A. Excavation of loose broken rock formations In the loose broken belt tunneling, the chiseling and loading work is not the key. The main process is the correct cooperation of support and excavation and support work. Different excavation support methods are selected according to geological rock conditions.
a Leading bolt method This method is applicable to rock hard, bedding, joint development, medium crushing, and bolting and shot support. The main points of operation of this method: The wrong pole hole top angle is 5~7° ; the length of the rod is equivalent to 1.5~1.8 times of the circulating footage ; the light burst is matched; the lead rod is used as a part of permanent support.
b Wedge method This method is applicable to dry loose rock layers, dry gravel layer, surrounding rock is not stable, no empty top is allowed after excavation, and water inrush is <10t/h. The main points of operation of this method: The wedge is generally used with d10~d12cm , 3~3.5m long round, and iron cap: the angle between the impact bar and the external opening angle is 15~20° ; the hammer can be hung on the frame beam The efficiency can be increased by 374 times; the working surface is 3m~4m , the shed distance is 0.7~0.8m, and the back part is densely shed.
c Rail feeding beam method This method is applicable to rock formations that fall more than 3m , the rock is hard, and there is a large block that cannot be hit by the wedge. Operation points of the implementation of this method: The beam is sent by 24kg/m rail and special U- card. The number of rails depends on the ground pressure, generally 2~3 . The two armpits were cleared after standing on their legs.
d Beam-protecting method This method is applicable to the vicinity of faults, staggered joints, crushed and crushed, easy to fall off, but the rock is hard, the wedge can not be hit, and the falling height is less than 1.5m . Operational points for the implementation of this Law: After the blasting, the cantilever joist top is supported first, and then the shed is shed; the wooden slab must not be suspended on the joist.
B. Support of loosely fractured rock layers In the severely weathered and fault-fractured zone, or the repeated intervening of the veins, the joints of soft sandstones with intertwined joints, the surrounding rocks are broken into small pieces and the cementation is poor, and the self-supporting of surrounding rocks cannot be utilized. ability. At this time, a simple wooden bracket is usually used for temporary support, and then reinforced concrete is used as a permanent support. Although the temporary wooden support is carried out as closely as possible, the self-stabilization ability of the surrounding rock after exposure is poor, and a falling area is formed on the wooden support.
For the support of such rock formations, it is best to cement the loosely broken rock layers that have already fallen by grouting, and then carry out the short-section concrete watering and steadily advance. In addition, some mines have adopted the shed support method. The construction points and steps of the law are as follows:
( 1 ) joist changing column, masonry foundation and rotating wall;
( 2 ) erecting a greenhouse on the magnetic wall;
( 3 ) treating the top gang with a wedge wedge letter;
( 4 ) When the top pressure is large, the column is added under the beam. After the concrete arch is solidified, the column is removed and the high-grade concrete is filled.
The advantages and disadvantages of this method are: Compared with the roofing support method, the operation is safer, and there is a dense buffer layer on the vault, which will not cause secondary impact on the spiral arch; the pit wood can not be recycled, and the cost is high. The construction process is complicated and the progress is slow.
Metal Alloy Powder
Metal alloy powders are commonly used in thermal spray processes to coat surfaces with a protective or functional layer. These powders are typically made by combining different metal elements in specific compositions to achieve desired properties such as corrosion resistance, wear resistance, or thermal conductivity.
Some commonly used metal alloy powders for thermal spray include:
1. Nickel-based alloys: These alloys are known for their excellent corrosion resistance and high-temperature strength. They are often used in applications where resistance to oxidation and wear is required, such as in gas turbine components.
2. Cobalt-based alloys: Cobalt alloys are known for their high hardness and wear resistance. They are commonly used in applications where resistance to abrasive wear and high temperatures is required, such as in the aerospace and power generation industries.
3. Stainless steel alloys: Stainless steel alloys are used for their corrosion resistance and high-temperature strength. They are often used in applications where protection against corrosion and oxidation is required, such as in chemical processing equipment.
4. Titanium-based alloys: Titanium alloys are lightweight and have excellent corrosion resistance. They are commonly used in applications where a combination of high strength, low density, and corrosion resistance is required, such as in the aerospace industry.
These metal alloy powders can be applied using various thermal spray techniques, such as flame spraying, arc spraying, plasma spraying, or high-velocity oxygen fuel (HVOF) spraying. The specific choice of alloy powder and thermal spray process depends on the desired coating properties and the application requirements.
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