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Method for Penetrating Walls with Fully Automatic Wet-Spraying Trolley Pipelines
Release time:
2026-09-15
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Summary:
In tunneling and underground engineering, the concrete delivery pipeline of a fully automated wet‑spraying carriage often needs to pass through structural barriers such as partition walls, side walls, linings, and diaphragm walls. The wall‑penetration section is a critical stress‑concentration point in the pipeline system; inadequate treatment can not only accelerate pipe‑wall wear and cause joint loosening and grout leakage, but may also lead to pipe rupture under concrete pumping pressure, posing a serious threat to operational safety. Establishing a standardized wall‑penetration procedure—covering the preparation of reserved openings, installation of sleeves, pipeline crossing, and sealing and fixation—is an essential requirement for ensuring the safe and continuous execution of wet‑spraying operations.
I. Core Rules for Through-Wall Treatment
When concrete delivery pipelines pass through walls or floor slabs, no branch connections shall be installed at the mid‑span of the wall; in other words, pipeline joints must not be located within the wall‑penetration section enclosed by the pre‑drilled opening. Instead, joints should be positioned on the exterior side of the wall or floor slab, ensuring they are situated in a readily accessible, visible, and operable zone for maintenance personnel. Additionally, sleeves must be provided, with sealing measures implemented between the pipeline and the sleeve; where waterproof sealing is required, waterproof flanged sleeves shall be used for jointing. For wall penetrations where settlement or misalignment may occur, expansion joints should be embedded in advance or flexible waterproof sleeves employed to prevent wall deformation from causing compressive damage to the pipeline. The foregoing provisions apply to wet‑spraying boom pipelines in all types of wall penetrations, including tunnel partition walls, shaft wall panels, and basement enclosure structures.
When passing pipelines through walls with a wet‑spraying carriage, the pipeline’s axial inclination should be minimized; it should traverse the wall horizontally or with only a gentle slope, and the inclination angle should not exceed 5° to prevent concrete segregation caused by abrupt changes in flow velocity within the pipe. If the wall thickness at the penetration point is insufficient, local thickening or the addition of a load‑bearing frame is required to accommodate the transmission of horizontal thrust and vibrational loads from the pipeline.
II. Preparations Before Work and Tool Inspection
Before performing wall‑penetration operations, operators must conduct a thorough inspection of the pipeline, casing, and sealing materials. Pipeline joints shall be securely fastened with clamps, and the sealing rings must be in good condition. The piping layout should minimize bends, with bend angles no less than 90°, to avoid sharp right-angle turns that can cause blockages. Casing should be steel pipe matched to the outer diameter of the conveying pipe; its inner diameter should ideally exceed the pipe’s outer diameter by 15–20 mm, providing an adequate expansion‑and‑contraction clearance and accommodating vibration. Sealing materials should preferably be pressure‑ and wear‑resistant rubber seals or polyurethane foam sealants; under high‑pressure pumping conditions, metal or nylon stop blocks should be used in conjunction with the seals.
The measuring tools shall include a spirit level, a tape measure, and an angle gauge to verify the deviation of the centerline of wall-penetrating openings and the horizontal alignment of pipelines. The allowable deviation in horizontal alignment shall be limited to 2 mm per meter to prevent localized stress concentrations caused by pipe misalignment.
III. Hole-Position Provisioning and Through-Wall Installation Procedure
Prior to the placement of tunnel lining or structural walls, openings shall be accurately pre‑reserved in accordance with the pipeline’s design alignment. The cross‑sectional area of these openings shall not be less than 1.5 times the pipe’s outer diameter, and reinforcing ribs or embedded steel plates shall be provided at the four corners of each opening to facilitate the subsequent installation of adjustable supports. When securing the wet‑spraying rig’s main unit, the levelness error of the working surface shall not exceed 2 mm per meter.
Installation and securing of the sleeve. Place the fabricated sleeve precisely in the designated opening, ensuring that its axis aligns with the pipeline’s designed routing. Use a level and a plumb bob to verify the sleeve’s position and verticality; deviations must not exceed 2 mm. Then, tack-weld the sleeve to the structural reinforcement and securely fasten the waterstop flange to the wall reinforcement mesh.
Pipeline crossing alignment. After the wall concrete has attained its design strength, the corrosion‑protected conveyance pipeline shall be slowly pushed into the casing. The joints of the wet‑spray machine’s delivery pipe must be securely fastened with clamps and fitted with intact sealing rings to ensure a tight seal. Once the pipeline has passed through the wall, pipe clamps or supports shall be installed at both the upstream and downstream ends of the casing for preliminary positioning, preventing the pipeline from sagging under its own weight.
Wall‑penetration section fixation and anti‑displacement measures. At the point where the pipeline penetrates a wall, a robust limiting device shall be installed to confine displacement in the vertical, horizontal, and lateral directions within the permissible limits. In cases where a vertical delivery pipe passes through a floor slab, wooden plugs or steel wedge blocks may be used to tightly pack the gap between the sleeve and the pipe, applying uniform compressive force from all four sides to ensure secure positioning. The material used to fill the pipe‑sleeve gap should be compacted in layers, with sealing rings or soft rubber gaskets employed circumferentially, so that the pipe remains centered under pumping‑induced impacts and to prevent direct contact between the pipe and the inner wall of the sleeve, thereby minimizing wear and impact.
Load calculation and reinforcement for wall‑penetrating sections. During pumping, concrete delivery pipes generate substantial vibrations that impose impact loads on walls or floor slabs, potentially damaging the piping itself. Support brackets shall be determined by structural analysis, and the supporting structure at their installation locations must be verified; reinforcement measures should be implemented where necessary. For long pipe runs passing through thick walls, additional vibration‑isolating supports shall be installed within sleeves, with support spacing not exceeding 1 m.
IV. Special Treatment for Waterproof Sealing and Flexible Connections
In tunnel sections with abundant groundwater or in areas where the groundwater level is high, wall‑penetrating pipelines must be equipped with stringent waterproofing and sealing measures. For high‑pressure transmission pipelines subject to significant vibration, flexible waterproof sleeves should be used. In addition to an external waterstop flange ring, these flexible sleeves incorporate an internal sealing ring and a flange pressure plate; tightening the flange bolts compresses the rubber sealing ring, ensuring it tightly grips the outer surface of the pipeline and providing a conforming, dynamic seal.
When passing through walls that may experience settlement or displacement, flexible waterproof sleeves shall be used, and expansion joints shall be installed between the pipeline and the wall. This allows the pipeline to accommodate small relative movements with respect to the wall without being crushed or fractured during wall settlement or temperature changes. Such measures are particularly critical when tunnels traverse fault‑fractured zones or sections with weak surrounding rock.
V. Inspection and Maintenance After Wall Penetration
Upon completion of wall‑penetration installation, the piping system shall undergo thorough inspection and maintenance:
Sealing inspection: Verify that the waterstop collar between the casing and the structural wall is securely installed and that the waterproof seal is properly in place. Apply low‑pressure compressed air or low‑pressure water to test the pipeline’s tightness, ensuring there are no leakage points. No grout leakage shall be permitted at the pipe‑connection clamps.
Differential pressure and vibration monitoring. During pumping, monitor differential pressure and vibration in the pipeline passing through the wall. If concrete pumping pressure rises abnormally or the pipeline exhibits unusual vibrations, immediately stop the machine and inspect the wall‑penetration section for blockages or crushing. Regularly use an infrared thermometer to measure temperature changes at the wall‑penetration sleeve, assessing whether excessive friction is generating heat in the pipeline.
Wall‑thickness wear inspection. Quarterly, use an ultrasonic thickness gauge to measure the wall thickness of the pipe sections that pass through the wall, and compare these measurements with those of reference pipe segments located outside the wall to assess the rate of external wall abrasion caused by the wall. If the wall thickness has thinned by more than 25% of its original value, the affected pipe section should be replaced promptly.
Conveyor pump pipes and their supports shall be regularly inspected and maintained, and any pipes, clamps, sealing rings, or other components whose wear exceeds the specified limits shall be replaced promptly. The pipeline shall be clearly marked with its working pressure, wall thickness, and the date of the last replacement, thereby establishing a complete pipeline usage record.
VI. Checklist for Wall Penetration Treatment
During pre- and post‑wall‑penetration inspections, you may refer to the following checklist to verify each item:
- Do the dimensions of the pre‑drilled openings in the wall meet the minimum clearance requirement of the pipe’s outer diameter plus 150 mm?
- Do the material and specifications of the wall‑penetrating sleeve match those of the pipeline, and is the connection between the waterstop flange ring and the structural reinforcement reliable?
- When the pipe passes through the wall, has it been ensured that the joint does not fall at the midpoint of the wall within the designated opening?
- Has the gap between the pipe and the sleeve been uniformly filled with sealing material, and has a flexible seal been installed?
- Have supports or limit devices been installed on both sides of the wall‑penetrating section as required, and is the levelness error ≤ 2 mm/m?
- During the vibration test, does the joint between the wall and the pipeline exhibit no abnormal displacement, no leakage, and no unusual noises?
- Has a ledger been established for wall-thickness wear of through-wall pipelines, and are inspections conducted on schedule?
By rigorously implementing precise positioning of reserved openings, employing a composite treatment that combines rigid sleeves with flexible seals, providing effective support on both sides of the wall, and establishing a dedicated inspection and maintenance regime for wall‑penetrating sections, the pipelines of the fully automated wet‑spraying carriage can maintain stable conveying performance as they pass through structural walls. This effectively reduces the likelihood of failures caused by pipe compression or vibration‑induced fatigue, thereby ensuring the continuity and safety of spraying operations.
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