Item-selection determination for graded-gravel replacement fill in excavation pits: the distinction among replacement-fill ground treatment (A-2-4 gravel spreading), foundation backfill and bedding layers, and quantity calculation (Beijing DB11/T 2382-2024 basis)

Topic Positioning

Resolving the item-selection determination when soft/non-uniform soil layers are strengthened by graded-gravel (or sand-gravel type) replacement after foundation-pit excavation: under the Beijing DB11/T 2382-2024 "Construction Consumption Standard" basis, which sub-item the replacement fill uses, and how it is distinguished - in item selection and quantity calculation - from the two neighbouring categories of "foundation backfill" and "bedding layer".

Core Conclusions

1. Attribution - Clause 4.3.1 of the body (original text): "For the strengthening of soft or non-uniform soil layers after foundation-pit excavation, the construction consumptions shall be executed under the corresponding replacement-fill ground-treatment items." -> Apply Appendix A "A.2 Ground Treatment and Slope Protection Works", Table A.2.1-1 "replacement-fill ground treatment" - attributed neither to backfill nor to bedding.
2. Sub-item for graded gravel: Table A.2.1-1 contains 4 sub-items - A-2-1 and A-2-2 "manual filling of sand/gravel" (for the compacted and rolled conditions respectively), A-2-3 "spreading, sand (stone chips)", and A-2-4 "spreading, gravel" (unit m3; work content: spreading in layers, leveling, compaction). The standard sets no sub-item literally named "graded gravel"; graded gravel belongs to the gravel type of replacement fill and is itemized under A-2-4; where the design specifies sand or stone-chip replacement, use A-2-3.
3. Excavation and fill separated - Clause 4.3.2 of the body (original text): "The construction consumptions of replacement-fill ground treatment shall not include the work content of excavating the in-situ soil; excavation of the in-situ soil shall be executed under the provisions of Clauses 4.2.1 to 4.2.27 of this standard." The replacement sub-items exclude digging out the soft soil and the hauling and disposal of spoil, which must be itemized separately under the earthworks chapter.
4. Quantities - Clause 4.3.16 of the body (original text): "The quantity of replacement-fill ground treatment shall be calculated by volume per the dimensions shown on the design drawings." The cushion layer of composite foundations follows Clause 4.3.3 - "executed under the corresponding spreading items".
5. Distinction from "foundation backfill" - by position and design intent, not by material: replacement fill is a ground-treatment measure that replaces soft soil to form a bearing stratum (thickness per the ground-treatment design); backfill is the filling, after the foundations are completed, of the voids around the foundations, in the working spaces and under room floors. With the same graded sand-gravel material, foundation backfill applies "A.1.3-1 foundation backfill" A-1-38 "graded sand-gravel" (work content: backfilling, watering, compaction). Backfill quantities: Clause 4.2.21 - "the quantity of foundation backfill shall be calculated as the excavation volume less the volumes occupied by the foundations, buildings and structures and bedding below the outdoor design ground level"; Clause 4.2.22 - room-floor backfill "shall be calculated by volume as the area between main walls, after deducting the areas occupied by heating trenches, cable trenches, drainage trenches and equipment foundations, multiplied by the height from the outdoor design ground to the underside of the first-floor bedding". "Replacement fill" and "backfill" may coexist in one project and are itemized separately.
6. Distinction from "bedding layer": a bedding layer is a constructional course of the foundation (a conventional thin layer, the operations being placing/casting); the standard itemizes it in A.4 Masonry Works Table A.4.5 bedding (e.g. A-4-55 "2:8 lime-soil", A-4-57 "grouted cobble") and A.5 Concrete and Reinforced Concrete Works Table A.5.1-1 bedding (e.g. A-5-2 "foundation bedding, concrete"); replacement fill and bedding differ in labor/material/machinery composition and operations and must not be interchanged (replacement = layered spreading and compaction; bedding = mixing and placing/casting). Terms (GB/T 50941-2014): "foundation bedding" is "a low-strength-grade concrete, three-part-soil or lime-soil course placed between the foundation and the foundation soil, for damp-proofing, drainage, frost protection and improving the working conditions of the foundation and the ground"; the "replacement-fill method" is "a ground-treatment method in which the soft soil layer of the natural ground is excavated and backfilled with rock and soil materials of better physical and mechanical properties".
7. BOQ feature-description reference (GB/T 50854-2024 Appendix B Ground Treatment and Slope Protection Works): "the 'type of replacement material' of replacement-fill bedding may be described as sand-gravel, silty clay, lime-soil, fly ash, slag, etc.; where geosynthetics are involved, the corresponding feature descriptions shall be added."

Applicable Boundaries

• Applicable basis: Chapter 4 of the body and Appendix A of the Beijing local standard DB11/T 2382-2024 "Construction Consumption Standard"; the sub-item numbers (A-2-4 etc.) belong to this standard - other provinces/cities differ in the item division and numbering of their consumption/pricing quotas and must not be copied.
• Applicable objects: replacement-fill strengthening of soft or non-uniform soil layers after foundation-pit excavation (including sand-gravel and gravel-type material replacement); where the design imposes explicit requirements on the replacement material, follow them (e.g. sand/stone-chip replacement uses A-2-3).
• This card resolves the qualitative determination of "which item to apply" and does not replace the specific pricing determined by the contract and the design documents; specific consumption data are subject to the corresponding sub-items in the appendix of the standard.
• Note: the replacement sub-items exclude in-situ excavation and the hauling and disposal of spoil (executed separately under 4.2.1 to 4.2.27) - do not omit the excavation when itemizing, and do not double-count it inside the replacement sub-item.

Further Reading

• DB11/T 2382-2024 "Construction Consumption Standard": body 4.3 Ground Treatment and Slope Protection Works (4.3.1 to 4.3.26); body 4.2 Earth and Rock Works (4.2.1 to 4.2.27, including Table 4.2.15-1 working-space widths required for foundation construction, Table 4.2.15-2 depth thresholds and coefficients for sloped excavation, Table 4.2.17 working-space widths required for pipeline construction); Appendix A "A.2 Ground Treatment and Slope Protection Works" Table A.2.1-1 replacement-fill ground treatment (sub-items A-2-1 to A-2-4); "A.1 Earth and Rock Works" continued Table A.1.3-1 foundation backfill (A-1-38 graded sand-gravel, A-1-42 room-floor backfill etc.); "A.4 Masonry Works" Table A.4.5 bedding (A-4-55, A-4-57); "A.5 Concrete and Reinforced Concrete Works" Table A.5.1-1 bedding (A-5-2).
• Terms and BOQ basis: GB/T 50941-2014 "Standard for Terminology of Building Foundation" 7.2.1 replacement-fill method, 8.1.7 foundation bedding; GB/T 50854-2024 "Standard for Calculation of Quantities of Building and Decoration Works" Appendix B Ground Treatment and Slope Protection Works.
• Cross-reference: DB11/T 2382-2024 Appendix D Municipal Works D1-1-27 "roadbed backfill, graded sand-gravel" - the same type of material attributed by position (the municipal basis itemizes it as roadbed backfill), illustrating the "by position, not by material" itemizing principle against the building basis.