The Most Complete Pipe Umbrella System Construction Procedure

Time:2022-07-11From:sinorock View:

In most unstable tunnel constructions, the advanced large pipe umbrella system support is the best solution to support the fractured or weathered rock mass. The general method of entering the hole is: first excavate the arch part of the open hole section, and carry out the side and slope support treatment according to the design, then apply the C20 concrete sleeve arch, then apply the advanced pipe umbrella system, and finally enter the tunnel to start other works.

Skills Requirement

The earthwork excavation at the entrance must be avoided during the rainy season. Before excavation, drainage systems such as intercepting ditch and gutter shall be constructed, and then the opening shall be excavated. The excavation of the cut-and-cover section shall be carried out layer by layer from top to bottom, and side and slope protection shall be carried out with shotcrete along with the excavation. When reaching the height of the excavation contour line of the vault in the undercut section, dig down vertically to the bottom of the set upper half section, and temporarily spray concrete to close the tunnel face of the dark hole. Circumferentially cut along the excavation contour line, install a 2-section steel frame, pour concrete, and prepare for the excavation of the dark hole.

The Technological Process of Pipe Umbrella Support System

Large Diameter Pipe Umbrella

1. In order to ensure the quality of the hole forming and prevent the collapse of the previous hole forming when the adjacent hole is drilled, the drilling should be carried out at intervals. The odd-numbered holes are drilled first, and the even-numbered holes are drilled later. The diameter of the holes is 140mm so that the φ108×6mm steel flower tube can be installed smoothly. That is to say, large pilot holes are used for construction, to the greatest extent possible to overcome the difficulty of pipe feeding in the pipe jacking construction operation.

2. When using long pipe sheds (φ108×6mm), the drilling angle is 1°～3°, the circumferential spacing is 40cm, and each length is 40m (each section is 9m long and connected by an 89cm long casing), When applying, each section should be staggered and overlapped by 3m, and small holes of 10mm should be drilled on the steel pipe according to the spacing of 15cm in plum blossom. The top of the first section of the steel pipe is tapered to facilitate jacking. φ108×6mm steel pipe adopts two specifications of 4.0m and 6.0m, the first one of odd-numbered holes is 4.0m, the first one of even-numbered holes is 6.0m, and the rest are 6.0m, so as to avoid the steel pipe joints on the same section. The steel pipe is connected by the casing.

3. In order to ensure that the drill pipe joint has sufficient strength, rigidity, and toughness, the drill pipe coupler should be of the same material as the drill pipe, with internal threads at both ends (with the outer screw at the first end of the drill pipe), and the wall thickness of the coupler ≥ 10mm. In order to prevent the drill pipe from vibrating up and down under the dual action of thrust and vibration force, resulting in non-straight drilling, when drilling, the straightener should be sleeved on the drill pipe, and the drill pipe should move forward as it moves forward.

4. The direction of the vertical axis of the drilling rig must be accurately controlled, and the hole position and hole number are marked on the poured sleeve arch. The holes are divided into odd holes and even holes. The odd holes use seamless steel pipes, and the even holes use plum blossom steel pipes. After the odd-numbered holes are formed, install steel flower pipes or non-porous steel pipes in time, and inject cement slurry. After the even-numbered holes are formed, the steel pipe must be installed immediately to prevent the holes from collapsing. At the same time, the construction of the even-numbered holes can check the grouting quality of the odd-numbered holes on the one hand, and on the other hand, supplementary grouting can be carried out to improve the effect of grouting to strengthen the surrounding rock.

5. When drilling, the boom of the trolley must be tightly pressed against the face to prevent excessive vibration from affecting the drilling accuracy.

6. The drilling speed of the drilling rig should be low when opening the hole, and then switch to the normal drilling speed after drilling 20cm.

7. The first section of the drill pipe is drilled into the rock formation, and the drilling is stopped when the remaining 20-30cm is left at the tail, and the drill pipe is manually clamped with two pipe wrenches, and the drilling rig is reversed at a low speed to disengage the drill pipe. The drilling rig is reset along the guide rail, and then the second drill pipe is loaded.

8. The diameter of the guide hole is 15-20mm larger than the outer diameter of the pipe umbrella, and the hole depth is more than 0.5 meters longer than the length of the pipe.

Construction of Long Roof Pipe

1. Pipe jacking process: According to the requirements of rapid construction, it is decided to use a combination of large guide hole and shed pipe drilling, and first drill a guide hole larger than the outer diameter of the steel pipe, and then use the impact and thrust of the drilling rig (jacking pipe During the shed, the rock drill does not use rotary pressure and does not generate torque). The shed pipe with the working pipe head is pushed in along the guide hole, and the pipe shed is connected section by section until the bottom of the hole.

2. Production of pipe fittings: The pipe shed is made of Φ108 seamless steel pipe, the steel pipe is made of 3m and 6m sections and the length is connected section by section. The steel pipe joints should be longitudinally staggered, 3m for the first even-numbered section, 6m for the odd-numbered first section, and 6m for each subsequent section. The buried length of the pipe shed is 24m. When the pipe shed is lengthened, the previous steel pipe shall be pushed into the drilled guide hole before connecting. The front section of the first steel pipe shall be welded with an alloy steel sheet-type hollow drill bit to prevent the end from being bent or split.

3. After the hole is cleared and the drilling is qualified, the steel pipe should be installed. After each hole is drilled, a steel pipe should be jacked in. During the drilling, a measuring instrument should be used to measure the deflection of the steel pipe, and it is found that the deflection exceeds the design requirements. Correct in time. The long pipe fittings should meet the stress requirements of the pipe shed, and the joints of adjacent pipes should be staggered forward and backward to avoid the joints being stressed in the same section.

4. Pipe jacking operation: After the steel pipe is placed on the boom of the trolley, the rock drill is aligned with the drilled guide hole, and the steel pipe is pushed at a low speed.

5. Takeover: when the first steel pipe is pushed into the hole and there is 30-40cm left outside the hole, start the rock drill to reverse, so that the jacking coupling sleeve is detached from the steel pipe, and the rock drill returns to its original position, the boom falls, and the second pipe is manually installed. Section the steel pipe, the boom is re-aligned, the rock drill moves forward slowly, slowly, and at low speed to align the end of the first steel pipe (the angle is strictly controlled), and the steel pipe is connected by manual chain pliers, so that the two steel pipes are integrated at the connection sleeve. The rock drill then jacks into the steel pipe at low speed with impact pressure and thrust pressure. According to the design length of the pipe shed, continue to connect the steel pipe in the same way.

6. To close the end of the steel pipe, first, use the burlap to seal the hole in the pipe shed, then use the annular wedge ring to tighten it, and finally weld the wedge ring to the pipe shed with electric welding.

7. Pipe shed pipe reinforcement: In order to strengthen the rigidity and strength of the pipe shed, after all the pipe shed steel pipes are laid according to the design, first use a drill to dig out the residue in the steel pipe to reinforce the shed pipe.

pipe umbrella support system

Preparation of Slurry

1. The mixing of the cement slurry should be carried out in a high-speed mixer, the materials should be fed in strict accordance with the construction mix ratio, and the cement water glass slurry should be injected into the steel pipe: 1, water glass modulus m=2.4, concentration Be=35, the initial pressure during grouting is 0.5～1MPa, the final pressure is 2.0Mpa, and the seamless steel pipe is filled with 1:1 cement mortar after grouting to enhance the strength and stiffness.

2. Feeding sequence of stirring cement slurry: while releasing water, add retarder and admixture in water in a certain proportion, stir to dissolve, then pour in the required cement and stir for 2-3 minutes.

3. The weight of the external admixture is 5%-10% of the weight of the cement, and the amount of the retarder is 2%-3% of the weight of the cement.

4. When preparing cement slurry or diluting water glass, it is strictly forbidden for cement blocks or paper sheets to enter the slurry.

5. Do a good job of construction records for the configuration of the grout, and make a grouting record during the grouting process to provide a basis for analyzing the grouting effect.

6. The prepared slurry is stored in the slurry storage tank with a low-speed agitator to prevent the slurry from precipitation and segregation due to a slightly longer storage time.

Grouting

1. After installing the perforated steel flower tube and putting it into the steel cage, grouting the hole, and the slurry is mixed by the ZJ-400 high-speed pulping machine.

2. Grouting material: The grouting material is an M20 cement slurry.

3. Use a grouting machine to inject the mortar into the steel flower tube of the tube shed, the initial pressure is 0.5~1.0MPa, the final pressure is 2MPPa, and the grouting is stopped after the pressure is maintained for 15min. The grouting should meet the design requirements, generally 1.5 times that of the borehole cylinder; if the grouting amount exceeds the limit and fails to meet the design requirements, the concentration of the grouting should be adjusted to continue grouting to ensure that the surrounding rock mass and the steel pipe around the borehole are fully filled.

In principle, the grouting sequence of the pipe shed follows the principles of "both sides first, then the middle", "jump-hole grouting", and "from thin to thick". The grouting construction starts from the pipe shed steel pipes at both ends, and the grouting construction is carried out by jumping holes, and advancing in the direction of the tunnel vault steel pipe. In the beginning, the slurry concentration of grouting is lower and gradually thickens to the design concentration. This approach is conducive to the spread of the grouting slurry to the dome direction and promotes the density of the slurry, which is conducive to the requirements of anti-seepage.

After the pipe shed with an even number of holes is completed, grouting is carried out on this part of the pipe shed. The grouting of the long tube shed is designed to consolidate the soil and rock within a limited range around the tube shed, the slurry diffusion radius is not less than 0.5m, and the grouting adopts segment grouting.

The above are two different methods to support the unstable rock mass in tunnel construction and we can see the whole construction is very and very and very complex. So is there a way to support more accessible? Of course yes. It is the Self-Drilling Rock Bolt.

Self-Drilling Rock Bolt

Then, what is self-drilling rock bolt?

The self-drilling anchor bolt system is composed of a hollow anchor bar, coupler, nut, drill bit, plate, and centralizer. It can combine drilling, grouting, and anchoring in one process. The self-drilling anchor bolt system is safe, efficient, and convenient. It is suitable for broken rock, loose soil, and geological conditions where is difficult to drill holes. It helps to ensure the anchoring effect in complex ground conditions and achieve the best construction result.

Construction Process

Sinorock is an experienced manufacturer of anchoring products with over 10 years of production experience. It is specialized in the development, production, and sales of anchoring products. Through several years’ efforts, Sinorock products have been exported to more than 40 countries. The company has passed ISO 9001 and SGS certification, and all series of self-drilling rock bolt has passed CE certification. Owing to reliable products and excellent services, Sinorock has won a great reputation all over the world.

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