, it is generally considered that... As the critical value for solving the crack half-length, that is: Where Y is the shape factor; The nominal stress is equal to the peak stress at the crack tip, i.e., the stress at the distance from the hole wall. The peak stress at the location. For borehole blasting, the nominal stress satisfies... , This represents the peak load on the borehole wall. For proportional distance, This is the attenuation coefficient. For relatively intact rock masses, For rock masses containing fractures, The value is not less than 2.

[0048] Finally, without considering geostress, the crack half-length can be solved using the following formula: Assuming the crack half-length is L without considering geostress conditions, increasing geostress... At this time, due to the "inhibition" effect of geostress, the crack half-length will shorten to Furthermore, under the same fracture toughness and peak borehole wall load, the greater the in-situ stress, the shorter the crack half-length, meaning the crack half-length is inversely proportional to the in-situ stress. Therefore, when considering in-situ stress for single-hole blasting, referring to the wedge-shaped crack propagation mechanical model, the peak stress at the crack tip is... Therefore, the relationship for solving the crack half-length under in-situ stress can be obtained, namely: When cracks generated by rock blasting are under bidirectional pressure (horizontal and vertical), their crack propagation model is as follows: Figure 5 As shown. At this point, the in-situ stress at the crack can be expressed as: , The first principal stress, i.e. and The larger one; The third principal stress, i.e. and The smaller one; The angle between the crack and the maximum principal stress. and It can be measured at the blasting site. For situations where the actual stress field cannot be obtained experimentally, it can be determined based on... To obtain, h is the burial depth.

[0049] The number of cracks is directly proportional to the peak load on the borehole wall, that is: Where k is the proportionality coefficient.

[0050] Due to the influence of ground stress, the number of cracks developed in the rock mass after blasting will decrease. The number of cracks is inversely proportional to the ground stress, that is: Finally, the rock mass damage variable considering the "inhibition" effect of geostress can be solved using the following relationship: Rock mass blasting damage under in-situ stress conditions is caused by the combined effects of the dynamic action of the blast stress wave, the quasi-static action of the blasting gas, and the quasi-dynamic action of the transient unloading of in-situ stress. However, the contributions of these three factors differ at different stages of the action; in reality, their effects are coupled. When multiple effects jointly cause rock mass damage, the rock mass damage variables under each individual action can be derived first, and then the first damage variable under the coupled action can be obtained using the following formula: in, As the first damage variable, The damage variable under the action of explosive stress wave, The damage variable under the action of explosive gases This represents the damage variable under transient unloading of ground stress.

[0051] In the case of single-hole blasting, based on the rock mass damage variable under the "inhibition" effect of in-situ stress, the damage variable under the dynamic action of the blast stress wave satisfies the following relationship: in, For dynamic Poisson's ratio, This is the proportionality coefficient under the dynamic action of the explosion stress wave. The number of cracks under the action of explosive stress wave. , The crack half-length activated by the explosion stress wave, For dynamic fracture toughness, The peak load on the borehole wall under the dynamic action of the explosion stress wave. , This is the adjustment coefficient.

[0052] After the rock mass is subjected to the dynamic action of the explosive stress wave, initial cracks are generated inside. The explosive gas expands and enters the initial cracks, causing them to propagate further. Assuming the explosive gas instantaneously enters the crack and is uniformly distributed along its length, the explosive gas begins to exert its quasi-static effect. In the case of single-hole blasting, based on the rock mass damage variables under the "inhibition" effect of in-situ stress, the damage variables under the quasi-static action of the explosive gas satisfy the following relationship: in, The static Poisson's ratio, This is the proportionality coefficient under quasi-static action of explosive gas. For adjustment coefficients, The number of cracks caused by explosive gases. , For crack half-length activated by explosive gases, For static fracture toughness, Let be the peak load on the borehole wall under quasi-static action of the explosive gas. Assuming the expansion process of the detonation products is an isentropic adiabatic expansion process, then according to the adiabatic instantaneous detonation theory, the peak load on the borehole wall under quasi-static action of the explosive gas satisfies... , For the volume of the explosive, The volume of the borehole; This refers to the critical pressure of the explosive. Let be the isentropic exponent of the gas, taken as 1.4. According to CJ theory, the critical pressure of the explosive... According to To calculate, , These are the specific volumes of the detonation products at the detonation wave front and the so-called conjugate point, respectively. The explosive is heated.

[0053] Based on the elastic unloading assumption, when the in-situ stress in the rock mass is transiently unloaded, it will generate elastic stress waves within the rock mass and propagate outwards. These unloading stress waves will also cause damage to the rock mass. The peak value of the transient unloading stress is equal to the magnitude of the in-situ stress at the excavation boundary, i.e. In the case of single-hole blasting, based on the rock mass damage variables under the "inhibition" effect of in-situ stress, the damage variables under the quasi-dynamic action of transient unloading of in-situ stress satisfy the following relationship: in, This is the proportionality coefficient under quasi-dynamic action of transient unloading of ground stress. The peak load on the borehole wall under quasi-dynamic action of transient unloading of ground stress. The crack half-length is activated by transient unloading of ground stress.

[0054] S22. Based on the first damage variable, considering the impact of single-cycle blasting excavation on the surrounding rock damage, calculate the second damage variable caused by the delayed initiation blasting of each section of the blast hole.

[0055] Specifically, in this embodiment, deep-buried tunnel blasting excavation is typically a cyclic process, with each excavation cycle employing millisecond-delay blasting rather than simple single-hole blasting. That is, in most actual blasting projects, the degree of damage to the surrounding rock of the tunnel is affected by the repeated disturbance of blasting excavation, which leads to cumulative damage within the rock mass. To simplify the analysis, the outermost boundaries of the blast damage zones of each borehole in the same section can be connected to form an envelope, which represents the boundary of the blast damage zone for that section. Figure 3 As shown. Furthermore, for ease of understanding, Figure 3 The map also shows the boundary of the single-hole blasting damage zone, the excavation free face, existing damage, and cumulative damage.

[0056] Furthermore, in Figure 3 Based on this, please refer to Figure 4 ,Depend on Figure 4 It is known that the blast holes at the excavation face are detonated with a delayed time from the inside out. Each blast hole creates a free excavation face and causes damage within the rock mass to a certain extent. This means that before the outer blast holes are blasted, the rock mass has already suffered some damage under the blast load of the inner blast holes and the transient unloading of ground stress. Therefore, the degree of damage caused by the outer blast holes will be increased due to the influence of the existing damage.

[0057] The damage to the surrounding rock caused by single-cycle blasting can be considered as a result of staged delayed blasting. According to damage mechanics, for rock masses already damaged by blasting excavation disturbance, their fracture toughness... It can be represented as: in, The degree of damage to the surrounding rock. The coefficients are related to the environment and materials.

[0058] When a damaged rock mass is subjected to blasting load again, the crack half-length can be calculated using the following formula: Based on the above analysis, the following will comprehensively consider the influence of in-situ stress and the cumulative damage effect of the surrounding rock in a single-cycle blasting, and will separately address... , and The calculation formula was modified to obtain the second damage variable caused by the detonation of each delayed-detonation borehole. Meanwhile, for ease of description, the calculation... , and The calculation formulas are denoted as the first relation, the second relation, and the third relation, respectively.

[0059] For single-cycle blasting, the rock mass damage caused by the explosive stress wave during the first delayed-detonation borehole blast can be calculated using the first formula. Starting from the second delayed-detonation borehole, the fracture toughness of the rock mass decreases due to the preceding blasts; therefore, it is necessary to calculate the rock mass damage based on... The calculation formula for the first relation is... Furthermore, for non-circular tunnel blasting excavation, the damage range of the surrounding rock exhibits a non-uniform distribution due to the influence of the tunnel shape and size. To reduce theoretical calculation errors, this embodiment introduces a coefficient related to the tunnel cross-sectional shape and span. Therefore, when the i-th delayed-detonation blast hole is detonated, the cumulative damage variable of the surrounding rock under the dynamic action of the explosion stress wave can be expressed as: in, Let be the damage variable under the action of the explosion stress wave when the i-th delayed detonation blast hole is blasted; is the actual coefficient for the blasting of the i-th delayed detonation blast hole, which is a coefficient related to the tunnel cross-sectional shape and span; This represents the number of cracks caused by the blast stress wave during the blasting of the i-th delayed-detonation borehole. ; The crack half-length activated by the explosion stress wave during the blasting of the i-th delayed detonation borehole; For dynamic fracture toughness; The first cumulative damage variable after the (i-1)th delayed detonation hole blast; The distance between the centers of the delayed detonation holes of segment i-1 and segment i is denoted by ; The peak load on the borehole wall under the action of the blast stress wave during the blasting of the i-th delayed-detonation borehole is calculated using the method described above. The calculation method.

[0060] Due to the ground stress on the free surface of the i-th delayed detonation blast hole excavation. It is difficult to measure through field tests. It can be calculated based on the original rock stress, using numerical simulation or according to the calculation method of surrounding rock stress distribution given in step S12.

[0061] refer to The derivation process yields the following formulas for calculating the cumulative damage of the surrounding rock under the action of explosive gas and the action of transient unloading of ground stress during the blasting of the i-th delayed detonation hole: in, Let be the number of cracks caused by the explosive gas during the blasting of the i-th delayed-detonation borehole. ; The crack half-length activated by the explosive gas during the blasting of the i-th delayed detonation borehole; Static fracture toughness; The peak load on the borehole wall under the action of explosive gas during the blasting of the i-th delayed-detonation borehole is calculated using the method described above. The calculation method; The crack half-length is activated by the transient unloading of ground stress during the blasting of the i-th delayed detonation borehole.

[0062] Finally, the second damage variable caused by the blasting of the i-th delayed detonation borehole can be expressed by the following formula: S23. Use the second damage variable to calculate the first cumulative damage variable of the surrounding rock mass during single-cycle blasting excavation.

[0063] Specifically, in this embodiment, the first cumulative damage variable under multi-cycle blasting conditions under in-situ stress conditions satisfies the following relationship: in, Let be the first cumulative damage variable after the blasting of the i-th delayed detonation borehole.

[0064] S3. Based on single-cycle blasting excavation, considering the impact of multi-cycle blasting excavation on the surrounding rock damage, calculate the cumulative damage variable of the surrounding rock mass during multi-cycle blasting excavation.

[0065] Step S3 specifically includes the following steps: S31. Based on single-cycle blasting excavation, considering the impact of multi-cycle blasting excavation on the surrounding rock damage, calculate the third damage variable caused by the delayed initiation blasting of each section of the tunnel face in different cycles of blasting.

[0066] Specifically, in this embodiment, unlike the cumulative damage to the surrounding rock caused by single-cycle blasting, the expansion and evolution of the existing damaged area in the surrounding rock during multi-cycle blasting excavation can be seen as secondary damage to the existing damaged area caused by the transmission of the explosive stress wave generated by the delayed initiation blasting of the blast holes in subsequent cycles and the unloading stress wave excited by the transient unloading of ground stress to the existing damaged area. The evolution process of cumulative damage to the surrounding rock under ground stress conditions in multi-cycle blasting is as follows: Figure 5 As shown.

[0067] Because multi-cycle blasting excavation has a long operation cycle, the stress redistribution process increases the damage to the surrounding rock. However, in actual construction, the surrounding rock is supported promptly after each blast, suppressing the damage effect caused by stress redistribution. For the sake of simplicity, the damage caused by stress redistribution is not considered. Furthermore, the effect of explosive gases has almost no influence on the evolution of existing damaged zones; therefore, the effect of explosive gases can also be ignored.

[0068] The transient unloading effect of in-situ stress creates a stress unloading zone within the excavated surrounding rock. The in-situ stress within this unloading zone is weakened to some extent, and due to the stress redistribution time effect, the stress suppression effect weakens in the short term. As the stress within the surrounding rock returns to equilibrium, the stress suppression effect gradually recovers and stabilizes. Therefore, the intensity of the stress suppression effect can be expressed as: in, The intensity of the ground stress suppression effect in the existing damaged area during the nth cycle of blasting; It is the attenuation coefficient for the nth blasting cycle with a single-cycle operation period of t.

[0069] In summary, when conducting cumulative damage variable analysis of surrounding rock in multi-cycle blasting excavation, it is necessary to comprehensively consider the effects of ground stress suppression, the explosive stress wave generated by delayed initiation of blast holes in each subsequent cycle, and the unloading stress wave generated by the transient unloading of ground stress on each excavation surface in subsequent cycles.

[0070] After the first cycle of blasting, damage is formed within a certain range inside the surrounding rock, and its distribution can be determined according to the relationship provided in step S23. Starting from the second cycle of blasting, after each delayed-detonation borehole is blasted, when the explosive stress wave propagates to the existing damage zone from the first cycle of blasting, the peak blast load has already attenuated, specifically as follows: in, The load value is the stress wave propagating to the existing damage zone of the first cycle blast after the blasting of the i-th delayed detonation hole on the face of the nth blasting cycle. The peak load on the borehole wall under the action of the blast stress wave during the blasting of the i-th delayed-detonation blast hole on the face of the nth blasting cycle is calculated using the method described above. The calculation method; is the distance from the center connection line of the i-th delayed detonation blast hole to the tunnel excavation outline; This refers to the length of a single advance.

[0071] Based on the above analysis, combined with The calculation formula can be derived from which the calculation formula for the cumulative damage of surrounding rock under the action of explosive stress wave during multi-cycle blasting excavation is: in, For the nth cycle blasting face, the cumulative damage variable is the explosion stress wave acting on the surrounding rock in the first cycle when the i-th delayed detonation hole is blasted. The correlation coefficient between the tunnel cross-sectional shape and span after the first cycle of blasting; Let be the number of cracks in the surrounding rock during the first cycle of blasting, under the action of the blast stress wave during the blasting of the i-th delayed-detonation blast hole on the working face. ; The crack half-length activated by the explosive stress wave acting on the surrounding rock of the first cycle when the i-th delayed detonation hole on the face of the nth cycle blasting; The second cumulative damage variable is the effect of the explosive stress wave and transient unloading of the ground stress on the surrounding rock in the first cycle after the blasting of the (i-1)th delayed detonation hole on the face of the nth blasting cycle.

[0072] The load value when the unloading stress wave propagates to the existing damage zone of the first cycle blast after the blasting of the i-th delayed detonation hole on the face of the nth blasting cycle. It can be represented as: in, The stress on the free surface of the excavation after the blasting of the i-th delayed-detonation blast hole on the face of the nth blasting cycle is denoted as .

[0073] Reference The calculation formula, combined with and The calculation formula can be derived from which the calculation formula for the cumulative damage of surrounding rock under transient unloading of ground stress during multi-cycle blasting excavation is: in, For the nth cycle blasting, the cumulative damage variable is the unloading stress wave on the excavated free surface acting on the surrounding rock in the first cycle when the i-th delayed detonation hole is blasted on the face of the tunnel. This is the adjustment coefficient; The number of cracks in the surrounding rock during the first cycle of blasting, under the transient unloading of ground stress, represents the number of cracks in the i-th delayed-detonation blast hole on the face of the n-th blasting cycle. ; The load value is the stress wave propagating to the existing damage zone of the first cycle blast after the blasting of the i-th delayed detonation hole on the face of the nth blasting cycle. The crack half-length is the crack activated by the unloading stress wave on the first cycle surrounding rock when the i-th delayed detonation hole on the face of the nth blasting cycle is blasted.

[0074] Furthermore, in the nth cycle of blasting, the blasting of the i-th delayed-detonation blast hole on the working face results in the third damage variable acting on the surrounding rock in the first cycle, due to the combined effect of the blast stress wave and the transient unloading of ground stress. This can be expressed using the following relation: S32. Calculate the second cumulative damage variable of the surrounding rock mass during multi-cycle blasting excavation using the third damage variable.

[0075] Specifically, in this embodiment, the second cumulative damage variable of the surrounding rock mass under multi-cycle blasting excavation under in-situ stress conditions can be expressed as: in, This is the second cumulative damage variable on the surrounding rock of the first cycle, which is the result of the transient unloading of the explosive stress wave and ground stress after the blasting of the i-th delayed detonation hole on the face of the n-th blasting cycle.

[0076] S4. Evaluate the stability of the surrounding rock of the deep-buried tunnel based on the calculated cumulative damage variables, and then optimize the blasting design scheme and support sequence.

[0077] Step S4 specifically includes the following steps: S41. Based on the strain equivalence assumption, the mechanical parameters of the surrounding rock mass are reduced using the calculated cumulative damage variable, and then the safety factor of the surrounding rock is obtained based on the reduced mechanical parameters.

[0078] Specifically, in this embodiment, the mechanical parameters of the surrounding rock mass include the internal friction angle and cohesion. Based on the strain equivalence assumption, that is, the strain of the damaged material under nominal stress is equivalent to the strain of the undamaged material under effective stress, the mechanical parameters of the surrounding rock mass can be reduced using the following relationship: in, The cumulative damage variables include the first cumulative damage variable and the second cumulative damage variable. This is the reduced internal friction angle. The initial internal friction angle, The reduced cohesion. This represents the initial cohesive force.

[0079] The cumulative damage variable at different locations on the rock mass was calculated by adjusting the distance r from the burst center, and the corresponding damage was then analyzed. and After reduction, we get and Then, a numerical model of the tunnel was constructed using FLAC3D software. In this model, the Mohr-Coulomb model was used as the constitutive model, and the calculated reduced internal friction angle and cohesion at each location were used as input parameters and substituted into the numerical model. Finally, based on the strength reduction method, the safety factor FoS at different locations of the surrounding rock was calculated. For any location, when... At that time, the surrounding rock was considered stable. At that time, the surrounding rock is in a basically stable or unstable state, requiring close monitoring. At that time, it was believed that the surrounding rock was unstable and the current support design was insufficient, requiring reinforcement.

[0080] S42. Based on the surrounding rock safety factor, optimize the blasting parameters through numerical simulation, and then optimize the blasting design scheme and support sequence.

[0081] Specifically, in this embodiment, blasting parameters such as explosive diameter, borehole diameter, explosive length, borehole length, and borehole radius are adjusted to obtain multiple different blasting schemes. For each blasting scheme, the corresponding cumulative damage variable is obtained, and the mechanical parameters of the surrounding rock mass are reduced. The reduced mechanical parameters are then substituted into the numerical model, and the safety factor FoS at different locations of the surrounding rock under different blasting schemes is obtained based on the strength reduction method.

[0082] Furthermore, based on the numerical simulation results, blasting schemes that can meet the preset blasting requirements are selected as candidate blasting schemes, and the maximum safety factor of each candidate blasting scheme is obtained. The candidate blasting scheme with the smallest maximum safety factor is selected as the preferred blasting scheme, and its corresponding blasting parameters are the preferred blasting parameters.

[0083] The safety factors of different locations in the surrounding rock under the preferred blasting scheme are arranged in descending order. The order of these safety factors is the support sequence of different locations in the surrounding rock under the preferred blasting scheme, that is, locations with larger safety factors need to be supported first.

[0084] It should be noted that in some cases, the actions described in the specification can be performed in different orders and still achieve the desired results. In this embodiment, the order of steps is given only to make the embodiment clearer and easier to explain, and not to limit it.

[0085] In one optional embodiment, please refer to Figure 6 To improve the practicality and facilitate the promotion of this method, the present invention also provides a system for analyzing the cumulative damage of surrounding rock in deep-buried tunnel cyclic blasting excavation. This system includes: a data acquisition device 1, a data output device 2, a processor 3, and a storage device 4. The storage device 4 includes a computer-readable storage medium storing a computer program. The computer program includes program instructions, which, when executed by the processor 3, cause the processor 3 to perform the contents described in steps S1 to S4.

[0086] In summary, this method has at least the following beneficial effects: Firstly, considering the combined effects of blasting and ground stress on the damage to the surrounding rock of deeply buried tunnels, it further considers the disturbance effect of cyclic blasting, achieving accurate calculation of the cumulative damage to the surrounding rock during cyclic blasting excavation of deeply buried tunnels, thus further improving the accuracy of surrounding rock damage assessment. Secondly, based on the accurate calculation of the cumulative damage to the surrounding rock during cyclic blasting excavation of deeply buried tunnels, this method optimizes the blasting design scheme and support sequence according to the calculated cumulative damage variables, forming a dynamic closed-loop system that guides construction, ensures safety, and optimizes costs, thereby improving the safety of tunnel engineering. Thirdly, a system adapted to this method has been established, which can operate stably, not only improving the practicality of this method but also facilitating its promotion.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for analyzing cumulative damage to surrounding rock during cyclic blasting excavation of deep-buried tunnels, characterized in that, Includes the following steps: The changes in blasting load and transient unloading of ground stress were analyzed to determine the effects of blasting and ground stress on the surrounding rock damage during deep tunnel blasting excavation. Under the action of blasting and ground stress, the influence of single-cycle blasting excavation on the damage of surrounding rock is considered, and the cumulative damage variable of surrounding rock mass during single-cycle blasting excavation is calculated. Based on single-cycle blasting excavation, the impact of multi-cycle blasting excavation on the surrounding rock damage is considered, and the cumulative damage variable of the surrounding rock mass during multi-cycle blasting excavation is calculated. The stability of the surrounding rock of the deep-buried tunnel is evaluated based on the calculated cumulative damage variables, thereby optimizing the blasting design scheme and support sequence.

2. The method for cumulative damage analysis of surrounding rock during cyclic blasting excavation of deep-buried tunnels according to claim 1, characterized in that, The analysis of the transient unloading history of blasting load and ground stress, and the determination of the effects of blasting and ground stress on the surrounding rock damage during deep tunnel blasting excavation, includes the following steps: The blast load pressurization time, peak blast load, and positive pressure duration are obtained to determine the blast load change history. The magnitude, start time, and duration of transient unloading of ground stress are estimated, thereby determining the history of transient unloading of ground stress. The effects of blasting and ground stress on the surrounding rock damage during deep-buried tunnel blasting excavation are determined based on the blasting load change history and the transient unloading change history of ground stress.

3. The method for cumulative damage analysis of surrounding rock during cyclic blasting excavation of deep-buried tunnels according to claim 1, characterized in that, The process of calculating the cumulative damage variable of the surrounding rock mass under the action of blasting and ground stress, considering the impact of single-cycle blasting excavation on the surrounding rock damage, includes the following steps: Calculate the first damage variable of the surrounding rock mass of a deep-buried tunnel under the action of blasting and in-situ stress; Based on the first damage variable, the impact of single-cycle blasting excavation on the surrounding rock damage is considered, and the second damage variable caused by the delayed initiation blasting of each section of the blast hole is calculated. The second damage variable is used to calculate the first cumulative damage variable of the surrounding rock mass during single-cycle blasting excavation.

4. The method for cumulative damage analysis of surrounding rock during cyclic blasting excavation of deep-buried tunnels according to claim 3, characterized in that, The second damage variable satisfies the following relationship: in, The second damage variable is caused by the blasting of the i-th delayed detonation borehole; Let be the damage variable under the action of the explosion stress wave when the i-th delayed detonation blast hole is blasted; Let be the damage variable under the action of explosive gas when the i-th delayed detonation hole is blasted; , represents the damage variable under transient unloading of ground stress during the blasting of the i-th delayed detonation borehole; For dynamic Poisson's ratio; is the actual coefficient for the blasting of the i-th delayed detonation blast hole, which is a coefficient related to the tunnel cross-sectional shape and span; Let be the in-situ stress on the free surface of the blasting excavation of the i-th delayed-detonation blast hole; This is the proportionality coefficient under the action of explosive stress wave; The number of cracks caused by the explosive stress wave during the blasting of the i-th delayed detonation borehole. The crack half-length activated by the explosion stress wave during the blasting of the i-th delayed detonation borehole; For dynamic fracture toughness; The first cumulative damage variable after the (i-1)th delayed detonation hole blast; The distance between the centers of the delayed detonation holes of segment i-1 and segment i is denoted by ; Coefficients related to the environment and materials; The peak load on the borehole wall under the action of the explosion stress wave during the blasting of the i-th delayed detonation borehole; The radius of the borehole; The attenuation coefficient; The static Poisson's ratio; This is the proportionality coefficient under the action of explosive gases; and This is the adjustment coefficient; The number of cracks caused by the explosive gas during the detonation of the i-th delayed detonation borehole. The crack half-length activated by the explosive gas during the blasting of the i-th delayed detonation borehole; Static fracture toughness; The peak load on the borehole wall under the action of explosive gas during the blasting of the i-th delayed detonation borehole. is the proportionality coefficient under transient unloading of ground stress; r is the distance from the blast source; The crack half-length is activated by the transient unloading of ground stress during the blasting of the i-th delayed detonation borehole.

5. The method for cumulative damage analysis of surrounding rock during cyclic blasting excavation of deep-buried tunnels according to claim 4, characterized in that, The first cumulative damage variable satisfies the following relationship: in, Let be the first cumulative damage variable after the blasting of the i-th delayed detonation borehole. Let r be the first cumulative damage variable after the (i-1)th delayed detonation borehole blast, and r be the distance from the blast source. The distance between the centers of the delayed detonation holes of the (i-1)th segment and the i-th segment is [the distance between the centers of the holes]. Let be the variable representing the surrounding rock damage caused by the delayed detonation of the i-th blast hole.

6. The method for cumulative damage analysis of surrounding rock during cyclic blasting excavation of deep-buried tunnels according to claim 1, characterized in that, The method for calculating the cumulative damage variable of the surrounding rock mass during multi-cycle blasting excavation, based on single-cycle blasting excavation and considering the impact of multi-cycle blasting excavation on the surrounding rock, includes the following steps: Based on single-cycle blasting excavation, considering the impact of multi-cycle blasting excavation on the surrounding rock damage, the third damage variable caused by the delayed initiation blasting of each section of the tunnel face in different cycles of blasting is calculated. The third damage variable is used to calculate the second cumulative damage variable of the surrounding rock mass during multi-cycle blasting excavation.

7. The method for cumulative damage analysis of surrounding rock in cyclic blasting excavation of deep-buried tunnels according to claim 6, characterized in that, The third damage variable satisfies the following relationship: in, For the blasting of the i-th delayed-detonation blast hole on the face of the nth blasting cycle, the third damage variable is the result of the combined action of the explosion stress wave and the transient unloading of the ground stress on the surrounding rock in the first cycle. For the nth cycle blasting face, the cumulative damage variable is the explosion stress wave acting on the surrounding rock in the first cycle when the i-th delayed detonation hole is blasted. For the nth cycle blasting, the cumulative damage variable is the unloading stress wave on the excavated free surface acting on the surrounding rock in the first cycle when the i-th delayed detonation hole is blasted on the face of the tunnel. For dynamic Poisson's ratio; The correlation coefficient between the tunnel cross-sectional shape and span after the first cycle of blasting; This is the proportionality coefficient under the action of explosive stress wave; The number of cracks in the surrounding rock during the first cycle of blasting is the number of cracks in the first cycle of blasting when the i-th delayed detonation hole is blasted on the face of the n-th blasting cycle under the action of the explosion stress wave. The crack half-length activated by the explosive stress wave acting on the surrounding rock of the first cycle when the i-th delayed detonation hole on the face of the nth cycle blasting; For dynamic fracture toughness; The second cumulative damage variable is the effect of the explosion stress wave and the transient unloading of the ground stress on the surrounding rock of the first cycle after the blasting of the i-1th delayed detonation hole on the face of the nth blasting cycle. Coefficients related to the environment and materials; The load value is the stress wave propagating to the existing damage zone of the first cycle blast after the blasting of the i-th delayed detonation hole on the face of the nth blasting cycle. The intensity of the ground stress suppression effect in the existing damaged area during the nth cycle of blasting; The radius of the borehole; The attenuation coefficient; and This is the adjustment coefficient; The number of cracks in the surrounding rock during the first cycle of blasting is the number of delayed-detonation blast holes on the face of the nth blasting cycle under the transient unloading of ground stress. The load value is the stress wave propagating to the existing damage zone of the first cycle blast after the blasting of the i-th delayed detonation hole on the face of the nth blasting cycle. This is the proportionality coefficient under transient unloading of ground stress; The crack half-length is the crack activated by the unloading stress wave on the first cycle surrounding rock when the i-th delayed detonation hole on the face of the nth blasting cycle is blasted.

8. The method for cumulative damage analysis of surrounding rock during cyclic blasting excavation of deep-buried tunnels according to claim 7, characterized in that, The second cumulative damage variable satisfies the following relationship: in, The second cumulative damage variable is the effect of the explosive stress wave and transient unloading of the ground stress on the surrounding rock of the first cycle after the blasting of the i-th delayed detonation hole on the face of the nth blasting cycle. The second cumulative damage variable is the effect of the explosion stress wave and the transient unloading of the ground stress on the surrounding rock of the first cycle after the blasting of the i-1th delayed detonation hole on the face of the nth blasting cycle. The third damage variable refers to the blasting of the i-th delayed-detonation blast hole on the face of the nth blasting cycle, where the explosion stress wave and the transient unloading of the ground stress act together on the surrounding rock in the first cycle.

9. The method for cumulative damage analysis of surrounding rock during cyclic blasting excavation of deep-buried tunnels according to claim 1, characterized in that, The process of evaluating the stability of the surrounding rock of the deep-buried tunnel based on the calculated cumulative damage variables, and then optimizing the blasting design scheme and support sequence, includes the following steps: Based on the strain equivalence assumption, the mechanical parameters of the surrounding rock mass are reduced using the calculated cumulative damage variable, and then the safety factor of the surrounding rock is obtained based on the reduced mechanical parameters. Based on the surrounding rock safety factor, blasting parameters are optimized through numerical simulation, thereby optimizing the blasting design scheme and support sequence.

10. A system for analyzing cumulative damage to surrounding rock during cyclic blasting excavation of deep-buried tunnels, characterized in that, The system for analyzing cumulative damage to surrounding rock during cyclic blasting excavation of deep-buried tunnels includes: a data acquisition device, a data output device, a processor, and a storage device. The storage device includes a computer-readable storage medium storing a computer program. The computer program includes program instructions, which, when executed by the processor, cause the processor to implement the method for analyzing cumulative damage to surrounding rock during cyclic blasting excavation of deep-buried tunnels as described in any one of claims 1-9.

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