In the underground mines, there are more and more square shafts with square or rectangular cross-sections, such as cable shafts, elevator shafts and ventilation shafts. The construction of mine square shafts still follows the way of tunneling [1-2]. For circular section wellbore construction, the perimeter of the wellbore section is smooth and continuous, which is beneficial to the selection and arrangement of construction equipment. The excavation, masonry, operation and other process systems can be coordinated and easy to achieve rapid construction [3-4]. However, the square shaft is affected by four right-angled well walls, the wellbore is difficult to form, and the work efficiency and capacity of blasting and wall-laying are limited. The traditional square well formwork construction method has the disadvantages of poor integrity, more labor, and longer construction period [5]. Safety production is the basic condition for ensuring the construction period. The construction of mine square wells is special. Therefore, it is very meaningful to discuss the rapid construction technology and safety management of mine square wells. The square shaft construction still adopts the construction method of vertical shaft short boring and short-mixing operation, which can be divided into three steps: construction preparation, wellbore preparation section and normal section construction of the wellbore. The process flow is shown in Figure 1. (1) Blasting. In order to improve the construction progress of the square shaft, in the construction of the square elevator shaft, measures such as appropriately increasing the depth of the blasthole and improving the efficiency of the grooving are adopted to increase the way of the footage of each tunneling to speed up the construction progress. Using YT-28 pneumatic drill for eye drilling, each eye is firstly drilled with 2m steel brazing, then deepened with 2.5m steel brazing sleeve, the drilling depth is 2.5m, and the drilling and dicing are used to drill the eye. Or drill the eye from the center to the well. The large parallel connection is used for blasting, and the charging wire is connected after the charging. The wire rope suspension cable in the wellbore is fired, and the LR-Z type explosive device wellhead is used to detonate the magnetic electric detonator blasting. In the ventilation, a high-power contra-rotating fan is equipped with a Φ600mm double-resistance rubber air duct for exhausting smoke. In the square shaft wellhead signal room, a centralized control system is set up. All the hanging trays and the ashing pipes, the wind pipes and the drain pipes are lifted and stabilized (including the pipeline suspension and stable vehicles). The start switch is set in the signal room, which can be set to be both linked and capable. The centralized control device lifts the hanging plate and the hanging plate is more than 20m away from the bottom working face. Practice has shown that the time for centralized control of the lifting and lowering tray is shortened by more than 1 h compared with the unsynchronized landing. Article source: Mining Technology; 2017.17(2) Author: HE Duanhua; new County of Hunan Province Administration of Work Safety, Hunan County 422700 Copyright: Scented Oil Diffuser,Essential Oil Diffuser,Best Essential Oil Diffuser,Aroma Oil Diffuser Guangzhou Chiyang Scent Technology Co., Ltd. , https://www.gzdiffuserscent.com
The second phase of the 4 million t/a waste rock lifting system of Yuxi Dahongshan Mining Co., Ltd. is located in the southwest of the ore body. The section of the 2# elevator shaft is square, which is the service channel for the waste rock to clean the waste rock at the bottom of the well. 22m horizontal and -79m horizontal working face construction workers and access to the upper and lower materials. The square elevator shaft has a height of about 244m, a net section of 4.9m×3.8m, and a support thickness of 300mm. It is supported by C30. The rock hardness coefficient f=8～10, and the water inflow is less than 5m3/h. The construction period of the square wellbore is May, the comprehensive average monthly footage is 49m, the masonry wall is smooth and smooth, and the rapid construction is realized under the condition of safe and high quality.
1 Square shaft rapid construction mechanized supporting mine square shaft shaft construction is carried out by short section mining and mixing operation method. The effect of construction mechanization supporting level on square shaft construction speed and quality is the same as that of many vertical shaft wells, that is, reasonable Mechanical equipment is an important guarantee for fast and high quality construction. # 2 Square Elevator Shaft construction machinery equipment selection Dahongshan iron ore draws on the experience of advanced equipment for shaft construction, and give full consideration to construction limitations square wellbore, wellbore construction machinery and equipment used in Table 1. 
2 Mine square shaft rapid construction plan
2.1 Construction preparation Before the square shaft construction enters the site, the “four links†such as traffic, water, electricity, communication, etc. are completed. The construction materials are discharged from the slopes and the waste rock bucket shafts to the working surface, and the wellbore meteorites are It is transported to the surface waste rock yard through the auxiliary ramp; the water supply is connected to the water from the second stage ramp; the power supply is taken from the power distribution room of the second stage; and the mine safety telephone is installed in the wellhead and underground. Before the construction of the square square elevator shaft, the upper part of the elevator shaft should be completed to arrange the sinking stable and the sky wheel platform.
2.2 Wellbore preparation section construction Before the square wellbore is being drilled, it is necessary to construct a certain depth of the wellbore preparation section to be installed with the hanging plate and the sealing plate. The height of the elevator shaft preparation section is not less than 23m.
The wellbore preparation section is constructed by HS-4 long-rope suspension rock grabbing rock, and the main lifting and stability truck is used to construct the material of the upper and lower personnel of the 3m3 bucket. In order to prevent the blasting from damaging the Tianlun platform, the iron plate is welded under the steel beam of the Tianlun platform, and the small gun or the blasting method is adopted to reduce the blasting impact. The rock drilling equipment is YT-28 pneumatic drill with an eye depth of 2 m. The wellhead is constructed by steel beam and wooden board. After grabbing the rock, the rock is lifted to the level of the chamber of the machine room. The grab is pulled to the machine room to remove the shovel, and then the loader is used to transport the raft to the car. Supported by wooden formwork, the support section is 3m high, and the ash pipe is suspended under the wall of the well wall, and the layer is symmetrically poured. 23m dig into the wellbore when the well head position, stop the driving, vehicle stability and steel mounting assembly can adjust the overall square metal template, and vehicle stability mounted hanging plate made double hanging plate assembly, and then put on the hanging plate, using the hanging plate The turning room and the turning chute are installed in the machine room, and finally, the hanging plate is dropped below the wellhead, the wellhead sealing plate is installed, and the hanging system is formed to form the digging condition.
2.3 Construction of the normal section of the wellbore The construction of the normal section of the square wellbore mainly includes drilling blasting, rock cleaning and bottoming, and supporting lining.
(2) Filling the rock to clear the bottom. The net diameter of the mine square shaft is usually small, and only one rock grab can be installed. In the square elevator shaft construction, the HS-4 long rope suspension rock grab is equipped with 0.4m3 grab rock. Limited by the net section of the wellbore, the lifting bucket can not be configured very large. The net section size of Dahongshan square elevator shaft is 4.9m×3.8m. After optimization, one 10t well winch (disc brake) is used to lift two 3m3. The bucket is out of the rock, the platform is flipped and the platform is turned and unloaded to the machine room. The work of clearing the bottom of the well is carried out by using the rock grabber and the manpower, and cooperates with each other to use multiple wind and clear bottoms to help clear the bottom and speed up the work of clearing the bottom.
(3) Support lining. The wall is made of adjustable square metal formwork with a mould height of 3m and a masonry section height of 3m. The concrete required for masonry is well-grounded, and the material is transported to the wellhead of the square well by the transport tanker. The pouring workbench is set up and the ash pipe is used for cutting. The concrete wall-casting method adopts a symmetrical layered annular watering method, and the layer thickness is 300mm, so as to prevent the one side of the steel mold from stacking and pressing the whole square mold to cause the running mode. Vibrate with a plug-in pneumatic vibrating rod and handle it on the hanging plate. The joint must be full and dense to ensure the quality of the joint.
3 key technologies for rapid construction of square shaft
3.1 Empty hole second-order barrel-shaped gutter smooth blasting Square shaft blasting footage is easy to be used for the production of four corners. The arrangement of the gutter is extremely important. According to many similar engineering experiences [2], the center of the gutter is left. The empty hole with no charge is set, and the diameter of the hole is equal to or larger than the diameter of the groove of the charge, which is used as the auxiliary free surface of the charge blasting and the compensation space of the crushed body. Therefore, the straight eye bucket is used in the arrangement of the blasthole. The shape-groove method, that is, the second-stage barrel-shaped groove smooth blasting with empty holes, effectively improves the blasting effect of the square wellbore. In order to reduce over-undercut, the peripheral eye distance is smaller than that of the conventional smooth blasthole, and the guide holes are arranged at the corners. The blasthole arrangement is shown in Figure 2. The blasting effect is shown in Table 2. In the square wellbore construction, the rock condition is adjusted in time, and the best blasting parameters are selected.
3.2 Adjustable integral square metal formwork In order to realize the rapid and high-quality construction of the mine square shaft wellbore, the traditional combined bulk wood formwork or steel formwork is integrated and innovative design, and the adjustable whole square metal formwork is developed for wall building. According to the actual size of the square shaft section, the adjustable integral square mold is customized. The whole square mold is mainly composed of 4 sets of right angle combined metal formwork, lapped T-shaped plate, overlapping channel steel, hydraulic cylinder, limit jack and limit bolt. ], 10mm thick steel plate is welded, the mold height is 3m, as shown in Figure 3. Yuxi Dahongshan Mining Co., Ltd. Phase II waste rock lifting system The square elevator shaft has a net size of 4.9m×3.8m, and the square mold has 4 stripping and shrinking ports. The adjustment range is (5000～4700)mm×(3900 ~3600)mm, square mode adjustment telescopic is mainly realized by hydraulic cylinder.
3.3 lifting and steady vehicle centralized control
3.4 Pipeline Wall Suspension Technology The air pressure pipe, the drain pipe, the water supply pipe and the rubber air cylinder are all suspended by the stable vehicle, which solves the problem that the traditional well wall suspension needs to occupy the tunneling time separately, and the pipeline is extended at the wellhead. Below the wellhead and above the hanging plate, 10~15m for the pressure air, water supply pipe and drain pipe are connected by hose. Reserve some hoses on the wellhead and the hanging plate to reduce the number of steel pipe extensions and greatly shorten the lifting time of the hanging plate. Thereby saving the construction time of the square wellbore.
4 Rapid construction safety management of mine square wells (1) Safety management institutions and systems. In order to effectively control the safe production process, a safety management department with safety deputy manager and full-time safety officer was established. The construction team also added a group security officer. The full-time security officer and the group security officer under the command of the safety deputy manager. Carry out various construction safety management tasks, and have regular and irregular safety inspections every month, resolutely stop the "three violations" and improve the safety production responsibility system.
(2) Equipment safety operation management. All mechanical and electrical equipment is chartered to the person. The full-time personnel must inspect the equipment and equipment of each process every day, and the listing management; the mechanical and electrical department of the project department regularly checks the operation of the lifting device and the lifting winch. All electrical equipment is equipped with overcurrent protection, leakage protection and protective grounding. The device; the square template shall be regularly inspected and proofread. It shall be stable and firm, the splicing shall be tight, no looseness, and the bolts shall be securely fastened to prevent displacement during construction. If the size of the specification is changed, it shall be adjusted in time.
(3) Roof safety management. Persist in knocking on the top system. According to the characteristics of the shaft construction, when the personnel arrive at the working surface by the bucket, first check whether the wellbore wall has loose pumice stone , find the loose pumice in time, and choose the station where there is no loose or pumice in the process. Strictly implement the safety confirmation procedure for top grade management. Each time the inspection forms a ledger, it is safe to carry out work such as the connection of the working surface air duct.
(4) Blasting safety management. The shooting must be carried out by full-time gunners. After special training, they will be certified. Execute the blasting item retreat system. When using detonator explosives at the construction site, strictly enforce the regulations for receiving the shift on duty. When loading the wellbore, except for the gunners and signal workers, other personnel must be evacuated to the wellbore; Before, the electrical facilities on the working surface are lifted away from the charging point by about 20m; after blasting, the air is blown for 30min, the gunpowder is blown away, and the layers are cleaned in time. Then the gunners and safety officers are put into the working surface to check the blasting situation. Other personnel enter the well to slag.
(5) Personal safety prevention. The operator must first check and familiarize with the pipelines and safety conditions at the workplace, and then adopt safe methods according to local conditions. Workers must wear safety belts, wear safety helmets, and put on work shoes. Slippers or rubber-soled shoes are strictly prohibited. When using the bucket to get up and down the wellbore, it is strictly forbidden to play in the underground, and the belt must be buckled to obey the wellhead signal arrangement. It is strictly forbidden to drink alcohol and go down.
5 Conclusion Compared with other circular shaft projects, the mine square shaft project is relatively complicated and difficult to construct. Therefore, according to the characteristics of the square shaft operation, the improved construction facilities and equipment are selected and properly matched. The adjustable square metal formwork, the second-order barrel-shaped groove smooth blasting, the centralized control of lifting and stable vehicles, and the well are adopted. Wall suspension and other technical innovations have solved the problems of wall-building, blasting and lifting of square shaft engineering. At the same time, relying on scientific organization management and strict safety measures, the rapid construction under the safe and high-quality conditions of mine square shafts has been realized.
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Wang Zuhui; Lianshao Construction Engineering (Group) Co., Ltd., Loudi City 417 000