A method for constructing inclined shafts in a gentle-angle, short-distance surrounding rock fracture zone

Abstract

The present invention relates to the technical field of tunnel construction, and in particular to a method for constructing an inclined shaft in a gently inclined, short-distance surrounding rock fracture zone; the inclined shaft is used to connect an upper horizontal tunnel and a lower horizontal tunnel that have been penetrated, the slope of the inclined shaft is 10°-30°, and the construction geological conditions are surrounding rock grade IV or above; the construction method is divided into upper inclined shaft construction and lower inclined shaft construction, the upper slope of the inclined shaft meets the conditions for vehicle transportation, and top-down layered construction is adopted, and the excavation size is smaller than that of full-section excavation. Except for the top of the topmost layer, which requires support, the tops of the remaining layers do not require support when excavating, so the risk of collapse is small and the safety is high; during the construction of the pilot shaft, the shaft wall is supported to ensure the safety of the operation, and when expanding the excavation, the lower horizontal tunnel is first backfilled with blocks of stone, and then the excavation is expanded from top to bottom, so the construction efficiency is high and the safety risk is low; after the pilot shaft is penetrated from top to bottom, the construction water and fissure water are discharged into the lower horizontal tunnel through the pilot shaft, so that operation under waterless conditions can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel construction, and in particular to a method for constructing an inclined shaft in a surrounding rock fracture zone with a gentle inclination angle and a short distance. Background Art

[0002] According to the "Construction Code for Underground Excavation of Hydraulic Structures" SL 378-2007, underground caverns can be divided into three types according to the inclination angle (the angle between the cave axis and the horizontal plane): horizontal tunnels, inclined shafts, and vertical shafts. The classification types are as follows: horizontal tunnels have an inclination angle of less than 6°, inclined shafts have an inclination angle of 6° to 75°, and vertical shafts have an inclination angle greater than 75°.

[0003] For inclined shafts with an inclination angle less than 30°, full-section excavation from top to bottom can be adopted. In previous water conservancy and hydropower projects, there are mainly two conventional inclined shaft construction methods. One is the pilot tunnel method, that is, first excavate a pilot shaft in the middle of the well, and then expand the excavation layer by layer from top to bottom or from bottom to top, and carry out slag discharge through the pilot shaft. However, when the slope of the lower part of the inclined shaft is relatively small, the slag discharge by the pilot shaft method is likely to cause well blockage; the other is the full-section method, that is, through the winch and track laying, the full-section construction is carried out layer by layer from top to bottom, and the slag is discharged through the track, which has high cost and low work efficiency.

[0004] For the construction of inclined shafts with surrounding rock grades of Class IV and above, which do not meet the maximum climbing slope of vehicles and where the pilot shaft is easily blocked, there are difficulties such as short construction period, high difficulty, high safety risks and high quality requirements. It is urgent to develop a high-quality, efficient, fast, economical and safe construction process for inclined shafts in gentle-angle, short-distance surrounding rock fracture zones. Summary of the Invention

[0005] In response to the deficiencies in the above-mentioned prior art, the present invention provides a method for constructing inclined shafts in a gentle-angle, short-distance surrounding rock fracture zone with high construction efficiency, low safety risk and cost savings.

[0006] The present invention provides a method for constructing an inclined shaft in a fractured zone with a gentle inclination angle and a short distance. The inclined shaft is used to connect an upper horizontal tunnel and a lower horizontal tunnel that have been connected. The slope of the inclined shaft is 10° to 30°, and the construction geological conditions are Class IV and above of the surrounding rock grade.

[0007] The construction method of the inclined shaft comprises the following steps:

[0008] Divide the construction area:

[0009] The inclined shaft structure starting from the upper horizontal tunnel and having a slope of less than or equal to 15° is divided into the upper part of the inclined shaft, and the inclined shaft structure located below the upper part of the inclined shaft and connected to the lower horizontal tunnel with a slope greater than 15° is divided into the lower part of the inclined shaft;

[0010] Construction of the upper part of the inclined shaft:

[0011] The upper part of the inclined shaft is subjected to blasting construction in layers from top to bottom. The slag and rock produced by the blasting are transported out through the upper horizontal tunnel by vehicles. Support is carried out in time after the blasting excavation.

[0012] Inclined shaft lower construction:

[0013] After the upper part of the inclined shaft is constructed, a pilot shaft is excavated by blasting in layers on the bottom surface. The slag generated by the excavation of the pilot shaft is lifted to the wellhead of the pilot shaft and transported out in sequence through the upper part of the inclined shaft and the upper horizontal tunnel by vehicles. After the pilot shaft is excavated through the lower horizontal tunnel, the position of the lower horizontal tunnel located at the lower part of the inclined shaft is backfilled with rocks. The pilot shaft is then expanded in layers from top to bottom to the designed boundary line. The slag enters the lower horizontal tunnel through the pilot shaft and is discharged from the lower horizontal tunnel.

[0014] After the excavation is expanded to penetrate the top of the lower flat tunnel, the blocks of stone backfilled in the lower flat tunnel are transported out through the lower flat tunnel, and the construction of the inclined shaft is completed.

[0015] In this technical solution, the upper part of the inclined shaft is constructed in layers from top to bottom, and the slag is transported out through the upper horizontal tunnel by vehicles. The excavation size is smaller than that of the full-section excavation, the risk of collapse is small, and the safety is high. During the construction of the pilot shaft, the slag is lifted to the pilot shaft mouth and transported out through the upper part of the inclined shaft and the upper horizontal tunnel. When expanding the excavation, the lower horizontal tunnel is first backfilled with blocks of stone, and then the excavation is expanded from top to bottom. The slag enters the lower horizontal tunnel through the pilot shaft and is transported out. The construction efficiency is high, the safety risk is low, and the construction cost is greatly reduced. When the pilot shaft is penetrated from top to bottom, the construction water and fissure water are discharged into the lower horizontal tunnel through the pilot shaft, so that operations under waterless conditions can be achieved.

[0016] In some embodiments of the present application, the upper portion of the inclined shaft is subjected to layered blasting construction, and the specific construction steps of each layer include:

[0017] Measurement and hole layout: measurement and layout are carried out at the excavation site of the upper horizontal tunnel, and blasthole positions are laid out on the tunnel face according to the requirements of the drilling and blasting plan design;

[0018] Drilling, charging, and blasting: Drill the blastholes on the tunnel face. After drilling is completed, charge the blastholes with explosives, evacuate personnel, and detonate for blasting.

[0019] Slag removal: Use an excavator to loosen the rocks, and use vehicles to transport the slag out through the upper level tunnel;

[0020] Support: After the excavation is completed, the initial spraying is carried out in time. After the initial spraying is completed, support is carried out on the top and both sides;

[0021] When the excavation slope exceeds the maximum climbing slope of the vehicle, the construction of the lowest layer of the upper part of the inclined shaft is completed, and the excavation of the upper part of the inclined shaft is completed.

[0022] In some embodiments of the present application, when constructing the upper part of the inclined well, it is necessary to ensure that the blast holes are parallel to each other during the drilling process. When drilling, the order of first bottom and then top is adopted. After each hole is made, the hole mouth is sealed with a flexible material to prevent the hole from being covered by blocks falling from above.

[0023] In some embodiments of the present application, after the excavation of the uppermost layer of the inclined shaft is completed, the top arch and the arch frames on both sides are installed, anchor rods are installed, mesh is hung, and then a second shotcrete construction is carried out until the designed thickness is reached;

[0024] After the construction of the top layer is completed, there is no need to support the top of the excavation of the remaining layers. The steel arch frames on both sides are extended and connected with connecting plates. Locking anchor rods are installed at the connection parts of the arch frames on each side and welded to the arch frames. The arch frames are connected with steel bars with a circumferential spacing of 0.5m.

[0025] In some embodiments of the present application, when blasting the upper part of the inclined shaft, the blasting holes are charged with columnar continuous charges, and the peripheral holes are charged with air interval charges. The charges should be dense and well blocked.

[0026] After the blasting is completed, ventilation and smoke dispersion are carried out through the press-in ventilation ducts at the hole until the concentration of harmful gases is reduced to the specified standard, and then the slag removal process can be carried out on site.

[0027] In some embodiments of the present application, before the construction of the upper portion of the inclined shaft, the lower adit needs to be initially supported;

[0028] After the construction of the upper part of the inclined shaft is completed and before the construction of the pilot shaft, the initial support of the lower horizontal tunnel is strengthened to form a strengthened support structure;

[0029] After the excavation and support of the pilot shaft is completed, the arch I-beam of the reinforced support structure of the lower horizontal tunnel in the pilot shaft area is removed, and then the block stones are backfilled to prevent collapse during the excavation of the inclined shaft. After the excavation is completed, the blocks of stone are transported out through the pilot shaft and the lower horizontal tunnel.

[0030] In some embodiments of the present application, during the construction of the pilot shaft, excavation blasting is carried out on a narrow free-facing surface, and a small-aperture shallow-eye segmented micro-difference blasting method is adopted. Two adjacent explosive packs or front and rear rows of explosive packs are detonated in sequence at a time interval of milliseconds to reduce the blasting vibration effect.

[0031] In some embodiments of the present application, when the pilot well is excavated, the accumulated water in the pilot well is promptly removed by using a slag bucket to lift out the mud and water together, or by excavating a sump on one side of the hole bottom and draining it with a water pump;

[0032] In order to prevent collapse and ensure construction safety, C25 shotcrete is used for initial support in each excavation layer. When the surrounding rock stability is poor, spaced ring beam concrete support is used with a spacing of no more than 3m.

[0033] In some embodiments of the present application, the lower part of the inclined shaft is excavated by smooth blasting, and is precisely laid out using infrared laser positioning technology. The peripheral holes are all drilled on the designed contour line, and the drill holes are slightly inclined outward by 2 to 3°. The drill holes are kept parallel to each other, and the bottoms of the holes are at the same elevation.

[0034] In some embodiments of the present application, when the lower part of the inclined shaft is excavated in layers, the support construction includes the following steps: spraying a layer of concrete 3 to 5 cm thick immediately after excavating one layer, erecting / extending the steel arch frame, setting the system anchor rods, laying the steel mesh, and spraying the second layer of concrete;

[0035] When expanding the excavation to the next layer, repeat the above support construction steps. Timely support ensures the formation of the excavation contour surface and reduces the impact of blasting vibration on the surrounding rock and adjacent structures, which is beneficial to quality control and structural safety.

[0036] Based on the above technical solution, the upper part of the inclined shaft is constructed in layers from top to bottom, and the slag is transported out through the upper adit by vehicles. The excavation size is smaller than that of full-section excavation, the risk of collapse is reduced, and the safety is high. During the construction of the pilot shaft, the slag is lifted to the pilot shaft mouth and transported out through the upper part of the inclined shaft and the upper adit. When expanding the excavation, the lower adit is first backfilled with blocks of stone, and then the excavation is expanded from top to bottom. The slag is transported out through the pilot shaft into the lower adit. This has high construction efficiency, low safety risks, and greatly reduced construction costs. When the pilot shaft is penetrated from top to bottom, the construction water and fracture water are discharged into the lower adit through the pilot shaft, making it possible to operate under waterless conditions.

[0037] During the excavation of the lower part of the inclined shaft, the support for the lower horizontal tunnel was strengthened, and the rock mass was less disturbed, creating good surrounding rock stability conditions for the inclined shaft excavation. Timely support after the expansion of one layer ensured the formation of the excavation contour surface and reduced the impact of blasting vibration on the surrounding rock and adjacent structures, which was beneficial to quality control and structural safety.

[0038] The blasting operation can be multi-cycle and continuous, and 2 to 3 cycles can be completed every day, with a footage of 3 to 5 meters. If the 70-meter-long inclined shaft adopts the pilot well method or the full-section excavation method, the total construction period is about 90 days. This application saves the time of setting up the raise drilling rig or installing and dismantling the track and transporting slag, and the construction period is shortened by nearly 15 days. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0040] Figure 1 Schematic diagram of the positional relationship between the upper and lower parts of an inclined well according to an embodiment of the present invention;

[0041] Figure 2This is a schematic diagram of the upper construction layer of an inclined shaft according to an embodiment of the present invention;

[0042] Figure 3 This is a schematic diagram of the position of the pilot shaft during construction of the lower portion of the inclined shaft according to an embodiment of the present invention;

[0043] Figure 4 This is a schematic diagram of the position of backfilling the lower adit with rocks after the pilot well is penetrated according to an embodiment of the present invention.

[0044] In the picture:

[0045] 10. Lower flat tunnel; 11. Block stone; 20. Upper flat tunnel; 30. Inclined shaft; 31. Upper part of inclined shaft; 311. First floor; 312. Second floor; 313. Third floor; 32. Lower part of inclined shaft; 33. Pilot shaft. DETAILED DESCRIPTION

[0046] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0047] In the description of the present invention, it should be understood that the terms "center", "transverse", "longitudinal", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0048] The terms "first," "second," and "third" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or to implicitly specify the quantity of the technical features indicated. Therefore, a feature specified as "first," "second," or "third" may explicitly or implicitly include one or more of such features.

[0049] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediary, or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0050] A deep hole flood discharge project in a certain reservoir project was constructed under geological conditions of surrounding rock grade IV or above. Inclined shaft 30 was used to connect the upper horizontal tunnel 20, which served as the flood discharge tunnel, and the lower horizontal tunnel 10, which served as the diversion tunnel. Behind the gate shaft of the flood discharge tunnel was the Longtoutou section, which consisted of a vertical curve, a sloped straight section, and an anti-arc section. The total length of the Longtoutou section was 71.34 m. The equation of the vertical curve (Walker curve) was y = 0.00633x 2 The slope ratio for the straight section is 1:2, the radius of the anti-arc section is 25m, the anti-arc center angle α is 25.88°, the starting elevation is 293.94m, and the terminal elevation is 269.52m. The transition section from 0+176.00m to 0+186.00m is the transition section, with the floor width gradually increasing from 4m to 6m. The floor width remains 6m for the remaining sections. The tunnel is a circular arch with straight walls, and the center angle of the tunnel crown is 120°. The transition section is within 10m of the gate shaft. After lining, the tunnel cross-section dimensions are 4m×7m (width×height) at the starting end and 6m×7m (width×height) at the end. The cross-section dimensions of the remaining sections after lining are the same as those at the end of the transition section.

[0051] If the pilot tunnel method is adopted, a pilot well is first excavated in the middle of the well, and then the excavation is expanded layer by layer from top to bottom or from bottom to top, and the slag is discharged through the pilot well. However, since the slope of the anti-arc section at the lower part of the inclined well 30 is 25.88°, the slag discharge by the pilot well method is likely to cause well blockage; and if the full-section method is adopted, the full-section construction is carried out layer by layer from top to bottom through the winch and track laying, and the slag is discharged through the track, which has high cost and low work efficiency.

[0052] Before construction of the gently inclined, short-distance, fractured-rock zone inclined shaft 30 of this embodiment, planning, material preparation, and production testing should be conducted based on on-site traffic flow within the power station construction area, the overall layout of the power generation system, the overall construction schedule, and the hydrological and geological conditions of the project. This includes planning for the inclined shaft 30, material preparation, and production testing. These planning steps include: layout of construction roads, placement of monitoring sections and equipment, planning for wind, water, and electricity, procedures for cross-excavation of caverns, deployment of construction machinery and equipment, personnel deployment, schedule planning, quality and safety assurance measures, and production testing of shotcrete and blasting parameters.

[0053] The vertical curve and part of the slope straight section of the inclined shaft 30 have a relatively gentle slope of less than 15°, which meets the conditions for mechanical transportation. It is divided into the upper part 31 of the inclined shaft, such as Figure 1-Figure 2 As shown, the blasting method is used to construct the site in steps from top to bottom, with a total of three layers. The top layer is the first layer 311, the middle layer is the second layer 312, and the bottom layer is the third layer 313. The excavation height of each step is 5m, and the cycle footage is 1.5m. The blasting construction parameters are determined according to the test parameters.

[0054] The specific process of layer construction is:

[0055] Survey and layout: Conduct survey and layout at the excavation site of upper horizontal tunnel 20, including the tunnel centerline, top arch centerline, floor elevation, face stake number (a stake number line is drilled every 5 meters inside the tunnel), design contour line, and waistlines on both sides or lines parallel to waistlines. Blasthole positions are then laid out on the face according to the drilling and blasting design requirements.

[0056] Drilling: The YTP-28 air-leg drill is divided into different parts and the drilling is carried out by designated personnel. During the drilling process, it is necessary to ensure that the blast holes are parallel to each other. When drilling, the order of first down and then up is adopted. After each hole is made, the hole mouth is blocked with a flexible material to prevent the hole from being covered by the falling pieces of the hole above.

[0057] Charging and blasting: Before charging explosives, use high-pressure air to blow away any debris and water in the blastholes. Qualified blasters will charge explosives and place detonators. A digital detonator micro-difference (25-50ms) blasting network and smooth blasting will be used. Columnar continuous charging will be used in blastholes, while air-interval charging will be used in peripheral holes. The charging must be dense and well-blocked. After charging and review by professionals, personnel and equipment will be evacuated and alerts will be set. The blaster will be responsible for detonating the blast. Immediately after blasting, the cave will be ventilated using the push-in ventilation duct at the cave entrance for 30 minutes to disperse smoke. When the concentration of harmful gases drops to the specified standard, safety personnel will then enter the cave to check the working surface and immediately address any unsafe factors.

[0058] Slag removal: Use the excavator bucket teeth to pry, dig, and knock out loose stones. Only after the safety personnel have passed the inspection can they enter the working face to carry out the slag removal operation. Use vehicles to transport the slag out through the upper level tunnel 20;

[0059] After the excavation is completed, the initial spraying is carried out in time. After the initial spraying is completed, the top arch and the arch frames on both sides are installed, anchor rods are installed, mesh is hung, and then the second shotcrete construction is carried out until the designed thickness is reached;

[0060] Repeat the construction process for the first layer, 311, to construct the second and third layers, 312 and 313. During construction, the steel arches on both sides were extended using connecting plates. Each arch connection was anchored with 4.5m-long, φ22mm locking anchors, welded to the arches, and connected with φ22mm steel bars with 0.5m circumferential spacing. When excavating the third layer, 313, the excavator should be used to excavate downward as far as possible, ensuring the maximum climbing slope for vehicles. When excavation is no longer possible, the remaining surrounding rock will be transferred to the lower construction area. The slag will be removed from the upper level tunnel 20 using the excavator and loader.

[0061] Since the excavation size during the construction of the upper part 31 of the inclined shaft is smaller than that of the full-section excavation, there is no need to support the top during the excavation of the second layer 312 and the third layer 313, the risk of collapse is small and the safety is high.

[0062] During the construction of the upper part 31 of the inclined shaft, initial support is required for the lower horizontal tunnel 10. During the construction of the lower part 32 of the inclined shaft, the support strength of the lower horizontal tunnel 10 should be strengthened by reducing the spacing between steel arch frames, adjusting the type of I-beams, etc. to form a reinforced support structure. The reinforced support strength of this embodiment adopts a structural type of I-22 steel arch frames with a spacing of 0.5m + φ25 system anchor rods with a spacing of 1.5m and a length of 6m + φ8@20×20 steel mesh + 20cmC20 sprayed concrete. According to empirical calculations, it can meet the safety requirements of the inclined shaft 30 construction.

[0063] The remaining straight slope section and the reverse arc section below are constructed as the lower part 32 of the inclined shaft;

[0064] First, excavate the pilot shaft 33 by the manual well method, such as Figure 3 As shown, the pilot shaft 33 has a diameter of 2.0 m and a depth of about 7.5 m. It is excavated by layered blasting. A lifting device is installed at the wellhead of the pilot shaft 33. The slag is manually lifted to the wellhead of the pilot shaft 33 by the lifting device in conjunction with a winch for discharge. Then, a vehicle is used to transport the slag out through the upper part 31 of the inclined shaft and the upper horizontal tunnel 20.

[0065] The construction process of pilot shaft 33 mainly includes: construction measurement, hole layout and drilling, charging, detonation, tunnel ventilation, smoke exhaust and dust removal, safety inspection, slag removal, and wall protection construction.

[0066] Specifically, when drilling, a YT28 hand drill is used for drilling and manual charging. Since the excavation blasting has only a narrow free air surface with a diameter of 2 meters, the excavation blasting should adopt a small-aperture shallow-eye segmented micro-difference blasting method, that is, two adjacent explosive bags or front and rear rows of explosive bags are detonated in sequence with a time interval of milliseconds to reduce the blasting vibration effect; then the rock wall of the pilot shaft 33 is protected by wall construction. After the pilot shaft 33 passes through the lower horizontal tunnel 10, the position of the lower horizontal tunnel 10 located below the inclined shaft 30 is backfilled with blocks 11 to prevent the lower horizontal tunnel 10 from collapsing in the subsequent process.

[0067] When discharging slag, the winch is used to lift the slag bucket to discharge the slag, and the loader is used to transport the slag to a temporary site. The slag bucket should be sealed and the volume should not exceed 1m 3 The maximum loading volume of slag shall not exceed 2 / 3 of the total volume of the barrel. The abandoned soil location shall be 5.0m away from the edge of the wellhead, and the height of the abandoned soil pile shall not exceed 1.5m.

[0068] During excavation, water should be promptly removed from the hole. This can be done by using a slag bucket to hoist the mud and water out together, or by excavating a sump on one side of the hole bottom and pumping it out. To prevent hole collapse and ensure construction safety, each excavation layer is primed with C25 shotcrete, 10 cm thick. If surrounding rock stability is poor, spaced ring beams are used for support, with spacing no greater than 3 m.

[0069] After the excavation and support of the pilot shaft 33 were completed, the arched I-beams of the reinforced support structure in the pilot shaft 33 area of ​​the lower adit 10 were removed. Since the steel arches of the reinforced support structure were spaced 0.5 meters apart, the arched I-beams below the pilot shaft 33, with a diameter of 2 meters, would obstruct the slag and rock transported through the pilot shaft 33 during excavation. Therefore, the inner arched I-beams within the diameter of the pilot shaft 33 needed to be removed. The lower adit 10 was then backfilled with rock blocks 11 to prevent the inclined shaft 30 from collapsing during excavation.

[0070] like Figure 4 As shown, after the backfill of rock 11 was completed, smooth blasting was used to expand the excavation layer by layer from top to bottom to the design boundary. The drill holes were vertical, the angles were easily controlled, and the excavation contour was regular. Infrared laser positioning technology was used for precise layout, accurately marking the location and direction of the surrounding smooth blasting holes. All peripheral holes were drilled on the design contour line, with a slight outward inclination of 2-3 degrees. The holes were parallel to each other and the bottoms of the holes were at the same elevation.

[0071] After each layer of excavation is expanded, support construction is carried out in time. The support construction follows the construction sequence of spraying a layer of 3cm to 5cm thick concrete immediately after excavation, erecting / extending the steel arch frame, setting up the system anchor rods, laying the steel mesh, and spraying the second layer of 312 concrete. The above construction steps are repeated after the next layer of excavation. The stones in the excavation process are transported to the lower flat tunnel 10 through the pilot shaft 33, and the slag is discharged from the lower flat tunnel 10.

[0072] After the expansion is completed, the rocks 11 backfilled in the lower adit 10 are transported out through the lower adit 10 , and the construction of the inclined shaft 30 is completed.

[0073] During support construction, steel supports are fabricated using a steel bending machine, bending the steel frame in sections according to the curvature of the tunnel section and trial-assembling them. Before installation, the rock face is cleaned of loose rocks and wall base deposits, undercuts are addressed, and the steel arch installation area is partially excavated to ensure that the tunnel cross-sectional dimensions meet design requirements after installation. Steel frame installation is performed immediately after the initial grouting of the face excavation is completed. Based on the measured locations, the steel frame sections are bolted together at the face, with two locking anchor rods installed on each side. The steel support installation tolerances are ±50mm in both lateral and vertical directions, and ±2° in verticality.

[0074] Steel frames should be formed by cold bending. There should be no false welds during the steel frame processing, and the weld surface should be free of defects such as cracks and weld bumps. After each steel frame is processed, it should be placed on a cement floor for trial assembly. The allowable error for peripheral assembly is ±3cm, and the plane warping should be less than 2cm.

[0075] The arch steel frame must be locked with its two bases to prevent it from sinking or retracting. Whenever possible, the steel frame should be welded to the outcroppings of anchor rods and steel mesh to enhance the combined support effect. When spraying concrete, the gap between the steel frame and the rock surface must be saturated with concrete to achieve a dense finish.

[0076] During anchor bolting, use a measuring instrument to stake out the anchor hole positions. Ensure that the anchor hole position deviations meet design specifications, with the hole axis oriented against the potential sliding surface and an angle greater than 45°. Drilling within the hole is performed manually using a work platform vehicle and a hand-held pneumatic drill. After drilling, flush the hole with high-pressure air to remove debris and scum from the hole walls and to dry any accumulated water. Anchor bolt installation should follow a "grouting first, then bolt insertion" procedure. Grouting and bolt insertion are performed manually. The grouting tube is first inserted into the hole bottom, mortar is injected, and then slowly pulled out. Once the hole is fully filled, the anchor bar is inserted to the designed depth and secured at the hole mouth. The anchor bolt should be inserted centered and slowly. After insertion, the exposed end of the anchor bolt (bundle) should be hammered three to four times with a heavy hammer. Pad the hole mouth with small stones or other materials to ensure that the anchor bolt (bundle) is fully grouted and centered. Avoid collision or pulling until the grouting strength reaches 70% of the design strength.

[0077] Before laying the steel mesh, it must be derusted and cleaned. During installation, the mesh should be laid along the excavation surface, keeping a distance of 30-50 mm from the wall (precast concrete blocks can be used for overhead support). The mesh should be securely connected to the anchor rods and steel arches, and the mesh should not shake during shotcrete. When installing the finished mesh, weld the joints, with an overlap length of at least 200 mm.

[0078] Before spraying, the sprayed surface must be cleaned, including loose rocks, slag, or accumulated debris from the excavation surface. Excavate any under-excavated areas and flush the sprayed surface with a high-pressure air and water gun. For damp, muddy rock, high-pressure air can be used to clean the rock surface. After the sprayed surface has been inspected and approved, markings indicating thickness should be placed on the anchor bars. If anchor bars are not available, markings indicating thickness can be added using custom anchor bars.

[0079] Strictly control the weighing deviation of various raw materials for concrete mixing to within specified values: ±1% for water and accelerator, ±2% for sand and gravel. Strictly control the quality of concrete mixing, with a mixing time of no less than 2 minutes. Keep the nozzle perpendicular to the spraying surface as much as possible to minimize rebound and ensure the quality of the sprayed concrete.

[0080] The spraying order of shotcrete is generally from bottom to top, from wall to arch. During spraying, the working wind pressure of the sprayer is generally controlled at 0.2~0.4MPa; the sprayer strictly controls the water-cement ratio at 0.4~0.45 to make the surface of the spray layer smooth and flat, without dry spots or slippage and flow. The nozzle should be perpendicular to the sprayed surface, with a distance of 0.6~1.0m, and move in an "S" shape; first level the concave part of the sprayed surface, and then move the nozzle slowly and evenly in a spiral shape, pressing the front half a circle each time, with a circle diameter of about 30cm, and strive to make the sprayed concrete surface smooth and flat.

[0081] Concrete spraying is carried out in two stages. The first stage is carried out immediately following the excavation work surface, with a spraying thickness of 3 to 5 cm. After the steel mesh is laid, the second stage of spraying is carried out until the designed thickness is reached. After the final setting of the shotcrete, watering and other measures can be used for curing. The shotcrete surface should be kept moist for 7 days.

[0082] When the rock surface is concave and convex, spray the concave part once to make the rock surface smooth, and then spray the large area. The last spraying should be carried out after the previous layer has finally set. The two cycles of spraying concrete should have a 200mm overlap length, and the undulation difference of the overlap part should be controlled within the allowable range.

[0083] If unfavorable geology is encountered during the construction process, advance geological forecast should be carried out, and small conduit pre-grouting should be used for advance support during construction. The advance small conduit adopts φ42 hot-rolled steel flower pipe with a wall thickness of 4mm, a length of 3.5m, a circumferential spacing of 0.4m, an external insertion angle of 10-15°, and M30 cement slurry (water-cement ratio of 1:1) for grouting. The grouting pressure is 0.3-0.5MPa, and the longitudinal overlap length is not less than 1m. With the system anchor rods, sprayed concrete, hanging mesh and steel support, the secondary lining will be followed up in time after the entire tunnel is connected.

[0084] To prevent cavern collapse, excavation in poor geological conditions should be conducted according to the principles of short advances, weak blasting, prioritizing roof protection, and timely strengthening of support. Appropriate anti-collapse and anti-slip plans and treatment measures should be developed. During construction, a dedicated safety officer should be posted in the work area, safety signs should be posted, and non-construction personnel should be prohibited from entering the work area. Each process should be completed and inspected before the next one can be carried out.

[0085] During tunnel excavation, mechanical excavation and manual labor are used. The surrounding rock conditions of the face should be observed and described in a timely manner after each excavation, the design should be checked, and the stability of the surrounding rock should be judged. Any loose soil blocks or cracks should be removed or supported. During mechanical excavation, manual labor is not allowed to carry out excavation operations at the same time.

[0086] Based on the above technical solution, the upper portion 31 of the inclined shaft is constructed using a step method, with construction being carried out layer by layer from top to bottom. The excavation size is smaller than that of a full-section excavation. Except for the top support required during the excavation of the first layer 311, the tops of the remaining layers do not require support, resulting in a low risk of collapse and high safety. During the construction of the pilot shaft 33, the shaft wall is supported to ensure operational safety. During the expansion excavation, the lower adit 10 is first backfilled with boulders 11, and then the excavation is expanded from top to bottom. This results in high construction efficiency and low safety risks. Once the pilot shaft 33 is penetrated from top to bottom, construction water and fissure water are discharged into the lower adit through the pilot shaft, enabling operations under waterless conditions.

[0087] When the lower part 32 of the inclined shaft was excavated, the support for the lower horizontal tunnel was strengthened, and the rock mass was less disturbed, creating good surrounding rock stability conditions for the inclined shaft excavation. After the expansion layer was completed, timely support was provided to ensure the formation of the excavation contour surface and reduce the impact of blasting vibration on the surrounding rock and adjacent structures, which is beneficial to quality control and structural safety.

[0088] Blasting operations can be performed continuously over multiple cycles, completing 2-3 cycles per day and achieving a depth of 3-5 meters. If a 70-meter-long inclined shaft is constructed using a pilot shaft method or full-face excavation, the total construction period is approximately 90 days. This application saves time setting up a raise boring rig, installing and removing track, and transporting slag, shortening the construction period by nearly 15 days. Compared to the original cost of approximately 2 million yuan for a 70-meter-long inclined shaft using full-face excavation, track removal, or the construction of a full-length pilot shaft followed by expansion, this invention can save approximately 300,000 to 500,000 yuan.

[0089] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0090] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the same. Although the present invention has been described in detail with reference to preferred embodiments, persons skilled in the art should understand that the specific implementation methods of the present invention may still be modified or some technical features may be replaced by equivalents without departing from the spirit of the technical solutions of the present invention, and all of these should fall within the scope of the technical solutions claimed for protection by the present invention.

Claims

1. A method for constructing a gently inclined shaft at a short distance in a surrounding rock fracture zone, characterized by: The inclined shaft is used to connect the upper and lower horizontal tunnels that have been penetrated. The slope of the inclined shaft is 10°~30°, and the construction geological conditions are surrounding rock grade IV and above; The construction method of the inclined shaft comprises the following steps: Divide the construction area: The inclined shaft structure starting from the upper horizontal tunnel and having a slope of less than or equal to 15° is divided into the upper part of the inclined shaft, and the inclined shaft structure located below the upper part of the inclined shaft and connected to the lower horizontal tunnel with a slope greater than 15° is divided into the lower part of the inclined shaft; Construction of the upper part of the inclined shaft: The upper part of the inclined shaft is subjected to blasting construction in layers from top to bottom. The slag and rock produced by the blasting are transported out through the upper horizontal tunnel by vehicles. Support is carried out in time after the blasting excavation. Inclined shaft lower construction: After the upper part of the inclined shaft is constructed, a pilot shaft is excavated by blasting in layers on the bottom surface. The slag generated by the excavation of the pilot shaft is lifted to the wellhead of the pilot shaft and transported out in sequence through the upper part of the inclined shaft and the upper horizontal tunnel by vehicles. After the pilot shaft is excavated through the lower horizontal tunnel, the position of the lower horizontal tunnel located at the lower part of the inclined shaft is backfilled with rocks. The pilot shaft is then expanded in layers from top to bottom to the designed boundary line. The slag enters the lower horizontal tunnel through the pilot shaft and is discharged from the lower horizontal tunnel. After the excavation is expanded to penetrate the top of the lower flat tunnel, the blocks of stone backfilled in the lower flat tunnel are transported out through the lower flat tunnel, and the construction of the inclined shaft is completed.

2. The method for constructing a gently inclined shaft with a short distance in a surrounding rock fracture zone according to claim 1 is characterized in that: The upper part of the inclined shaft is subjected to layered blasting construction, and the specific construction steps of each layer include: Measurement and hole layout: measurement and layout are carried out at the excavation site of the upper horizontal tunnel, and blasthole positions are laid out on the tunnel face according to the requirements of the drilling and blasting plan design; Drilling, charging, and blasting: Drill the blastholes on the tunnel face. After drilling is completed, charge the blastholes with explosives, evacuate personnel, and detonate for blasting. Slag removal: Use an excavator to loosen the rocks, and use vehicles to transport the slag out through the upper level tunnel; Support: After the excavation is completed, the initial spraying is carried out in time. After the initial spraying is completed, support is carried out on the top and both sides; When the excavation slope exceeds the maximum climbing slope of the vehicle, the construction of the lowest layer of the upper part of the inclined shaft is completed, and the excavation of the upper part of the inclined shaft is completed.

3. The method for constructing a gently inclined shaft with a short distance in a surrounding rock fracture zone according to claim 1 is characterized in that: During the construction of the upper part of the inclined shaft, the blast holes must be kept parallel to each other during the drilling process. The order of bottom first and top later is adopted. After each hole is made, the hole mouth is sealed with a flexible material to prevent the hole from being covered by blocks falling from above.

4. The method for constructing a gently inclined shaft with a short distance in a surrounding rock fracture zone according to claim 2 is characterized in that: After the excavation of the uppermost layer of the inclined shaft is completed, the top arch and the arch frames on both sides are installed, anchor rods and mesh are hung, and then the second shotcrete construction is carried out until the designed thickness is reached; After the construction of the top layer is completed, there is no need to support the top of the excavation of the remaining layers. The steel arch frames on both sides are extended and connected with connecting plates. Locking anchor rods are installed at the connection parts of the arch frames on each side and welded to the arch frames. The arch frames are connected with steel bars with a circumferential spacing of 0.5m.

5. The method for constructing a gently inclined shaft with a short distance in a surrounding rock fracture zone according to claim 1 is characterized in that: When blasting the upper part of the inclined shaft, the blasting holes are charged with columnar continuous charges, and the peripheral holes are charged with air interval charges. The charges should be dense and well blocked. After the blasting is completed, ventilation and smoke dispersion are carried out through the press-in ventilation ducts at the hole until the concentration of harmful gases is reduced to the specified standard, and then the slag removal process is carried out on site.

6. The method for constructing a gently inclined shaft with a short distance in a surrounding rock fracture zone according to claim 1 is characterized in that: Before the construction of the upper part of the inclined shaft, the lower horizontal tunnel needs to be initially supported; After the construction of the upper part of the inclined shaft is completed and before the construction of the pilot shaft, the initial support of the lower horizontal tunnel is strengthened to form a strengthened support structure; After the excavation and support of the pilot shaft is completed, the arch I-beam of the reinforced support structure of the lower horizontal tunnel in the pilot shaft area is removed, and then the block stones are backfilled to prevent collapse during the excavation of the inclined shaft. After the excavation is completed, the blocks of stone are transported out through the pilot shaft and the lower horizontal tunnel.

7. The method for constructing a gently inclined shaft with a short distance in a surrounding rock fracture zone according to claim 1 is characterized in that: During the construction of the pilot shaft, excavation blasting is carried out on a narrow free-facing surface, using a small-aperture shallow-eye segmented micro-difference blasting method, where two adjacent explosive packs or front and rear rows of explosive packs are detonated in sequence at intervals of milliseconds to reduce the blasting vibration effect.

8. The method for constructing a gently inclined shaft with a short distance in a surrounding rock fracture zone according to claim 7 is characterized in that: When the pilot well is excavated, the accumulated water in the pilot well is promptly removed by using a slag bucket to lift out the mud and water together or by excavating a water collection pit on one side of the hole bottom and draining it with a water pump; In order to prevent collapse and ensure construction safety, C25 shotcrete is used for initial support in each excavation layer. When the surrounding rock stability is poor, spaced ring beam concrete support is used with a spacing of no more than 3m.

9. The method for constructing a gently inclined shaft with a short distance in a surrounding rock fracture zone according to claim 1 is characterized in that: The lower part of the inclined shaft is excavated by smooth blasting and precisely laid out using infrared laser positioning technology. The surrounding holes are all drilled on the designed contour line, and the drill holes are slightly inclined outward by 2 to 3 degrees. The drill holes are kept parallel to each other, and the bottoms of the holes are at the same elevation.

10. The method for constructing a gently inclined shaft with a short distance in a surrounding rock fracture zone according to claim 1 is characterized in that: When the lower part of the inclined shaft is excavated in layers, the support construction includes the following steps: spraying a layer of 3-5 cm thick concrete immediately after excavating one layer, erecting / extending the steel arch frame, setting the system anchor rods, laying the steel mesh, and spraying the second layer of concrete; When expanding the next layer, repeat the above support construction steps.

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