The "length" value for pile-head cutting/chiseling quantities and comparison of measurement calibers across quota systems (40d, over-cast height, by count)

Topic Positioning

The meaning and value rules of the "length" in pile-head cutting and chiseling (ring-cutting, trimming) quantities: length = the cut/chiseled height from the as-cast pile top (including over-cast and sludge layer) to the design pile-top level; with a comparison of measurement calibers among the railway buildings quota (TB/T 10831-2024), railway bridge-culvert quota (TB/T 10823-2024), DB11/T 2382-2024, SJG 111.1-2022, and provincial consumption quotas, to prevent cross-system misuse.

Core Conclusions

1. First judge the measurement unit, then decide whether a length is computed Only sub-items measured by volume (m3) need the "length": chiseled pile-head quantity = design pile section area x cut/chiseled length. Sub-items measured by "count" do not compute length — just count piles. General order of values: design provisions govern (drawings usually note the "over-cast height" or the cut-off level); absent design provisions, the fallback caliber of the applied quota system applies.

2. Calibers of each system (fallback values absent design provisions)

1. Railway buildings works (TB/T 10831-2024 volume notes, Item 18):

• Where the chiseled precast pile-head length has no design provision, the head length is computed as 40d (d = main bar diameter of the pile, the larger where diameters differ);
• Chiseled bored-pile heads are computed by volume as the design over-cast height (0.50 m absent design provision) x the design pile section area;
• Where the precast pile cut length is <=1 m, the corresponding driving/pressing quantity is not deducted; where >1 m, the excess is deducted as-built from the driving quantity, but the pile body price is not deducted;
• Companion sub-items by unit: cutting square pile heads in m3 (FY-185), cutting pipe piles by count (FY-186), chiseling precast/bored pile heads in m3 (FY-187/188), tidying pile-head rebar per 10 piles (FY-189); work content includes cutting/chiseling concrete, hauling blocks out of the pit, welding pile bars to foundation bars, and straightening pile-head bars.

2. Railway bridge and culvert works (TB/T 10823-2024 volume notes, Item 11): ring-cut pile-head quantities are computed by the design number of piles tiered by pile diameter — not by volume, no length; sub-items QY-229-231 are measured "per pile", tiered at diameter <=1.0/<=2.0/<=3.0 m. Also note: (1) the ring-cut sub-item excludes hauling of cut heads, which is computed separately with reference to rock hauling; (2) the reinforced concrete square-pile and (prestressed) concrete pipe-pile quotas already include amortized quantities of guide piles, followers, and chiseled heads — not counted again.
3. Local standards:

• DB11/T 2382-2024 Table A.3.4 "chiseling pile heads" measured in m3 (e.g., A-3-19 chiseling pile heads, reinforced concrete piles), work content: chiseling head concrete, cutting rebar, straightening head bars (excluding spoil hauling); the volume prints no "absent design provision" fallback clause — length per the design-confirmed chiseled height.
• SJG 111.1-2022 (3.2.4 pile foundation works): quantities of chiseled reinforced concrete above pile tops are computed in cubic meters as the volume chiseled.
• Provincial consumption quota (draft-for-comment caliber, the most complete, usable as a compilation reference): chiseled precast pile heads by volume as shown pile section x chiseled length, the length taken as 40d absent design provision (d = main bar diameter, the larger where differing); rotary, rotary-excavated, impact, and hole-reaming bored piles by design over-cast height (1 m absent provision) x pile section; driven-tube and screw piles by over-cast height (0.5 m absent provision) x pile section; precast pile cutting by the design-required count.

3. Over-cast control values in construction codes (quality background; must not replace measurement rules)

• GB 50202-2018 Clause 4.1.4: the bored pile top shall be at least 0.5 m above the design level;
• JGJ 94-2008: the over-cast height of slurry-supported bored piles should be 0.8-1.0 m; for long-screw cast-in-place piles not less than 0.3-0.5 m; after forming, the top of driven and internal-tamping driven piles should be within 500 mm above the design pile-top level;
• JGJ 79-2012 Clause 7.7.3: for CFG piles the cast top should be not less than 0.5 m above the design pile top;
• T/ZCEAS 1008-2025 Clause 6.1.4: for screw piles the cast top should be 0.5-1.0 m above the design pile top.

4. Distinctions and preventing double pricing

• "Cutting piles" and "chiseling pile heads" are different things: cutting affects the deduction rules for driving quantities (railway buildings volume: <=1 m no deduction, >1 m deduct the excess); chiseling is a separate sub-item whose unit may also differ (square-pile cutting in m3, pipe piles by count).
• Distinguish from follower length: followers in piling are computed as design pile-top level to pre-driving natural ground plus 0.50 m (TB/T 10831-2024 volume notes 18(I)3).
• Hauling, pile-head rebar tidying, welding, and other companion contents are judged per each system's work content for separate counting.

Applicable Boundaries

• Applies to determining measurement and length values for pile-head cutting/chiseling (ring cutting, trimming) when compiling estimates/budgets/BOQs; not for pile-shaft concrete, drilling, or other quantities.
• Calibers must not be mixed across systems: first fix the quota system the project applies (railway station buildings TB/T 10831, bridges/culverts TB/T 10823, local projects the local standard/consumption quota), then the sub-item unit.
• The over-cast heights in construction codes are quality-control requirements and cannot be used directly as measurement lengths; measurement still follows the design or the applied quota.
• The "d" in "40d" is the pile's main bar diameter, not the pile diameter; the larger value where bars differ.

Further Reading

• TB/T 10831-2024 Budget Quota for Railway Works, Vol. 10: Buildings, volume notes 17 and 18 (quantity rules) and Chapter 1 Section 2 pile and foundation sub-items FY-185-FY-189;
• TB/T 10823-2024 Budget Quota for Railway Works, Vol. 2: Bridges and Culverts, volume notes 10 and 11, Section 4 bored and hand-dug piles QY-229-231 (chiseling concrete pile heads) and Section 5 square and pipe piles;
• DB11/T 2382-2024 Consumption Standard for Construction Works, Appendix A.3.4 chiseling pile heads (A-3-19);
• SJG 111.1-2022 Consumption Standard for Urban Underground Utility Tunnel Works (Vol. 1: Earthworks, Support and Pile Foundations), 3.2.4 pile foundations;
• T/ZCEAS 1008-2025 Technical Specification for Screw Grouting Piles 6.1.4; JGJ 94-2008; JGJ 79-2012; GB 50202-2018 related clauses.