Construction method for removing undercut part of tunnel by adopting static hydraulic blasting

Abstract

The invention relates to the technical field of tunnel construction, and discloses a construction method for removing an undercut part of a tunnel by adopting static hydraulic blasting, which comprises the following steps of: blasting the tunnel, and carrying out slag tapping operation for the first time; scanning a tunnel excavation area by three-dimensional laser, and identifying the position, shape and volume of an under-excavation area; according to analysis of the position, the shape and the volume of the undercut area, static hydraulic blasting design is conducted on the undercut area; setting out and drilling according to design; and a static hydraulic splitting rod is installed for static hydraulic splitting blasting, secondary deslagging operation is conducted, and the contour surface is cleaned. Static hydraulic splitting is applied to tunnel under-excavation part removal, the advantages of safety, environmental protection, flexibility and accuracy of a static hydraulic blasting device can be well played, secondary disturbance of secondary blasting of a general under-excavation part to surrounding rock is reduced, and the problems that an existing tunnel under-excavation treatment method is low in efficiency, large in labor intensity and high in efficiency are solved. And vibration or disturbance is easily generated to cause damage to subsequent processes.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel construction, in particular to a construction method for removing an undercut portion of a tunnel by adopting static hydraulic blasting. Background Art

[0002] During tunnel drilling and blasting construction, controlling the excavation profile directly impacts construction quality, safety, and economic efficiency. Using the tunnel's designed excavation profile as a reference, the portion of the actual excavation section that exceeds the designed profile is called overbreak, while the portion that falls short of the designed profile is called underbreak. Overbreak increases the concrete consumption and support costs of the secondary lining, while underbreak, if not addressed promptly, can impact subsequent construction progress and even lead to even greater overbreak due to supplemental blasting, further increasing construction costs. Both overbreak and underbreak can directly impact tunnel construction safety, cost, and quality, and increase the difficulty of subsequent construction.

[0003] Currently, the main methods for dealing with undercut tunnels include manual pneumatic pick crushing, mechanical hydraulic hammer crushing, or supplementary blasting. However, these methods have the following drawbacks: 1. Manual pneumatic picks have low crushing efficiency, high labor intensity, and it is difficult to ensure the flatness of the excavation profile; 2. Mechanical hydraulic hammer crushing will produce large vibrations, which may cause damage to the surrounding rock and initial support; 3. Although supplementary blasting can quickly remove the under-excavated part, the blasting shock wave will disturb the surrounding rock again, resulting in greater over-excavation and generating a large amount of dust and noise, affecting the construction environment and personnel health. Summary of the Invention

[0004] The present invention provides a construction method for removing undercut sections of tunnels using static hydraulic blasting. By applying static hydraulic splitting to the removal of undercut sections, the advantages of the static hydraulic blasting device, such as safety, environmental friendliness, flexibility, and precision, are fully utilized, reducing the secondary disturbance of surrounding rock caused by secondary blasting of large undercut sections. Static hydraulic blasting effectively controls the excavation fracture surface, resulting in a smooth tunnel excavation profile and preventing overcut after secondary blasting of undercut sections. Construction efficiency is high, and large-scale blasting dust is eliminated, which is beneficial for rapid construction and ensuring the health of construction workers. The present invention expands the application area of ​​the static hydraulic splitting device, effectively improving the efficiency of identifying and treating undercut sections, and providing a new technical means for ensuring safe and efficient tunnel construction. This addresses the technical issues of existing methods for treating undercut sections, such as low efficiency, high labor intensity, and the susceptibility to vibration or disturbance that can damage subsequent processes.

[0005] The present invention provides a construction method for removing undercut parts of a tunnel by using static hydraulic blasting, comprising the following steps: S100, tunnel blasting, and performing a first slag removal operation; S200, three-dimensional laser scanning of the tunnel excavation area to identify the position, shape, and volume of the undercut area; S300, designing static hydraulic blasting for the undercut area based on an analysis of the position, shape, and volume of the undercut area; S400, staking out and drilling holes according to the design; and S500, installing a static hydraulic splitting rod, performing static hydraulic splitting blasting, performing a second slag removal operation, and cleaning the contour surface.

[0006] Furthermore, step S200 specifically includes: S201, arranging sites for three-dimensional laser scanning to facilitate scanning data acquisition and unify the coordinate system and perform coordinate system conversion; S202, comparing the actual excavation point cloud data with the point cloud data of the designed contour surface, analyzing the location of the under-excavation of the tunnel, calculating the shape and volume of the over-excavation and under-excavation, and generating a three-dimensional drawing of the under-excavation part.

[0007] Furthermore, step S201 specifically includes: after the tunnel excavation area is slag-removed and leveled, a ground-based three-dimensional laser scanner is used to perform a three-dimensional laser scan on the tunnel excavation area to obtain tunnel point cloud data, the tunnel point cloud is pre-processed to obtain the actual excavation contour point cloud of the tunnel, and the actual excavation contour point cloud of the tunnel is converted from a dedicated format to a universal point cloud format, and then established and converted to a tunnel surrounding rock over-excavation and under-excavation analysis coordinate system.

[0008] Furthermore, step S300 specifically includes: when designing static hydraulic blasting for the under-excavated area, the characteristics of static hydraulic splitting should be considered, and sufficient hydraulic splitting points should be arranged along the tunnel design contour to ensure that a tunnel contour surface that meets the clearance requirements can be formed after static hydraulic splitting blasting; when designing static blasting, the drilling direction and the splitting rod arrangement should be as parallel as possible to the tunnel axis direction.

[0009] Furthermore, when the undercut area of ​​the tunnel is large, drilling parallel to the tunnel excavation face is used as an auxiliary method; or when the undercut area of ​​the tunnel is too large and it is difficult to complete static hydraulic splitting in one go, a layered multiple static hydraulic splitting blasting design is adopted to facilitate the cleaning of the undercut area of ​​the tunnel.

[0010] Furthermore, when designing static hydraulic blasting, the method of adding auxiliary holes is adopted to improve the static liquid blasting effect; the auxiliary holes are through holes without static hydraulic splitting rods and are at a certain distance from the splitting point, and the auxiliary holes and the splitting point are arranged in an intermittent manner.

[0011] Furthermore, step S500 specifically includes: after drilling and cleaning the hole, installing a static hydraulic splitting rod to perform static hydraulic splitting blasting; according to the static blasting design and the drilling depth, selecting a static hydraulic splitting rod of appropriate length, moving and lifting it through a small self-propelled scissor-type lifting platform, installing the static hydraulic splitting rod into the predetermined drill hole, and fixing the static hydraulic splitting rod on the surrounding stable surrounding rock; after the construction personnel and machinery are evacuated to a safe location, performing static hydraulic splitting blasting; after the static blasting is completed, removing the static hydraulic splitting rod and storing it for next use.

[0012] Furthermore, a detachable hydraulic expansion fixing device is used to fix the static hydraulic splitting rod on the surrounding stable surrounding rock; the detachable hydraulic expansion fixing device includes a metal component, a pin, a hydraulic power device and a spring component, the first end of the metal component has a conical protrusion, and two metal components are provided; the two metal components are cross-stacked and pinned together at the middle part by a pin to form a scissor-type structure, the hydraulic power device presses the second end of the metal component and stretches the spring component to open the scissor-type structure, and the protruding end of the metal component squeezes the wall of the surrounding rock hole to stabilize the opening of the scissor-type structure and stabilize the force, and then the static hydraulic splitting rod is fixed by the connecting rope; when the static splitting blasting is completed, the static hydraulic splitting rod needs to be removed.

[0013] Furthermore, the force unloading and recovery process of the detachable hydraulic expansion fixing device is as follows: the hydraulic power device unloads and recovers the force, and the spring component contracts and pulls to close the scissor-type structure, thereby removing the static hydraulic splitting rod.

[0014] Furthermore, step S100 is specifically as follows: blasting design is performed for tunnel blasting, and smooth blasting or pre-splitting blasting is used as much as possible when selecting a blasting scheme, thereby helping to reduce over-excavation and under-excavation; when arranging blastholes and calculating blasting parameters, the cross-sectional dimensions, geological conditions, and construction schedule requirements of the tunnel are fully considered; during the blasting process, strict blasting monitoring and quality control are performed, a blasting monitoring plan is formulated, a blasting construction quality control system is established, and key links such as drilling accuracy, charge quality, and detonation network connection are strictly monitored and controlled to ensure that the blasting effect meets the design requirements; when performing slag removal operations after the blasting is completed, the middle part should be cleaned first, and then expanded to both sides to avoid blockage that affects the construction progress.

[0015] The present invention has the following beneficial effects: 1. Improve construction safety: By replacing traditional blasting operations with static hydraulic splitting, secondary disturbance of the surrounding rock and initial support structure caused by blasting vibration is avoided, thus reducing construction safety risks.

[0016] 2. Improve construction accuracy: Combined with 3D laser scanning technology, the location, shape and volume of under-excavated areas can be accurately identified, making static hydraulic blasting design more targeted, effectively controlling the flatness of the excavation contour surface, and reducing over-excavation and under-excavation.

[0017] 3. Optimize construction efficiency: Use static hydraulic splitting rods for precise splitting, avoiding the inefficient operation of traditional manual pneumatic picks or mechanical crushing, shortening the under-excavation processing time, and improving the overall construction progress.

[0018] 4. Improve the construction environment: The static hydraulic splitting process has no blasting dust and noise pollution, which improves the working environment, is beneficial to the health of construction workers, and reduces the impact on the surrounding environment.

[0019] 5. Reduce project costs: By precisely controlling the excavation profile, over-excavation or secondary blasting caused by improper under-excavation treatment is reduced, the additional consumption of materials such as concrete is reduced, and construction costs are saved.

[0020] 6. Expanding technical applications: Combining static hydraulic splitting technology with tunnel underbreak treatment provides a feasible solution for the application of this device in tunnel engineering and enriches the technical means of tunnel construction.

[0021] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings: Figure 1 1. It is a flow chart of a construction method for removing an undercut portion of a tunnel using a static hydraulic blasting device according to a preferred embodiment of the present invention; Figure 2 This is a schematic diagram of a drilling arrangement for static hydraulic blasting drilling design according to a preferred embodiment of the present invention; Figure 3 This is a schematic structural diagram of a static hydraulic splitting rod with a fixing device according to a preferred embodiment of the present invention; Figure 4 This is a schematic structural diagram of a detachable hydraulic expansion and fixing device according to a preferred embodiment of the present invention; Figure 5 It is a structural schematic diagram of a small self-propelled scissor-type lifting platform according to a preferred embodiment of the present invention.

[0023] Legend: 1. Tunnel outline; 2. Tunnel undercut area; 3. Splitting point drilling; 4. Auxiliary hole; 5. Hydraulic splitting rod body; 6. Hydraulic top block; 7. Mounting handle; 8. Splitting rod hydraulic oil pipe; 9. Connecting rope; 10. Removable hydraulic expansion and fixing device; 11. Surrounding rock hole wall; 12. Horizontally movable fixed vehicle body; 13. Scissor-type hydraulic lifting system; 14. Working platform.

[0024] 101. Metal component with a conical protrusion; 102. Pin; 103. Hydraulic power unit; 104. Spring component; 105. Hydraulic oil pipe of the fixing device. DETAILED DESCRIPTION

[0025] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0026] Figure 1 1. It is a flow chart of a construction method for removing an undercut portion of a tunnel using a static hydraulic blasting device according to a preferred embodiment of the present invention; Figure 2 This is a schematic diagram of a drilling arrangement for static hydraulic blasting drilling design according to a preferred embodiment of the present invention; Figure 3 This is a schematic structural diagram of a static hydraulic splitting rod with a fixing device according to a preferred embodiment of the present invention; Figure 4 This is a schematic structural diagram of a detachable hydraulic expansion and fixing device according to a preferred embodiment of the present invention; Figure 5 It is a structural schematic diagram of a small self-propelled scissor-type lifting platform according to a preferred embodiment of the present invention.

[0027] like Figure 1As shown, the construction method of this embodiment for removing the under-excavated portion of a tunnel by using static hydraulic blasting includes the following steps: S100, tunnel blasting, and performing the first slag removal operation; S200, three-dimensional laser scanning of the tunnel excavation area to identify the position, shape, and volume of the under-excavated area; S300, designing static hydraulic blasting for the under-excavated area based on the analysis of the position, shape, and volume of the under-excavated area; S400, staking out and drilling holes according to the design; S500, installing static hydraulic splitting rods, performing static hydraulic splitting blasting, performing the second slag removal operation, and cleaning the contour surface. The present invention adopts a construction method for removing undercut sections of tunnels using a static hydraulic blasting device. Three-dimensional laser scanning technology is used to accurately identify the location, shape, and volume of undercut areas, providing an accurate basis for subsequent static hydraulic blasting design and ensuring targeted undercut treatment. Static hydraulic splitting replaces traditional blasting or mechanical crushing, avoiding secondary damage to surrounding rock and initial support structures caused by blasting shock waves or vibrations, thus facilitating tunnel stability. Undercut treatment and tunnel blasting construction are carried out in stages, with excavation and undercut treatment separated through two slag removal operations, improving construction organization efficiency. The precise splitting action of the static hydraulic splitting rod forms a smooth excavation profile, effectively controlling over- and undercut phenomena and reducing subsequent finishing work. The static hydraulic splitting process eliminates blasting dust and noise pollution, creating a safer and cleaner construction environment and protecting the health of workers. Precise control of the excavation profile reduces material waste and rework caused by improper undercut treatment, saving construction costs. The combination of static hydraulic splitting technology with tunnel undercut treatment provides a feasible solution for the innovative application of this device in tunnel engineering. By combining 3D laser scanning technology with static hydraulic splitting technology, a complete solution for treating under-excavation in tunnels has been developed. While ensuring construction accuracy, it effectively reduces disturbance to the surrounding rock, improves construction efficiency, and enhances the working environment, providing a new, safe, efficient, and economical method for treating under-excavation in tunnel projects.

[0028] Furthermore, undercut areas in tunnels often have large free-surface areas. In terms of rock mechanical properties, the tensile strength of rock is typically much lower than its compressive strength. The present invention's construction method for removing undercut areas of tunnels using static hydraulic blasting utilizes the low tensile strength of rock, easily splitting the rock from within, thereby achieving energy-efficient and efficient treatment of undercut areas. Static hydraulic splitting equipment (including static hydraulic splitting rods) is compact, lightweight, and flexible, making it ideal for use in confined spaces. During the hydraulic splitting process, it relies on reaction forces to maintain its balance, resulting in high stability. The hydraulic splitting rock-breaking process does not significantly disturb the surrounding rock or the surrounding environment, making it suitable for rock-breaking and excavation projects under special construction conditions. It is a non-blasting rock-breaking method with a simple working principle and convenient operation. This is very suitable for tunnel projects with limited working space and high disturbance control requirements. In particular, when under-excavation occurs during tunnel drilling and blasting, the stability of the under-excavated area drops sharply after the blasting disturbance. Secondary blasting is very likely to cause accidents such as falling blocks, over-excavation, and collapse. Therefore, the hydraulic splitting technology, which is lightweight, flexible, and has no blasting disturbance, is very suitable for dealing with under-excavation in tunnels.

[0029] Furthermore, the present invention utilizes static hydraulic blasting to remove undercut areas in tunnels. The introduction of 3D laser scanning technology allows for rapid identification and location of undercut areas, improving construction efficiency. 3D laser scanning allows for rapid and accurate analysis of the shape and volume of undercut areas, greatly facilitating subsequent static blasting design. Based on the undercut map generated by 3D laser scanning, a network layout for static hydraulic fracturing can be quickly designed, eliminating the need for secondary measurements of undercut areas using traditional total stations and levels. This improves measurement accuracy while optimizing the processing flow and enhancing the efficiency of identifying and measuring undercut areas.

[0030] In this embodiment, step S200 specifically includes: S201, arranging sites for three-dimensional laser scanning to facilitate scanning data acquisition and unify the coordinate system and perform coordinate system conversion; S202, comparing the actual excavation point cloud data with the point cloud data of the designed contour surface, analyzing the location of the under-excavation in the tunnel, calculating the shape and volume of the over-excavation and under-excavation, and generating a three-dimensional drawing of the under-excavation area. By optimizing the layout of scanning stations, the scanned data ensures complete coverage of the excavation area. Coordinate system conversion is unified, eliminating errors in data splicing from multiple stations and providing high-precision basic data for underbreak analysis. Through point cloud data comparison technology, deviations between the actual excavation surface and the designed contour surface are digitally analyzed to accurately identify underbreak locations, overcoming the subjectivity and limitations of traditional manual inspection. Generated 3D drawings of underbreak areas provide intuitive spatial references for subsequent static hydraulic blasting design, making drilling layout and splitting scheme design more targeted. Point cloud data analysis is used to calculate underbreak volume, providing a quantitative basis for construction resource allocation (such as the number of splitting rods and drilling depth), avoiding resource waste or shortages. The established unified coordinate system and 3D model serve as the basis for construction quality traceability, achieving a closed-loop management system of "scanning-analysis-processing-review." Through standardized data acquisition and intelligent analysis, traditional empirical judgments are transformed into quantitative decisions based on 3D point clouds, providing precise spatial parameters and visual guidance for subsequent static hydraulic blasting. This is the core technical support for ensuring the accuracy of underbreak treatment.

[0031] The site layout for 3D laser scanning is as follows: 1. Site Planning Longitudinal spacing: one station is arranged every 20m-30m along the tunnel axis (based on the effective distance of the scanner, such as 20m spacing for a 30m range instrument), and the overlapping area of ​​adjacent stations is ≥30%.

[0032] Horizontal position: The station is placed centrally on the tunnel floor to avoid scanning blind spots (vault / side wall blind spots) caused by proximity to the side walls.

[0033] 2. Control point layout ≥3 reflective targets (or artificial markers) are arranged around each site, and their three-dimensional coordinates are measured by a total station (with an accuracy of ±1 mm) as the basis for point cloud stitching.

[0034] 3. Scan parameter setting Resolution: 1mm-3mm point spacing (encrypted to 1mm in key areas, 3mm in general areas).

[0035] Scanning range: 360° horizontal coverage, ±30° vertical coverage (from arch top to invert).

[0036] Denoising mode: Enables dynamic filtering algorithm to remove interference points such as dust and equipment in real time.

[0037] 4. Environmental Adaptation Measures Lighting compensation: Add auxiliary light sources (such as LED cold light) in areas with insufficient light.

[0038] Dust control: Use 1550nm wavelength laser (the ability to penetrate dust is better than 905nm).

[0039] The site layout for 3D laser scanning eliminates blind spots in traditional single-station scanning (such as the junction of arch feet and inverted arches) through overlapping multi-station layout. Control point-assisted stitching ensures that the overall point cloud error is ≤3mm (uncontrolled stitching error is ≥10mm). Under the standardized process, the single-station scanning time is ≤5 minutes (including station setup and target measurement). The high-density point cloud (≥500 points / m²) can identify contour deviations of ≥5mm.

[0040] In this embodiment, step S201 specifically includes: after the tunnel excavation area has been slag-removed and leveled, a terrestrial 3D laser scanner is used to perform a 3D laser scan of the tunnel excavation area to obtain tunnel point cloud data. The tunnel point cloud is preprocessed to obtain a point cloud of the actual tunnel excavation contour. The actual tunnel excavation contour point cloud is converted from a dedicated format to a universal point cloud format, and then a coordinate system is established and converted to analyze the tunnel surrounding rock over- and under-break. Scanning after slag removal and leveling eliminates interference from the slag pile, obtaining point cloud data that truly reflects the excavation contour and avoiding measurement errors caused by on-site debris. Converting the dedicated point cloud format to a universal format enables data interoperability between different software platforms, providing a standardized data foundation for subsequent multi-disciplinary collaborative analysis. Coordinate system conversion to a dedicated coordinate system for over- and under-break analysis eliminates baseline differences between the design model and on-site scan data, ensuring the mathematical accuracy of comparative analysis. The preprocessing process removes noise points, fills in missing data, and improves point cloud quality, making subsequent over- and under-break analysis more reliable. This forms a standardized data processing chain of "scanning-conversion-preprocessing-coordinate unification," providing structured data support for intelligent construction. Through standardized data collection and processing procedures, a precise channel connecting on-site entities and digital models is constructed, which is a prerequisite for achieving high-precision over-excavation and under-excavation analysis, and provides a reliable spatial data foundation for subsequent intelligent decision-making.

[0041] In this embodiment, step S300 specifically includes: when designing static hydraulic blasting for the undercut area, the characteristics of static hydraulic splitting should be considered. Sufficient hydraulic splitting points should be arranged along the tunnel design contour to ensure that a tunnel contour surface that meets the clearance requirements can be formed after static hydraulic splitting blasting; when designing static blasting, the drilling direction and splitting rod arrangement should be as parallel as possible to the tunnel axis. By arranging splitting points at a sufficient density along the design contour, the rock splitting surface accurately conforms to the design linear shape, effectively ensuring that the tunnel clearance size meets the design requirements; using a drilling arrangement parallel to the tunnel axis, the splitting force is transmitted along the natural joint direction of the rock mass, improving rock splitting efficiency and reducing energy loss; directional splitting design can control the direction of rock fracture propagation and avoid lateral compression damage to the completed support structure; a special design based on splitting characteristics makes the effect of each splitting point predictable, achieving a visual preview of the undercut treatment; and by scientifically arranging splitting points, the number of drill holes and the amount of splitting rods used can be reasonably controlled while ensuring the treatment effect. Through special design that conforms to the mechanical characteristics of static hydraulic splitting, the optimal balance between contour accuracy control and construction economy during under-excavation processing is achieved, which is the core technical link to ensure the final forming quality.

[0042] When designing static hydraulic blasting for undercut areas, the characteristics of static hydraulic fracturing should be considered. Sufficient hydraulic fracturing points should be arranged along the tunnel design contour to ensure that a tunnel contour surface that meets the clearance requirements can be formed after static hydraulic fracturing blasting. Specifically: 1. Splitting point positioning arrangement (1) Draw a reference line 50 mm inside the tunnel design outline to serve as the axis for the splitting point arrangement; (2) Determine the spacing of splitting points according to the hardness of the rock mass: hard rock mass (uniaxial compressive strength > 60 MPa): 300 mm-400 mm; medium-hard rock mass (30-60 MPa): 400 mm-500 mm; (3) For under-excavated areas with a thickness greater than 500 mm, double-row staggered arrangement is adopted: Inner row holes: 50mm from the contour line, hole depth = undercut thickness + 50mm; External row holes: 150mm from the contour line, hole depth = under-excavation thickness × 0.7mm; Row spacing: 100 mm, arranged in a plum blossom shape; 2. Drilling parameter control (1) Drilling diameter: 2mm-3mm larger than the splitting rod diameter (conventional 42mm-45mm) (2) Drilling angle: parallel to the tunnel axis, with the deviation controlled within ±2° (3) Hole quality requirements: hole depth error ≤ 10 mm; hole position deviation ≤ 5 mm; hole wall is intact without hole collapse; 3. Auxiliary system configuration (1) Add an auxiliary hole between every three splitting points: the diameter is 42 mm; the depth is 0.8 times the average depth of the adjacent splitting holes; (2) Setting stress guide holes: located at the edge of the undercut area; with an angle of 20°-30° with the main joint; Through precise hole network design, dynamic parameter adaptation and strict process control, the flatness error of the contour surface after static hydraulic splitting is ensured to be ≤30㎜, while the rock block crushing size is controlled within the ideal range of 300㎜-500㎜, taking into account both construction efficiency and forming quality.

[0043] In this embodiment, when the tunnel undercut area 2 is large, supplementary drilling is performed parallel to the tunnel excavation face. Alternatively, when the tunnel undercut area 2 is too large to complete static hydraulic fracturing in a single pass, a layered, multiple-step static hydraulic fracturing blasting design is employed to facilitate the clearing of the tunnel undercut area 2. By adding supplementary drilling holes parallel to the tunnel excavation face, a multi-directional fracturing network is formed, effectively decomposing the structural integrity of large rock masses and overcoming the limitations of traditional single-directional fracturing. The layered, multiple-step fracturing design treats large undercut areas in stages, avoiding energy dispersion or contour loss caused by a single fracturing pass and ensuring high-quality fracturing at each layer. The multi-directional drilling arrangement creates a more rational stress transmission system, causing the rock mass to fracture progressively in a predetermined sequence and direction, reducing the risk of secondary damage to the surrounding rock. Differentiated design schemes are employed for undercut areas of varying sizes, ensuring both efficient treatment of small undercuts and the feasibility of large undercuts. Layered treatment reduces the energy of a single blast, minimizing the risk of sudden rock collapse and providing a safer operating environment for construction personnel. Through the coordinated design of multi-directional drilling and layered splitting, the technical bottleneck of static hydraulic splitting technology in large-volume under-excavation treatment has been broken through, and the applicability and processing capacity of the technology have been significantly improved while ensuring construction safety.

[0044] In this embodiment, during the static hydraulic blasting design, the addition of auxiliary holes 4 is employed to enhance the effectiveness of static hydraulic blasting. Auxiliary holes 4 are through-holes located at a certain distance from the splitting point without static hydraulic splitting rods. Auxiliary holes 4 are arranged in a skipped pattern with intervals between them and the splitting point. Acting as free surfaces, these holes alter the stress transfer path within the rock mass, allowing the tensile stress generated at the splitting point to more easily propagate in the desired direction, significantly enhancing the penetration of the primary splitting plane. The skipped-hole arrangement forms a stress-guiding network, ensuring directional fracture along the designed contour and preventing random cracks from damaging the remaining rock mass. The auxiliary holes 4 release local confining pressure, reducing the rock mass's resistance to cracking and concentrating the splitting rod's energy on the primary fracture plane, thereby reducing ineffective energy consumption. The synergistic effect of the auxiliary holes 4 and the splitting holes produces staggered cracks, which promote the decomposition of the rock mass into medium-sized fragments suitable for removal, avoiding the generation of oversized rock fragments or excessive crushing. The skipped-hole arrangement creates multiple stress release points, allowing adjacent systems to complete rock fragmentation even if a single splitting point fails, ensuring construction continuity. By constructing a scientific hole network system, the reliability, economy and contour control accuracy of static hydraulic blasting are significantly improved without adding splitting equipment.

[0045] Furthermore, when designing rock-breaking excavation for hard rock tunnels or underground structures, adding holes can effectively improve the limited free surface of deep rock. The presence of holes changes the stress field within the rock mass and guides the propagation of rock cracks, further enhancing the rock-breaking effect. Therefore, when designing static hydraulic fracturing, adding appropriate auxiliary holes can exploit the stress concentration phenomenon of the hole effect and the mechanical properties of hard rock with low tensile strength to achieve directional expansion fracture. Adding auxiliary holes not only helps reduce the use of static hydraulic splitting rods, but also facilitates precise control of the tunnel contour by hydraulic splitting to remove undercut areas.

[0046] In this embodiment, step S500 specifically includes: after drilling and cleaning the hole, installing a static hydraulic splitting rod to perform static hydraulic splitting blasting; according to the static blasting design and the drilling depth, selecting a static hydraulic splitting rod of appropriate length, moving and lifting it through a small self-propelled scissor-type lifting platform, installing the static hydraulic splitting rod into the predetermined drill hole, and fixing the static hydraulic splitting rod on the surrounding stable surrounding rock; after the construction personnel and machinery are evacuated to a safe location, static hydraulic splitting blasting is performed; after the static blasting is completed, the static hydraulic splitting rod is removed and stored for next use. Through precise positioning of a small, self-propelled scissor-type lifting platform, the splitting rod and the borehole axis are aligned, avoiding energy loss or contour deviation caused by installation deviation. A remote fixation and personnel evacuation mechanism eliminates the direct threat to personnel from sudden rock fractures during the splitting process, complying with tunnel construction safety regulations. The splitting rod length is matched to the drilling depth to ensure that hydraulic energy fully acts on the target rock mass, avoiding energy waste caused by deep rods in shallow holes or incomplete treatment of short rods in deep holes. Standardized handling and maintenance procedures maintain the structural integrity of the splitting rod, extend the service life of key equipment, and reduce construction costs. A collaborative operation mode of mechanized installation and manual evacuation shortens single-cycle operation time and improves overall construction efficiency. Through standardized and mechanized equipment installation and operation procedures, while ensuring construction safety, the precision and efficiency of static hydraulic splitting operations and standardized equipment management are achieved.

[0047] In this embodiment, a detachable hydraulic expansion fixing device 10 is used to fix the static hydraulic splitting rod on the surrounding stable surrounding rock; the detachable hydraulic expansion fixing device 10 includes a metal component, a pin 102, a hydraulic power device 103 and a spring component 104, the first end of the metal component has a conical protrusion, and two metal components are provided; the two metal components are cross-stacked and pinned together at the middle part by the pin 102 to form a scissors-type structure, the hydraulic power device 103 presses the second end of the metal component and stretches the spring component 104 to open the scissors-type structure, and the protruding end of the metal component squeezes the surrounding rock hole wall 11 to stabilize the opening of the scissors-type structure and stabilize the force, and then the static hydraulic splitting rod is fixed by the connecting rope 9; when the static splitting blasting is completed, the static hydraulic splitting rod needs to be removed. The scissor-type structure forms a stable four-point contact support through the symmetrical expansion of bidirectional metal components, effectively resisting the reaction force during the splitting process and preventing energy loss caused by equipment displacement; the hydraulic power device 103 drives the elastic reset of the spring component 104, so that the device can quickly complete anchoring and release before and after blasting, significantly improving the efficiency of process connection; the conical protrusion design enhances the bite with the irregular surrounding rock hole wall 11, and can still maintain sufficient friction anchoring force even in broken rock; through the flexible fixing method of the connecting rope 9, the axial positioning accuracy of the splitting rod is ensured, and stress concentration damage caused by rigid connection is avoided; the detachable design avoids the channel contamination caused by traditional chemical anchoring, maintains the integrity of the surrounding rock, and reduces the risk of equipment jamming.

[0048] Furthermore, the detachable hydraulic expansion fixing device has a simple structure and is used in conjunction with the static hydraulic splitting rod. Both use a hydraulic system to provide stable and powerful power to maintain the stability of the device. The device uses the lever principle to amplify the displacement of the sawtooth end, thereby improving the degree of engagement between the device and the hole wall, and can better fix the device stably on the stable surrounding rock, thereby ensuring the safety of the static hydraulic splitting rod.

[0049] In this embodiment, the force recovery process of the removable hydraulic expansion fixture 10 is as follows: the hydraulic power unit 103 recovers the force, and the spring member 104 contracts to close the scissor-like structure, thereby removing the static hydraulic splitting rod. The hydraulic power unit 103 gradually relieves pressure and coordinates with the spring member 104 to ensure the smooth closure of the scissor structure, avoiding impact damage to the equipment caused by sudden release. The automatic reset function of the spring member 104 quickly releases the metal member from contact with the hole wall, eliminating the manual tapping and loosening step, and shortening the single operation cycle time. The orderly closure process reduces secondary spalling damage to the hole wall rock mass, maintains the self-stability of the surrounding rock, and creates favorable conditions for possible subsequent repeated drilling. Mechanical automatic reset replaces forced prying, reducing the risk of metal member deformation and extending the service life of key components. The close-range manual intervention required for traditional disassembly is eliminated, avoiding safety hazards caused by rock chip splashing or tool slippage. The synergistic effect of the hydraulic-spring system achieves a safe, efficient, and non-destructive recovery process for the fixture.

[0050] In this embodiment, step S100 is specifically as follows: blasting design is performed for tunnel blasting, and smooth blasting or pre-splitting blasting is used as much as possible when selecting a blasting scheme, thereby helping to reduce over-excavation and under-excavation; when arranging blastholes and calculating blasting parameters, the cross-sectional dimensions, geological conditions, and construction schedule requirements of the tunnel are fully considered; during the blasting process, strict blasting monitoring and quality control are performed, a blasting monitoring plan is formulated, and a blasting construction quality control system is established. Key links such as drilling accuracy, charge quality, and detonation network connection are strictly monitored and controlled to ensure that the blasting effect meets the design requirements; when performing slag removal operations after the blasting is completed, the middle part should be cleaned first and then expanded to both sides to avoid blockage that affects the construction schedule. Smooth blasting or pre-splitting blasting techniques are employed to control blasting energy distribution, significantly reducing damage to the retained rock mass and ultimately preventing over- and under-break. Dynamic blasting parameter design based on cross-sectional dimensions and geological conditions ensures optimal blasting results across varying surrounding rock grades, enhancing the process's universality. A triple quality assurance system encompassing drilling accuracy monitoring, charge control, and detonation network testing ensures standardized blasting operations and eliminates human error. A "center first, side last" slag removal strategy avoids mechanical congestion caused by traditional, unorganized slag removal and maximizes loading equipment efficiency. Quantitative records generated by the blasting monitoring program provide benchmark data for subsequent under-break treatment, forming a closed-loop "blasting-scanning-processing" management chain. Through the systematic implementation of refined blasting design, full-process quality monitoring, and scientific slag removal organization, over- and under-break are effectively controlled from the very beginning, creating favorable conditions for subsequent static hydraulic fracturing.

[0051] During implementation, a construction method for removing undercut sections of tunnels using a static hydraulic blasting device is provided. This method primarily involves using 3D laser scanning technology to rapidly identify undercut areas, designing a layout for static hydraulic splitting rods, proposing the addition of auxiliary holes to improve the efficiency of static hydraulic splitting blasting, designing a removable hydraulic expansion fixture for the static hydraulic splitting rods, and preferably utilizing a small, self-propelled, scissor-type mobile lifting platform to assist in the installation of the static hydraulic splitting device. The specific construction steps are as follows: tunnel blasting to remove slag, 3D laser scanning of the tunnel excavation area, data processing to identify the location and volume of the undercut area, static hydraulic blasting design for the undercut section, drilling according to the design, installing static hydraulic splitting rods for static blasting, removing slag to clean the contour surface, and completing subsequent support operations. Applying the static hydraulic splitting device to remove undercut sections of tunnels effectively leverages its advantages of safety, environmental friendliness, flexibility, and precision, reducing the secondary disturbance of the surrounding rock caused by secondary blasting of large undercut sections. Static hydraulic blasting effectively controls the excavation fracture surface, resulting in a smooth tunnel excavation profile and preventing overexcavation after secondary blasting. This method improves construction efficiency and eliminates the generation of extensive blasting dust, facilitating rapid construction and protecting the health of construction workers. This invention expands the application area of ​​static hydraulic fracturing devices, effectively improving the efficiency of identifying and addressing tunnel underexcavation, and provides a new technical approach for ensuring safe and efficient tunnel construction.

[0052] like Figure 1 As shown, the present invention adopts a static hydraulic blasting device to remove the undercut portion of the tunnel, comprising the following steps: Step S100, tunnel blasting and slag removal; According to the blasting design plan, after the tunnel is charged and detonated, suitable slag removal equipment such as loaders, excavators, dump trucks, etc. are selected according to the tunnel size, slag volume and transportation conditions.

[0053] Step S200, 3D laser scanning of the tunnel excavation area; After the tunnel excavation area is slag-removed and leveled, a ground-based 3D laser scanner is used to perform 3D laser scanning on the tunnel excavation area to obtain tunnel point cloud data. The tunnel point cloud is preprocessed to obtain the actual tunnel excavation contour point cloud. The actual tunnel excavation contour point cloud is converted from a dedicated format to a universal point cloud format, and then established and converted to the tunnel surrounding rock over-excavation and under-excavation analysis coordinate system.

[0054] Step S300, data processing to identify the location and volume of the undercut area; The processed tunnel point cloud data is input into the analysis system and compared with the designed excavation contour surface to calculate the volume of the undercut part of the tunnel and locate the location of the undercut area.

[0055] Step S300, performing static hydraulic blasting design on the undercut portion; Based on the above analysis of the shape, volume and location of the under-excavated area, a static hydraulic blasting design is carried out for the under-excavated area. The design content includes: the drilling position, drilling depth and drilling distribution of the static hydraulic splitting rod.

[0056] Step S400, drilling according to design layout; According to the above design, the drilling is carried out to locate the under-excavated parts of the tunnel, and the control points are introduced to set up the total station to lay out the drilling points. The positions and angles of the drilling points designed above are marked, and the drilling is carried out using an automatic drilling rig. After the drilling is completed, the hole is cleaned.

[0057] Step S500, installing a static hydraulic splitting rod to perform static blasting; After drilling and cleaning the hole, static hydraulic splitting rods are installed and static hydraulic splitting blasting is performed. Based on the static blasting design and the drilling depth, a static hydraulic splitting rod of appropriate length is selected. A small, self-propelled scissor-type lifting platform is used to lift and install the splitting rod into the planned borehole. The fixable static hydraulic splitting rod is then secured to the surrounding stable rock mass. After the construction personnel mechanically evacuate to a safe location, static hydraulic splitting blasting is performed. After the static blasting is completed, the static hydraulic splitting rod is removed and stored for future use.

[0058] Step S500, slag removal and contour cleaning; After static blasting to remove the under-excavated part, secondary slag removal is carried out, and after slag removal, the excavation contour surface is cleaned.

[0059] Step S500, completing subsequent support operations; After the secondary slag discharge and excavation contour surface cleaning are completed, subsequent support operations will be carried out.

[0060] In step S100, tunnel blasting should be rigorously designed. When selecting a blasting plan, blasting methods such as smooth blasting and pre-splitting blasting should be used as much as possible to help reduce over-excavation and under-excavation. Factors such as the tunnel's cross-sectional dimensions, geological conditions, and construction schedule requirements should be fully considered when arranging blastholes and calculating blasting parameters. Strict blasting monitoring and quality control should be implemented during the blasting process. A blasting monitoring plan should be developed, and a blasting construction quality control system should be established. Key aspects such as drilling accuracy, charge quality, and detonation network connections should be rigorously monitored and controlled to ensure that the blasting results meet design requirements. After blasting, when removing slag, the center section should be cleaned first, then expanded to both sides to avoid blockages that could affect the construction progress.

[0061] In step S200, site arrangement should be performed before performing three-dimensional laser scanning to facilitate scanning data collection, coordinate system unification, and coordinate system conversion.

[0062] In step S300, the designed excavation contour surface also needs to be processed and input into the analysis system to form the tunnel contour 1 point cloud data. The actual excavation point cloud data is compared with the point cloud data of the designed contour surface to analyze the location of the under-excavation in the tunnel, calculate the volume of the over-excavation and under-excavation, and generate a three-dimensional drawing of the under-excavation part.

[0063] like Figure 2 As shown, the drilling arrangement diagram of the static hydraulic blasting drilling design of the preferred embodiment of the present invention mainly includes a tunnel outline 1, a tunnel under-excavation area 2, a splitting point drilling 3, and an auxiliary hole 4.

[0064] In step S300, when designing the static hydraulic blasting for the undercut portion, the characteristics of static hydraulic splitting should be considered. Sufficient hydraulic splitting points should be arranged along the tunnel design contour to ensure that a tunnel contour surface that meets the clearance requirements can be formed after the static hydraulic splitting blasting. When designing the static blasting, the drilling direction and the splitting rod arrangement should be parallel to the tunnel axis as much as possible. When the undercut area 2 of the tunnel is large, drilling parallel to the tunnel excavation surface can be used as a supplement. When the undercut area 2 of the tunnel is too large to complete the static hydraulic splitting in one go, a Figure 2 The tunnel undercut area 2 was cleared by multiple static hydraulic splitting blasting in layers as shown; In the step S300, when designing static hydraulic blasting, the method of adding auxiliary holes 4 can be used to improve the static hydraulic blasting effect. The auxiliary holes 4 are through holes that are not placed with hydraulic splitting rods and are at a certain distance from the splitting point. The auxiliary holes 4 are preferably placed at a certain distance from the splitting point. Figure 2 The intermittent skip hole arrangement shown in the figure. Adding auxiliary holes 4 can improve static blasting efficiency by increasing the free surface. Adding auxiliary holes 4 can also improve the excavation profile. Specifically, adding auxiliary holes 4 along the tunnel design contour can make the static blasting profile smoother, facilitating subsequent construction. Adding a certain number of auxiliary holes 4 can also enhance the crushing effect, facilitating the rapid transportation of slag after blasting.

[0065] In step S400, when drilling and staking out, the accuracy of the staking out and positioning is ensured as much as possible to avoid drilling errors caused by inaccurate staking out, thereby affecting the quality of static blasting.

[0066] In step S400, if auxiliary holes 4 are arranged, the drilled auxiliary holes 4 are preferably through holes, that is, they are drilled through the rock in the undercut area 2 of the tunnel.

[0067] like Figure 3 As shown, the structural diagram of the static hydraulic splitting rod with a fixing device in the preferred embodiment of the present invention mainly includes a hydraulic splitting rod body 5, a hydraulic top block 6, an installation handle 7, a splitting rod hydraulic oil pipe 8, a connecting rope 9, and a detachable hydraulic expansion fixing device 10.

[0068] In step S500, if Figure 3 The static hydraulic splitting rod shown is a specially designed static hydraulic splitting rod with a fixing device. The detachable hydraulic expansion fixing device 10 is fixed to one end of the hydraulic splitting rod body 5 by a connecting rope 9. The detachable hydraulic expansion fixing device 10 is a detachable hydraulic expansion fixing device 10 that can be fixed to the surrounding surrounding rock by hydraulic control. The detachable hydraulic expansion fixing device 10 needs to select a fixed position on the surrounding stable surrounding rock. After drilling, the detachable hydraulic expansion fixing device 10 is placed in the hole and the hydraulic switch is activated to make it engage with the hole wall, thereby fixing the static hydraulic splitting rod to the surrounding surrounding rock. The function of the detachable hydraulic expansion fixing device 10 is to prevent the splitting rod from falling to the ground and being damaged after static blasting without support.

[0069] like Figure 4 As shown, the structural diagram of the detachable hydraulic expansion fixing device 10 of the preferred embodiment of the present invention mainly includes a connecting rope 9, a metal component 101 with a conical protrusion, a pin 102, a hydraulic power device 103, a fixing device hydraulic oil pipe 105, and a surrounding rock hole wall 11.

[0070] Figure 3 The detachable hydraulic expansion fixing device 10 is composed of Figure 4 The device shown is composed of two metal components 101 with conical protrusions at one end, a pin 102, a hydraulic power device 103, and a spring component 104. The device can achieve its fixing and removing functions through the top pressure and unloading force recovery of the hydraulic power device 103.

[0071] The working principle of the detachable hydraulic expansion and fixing device 10 is as follows: two metal components 101 with conical protrusions at one end are cross-stacked and pinned together in the middle by a pin 102, and the hydraulic power device 103 presses the other end of the metal component 101 with conical protrusions, and the two metal components 101 with conical protrusions are opened in a scissor-like manner, and the spring component 104 is stretched, and the protruding ends of the metal components 101 with conical protrusions squeeze the surrounding rock hole wall 11 to stabilize the device, so that the detachable hydraulic expansion and fixing device 10 can be stably stressed as a whole, and then the static hydraulic splitting rod is fixed by the connecting rope 9; when the static splitting blasting is completed, the static hydraulic splitting rod needs to be removed, and the force unloading and recovery process of the detachable hydraulic expansion and fixing device 10 is as follows: the hydraulic power device 103 unloads and recovers the force, and the spring component 104 contracts the tension to make the components with conical protrusions close in a scissor-like manner, thereby removing the detachable hydraulic expansion and fixing device 10 and the static hydraulic splitting rod.

[0072] like Figure 3 、 Figure 4As shown, when installing the static hydraulic splitting rod, the installation handle 7 can be held by hand to place the hydraulic splitting rod body 5 in the splitting point borehole 3, and the hydraulic splitting rod body 5 is adjusted and rotated so that the hydraulic top block 6 is perpendicular to the tunnel design contour. Then, the surrounding stable surrounding rock is selected for drilling to form the surrounding rock hole wall 11, and the detachable hydraulic expansion fixing device 10 is installed and fixed on the surrounding rock hole wall 11 to complete the installation and fixation of the static hydraulic splitting rod.

[0073] like Figure 5 As shown, the structural diagram of the small self-propelled scissor-type lifting platform of the preferred embodiment of the present invention includes a horizontally movable and fixable vehicle body 12, a scissor-type hydraulic lifting system 13, and a working platform 14.

[0074] In the step S500, when the tunnel undercut area 2 is located at the tunnel vault or a higher area, it is preferred to use Figure 5 The small self-propelled scissor lift shown here serves as a mobile lifting platform. This type of construction equipment features a horizontally movable fixed body 12 for horizontal movement and a scissor-type hydraulic lifting system 13 for vertical lifting. Construction workers, seated on the work platform 14 of the small self-propelled scissor lift, can move quickly and easily left and right, as well as up and down. This allows them to more quickly carry static hydraulic splitting rods to designated drilling locations for installation.

[0075] In step S500, when the slag and rock with a large volume after static blasting is difficult to be loaded and transported at one time, a static hydraulic splitting rod may be used for secondary segmentation and crushing.

[0076] The present invention proposes a construction method for removing the undercut portion of a tunnel using a static hydraulic blasting device, which has the following beneficial effects: (1) The static blasting technology is applied to the under-excavated part of the tunnel, which reduces the secondary disturbance of the surrounding rock caused by the secondary blasting of the large under-excavated part. It can well control the excavation fracture surface, making the tunnel excavation contour smooth, and will not cause over-excavation after the under-excavated secondary blasting. The construction efficiency is high, and there will be no large-scale blasting dust, which is beneficial to the rapid construction and the health of the construction workers.

[0077] (2) The use of three-dimensional laser scanning technology can quickly identify and locate the under-excavated area of ​​the tunnel, and accurately calculate the volume of the under-excavated area to provide a basis for subsequent static blasting design.

[0078] (3) The arrangement of hydraulic splitting points for static hydraulic splitting blasting was proposed, and the addition of auxiliary holes was proposed to help improve the hydraulic splitting effect.

[0079] (4) A special design is made for the static hydraulic splitting rod, and a detachable hydraulic expansion fixing device is added to the splitting rod. This device can effectively fix the static hydraulic splitting rod on the surrounding stable surrounding rock, preventing the static hydraulic splitting rod from falling directly to the ground without support after hydraulic static blasting and causing damage.

[0080] (5) It is preferred to use a small self-propelled scissor lift as a working platform to perform mobile lifting to help construction workers quickly locate and install static hydraulic splitting rods.

[0081] More specifically: 1. Security Using static hydraulic splitting rods to remove undercut areas in tunnels is a static blasting method. This method does not require the installation of explosives for blasting, causes little disturbance to the surrounding rock, is beneficial to the overall stability of the tunnel, and can reduce construction risks such as tunnel collapse. At the same time, using static hydraulic splitting rods to remove undercut areas in tunnels avoids the use of explosives for blasting, which can reduce the risks brought by explosives blasting during tunnel construction to a certain extent.

[0082] 2. Environmental protection This method uses hydraulic fracturing to remove undercut areas in tunnels without the vibration or impact of blasting. It effectively reduces noise, dust, and debris, making it more environmentally friendly for both construction workers and the surrounding environment. Reducing noise and dust improves the working environment and protects their health.

[0083] 3. Economical Compared to traditional explosive blasting, hydraulic splitting allows for precise control of the splitting direction, preventing overexcavation after secondary blasting of underexcavated areas, thus avoiding the additional cost of overexcavation treatment. Furthermore, the hydraulic splitter's high splitting force (maximum force of 600 tons) allows for a single operation in seconds, with continuous, uninterrupted operation and high efficiency. Operating and maintenance costs are very low, eliminating the need for isolation or other time-consuming and expensive safety measures required for blasting operations.

[0084] 4. Flexibility of use The static hydraulic splitting rod is small in size, light in weight and compact in structure, which ensures that its use is simple and easy to learn, and does not require professional personnel to carry out blasting operations like explosive blasting.

[0085] 5. Accuracy Unlike most traditional blasting demolition methods and equipment, hydraulic splitters can accurately determine the splitting direction in advance and can accurately demolish and split according to the required splitting shape and the size of the part to be removed.

[0086] Matters not covered by the present invention are known technologies.

[0087] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0088] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that variations and improvements are possible without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

[0089] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A construction method for removing undercut parts of a tunnel using static hydraulic blasting, characterized in that: The following steps are involved: S100, tunnel blasting, first slag removal operation; S200, 3D laser scanning of the tunnel excavation area to identify the location, shape and volume of the under-excavation area; S300, based on the analysis of the location, shape and volume of the undercut area, perform static hydraulic blasting design on the undercut area; S400, drilling according to design layout; S500: Install static hydraulic splitting rods to perform static hydraulic splitting blasting, carry out the second slag removal operation, and clean the contour surface.

2. The construction method for removing undercut parts of a tunnel by using static hydraulic blasting according to claim 1, characterized in that: Step S200 specifically includes: S201, arranging sites for 3D laser scanning to facilitate scanning data acquisition and coordinate system unification and conversion; S202: Compare the actual excavation point cloud data with the point cloud data of the designed contour surface, analyze the location of the tunnel undercut, calculate the shape and volume of the over-excavation and under-excavation, and generate a three-dimensional drawing of the undercut location.

3. The construction method for removing undercut parts of a tunnel by using static hydraulic blasting according to claim 2, characterized in that: Step S201 specifically includes: After the tunnel excavation area is slag-removed and leveled, a ground-based 3D laser scanner is used to perform 3D laser scanning on the tunnel excavation area to obtain tunnel point cloud data. The tunnel point cloud is preprocessed to obtain the actual tunnel excavation contour point cloud. The actual tunnel excavation contour point cloud is converted from a dedicated format to a universal point cloud format, and then established and converted to the tunnel surrounding rock over-excavation and under-excavation analysis coordinate system.

4. The construction method for removing undercut tunnel sections using static hydraulic blasting according to claim 1, characterized in that: Step S300 specifically includes: When designing static hydraulic blasting for undercut areas, the characteristics of static hydraulic fracturing should be considered. Sufficient hydraulic fracturing points should be arranged along the tunnel design contour to ensure that a tunnel contour surface that meets the clearance requirements can be formed after static hydraulic fracturing blasting. When designing static blasting, the drilling direction and splitting rod arrangement should be as parallel to the tunnel axis as possible.

5. The construction method for removing undercut parts of a tunnel by using static hydraulic blasting according to claim 4, characterized in that: When the tunnel undercut area is large, drilling parallel to the tunnel excavation face is used as a supplement; or When the undercut area of ​​the tunnel is too large and it is difficult to complete the static hydraulic fracturing in one go, a layered multiple static hydraulic fracturing blasting design is adopted to facilitate the clearing of the undercut area of ​​the tunnel.

6. The construction method for removing undercut tunnel sections using static hydraulic blasting according to claim 4, characterized in that: When designing static hydraulic blasting, the method of adding auxiliary holes is adopted to improve the static hydraulic blasting effect; The auxiliary hole is a through hole without a static hydraulic splitting rod and is at a certain distance from the splitting point. The auxiliary hole and the splitting point are arranged in an intermittent skipping manner.

7. The construction method for removing undercut tunnel sections using static hydraulic blasting according to claim 1, characterized in that: Step S500 specifically includes: After drilling and cleaning the hole, install a static hydraulic splitting rod for static hydraulic splitting blasting. According to the static blasting design and drilling depth, select a static hydraulic splitting rod of appropriate length, move and lift it with a small self-propelled scissor-type lifting platform, install the static hydraulic splitting rod into the predetermined borehole, and fix it on the surrounding stable rock. After the construction personnel and machinery have evacuated to a safe location, static hydraulic splitting blasting is carried out; After the static blasting is completed, the static hydraulic splitting rod is removed and stored for next use.

8. The construction method for removing undercut tunnel sections using static hydraulic blasting according to claim 7, characterized in that: A detachable hydraulic expansion fixture is used to fix the static hydraulic splitting rod to the surrounding stable rock mass; The detachable hydraulic expansion fixing device comprises a metal component, a pin, a hydraulic power device and a spring component. The first end of the metal component is provided with a conical protrusion, and the metal component is provided with two; After the two metal components are stacked crosswise, they are pinned together in the middle to form a scissor-like structure. The hydraulic power device presses the second end of the metal component and stretches the spring component to open the scissor-like structure. The raised end of the metal component squeezes the surrounding rock hole wall to stabilize the opening of the scissor-like structure and stabilize the force. The static hydraulic splitting rod is then fixed by a connecting cable. When the static splitting blasting is completed, the static hydraulic splitting rod needs to be removed.

9. The construction method for removing undercut tunnel sections using static hydraulic blasting according to claim 8, characterized in that: The process of unloading and recovering the force of the detachable hydraulic expansion fixture is as follows: The hydraulic power unit unloads and recovers the force, and the spring component contracts and pulls to close the scissor-type structure, thereby removing the static hydraulic splitting rod.

10. The construction method for removing the undercut portion of a tunnel using static hydraulic blasting according to any one of claims 1 to 7, characterized in that: Step S100 is specifically as follows: During tunnel blasting, blasting design should be conducted. When selecting a blasting plan, smooth blasting or pre-splitting blasting should be used as much as possible to reduce over-break and under-break. When blasthole arrangement and blasting parameter calculation are performed, the tunnel cross-sectional dimensions, geological conditions, and construction schedule requirements should be fully considered. During the blasting process, strict blasting monitoring and quality control are carried out. A blasting monitoring plan is formulated, and a blasting construction quality control system is established. Strict quality monitoring and control are carried out on key links such as drilling accuracy, charge quality, and detonation network connection to ensure that the blasting effect meets the design requirements; When slag removal is carried out after blasting is completed, the middle part should be cleaned first and then expanded to both sides to avoid blockage that affects the construction progress.

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