The installation of highway noise barriers is divided into eight main modules: pre-construction preparation, foundation installation, column installation, panel assembly, sealing and noise reduction, corrosion protection and durability, traffic safety, and acceptance, operation, and maintenance. These modules cover both roadbed and bridge construction scenarios.
What factors should be considered when installing highway noise barriers? In the construction and operation of expressways, installing noise barriers is a key measure to reduce traffic noise and minimize disruption to the daily lives of nearby residents. Numerous factors must be considered during the installation process; every step, from initial planning to final commissioning, is critical. Even the slightest oversight can affect the performance of the noise barrier, so close attention must be maintained throughout the entire installation process. LuoFu has summarized the key points to note when installing noise barriers as follows.
I. Pre-Construction Preparation (Determining Overall Accuracy)
The installation of highway noise barriers involves multiple stages, making thorough preparation critical. A detailed assessment of the acoustic environment and structural safety is essential to optimize the design, striking a balance between noise reduction, structural integrity, and aesthetic appeal, while ensuring compliance with relevant regulations and obtaining the necessary approvals. In addition, a meticulous construction plan must be developed, and material quality must be strictly controlled to lay a solid foundation for subsequent construction work.
1. Comparison of Drawings with On-Site Verification
Three types of foundations are distinguished: embankments, cuttings, and bridge guardrails. For bridge sections, reinforced steel anchoring or pre-embedded steel plates should be prioritized; for embankments, independent reinforced concrete foundations should be constructed.
Use a total station to stake out the entire route; the horizontal deviation of the column centerline should be ≤±5 mm, and the elevation error should be ≤10 mm. Verify the locations of slope arches, utility lines, and culverts to avoid underground utilities.
Re-measure distances at key points to confirm the barrier height and the ratio of sound-absorbing panels to sound-insulating panels; an insufficient effective barrier height will directly result in noise reduction failure.
2. Inspection of Materials upon Delivery
Steel columns (H-beams): Fully hot-dip galvanized, with a zinc coating thickness of ≥85 μm; free of bending, deformation, or blistering of the zinc coating; Grade 8.8 high-strength bolts, supplied with corresponding galvanized washers and lock nuts.
Soundproof Panels
Metal Soundproof Panels: Panel thickness ≥ 1.0 mm; filled with polyurethane acoustic foam or spun glass wool, wrapped in waterproof fiberglass cloth; no exposed foam or sagging; aluminum foam acoustic core material may also be used.
Transparent PC Panels: Thickness ≥ 8 mm; Class B1 flame retardant; no scratches or cracks;
3. Traffic management and on-site safety measures are also among the most critical safety measures during highway construction.
Within a 500-meter radius upstream and downstream of the construction zone, signs indicating a 40 km/h speed limit, “Construction Ahead” signs, reflective cones, and guardrails must be installed. Dedicated personnel must be assigned to direct traffic, and flashing warning lights must be installed at night.
Separate lifting zones and material storage areas should be designated. Place wooden blocks under the bottom of structural components to prevent scratching the galvanized coating. It is strictly prohibited to pile sand, gravel, or steel within 1.5 meters of the excavation edge to prevent pit collapse.
Work suspension regulations during inclement weather: Lifting operations or concrete pouring must not be performed when wind speeds reach Force 6 or higher, during rain, or under icy conditions.
II. Installation of Foundations/Embedded Components
The construction of foundations and embedded components is also critical to structural stability.
1. Key Points for Isolated Foundations on Road Beds
The standard excavation depth is 1.5–2.5 m, which must be below the local frost line. A 10 cm thick crushed stone base layer must be laid and compacted at the bottom, and the excess excavation must be backfilled with C30 concrete of the same grade; the use of mixed soil for backfilling is prohibited.
The concrete cover thickness must be ≥35 mm. Anchor bolts must be securely fastened to the positioning plates, with positional deviations ≤±2.5 mm, and the bolt protrusion length must be consistent.
Concrete must be compacted in layers using vibration, with a curing period of no less than 7 days; in winter, it must be covered with an insulating blanket.
A simple drainage ditch must be installed on the outer side of the foundation to prevent prolonged rainwater saturation of the foundation, thereby avoiding subgrade settlement and column tilting.
2. Installation of Bridge Guardrails
This is also a critical step in the reinforcement installation process. The top surface of the guardrail must be ground to roughen it, and loose mortar and oil stains must be removed. Reinforcement adhesive must be applied thoroughly, and the anchorage depth must comply with code requirements; the direct use of expansion bolts as load-bearing components is strictly prohibited.
Pre-embedded steel plates must be spot-welded to the guardrail reinforcement to enhance strength, and special attention must be paid to subsequent anti-corrosion treatment of the welded areas. The top surface of the foundation must be leveled, with height differences controlled within 5 millimeters.
III. Installation of H-Beam Columns
Strict control must be exercised over the verticality and parallelism of H-beam columns during installation.
1. Use nylon slings for hoisting; never use steel wire ropes to directly secure the columns, as this may scratch the galvanized anti-corrosion coating. Select lifting points at the pre-drilled holes on the columns, perform a test lift with the column 20 cm off the ground to check for balance, and then position and install it.
2. After the column is in position, use a dual-axis level to calibrate: verticality ≤ 1.5 mm/m, straightness of all columns along the line ≤ 40 mm; deviation in center-to-center distance between columns ≤ ±10 mm.
3. Tighten the bolts in three stages using a diagonal pattern to ensure torque meets specifications (typically ≥30 N·m), and install spring lock washers on all bolts. Re-measure verticality after tightening; retighten bolts at any points showing wobble.
4. Immediately grind and remove rust from welded and cut areas, then apply two coats of zinc-rich primer, followed by a topcoat to prevent corrosion.
IV. Screen Suspension and Assembly
1. Installation must be performed using a bottom-up approach, proceeding section by section from one end to the other. Each panel must be secured with a 4-millimeter anti-fall steel wire rope, allowing for a 0.5-meter buffer to prevent the risk of the panel falling from a height.
2. When inserting panels into the column slots, place them gently; do not force or squeeze them in. Do not remove the protective film from the surface of the transparent PC panels until installation is complete to prevent scratches.
3. The gaps between the top, bottom, left, and right sides of the panels must be ≤2 mm. Gaps must be strictly controlled, as excessive gaps will result in increased sound leakage and significantly reduce noise reduction performance.
4. Each panel must be securely fastened using clips or self-tapping screws, with a maximum spacing of 300 mm between fastening points; on road sections subject to prolonged vehicle vibration, additional fastening points must be added.
V. Key Factors for Sealing and Noise Reduction
All gaps must be completely sealed, as noise leakage is the primary cause of failure to meet noise reduction standards.
1. Apply EVA foam sealing strips along the entire length of the inner sides of the grooves in the barrier panels and posts, ensuring there are no breaks or loose sections.
2. Apply weather-resistant silicone sealant to panel joints and to the gaps between the bottom of the barrier panels and the foundation or crash barrier.
3. Corner overlaps must be installed where the barrier meets slopes, guardrails, or bridge piers at both ends; leaving open passages is strictly prohibited. Access doors must be equipped with double-layer sealing strips.
4. Rain caps of uniform specifications should be installed at the top to prevent rainwater from seeping into the sound-absorbing core material. Failure to do so will cause the sound-absorbing material to lose its effectiveness due to moisture absorption and lead to corrosion inside the posts.
VI. Special Precautions for Different Road Sections
1. High-wind and coastal sections: The spacing between posts must be reduced, and diagonal bracing must be installed. Construction must strictly comply with design wind load specifications. In addition, work at heights is prohibited during high-wind conditions.
2. Sections Near Residential Areas: Construction must be conducted during daylight hours; high-noise operations such as cutting and lifting are prohibited at night. Sound barriers should preferably use a double-sided sound-absorbing structure to enhance the suppression of low-frequency noise.
3. Interchanges and Curved Sections: Increase the barrier height and turning radius as specified in the drawings to prevent sound wave diffraction; additionally, the barrier on the inner side of the curve should be slightly raised.
4. Underpasses and viaducts: When performing work at heights of 2 meters or higher, all personnel must wear double-hook safety harnesses; erect work platforms; install fall protection nets below; and ensure all tools are stored in bags—throwing materials is strictly prohibited.
VII. Key Points for Self-Inspection and Acceptance Upon Completion
1. Structural Safety Inspection
Re-inspect the verticality and straightness of all columns along the entire route; conduct random re-inspections of bolt torque to ensure there is no looseness; gently push and press the partition panels to confirm there is no wobbling.
Ensure that fall arrest ropes, capstones, and corner components are intact and secure, with no risk of missing or detached parts.
2. Acoustic Sealing Inspection
All gaskets and sealants inside the screens must be continuous and intact, with no breaks or visible gaps; sound-absorbing foam must not be exposed and must not have collapsed due to moisture.
3. Appearance and Corrosion Protection Inspection
Galvanized and powder-coated surfaces must not have significant scratches or peeling; corrosion protection at weld seams must be complete; transparent panels must not have cracks or white haze.
4. Actual Noise Reduction Measurement: Upon completion, noise measurements must be taken at sensitive points; insertion loss must meet design requirements (typically ≥15–25 dB(A)).
5. Post-Completion Protection of Finished Products: After completion, loose components and sealant residues on the road surface must be removed to prevent them from being crushed by vehicles or scattered.
VIII. Ongoing Maintenance and Management
Ongoing maintenance and management are key to ensuring the long-term effective operation of noise barriers. This includes regular inspections and maintenance, identifying potential safety hazards, monitoring noise reduction effectiveness, and developing contingency plans to address emergencies. If the noise barrier incorporates landscaping, plant maintenance is also required. Through continuous maintenance and management, the safety, effectiveness, aesthetic appeal, and environmental sustainability of the noise barrier can be ensured, thereby enabling it to provide long-term noise reduction.
The above outlines the key considerations for installing highway noise barriers as summarized by LuoFu. In summary, installing highway noise barriers is a complex process; only by comprehensively considering all factors can we ensure that the barriers are safe, effective, aesthetically pleasing, and environmentally sustainable. Selecting a professional team to handle design, construction, and maintenance is crucial.