Shaft excavation method that combines boundary pipe jacking pre-support with internal weak blasting
By combining boundary pipe curtain pre-support with internal weak blasting, the problems of poor boundary control and shaft wall impact damage during vertical shaft excavation were solved, thereby improving the safety and forming quality of vertical shaft excavation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGHAN UNIVERSITY
- Filing Date
- 2026-05-06
- Publication Date
- 2026-07-10
AI Technical Summary
Existing shaft excavation technology suffers from problems such as poor boundary control, uneven rock fragmentation, severe impact damage to the shaft wall, and delayed support during construction. It is difficult to achieve integrated and coordinated control of the entire process of boundary pre-stabilization, internal controlled fragmentation, and immediate support of the shaft wall, which affects construction safety and forming quality.
The method of combining boundary pipe curtain pre-support with internal weak blasting is adopted. By constructing a central initial well and support system at the boundary of the vertical shaft, blasting is carried out in sections and timely reinforcement is carried out. Combined with permanent lining structure, the whole process is integrated and coordinated.
It improved the safety and forming quality of vertical shaft excavation, reduced the risk of shaft wall damage, improved construction efficiency and shaft wall stability, and achieved suitability of rock mass fracturing and controllability of construction.
Smart Images
Figure CN122359040A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of vertical shaft blasting excavation construction control technology, and particularly relates to a vertical shaft excavation method that coordinates boundary pipe curtain pre-support with internal weak blasting. Background Technology
[0002] As a key passage connecting the surface and underground space, shafts are important construction structures in the fields of geotechnical engineering and mining engineering. Their excavation operations are affected by factors such as limited construction space and complex surrounding geological conditions, resulting in high operational safety risks and stringent requirements for construction accuracy and coordination.
[0003] Traditional shaft excavation often employs a drill-and-blast cycle operation mode, progressing through a series of steps including drilling, charging and blasting, ventilation and smoke extraction, muck removal, and support. Construction efficiency and final quality depend on the precision of each step. To improve excavation results, controlled blasting technologies such as pre-splitting blasting and smooth blasting, as well as support technologies like casing drilling, pipe jacking, and pre-drilling grouting, have been gradually applied. Furthermore, various construction methods have been developed, including full-face mechanical drilling, freezing methods, and shaft tunneling machine methods. Each technology and method demonstrates its advantages in specific scenarios.
[0004] Current shaft blasting excavation technology still faces many unresolved problems. The integration of various technologies into a systematic and coordinated operational framework is difficult. Boundary control, internal rock fracturing, and shaft wall support are often designed and constructed as independent processes, lacking spatial layout and sequential design. The gap in surrounding rock exposure between drilling and blasting or support can easily lead to borehole wall instability, resulting in irregular excavation boundaries. Conventional drilling and blasting operations involve high charge concentration, making precise control of blasting energy difficult. This easily leads to uneven rock fragment sizes and severe impact damage to the shaft wall. There is currently no effective method to simultaneously achieve the dual goals of appropriate rock fracturing and low shaft wall damage. Furthermore, shaft wall support is often passively implemented in a delayed manner. After blasting creates a new free face, it is impossible to promptly seal and support the surrounding rock, resulting in a high risk of loosening and deformation of the surrounding rock, and making it difficult to effectively guarantee the long-term stability of the shaft wall.
[0005] In construction scenarios involving complex geological formations, sensitive environments, or large-diameter deep shafts, existing technologies cannot achieve integrated and coordinated control of the entire process, including pre-stabilization of boundaries, controlled internal fracturing, and immediate support of the shaft wall. Consequently, it is difficult to simultaneously ensure the safety, efficiency, and quality of shaft excavation.
[0006] Therefore, a shaft excavation method that combines boundary pipe jacking pre-support with internal weak blasting is urgently needed to solve this problem. Summary of the Invention
[0007] The purpose of this invention is to provide a shaft excavation method that combines boundary pipe curtain pre-support with internal weak blasting to solve the above-mentioned problems.
[0008] To achieve the above objectives, the present invention provides the following solution: A shaft excavation method that combines boundary pipe jacking pre-support with internal weak blasting includes the following steps: Delineate the boundaries of the shaft and determine the excavation area; Construct a central initial well at the center of the excavated area; A support system is constructed at the edge of the excavated area; The excavation area is divided into multiple blasting zones from the inside out, starting from the central initial well. The blasting areas are blasted one by one in order from the inside out. After the blasting is completed, the slag is cleared to form a vertical shaft. After immediately reinforcing the local unstable areas on the inner wall of the shaft, a permanent lining structure is constructed on the inner wall of the shaft.
[0009] Optionally, the method for constructing the central initial well includes the following steps: A guide hole is excavated in the center of the excavation area; The guide hole is enlarged to form the central initial well.
[0010] Optionally, a rotating magnetic field probe that moves up and down along the axis of the central initial well is deployed inside the central initial well.
[0011] Optionally, the depth of the pilot hole is matched with the design depth of the shaft, and during the drilling process of the pilot hole, an electromagnetic measurement-while-drilling system is used for real-time monitoring and correction to ensure that the deviation of the drilling trajectory of the pilot hole is within 3‰.
[0012] Optionally, the method for constructing the support system includes the following steps: Multiple grouting holes were excavated along the boundary of the shaft; Reinforcement of unstable strata in the soil; Construct an enclosure structure at the boundary of the shaft.
[0013] Optionally, the method for obtaining the unstable stratigraphic segment includes the following steps: While excavating the grouting hole, a soil and rock sample of the grouting hole is obtained, and the properties and state of the strata soil and rock are obtained based on the soil and rock sample. The stability of the stratum section is determined by analyzing the properties and state of the soil and rock. Unstable stratigraphic segments are identified as such.
[0014] Optionally, the method for dividing the blasting zone includes the following steps: Centered on the central initial well, annular blasting zones are sequentially set outside the central initial well, and are marked sequentially from the inside to the outside.
[0015] Optionally, the method for blasting the blasting area includes the following steps: The blasting area is divided into a near-center initial well blasting area and a far-center initial well blasting area; The near-center initial well blasting area was blasted in multiple successive blasting operations. Detonation holes are installed in each of the aforementioned blasting areas; After the blasting of the previously described blasting area is completed, the demolition of the next described blasting area will proceed. After all the blasting is completed, the debris is cleared.
[0016] Optionally, any of the aforementioned blasting zones must meet the following requirements: ; in, The total area of the existing free surfaces adjacent to the blasting area before detonation; The blasting cross-sectional area of the blasting zone; This is the blasting and swelling coefficient determined based on the characteristics of the soil and rock mass at the site.
[0017] Optionally, during the excavation of the blasting hole, an electromagnetic drilling measurement system is used in conjunction with a rotating magnetic field probe in the central initial well to ensure that the radial distance error of the blasting hole is no greater than 10 cm and the azimuth deviation is no greater than 0.5 degrees.
[0018] Compared with the prior art, the present invention has the following advantages and technical effects: This method integrates boundary pretreatment, refined internal blasting, and immediate support technologies to achieve unified and coordinated control of the entire vertical shaft blasting excavation process. This effectively solves the problems of fragmented procedures, coarse blasting control, and delayed support in traditional construction. Before excavation, trenching with casing drilling and pre-grouting reinforcement, combined with surface retaining structure construction, proactively improves the integrity and stability of the boundary rock and soil mass, accurately defines the excavation outline, and reduces the risks of shaft wall collapse and water inrush from the source, providing a stable operational foundation for subsequent high-precision blasting. The internal rock column layered and zoned weak blasting technology uses the initial free face as a reference, follows a blasting sequence from the inside out and the free face compensation space principle, achieving directional release of blasting energy. While ensuring the rock mass is fully broken into suitable transportable blocks, it significantly reduces the impact damage and vibration effects of blasting on the surrounding rock of the shaft wall, balancing rock breaking efficiency and shaft wall protection. The constructed full-cycle support system tightly couples pre-excavation support with immediate post-excavation support, promptly sealing newly exposed surrounding rock surfaces and providing targeted reinforcement to local weak areas. This effectively suppresses the loosening and deformation of the surrounding rock, achieving well wall stability control from the construction phase to the operation phase. At the same time, unmanned slag removal operations improve construction efficiency, making vertical shaft blasting and excavation operations more orderly and controllable, and overall improving the construction quality and safety level of the vertical shaft project. Attached Figure Description
[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a flowchart of the construction steps of the present invention; Figure 3 This is a plan view of the vertical shaft, blasting area, and blasting holes of the present invention; Figure 4 This is a schematic diagram of the tube curtain structure of the present invention. Detailed Implementation
[0020] The technical solutions of 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.
[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0022] Reference Figures 1 to 4 This invention discloses a vertical shaft excavation method that combines boundary pipe jacking pre-support with internal weak blasting, comprising the following steps: Delineate the boundaries of the shaft and determine the excavation area; Construct a central initial well in the center of the excavated area; Construct a support system at the edge of the excavated area; The excavation area is divided into multiple blasting zones from the inside out, starting from the central initial well. The blasting areas are blasted one by one from the inside out. After the blasting is completed, the debris is cleared to form a vertical shaft. After immediately reinforcing the unstable areas on the inner wall of the shaft, a permanent lining structure is constructed on the inner wall of the shaft.
[0023] This method first delineates the shaft boundary and defines the excavation area. A central initial shaft is constructed at the center of the area, and a support system is built at the edges. Then, the excavation area is divided into multiple blasting zones from the inside out. Each zone is blasted sequentially, and the debris is cleared to form the shaft. Finally, unstable areas of the shaft wall are reinforced in real time and a permanent lining is constructed. Through the coordinated operation of boundary support, internal zonal blasting, real-time reinforcement, and permanent lining, the method achieves boundary stability control, refined internal crushing, and long-term stability assurance of the shaft wall during shaft excavation. This solves the problems of fragmented excavation processes and delayed support in traditional methods, improving the safety and quality of shaft excavation.
[0024] As an optional implementation method, the construction method of the central initial well includes the following steps: A guide hole is excavated in the center of the excavation area; The pilot hole is enlarged to form the initial center well.
[0025] First, a pilot hole is excavated in the center of the excavation area, and then the pilot hole is enlarged to form the central initial well. The pilot hole provides a precise spatial reference for the construction of the central initial well. The enlargement operation is carried out based on this reference, which can ensure the verticality of the axis of the central initial well, making it a reliable initial free face for subsequent blasting operations. This creates good spatial conditions for subsequent zonal blasting from the inside out and ensures the directional release of blasting energy.
[0026] As an optional implementation, a rotating magnetic field probe that moves up and down along the axis of the central initial well is deployed inside the central initial well.
[0027] As a core component of the downhole reference station, this probe, together with the electromagnetic guidance equipment at the borehole opening, forms a joint high-precision guidance system. It can measure the relative position and distance of the subsequent blasting hole drill bit in real time, providing dynamic guidance for blasting hole drilling. From the equipment layout level, it ensures the spatial accuracy of subsequent drilling and blasting, avoiding well wall damage or poor blasting effect caused by drilling deviation.
[0028] As an optional implementation method, the pilot hole depth is matched with the design depth of the shaft, and during the drilling process of the pilot hole, an electromagnetic measurement-while-drilling system is used for real-time monitoring and correction to ensure that the deviation of the pilot hole's drilling trajectory is within 3‰.
[0029] As an optional implementation method, the method for constructing a support system includes the following steps: Multiple grouting holes were excavated along the boundary of the vertical shaft; Reinforcement of unstable strata in the soil; Construct an enclosure structure at the boundary of the shaft.
[0030] First, multiple grouting holes are excavated along the shaft boundary. Then, unstable strata in the soil layer are reinforced. Finally, a retaining structure is constructed at the shaft boundary. The grouting holes achieve targeted reinforcement of unstable strata. Combined with the outer retaining structure, the integrity and stability of the rock and soil mass at the shaft boundary are proactively improved, reducing the risk of shaft wall collapse and spalling during excavation from the source.
[0031] As an optional implementation method, the method for obtaining unstable stratigraphic sections includes the following steps: While excavating the grouting hole, obtain the rock and soil residue sample of the grouting hole, and obtain the properties and state of the strata rock and soil based on the rock and soil residue sample; The stability of the stratum section is determined by analyzing the properties and state of the soil and rock. Unstable stratigraphic segments are identified as unstable stratigraphic segments.
[0032] While excavating grouting holes, soil and rock samples are simultaneously obtained. Based on the samples, the properties and state of the strata are determined, and unstable strata are identified through analysis. This method enables simultaneous stratum exploration and grouting hole construction, eliminating the need for a separate stratum exploration process, thus improving construction efficiency. Furthermore, it can identify unstable strata in real time and accurately, providing accurate stratum data for subsequent targeted high-pressure grouting reinforcement and ensuring the effectiveness of boundary reinforcement.
[0033] As an optional implementation method, the method for dividing the blasting zone includes the following steps: Centered on the central initial well, ring-shaped blasting zones are sequentially set outside the central initial well, and marked in order from the inside to the outside.
[0034] Centered on the initial central shaft, annular blasting zones are sequentially established around it and marked from the inside out. The annular zones conform to the circular cross-sectional characteristics of the shaft, ensuring uniform blasting operations. The sequential markings from the inside out provide a clear construction basis for subsequent sequential blasting, ensuring that the blasting of later zones can utilize the free face of the previous zone, allowing blasting energy to dissipate primarily inwards and minimizing impact damage to the shaft boundaries.
[0035] As an optional implementation method, the method for blasting a blasting zone includes the following steps: The blasting area is divided into the near-center initial well blasting area and the far-center initial well blasting area; The blasting area near the initial well center was blasted in multiple successive blasting operations. Deploy blasting holes in each blasting area; After the previous blasting area is completed, the next blasting area will be cleared. After all the blasting is completed, the debris is cleared.
[0036] The blasting area is first divided into near-center and far-center initial well areas. The near-center area is blasted in multiple stages, with blasting holes laid out in each area. The next area is blasted only after the previous area has been cleared of debris. The staged blasting in the near-center area can gradually release the rock mass restraining force. The "blasting-slag clearing-re-blasting" process provides sufficient fragmentation and free space for subsequent blasting, avoiding damage to the well wall caused by the reflection of blasting energy due to debris accumulation.
[0037] Furthermore, the blasting holes are designed to match the depth of the shaft.
[0038] Setting up full-depth blasting holes helps ensure synchronous excavation of the shaft at its full depth.
[0039] As an optional implementation method, any blasting zone must meet the following requirements: ; in, This refers to the total area of the existing free-face surfaces adjacent to the blasting area before detonation; The blasting cross-sectional area of the blasting zone; This is the blasting and swelling coefficient determined based on the characteristics of the soil and rock mass at the site.
[0040] By quantifying the relationship between the free face area and the blasting cross-sectional area, sufficient space for expansion and energy release in the blasted rock mass is ensured. This principle effectively controls the direction of blasting energy release, ensuring thorough rock mass fracturing while preventing excessive impact of blasting energy on the shaft boundary and excavated areas, thus achieving dual optimization of rock mass fracturing efficiency and shaft wall protection effect.
[0041] As an optional implementation method, during the excavation of blasting holes, an electromagnetic measurement while drilling system is used in conjunction with a rotating magnetic field probe in the central initial well to ensure that the radial distance error of the blasting holes is no more than 10 cm and the azimuth deviation is no more than 0.5 degrees.
[0042] By utilizing an electromagnetic measurement-while-drilling system in conjunction with a rotating magnetic field probe in the central initial well, the radial distance error of the blasting holes is controlled to ≤10 cm, and the azimuth deviation to ≤0.5 degrees. The coordinated guidance of these two devices forms a closed-loop high-precision spatial control, ensuring that the blasting holes are precisely shaped according to the design position. This ensures that the energy distribution of the explosive charge is consistent with the design, avoids local energy concentration caused by drilling deviations, further reduces unnecessary damage to the surrounding rock of the wellbore, and guarantees the regularity of the shaft excavation cross-section.
[0043] Specifically, this method is divided into the following detailed steps: (1) Establishment of the central reference hole: At the center of the shaft design axis, a pneumatic down-the-hole drill rig equipped with an electromagnetic transmission measurement-while-drilling guidance system is used to drill a guide hole with a diameter of about 200 cm, which must reach the bottom of the shaft design. During the drilling process, the measurement-while-drilling system is used for real-time monitoring and correction to ensure that the deviation of the drilling trajectory is controlled within 3‰.
[0044] (2) Initial free surface formation: Using the aforementioned guide hole as a precise spatial reference, a drilling rig is used to enlarge the hole to form a central initial well with a diameter of about 1 meter and a depth extending to the bottom of the vertical shaft. This well constitutes the initial free surface and geometric reference for all subsequent blasting operations.
[0045] (3) Deployment of the guidance monitoring system: Install a rotating magnetic field probe that can move up and down along the shaft axis in the already formed central initial well to form the downhole reference station of the combined high-precision guidance system.
[0046] (4) Boundary strata pre-reinforcement and exploration: Around the outer area of the shaft design outline, a drilling measurement-while-drilling system was used for guidance, and a series of grouting holes with a diameter of about 20 cm were drilled using a large-hole down-the-hole drill with air reverse circulation. During this process, soil and rock samples were obtained simultaneously to determine the properties and state of the strata in real time; based on the strata identification results, high-pressure grouting was carried out to reinforce the identified unstable strata sections to form a deep pre-support ring.
[0047] (5) Construction of surface boundary retaining structure: In the soft overburden or unstable soil layer outside the shaft opening area, construct rigid reinforced retaining structures such as piles, interlocking piles or underground continuous walls to complete the surface pre-support of the excavation boundary.
[0048] (6) Layered and zoned blasting hole drilling: Using the axis of the central initial well as the absolute reference, and based on the pre-designed "from the inside out" annular zoned smooth blasting scheme, a pneumatic down-the-hole drill is used to drill blasting holes to full depth. During the drilling process, a combined guidance system consisting of an electromagnetic measurement-while-drilling system and a rotating magnetic field probe in the central well provides real-time dynamic guidance to ensure that the spatial position of each blasting hole meets the following requirements: with the central axis as the reference, the radial distance error is no more than 10 cm, and the azimuth deviation is no more than 0.5 degrees.
[0049] (7) Weak blasting and fragmentation control: Explosives are filled into the blasting hole. Specifically, the explosives are spaced out within the blasting hole. After filling a portion of the explosives, a portion of sealing material is added, and this process is repeated to achieve the spaced distribution of explosives within the blasting hole. The charge structure and quantity strictly follow the smooth blasting scheme specifically designed for the geological conditions of the area. Full-depth single blasting is implemented, and this process must meet the "free face compensation space criterion".
[0050] (8) High-efficiency unmanned slag removal: After the blasting of all areas is completed, heavy-duty hydraulic grab buckets are immediately used for unmanned slag removal operations underground. The grab buckets are operated by wireless remote control at the wellhead and use a single-rope rapid lifting scheme to grab the loose and accumulated rock and soil debris and transport it out of the well until the cleanup is completed.
[0051] (9) Immediate support and final lining of the shaft wall: After all sections have been excavated, the exposed surrounding rock of the shaft is systematically inspected, and local unstable areas are reinforced immediately using pipe grouting or similar techniques. Finally, the permanent lining structure of the shaft is constructed and the equipment is installed.
[0052] The core technology of implementing all steps (1) to (9) of this invention lies in establishing a spatial reference and initial free surface with millimeter-level precision, performing zonal sequential blasting controlled by strict physical principles, and coupling and penetrating the multi-layer support system before and after excavation, thereby achieving the unity of safety, efficiency and high forming quality in shaft engineering.
[0053] Steps (1) and (2) form the basis of the method of this invention. The "electromagnetic transmission measurement-while-drilling guidance system" is a key device for achieving high-precision drilling in ultra-deep holes. To further improve the accuracy of the guide hole, the drill string can be retrieved in segments at predetermined depths (the segment height is determined according to the well directional accuracy requirements) during the drilling process, and a static ultra-high precision inclinometer can be lowered to perform fine trajectory measurement and parameter correction. This method can improve the guidance accuracy to the order of one-thousandth and is suitable for vertical shaft projects with extremely high verticality requirements.
[0054] Steps (4) and (5) together constitute the specific implementation paradigm of the "vertical shaft boundary 'follow-the-casing drilling and trenching' technology" of this invention. The concept of "follow-the-casing drilling" here is reflected in the use of down-the-hole drilling air reverse circulation technology, and the casing can be run in during drilling to achieve synchronous drilling and wall protection. "Trenching" and pre-support are achieved through a reinforced curtain formed by a series of grouting holes and surface retaining structures. These two steps are completed before the main excavation, aiming to actively modify and reinforce the boundary soil and rock mass, and control the stability and shape of the well wall from the source.
[0055] Steps (6), (7), and (9) are the concentrated embodiment of the "internal rock column layering and zoned weak blasting technology". Among them, the "joint high-precision guidance system" in step (6) is the guarantee to ensure that the blasting hole network is accurately formed according to the design position. In this system, the rotating magnetic field probe can measure the relative position and distance with the blasting hole drill bit in real time, forming a closed-loop guidance control. The "free face compensation space criterion" that must be followed in step (7) is the core design principle of this blasting technology, and its mathematical expression is: For any zone to be blasted , must meet .
[0056] In the formula, This represents the total area of the existing free surfaces adjacent to the zone before detonation; This represents the blasting cross-sectional area of the zone; The blasting expansion coefficient (usually determined based on the characteristics of the soil and rock mass at the site) is used to determine the blasting expansion coefficient. >1). This principle ensures that the blasted rock mass has sufficient expansion space, and energy can be effectively released in the free-face direction, thereby obtaining a suitable fragment size for transportation and minimizing blasting damage and vibration to the remaining well wall. The "inner-out ring partitioning sequence" emphasized in step (9) is a mandatory timing control logic that ensures that each blast is carried out under the condition of the formed effective free face.
[0057] The “high-efficiency unmanned slag removal” scheme described in step (8) aims to achieve rapid slag removal by adopting heavy-duty grab buckets, wireless remote control and single rope lifting technology, creating conditions for tight blasting operation cycles, and is an important link to improve overall work efficiency.
[0058] The well wall inspection and immediate reinforcement in step (9) embody the timely application of the "vertical shaft well wall 'pipe-following curtain support' technology". After the overall excavation or the completion of key sections, by drilling grouting pipes and pressure grouting, a reinforced shell tightly bonded to the surrounding rock can be quickly formed, which is "immediate support". Together with the "pre-support" in steps (4) and (5), it constitutes a proactive well wall stability control system covering the entire construction cycle.
[0059] The following uses the blasting excavation of a Φ6.5m deep vertical shaft as an example to illustrate the specific implementation of the present invention.
[0060] The shaft is designed to be 60 meters deep with a diameter of 6.5 meters. The site's strata, from top to bottom, consist mainly of: 0-12m of backfill soil and strongly weathered rock layers, exhibiting poor stability; below 12m, moderately weathered granite, with a relatively intact rock mass but containing fracture zones. The construction will utilize the synergistic excavation method described in this invention, which combines boundary pretreatment, refined internal blasting, and immediate support.
[0061] The core procedures of this method are divided into four major stages: "establishment of central benchmark and monitoring system", "boundary pretreatment and surface support", "layered and zoned blasting and tunneling" and "instant support and finishing of well wall". Each stage is closely connected to form a closed-loop operation cycle.
[0062] (1) Project Overview and Overall Implementation Process The site for a certain vertical shaft project has a net diameter of 6.5 meters and a depth of 60 meters. The design requirements are to strictly control the verticality of the shaft, minimize disturbance to the surrounding rock, and ensure construction safety throughout the entire process of shaft blasting and excavation.
[0063] (2) Boundary pretreatment and surface support stage This phase aims to implement the "shaft boundary 'follow-the-pipe drilling and trenching' technology" to create a stable boundary for subsequent blasting excavation.
[0064] First, such as Figure 3 As shown in the plan layout, a ring-shaped working area is demarcated 3 meters outside the designed contour line of the vertical shaft. A large-hole down-the-hole drilling rig, coupled with measurement-while-drilling guidance, is used to drill a ring of Φ200mm grouting holes with a spacing of 1.5 meters and a depth of 60 meters using reverse air circulation. Rock cuttings are collected simultaneously during drilling to identify the formation in real time. When drilling reaches an unstable formation near a depth of 12m, a Φ180mm casing is run in for wall protection, achieving "casing-following drilling." Subsequently, high-pressure grouting is performed on the annular gap between the casing and the borehole wall, as well as on the identified fracture zones. The grouting pressure is controlled at 2-3MPa to form a pre-reinforced curtain to a depth of 60 meters.
[0065] Simultaneously, bored piles with diameters of 1000mm and 1200mm were constructed on the surface as a retaining structure, with a pile length of 15 meters, embedded in stable rock strata, completing the surface pre-support. The "drilled trench" type reinforcement ring formed at this stage, such as... Figure 4 As shown in the schematic diagram of the pipe curtain, the weak boundary is effectively sealed off.
[0066] (3) Establishment of central benchmark and monitoring system At the center of the shaft axis, a pneumatic down-the-hole hammer drill equipped with an electromagnetic wave measurement-while-drilling system was used to drill a Φ200mm pilot hole to the designed depth of 60 meters. After verification with a segmented inclinometer, the overall borehole deviation was ≤2.8‰, meeting the accuracy requirements.
[0067] Subsequently, the borehole was enlarged using this guide hole as a reference to form a central initial free shaft with a diameter of 1.2 meters and a depth of 60 meters. A liftable rotating magnetic field probe was installed inside this central shaft as a downhole space reference station, which, together with the borehole electromagnetic guidance system, constitutes a combined high-precision guidance system.
[0068] (4) Layered and zoned blasting implementation The core of this stage is "internal rock column layering and zoned weak blasting technology." Using the central free-cut shaft axis as the absolute reference, the entire shaft cross-section is divided into eight concentric circular zones (zones one to eight), as follows: Figure 3 The plan layout is shown. A combined guidance system was used to dynamically control the drilling and blasting of the holes. The measured radial error of the holes was ≤8cm, and the azimuth deviation was ≤0.4°.
[0069] The blasting strictly followed the "inside-out" sequence. The first zone (zone one) had a radius of 1.5 meters, using Φ70mm emulsion explosive cartridges, full-depth charging, and a linear charge density of 240g / m. Before blasting, the "free face compensation space criterion" had to be verified: before the detonation of the first zone, the free face consisted only of the central shaft wall, with a calculated area of 226㎡. The blasting cross-sectional area was 7.1㎡, and the measured rock mass fragmentation coefficient K was 1.35. Substituting these values into the formula, the criterion was verified to be met. This ensures the effective release of blasting energy.
[0070] (5) Unmanned slag removal and recycling operation After each blasting zone, a 20m³ heavy-duty hydraulic grab bucket is immediately used for muck removal. The grab bucket is operated wirelessly from the wellhead, employing a single-rope rapid lifting system to grab and transport the blasted rock fragments. Actual measurements show a single-cycle muck removal efficiency of up to 45m³ / h, approximately 60% higher than the traditional manual bucket-assisted muck removal method, ensuring a tight blasting operation cycle. Only after muck removal is completed can drilling and blasting operations proceed to the next zone, with the cycle continuing in one step.
[0071] (6) Immediate support and final lining of the well wall After the entire shaft cross-section was excavated to the designed depth, a systematic inspection of the exposed surrounding rock was immediately carried out. For local rock fractures or seepage points, the shaft wall was reinforced immediately using the "pipe-following pipe curtain support" technology: a Φ50mm grouting pipe was drilled using a pipe-following drilling rig, and after passing through the unstable area, ultrafine cement grout was injected under pressure. The measured average grout diffusion radius was 2.5m, quickly forming a reinforced shell.
[0072] Finally, the reinforcing bars were tied and C40 waterproof concrete was poured to complete the permanent lining construction. Through the above-mentioned full-cycle active control system combining "pre-support" and "instant support", the final convergence deformation of the well wall in this project was controlled within 0.12%H0 (H0 is the excavation height), and the forming quality was excellent.
[0073] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.
[0074] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims
1. A method for shaft excavation that combines boundary pipe jacking pre-support with internal weak blasting, characterized in that, Includes the following steps: Delineate the boundaries of the shaft and determine the excavation area; Construct a central initial well at the center of the excavated area; A support system is constructed at the edge of the excavated area; The excavation area is divided into multiple blasting zones from the inside out, starting from the central initial well. The blasting areas are blasted one by one in order from the inside out. After the blasting is completed, the slag is cleared to form a vertical shaft. After immediately reinforcing the local unstable areas on the inner wall of the shaft, a permanent lining structure is constructed on the inner wall of the shaft.
2. The shaft excavation method according to claim 1, which combines boundary pipe curtain pre-support with internal weak blasting, is characterized in that... The method for constructing the central initial well includes the following steps: A guide hole is excavated in the center of the excavation area; The guide hole is enlarged to form the central initial well.
3. The shaft excavation method according to claim 1, which combines boundary pipe curtain pre-support with internal weak blasting, is characterized in that... A rotating magnetic field probe that moves up and down along the axis of the central initial well is deployed inside the central initial well.
4. The shaft excavation method according to claim 2, which combines boundary pipe curtain pre-support with internal weak blasting, is characterized in that... The depth of the pilot hole matches the design depth of the shaft, and during the drilling process of the pilot hole, an electromagnetic measurement-while-drilling system is used for real-time monitoring and correction to ensure that the deviation of the drilling trajectory of the pilot hole is within 3‰.
5. The shaft excavation method according to claim 1, which combines boundary pipe curtain pre-support with internal weak blasting, is characterized in that... The method for constructing the support system includes the following steps: Multiple grouting holes were excavated along the boundary of the shaft; Reinforcement of unstable strata in the soil; Construct an enclosure structure at the boundary of the shaft.
6. The shaft excavation method according to claim 5, which combines boundary pipe curtain pre-support with internal weak blasting, is characterized in that... The method for obtaining the unstable stratigraphic interval includes the following steps: While excavating the grouting hole, a soil and rock sample of the grouting hole is obtained, and the properties and state of the strata soil and rock are obtained based on the soil and rock sample. The stability of the stratum section is determined by analyzing the properties and state of the soil and rock. Unstable stratigraphic segments are identified as such.
7. The shaft excavation method according to claim 1, which combines boundary pipe curtain pre-support with internal weak blasting, is characterized in that... The method for dividing the blasting zone includes the following steps: Centered on the central initial well, annular blasting zones are sequentially set outside the central initial well, and are marked sequentially from the inside to the outside.
8. The shaft excavation method according to claim 2, which combines boundary pipe curtain pre-support with internal weak blasting, is characterized in that... The method for blasting the blasting area includes the following steps: The blasting area is divided into a near-center initial well blasting area and a far-center initial well blasting area; The near-center initial well blasting area was blasted in multiple successive blasting operations. Detonation holes are installed in each of the aforementioned blasting areas; After the blasting of the previously described blasting area is completed, the demolition of the next described blasting area will proceed. After all the blasting is completed, the debris is cleared.
9. The shaft excavation method according to claim 8, which combines boundary pipe curtain pre-support with internal weak blasting, is characterized in that... Any of the aforementioned blasting zones must meet the following requirements: ; in, The total area of the existing free surfaces adjacent to the blasting area before detonation; The blasting cross-sectional area of the blasting zone; This is the bursting and swelling coefficient determined based on the characteristics of the rock and soil mass at the site.
10. The shaft excavation method according to claim 8, which combines boundary pipe curtain pre-support with internal weak blasting, is characterized in that... During the excavation of the blasting holes, the electromagnetic drilling measurement system is used in conjunction with the rotating magnetic field probe in the central initial well to ensure that the radial distance error of the blasting holes is no greater than 10 cm and the azimuth deviation is no greater than 0.5 degrees.