In tunnel engineering, shotcrete is an important process for initial support and secondary lining, and its quality has a significant impact on the durability of the tunnel. This article will provide a detailed introduction to the key technical measures that cannot be ignored in shotcrete construction, helping construction personnel ensure the quality of tunnel concrete and guarantee the safety and durability of the project.

　　1、 Mix proportion design

　　1. Cement to bone ratio control: Control the cement to bone ratio of sprayed concrete between 1:4 and 1:4.5. Reasonably control the amount of cement used to avoid affecting the initial strength growth rate and shrinkage.

　　2. Sand ratio adjustment: The sand ratio should be maintained between 45% and 55% to prevent aggregate blockage.

　　3. Water cement ratio adjustment: The water cement ratio should be between 0.4 and 0.5. Ensure that cement and water are fully hydrated to form a dense cementitious structure, ensuring the strength of sprayed concrete and reducing rebound losses.

　　4. Addition of accelerators: Reasonably add accelerators, and be careful not to cause a decrease in later strength in order to pursue early strength.

　　2、 Precautions for construction preparation

　　1. Equipment inspection: Check the pipelines and joints to ensure that there is no air leakage in the air ducts and no water leakage in the water pipes. Install a valve joint every 40 to 50 meters.

　　2. Thickness marker embedding: Install shotcrete thickness inspection markers and record their exposed length. Pull the line, level with wooden bars while spraying, control the flatness of the spraying surface, and compact the concrete.

　　3. Excavation section inspection: Check the excavation section and make up for any under excavation. Reinforce unfavorable geological areas and provide sufficient lighting on the spraying operation surface.

　　3、 Maintenance measures

　　1. Initial setting leveling: After the initial setting of concrete, leveling should be carried out to avoid damaging the bonding between the internal structure of fresh concrete and the base layer.

　　2. Watering and curing after final setting: The last layer of concrete should be watered and cured for no less than 14 days after the final setting of 2 hours.

　　3. Low temperature maintenance: Water retention maintenance must be carried out when the temperature is below 5 ℃.

　　4、 Concrete thickness detection

　　1. Spray thickness inspection: Within 8 hours after the spraying is completed, drill holes to check the thickness of the reinforcement layer. If it is insufficient, it must be sprayed in a timely manner.

　　2. Thickness error control: The thickness error of the reinforcement layer should be controlled between -5 and+8 millimeters.

　　5、 Concrete strength testing

　　1. Sampling of test specimens: Cut or drill concrete specimens without cracks from the site, meeting the requirements of flatness and verticality.

　　2. Compressive strength test: Control the dispersion of the compressive strength test value of the specimen to ensure the rationality of the data.

　　3. Appearance inspection: Conduct appearance inspection to eliminate hollowing and cracking areas.

　　6、 Dust control measures

　　1. Selection of jet air pressure: Select the jet air pressure through experiments and control the jet force.

　　2. Spray material mixing * *:

　　-Uniformly mix the sprayed material to reduce rebound and dust volume.

　　3. Wet spray secondary mixing: Wet spray secondary mixing is adopted to reduce rebound.

　　4. Control the dosage of accelerators: Strictly control the dosage of accelerators.

　　Through reasonable mix design, meticulous construction preparation, effective maintenance measures, rigorous thickness and strength testing, and scientific dust control, the quality of tunnel shotcrete can be significantly improved, ensuring the safety and durability of the project. These technical measures not only provide practical guidance for construction personnel, but also lay a solid foundation for the smooth progress of tunnel engineering.

　　How to prevent tunnel collapse? Preventing tunnel collapse is an important task in tunnel engineering. It is necessary to start from multiple aspects such as design, construction, material selection, and site management, and implement strict preventive measures to ensure the safety of tunnel construction and operation. The following are some effective measures to prevent tunnel collapse:

　　1. Detailed investigation of geological conditions: Before tunnel construction, conduct a comprehensive geological survey to understand the geological structure, stratum distribution, groundwater conditions, etc., to provide accurate data support for tunnel design and construction.

　　2. Scientific and reasonable design: According to geological conditions and engineering requirements, adopt advanced design concepts and calculation methods to ensure that the tunnel structure has sufficient safety reserves and resistance.

　　3. Choose a suitable construction method: Choose a suitable construction method according to geological conditions, such as shield method, TBM (tunnel boring machine) method, traditional excavation method, etc., and take corresponding support measures.

　　4. Strengthen the design of support structure: According to the geological conditions, design a reasonable support structure, such as steel support, arch frame, shotcrete, etc., to ensure the stability of the tunnel during construction and operation.

　　5. Strictly control the construction quality: Establish a complete quality management system, strictly control every link in the construction process, and ensure that the materials, equipment and processes used meet the requirements of the specifications.

　　6. Strengthen on-site management: Establish an effective on-site management system, strengthen the training and management of construction personnel, ensure the safety and order of the construction site, and prevent man-made accidents.

　　7. Implement real-time monitoring: Install advanced monitoring equipment to monitor the displacement, stress, seepage and other key parameters of the tunnel in real time, timely discover potential dangerous factors, and take corresponding treatment measures.

　　8. Timely deal with hidden dangers: Take timely measures to deal with cracks, seepage, deformation of support structures and other problems that occur during the construction process to prevent the expansion of problems and collapse.

　　9. Regular maintenance and inspection: Carry out regular maintenance and inspection of the built tunnels, timely discover and repair problems that may affect the safety of the tunnels, and extend the service life of the tunnels.

　　Through the comprehensive use of the above measures, the risk of tunnel collapse can be greatly reduced, and the safe construction and smooth operation of tunnel projects can be guaranteed.

　　Concrete wet spraying robotic arm has become the mainstream equipment for support operations in modern tunnel and mining engineering. Its efficient spraying performance and excellent engineering quality have made it occupy an important position in the fields of civil engineering and construction. This article will introduce the characteristics, application fields, and advantages of concrete wet spraying robotic arms in support operations.

　　1、 Characteristics of concrete wet spraying manipulator

　　1. Efficient spraying: The concrete wet spraying robotic arm can achieve continuous and stable spraying operations, improving construction efficiency.

　　2. Excellent spraying quality: The wet spraying process makes the mixing of concrete and cement slurry more uniform, resulting in high density and strong adhesion of the sprayed concrete.

　　3. High degree of automation: Equipped with advanced automatic control systems, it can achieve precise control and remote operation, reduce manual intervention, and improve construction safety.

　　4. Strong adaptability: It can operate stably under various complex geological conditions and is widely used in underground engineering such as tunnels and mines.

　　2、 Application Fields

　　1. Tunnel engineering: During tunnel excavation, concrete wet spraying robots are used for initial support and secondary lining, providing a stable support structure.

　　2. Mining engineering: In mining operations, wet spraying robotic arms are used for roadway support and protection engineering to ensure mining safety.

　　3. Foundation pit support: In deep foundation pit construction, wet spraying robotic arms are used for slope support to prevent collapse and landslides.

　　4. Subway construction: In subway construction, wet spraying robotic arms are used to support shield tunnels and underground stations, ensuring construction safety and structural stability.

　　3、 Advantages in Support Operations

　　1. Improve construction efficiency: Automated operation and continuous spraying significantly shorten the construction period and improve the overall project progress.

　　2. Improve support quality: Wet sprayed concrete has high compactness, strong bonding force, significant support effect, and reduces maintenance costs in the later stage.

　　3. Enhance construction safety: Remote operation reduces the number of times construction personnel enter hazardous areas and lowers safety risks.

　　4. Adapt to complex environments: Wet spraying robotic arms can operate stably in harsh environments such as high temperature, high humidity, and high dust, ensuring the smooth progress of projects.

　　The concrete wet spraying manipulator, as the mainstream equipment for support operations, plays an irreplaceable and important role in modern engineering construction with its efficient, high-quality, and safe construction performance. With the continuous advancement of technology, wet spraying robots will demonstrate their advantages in more fields, providing strong guarantees for engineering quality and construction efficiency.

　　What factors affect the spraying effect of a wet spraying robotic arm? The spraying effect of wet spraying robotic arm is influenced by various factors, mainly including:

　　1. Equipment parameters:

　　The model, specifications, and technical parameters of the wet spraying robotic arm, such as spraying pressure, spraying flow rate, mixing efficiency, etc., directly determine the spraying effect.

　　The design and size of the nozzle, including the diameter and shape of the spray hole, affect the spray mode and atomization effect.

　　2. Operation control:

　　The technical level and experience of the operators, as well as their proficiency in the equipment, directly affect the wet spraying effect.

　　The adjustment of wet spraying parameters, such as water cement ratio, spraying speed, and angle, needs to be precisely controlled according to construction requirements.

　　3. Material properties:

　　The formula and ratio of concrete, including the types and proportions of cement, aggregates, admixtures, and additives, affect its fluidity and bonding properties.

　　The particle size distribution, shape, and surface characteristics of aggregates, as well as their impact on the spraying effect.

　　4. Environmental conditions:

　　The climatic conditions at the construction site, such as temperature, humidity, wind speed, etc., especially wind speed, have a significant impact on the wet spraying effect.

　　The spatial limitations of the construction environment, such as height, width, and layout of obstacles, may restrict the movement range and spraying direction of the wet spraying robot arm.

　　5. Safety measures:

　　The safety regulations and protective measures that must be followed during the wet spraying process, such as wearing appropriate protective equipment to ensure the safety of operators and the surrounding environment.

　　6. Maintenance and upkeep:

　　Regular maintenance and upkeep of the wet spraying robot arm, including cleaning, lubrication, and inspection, to ensure its normal operation and avoid a decrease in spraying effect caused by equipment failure.

　　7. Construction preparation:

　　Before construction, inspect the wet spraying robot arm to ensure that all components are intact and firmly connected, as well as prepare for the construction site, such as laying suitable substrates and setting up necessary support structures.

　　By comprehensively considering these factors and taking corresponding measures to optimize the wet spraying process, the spraying effect of the wet spraying robot can be significantly improved, ensuring construction quality.

　　What are the applicable scope of the three arm arch installation trolley? As an efficient tunnel construction equipment, the three arm arch installation trolley is mainly applicable in the following areas:

　　1. Railway tunnel: In railway tunnel construction, the three arm arch installation trolley can quickly complete the arch installation work inside the tunnel, improve construction efficiency, and ensure the smooth laying of railway lines.

　　2. Highway tunnels: The construction of highway tunnels also requires a large amount of arch installation work. The three arm arch installation trolley can work stably under various geological conditions to ensure construction quality.

　　3. Water conservancy tunnels: In water conservancy construction, such as irrigation channels, hydropower tunnels, etc., the three arm arch installation trolley can help quickly complete the installation of the internal structure of the tunnel, promoting the smooth progress of water conservancy projects.

　　4. Urban rail transit: With the acceleration of urbanization, the construction of urban rail transit is increasing day by day. The three arm arch installation trolley can be effectively applied in the construction of urban rail transit tunnels such as subways and light rails.

　　5. National Defense Engineering: In some special national defense projects, such as military tunnels, underground facilities, etc., the three arm arch installation trolley can provide stable construction support under complex geological conditions.

　　6. Other underground projects: In addition to the above-mentioned application areas, the three arm arch installation trolley can also be applied to other underground projects that require tunnel construction, such as underground shopping malls, underground parking lots, etc.

　　The three arm arch installation trolley has been widely used in the field of tunnel construction due to its high efficiency and safety, making important contributions to the rapid development of modern tunnel construction. With the continuous advancement of technology and the expansion of application scenarios, its scope of application is expected to further expand.

　　Overexcavation refers to the part of the actual excavated section outside the reference line based on the designed excavation contour line. Here are several common explanations:

　　1. Overexcavation in mining: In mining operations, overbreak refers to the situation where the actual volume of rock excavated exceeds the designed or expected excavation boundary during the excavation process. This may be due to the inaccuracy of drilling and blasting techniques, or intentionally done to ensure the stability of the working face. Overexcavation can lead to resource waste and additional costs, as it means extracting more rocks than ores.

　　2. Overexcavation of tunnels and underground engineering: In tunnel construction and other underground engineering projects, oversize or overbreak refers to the actual excavation size of tunnels or caverns being greater than the design size. This may be due to limitations in construction technology, such as insufficient drilling accuracy and improper blasting control. Overexcavation may lead to structural instability, increase support costs, and may require additional repair work.

　　3. Overexcavation under complex geological conditions: In some complex geological conditions, in order to ensure construction safety and structural stability, the construction party may intentionally carry out a certain degree of overexcavation. This can provide more space for subsequent support and lining work to cope with unforeseeable geological changes.

　　4. Overexcavation in construction: In above ground construction, over excavation may refer to digging deeper than the design depth during the foundation excavation process. This situation is usually caused by measurement errors, construction errors, or measures taken to solve foundation problems.

　　How to handle the over excavation part?

　　In basic construction, if over excavation occurs, corresponding measures may need to be taken, such as sand piles, cement fly ash piles, dynamic compaction method, replacement method, preloading method, etc., to ensure the bearing capacity and stability of the foundation.

　　In construction projects such as site excavation or tunnel excavation, there may be three situations: over excavation, under excavation, and exact excavation height. Over excavation requires backfilling of the site, while under excavation requires continued excavation, both of which result in wastage of manpower, material resources, and financial resources. In order to better control costs and schedule, construction workers usually set up temporary leveling elevations based on the site conditions, and promptly inform excavator drivers or laborers of the required excavation thickness according to the elevations.

　　Underexcavation is an engineering term that refers to the phenomenon where the perimeter of the cross-section of a shaft, tunnel, or other underground project is smaller than the design size after blasting. This term is mainly applied in fields such as coal mining, water conservancy and hydropower engineering, and highway tunnels.

　　In the construction of underground projects such as tunnels and tunnels, excavation is usually required according to the designed cross-sectional dimensions. However, due to various reasons, the actual excavated section may have some areas that do not meet the design requirements, which is called under excavation.

　　The reasons for under excavation may include: low drilling accuracy, resulting in the outer insertion angle, opening position, or drilling depth of the surrounding boreholes not meeting the requirements; Improper blasting techniques, such as unreasonable types and structures of explosives, unreasonable arrangement of surrounding holes, or unreasonable blasting design; Construction operations are not standardized, such as inaccurate contour lines, poor control of drilling positioning or drilling angle deviation, insufficient drilling or unauthorized reduction of drilling depth.

　　Underexcavation may bring some problems, such as affecting the quality and safety of the project, requiring additional treatment to meet design requirements, which will increase construction costs and time. In order to reduce the phenomenon of under excavation, a series of measures need to be taken during the construction process, such as improving drilling accuracy, optimizing blasting design, strengthening construction management and measurement work, etc.

　　For example, strengthening the training of drillers to enable them to master drilling techniques proficiently; Reasonably determine the depth of the borehole based on geological conditions and construction requirements; Carefully carry out drilling and blasting design, select appropriate explosive varieties and loading methods; Using high-precision instruments for measurement, accurately drawing excavation contour lines, etc. At the same time, it is necessary to strengthen inspections during the construction process, promptly identify and address any issues of under excavation.

　　In tunnel engineering, it is very important to control over excavation (actual excavation section exceeding the design size) and under excavation, which helps to ensure project quality, reduce costs, improve construction efficiency, and ensure the stability of surrounding rock.

　　Anchor rod trolley is a self moving equipment that drills anchor rod holes in the roof or side walls of underground tunnels and completes partial or complete the installation of anchor rods. With the popularization and development of anchor rod support operations in underground engineering such as mining tunnels and tunnels, anchor rod trolleys have become an indispensable and important equipment in these projects. Their high efficiency, intelligence, multifunctionality, and flexibility provide strong support for modern tunnel construction.

　　1、 Main characteristics of anchor rod trolley

　　Efficiency: The anchor rod trolley can automate the anchor rod support operation, greatly reducing the labor intensity of workers and improving construction efficiency.

　　Intelligence: Modern anchor rod trolleys often use computer-controlled trolley control systems, which can achieve precise positioning and automated operations, improving construction quality and consistency.

　　Multifunctionality: The anchor rod trolley not only has drilling function, but also can complete processes such as grouting and installing anchor rods, realizing the full process mechanization of anchor rod support operation.

　　Flexibility: The design of the anchor rod trolley is flexible and can adapt to the requirements of anchor rod support operations at different heights and angles.

　　2、 Advantages of anchor rod trolley

　　Improve construction efficiency: The anchor rod trolley can automate the anchor rod support operation, greatly shortening the construction period.

　　Improving construction quality: Through a computer-controlled trolley control system, precise positioning and automated operations can be achieved, improving construction quality and consistency.

　　Reduce labor intensity: The application of anchor rod trolleys reduces the labor intensity of workers and improves construction safety.

　　Enhanced adaptability: The design of the anchor rod trolley is flexible and can adapt to the needs of anchor rod support operations at different heights and angles, improving the versatility and adaptability of the equipment.

　　3、 Types of anchor rod trolleys

　　Anchor rod trolleys can be classified into various types based on their structure and function, such as tower type anchor rod trolleys, thruster type anchor rod trolleys, and rotary type anchor rod trolleys. These different types of anchor rod trolleys each have their own characteristics and application scenarios.

　　4、 Application scenarios of anchor rod trolley

　　Tower type anchor rod trolley: composed of drilling arm, hydraulic rock drill, walking mechanism, and control system, etc. The hydraulic rock drill is installed at the top of the drilling arm, and the drilling of anchor rod holes is achieved through the lifting and lowering of the drilling arm.

　　Propeller type anchor rod trolley: Similar to tower type anchor rod trolley, but its hydraulic rock drill is propelled by a thruster, which can swing back, forth, left, and right at a certain angle to meet the needs of different hole positions.

　　Rotating anchor rod trolley: using a rotating frame instead of a propeller, the rotating frame can drill anchor rod holes and install anchor rods, with higher operational efficiency.

　　Anchor rod trolleys are widely used in various underground engineering constructions such as tunnel excavation and underground factory building excavation. It can efficiently perform tasks such as blasting drilling, anchor drilling, automatic clamping and pushing of anchor rods, and automatic grouting, becoming an indispensable equipment in underground engineering.

　　Rock drills are important equipment in engineering construction, and proper storage and maintenance can greatly extend their service life, ensuring that the equipment can operate efficiently when needed. The following is a detailed guide for the storage and maintenance of rock drills:

　　1. Selection of storage environment

　　1.1 Dry Warehouse: Ideally, a dry and non humid warehouse should be selected for storage to prevent equipment from getting damp and rusting. If a suitable warehouse cannot be found and needs to be stored outdoors, a flat wooden board should be laid on the ground, the rock drill should be placed on the board, and covered with high-quality cloth to prevent rainwater and dust from entering.

　　1.2 Equipment arrangement: When multiple rock drills are stored in the warehouse, appropriate distance should be maintained between the equipment. This not only helps with ventilation, but also prevents contact between metals, reducing possible chemical reactions and mechanical damage.

　　2. Preparation before storage

　　2.1 Inspection of Components: Before storage, it is necessary to thoroughly inspect all components of the rock drill to ensure that they are intact and undamaged. If any damage or missing components are found, they should be repaired and replaced in a timely manner to ensure that the machine is in the best condition for the next use.

　　2.2 Battery disassembly and storage: Generally, the battery of a rock drill should be disassembled and stored separately. The battery should be placed in a suitable temperature environment to avoid high temperatures and prevent explosions; Low temperature environments should also be avoided to prevent battery freezing and cracking. Appropriate temperature can extend the lifespan of batteries and ensure their performance.

　　3. Key points of daily maintenance

　　3.1 Regular Inspection: Even long-term stored equipment needs to be regularly inspected to ensure that there are no issues such as rust or loose components. Regular inspections and simple maintenance can prevent small problems from turning into major malfunctions.

　　3.2 Lubrication and Maintenance: Regularly lubricate and maintain the equipment, especially for transmission and moving parts, to ensure smooth operation. Long term storage of equipment may cause the lubricating oil to deteriorate, therefore it needs to be replaced regularly.

　　3.3 Dust prevention measures: During storage, equipment is prone to dust accumulation, especially when stored outdoors. Equipment should be cleaned regularly to maintain surface cleanliness and prevent dust from entering the interior and affecting machine performance.

　　Reasonable storage and maintenance are key to extending the service life of rock drills. Choosing a suitable storage environment, preparing for storage, conducting regular inspections and maintenance can ensure that the rock drill is always in the best working condition when needed, reduce failure rates, and improve work efficiency. Through these measures, the service life of rock drills can be greatly extended, maintenance and replacement costs can be saved, and overall engineering efficiency can be improved.

　　What are the advantages and disadvantages of different types of tunnel support methods? Common tunnel support methods include anchor spray support, anchor rods, shotcrete, steel arches, etc., each of which has its own advantages and disadvantages. The following is a specific introduction:

　　1. Anchor spray support

　　Advantages: Good flexibility and adaptability to different surrounding rock conditions; Strong timeliness, able to be quickly implemented after excavation; Has close adhesion and can be tightly combined with surrounding rock; Excellent depth, able to penetrate deep into the surrounding rock and play a role; Has a certain degree of flexibility, allowing for appropriate deformation of the surrounding rock; It has good sealing properties and can effectively prevent the weathering and loosening of surrounding rocks.

　　Disadvantages: Its support effect is greatly affected by construction quality; For particularly weak or unstable surrounding rocks, it may be necessary to combine other support methods.

　　2. Anchor rod support

　　Advantages: It can effectively support the surrounding rock and improve its stability; It can strongly reinforce the surrounding rock, increase its strength and bearing capacity; Can increase interlayer frictional resistance and enhance the connection between rock layers; Plays a suspension role to prevent local rock mass from loosening and falling off.

　　Disadvantages: The anchoring effect of anchor rods is affected by rock conditions, and the anchoring force may be insufficient in some fractured or weak rock masses; Construction requires certain technical and equipment support; In long-term use, the durability of anchor rods may be affected by factors such as corrosion.

　　3. Spray concrete support

　　Advantages: It can provide timely support for the surrounding rock and limit its deformation; Has unloading function and can share part of the load borne by the surrounding rock; Can reinforce the surrounding rock and improve its overall integrity; Can cover the surface of the surrounding rock and prevent it from loosening and peeling off; The construction is relatively simple and fast.

　　Disadvantages: The quality of sprayed concrete is greatly affected by construction techniques and material mix proportions; High rebound rate may result in certain material waste; The technical requirements for construction personnel are high to ensure the uniformity and compactness of spraying.

　　4. Steel arch support

　　Advantages: The overall stiffness is relatively high, which has a good supporting effect on fractured rock or rock with low rock grades; Can be made and assembled on site, suitable for tunnels with different cross-sections and conditions; It can be well combined with other support methods such as anchor rods and shotcrete to work together and improve support efficiency.

　　Disadvantages: Large amount of steel used, relatively high cost; Installation requires a certain amount of time and manpower; The weight of steel arches is relatively large, and the transportation and installation process is relatively complex.

　　In practical engineering, one or more support methods are usually selected comprehensively based on the specific geological conditions, surrounding rock types, tunnel uses, construction methods, and other factors of the tunnel to achieve safe, economical, and reasonable support effects. At the same time, monitoring and measurement during the construction process are also very important. Based on the monitoring results, support parameters can be adjusted in a timely manner to ensure the stability and safety of the tunnel.