Lead in Earthwork – Identify the incorrect statement Consider the following statements about lead (horizontal hauling distance) in earthwork measurement and payment. Which statement is incorrect as per common IS-style practice?
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ALead is the average horizontal straight distance between the borrow pit and the place of spreading soil.
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BLead is calculated separately for each small block within the excavated area.
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CFor distances up to about 500 m, the unit of lead is taken as 50 m in schedules.
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DWhere lead exceeds about 2 km, the unit of lead is commonly taken as 1 km.
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ELead is measured between the centroids of excavation and fill.
Answer
Correct Answer: Lead is calculated separately for each small block within the excavated area.
Explanation
Introduction / Context:Lead and lift are fundamental to pricing earthwork haul. Misinterpreting their definitions can distort quantities, rates, and logistics planning. Examinations often include conceptual questions to ensure engineers internalize the correct measurement basis for transporting soil from cut to fill.
Given Data / Assumptions:
- Standard departmental schedules and IS 1200-style conventions.
- Borrow and spoil/embankment locations identifiable on drawings.
- Average haul used for payment unless special haul roads or staged dumps are specified.
Concept / Approach:
Lead is not determined for every micro-block of excavation. Instead, it is measured as the straight-line horizontal distance between the centroid (center of gravity) of the excavation area and the centroid of the fill area. For short hauls, schedules commonly adopt 50 m lead units up to about 500 m; for long hauls beyond about 2 km, 1 km units are used.
Step-by-Step Solution:
Define lead correctly: horizontal distance between centroids of cut and fill.Check unit practice: 50 m steps up to roughly 500 m; beyond long haul, 1 km steps.Evaluate statements: options A, C, D, and E align with standard practice; option B suggests per-block calculation, which is incorrect.Verification / Alternative check:
Typical SOR notes and MoRTH/departmental specifications use centroid-to-centroid lead; project-specific methods only deviate when explicitly stated.
Why Other Options Are Wrong:
They are not wrong: A, C, D, and E are consistent with standard definitions and unit steps for lead.
Common Pitfalls:
Measuring along haul roads instead of straight distance for payment; ignoring separate items for extra lead; confusing lead (horizontal) with lift (vertical).
Final Answer:
Lead is calculated separately for each small block within the excavated area.