Whether pipe-trench backfill quantities deduct the pipe volume: the 500 mm diameter demarcation rule and comparison of standards' calibers

Topic Positioning

Whether backfill quantities of pipe trenches (conduits) deduct the volume occupied by the pipe is a common dispute in compiling and reviewing backfill quantities across water supply and drainage, municipal, railway, and landscape trades; the crux is the applicability of the "500 mm diameter" demarcation and the caliber differences among standard volumes. This card consolidates the verbatim calibers and execution points of multiple current texts: the railway quota, local consumption standards, the utility-tunnel standard, the municipal maintenance standard, and the national BOQ measurement standard.

Core Conclusions

Most quota systems demarcate at pipe diameter (nominal diameter / pipe structural width) 500 mm: 500 mm and below no deduction; above 500 mm deduct. The verbatim calibers of each system (in compilation, the text of the volume in force governs):

1. Railway budget quota — TB/T 10833-2024 Budget Quota for Railway Works, Vol. 12: Depot, Rolling Stock and Machinery Works, volume notes, "V. Quantity calculation rules", Item 2: "In the original-soil backfill quota, for pipes of nominal diameter 500 mm and below, the backfill quantity is computed as the excavated quantity; for pipes of nominal diameter above 500 mm, the backfill quantity is computed as the excavated quantity minus the volume occupied by the pipe."
2. Hunan Province 2025 Consumption Standard for Building and Decoration Works: "For pipe-trench backfill, the backfill quantity is computed as the excavated volume minus the volumes of the pipe and the base. Pipes of nominal diameter within 500 mm are not deducted; pipes above 500 mm are deducted per Table 9. Where purchased sand/gravel etc. is used for backfill, the full pipe volume shall be deducted and the quantity computed as the actually backfilled volume." Table 9 is the "table of equivalent pipe backfill volumes (m3/m)", looked up by material and diameter.
3. Shenzhen SJG 111.1-2022 Consumption Standard for Urban Underground Utility Tunnel Works (Vol. 1: Earthworks, Support and Pile Foundations), 1.2.9: "For pipes with structural width within 500 mm no volume is deducted; for pipes with structural width above 500 mm, the volumes occupied by the pipe cushion, pipe base, pipe, and various chambers and other auxiliary structures shall be deducted, wherein the volume of a single pipe may be computed as-built or with reference to Table 1.2.9." The same clause: trench and pit backfill quantities are computed in cubic meters as excavated volume minus the volumes of embedded structures (including base cushion, base, superstructure, etc.). Table 1.2.9 is "deducted earthwork volume of pipes (m3/linear meter)".
4. Shenzhen SJG 84-2020 Consumption Standard for Municipal Maintenance Works, Vol. 2: Water Supply and Drainage Maintenance Works, 7.2.9: "Conduits with structural width not greater than 500 mm may have no volume deducted; conduits with structural width greater than 500 mm shall have the volumes occupied by the conduit cushion, base, outer contour of the conduit body, and chambers and other auxiliary structures deducted."
5. Beijing DB11/T 2382-2024 Consumption Standard for Construction Works — municipal works 7.1.15 and landscape works 8.1.12 share the caliber: "Quantities shall be computed as excavated volume minus the volumes occupied below the design ground level by embedded structures, bases (including cushions), pipes and structures" — i.e., expressed directly as "minus pipes and structures", with no "within 500 mm no deduction" exemption; building and decoration works 4.2.21: foundation backfill quantity "is computed as excavated volume minus the volumes of foundations, buildings, structures, and cushions embedded below the outdoor design ground level".
6. National GB/T 50857-2024 Standard for Measurement of Municipal Works, Appendix A, Table A.3.1 (code 040103): BOQ items, item-characteristic descriptions, measurement units, and quantity calculation rules for backfill and surplus spoil follow that table; BOQ measurement follows this caliber (note the separate track from consumption-quota calibers).

Execution points:

• How much to deduct: where an appendix table exists, deduct per the table (equivalent pipe backfill volume / deducted earthwork volume tables, in m3/linear meter, by material and diameter); where none, deduct as-built (pipe outer-diameter section x trench length, including cushion and base).
• Scope of deduction: generally the pipe body + base/cushion; the Shenzhen system expressly also includes chambers and other auxiliary structures.
• Backfill material affects deduction: Hunan 2025 expressly requires deducting the full pipe volume when purchased sand/gravel etc. is used, with no 500 mm exemption.
• Special caution for Beijing projects: follow the "minus pipes and structures" caliber of DB11/T 2382-2024; do not habitually apply other provinces' "within 500 mm no deduction" rule.
• Concept distinction: the measurement deduction rule (whether to deduct pipe volume) and the workmanship requirements for backfill around pipes (fill, compaction) belong respectively to quantity calculation/quotas and pipe construction acceptance codes, and must not be mixed.

Applicable Boundaries

• Applies to compiling, reviewing, and reconciling quantities of pipe trench/conduit backfill (both original-soil and purchased-material backfill); not applicable to structural design, material selection, or construction-method determination.
• The "500 mm demarcation" is not a nationwide unified rule but a per-volume caliber: railway per TB/T 10833-2024 Vol. 12, Hunan per its 2025 consumption standard, Shenzhen per SJG 111.1-2022 or SJG 84-2020; Beijing DB11/T 2382-2024 has no such exemption. Before execution, confirm the adopted standard's name, volume number, and edition.
• The demarcation measure differs: railway uses "nominal diameter", Shenzhen uses "pipe structural width" (outer structural width) — not directly transferable across systems.
• Appendix-table values (Table 9, Table 1.2.9, etc.) change with standard editions; look up the current edition's table rather than carrying over old values; the clause texts here are excerpts — the published texts govern.

Further Reading

• TB/T 10833-2024 Budget Quota for Railway Works, Vol. 12: Depot, Rolling Stock and Machinery Works, volume notes "V. Quantity calculation rules", Item 2 (original-soil backfill).
• Hunan Province 2025 Consumption Standard for Building and Decoration Works, earthwork backfill chapter and Table 9 "equivalent pipe backfill volume table" (m3/m).
• SJG 111.1-2022 Consumption Standard for Urban Underground Utility Tunnel Works (Vol. 1: Earthworks, Support and Pile Foundations), 1.2.9 earthworks and Table 1.2.9 "deducted earthwork volume of pipes" (m3/linear meter).
• SJG 84-2020 Consumption Standard for Municipal Maintenance Works, Vol. 2: Water Supply and Drainage Maintenance Works, 7.2.9 general items and Table 7.2.9 slope coefficients.
• DB11/T 2382-2024 Consumption Standard for Construction Works: municipal works 7.1.15 (other-position backfill), landscape works 8.2.12 (backfill), building and decoration works 4.2.21 (foundation backfill).
• GB/T 50857-2024 Standard for Measurement of Municipal Works, Appendix A, Table A.3.1 backfill and surplus spoil disposal (code 040103).