Karst tunnel drilling and blasting parameter dynamic adjustment construction method

Abstract

The application discloses a kind of karst tunnel drilling and blasting parameter dynamic adjustment construction methods, comprising: using advanced geology forecast to detect the geological condition in front of the face, obtain the surrounding rock parameters and cave position in the effective detection depth in front of the face;According to the obtained surrounding rock parameters and cave position, determine the cave influence area, and preset the blasting parameter, and carry out trial blasting to the surrounding rock in front of the face;By three-dimensional laser scanning technology, obtain the contour line after blasting construction, dynamically adjust the blasting parameter of influence area according to the blasting effect, carry out trial blasting again, finally determine the blasting parameter.The method effectively reduces the overbreak and underbreak phenomenon, saves a large amount of concrete material, improves the construction progress and efficiency, solves the serious overbreak and underbreak technical problem caused by cave and other adverse geology to blasting.At the same time, the disturbance of blasting to surrounding rock is reduced, and the ecological environment of excavation area is effectively protected, which has obvious economic benefit and social benefit.

Description

Technical Field

[0001] This invention relates to the field of tunnel blasting construction technology, specifically to a method for dynamically adjusting drilling and blasting parameters in karst tunnels. Background Technology

[0002] Drill-and-blast excavation remains the primary method for tunnel excavation in my country. While manual drilling and blasting offer advantages such as ease of operation and low cost, in karst regions, blasting vibrations can cause the tunnel to connect with karst caves, leading to geological disasters such as water inrush, mudslides, and collapses. Furthermore, in karst areas, blasting can not only cause these geological disasters but also negatively impact the blasting effect. The presence of karst caves may reduce the explosive power and affect the size of blasted rock fragments, increasing the difficulty of muck removal. Additionally, blasting in karst areas can cause irreversible damage to the surrounding rock. Moreover, the presence of karst caves may alter the size and direction of the design resist line, leading to blasting blasts, flyrock, and over- or under-excavation of the tunnel, affecting the stability of the surrounding rock, reducing the tunnel's operational lifespan, and creating serious safety hazards.

[0003] Southern my country is rich in karst geology, and during the blasting excavation of karst tunnels, it is inevitable to encounter karst caves of varying sizes. The presence of these caves causes the blast stress waves to be reflected and refracted multiple times, expanding the loosened zone created by the blast and resulting in severe over-excavation and under-excavation. To ensure construction efficiency, reduce disturbance to the surrounding rock caused by blasting, obtain a better tunnel outline, and control construction costs, it is necessary to address the relationship between karst caves and blasting parameters.

[0004] During the construction of a certain highway, some tunnels traversed karst geology, with numerous sinkholes distributed in the surrounding rock. It was necessary to prevent the presence of these sinkholes from adversely affecting blasting operations, including significant disturbance to the surrounding rock, impacting its stability, and even leading to severe over- or under-excavation. Over- or under-excavation caused by blasting is a major technical challenge, especially in karst areas where controlling excavation quality is difficult when using blasting. Summary of the Invention

[0005] The purpose of this invention is to address the problem of difficulty in effectively controlling excavation quality during blasting construction in karst areas. This invention provides a method for dynamically adjusting drilling and blasting parameters in karst tunnels. This method can effectively control the over-excavation and under-excavation caused by blasting construction in karst geology, and has significant economic and social benefits.

[0006] This invention is achieved through the following technical solution:

[0007] This invention provides a method for dynamically adjusting drilling and blasting parameters in karst tunnels, comprising:

[0008] Advanced geological forecasting is used to explore the geological conditions in front of the tunnel face, and to obtain the surrounding rock parameters and the location of karst caves within the effective exploration depth in front of the tunnel face;

[0009] Based on the obtained surrounding rock parameters and the location of the karst cave, the karst cave influence zone is determined, and blasting parameters are preset to conduct test blasting on the surrounding rock in front of the tunnel face;

[0010] Using 3D laser scanning technology, the outline of the blasting operation is obtained. The blasting parameters of the affected area are dynamically adjusted according to the blasting effect, and a test blast is conducted again to finally determine the blasting parameters.

[0011] In some embodiments, advanced geological prediction uses the TSP303 advanced geological prediction system and ground-penetrating radar to detect the geological conditions in front of the tunnel face, comprehensively determine whether there are karst caves in front of the tunnel face, and draw a map of the location of the karst caves.

[0012] In some embodiments, the karst cave influence zone is divided based on the positional relationship between the karst cave and the tunnel outline obtained from advanced geological forecasting. Then, the karst cave data, borehole parameters, influence zone determination criteria, and over-excavation / under-excavation values ​​are imported into MATLAB software to divide the karst cave influence zone.

[0013] In some embodiments, the positional relationship between the cave and the tunnel outline includes the cave being inside the outline, the cave intersecting with the outline, and the cave being outside the outline.

[0014] In some embodiments, the method for preset blasting parameters includes:

[0015] Mark the locations of the blast holes in the affected area based on the identified karst cave influence zone;

[0016] Determine normal blasting parameters based on the theoretical formula for smooth blasting;

[0017] Based on the blasting parameter optimization scheme, the blasting parameters in the affected area are optimized to obtain the preset blasting parameters.

[0018] In some embodiments, the method for determining the location of boreholes in the affected area is to classify boreholes whose blasting damage radius is smaller than the distance between the borehole and the edge of the karst cave as boreholes in the karst cave's affected area based on the relationship between the surrounding rock filling material and the blasting damage radius.

[0019] In some embodiments, when the surrounding rock filling material is air or clay, the radius of the affected area is 1 times the radius of the karst cave; when the surrounding rock filling material is water or soft rock, the radius of the affected area is 1.2 times the radius of the karst cave.

[0020] In some embodiments, the blasting parameter optimization scheme includes:

[0021] Considering the location of the karst cave: reduce the amount of explosive charge in the boreholes by 5% in the area affected by the karst cave;

[0022] Considering the location of the karst cave: By using a directional energy-concentrating blasting device on the blast holes in the karst cave's influence zone, with the directional energy-concentrating direction forming a 180° angle with the direction of the karst cave, the energy-concentrating effect of the karst cave can be counteracted;

[0023] Ignoring the location of karst caves: Blasting operations can be carried out by reducing the charge amount of the peripheral holes by 5% or increasing the spacing between the peripheral holes by 5%.

[0024] In some embodiments, the blasting parameters are optimized based on the positional relationship between the karst cave and the tunnel outline as follows:

[0025] During test blasting and cyclic blasting, if the karst cave is inside the tunnel outline and the distance between the edge of the karst cave and the blast hole is less than the blast damage radius, optimization is performed by using a directional energy-concentrating device. If the karst cave is inside the tunnel outline and the distance between the edge of the karst cave and the blast hole is greater than the blast damage radius, or if the karst cave is outside the tunnel outline and the distance between the edge of the karst cave and the surrounding holes is greater than the blast damage radius, or if the diameter of the karst cave is smaller than the diameter of the blast hole, the normal blasting scheme is used. In other cases, blasting is carried out by reducing the charge amount of the surrounding holes by 5% or increasing the spacing between the surrounding holes by 5%.

[0026] In some embodiments, when adjusting blasting parameters, the priority is: borehole line charge density > perimeter borehole spacing > minimum resistance line.

[0027] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0028] This invention utilizes advanced geological forecasting to detect karst caves ahead of the tunnel face and identify the affected area. After pre-setting blasting parameters, test blasting is conducted on the surrounding rock ahead of the tunnel face. Three-dimensional laser scanning technology is used to acquire the outline of the blasted area, and the blasting parameters are dynamically adjusted based on the blasting effect. In karst geological areas, the use of dynamic blasting technology effectively reduces over- and under-excavation, saves a significant amount of concrete materials, improves construction progress and efficiency, and solves the technical problem of severe over- and under-excavation caused by karst caves and other adverse geological conditions. Simultaneously, it reduces disturbance to surrounding rock strata, effectively protecting the ecological environment of the excavation area, resulting in significant economic and social benefits. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered 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. In the drawings:

[0030] Figure 1This is a flowchart of the construction method for dynamically adjusting drilling and blasting parameters in karst tunnels according to the present invention;

[0031] Figure 2 This is a schematic diagram of the borehole charging structure in this invention;

[0032] Figure 3 This is a schematic diagram of the minimum resistance line in this invention;

[0033] Figure 4 This is a flowchart of the preset blasting parameters in this invention;

[0034] Figures 5a-5c This is a schematic diagram showing the location distribution of the karst caves in this invention;

[0035] Figure 6 This is a flowchart of the cyclic dynamic blasting construction process in this invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0038] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order, or primary and secondary relationship of the indicated technical features.

[0039] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0040] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. In addition, the character " / " in this document generally indicates that the related objects before and after it have an "or" relationship.

[0041] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0042] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces), unless otherwise explicitly specified.

[0043] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0044] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0045] Example

[0046] Please refer to Figures 1-6 The present application provides a method for dynamically adjusting drilling and blasting parameters in karst tunnels, comprising:

[0047] Advanced geological forecasting is used to explore the geological conditions in front of the tunnel face, and to obtain the surrounding rock parameters and the location of karst caves within the effective exploration depth in front of the tunnel face;

[0048] Based on the obtained surrounding rock parameters and the location of the karst cave, the karst cave influence zone is determined, and blasting parameters are preset to conduct test blasting on the surrounding rock in front of the tunnel face;

[0049] Using 3D laser scanning technology, the outline of the blasting operation is obtained. The blasting parameters of the affected area are dynamically adjusted according to the blasting effect, and a test blast is conducted again to finally determine the blasting parameters.

[0050] According to some embodiments of this application, advanced geological prediction uses the TSP303 advanced geological prediction system and ground-penetrating radar to detect the geological conditions in front of the tunnel face, comprehensively determine whether there are karst caves in front of the tunnel face, and draw a map of the location of the karst caves.

[0051] Specifically, the TSP303 advanced geological prediction system is used to detect the tunnel face that needs to be inspected. Data acquisition can typically be performed on any sidewall. If the fault first appears on the right side of the tunnel, the shot points should be located on the right side of the tunnel. When seismic waves encounter interfaces with differences in rock wave impedance (such as faults, fracture zones, and lithological changes), part of the seismic signal is reflected back, and part is transmitted into the medium ahead. The reflected seismic signal is received by a highly sensitive seismic detector. The received data is processed by the TSP win software to understand the nature (weak rock zones, fracture zones, faults, water-bearing strata, etc.), location, and scale of the geological body ahead of the tunnel face. Evaluation of the TSP software processing results shows that if the S-wave reflection is stronger than the P-wave, it indicates that the rock strata are saturated with water. In this case, ground-penetrating radar is used for advanced prediction of the rock strata ahead. The two methods are then cross-validated to determine whether there are cavities ahead.

[0052] Ground-penetrating radar (GPR) uses a transmitting antenna to emit broad-spectrum, high-frequency electromagnetic waves into the underground medium. When these electromagnetic waves encounter interfaces with differences in electrical properties (dielectric constant, conductivity), transmission, refraction, and reflection occur. Simultaneously, the medium absorbs, filters, and scatters the propagating electromagnetic waves. A receiving antenna receives and records the reflected waves from underground. Appropriate processing software is used to process the data, and then the processed data images are combined with engineering geological and geophysical characteristics for inference and interpretation. This allows for the detection of the engineering geological conditions ahead of the tunnel face (surrounding rock properties, geological structure, surrounding rock integrity, groundwater, and karst caves, etc.). Based on a comprehensive assessment of the TSP303 and GPR data, the presence of karst caves ahead is determined. To ensure the accuracy of advanced detection, drilling methods are employed, and some blast holes are deepened (the deepened blast holes cannot be used for blasting later) to detect hidden karst caves around the tunnel face and to create a map of their locations.

[0053] Following blasting, 3D laser scanning technology is used to promptly acquire the tunnel outline, observe the blasting effect, and determine if blasting parameters need modification. If the outline is relatively smooth, blasting cycles continue; if the outline exhibits significant jaggedness, blasting parameters for the affected area of ​​the karst cave need optimization, and another test blast is conducted. 3D laser scanning technology can acquire massive amounts of 3D point cloud data of the scanned object's surface, achieving a leap from point measurement to surface measurement. Compared to traditional measurement methods, the advantages of 3D laser scanning technology are mainly reflected in: high data acquisition rate, high data accuracy, non-contact measurement, diversified data information, and comprehensive data acquisition.

[0054] According to some embodiments of this application, based on advanced geological forecasting and on-site drilling, data and waveforms were analyzed using RADAN software. It was found that the positional relationship between the karst cave and the tunnel mainly falls into three categories: the karst cave is inside the outline, the karst cave intersects with the outline, and the karst cave is outside the outline. Then, the karst cave data, borehole parameters, influence zone determination criteria, and over-excavation / under-excavation values ​​were imported into MATLAB software to delineate the influence zone of the karst cave.

[0055] According to some embodiments of this application, the method for preset blasting parameters includes: marking the positions of blast holes in the determined karst cave influence zone; determining normal blasting parameters according to the theoretical formula of smooth blasting; and optimizing the blasting parameters of the influence zone according to the blasting parameter optimization scheme to obtain preset blasting parameters.

[0056] According to some embodiments of this application, the design of blasting parameters specifically includes:

[0057] 1) Hole diameter and hole depth: my country currently generally uses a hole diameter of 35mm-45mm. A larger hole diameter can concentrate the energy of the explosive and reduce the number of holes. Although this can improve blasting efficiency, it will also reduce the drilling speed and affect the blasting quality and reduce the stability of the surrounding rock.

[0058] The borehole depth is determined based on the time taken for each drilling cycle during tunneling.

[0059]

[0060] In the formula: L is the depth of the blast hole; m is the number of drilling rigs; v is the drilling speed; t is the time occupied by drilling in each tunneling cycle; N is the number of blast holes.

[0061] 2) Charge Structure: In tunnel blasting, the charge structure of the blast hole can be divided into two categories: concentrated charge at the bottom of the hole and decoupled interval charge. The purpose of using decoupled interval charge in the peripheral holes is to buffer the blast shock wave in the air layer, while also prolonging the interaction time between the blasting gas and the rock, reducing the damage to the hole wall caused by blasting, and reducing over-excavation and under-excavation caused by blasting.

[0062] 3) Charge quantity: The total charge quantity is allocated according to the different functions of various blast holes in blasting. Among them, the cut hole is subject to the greatest rock clamping effect and requires the most charge; the auxiliary hole has a large distribution range and a large number of blast holes, and its charge quantity is second only to the cut hole; the peripheral holes require the least charge.

[0063] 4) Borehole plugging: Borehole plugging refers to the process of sealing a blast hole filled with explosives tightly with an inert substance, the filling material being stemming material. Borehole plugging is performed to prolong the time the explosives act on the rock, improve the blasting effect, and increase the utilization rate of explosive energy.

[0064] The specific length of the borehole plug can be determined as follows: a. When the borehole depth h < 1m, the length of the plug should not be less than 1 / 2 of the borehole depth; b. When the borehole depth 1m ≤ h ≤ 2.5m, the length of the plug should not be less than 0.5m; c. When the borehole depth h > 2.5m, the length of the plug should not be less than 1m.

[0065] 5) Minimum Resistance Line: The minimum resistance line refers to the vertical distance from the peripheral boreholes to the nearest collapse hole, also known as the thickness of the blast layer, usually denoted by W. Generally, the value of the minimum resistance line should be greater than or equal to the spacing between peripheral boreholes, and is 10-20 times the borehole diameter. Its calculation formula is as follows:

[0066]

[0067] In the formula: W is the minimum resistance line; E is the spacing between peripheral holes; m is the hole density coefficient, where the value of the hole density coefficient ranges from 0.8 to 1.

[0068] 6) Decoupling Coefficient: When using coupled charges in blasting, the rock experiences the greatest impact from the explosion, and excessive crushing is likely to occur around the borehole, leading to over-excavation. Therefore, decoupled charges are generally used for blasting the peripheral holes. The principle for determining the decoupling coefficient is that the pressure on the hole wall is less than the compressive strength of the rock but higher than its tensile strength. Experiments show that the magnitude of the decoupling coefficient should be adjusted according to the properties of the explosive and the rock strata. Generally, the value range of the decoupling coefficient is 1.5-2.5.

[0069] 7) Spacing between peripheral holes: Spacing between peripheral holes refers to the distance between two adjacent holes on the design outline, usually denoted by E. A smaller spacing increases the number of peripheral holes, leading to increased drilling time and the amount of blasting materials used, thus increasing blasting costs. Furthermore, as the number of holes increases, the linear charge density also increases, increasing damage to the surrounding rock and potentially causing over-excavation, affecting the tunnel's durability and stability. Tunnel blasting effectiveness is controlled by multiple variables, with spacing between peripheral holes being only one. Its value is also related to the minimum resistance line and the hole density coefficient. Therefore, to achieve good blasting results, the spacing between peripheral holes, the minimum resistance line coefficient, and the hole density coefficient must be designed holistically.

[0070] Currently, the main methods for calculating the spacing between peripheral holes include the peripheral hole density coefficient theory and empirical formulas from fracture mechanics theory. The specific calculation methods are as follows:

[0071] a. The theory of peripheral hole density coefficient suggests that a better blasting effect can be achieved when the peripheral hole density coefficient m ranges from 0.8 to 1.0. Therefore, the calculation method for the peripheral hole spacing E is as follows:

[0072] E = (0.8 ~ 1.0)W

[0073] In the formula: W is the thickness of the light burst layer; the proportional coefficient in the formula can be adjusted according to the actual situation on site.

[0074] b. Empirical formulas for fracture mechanics theory:

[0075]

[0076] In the formula: K1 is the adjustment coefficient, which ranges from 6 to 14. The value of the adjustment coefficient K1 is selected according to the rock hardness. When the hardness is high, the adjustment coefficient K1 takes a large value; when the hardness is low, the adjustment coefficient K1 takes a small value; f is the Protodyakonov coefficient of the rock.

[0077] According to some embodiments of this application, based on numerical simulation analysis of blasting, the degree of influence of each parameter on the blasting effect of tunnels in karst areas can be determined, that is, the influence of linear charge density is greater than the influence of the spacing between surrounding holes, which is greater than the influence of the size of the resistance line on the tunnel blasting effect.

[0078] According to some embodiments of this application, based on the relationship between the fourth-level surrounding rock filling material and the blast damage radius, blast holes with a blast damage radius smaller than the distance between the blast hole and the edge of the karst cave are classified as blast holes in the karst cave influence zone.

[0079] According to some embodiments of this application, when the surrounding rock filling material is air or clay, as shown in the influence zone 1 in the figure, the radius r of the influence zone is 1 times the radius of the karst cave; when the surrounding rock filling material is water or soft rock, as shown in the influence zone 2 in the figure, the radius R of the influence zone is 1.2 times the radius of the karst cave.

[0080] According to some embodiments of this application, the presence of karst caves increases the blast damage radius. In order to reduce the impact of karst caves on the blasting effect and obtain a more complete outline, the following three blasting parameter optimization schemes are adopted:

[0081] Option 1, considering the location of the karst cave: reduce the amount of explosive charge in the blast holes by 5% in the area affected by the karst cave;

[0082] Option 2, considering the location of the karst cave: Since the existence of the karst cave is equivalent to the direction of the blasting hole, the blasting energy is concentrated towards the location of the karst cave, which has a certain energy-concentrating effect. By using a directional energy-concentrating blasting device on the blast holes in the karst cave's influence area, the directional energy-concentrating direction is at a 180° angle to the direction of the karst cave, thus counteracting the energy-concentrating effect of the karst cave.

[0083] Option 3, without considering the location of the karst cave: blasting operations can be carried out by reducing the charge amount of the peripheral holes by 5% or increasing the spacing between the peripheral holes by 5%.

[0084] The following is a comparative analysis of the effects of the three blasting parameter optimization schemes based on the relative positional relationship between the karst cave and the tunnel outline:

[0085] 1) The cave is inside the outline.

[0086] Through on-site construction and numerical simulation of blasting, it was found that when the karst cave is inside the outline and far from the surrounding boreholes, blasting with normal parameters can obtain a relatively complete tunnel outline without optimization. However, when the distance between the edge of the karst cave and the blast hole is less than the blast damage radius, blasting with normal parameters results in severe over-excavation and under-excavation, requiring optimization of the blasting parameters. Comparison of the three optimization schemes revealed that Scheme 2 yielded the most complete tunnel outline after blasting excavation, followed by Scheme 2, with Scheme 3 being the worst.

[0087] 2) The cave intersects with the outline.

[0088] Because the karst cave intersects with the tunnel outline, the outline of the karst cave area differs significantly from the designed outline after blasting. On-site construction and numerical simulations of the blasting revealed that, with normal blasting parameters, over-excavation and under-excavation were also severe in areas other than the karst cave, necessitating optimization of the blasting parameters. Comparison of three optimization schemes showed that Scheme 1 produced the most complete tunnel outline after blasting excavation, followed by Scheme 3, with Scheme 2 being the worst.

[0089] 3) The cave is outside the outline.

[0090] When the distance between the edge of the karst cave and the surrounding holes is less than the blasting damage radius, comparing the three optimization schemes: Scheme 3 has the most complete tunnel outline after blasting excavation, Scheme 2 is the second best, and Scheme 3 is the worst.

[0091] According to some embodiments of this application, the blasting parameters are optimized based on the positional relationship between the karst cave and the tunnel outline as follows: During test blasting and cyclic blasting, when the karst cave is inside the tunnel outline and the distance between the edge of the karst cave and the blast hole is less than the blast damage radius, optimization is performed by using a directional energy-concentrating device; when the karst cave is inside the tunnel outline and the distance between the edge of the karst cave and the blast hole is greater than the blast damage radius, or when the karst cave is outside the tunnel outline and the distance between the edge of the karst cave and the surrounding holes is greater than the blast damage radius, or when the diameter of the karst cave is smaller than the diameter of the blast hole, the normal blasting scheme is used; in other cases, blasting is carried out by reducing the charge amount of the surrounding holes by 5% or increasing the spacing between the surrounding holes by 5%.

[0092] It should be noted that when the blast hole passes through the karst cave, the blast damage radius is not much different from that without the karst cave. Moreover, as the distance between the karst cave and the blast hole increases, the influence on the blast damage radius becomes smaller and smaller. Therefore, the blast hole parameters inside the karst cave remain unchanged.

[0093] According to some embodiments of this application, it is difficult to accurately predict the specific edge location and size of the karst cave during construction. Therefore, if a hidden karst cave is found ahead of the tunnel face during on-site construction, Scheme 1 is used for optimization. Based on on-site construction experience and existing numerical simulation results, the following principles for adjusting blasting parameters are derived:

[0094] (1) There is a slight over-excavation phenomenon. The linear charge density of the blast holes in the affected area should be reduced by 5%.

[0095] (2) There is a slight under-drilling phenomenon. The linear charge density of the blast holes in the affected area should be increased by 5%.

[0096] (3) There is a serious over-excavation phenomenon. The density of the linear charge in the blast holes in the affected area should be reduced by 10%.

[0097] (4) There is a serious under-drilling phenomenon. The linear charge density of the blast holes in the affected area should be increased by 10%.

[0098] According to some embodiments of this application, since the effective detection depth of ground-penetrating radar varies with the surrounding rock grade (30m for Grade I, 20m for Grade II, and 10m for Grade III), the effective detection depth of ground-penetrating radar is defined as a total cycle. When blasting operations exceed the effective detection depth of ground-penetrating radar, it is necessary to use ground-penetrating radar again for geological advance prediction to obtain the distribution of karst caves ahead of the tunnel face. Then, based on the numerical simulation results, the blasting parameters are readjusted. When adjusting the blasting parameters, the priority is: linear charge density of blast holes > spacing between blast holes in the perimeter > minimum resistance line. It is recommended to adjust only the linear charge density.

[0099] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for dynamically adjusting drilling and blasting parameters in karst tunnels, characterized in that, include: Advanced geological forecasting is used to explore the geological conditions in front of the tunnel face, and to obtain the surrounding rock parameters and the location of karst caves within the effective exploration depth in front of the tunnel face; Based on the obtained surrounding rock parameters and the location of the karst cave, the karst cave influence zone is determined, and blasting parameters are preset to conduct test blasting on the surrounding rock in front of the tunnel face; The contour line after blasting is obtained by using three-dimensional laser scanning technology. The blasting parameters of the affected area are dynamically adjusted according to the blasting effect. Another test blast is carried out to finally determine the blasting parameters. Methods for presetting explosive parameters include: Mark the locations of the blast holes in the affected area based on the identified karst cave influence zone; Determine normal blasting parameters based on the theoretical formula for smooth blasting; Based on the blasting parameter optimization scheme, the blasting parameters of the affected area are optimized to obtain the preset blasting parameters; The optimization scheme for blasting parameters includes: When a karst cave intersects with the tunnel outline, reduce the amount of explosive charge in the blast holes in the area affected by the karst cave by 5%. When the karst cave is inside the tunnel outline and the distance between the edge of the karst cave and the blast hole is less than the blast damage radius, the directional energy-concentrating blasting device is used on the blast holes in the karst cave's influence zone. The directional energy-concentrating direction is at a 180° angle to the direction of the karst cave to counteract the energy-concentrating effect of the karst cave. When the karst cave is outside the tunnel outline and the distance between the edge of the karst cave and the surrounding holes is less than the blasting damage radius, blasting can be carried out by reducing the charge amount of the surrounding holes by 5% or increasing the spacing between the surrounding holes by 5%. When a karst cave is located inside the tunnel outline and the distance from the edge of the karst cave to the blast hole is greater than the blast damage radius, or when a karst cave is located outside the tunnel outline and the distance from the edge of the karst cave to the surrounding holes is greater than the blast damage radius, or when the diameter of the karst cave is smaller than the diameter of the blast hole, normal blasting parameters shall be used for blasting.

2. The method for dynamically adjusting drilling and blasting parameters in karst tunnels according to claim 1, characterized in that, Advanced geological prediction uses the TSP303 advanced geological prediction system and ground-penetrating radar to detect the geological conditions in front of the tunnel face, comprehensively determine whether there are karst caves in front of the tunnel face, and draw a map of the location of the karst caves.

3. The method for dynamically adjusting drilling and blasting parameters in karst tunnels according to claim 1, characterized in that, The karst cave influence zone is determined by the positional relationship between the karst cave and the tunnel outline obtained from advanced geological forecasting. Then, the karst cave data, borehole parameters, influence zone determination criteria, and over-excavation / under-excavation values ​​are imported into MATLAB software for division and determination.

4. The method for dynamically adjusting drilling and blasting parameters in karst tunnels according to claim 1, characterized in that, The method for determining the location of blast holes in the affected area is based on the relationship between the surrounding rock filling material and the blast damage radius. Bore holes with a blast damage radius smaller than the distance between the borehole and the edge of the karst cave are classified as boreholes in the karst cave's affected area.

5. The method for dynamically adjusting drilling and blasting parameters in karst tunnels according to claim 4, characterized in that, When the surrounding rock filling material is air or clay, the radius of the affected area is 1 times the radius of the karst cave; when the surrounding rock filling material is water or soft rock, the radius of the affected area is 1.2 times the radius of the karst cave.

6. The method for dynamically adjusting drilling and blasting parameters in karst tunnels according to claim 1, characterized in that, When adjusting blasting parameters, the priority order is: borehole line charge density > perimeter borehole spacing > minimum resistance line.

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