Hard rock tunnel carbon dioxide gas fracturing and heading machine combined excavation construction method

Abstract

The invention discloses a hard rock tunnel carbon dioxide gas fracturing and cantilever heading machine combined excavation construction method. The construction method sequentially comprises the steps of construction preparation, advanced forecasting, surveying and setting out, fracturing hole drilling, fracturing pipe series connection plugging, crack and nest groove forming through electrified fracturing, heading machine in-place cutting and deslagging, primary supporting and circulating propelling. According to the method, under the conditions that the rock strength is larger than 60 MPa and the surrounding rock is complete, the rock breaking efficiency of the heading machine is improved, drill bit abrasion is relieved, and the vibration influence on surrounding structures is reduced; carbon dioxide fracturing operation is easy and convenient, noise is small, environmental disturbance is small, combined tunneling can control over-excavation and under-excavation, the forming quality is improved, the situation that operators get close to the tunnel face is reduced, over-excavation and over-filling cost is reduced, and energy conservation, emission reduction and cost optimization are achieved.

Description

Technical Field

[0001] This invention belongs to the field of tunnel engineering construction technology, specifically relating to a method for combined excavation of hard rock tunnels using carbon dioxide gas fracturing and tunnel boring machines. Background Technology

[0002] With the rapid development of national water conservancy, the construction of small-section hydraulic tunnels has become an important part of water conservancy projects. These tunnels are characterized by small cross-sections, shallow depths, variable surrounding rock, difficult construction organization, and numerous environmental constraints. Currently, small-section tunnel excavation mainly employs two methods: blasting excavation and non-blasting excavation. Blasting excavation refers to the method of excavating rock through drilling, charging explosives, and blasting. This method has the advantages of strong adaptability to geological conditions and low excavation costs, and is particularly suitable for construction in hard rock caverns. However, it has disadvantages such as higher construction safety risks, strict management of explosives, complex approval processes, significant environmental impact from blasting vibrations, difficulty in blasting control, and prominent over- and under-excavation issues. Non-blasting excavation methods commonly used include cantilever tunneling, pipe jacking, TBM (tunnel boring machine), hydraulic fracturing, and water-jet drilling. Mechanized construction offers advantages such as high efficiency, fast construction progress, and minimal over- and under-excavation, but its overall cost is slightly higher than blasting excavation.

[0003] Against this backdrop, based on past experience in similar projects, this paper innovates traditional construction techniques and provides a combined carbon dioxide gas fracturing and cantilever tunneling method for excavating tunnels in hard rock. This method solves the problem that the efficiency of cantilever tunneling machines is greatly reduced when the rock strength is greater than 60 MPa and the surrounding rock is relatively intact during existing tunnel excavation, while controlling the vibration impact on surrounding structures. This achieves rapid, safe, and efficient construction. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for excavating hard rock tunnels by combining carbon dioxide gas fracturing with tunnel boring machine, which can reduce drill bit wear, reduce vibration impact on surrounding structures, reduce noise and environmental disturbance, improve forming quality and reduce over-excavation and over-filling costs.

[0005] The technical solution of this invention is as follows: A method for excavating hard rock tunnels using a combination of carbon dioxide gas fracturing and a tunnel boring machine includes the following steps: Step 1, Construction Preparation: Complete equipment selection, assembly and debugging, lay power cables, install ventilation equipment and prepare construction materials; Step 2, Advanced Geological Prediction: The geological and hydrological conditions ahead of the tunnel face are detected by combining ground-penetrating radar with advanced horizontal drilling. Step 3, Measurement and layout: Use a total station to lay out the excavation outline and install a laser guide on the completed initial support surface to form the excavation pointing reference; Step 4: Drilling fracture holes: Drill fracture holes at the preset positions on the working face; Step 5, Installation and sealing of fracturing tube: Insert the disposable carbon dioxide fracturing tube into the fracturing hole and fill and seal it. At the same time, connect the power lines of the fracturing tube in series and perform insulation and waterproofing treatment. Step 6, Power-induced fracturing: After completing the network inspection, implement safety precautions and evacuate personnel and equipment to a safe distance. After issuing a power-on signal, power-induced fracturing causes the rock mass at the working face to crack and form a pit. Step 7, Tunneling machine positioning: Start the cantilever tunneling machine, make the cutting head horizontal, and slowly advance the tracks until the cutting head cuts into the predetermined depth of the working face. Lower the shovel plate so that the shovel tip contacts the ground. Step 8, Excavation: Using the pilot tunnel formed by the fracturing and the cracked rock mass, cut and break the rock and complete the muck removal; Step 9, Initial Support: Under full-face excavation conditions, extend the distance between the support section and the tunnel face. During support, the tunneling machine retreats to a position that will not affect subsequent construction. If the surrounding rock at the tunnel face is poor, follow up with support. After completion, proceed to the next cycle.

[0006] Furthermore, in step 4, the fracture hole is drilled using a hand-held pneumatic drill with a hole diameter of 50 mm, a drilling depth of 2.0 m to 2.2 m, and a row spacing of 0.3 m by 0.6 m between holes.

[0007] Furthermore, in step 4, the borehole spacing and row spacing are dynamically adjusted according to the rock strength and the fracturing effect of each operation.

[0008] Furthermore, in step 3, five laser guides are installed, respectively located at the arch crown, arch foot, and sidewall. They are connected and positioned to the pre-reserved steel bars of the initial support by steel wire binding. The laser guides are checked and verified in each cycle, and are moved forward once every 50m of excavation.

[0009] Furthermore, in step 5, after the fracturing tube is inserted into the hole, at least 30cm should be left at the hole opening, and one or more of the following materials should be selected as filling materials: drilling mud, anchoring agent, wooden wedges, and polyurethane, and compacted and sealed in layers.

[0010] Furthermore, in step 5, the disposable carbon dioxide fracturing tubes are connected in series, and the joints are covered with insulating and waterproof tape.

[0011] Furthermore, in step 6, after the network connection is completed, a safety warning should be issued immediately, and personnel and equipment in the excavation area should be evacuated to a distance of more than 100m before power is applied to cause cracking.

[0012] Furthermore, in step 8, a right-handed cutting head is selected to perform the cutting. The cutting begins from the bottom, starting from the right to the left, and then the cutting is performed gradually from the bottom to the left or from the top to the left.

[0013] Furthermore, in step 8, a small-diameter cutting head is selected for cutting high-strength rocks.

[0014] The beneficial effects of this invention are: 1. Improve hard rock efficiency and reduce wear and tear: When the rock strength is greater than 60MPa and the surrounding rock is relatively intact, carbon dioxide fracturing is used to pre-form cracks and guide tunnels, which alleviates the problem of significant efficiency reduction caused by the direct cutting of hard rock by the cantilever tunneling machine. At the same time, it reduces drill bit wear and can control the vibration impact on surrounding structures, so as to achieve fast, safe and efficient construction.

[0015] 2. Controlling over- and under-excavation and improving forming quality: The combined construction of carbon dioxide gas fracturing and cantilever tunneling machine is conducive to controlling over- and under-excavation of tunnels, improving tunnel forming effect and excavation quality, and reducing material and process costs caused by "over-excavation and over-filling".

[0016] 3. Reduce disturbance to surrounding rock and improve construction safety: The combined construction method can reduce disturbance to the surrounding rock, improve construction safety, reduce the amount of reserved deformation, and make the excavation face smoother and flatter; at the same time, the excavation by the tunneling machine can reduce the number of workers inside the tunnel, keep personnel away from the working face, reduce safety risks and reduce labor intensity.

[0017] 4. Environmentally friendly and green low-carbon: Carbon dioxide fracturing is simple to operate, has high safety, and produces less explosive power and noise, causing less disturbance to the surrounding environment. Compared with traditional explosive blasting, it has obvious advantages in energy saving, environmental protection and consumption reduction, and can support the goals of energy saving and efficiency improvement, emission reduction and pollution reduction and cost optimization. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the construction method of a hard rock tunnel using carbon dioxide gas fracturing and a tunnel boring machine combined.

[0019] Figure 2 This is a schematic diagram of the carbon dioxide fracturing hole layout in a method for combined excavation of hard rock tunnels using carbon dioxide gas fracturing and a tunnel boring machine, according to the present invention.

[0020] Figure 3 This is a schematic diagram of the boom tunneling machine construction sequence in a method for combined excavation of hard rock tunnels using carbon dioxide gas fracturing and a tunneling machine, according to the present invention.

[0021] Figure 4 This is a schematic diagram of the muck removal process of a cantilever tunneling machine in a combined excavation method for hard rock tunnels using carbon dioxide gas fracturing and tunneling machine.

[0022] In the diagram: 1-Tunnel excavation edge line; 2-Carbon dioxide gas blasting side hole; 3-Carbon dioxide gas blasting center hole; 4-Cantilever tunneling machine drill bit; 5-Cantilever tunneling machine muck removal system; 6-Muck removal vehicle; 7-Cantilever tunneling machine. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings, so that those skilled in the art can gain a complete understanding of the concept and technical solution of the present invention.

[0024] like Figure 1 As shown in this embodiment, a construction method for hard rock tunnels using carbon dioxide gas fracturing and a combined tunnel boring machine (TBM) is implemented in a cyclical manner, including construction preparation, advanced geological forecasting, surveying and setting out, drilling of fracturing holes, installation and sealing of fracturing pipes, energizing fracturing, positioning of the TBM, tunneling and excavation, initial support, and then proceeding to the next cycle. This method is designed for construction under conditions where the efficiency of the TBM is reduced due to rock strength greater than 60 MPa and relatively intact surrounding rock. By combining fracturing pretreatment with mechanical cutting, the overall efficiency is improved and the vibration impact on surrounding structures is controlled.

[0025] I. Construction Preparation: Construction preparation includes equipment selection, tunneling machine assembly and commissioning, cable installation, ventilation equipment installation, and material preparation. In practice, it is preferable to conduct integrity checks and functional tests on the carbon dioxide fracturing pipe and its power supply line, the tunneling machine cutting head and cutting teeth, the slag removal system, and the air and water supply pipelines and power supply system, and form equipment inspection records. In combination with the cyclic advance and surrounding rock conditions, materials and tools are arranged in a fixed position to ensure the cross-connection of fracturing construction, tunneling construction and support construction.

[0026] II. Advanced Geological Prediction: To understand the engineering geological and hydrological conditions ahead of the tunnel face and reduce the risks of collapse, water inrush, quicksand, and soil erosion, advanced geological forecasting is conducted during construction. The forecasting technology combines ground-penetrating radar with advanced horizontal boreholes to detect geological conditions. To ensure that this combination of ground-penetrating radar and advanced horizontal borehole forecasting can be directly executed on-site, this embodiment preferably follows the following procedure: S1: Set up survey lines on the tunnel face and adjacent tunnel walls for scanning and data acquisition, and simultaneously record the survey line mileage, survey line location, acquisition parameters and coupling status; after acquisition, perform rapid processing and preliminary interpretation to identify the location and range of reflection anomaly zones, and focus on possible sections of fracture zones, weak interlayers, cavities and water-rich structures. S2: Compare and analyze the radar anomalies with the geological sketch of the working face, the lithology of the slag discharge, and the development of joints and fractures to delineate the target area that needs to be verified by drilling, and determine the arrangement principles and number of verification holes based on their location, orientation, and dip angle. S3: Conduct advanced horizontal drilling in the target area according to the predetermined orientation. During the drilling process, continuously record the drilling response and geological phenomena, including changes in drilling speed, stuck drill bits and falling blocks, changes in the particle size and lithology of returned cuttings, and water production in the borehole. After the borehole is completed, observe and record the water production and water-bearing characteristics in the borehole. If necessary, use borehole inspection to verify the fracture and water-bearing status. S4: Verify the correspondence between radar interpretation results and borehole revelation results to form conclusions on the trend of surrounding rock integrity, the degree of fracture zone development, and water-bearing risk within a certain mileage range ahead, and give the risk level and applicable mileage range; S5: Transform the forecast conclusions into actionable measures to guide the determination of construction parameters for the next cycle. This includes at least recommendations for cycle advance adjustment, recommendations for the layout and parameter adjustment of crack-causing holes, recommendations for the timing and reinforcement of initial support, and recommendations for necessary advance drainage or pre-reinforcement. The results should be communicated to the site management personnel as input for subsequent procedures.

[0027] III. Measurement and Setting Out: The tunnel entry survey uses a total station for layout, marking out the excavation outline. After entering the tunnel, five laser guides are installed on the completed initial support surface to replace the total station layout for each cycle. The laser guides are positioned at the arch crown, arch foot, and sidewalls. The pre-reserved steel bars of the initial support are connected to the laser positioning holes using steel wire binding, and the total station is used for measurement and positioning to ensure accurate installation. During construction, the laser guides form red dots on the excavation face, and the on-site operators use the line connecting the dots as the excavation reference line. The laser guides are checked and calibrated for each cycle to prevent instrument vibration or damage from affecting the layout accuracy. The laser guides are moved forward every 50m of excavation, and the layout results are promptly communicated.

[0028] IV. Drilling holes that cause cracks: The fracture holes were drilled using a YT 28 hand-held pneumatic drill, with a hole diameter of 50mm and a depth of 2.0m to 2.2m. The spacing between the drilled holes was 0.3m x 0.6m. The fracture holes were arranged as follows: Figure 2 As shown, the spacing between holes can be dynamically adjusted according to the rock strength and the fracturing effect of each operation. Before drilling, the holes are accurately measured and marked with a total station according to the designed hole positions. After the holes are laid out, the equipment is positioned, the power supply and air and water supply lines are connected, the drill bit is aligned with the hole position and the drilling rig is adjusted to make each hole as perpendicular to the working face as possible. After the drilling rig is firmly fixed, drilling begins, striving to ensure that the bottom of each hole falls on the same cross section. After drilling is completed, the hole is closed after the on-site technicians confirm and sign off. After drilling is completed, the hole opening is protected in a timely manner to prevent soil and gravel from entering the hole and affecting the fracturing tube filling effect.

[0029] V. Installation and sealing of the fracture-causing pipe: The disposable carbon dioxide fracturing tubes are gently, evenly, and slowly inserted into the borehole, avoiding forceful impact. The borehole quality, including angle, diameter, and depth, is verified; boreholes that do not meet the standards are not installed with tubes. After the fracturing tubes are installed, at least 30cm should be left at the borehole opening and then filled and sealed. The filling material should preferably be one or more materials such as drilling mud, anchoring agent, wooden wedges, or polyurethane. Fill and compact the filling material in layers using tools. The denser the backfill on the borehole wall, the more stable the fracturing effect. During the tube installation and filling process, care should be taken to protect the connecting wires to avoid pulling them off and causing loose connections that lead to excessive resistance. The disposable carbon dioxide fracturing tubes are connected in series, and the joints are covered with insulating and waterproof tape to reduce the impact of short circuits or grounding that increase resistance on the fracturing effect. If the circuit performance is unstable or does not meet the standards, the initiation process should be stopped and the problem addressed.

[0030] VI. Cracks caused by electrical current: After the fracturing pipe is installed, all power lines are connected in series, and the joints are wrapped tightly with insulating tape and carefully inspected. After the network is completed, a safety warning is immediately issued, and personnel and equipment in the excavation area are evacuated to more than 100m away. After the safety officer issues the power-on signal, the power is applied to induce fracturing. After fracturing, the next process is carried out when the safety conditions are met.

[0031] VII. Tunneling machine in place: Start the cantilever tunneling machine 7, position the cutting head horizontally and parallel to the equipment, and move the tracks forward slowly until the cutting head cuts into the working face to the predetermined working depth; then lower the shovel plate to the ground so that the shovel tip contacts the ground, while avoiding using the shovel plate to support and lift the equipment, which would affect the stability of the posture.

[0032] VIII. Tunneling and Excavation and Slag Removal: Excavation is carried out using the pilot tunnel formed by fracturing and the fractured rock mass. A right-hand rotary cutting head is preferred. Cutting begins from the bottom, moving from right to left, followed by progressive cutting from left to right and from bottom to top, or from right to left and from top to bottom. Figure 3 As shown; the cutting tooth configuration scheme is determined according to the rock hardness. When the rock strength is high, a small-diameter cutting head is preferred to obtain greater cutting force and stronger rock-breaking ability, thereby reducing the difficulty of tunneling and the consumption of cutting teeth; the thread arrangement of the cutting teeth can be combined with the working conditions to select the optimal cutting head to improve construction efficiency; the excavated slag is loaded into the slag removal system 5 and transported to the slag removal truck 6 for off-site disposal, such as... Figure 4 As shown.

[0033] IX. Initial Support and Cyclic Advancement: Water conveyance tunnels are small-section tunnels. When using a tunnel boring machine to excavate the entire cross-section, the disturbance to the surrounding rock is relatively small. The distance between the support section and the tunnel face can be appropriately increased. During support construction, the tunnel boring machine should be moved back to a position that will not affect subsequent construction. If the surrounding rock at the tunnel face is poor, support should be provided in a timely manner. After completion, the next cycle can begin.

[0034] The above embodiments provide a detailed description of the process organization, key parameters, and on-site operation points of the method of the present invention. Within the scope of the technical concept of the present invention, the spacing between holes, the cutting sequence, and the configuration of cutting teeth can be adaptively adjusted according to the surrounding rock conditions and construction organization.

Claims

1. A method for combined excavation of hard rock tunnels using carbon dioxide gas fracturing and a tunnel boring machine, characterized in that, Includes the following steps: Step 1, Construction Preparation: Complete equipment selection, assembly and debugging, lay power cables, install ventilation equipment and prepare construction materials; Step 2, Advanced Geological Prediction: The geological and hydrological conditions ahead of the tunnel face are detected by combining ground-penetrating radar with advanced horizontal drilling. Step 3, Measurement and layout: Use a total station to lay out the excavation outline and install a laser guide on the completed initial support surface to form the excavation pointing reference; Step 4: Drilling fracture holes: Drill fracture holes at the preset positions on the working face; Step 5, Installation and sealing of fracturing tube: Insert the disposable carbon dioxide fracturing tube into the fracturing hole and fill and seal it. At the same time, connect the power lines of the fracturing tube in series and perform insulation and waterproofing treatment. Step 6, Power-induced fracturing: After completing the network inspection, implement safety precautions and evacuate personnel and equipment to a safe distance. After issuing a power-on signal, power-induced fracturing causes the rock mass at the working face to crack and form a pit. Step 7, Tunneling machine positioning: Start the cantilever tunneling machine, make the cutting head horizontal, and slowly advance the tracks until the cutting head cuts into the predetermined depth of the working face. Lower the shovel plate so that the shovel tip contacts the ground. Step 8, Excavation: Using the pilot tunnel formed by the fracturing and the cracked rock mass, cut and break the rock and complete the muck removal; Step 9, Initial Support: Under full-face excavation conditions, extend the distance between the support section and the tunnel face. During support, the tunneling machine retreats to a position that will not affect subsequent construction. If the surrounding rock at the tunnel face is poor, follow up with support. After completion, proceed to the next cycle.

2. The construction method according to claim 1, characterized in that, In step 4, the fracture hole is drilled using a hand-held pneumatic drill with a hole diameter of 50 mm, a drilling depth of 2.0 m to 2.2 m, and a row spacing of 0.3 m by 0.6 m between holes.

3. The construction method according to claim 1, characterized in that, In step 4, the borehole spacing and row spacing are dynamically adjusted according to the rock strength and the fracturing effect of each operation.

4. The construction method according to claim 1, characterized in that, In step 3, five laser guides are installed, which are placed at the arch top, arch foot and side wall. They are connected and positioned to the pre-reserved steel bars of the initial support by steel wire binding. The laser guides are checked and verified in each cycle, and are moved forward once every 50m of excavation.

5. The construction method according to claim 1, characterized in that, In step 5, after the fracturing tube is inserted into the hole, at least 30cm should be left at the hole opening, and one or more of the following materials should be selected as filling materials: drilling mud, anchoring agent, wooden wedges, and polyurethane, and compacted and sealed in layers.

6. The construction method according to claim 1, characterized in that, In step 5, the disposable carbon dioxide fracturing tubes are connected in series, and the joints are covered with insulating and waterproof tape.

7. The construction method according to claim 1, characterized in that, After the network connection is completed in step 6, a safety warning should be issued immediately, and personnel and equipment in the excavation area should be evacuated to a distance of more than 100 meters before power is turned on to cause cracking.

8. The construction method according to claim 1, characterized in that, In step 8, a right-handed cutting head is used for cutting. First, the cutting starts from the bottom and moves from right to left. Then, the cutting is done from left to right from bottom to top, or from right to left from top to bottom.

9. The construction method according to claim 1, characterized in that, In step 8, a small-diameter cutting head is used to cut the high-strength rock.

Images