Four methods for reliability verification of ultra-high molecular escape pipelines
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The ultra-high molecular polyethylene tunnel escape pipeline material is light in weight, easy to assemble and disassemble; the pipeline has good toughness and high impact strength, and the pipeline ring has high rigidity, good pressure resistance, and is not easily deformed, and can be repeatedly used repeatedly. The transportation department demonstrated the emergency rescue channel of the ultra-high molecular polyethylene tunneling escape pipeline in the tunnel construction. The pipe structure size is ergonomic. Through the impact test of ultra-high molecular weight polyethylene escape pipes and steel pipes, the reliability of UHMW escape pipes used in tunnel construction emergency rescue is verified.
Verify the reliability of UHMWPE pipes by the following four basic methods
1.800 escape pipe (new material) structural size design
Alvin R. Tilly pointed out that the minimum diameter of the round tube is 585 mm when the entrance and exit of the circular opening at the bottom of the whole body is crawling through. Therefore, the inner diameter of the new emergency rescue channel for highway tunnel construction must be ≥ 585mm to ensure the normal passage of the human body.
At the same time, considering the actual situation of the road tunnel construction site, the outer diameter of the emergency rescue channel should not be too large, otherwise the impact on the construction is large, so the outer diameter of the ultra high molecular weight polyethylene pipe is 800mm in diameter.
2. New 800 escape pipe thin and thick diameter design
During the lateral impact of the thin-walled circular tube on the side of the large energy block at the top of the tunnel, the overall bending deformation of the lower half of the structure is small, and the deformation is mainly caused by the local depression of the impact point.
According to the Hertxz contact mechanics theory, using the Thornton hypothesis, the material has the ideal elastoplasticity, then the contact pressure between the two contact objects. On the basis of the energy analysis, the local depression value â–³ and the lateral load P when the circular tube is subjected to the lateral impact The relationship between the two can be derived from the local depression value of the round tube when it is subjected to lateral impact, which is the yield stress of the round tube material; H is the thickness of the round tube; D is the diameter of the round tube.
800 escape pipeline (molecular weight is about 2.5 million), the specification is Φ ultra high molecular weight polyethylene * 30mm, the main parameters are: yield strength σ1 = 3.7GPa, elastic modulus: E1 = 700MPa; Poisson's ratio ν1 = 0.42; Density: Ï1 = 950kg/m3.
The impact test piece is block granite. The diameter of the rock mass is 0.67m. The rock mass parameters are: elastic modulus E2=40GPa, Poisson's ratio ν2=0.2, density Ï2=2500kg/m3. The weight of the rock block is W=400kg.
The limit value H of the height from the center of the tunnel and the top of the tunnel to the top of the round pipe is 7m and 5m. The rock is freely released and impacts on the 800 escape pipe and the steel pipe respectively. At this time, the rock mass falling speed can be calculated according to the law of conservation of energy. , v1 = 11.7 m / s and v1 = 9.9 m / s, respectively. The wall thickness H of different round tubes is calculated. As the wall thickness of the round tube increases, the deformation value of the round tube depression caused by the falling of the stone is getting smaller and smaller. When the drop height h=7m and the wall thickness H=24mm, the concave deformation value of the 800 escape pipe is Δ=0.048m, which is about 8% of the diameter of the pipe; when the drop height h=5m, the wall thickness H= At 24 mm, the deformation value of the depression is Δ=0.038 m, and the deformation value is smaller. At this time, after the 800 escape pipe is deformed and recessed, the passage space inside the pipe is 740 mm, which meets the ergonomic requirements, and the person can safely pass the emergency passage. When the wall thickness is small, the deformation value increases, which may be unsafe. When the wall thickness is larger, although the safety is increased, the weight of the pipe is also increased, resulting in an increase in cost and difficulty in handling. Therefore, it is suitable to take 800 escape pipe wall thickness of 30mm in the design.
3.800 escape pipe connection parts design
The main part of the 800 escape pipeline is made of ultra-high molecular weight polyethylene pipe, and a reinforcing layer is arranged at the end. The connecting parts are steel wire rope, iron chain and end hook. In order to collide in the tunnel, the relevant personnel can easily climb in the 800 escape pipeline, and tie a climbing rope every 120° in the channel circumference.
In the principle of convenient disassembly and assembly, the connection between the escape route of the road 800 and the pipe is a hoop connection. Therefore, it is more convenient in the installation and construction organization. When installing for the first time, it is only necessary to dock the two pipes and fasten them tightly with the hoops. According to the existing holes of the hoop, drill holes on the pipe to wear the bolts. . Wherein, the end of the wire rope and the end of the chain are hooked, and the length of the chain can be freely adjusted according to the position of the hook on the chain of the chain.
4.800 escape pipeline reliability verification
Test purposes
Through the impact test of 800 escape pipes and steel pipes with similar size specifications, the feasibility of using super high pipes for emergency rescue of road tunnel collapse rescue is demonstrated.
experiment material
1. Q235 spiral seam submerged arc welded steel pipe with the specification of Φ620×10. The yield strength σ1 = 215 GPa, the elastic modulus elastic modulus E1 = 210 MPa, and the Poisson's ratio ν1 = 0.25.
2, 800 escape pipeline (molecular weight is about 2.5 million), the specification is Φ ultra high molecular weight polyethylene × 30mm, yield strength σ1 = 3.7GPa, elastic modulus E1 = 700MPa; Poisson's ratio ν1 = 0.42.
Inspection requirements and methods
The steel pipe and the 800 escape pipe are freely released from the height H of the top of the pipe at a height H of 10 m from the top of the pipe, and the impact comparison test is performed to verify the reliability of the 800 escape pipe.
1. The impact test piece is a block granite, and the diameter of the rock block is initially selected to be 0.67m. The rock mass parameters are: elastic modulus E=40 MPa; Poisson's ratio: ν1=0.2; % density Ï1=2500 kg/m3; rock mass W=400 kg.
2. The round tube cushion is a flat sand bag with a cushion thickness of 250 mm and a width of ultra high molecular weight polyethylene mm.
The thin-walled tube used for tunnel construction and rescue is freely placed on the flat cushion. When subjected to the impact of rockfall impact, the bottom of the round tube is mainly restrained by the vertical and lateral friction of the cushion. The distance from the top of the impact test piece to the top of the round pipe depends mainly on the excavation height of the tunnel section. The limit value H of the height from the top of the tunnel center to the top of the pipe is 10m, and the block stone is freely released, respectively, for 800 escape pipes and steel pipes. Carry out the impact. Experimental results 800 After the escape pipeline was impacted, the stone was ejected, the pipeline was hardly damaged, and the impact resistance was good. After the steel tube was impacted, the pipeline was flattened and deformed.
In order to clarify the magnitude of the impact energy, the impact force and the circular tube shape of the free fall of the stone from a height of 10 m are calculated. When the stone falls freely, the instantaneous velocity of the stone can be obtained by the law of conservation of energy, Vt=14m/s. At the same time, it can be calculated that the impact force and deformation of the 800 escape pipes and steel pipes are as shown.
It can be seen from the results that the impact energy of the stones falling at a height of 10 m is very large. At the same time, the 800 escape pipeline has extremely high impact resistance, and the external impact cannot cause it to rupture. Moreover, it has good toughness and impact energy absorption performance. During the impact of large stones, it can absorb most of the impact energy and reduce the damage to the pipeline. The impact resistance of the steel pipe is not as good as that of the 800 escape pipe, and it is deformed after being hit by the stone and is difficult to recover.
Certification conclusion:
Because the 800 escape pipeline (Ultra High Molecular Weight Polyethylene) is light in weight disassembly and handling, it has good toughness and high impact strength. It is instantly deformed by strong external force, absorbs a large amount of impact energy, and then quickly restores its original shape as a road tunnel. The construction rescue rescue provides extremely safe and reliable protection; the pipeline ring has high rigidity, good pressure resistance and is not easy to be deformed. When collapse occurs in highway tunnel construction, the pressure bearing capacity and environmental damage resistance far exceed the general pipeline, including steel pipe. Then let us look at his superiority and scope of application.
Tunnel 800 escape pipe excellence
800 escape pipeline has excellent comprehensive performance, and has unparalleled impact resistance, pressure resistance, wear resistance, anti-aging, light weight, chemical corrosion resistance, hygienic non-toxicity and non-adhesion in other engineering plastics. Foreign countries are known as "magic plastics." Therefore, it has extensive reference prospects in the fields of machinery, transportation, textile, paper, mining, agriculture, and chemical industry.
â— Light weight, only about 1/3 of the weight of the steel pipe, easy to disassemble and transport.
â—The pipeline has good toughness and high impact strength. It is instantly deformed by strong external force, absorbs a large amount of impact energy, and then quickly restores its original shape, which provides an extremely safe and reliable guarantee for emergency rescue of highway tunnel construction.
â—The pipe ring has high rigidity, good pressure resistance and is not easy to be deformed. When collapse occurs in highway tunnel construction, the pressure bearing capacity and environmental damage resistance far exceed the general pipeline.
800 escape pipeline application:
The pipe used for the 1800 escape pipeline adopts ultra-high molecular weight polyethylene pipe with diameter of 800mm. The length of the pipe joint is 12m and the wall thickness is 30mm. The pipe joint can be connected with metal hole with hoop diameter larger than (Dalian) 800 escape pipe diameter, 22mm. Wide, temporarily fixed with bolts. In order to ensure that the pipeline is subjected to the pressure of the collapsed body, the material pipe used must ensure its pressure bearing capacity and the connection head is firm, and can be used in the tunnel after specific tests in the laboratory.
2 The construction site should prepare the pipeline and connecting materials according to the tunnel surrounding rock, excavation and excavation methods, etc. In addition to the whole section of the pipeline, the 1 m, 2 m, and 3 m short section pipes and adapters should be prepared at the same time.
The 3800 escape pipeline is processed and used, combined with the material and the actual situation on the site. The connection is simple, firm, compact and reliable. The temporary fixing measures are made on the ground. The nozzle can be temporarily sealed and easy to open and close during construction.
The 4800 escape pipeline adopts a socketed ultra-high molecular weight polyethylene pipe with a diameter of 800mm, and the starting point is the newly applied second liner end, and the distance from the second liner end is not more than 5 meters, from the lining working surface to the distance. Appropriate position within 20m of the excavation face, (Dalian) 800 escape pipeline is laid along the side of the initial support to the face of the hand, and the working rope is reserved in the pipe to facilitate lifesaving, rescue, contact and transmission of various items. The longitudinal connection of the molecular weight polyethylene pipe can adopt measures such as chain to prevent the ultrahigh molecular weight polyethylene pipe from being washed away when collapsed.
The 5800 escape pipeline shall be dismantled section by section during the temporary disassembly of the second lining trolley. It is strictly forbidden to dismantle it once in order to ensure the effectiveness of the 800 escape pipeline at any time.
When the 6800 escape pipe passes through the excavation step, it should be arranged according to the step, and the 135° adapter joint should be installed. The height and length of the pipe should not affect the construction and facilitate the opening of the life-saving window.
7 The 800 escape pipelines shall be flat, dry and smooth, and shall not be used for emergency rescue.
The 8800 escape pipe is laid at a length of 100m.
800 escape pipeline case:
At present, the Dali-Lijiang Expressway under construction has taken the lead in the use of 800 escape pipelines (ultra-high molecular weight polyethylene pipelines), which has added safety protection measures to tunnel builders. Please listen to the report of Yunnan Taiwan reporter Zhang Ting and correspondent Zhou Fengrong:
In Yunnan, the highway has a high proportion of bridges and tunnels, and the geological and geographical conditions are complex. Tunnel construction is the top priority of safe production. However, compared with the previous construction, the tunnel builders on the Dali Expressway have added a layer of safety protection. The master Zhao of the worker told the reporter: 800 escape pipeline, this is a good way, if the landslide, buried, people can follow this pipe.
The 800 escape pipe is made of special engineering plastics. The inner diameter of the inner hole is ultra-high molecular weight polyethylene mm. It can withstand more than 2000 kilograms of pressure and is enough for an adult to crawl from it. The 800 escape pipe is placed in the position connecting the face to the secondary lining. As the tunnel is drilled, the 800 escape pipe is constantly moving forward. Once the construction collapses, workers can safely leave the 800 escape route. The use of this technology can reduce the casualties of tunnel construction workers. Sun Qiaobao, Chairman of Provincial Highway Development and Investment Co., Ltd.: It is generally easy to go between the tunneling and the second floor. We asked for a 60-meter-long pipeline when we tendered. Once it collapsed from the face, it was buried and the staff passed. The pipe can come out.
In the end, I sincerely hope that every tunnel project can be carried out safely and make our country more prosperous. In addition, we would like to know friends from all walks of life. We warmly welcome friends from all walks of life to visit our company and guide.