Weak disturbance accurate excavation control method and construction device for broken surrounding rock

Abstract

The invention relates to the technical field of tunnel and underground engineering construction, and discloses a weak disturbance accurate excavation control method and construction device for broken surrounding rock.A parameterized model is established based on a long and short hole different-plane conjugate strategy, arc drilling is implemented by utilizing controlled bending of a flexible drill rod, and the construction efficiency is improved. The end hole track is tangentially parallel to the design axis to eliminate the external insertion angle; during drilling, monitoring lateral force for maintaining bending in real time to feed back the mechanical property of the surrounding rock, and dynamically correcting the explosive charging linear density of the blast hole according to the mechanical property; the density of centralizing fins outside the cartridge is adjusted according to the curvature distribution of the axis of the hole, and a self-adaptive centering charging structure matched with the arc-shaped hole is constructed; during blasting, the short hole is controlled to be detonated in advance, and a micro-fissure zone is prefabricated between the long hole and the contour line to serve as a stress wave cut-off interface. The device comprises an electric automatic paint spraying rod integrating laser ranging, dip angle monitoring and automatic marking functions. The method solves the problem of back break of broken surrounding rocks, and realizes precise contour forming and low damage control of the surrounding rocks.

Description

Technical Field

[0001] This invention relates to the field of tunnel and underground engineering construction technology, specifically to a method and construction device for precise excavation control with weak disturbance in fractured surrounding rock. Background Technology

[0002] In tunnel and underground engineering excavation in weak and fractured surrounding rock (such as Class IV and V surrounding rock), the drill-and-blast method is widely used due to its strong adaptability. However, under fractured surrounding rock geological conditions, achieving precise contour shaping and controlling damage to the remaining surrounding rock has always been a technical challenge in construction.

[0003] Current peripheral drilling operations typically rely on rigid drill rods in conjunction with drilling rigs. Limited by the structural dimensions of the drilling rig's propulsion beam and minimum working space requirements, a certain outward angle must be reserved during drilling to ensure the hole bottom reaches the designed outline. This inherent geometric constraint results in a sawtooth-shaped tunnel profile after excavation, inevitably leading to over-excavation. This not only increases the volume and cost of subsequent concrete spraying but, more seriously, frequent over-excavation and backfilling worsens the stress state of the fractured surrounding rock. Furthermore, existing explosive charge designs are usually based on average lithological parameters given in geological survey reports, constituting a static design. However, the geological conditions of fractured surrounding rock can change drastically over a very short distance. Traditional construction methods lack the means to perceive local rock hardness changes in real time during drilling, resulting in explosive charges often failing to match the actual rock properties. When encountering localized weak interlayers, the conventionally designed explosive charge will generate excessive explosive energy, exacerbating the damage to the surrounding rock.

[0004] Furthermore, regarding the blasting mechanism, while traditional smooth blasting improves the shaping effect to some extent, its essence still relies on the shock wave and high-pressure gas generated by the explosive detonation to break the rock. At the moment of detonation, the high-energy shock wave propagates directly in all directions. For fractured surrounding rock with well-developed joints and fissures, this uninterrupted shock wave can easily induce loosening and fissure expansion in the deeper rock mass, destroying the original self-bearing capacity of the surrounding rock. Existing blasting technologies lack effective stress wave guiding or interception mechanisms to physically block the propagation of shock waves to the deeper parts of the remaining surrounding rock.

[0005] Finally, regarding the charge structure and construction aids, a decoupled charge structure is usually required to achieve good blasting results. However, in actual operation, due to gravity, it is difficult for the charge cartridge to maintain an ideal centered position within the borehole, easily resulting in adhesion to the borehole wall and uneven distribution of blast pressure. This eccentricity problem is particularly pronounced when attempting to correct the borehole profile by using curved holes or adjusting angles. Furthermore, on-site borehole layout often relies on simple manual marking with hand tools, lacking precise guidance for drilling angles and depths, further limiting the improvement of excavation accuracy. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method and construction device for precise excavation control with weak disturbance in fractured surrounding rock. It solves the problems in existing tunnel construction in fractured surrounding rock caused by the presence of borehole insertion angle and the inability of charging parameters to dynamically match the rock type, resulting in over-excavation and under-excavation, excessive damage to the surrounding rock, the propagation of blasting shock waves to deeper parts that damages the stability of the surrounding rock, and uneven distribution of explosive energy caused by the eccentricity of the explosive cartridge against the wall in the blast hole.

[0007] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of the present invention provides a method for precise excavation control with weak disturbance in fractured surrounding rock, the method comprising the following steps:

[0008] S1. Establish a local spatial rectangular coordinate system on the working face. Based on the strategy of conjugate of long and short boreholes, use a parametric model to calculate the three-dimensional coordinate parameters of the long and short boreholes. The parameters include the starting point position, drilling depth and inner offset distance.

[0009] S2. Based on the three-dimensional coordinate parameters, perform peripheral drilling, use flexible drill rods to perform arc drilling, and apply lateral pre-tightening force to the drill rod to make the drill rod elastically bend until the bottom tangent direction of the hole is parallel to the tunnel design axis.

[0010] S3. During the arc drilling process, the peak value of the lateral force required to maintain the bending of the drill rod is monitored in real time, and the peak value of the lateral force is used as a feedback parameter to characterize the local mechanical properties of the surrounding rock, and the charge linear density of the corresponding borehole is dynamically corrected.

[0011] S4. Construct an adaptive centering charge structure that is physically matched with the borehole geometry. Based on the curvature distribution of the borehole axis formed by arc drilling, adjust the longitudinal distribution density of the elastic centralizing wing on the outside of the charge cartridge to keep the charge cartridge centered in the arc-shaped borehole.

[0012] S5. Implement long and short hole stress wave guided blasting, control the short hole to detonate before the long hole, and use the micro-fracture zone formed between the long hole and the design outline by the short hole detonation as the stress wave cutoff interface to attenuate the impact energy of the long hole blasting on the remaining surrounding rock.

[0013] Preferably, in step S1, the long and short borehole conjugate strategy specifically includes: setting the long hole as the main excavation hole and the short hole as the guide hole. First, based on the excavation progress and the positioning distance of the drilling equipment, the radial inward offset distance of the starting point of the long hole is calculated, so that the ending point of the long hole at a predetermined depth falls on the design contour line. Second, the starting point of the short hole is set to be located between the starting point of the long hole and the design contour line, and the drilling trajectory of the short hole and the drilling trajectory of the long hole form a hyperboloid tangent structure in space, and the drilling depth of the short hole is less than the drilling depth of the long hole.

[0014] Preferably, in step S2, the trajectory control of the arc drilling needs to meet the following boundary conditions: the starting point coordinates are located inside the design contour line; the ending point coordinates coincide with the design contour line; the slope of the tangent line of the drilling trajectory at the ending point approaches zero, thereby eliminating the external insertion angle at the bottom of the hole.

[0015] Preferably, in step S3, the specific operation of dynamically correcting the linear density of the charge in the corresponding borehole is as follows: setting the reference lateral force required for the drill rod to reach a predetermined curvature under standard surrounding rock conditions; calculating the ratio of the measured peak lateral force to the reference lateral force, and determining the surrounding rock correction coefficient based on the ratio and the lithology sensitivity index; multiplying the reference linear density of the charge by the surrounding rock correction coefficient to obtain the actual linear density of the charge; if the actual linear density of the charge is lower than a preset threshold, then switching the charge structure to a pre-made charge cartridge with a smaller diameter.

[0016] Preferably, in step S4, adjusting the longitudinal distribution density of the elastic centralizing wing on the outer side of the propellant cartridge specifically involves: calculating the geometric curvature of the borehole trajectory along the depth direction; setting the longitudinal distribution density of the elastic centralizing wing to be positively correlated with the geometric curvature, increasing the wing density in borehole sections with larger curvature, and maintaining the basic wing density in straight sections; supporting the propellant cartridge with the elastic centralizing wing to ensure that the ratio of borehole diameter to propellant cartridge diameter is maintained within a preset decoupling coefficient range throughout the entire length.

[0017] Preferably, in one specific embodiment, in the adaptive centering charge structure, the charge roll is made of PVC pipe with an inner diameter of 27mm and mixed with emulsion explosive or finished emulsion explosive with a diameter of 25mm, and the decoupling coefficient is greater than 1.5.

[0018] Preferably, in step S5, the formation mechanism of the stress wave cutoff interface is as follows: the short hole adopts an extremely weak charge or an air-gap charge structure; after the short hole is detonated first, a micro-crack zone with a specific curvature is prefabricated in the shallow region between the long hole and the design outline. The micro-crack zone serves as a wave impedance mismatch interface to reflect and attenuate the shock wave generated by the detonation of the long hole.

[0019] Preferably, in step S5, the timing control of the long and short hole stress wave guided coordinated blasting needs to satisfy the following: the detonation time of adjacent long holes lags behind the detonation time of short holes, and the lag time difference is determined according to the distance between the long holes and the short holes and the longitudinal wave velocity of the rock mass.

[0020] Preferably, the charge amount in the short hole is one-third to one-quarter of the charge amount in the long hole, and the charge section in the short hole is mainly distributed in the bottom area of ​​the hole.

[0021] A second aspect of the present invention provides a low-disturbance precision excavation construction device for fractured surrounding rock. The device is used to assist in achieving precise hole positioning and includes: an electric self-spraying paint rod, an electric switch, an inclination sensor, a laser rangefinder display, a laser rangefinder sensor, a base, a fixing ring, a fastening plate, bolts, nuts, and a paint can.

[0022] Specifically, the electric spray paint pole has an electric switch electrically connected to its outer wall for controlling the spraying operation; an angle sensor electrically connected to its outer wall for monitoring the pole's posture; and a laser rangefinder and laser range sensor electrically connected to its top for measuring distance data. A base is fixedly connected to the top of the electric spray paint pole for supporting components. Two fixing rings are fixedly connected to the top of the electric spray paint pole, each with a fastening plate at one end. Bolts are threaded between the fastening plates, and nuts are threaded to one end of each bolt, securing the paint can to the base. The paint can is slidably connected inside the base, and its outer wall is slidably connected between the fixing rings.

[0023] This invention provides a method and construction device for controlling precise excavation with minimal disturbance in fractured surrounding rock. It offers the following advantages:

[0024] 1. This invention employs a flexible drill rod to implement an arc-drilling process. By utilizing the controlled elastic bending characteristics of the drill rod, the tangent direction at the bottom of the borehole is made parallel to the tunnel design axis. This eliminates the unavoidable external angle of conventional straight-line drilling from a physical and geometric perspective, achieving precise shaping of the tunnel profile. Simultaneously, the lateral force required to maintain the bending of the drill rod during drilling is used as a direct feedback of the local mechanical properties of the surrounding rock. Based on this, the charge linear density is dynamically adjusted to ensure that the blasting energy input matches the actual hardness of the surrounding rock, avoiding over-excavation or excessive disturbance to the fractured surrounding rock caused by excessive charge.

[0025] 2. This invention utilizes a strategy of conjugate long and short boreholes with different surfaces, combined with micro-delay detonation technology, to control the detonation of short holes first. This prefabricates a micro-fracture zone between the main blasting zone of the long holes and the designed outline, thus constructing a physical stress wave cutoff interface. When subsequent long holes are detonated, this interface uses the principle of wave impedance mismatch to force the high-energy shock wave to be reflected and attenuated, effectively blocking the direct propagation of blasting vibration to the deep part of the remaining surrounding rock, thereby significantly improving the excavation stability of the fractured surrounding rock section.

[0026] 3. This invention constructs an adaptive centering charging structure adapted to the geometry of the arc-shaped borehole. By configuring the longitudinal density of the elastic centralizing blades according to the differential distribution of the borehole axis curvature, it effectively overcomes the problem of the charge cartridge sticking to the wall and being eccentric due to gravity or elastic restoring force in the arc-shaped borehole. This structure, combined with a construction device with laser ranging and tilt monitoring functions, ensures the accuracy of the borehole trajectory and the constant decoupling coefficient along the entire length, ensuring that the explosive stress wave acts uniformly on the rock mass in the radial direction. Attached Figure Description

[0027] Figure 1 This is a perspective view of the construction device of the present invention;

[0028] Figure 2 This is a schematic diagram of the paint can structure of the present invention;

[0029] Figure 3 for Figure 2 A magnified view of the structure at point A in the middle;

[0030] Figure 4 This is a block diagram of the system module structure of the present invention;

[0031] Figure 5 This is a flowchart illustrating the overall process of the method of the present invention.

[0032] The components include: 1. Electric self-spraying paint rod; 2. Electric switch; 3. Tilt sensor; 4. Laser rangefinder display; 5. Laser rangefinder sensor; 6. Base; 7. Fixing ring; 8. Fastening plate; 9. Bolt; 10. Nut; 11. Paint can; 100. Parametric geometric modeling module; 200. Drilling penetration feedback module; 300. Adaptive charge decision module; 400. Cooperative blasting timing control module. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] See attached document Figure 1 - Appendix Figure 3 The present invention provides a low-disturbance precision excavation construction device for fractured surrounding rock, which includes: an electric self-spraying paint rod 1, an electric switch 2, an inclination sensor 3, a laser rangefinder display 4, a laser rangefinder sensor 5, a base 6, a fixing ring 7, a fastening plate 8, a bolt 9, a nut 10, and a paint can 11.

[0035] The main structure of this low-disturbance precision excavation construction device for fractured surrounding rock consists of an electric self-spraying paint rod 1. The electric self-spraying paint rod 1 serves as an extension component for handheld or robotic arm gripping, and an electric switch 2 is mounted on its outer wall. The electric switch 2 is electrically connected to the control circuit inside the electric self-spraying paint rod 1, and is used to control the device's opening and closing, as well as its spraying action.

[0036] An inclination sensor 3 is also installed on the outer wall of the electric self-spraying paint rod 1. The inclination sensor 3 is electrically connected to the data processing unit or an external display device to detect the inclination angle of the axis of the electric self-spraying paint rod 1 relative to the plumb line in real time. This data is used to assist the operator in determining the initial positioning angle of the drill rod.

[0037] At the top of the electric self-spraying paint pole 1, a laser rangefinder 5 and a laser rangefinder display 4 are installed. The emitting end of the laser rangefinder 5 faces forward of the device and is used to measure the straight-line distance from the top of the electric self-spraying paint pole 1 to the rock face of the working face. The laser rangefinder display 4 is electrically connected to the laser rangefinder 5 and is used to display the measured distance value in real time.

[0038] A base 6 is fixedly connected to the top of the electric spray paint stick 1. The base 6 serves as a connecting component and has a sliding cavity inside for accommodating objects. The paint can 11 is slidably connected to the internal cavity of the base 6.

[0039] To secure the paint can 11, two retaining rings 7 are fixedly connected to the top of the electric spray paint rod 1. The two retaining rings 7 are arranged at intervals along the axial direction of the paint can 11, and the outer wall of the paint can 11 is slidably connected between the inner rings of the retaining rings 7.

[0040] Each retaining ring 7 extends from one end and is fixedly connected to a fastening plate 8. The two fastening plates 8 are arranged opposite each other and are connected by bolts 9 and nuts 10. The bolts 9 pass through through holes in the fastening plates 8, and one end of the bolts 9 is threadedly connected to the nuts 10.

[0041] By rotating the nut 10, the distance between the two fastening plates 8 can be adjusted, thereby tightening the retaining ring 7. This mechanical structure uses friction to lock the paint can 11 to the top of the electric spray paint lever 1. When the electric switch 2 is triggered, the electric spray paint lever 1 controls the paint can 11 to spray marking paint onto the target rock surface, completing the hole marking operation.

[0042] See attached document Figure 4 The present invention provides a low-disturbance precision excavation control system for fractured surrounding rock. The system serves as the hardware and logic carrier for executing the control method and includes: a parametric geometric modeling module 100, a drilling penetration feedback module 200, an adaptive charge decision module 300, and a collaborative blasting timing control module 400.

[0043] The parametric geometric modeling module 100 is used to perform spatial planning before drilling. This module receives tunnel design contour parameters, surrounding rock geological grade parameters, and excavation advance parameters as input data. The parametric geometric modeling module 100 integrates a three-dimensional coordinate calculation unit. This unit calculates and generates the three-dimensional coordinate parameters of long and short boreholes based on a conjugate strategy for long and short boreholes, including the starting point coordinates (x0, y0, z0), drilling depth L, and internal deflection angle α. The coordinate data output by this module is transmitted to the laser positioning equipment or the control center of the drilling rig on site.

[0044] The drilling penetration feedback module 200 is electrically connected to the hydraulic or electric drive system of the drilling equipment. This module is active during drilling operations and is used to acquire real-time data on the lateral force acting on the drill pipe. The drilling penetration feedback module 200 includes a force sensor interface unit and a peak extraction unit. The force sensor interface unit records the lateral force values ​​that maintain the drill pipe bending at a millisecond-level sampling frequency; the peak extraction unit identifies the peak lateral force F from the time-domain signal. peak The drilling penetration feedback module 200 maps the extracted mechanical feature values ​​to the surrounding rock hardness index and transmits them to the next level module.

[0045] The adaptive charge decision module 300 is signal-connected to the drilling penetration feedback module 200. This module stores a standard drilling mechanics model under reference surrounding rock conditions. The adaptive charge decision module 300 calculates a surrounding rock correction coefficient by comparing the measured peak lateral force with the reference value. Based on this coefficient, the module outputs a charge linear density correction command for a specific borehole, as well as a longitudinal distribution density scheme for the elastic centralizing vanes on the outer side of the charge cartridge. This scheme guides on-site charge operations or controls the filling parameters of the automatic charger.

[0046] The collaborative blasting timing control module 400 is used to generate the detonation delay scheme for the electronic detonators. Based on the spatial distance data between the long and short holes and the acoustic velocity parameters of the rock mass, this module calculates the minimum lag time difference between the short and long holes. The collaborative blasting timing control module 400 writes the calculated delay data into the corresponding electronic detonator chip, ensuring a stress wave guiding mechanism of short hole detonation first and long hole detonation later on a millisecond-level timescale.

[0047] The above modules interact with each other through industrial fieldbus or wireless data transmission network, and together they form a closed-loop control system for precise excavation of fractured surrounding rock with weak disturbance.

[0048] See attached document Figure 5 This invention provides a method for precise excavation control with weak disturbance in fractured surrounding rock. This method combines parametric geometric design, drilling mechanics feedback and collaborative blasting technology to form a closed-loop control process.

[0049] S1. Establish a local spatial rectangular coordinate system at the working face. Within this system, based on the strategy of eccentric conjugate of long and short boreholes, a parametric model is used to calculate the three-dimensional coordinate parameters of the long and short boreholes. These parameters specifically include the starting point location, drilling depth, and internal offset distance. This step establishes the spatial geometric relationship of the boreholes through mathematical modeling, providing a data foundation for subsequent differentiated construction.

[0050] S2. Based on the aforementioned three-dimensional coordinate parameters, peripheral borehole construction is carried out. During this process, a flexible drill rod is used to implement an arc-drilling technique. The construction device applies a lateral preload to the drill rod, utilizing its own elastic deformation to generate a bending trajectory. By controlling the magnitude and direction of the lateral preload, the bending state of the drill rod is continuously adjusted until the tangent direction at the bottom of the hole is parallel to the tunnel design axis. This operation eliminates the external angle at the bottom of the hole, ensuring that the drilling trajectory is tangent to the design contour line.

[0051] S3 refers to real-time monitoring of the peak lateral force required to maintain drill pipe bending during arc drilling. This peak lateral force reflects the lateral constraint strength of the surrounding rock on the drill pipe and is a direct physical quantity characterizing the local mechanical properties of the surrounding rock. This method uses the peak lateral force as a feedback parameter to dynamically correct the charge linear density of the corresponding borehole according to a preset mechanical model, thereby achieving the purpose of automatically adjusting the explosive amount according to the rock hardness.

[0052] S4. Construct an adaptive centering charge structure that physically matches the borehole geometry. Based on the borehole axis curvature distribution data formed by arc drilling in step S2, adjust the longitudinal distribution density of the elastic centralizing vanes on the outside of the charge cartridge. In sections with large borehole curvature, increase the distribution density of the elastic centralizing vanes to resist the weight or tension of the charge cartridge itself, forcing the charge cartridge to maintain a geometrically centered state within the arc-shaped borehole, ensuring a constant decoupling coefficient throughout the entire length.

[0053] S5. Implement coordinated long and short borehole stress wave guided blasting. This step, through precise timing control, ensures that the short borehole is detonated before the long borehole. The pre-detonation of the short borehole creates a micro-fracture zone in the rock mass between the long borehole and the designed outline. This micro-fracture zone physically constitutes a stress wave cutoff interface. When the long borehole is subsequently detonated, the resulting blast shock wave undergoes reflection and transmission attenuation upon propagation to this interface, thereby blocking the propagation of the high-energy shock wave to the remaining surrounding rock and achieving minimally disturbed excavation.

[0054] This invention provides a method for precise excavation control with minimal disturbance in fractured surrounding rock. In step S1, a spatial rectangular coordinate system O-XYZ is first established at the tunnel excavation face. The origin O is set at the geometric center of the bottom of the design outline, Z points towards the unexcavated rock mass, X is parallel to the tunnel face horizontally to the right, and Y is parallel to the tunnel face vertically upward. Under this coordinate system, based on the geological characteristics of the fractured surrounding rock, a hole layout strategy of conjugate long and short boreholes is adopted, and the three-dimensional coordinates of the boreholes are calculated through a parametric model.

[0055] The parametric model first defines the basic input parameters: the radius of the tunnel design outline is set to R, the planned cycle advance is S, and the distance from the initial shotcrete frame positioning point of the drilling rig or rock drill to the working face is D. frame Based on the above basic parameters, the length H of the long hole is calculated. L The geometric parameters of the long hole H. L As the main excavation hole, its starting point Radial inward offset distance ΔL and borehole depth Based on the equipment's geometric constraints and tunneling requirements, the following formula is used for calculation:

[0056]

[0057] Where k1 is the slewing radius coefficient of the drill arm, C1 is the basic safety constant considering the width of the drill arm structure, and θ L This is the nominal external insertion angle of the elongated hole. The radial inward offset distance Δ is determined by this formula. L This ensures that the drill pipe has sufficient elastic bending space during drilling, allowing the long hole to reach the predetermined depth. The final hole point can be precisely located on the design outline.

[0058] After determining the parameters of the long hole, calculate the short hole H. S The geometric parameters of the short hole H. S Used for contour trimming and constructing stress wave-guided interfaces. Drilling depth of short holes. Set to 0.3 to 0.5 times the cyclic advance S. The inner offset distance Δ at the starting point of the short hole. S The following relationship must be satisfied:

[0059] Δ S =Δ L -δ gap ;

[0060] Where, δ gap This is a constant representing the radial spacing between the long and short holes at the hole opening cross-section. This parameter setting ensures that the starting point of the short hole is located in the transition region between the starting point of the long hole and the design contour line.

[0061] Based on the coordinate parameters calculated above, the long borehole and the short borehole form a skewed conjugate structure in space. Specifically, the trajectory of the long borehole starts from the innermost starting point and extends to the deep contour line; the trajectory of the short borehole starts from the outermost starting point and extends to the shallow region. The drilling trajectories of the short and long boreholes are geometrically tangent to each other as hyperboloids. This geometric layout ensures that the short borehole mainly acts on the shallow region of the tunnel contour line, while the long borehole acts on the deep region. They do not interfere with each other spatially, but they create a synergistic effect in the distribution of the stress field generated by blasting. The three-dimensional coordinate data calculated by this parametric model is transmitted to the control unit of the drilling equipment or calibrated on-site by construction personnel based on laser ranging data.

[0062] This invention provides a method for precise excavation control with weak disturbance in fractured surrounding rock, wherein in steps S2 and S3, geometric control of the borehole trajectory is combined with real-time detection of the mechanical properties of the surrounding rock.

[0063] In step S2, peripheral boreholes are drilled based on the three-dimensional coordinate parameters calculated in step S1. For each borehole, a flexible drill rod is used for drilling. After the borehole is pulled in, a lateral preload F is applied to the flexible drill rod using a drill string holder or guide device at the front end of the drilling equipment. lat The lateral preload forces the flexible drill pipe to bend elastically during drilling, forming a controlled arc-shaped trajectory.

[0064] Let the trajectory function of the drill pipe axis on the longitudinal section be x(z), which is controlled to satisfy specific boundary conditions. First, at the borehole opening position z = 0, the transverse coordinate x(0) of the drill pipe is set to R - Δ, where R is the design contour radius and Δ is the calculated inner offset distance. Second, at the bottom of the borehole position z = L depth At point L, the lateral coordinate of the drill pipe is x(L). depth The radius RR of the design profile is reverted. Simultaneously, the derivative x of the drill rod at the bottom of the hole is controlled. ‘ (L depth The boundary condition approaches 0. This boundary condition ensures that the tangent direction at the bottom of the borehole is parallel to the tunnel design axis, thereby physically eliminating the unavoidable external angle of traditional straight-line drilling and achieving zero over-excavation geometry.

[0065] During the aforementioned arc drilling process, step S3 is executed simultaneously. The drilling equipment's sensor system monitors in real time the peak lateral force F required to maintain the drill rod reaching the predetermined bending trajectory. peak The peak lateral force F peak This directly reflects the ability of the surrounding rock to constrain the lateral deformation of the drill pipe, and its magnitude is positively correlated with the local hardness and integrity of the surrounding rock. Therefore, this method uses the peak lateral force F peakAs a feedback parameter characterizing the local mechanical properties of the surrounding rock.

[0066] Based on the acquired feedback parameters, the data processing unit performs a quantitative correction calculation for the charge amount. First, the reference lateral force F is defined. ref This value represents the theoretical or empirical lateral force required for the drill pipe to achieve the same degree of bending under standard reference surrounding rock conditions. Next, the surrounding rock correction factor ξ for the i-th borehole is calculated using a power-law formula. i :

[0067]

[0068] Wherein, λ is the lithology sensitivity index, which is determined based on field rock mechanics tests and is used to adjust the sensitivity of the correction.

[0069] Obtain the surrounding rock correction coefficient ξ i Then, calculate the actual linear density of the propellant charge in the borehole. The calculation formula is:

[0070]

[0071] Where, q base This serves as the baseline charge linear density. The system will then calculate the actual charge linear density. Compare with the preset minimum charge threshold. If the actual charge linear density... If the current surrounding rock is below the threshold, it is determined that the rock is extremely weak. In this case, the system outputs a command to switch the charge structure of the borehole to a smaller diameter pre-cast cartridge, for example, switching from a 32 mm diameter cartridge to a 25 mm diameter cartridge, in order to reduce the total blasting energy while maintaining a reasonable decoupling coefficient. Through the above process, dynamic physical matching between the drilling process and the charge parameters is achieved.

[0072] This invention provides a method for precise excavation control with minimal disturbance in fractured surrounding rock. In step S4, an adaptive centering charge structure is constructed to adapt to the geometry of the arc-shaped borehole. This structure aims to solve the problem of wall eccentricity caused by gravity or tension in traditional straight-type explosive charges within the arc-shaped borehole, ensuring uniform radial transmission of blasting energy.

[0073] This step first calculates the geometric curvature distribution along the hole depth z_z direction based on the borehole trajectory function x(z) determined in step S2 with arc drilling. The geometric curvature κ(z) at any point on the borehole axis is calculated using the second derivative of the trajectory function, and its expression is:

[0074]

[0075] The curvature value κ(z) quantifies the degree of curvature of the borehole at different depths.

[0076] Based on the calculated geometric curvature distribution data, the longitudinal distribution density of the elastic centralizing fins on the outside of the medicine roll is configured differently. The longitudinal distribution density function ρ of the elastic centralizing fins is defined. fin (z), i.e., the number of blades per unit length, is linearly positively correlated with the geometric curvature κ(z). The specific calculation model is as follows:

[0077] ρfin(z)=ρ0+α ga in·κ(z);

[0078] Where ρ0 is the basic fin distribution density of the straight segment, α gain This is the preset distributed gain coefficient.

[0079] Based on the above model, in the arc-forming section or bottom section where the borehole curvature κ(z) is large, the distribution density ρ calculated by the system is... fin (z) Increased. Construction personnel or automated charging equipment can increase the number of elastic centralizing fins installed on the outside of the propellant cartridge in this section. The densely arranged elastic centralizing fins provide higher radial support stiffness, effectively resisting the elastic restoring force and its own weight component generated by the propellant cartridge in a bending state, forcing the propellant cartridge carrier to always be located on the geometric central axis of the arc-shaped borehole.

[0080] This adaptive centering charge structure is physically sized to strictly match the decoupling coefficient requirements of low-disturbance blasting. In practice, the charge carrier is either a 27mm inner diameter PVC pipe filled with emulsion explosive, or a 25mm diameter pre-made emulsion explosive cartridge. The centering support, provided by elastic centering fins, ensures the borehole diameter D is maintained along its entire length. hole With the diameter D of the medicine roll charge The ratio, i.e., the decoupling coefficient K d Constantly satisfying K d The condition is ≥1.5. This structure forms a uniformly thick annular air gap or low-density medium layer between the explosive cartridge and the hole wall, providing geometric assurance for the uniform action of the subsequent explosion stress wave.

[0081] This invention provides a method for precise excavation control with weak disturbance in fractured surrounding rock. Step S5 mainly involves the differentiated configuration of the charging structure and the precise control of the detonation sequence for long holes and short holes, so as to achieve directional guidance and energy blocking of stress waves.

[0082] In this step, a very weak charge or air-gap charge strategy is implemented for short holes. Specifically, the total charge amount in a single short hole is controlled to be one-third to one-quarter of the total charge amount in a single long hole. Simultaneously, the charge section in the short hole does not fill the entire borehole, but is mainly distributed in the bottom area. This charge distribution method aims to limit the blasting damage range of the short hole, ensuring that its energy is primarily used to create fractures in specific areas rather than ejecting large amounts of rock.

[0083] Regarding the control of detonation timing, this method sets the detonation time of the short hole to be strictly earlier than the detonation time of the adjacent long hole. The lag time difference ΔT between the two is based on the spatial distance D between the long and short holes. LS and the longitudinal wave velocity C of the rock mass p The lag time difference ΔT must be calculated and determined. ΔT ≥ D must satisfy the condition ΔT ≥ D. LS / C p This is to ensure that the physical effects of short-hole blasting have been formed and stabilized before the main shock wave generated by long-hole blasting arrives.

[0084] After the short hole is detonated first, due to its specific spatial location (between the long hole and the design outline) and the controlled charge amount, a microfracture zone with a specific curvature will be pre-formed in the shallow surrounding rock area between the long hole and the design outline. This microfracture zone physically represents an interruption of the rock mass continuity, thus forming a significant wave impedance mismatch interface, i.e., a stress wave cutoff interface.

[0085] Subsequently, the main excavation charge inside the long hole was detonated. The high-energy blast shock wave generated by the long hole blasting propagated in all directions. When the shock wave reached the micro-fracture zone pre-fabricated by the short holes, reflection and transmission attenuation occurred due to the abrupt change in wave impedance. Most of the shock wave energy was reflected back into the excavation cavity, enhancing the rock fragmentation effect; while the energy transmitted through this interface was significantly attenuated, thus significantly reducing disturbance and damage to the surrounding rock outside the design outline, achieving precise shaping with minimal disturbance.

[0086] This invention provides a method and apparatus for precise excavation control with minimal disturbance in fractured surrounding rock. The following description uses the excavation operation of a Class IV fractured surrounding rock section of a single-track railway tunnel as an example. The tunnel's designed outline radius is 6 meters, and the designed cycle advance is 3 meters.

[0087] During the construction preparation phase, on-site technicians first used the electric spray paint stick 1 to mark the holes. The operator held the electric spray paint stick 1 and used the laser rangefinder 5 and laser range display 4 at the top to measure the unevenness and distance of the working face. Simultaneously, they observed the data from the tilt sensor 3 installed on the outer wall of the electric spray paint stick 1 to ensure that the stick's posture matched the designed external angle. Triggering the electric switch 2 caused the paint can 11 inside the base 6 to spray out the marking points.

[0088] Based on the parametric model calculation in step S1, the starting point of the long hole is set to be 25 cm inside the design outline, and the starting point of the short hole is set to be 10 cm inside the design outline. Using the above device, the double marking of the peripheral eyes of the entire cross section is quickly completed, with long holes and short holes arranged alternately.

[0089] Drilling operations then commenced. The drilling rig employed a flexible drill rod to drill at the marked points. When drilling the long hole numbered L-5 at the left arch position, the drilling rig control system applied lateral preload to the drill rod, guiding it along a predetermined arc trajectory. When the hole reached a depth of 3 meters from the bottom, the drill rod returned to a horizontal tangential state, and the final hole point accurately fell on the designed contour line.

[0090] During drilling, the system simultaneously executed the mechanical feedback in step S3. Monitoring data showed that in the 1.5-2.0 meter depth range of hole L-5, the peak lateral force required to maintain drill pipe bending was significantly lower than the baseline value, with a ratio of only 0.6. The system determined that a weak and fractured interlayer existed in this area and subsequently calculated a surrounding rock correction factor of 0.65. Based on this feedback, the on-site charging command adjusted the originally planned 32 mm diameter rock emulsion explosive for this hole to a 25 mm diameter high-velocity small-diameter explosive cartridge, reducing the charge linear density.

[0091] During the loading stage, operators assemble the propellant cartridges according to the requirements of step S4. Considering the significant curvature of the front section of hole L-5, the longitudinal distribution density of the elastic centralizing blades at the front of the cartridge is increased before it enters the hole, reducing the spacing from the conventional 50 cm to 20 cm. After loading, the elastic centralizing blades effectively support the cartridge, suspending it in the center of the hole, ensuring a decoupling coefficient greater than 1.5 and uniform distribution.

[0092] Finally, coordinated blasting was implemented. Only one explosive cartridge was loaded at the bottom of the short holes, using an air-gap structure. In the blasting network design, the short holes were connected to the MS1 detonator section, and adjacent long holes were connected to the MS3 detonator section. After detonation, the short holes detonated approximately 50 milliseconds before the long holes, forming a connected micro-fracture zone inside the outline. Subsequently, the long holes detonated, and the explosive gases and shock waves were reflected at the fracture zone, preventing excessive damage to the remaining surrounding rock. Post-blast debris removal revealed a smooth and flat blasted layer with a residual hole rate exceeding 90%, and no obvious over- or under-excavation.

Claims

1. A method for controlling precise excavation with minimal disturbance in fractured surrounding rock, characterized in that, Includes the following steps: S1. Establish a local spatial rectangular coordinate system on the working face. Based on the strategy of conjugate of long and short boreholes, use a parametric model to calculate the three-dimensional coordinate parameters of the long and short boreholes. The parameters include the starting point position, drilling depth and inner offset distance. S2. Based on the three-dimensional coordinate parameters, perform peripheral drilling, use flexible drill rods to perform arc drilling, and apply lateral pre-tightening force to the drill rod to make the drill rod elastically bend until the bottom tangent direction of the hole is parallel to the tunnel design axis. S3. During the arc drilling process, the peak value of the lateral force required to maintain the bending of the drill rod is monitored in real time, and the peak value of the lateral force is used as a feedback parameter to characterize the local mechanical properties of the surrounding rock, and the charge linear density of the corresponding borehole is dynamically corrected. S4. Construct an adaptive centering charge structure that is physically matched with the borehole geometry. Based on the curvature distribution of the borehole axis formed by arc drilling, adjust the longitudinal distribution density of the elastic centralizing wing on the outside of the charge cartridge to keep the charge cartridge centered in the arc-shaped borehole. S5. Implement long and short hole stress wave guided blasting, control the short hole to detonate before the long hole, and use the micro-fracture zone formed between the long hole and the design outline by the short hole detonation as the stress wave cutoff interface to attenuate the impact energy of the long hole blasting on the remaining surrounding rock.

2. The method for controlling precise excavation with weak disturbance in fractured surrounding rock according to claim 1, characterized in that, In step S1, the long and short borehole conjugate strategy specifically includes: The long holes are designated as the main excavation holes, and the short holes as guide holes; Based on the excavation progress and the positioning distance of the drilling equipment, the radial inward offset distance of the starting point of the long hole is calculated so that the ending point of the long hole at the predetermined depth falls on the design outline. The starting point of the short hole is set between the starting point of the long hole and the design outline. The drilling trajectory of the short hole and the drilling trajectory of the long hole form a hyperboloid tangent structure in space, and the drilling depth of the short hole is less than the drilling depth of the long hole.

3. The method for controlling precise excavation with weak disturbance in fractured surrounding rock according to claim 1, characterized in that, In step S2, the trajectory control of the arc drilling must meet the following boundary conditions: The coordinates of the hole starting point are located inside the design outline; The coordinates of the final hole point coincide with the design outline. The slope of the tangent line of the drilling trajectory at the end point approaches zero to eliminate the external insertion angle at the bottom of the hole.

4. The method for controlling precise excavation with weak disturbance in fractured surrounding rock according to claim 1, characterized in that, In step S3, the dynamic correction of the charge linear density of the corresponding borehole specifically includes: Set the reference lateral force required for the drill pipe to reach a predetermined bend under standard surrounding rock conditions; Calculate the ratio of the measured peak lateral force to the reference lateral force, and determine the surrounding rock correction coefficient based on the ratio and the lithology sensitivity index; The actual charge linear density is obtained by multiplying the baseline charge linear density by the surrounding rock correction factor; if the actual charge linear density is lower than the preset threshold, the charge structure is switched to a finished charge cartridge with a smaller diameter.

5. The method for controlling precise excavation with weak disturbance in fractured surrounding rock according to claim 1, characterized in that, In step S4, adjusting the longitudinal distribution density of the external elastic straightening fins of the drug roll specifically involves: Calculate the geometric curvature of the borehole trajectory along the depth direction; The longitudinal distribution density of the elastic straightening wing is set to be positively correlated with the geometric curvature. The wing density is increased in the hole section with greater curvature, while the basic wing density is maintained in the straight section. The elastic straightening wing supports the propellant cartridge, ensuring that the ratio of the borehole diameter to the propellant cartridge diameter remains within a preset decoupling coefficient range throughout the entire length.

6. The method for controlling precise excavation with weak disturbance in fractured surrounding rock according to claim 5, characterized in that, In the adaptive centering charge structure, the charge roll is made of PVC pipe with an inner diameter of 27mm and filled with emulsion explosive or finished emulsion explosive with a diameter of 25mm, and the decoupling coefficient is greater than 1.

5.

7. The method for controlling precise excavation with weak disturbance in fractured surrounding rock according to claim 1, characterized in that, In step S5, the formation mechanism of the stress wave cutoff interface is as follows: The short hole adopts a very weak charge or air-spaced charge structure; After the short hole is detonated first, a micro-crack zone with a specific curvature is prefabricated in the shallow region between the long hole and the design outline. The micro-crack zone serves as a wave impedance mismatch interface to reflect and attenuate the shock wave generated by the long hole detonation.

8. The method for controlling precise excavation with weak disturbance in fractured surrounding rock according to claim 1, characterized in that, In step S5, the timing control of the long and short eye stress wave guided coordinated blasting must meet the following requirements: The detonation time of adjacent long holes lags behind that of short holes, and the lag time difference is determined based on the distance between the long and short holes and the longitudinal wave velocity of the rock mass.

9. The method for controlling precise excavation with weak disturbance in fractured surrounding rock according to claim 7, characterized in that, The charge amount in the short hole is one-third to one-quarter of the charge amount in the long hole, and the charge section in the short hole is mainly distributed in the bottom area of ​​the hole.

10. A low-disturbance precision excavation construction device for fractured surrounding rock, characterized in that, include: An electric spray paint pole (1) is electrically connected to an electric switch (2) on its outer wall, an angle sensor (3) on its outer wall, a laser rangefinder (4) on its top end, a laser rangefinder (5) on its top end, a base (6) fixedly connected to its top end, two fixing rings (7) fixedly connected to its top end, a fastening plate (8) fixedly connected to one end of each fixing ring (7), a bolt (9) threaded between the fastening plates (8), a nut (10) threaded to one end of each bolt (9), a paint can (11) slidably connected inside the base (6), and the outer wall of the paint can (11) slidably connected between the fixing rings (7).

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