Load-Bearing Standards for Underground Prefabricated Housing

The load-bearing standards for underground prefabricated housing must be determined based on specific scenarios and design requirements, with a common load-bearing range of 200-10,000 kg/m². The specific standards should be comprehensively determined according to the structural type, usage scenario, and relevant codes.

I. Load-Bearing Standards for Common Scenarios

1. Ordinary Residential Basements: The load-bearing standard per square meter should not be less than 2.5 kN/m² (approximately 250 kg/m²). If reinforced concrete structures are used, the concrete strength grade should not be lower than C25. For example, with C30 concrete, a prefabricated slab with a thickness of 120 mm and a span of 3.6 meters can bear approximately 3.46 tons per slab.
2. Fire Lanes and Firefighting Access Areas: The design live load uniformly distributed standard value is 35 kN/m² (approximately 3,500 kg/m²), which must meet the requirements for vehicle passage during emergencies.
3. Industrial or Warehousing Scenarios: The live load standard value can reach 5.0 kN/m² (approximately 500 kg/m²). Prefabricated slabs of the same specifications can bear up to 7.2 tons; if equipped with high-strength concrete (such as C50) and double-layer reinforcement, the load-bearing capacity can exceed 10 tons.

II. Differences in Load-Bearing Capacity Among Prefabricated Slab Types

1. Concrete Hollow Slabs: Commonly used in rural self-built houses, the national standard for uniformly distributed loads is 200-250 kg/m². For example, a hollow slab that is 3.6 meters long and 0.6 meters wide can bear a total load of approximately 432 kg when uniformly distributed.
2. Solid Prefabricated Slabs: Used in areas with higher loads (such as kitchens and bathrooms), with a load-bearing capacity of 250-300 kg/m²; solid slabs produced by large factories (with sufficient reinforcement and a concrete grade of C30 or higher) can reach 300 kg/m².
3. Prestressed Prefabricated Slabs: When the span is within 3 meters, the load-bearing capacity per square meter is 300-400 kg; when the span exceeds 4 meters, the load-bearing capacity remains at 250-300 kg, which is 20% higher than that of ordinary slabs of the same span.

III. Key Influencing Factors

1. Span: The shorter the prefabricated slab, the stronger its load-bearing capacity. For example, a hollow slab with a span of 2.4 meters can bear 250 kg/m², while a slab with a span of 3.6 meters can only bear 200 kg/m².
2. Thickness and Reinforcement: For every 10 mm increase in thickness, the load-bearing capacity increases by 20%-30%; double-layer reinforcement can significantly enhance the flexural capacity.
3. Load Type: Uniformly distributed loads (such as personnel and equipment) and concentrated loads (such as heavy machinery) have different effects on the stress distribution of the slab. Concentrated loads require additional verification of local bearing capacity.

Recommendation: The load-bearing design of underground prefabricated housing should be comprehensively determined based on the specific usage scenario (residential/industrial), load type (uniformly distributed/concentrated), and structural codes (such as the "Code for Design of Concrete Structures" GB50010-2010). Regular inspections and maintenance should be conducted to ensure safety.