Spacing of Prefabricated Piles for Single-Story Houses

The spacing of prefabricated piles for single-story houses should be determined comprehensively based on geological conditions, pile foundation type, construction method, and surrounding environment. Specific requirements are as follows:

I. Spacing Requirements with Adjacent Piles

According to the "Code for Design of Building Foundation" (GB 50007-2011), the center-to-center spacing of friction-type prefabricated piles should not be less than 3 times the pile diameter. If soil compaction methods (such as hammer driving) are used, the staggered spacing between adjacent piles should be controlled at 3 times the pile outer diameter to account for the disturbance to the soil between piles caused by soil compaction effects. For example, the commonly used PHC prestressed concrete pipe piles in China have diameters ranging from 300mm to 1200mm, corresponding to staggered spacings of 900mm to 3600mm. For smaller pile diameters (e.g., 300mm), a spacing of 900mm can be used; for larger pile diameters (e.g., 1200mm), the spacing should be increased to 3600mm to reduce the impact of soil compaction on pile quality during construction.

II. Spacing Requirements with Existing Buildings

When soil compaction methods (such as hammer driving or static pressing) are used, the spacing between newly driven piles and the foundation of existing buildings should not be less than 1/3 of the pile length. For example, if the pile length is 15 meters, the spacing from existing buildings should be at least 5 meters. This requirement aims to prevent uneven settlement and structural cracking of the existing building foundation caused by soil compaction and vibration during pile driving. If the geological conditions are poor (e.g., soft soil or liquefiable soil), the spacing should be further increased or vibration isolation measures should be taken.

III. Spacing Adjustments for Different Construction Methods and Foundation Types

1. Cement Fly Ash Gravel (CFG) Pile Composite Foundation: If soil compaction methods (such as hammer driving or static pressing) are used for pile formation, the pile spacing should be 3 to 6 times the pile diameter; for single-row pile arrangements under wall foundations, the spacing can be selected within this range.
2. Non-Soil Compaction Methods: For non-soil compaction piles such as bored piles, the pile spacing can be appropriately reduced but must meet the bearing capacity calculation requirements to avoid a reduction in bearing capacity due to group pile effects.

IV. Other Key Influencing Factors

1. Soil Properties: In soft soil, liquefiable soil, or highly sensitive soil, the pile spacing should be appropriately increased (e.g., expanded to 4 to 6 times the pile diameter) to reduce the impact of soil compaction on pile stability.
2. Pile Arrangement: For uniform pile arrangements, the spacing can be selected based on the minimum value specified in the code; for梅花形 (plum blossom) pile arrangements, the spacing can be optimized to improve foundation bearing capacity.
3. Pile Length and Diameter: For piles with a large length-to-diameter ratio (L/D), the spacing should be appropriately increased to avoid excessive lateral soil displacement during construction.

Summary: The spacing of prefabricated piles for single-story houses should be determined by combining code requirements, geological conditions, and construction methods, with the core principle of controlling soil compaction effects, ensuring pile quality, and protecting the safety of surrounding buildings. In practical engineering, it is recommended to further optimize spacing parameters through field pile testing or numerical simulation.