When undertaking pile foundation construction, particularly for deep excavations and the installation of high drop fall protection barriers, adherence to stringent safety measures is essential to ensure both worker safety and the integrity of the construction process. Below is a comprehensive guide to the safety protocols and construction methods that need to be followed.
1. Fall Protection Barriers for High Excavations
The first section of the pile protection wall must rise at least 20cm above the opening ground level, serving as a safety baseboard around the hole. Within a 2-meter radius of the pile opening, no debris should be stored. Protective barriers should be set up around the wellhead to prevent falling objects. Steel tube barriers should be placed around the excavation’s slope top, with a height of 1.2 meters to prevent unauthorized personnel from entering. During vertical transportation, measures must be taken to prevent soil and debris from falling from the hoist bucket.
Workers must wear safety harnesses while operating at the wellhead to avoid falls. An emergency ladder must be in place for situations such as sudden power outages, enabling workers to ascend quickly. When excavating below 5 meters, a steel reinforcement shield net should be installed, and the hoist bucket must not be filled to prevent spillage.
2. Ventilation and Toxic Gas Prevention
Before beginning work in a pile foundation hole, it is critical to establish proper ventilation. Each time workers enter the hole, they must ensure that the airflow is active for at least 15 minutes. Fresh air should continuously flow into the hole throughout the construction. Gas detectors should be used to monitor the air for toxic gases such as CO and methane, especially when working at depths exceeding 4 meters.
Gas masks must be available for emergency rescue operations in case of power failure or hazardous gas exposure.
3. Electrical Safety
In the construction site’s low-voltage electrical circuits, a TN-S zero-protection system must be implemented, ensuring safety for all workers. Protective grounding and neutral lines should be properly separated and must not serve dual purposes. Proper installation of leakage protection devices, especially for damp and corrosive environments, is essential to minimize electrical hazards.
Switchgear and distribution boxes must be securely mounted and free from damage, and no exposed live wires should be allowed to come into contact with scaffolding or other equipment. Specific grounding resistance levels must be maintained, and the electrical setup must be regularly inspected to prevent electrical faults.
4. Deep Manual Pile Excavation: Quality Control
Material Quality Control Measures
Before construction, materials such as steel reinforcement, cement, sand, and stone should be obtained from certified suppliers. These materials must be inspected and approved before use on-site.
Excavation Procedures
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Preparation: Before excavation, ensure that all necessary documents, including the geological report, construction blueprints, and quality control reports for materials, are in place.
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Safety Measures: Emergency ladders, safety helmets, hoists, and reliable safety equipment should be available on-site. Ventilation equipment is required when the excavation depth exceeds 5 meters.
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Excavation and Shoring: Excavation should be conducted in stages, with each stage being supported by temporary shoring to prevent collapse. Concrete reinforcement walls should be installed as excavation progresses.
Excavation Control and Measuring
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Positioning: Pile positions should be accurately marked using precise measurements based on the project’s design. The excavation should proceed with careful monitoring of alignment and depth.
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Verticality: Ensure that the pile remains vertical by using control lines, measurement tools, and visual markers. Any deviations in verticality should be addressed immediately.
Concrete Wall Installation
For deep excavations, the use of custom steel forms to cast protective concrete walls is essential. These walls must be poured with an appropriate concrete mix, which should meet the specified strength and curing requirements. Each section of the concrete must be properly vibrated and monitored for integrity.
5. Drilling and Excavation of Piles
The pile hole should be excavated from top to bottom, using a combination of manual labor and mechanical tools. The soil should be removed in layers, starting from the middle of the hole and working outward. When encountering difficult geological conditions such as soft soil or flowable sand, reinforced steel casings should be used to prevent collapse.
Drilling Methodology
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Soil Type: For each type of soil (e.g., gravelly clay, fully weathered granite), adjust the excavation method to ensure efficient and safe excavation. Harder layers may require pneumatic drills or air hammers for breakage.
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Reinforcement Cages: Steel cages must be prepared and installed within the pile holes, ensuring that the cage fits securely and is appropriately anchored in place.
Concrete Pouring
Once the excavation is complete, concrete should be poured immediately to avoid compromising the hole. A pump or concrete bucket should deliver concrete to the bottom of the hole, and it must be vibrated properly to ensure there are no voids.
6. Final Inspections and Testing
Before completing the pile, a thorough inspection must be conducted to check the vertical alignment, depth, and quality of the concrete. The final bottom of the pile must be properly sealed with concrete to prevent water infiltration or soil degradation.
By maintaining rigorous safety standards and construction techniques, the integrity of the pile foundation can be ensured, leading to a safer and more durable structure.
