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1.2 Structure and Principle of Concrete Shotcreting Machine The concrete shotcreting machine is mainly composed of four parts: the air pipeline system, the feeding mechanism system, the feeding system, and the accelerating agent metering and adding system. The feeding system is the core component. It consists of a hopper, a vibrator, a cam, a rotor, a piston, a rotary lining plate, a coupling plate and the like. The rotor piston in the material chamber moves up and down in the chamber to complete feeding and feeding. The concrete material is forcibly fed into the mixing chamber of the gas and material by the piston and mixed with the compressed air to form a thin flow pattern, which is sent to the nozzle through the pipeline; at the same time, the metering pump pumps the liquid quick-accelerating agent, and is atomized to speed up the passage through the atomizer. After the nozzle is mixed with the concrete. Spray from the nozzle to the sprayed surface. The machine better solves the problem of cohesive plugging of wet mixes in the rotor material cavity, and realizes uniform and continuous feeding of small aggregates and thin flow delivery in pipes.
2. Shotcrete construction process 2.1 Requirements for raw materials 1 Water: No mineral components affecting the performance of concrete, general drinking water standards; 2 Sand: After super-dipping stone after screening, fineness modulus F·M=2.2～2.6 It is appropriate; 3 stone: The maximum particle size must not exceed 15mm; 4 quick-setting coagulants: better with water agent; 5 Concrete slump control: According to the distance from the spray surface, the concrete number and so on. 8-12cm is appropriate.
2.2 The mechanical operation requires that the operator of the concrete spraying machine before starting the machine should do the following:
(1) check the materials used, the material can meet the above requirements before use;
(2) Check the hopper for foreign matter and the speed of the accelerator and adjust the metering pump so that the addition ratio of the accelerator is in accordance with the design requirements for the concrete mix ratio;
(3) Check that the pressure of the pressure controller is suitable for the relevant parameters such as the conveying distance. The general setting value is greater than the working pressure 0.1 ~ 0.2MPa;
(4) take over. Prevent the occurrence of sharp bends and stiffening in concrete pipes;
(5) Check the circuit. Whether the voltage is within the range specified by the machine;
(6) Check whether the direction of rotor movement is consistent with the direction of the target. Observe whether the liquid flow in the suction pipe is normal and whether the nozzle is clogged.
(7) After checking and confirming according to the method above, about half of the mortar is added to the hopper (usually mortar mixing ratio is c:s:w=1:3.5:0.45). Start the main motor and transfer the mortar into the rotor cavity and gas mixture chamber;
(8) Fill the bucket sifter with concrete and vibrate so that the concrete enters the hopper;
(9) After completing the above work flow, turn on and observe the change of wind pressure value; general working wind pressure, spray wall 0.2 ~ 0.5MPa, injection arch 0.3 ~ 0.45MPa, but according to the nozzle discharge conditions to adjust the main air valve The opening degree.
2.3 Sprayed Concrete Construction Method (1) Before spray concrete is sprayed, the following aspects are mainly done: 1 Check loose rock mass and loose body condition by sprayed surface; 2 Dust remove and clean the rock surface to ensure the concrete and rock have Good combination; 3 spraying thickness should be sprayed on the surface before spraying to achieve design indicators.
(2) The following principles should be followed during the operation: 1) Feeding speed should be uniform and continuous, and maintain a certain amount of storage in the hopper; 2) Remove coarse material or other foreign matter with particle size greater than 15mm on the shaker in time; When the nozzle is operated, the nozzle should be perpendicular to the sprayed surface, and the distance should be about 1.0m; 4 The shot should be taken from the bottom to the top when spraying the concrete. The nozzle should be spirally rotated and evenly sprayed to the rock surface. .
(3) On-site quality control. Mainly take the following measures: (1) Check whether the thickness of the sprayed layer on the sprayed surface is the same as that of the set thickness; otherwise, make up the spray to the design thickness; (2) The uneven surface should be promptly filled to flush; 3 pairs. Hollowing or exfoliation layer for chiseling, make-up spray or follow-up reinforcement by grouting method; 4 random drilling or ultrasonic method to check the thickness of the spray layer.
III. Precautions for Construction (1) During the injection process, the machine operator must keep in touch with the sprayer. If any abnormality occurs, it should be able to react in time.
(2) Before slowly opening the main air valve, the system air pressure should not be lower than 0.5 MPa.
(3) Do a good job of various inspections before starting up, including raw materials, hoppers, air pressure, voltage, and pipeline laying.
(4) In case of short-time shutdown, stop the main motor, vibration motor, metering pump, and main air valve, but keep the auxiliary air valve open.
(5) When the hopper is opened, the vibration motor cannot be opened to prevent accidents.
(6) The maximum particle size of concrete aggregates does not exceed 15 mm, and the slump is controlled within the range of 6 to 18 cm.
(7) The concrete feeding must be continuous, and the frequent stoppage during the injection may cause the blocking of the accelerator channel on the nozzle and the material accumulation in the gas mixing chamber.
(8) Strengthen daily maintenance work. Before each injection, check whether the bleeder outlet on the rotor is unblocked. After the operation is completed, clean the inside and outside of the machine in a timely manner. Check whether the hopper ring seal screw is loose or not; combine the wear of the plate and the piston.
(9) Regular maintenance. Pay attention to the wear of the lining plate; the lubricating oil is replaced as scheduled; the quick-setting coagulant tank is cleaned on time.
IV. Conclusions (1) The wet shotcrete construction process is simple and easy to operate, requiring only 2 to 3 skilled workers.
(2) The construction efficiency is high. Normally about 15m3 per hour can be sprayed.
(3) Compared with dry shotcrete construction, wet shotcrete construction has less environmental pollution.
(4) The construction cost is not high and the equipment maintenance is simple.
(5) The construction quality is easy to control and the quality of the concrete can be guaranteed. With high safety, it is particularly suitable for difficult and dangerous construction sites such as tunnel rock bolting and shotcreting and high slope support.
First, the construction principle of sprayed concrete 1.1 Shotcrete construction process characteristics Wet sprayed concrete in China is a new process, because it has a higher production efficiency than dry spray; a large spray thickness; effectively improve the construction operating environment, especially for underground construction; Accelerate the cycle time of the operation, and at the same time, it also ensures the stability and reliability of the concrete quality.