CN108825301B - Quick wall building method for underground coal mine through pile-spraying concrete - Google Patents

Abstract

The invention relates to a method for rapidly building a wall with shotcrete in a coal mine, belonging to the technical field of concrete wall construction and shotcrete in a coal mine, and can solve the problem that the existing method for building a concrete wall in a coal mine is slow, the final strength fails to meet the design requirements, and the There is no effective support for the roof and the problem of small application range. The sand and gravel, cement, JCT‑1 shotcrete admixture and accelerator are mixed evenly in a certain proportion in a wet state and then loaded into the jet machine. The wet mixture is transported along the pipeline to the nozzle, mixed with water and sprayed at high speed to build the wall, a new method for rapid construction of concrete walls in coal mines. According to the method of the invention, the wall body is easy to form, the initial setting time is short, and the pile spray forming has high initial strength, no slippage and falling deformation, and the thickness of the wall body is not limited.

Description

A rapid construction method of sprayed concrete for underground coal mine

technical field

The invention belongs to the technical field of concrete walls and shotcrete in underground coal mines, and particularly relates to a method for rapidly building walls with shotcrete in coal mines.

Background technique

Concrete has become one of the most important civil engineering materials due to its advantages of high strength, integrity and durability. It is mixed with water in a certain proportion (it may contain admixtures and admixtures), and the agitated concrete is poured into the set formwork, compacted and formed, and the formwork is removed after curing and hardening. The stereotyped formwork is very important to the structural size and forming quality of the concrete wall. The unqualified setting of the stereotyped formwork can cause quality defects such as slurry leakage, poor verticality and flatness of the concrete wall, and honeycomb pitted surface. In addition, the process of setting up and dismantling the formwork accounts for more than half of the work of constructing the concrete wall, which seriously restricts the construction speed of the concrete wall.

Confined walls, chambers and other working space walls often need to be constructed underground in coal mines. Due to the limitation of working space and construction environment, the construction of concrete walls can only be done by manual mixing on site or by low-power equipment. , the material ratio is not easy to control, the wall building efficiency is low, the maintenance time is long, and the maintenance is easily affected by the underground environment, so that the final strength of the wall does not meet the design requirements, which restricts the popularization and use of concrete in coal mines.

At present, materials and stones are mostly used to build walls in coal mines. However, in the process of building materials and stone walls, a lot of heavy manual labor is required for material and stone transportation and masonry. Due to the poor underground working environment, accidents such as smashing and other accidents are prone to occur in the process of handling and masonry. In addition, another defect of the masonry stone wall is that due to the size of the stone, it is difficult to fill the final gap between the masonry stone wall and the roof, and can only be filled with crushed stone or mortar. The strength of the joint is obviously insufficient, and it cannot form an effective support for the roof, and cannot play the supporting role of the wall on the roof, so that the roof has a certain range of sinking deformation space, which is not conducive to supporting the roof through the masonry wall.

At present, shotcrete is mainly used in the initial or permanent support of tunnels and roadways, foundation pit slope support, structural reinforcement and maintenance and other fields. In order to ensure long-distance transportation and no problems such as caking and blocking of pipes during transportation, the sprayed concrete must have good workability, but the forming thickness should not be too large, otherwise it will slip and fall. Shotcrete is mostly used in coal mines for single-layer lining support on the surface of underground space structures such as roadways, but the thickness of shotcrete is usually less than 100mm. If the shotcrete is too thick, quality problems such as cracking and falling off will occur. Therefore, the spraying process can only be used. Form a spray layer with a smaller thickness.

In order to improve the early strength of shotcrete, a certain proportion of accelerator will be added during the spraying process. Although the ordinary quick-setting agent shortens the initial setting time of shotcrete, it will greatly reduce the medium-term strength of the concrete, and the strength will be reduced by more than 30% after 28 days of standard curing. Taking the C35 concrete added with ordinary accelerators as an example, the concrete strength after standard curing for 28 days is only 18~19MPa, and the pressure reduction ratio is 48.6%.

The patent of "a shotcrete for mining and its preparation method" with the publication number of "CN 107522442 A" can be obtained in the published literature, which mainly proposes a commercial preparation method of shotcrete material for underground coal mines, which is only by The provided material ratio enables the jetting slurry to meet the construction requirements of underground coal mines in terms of strength after hardening, and reduces the rebound rate to a certain extent, but it does not specify the application site of coal mines and the maximum spray layer thickness that can be achieved. It is still limited to forming a concrete sprayed layer with a small thickness.

Constructing concrete walls in coal mines can give full play to the advantages of high strength and integrity of the walls, and is of great significance to promoting safe production in coal mines. In the published literature and the currently used pouring or spraying concrete methods, there is no method for constructing concrete walls by pile spraying. In order to popularize the application of concrete in building walls and other places of use in coal mines, it is urgent to seek a method that simplifies the traditional pouring concrete process, does not require formwork and dismantling, and improves the efficiency of building walls under the premise of meeting the requirements of use. A new method for rapid construction of concrete walls by spraying in coal mines, which can replace masonry stone walls and traditional formwork pouring concrete walls and save labor costs.

SUMMARY OF THE INVENTION

Aiming at the problems of the existing method of constructing concrete walls underground in coal mines, the speed is slow, the final strength cannot meet the design requirements, the effective support for the roof cannot be formed, and the scope of application is small, and the invention provides a rapid construction of shotcrete for underground coal mines. In the present invention, the sand and gravel, cement, JCT-1 shotcrete admixture and quick-setting agent are mixed uniformly in a certain proportion in a wet state and then loaded into the sprayer, and the wet mixture is transported along the pipeline to the sprayer with compressed air It is mixed with water and sprayed at high speed to build the wall.

The present invention adopts following technical scheme:

A method for rapidly building a wall with shotcrete in a coal mine, comprising the following steps:

The first step is to knock on the top to remove the live gangue in the range of the top plate of the wall designed and constructed in the coal mine, remove the scum on the bottom plate of the design wall and find the hard bottom;

The second step is to place prefabricated steel cages within the wall construction range, and use 16# binding wires to bind and connect the steel cages; the width of the steel cages is consistent with the width of the wall to control the size of the wall; the height and length of the steel cages It is equal to the height and length of the designed construction wall;

In the third step, according to the volume of the concrete wall constructed by the underground shotcrete, prepare the shotcrete raw materials on the ground according to the mass ratio of cement: sand: stone: JCT-1 shotcrete admixture of 1 : 2 : 2 : 0.06 , the construction of 1m ³ concrete wall by the shotcrete process requires 589.04Kg of cement, 1178.08Kg of sand, 1178.08Kg of stones, and 35.34Kg of JCT-1 shotcrete admixture;

The fourth step is to fully wet the stones with water and put them into the mixer, add the JCT-1 shotcrete admixture to the mixer, start the mixer and start mixing, so that the stones and the JCT-1 shotcrete admixture are evenly mixed;

The fifth step, when the stones in the mixer and the JCT-1 shotcrete admixture are evenly mixed, add sand and cement into the mixer, and continue to mix until the mixture is uniform to obtain a concrete mixture;

The sixth step is to load the mixed concrete mixture into a truck and transport it to the underground spraying wall site, continuously add the mixed concrete mixture into the hopper of the jet machine and start the stirring, open the water pipe valve at the spray gun and automatically add liquid. Accelerator pipeline valve, adjust the flow rate of the water pipe valve, control the water-cement ratio of the concrete at the outlet of the spray gun to 0.4~0.5, connect the pressure air pipeline of the sprayer, start the pneumatic vibrator and the feeding system, and start the pile spraying. Wall work, in the process of stacking and spraying the wall, the spray gun makes a continuous spiral circular motion, the diameter of the spiral is 20~30 cm, and the latter circle covers 1/3 of the previous circle. The side is leveled with the wall, the unevenness of the wall surface is less than 10mm, and the spraying route runs in an "S" shape from bottom to top within the range of the length and height of the designed wall;

The seventh step, when the wall formed by the stacking spray reaches the design height, stop feeding into the ejector hopper, and confirm that there is no remaining material in the ejector hopper and when there is no more material ejected from the spray gun, close the automatic adding liquid accelerator pipeline. valve, and then turn off the pneumatic vibrator; add water to the hopper of the ejector, clean the feeding system and conveying pipeline, and finally turn off the air pressure, water pressure and power supply, clean the pipeline for adding liquid accelerator automatically and clean the spray debris around the machine;

The eighth step, spraying and curing the concrete wall after 2 hours. Sprinkling and curing every 8 hours for a total of 7 days. The maintenance water is the same as the heap spraying water.

The standard of pile spray construction is that the arch of the wall is smooth, the two sides are smooth, and there is no obvious unevenness as a whole (subject to the unevenness of the wall surface formed by pile spraying not exceeding 10 mm), the wall is connected to the top and the joints are tight. Leave no gaps.

Preferably, the cement is Portland cement, and the strength grade is not lower than 32.5Mpa.

The stones are crushed stones or pebbles or a mixture of the two, and the particle size is 5-15 mm.

The sand is medium sand or coarse sand, the fineness modulus is greater than 2.5, the moisture content is 5-7%, and the mud content is less than or equal to 3%.

The spraying machine is a rotor type-II type spraying machine, and the spraying gun is a double-water ring conical spraying head; The water flow is in the form of a cross network, which fully wets the material.

The wind pressure in the spraying process of the jet machine is 0.12-0.17MPa, and the water pressure is 0.18-0.21MPa.

JCT-1 shotcrete admixture is an inorganic nano-scale material refined by mechanical grinding method. It is non-toxic, tasteless, non-flammable, with a bulk density of 200~300Kg/m ³ , a density of 2.1~2.3g/cm ³ , a particle size of 0.3~0.5μm, and no adverse effects on the human body during use. When JCT-1 shotcrete admixture is used in the test, the strength of C35 concrete after standard curing for 28 days can reach 35~36MPa, and there is no depressurization loss. JCT-1 shotcrete admixture is a shotcrete admixture developed by Shanxi Jichangtai Mining Engineering Technology Co., Ltd. The use of JCT-1 shotcrete admixture can increase the cohesion of the shotcrete layer without shrinking, improving the Early strength and final strength of concrete, reducing splashing and rebounding, forming fast, increasing the thickness of spray layer, and compacting the top.

The reinforcement cage placed in the spray wall is composed of steel mesh with a mesh size of 100mm welded by 8# steel bars and connecting steel bars. The width of the steel mesh is the design width of the spray wall, and the height of the steel mesh is the height of the spray wall. The design height is 0.5m and the length of the connecting bars is 1.0m.

There should be at least two construction workers for the construction of walls by spraying and spraying, one of whom is responsible for spraying with a hand-held sprinkler, the other is responsible for auxiliary lighting and liaison, and observes the safety of surrounding rocks in the workplace and the quality of the sprayed wall.

The beneficial effects of the present invention are as follows:

The method of the invention does not need to set up formwork, and can realize the construction of concrete wall by pile spraying by using ordinary concrete spraying machine. Falling deformation, the wall thickness is not limited.

Compared with the prior art, the construction method of the spraying process of the present invention fills the blank of the construction of concrete walls by spraying under the coal mine. By adding a JCT-1 shotcrete admixture with high cohesiveness when preparing the mixture, the cohesiveness of the concrete sprayed at the nozzle is improved, and it can be compacted and formed by itself without setting up a formwork, which simplifies the underground coal mine. The process of building a concrete wall liberates labor intensity, improves efficiency, and saves the cost of building walls. The speed of the sprayed concrete is high, and any narrow gap can be filled, so that the contact between the wall and the top plate and the help is tight.

The pile spraying process of the invention has the advantages of fast construction speed, convenient operation, no loss of concrete strength and low cost, and meets the safety production requirements of coal mines. The speed of building a wall by the stack spraying process is mainly related to the jetting capacity of the jet. When the jetting capacity of the jetting machine meets the requirements, the speed of the stacking jetting process can reach 7~10m ³ /h, which can improve the wall building speed and reduce the labor of workers It is of great significance to improve the strength, shorten the construction period, and promote the safe production of coal mines.

Description of drawings

Fig. 1 is the process flow diagram of the present invention;

Fig. 2 is a schematic diagram of the structure of the jet of the present invention;

Fig. 3 is the structure schematic diagram of the reinforcement cage placed in the pile spray construction wall of the present invention;

Fig. 4 is a schematic diagram of the process of stacking spraying and building a wall according to the present invention, and the arrow direction of the curve in the figure is the stacking spraying direction;

Fig. 5 is a schematic diagram of the final wall body of the present invention;

Among them: 1-pressure air source; 2-system air pressure gauge; 3-working air pressure gauge; 4-hopper; 5-mixing ring; 6-nozzle; 7-feeding system; 8-main air valve; 9-pipe Road; 10- Auxiliary Air Valve; 11- Atomizer; 12- Liquid Accelerator Tank; 13- Metering Pump; 14- Clear Water Tank; 15- Reinforcement Mesh; Shotcrete wall; 19-base plate; 20-side help.

Detailed ways

A method for rapidly building a wall with shotcrete in a coal mine, comprising the following steps:

The first step is to knock on the top to remove the live gangue in the range of the top plate of the wall designed and constructed in the coal mine, remove the scum on the bottom plate of the design wall and find the hard bottom;

The second step is to place prefabricated steel cages within the wall construction range, and use 16# binding wires to bind and connect the steel cages; the width of the steel cages is consistent with the width of the wall to control the size of the wall; the height and length of the steel cages It is equal to the height and length of the designed construction wall;

In the third step, according to the volume of the concrete wall constructed by the underground shotcrete, prepare the shotcrete raw materials on the ground according to the mass ratio of cement: sand: stone: JCT-1 shotcrete admixture of 1 : 2 : 2 : 0.06 , the construction of 1m ³ concrete wall by the shotcrete process requires 589.04Kg of cement, 1178.08Kg of sand, 1178.08Kg of stones, and 35.34Kg of JCT-1 shotcrete admixture;

The fourth step is to fully wet the stones with water and put them into the mixer, add the JCT-1 shotcrete admixture to the mixer, start the mixer and start mixing, so that the stones and the JCT-1 shotcrete admixture are evenly mixed;

The fifth step, when the stones in the mixer and the JCT-1 shotcrete admixture are evenly mixed, add sand and cement into the mixer, and continue to mix until the mixture is uniform to obtain a concrete mixture;

The sixth step is to load the mixed concrete mixture into a truck and transport it to the underground spraying wall site, continuously add the mixed concrete mixture into the hopper of the jet machine and start the stirring, open the water pipe valve at the spray gun and automatically add liquid. Accelerator pipeline valve, adjust the flow rate of the water pipe valve, control the water-cement ratio of the concrete at the outlet of the spray gun to 0.4~0.5, connect the pressure air pipeline of the sprayer, start the pneumatic vibrator and the feeding system, and start the pile spraying. Wall work, in the process of stacking and spraying the wall, the spray gun makes a continuous spiral circular motion, the diameter of the spiral is 20~30 cm, and the latter circle covers 1/3 of the previous circle. The side is leveled with the wall, the unevenness of the wall surface is less than 10mm, and the spraying route runs in an "S" shape from bottom to top within the range of the length and height of the designed wall;

The seventh step, when the wall formed by the stacking spray reaches the design height, stop feeding into the ejector hopper, and confirm that there is no remaining material in the ejector hopper and when there is no more material ejected from the spray gun, close the automatic adding liquid accelerator pipeline. valve, and then turn off the pneumatic vibrator; add water to the hopper of the ejector, clean the feeding system and conveying pipeline, and finally turn off the air pressure, water pressure and power supply, clean the pipeline for adding liquid accelerator automatically and clean the spray debris around the machine;

The eighth step, spraying and curing the concrete wall after 2 hours. Sprinkling and curing every 8 hours for a total of 7 days. The maintenance water is the same as the heap spraying water.

The standard of pile spray construction is that the arch of the wall is smooth, the two sides are smooth, and there is no obvious unevenness as a whole (subject to the unevenness of the wall surface formed by pile spraying not exceeding 10 mm), the wall is connected to the top and the joints are tight. Leave no gaps.

Preferably, the cement is Portland cement, and the strength grade is not lower than 32.5Mpa.

The coarse bone particles are crushed stones or pebbles or a mixture of the two, and the particle size is 5-15 mm.

The fine bone particles are medium sand or coarse sand, the fineness modulus is greater than 2.5, the moisture content is 5-7%, and the mud content is less than or equal to 3%.

The spraying machine is a rotor type-II type spraying machine, and the spraying gun is a double water ring conical spraying head; Wet the material well.

The wind pressure in the spraying process of the jet machine is 0.12-0.17MPa, and the water pressure is 0.18-0.21MPa.

JCT-1 shotcrete admixture is an inorganic nano-scale material refined by mechanical grinding method. It is non-toxic, tasteless, non-flammable, with a bulk density of 200~300Kg/m ³ , a density of 2.1~2.3g/cm ³ , a particle size of 0.3~0.5μm, and no adverse effects on the human body during use. When JCT-1 shotcrete admixture is used in the test, the strength of C35 concrete after standard curing for 28 days can reach 35~36MPa, and there is no depressurization loss.

The reinforcement cage placed in the spray wall is composed of steel mesh with a mesh size of 100mm welded by 8# steel bars and connecting steel bars. The width of the steel mesh is the design width of the spray wall, and the height of the steel mesh is the height of the spray wall. The design height is 0.5m and the length of the connecting bars is 1.0m.

There should be at least two construction workers for the construction of walls by spraying and spraying, one of whom is responsible for spraying with a hand-held sprinkler, the other is responsible for auxiliary lighting and liaison, and observes the safety of surrounding rocks in the workplace and the quality of the sprayed wall.

Claims (6)

1. a method for rapidly building walls with shotcrete for underground coal mines, is characterized in that: comprise the steps: The first step is to knock on the top to remove the live gangue in the range of the top plate of the wall designed and constructed in the coal mine, remove the scum on the bottom plate of the design wall and find the hard bottom; The second step is to place prefabricated steel cages within the wall construction, and use 16# binding wires to bind and connect the steel cages; the width of the steel cage is the same as the width of the wall, and the height and length of the steel cage are the same as the height of the designed wall. is equal to the length; The third step, according to cement: sand: stone: the mass ratio of JCT-1 shotcrete admixture is 1: 2: 2: 0.06 to prepare shotcrete raw materials; The fourth step is to fully wet the stones with water and put them into the mixer, add the JCT-1 shotcrete admixture to the mixer, start the mixer and start mixing, so that the stones and the JCT-1 shotcrete admixture are evenly mixed; The fifth step, when the stones in the mixer and the JCT-1 shotcrete admixture are evenly mixed, add sand and cement into the mixer, and continue to mix until the mixture is uniform to obtain a concrete mixture; The sixth step is to load the mixed concrete mixture into a truck and transport it to the underground spraying wall site, continuously add the mixed concrete mixture into the hopper of the jet machine and start the stirring, open the water pipe valve at the spray gun and automatically add liquid. Accelerator pipeline valve, adjust the flow rate of the water pipe valve, control the water-cement ratio of the concrete at the outlet of the spray gun to 0.4~0.5, connect the pressure air pipeline of the sprayer, start the pneumatic vibrator and the feeding system, and start the pile spraying. Wall work, in the process of stacking and spraying the wall, the spray gun makes a continuous spiral circular motion, the diameter of the spiral is 20~30 cm, and the latter circle covers 1/3 of the previous circle. The side is leveled with the wall, the unevenness of the wall surface is less than 10mm, and the spraying route runs in an "S" shape from bottom to top within the range of the length and height of the designed wall; The seventh step, when the wall formed by the stacking spray reaches the design height, stop feeding into the ejector hopper, and confirm that there is no remaining material in the ejector hopper and when there is no more material ejected from the spray gun, close the automatic adding liquid accelerator pipeline. valve, and then turn off the pneumatic vibrator; add water to the hopper of the ejector, clean the feeding system and conveying pipeline, and finally turn off the air pressure, water pressure and power supply, clean the pipeline for adding liquid accelerator automatically and clean the spray debris around the machine; In the eighth step, the sprayed concrete wall starts to be sprayed for maintenance after 2 hours, and is sprayed for maintenance every 8 hours for a total of 7 days. 2 . The method for rapidly building walls with shotcrete for underground coal mines according to claim 1 , wherein the cement is Portland cement, and the strength grade is not lower than 32.5Mpa. 3 . 3 . The method for rapidly building walls with shotcrete for underground coal mines according to claim 1 , wherein the stones are crushed stones or pebbles or a mixture of the two, and the particle size is 5-15 mm. 4 . 4. The method for rapidly building walls with shotcrete for underground coal mines according to claim 1, wherein the sand is medium sand or coarse sand, the fineness modulus is greater than 2.5, and the water content is 5-5 7%, and the mud content is less than or equal to 3%. 5. a method for rapidly building walls with shotcrete in a coal mine underground according to claim 1, characterized in that: the sprayer is a rotor type-II type shotcrete machine, and the spray gun is a double-water ring conical spray head ; The spray gun is equipped with double water rings, and micro holes with a diameter of 1 mm are drilled on the ring according to the spacing of 10 mm. 6 . The method for rapidly building walls with sprayed concrete for underground coal mines according to claim 1 , wherein the wind pressure during the spraying process of the sprayer is 0.12-0.17MPa, and the water pressure is 0.18-0.21 MPa. 7 . MPa.

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