Guidelines on the Choice and Planning of Appropriate Technology in Road Construction

IRC SP 24 — Scope Summary

Scope (Clause 2) defines the extent and application of the document focused on labour-based and equipment-intensive methods for road construction, particularly earthwork and related operations.

Key Points:

• Applies to planning, organisation, and execution of earthwork and road construction using:

  • Labour-based methods
  • Equipment-intensive methods

• Covers selection of construction methods based on:

  • Soil hardness
  • Haulage distance
  • Site conditions
  • Economic and technical feasibility

• Includes resource calculations, equipment output, costing, and sample calculations (see relevant clauses and tables).

Important Tables & Clauses for Scope:

Typical Considerations for Construction Method Selection

• Technical feasibility
• Economic viability
• Social desirability
• Compatibility with site conditions

Example: Equipment Output Table (Excerpt)

flowchart LR
    A[Scope: Road Construction Methods] --> B[Labour-Based Methods]
    A --> C[Equipment-Intensive Methods]
    B --> D[Site Planning & Earthwork]
    C --> E[Equipment Selection & Usage]
    D --> F[Costing & Resource Calculation]
    E --> F

For detailed formulas and tables, refer to clauses 12, 14-21 for resource and cost calculations as per site-specific parameters.

Process of Choosing Optimum Construction Method (IRC SP 24)

The selection is a multi-factor decision involving technical feasibility and site conditions, not just cost.

Key Steps:

1. List all major tasks and quantities considering critical site parameters (e.g., soil hardness, haulage distance).
2. Identify all technically feasible construction methods for each task without initial cost consideration.
3. Use a systematic elimination framework to discard unsuitable methods based on:
   • Technical feasibility
   • Site constraints
   • Equipment availability
   • Safety and environmental factors
4. Rank remaining methods considering cost, time, and resource optimization.

Typical Table Structure (from Table 1 & 2):

Summary:

• Do not rely on single criteria.
• Use a stepwise elimination process.
• Consider all relevant factors systematically.

flowchart TD
    A[List Tasks & Quantities] --> B[Identify Feasible Methods]
    B --> C[Evaluate Technical Feasibility]
    C --> D[Eliminate Unsuitable Methods]
    D --> E[Rank Remaining Methods by Cost, Time, Safety]
    E --> F[Select Optimum Method]

This ensures a balanced, rational choice aligned with project specifics.

IRC SP 24 - Site Clearance (Clause 5.3) Key Points

Scope of Site Clearance

• Remove/store/stack:
  • Trees, bushes, shrubs
  • Grass and vegetation
  • Stumps, rubbish, loose stones
  • Topsoil (50-150 mm depth, organic layer) for reuse

Clearing Limits

• Follow project drawings or extend to areas affecting construction.
• Cut trees/stumps within excavation/fill toe lines to at least 0.5 m below subgrade.
• Retain erosion-protecting vegetation unless removal is necessary.
• Remove topsoil containing organic matter carefully.

Recommended Practices

• Perform clearance well before construction to set lines and assess ground.
• Use labor-based methods with axes, saws, mattocks, winches.
• Use animals or tractors for hauling cleared material.

Summary Table: Site Clearance Tasks & Methods

Additional Notes

• Site clearance is critical for earthwork planning and cost efficiency.
• Ensure clearance aligns with earthwork excavation and haulage planning.

flowchart TD
    A[Start Site Clearance] --> B{Identify Clearing Limits}
    B -->|Within excavation/fill toe| C[Cut trees/stumps 0.5m below subgrade]
    B -->|Outside toe lines| D[Retain vegetation unless removal warranted]
    C --> E[Remove topsoil (50-150 mm)]
    D --> E
    E --> F[Stack/store cleared material]
    F --> G[Set out construction lines]
    G --> H[Begin earthwork operations]

This concise guidance ensures compliance with IRC SP 24 for efficient and environmentally sensitive site clearance.

Balancing Cut and Fill in Road Construction (IRC SP 24)

Though the code does not provide a direct formula, key principles and a sample table for gang balance calculations using flat-bed trucks are given:

Key Parameters (from Table 12):

• Soil type: Hard soil
• Haul distance: 3 km
• Loading height: 0.5 m
• In-situ soil density: 1.7 gm/cc (1700 kg/m³)
• Truck capacity: 5 t or 3 m³ (in-situ volume)
• Truck speed: Loaded 15 km/h, Empty 20 km/h

Balancing Cut and Fill Concept:

• Cut volume = Fill volume (accounting for swell and shrinkage)
• Use bank (in-situ) volume and convert to loose or compacted volume using swell/shrinkage factors.

Basic Formula for Volume Conversion:

[ V_{\text{loose}} = V_{\text{bank}} \times (1 + \text{swell factor}) ] [ V_{\text{compacted}} = V_{\text{bank}} \times (1 - \text{shrinkage factor}) ]

Gang Balance Calculation Steps:

1. Calculate total cut volume (bank measure).
2. Convert cut volume to loose volume for haulage.
3. Calculate number of truck trips = (\frac{\text{Loose volume}}{\text{Truck capacity}}).
4. Calculate cycle time based on haul distance and truck speeds.
5. Determine number of trucks and loaders required to maintain balance.

Example: Truck Cycle Time (T)

[ T = \frac{2 \times \text{Haul distance}}{\text{Average speed}} + \text{Loading time} + \text{Unloading time} ]

flowchart LR
    Cut[Cut Volume (Bank)] -->|Swell factor| Loose[Loose Volume]
    Loose -->|Truck Capacity| Trips[Number of Trips]
    Trips -->|Cycle time| Equipment[Equipment Required]
    Equipment --> Fill[Fill Volume]
    Fill -->|Shrinkage factor| Compact[Compacted Volume]

Note: Refer IRC SP 24 Table 12 for detailed gang balance calculations and equipment productivity norms.

Labour-Based Methods & Productivity (IRC SP 24)

Key Formulas:

• Number of Labourers Required: [ \text{Labourers} = \text{Labour Effective Days} \times \text{Productivity} ]

  • Productivity = output per day per person.

• Effective Labour Days Calculation (Example, Table 10): [ \text{Total working days} = \text{Season days} - (\text{Holidays} + \text{Recruitment loss} + \text{Weather loss} + \text{Labour disputes}) ]

  • Example: (206 - (10 + 10 + 15 + 5) = 166) days

Productivity Input Coefficients (Man-hours per unit):

Notes:

• **WT (Working Time):

IRC SP 24: Equipment Suitable for Earthwork — Key Points

1. Output of Earthmoving Equipment (Clause 6.4, p.41)

• Output depends on machine capacity, cycle time, efficiency, and site conditions.

• Typical formula for output (m³/hr):

  [ \text{Output} = \frac{\text{Bucket Capacity (m}^3) \times 3600 \times \text{Efficiency}}{\text{Cycle Time (sec)}} ]

• Efficiency usually ranges from 0.7 to 0.85 depending on operator skill and site.

2. Equipment Types & Specifications (Clause 6.3)

• Common earthmoving equipment includes:
  • Excavators
  • Front-end loaders
  • Bulldozers
  • Dump trucks
  • Tractors with scrapers

3. Usage Charges & Costing (Clauses 18, 19, 21)

• Usage charges depend on machine hourly rate, fuel consumption, and maintenance.
• Costing formulas consider:
  • Initial cost
  • Operating hours
  • Depreciation
  • Fuel and lubricants

4. Sample Calculation Reference

• See Clause 15 (p.48) for sample earthwork calculations using front-end loaders and dump trucks.

Summary Table: Typical Earthmoving Equipment Output

flowchart LR
    A[Earthwork Equipment] --> B[Excavator]
    A --> C[Front-end Loader]
    A --> D[Bulldozer]
    A --> E[Dump Truck]
    B --> F[Output = Bucket Capacity x Efficiency / Cycle Time]
    C -->

IRC SP 24: Key Points on Cost Calculations (Clause 7)

Purpose of Cost Calculations (7.1.1)

• Compare costs of various construction methods (unit cost basis, e.g., Rs/cu.m earthwork)
• Compare pavement material costs (initial vs haulage costs)
• Prepare financial estimates for approvals

Unit Cost Calculation (7.1.2)

[ \text{Unit Cost} = \sum (\text{Input Coefficient} \times \text{Resource Rate}) ]

• Input coefficient: resource quantity per unit output (e.g., man-hours/cu.m)
• Rate: cost per unit time or unit material (Rs/hr, Rs/cu.m, etc.)

Labour-based Methods (7.2)

• Input coefficients (Tables 4-9) give man-hours per unit output
• Output per man-day depends on working hours (5.5-6 hrs for daily wages, 8 hrs for piecework)
• Example: Excavation cost by daily paid labour
  • Input coefficient = 0.8 man-hr/cu.m
  • Working hours/day = 6
  • Hourly wage = Rs 6/6 = Rs 1/hr
  • Cost = 0.8 × 1 = Rs 0.8/cu.m

Equipment-intensive Methods (7.3)

• Similar approach but input coefficients represent machine hours or fuel consumption
• Use machine usage charges (see Tables 18 & 19)

Summary Table for Labour Cost Example

flowchart LR
    A[Input Coefficient] --> B[Multiply by Resource Rate]
    B --> C[Unit Cost per cu.m]
    C --> D[Compare Different Methods]

For detailed input coefficients and machine charges, refer to Tables 4-9, 18-19 in IRC SP 24 (pages 54-60).

Key Specifications and Formulas for Road Construction Aggregates (IRC SP 24)

1. Aggregate Production & Crushing Plant Capacity

• Stone crushers:
  • Sizes: 400×225 mm, 400×280 mm
  • Capacity: 14-18 tonnes/hr
• Granulators (smaller aggregates):
  • Sizes: 300×175 mm, 300×100 mm
  • Capacity: 5-8 tonnes/hr
• Large scale:
  • Base crushers: 100-150 t/hr
  • Secondary crushers: 50-100 t/hr

2. Hot Mix Plant Capacity & Planning

• Typical capacities:
  • 20-30 t/hr or 30-45 t/hr
• Stockpile aggregates for 15 days minimum at site
• Match number of tipper trucks with plant output
• Use front-end loaders for cold feed bins

3. Sample Calculation for Paving 50 mm Bituminous Macadam

Cycle time for tipper truck (min):

Productivity per tipper/hr:
[ \frac{5 \times 60}{64} = 4.7 \text{ tonnes/hr} ]

Number of tippers required:
[ \frac{30}{4.7} \approx 7 ]

4. Aggregate Consumption & Bitumen Usage

• Aggregate/day = 210 tonnes - 7.35 tonnes (bitumen) = 202.65 tonnes (~135 cu.m

IRC SP 24: Productivity Data for Manual Haul and Unload Operations

Key productivity metrics and formulas from the code:

• Loading Height Correction (Clause 1.5 (b)):
  Productivity is based on a standard loading height of 1.5 m.

  • Base productivity: 0.26 man-hr/cu.m for loading.

• Equivalent Haul Length (Clause 1.5 (c)):
  [ L_{eq} = 20 + 10 \times L ]
  Where (L) = actual haul length in meters.

• Haul and Unload Input (Clause 1.5 (d), Table 7):

  • Productivity for haul and unload: 0.7 man-hr/cu.m.

• Summary Table: Productivity for Manual Haul and Unload

Use these values to estimate labor input for manual earthwork tasks, adjusting haul length using the equivalent haul length formula.

flowchart LR
    A[Manual Loading] --> B[Equivalent Haul Length Calculation]
    B --> C[Manual Haul & Unload]
    C --> D[Total Man-hours = Volume × (Loading + Haul/Unload)]

Key Specifications & Formulas for Compaction (IRC SP 24)

1. Watering for Compaction (Clause 6.5.2)

• Moisture content must be near Optimum Moisture Content (OMC) for effective compaction.

• Water tankers (4000-5000 L capacity) with sprinkler arrangements are used.

• Productivity of water tankers:

  [ \text{Productivity} = \frac{\text{Capacity}}{\text{Cycle Time (fixed + variable)}} ]

• Cycle time includes filling, turning, spraying, haul distance, and speed.

2. Sample Calculation for Watering Units (Clause 6.5.3)

• Example:
  [ 5750 \times 25 \times 0.8 = 28.6 \text{ cu.m (bank)} ]
• Number of watering units required =
  [ \frac{60}{28.6} \approx 2 \text{ units} ]

3. Compaction Density & Thickness (from Table 17)

4. Productivity Calculation for Tip Trucks (Sample from Table 17)

• Cycle time (loading + haul loaded + haul empty + discharge + turning) = 64 min

• Productivity per tipper per hour:

  [ \frac{5 \times 60}{64} = 4.7 \text{ tonnes/hr} ]

• Number of tippers required for 30 tonnes/hr plant output:

  [ \frac{30}{4.7} \approx 7 \text{ tippers} ]

Summary Diagram: Watering & Compaction Cycle

flowchart LR
  A[Water Tanker Filling] --> B[Travel to Site]
  B --> C[Sprinkling Water on Soil]
  C --> D[Compaction with Rollers]
  D --> E[Check Moisture Content]
  E -->|If not optimum| A
  E -->|If optimum| F[Proceed to Next Layer]

**

Soil Stabilisation - IRC SP 24 Key Points

5.7 Soil Stabilisation Essentials:

• Pulverisation & Mixing: Use mechanical equipment (mould-board plough, disc harrow, off-set harrow) for thorough soil pulverisation and uniform mixing.
• Tractor Power:
  • ~50 HP for processing depth up to 200 mm
  • ~110 HP for depth up to 400 mm
• Process:
  1. Loosen soil with mould-board plough
  2. Break clods using disc harrow
  3. Further pulverise with off-set harrow
  4. Adjust moisture, spread stabilizer manually
  5. Mix with 4-6 passes of off-set harrow
  6. Level & compact with power roller

For heavy clays: Pre-treatment with lime is recommended.

Compaction Specifications (Clause 5.6)

• Use 8/10 tonne 3-wheeled power roller for most soils and bituminous layers.
• Light rollers (0.5-2 tonne) only for minor roads.

Productivity Table (Average Output/Day)

Summary Diagram of Soil Stabilisation Process

flowchart TD
    A[Loosen Soil - Mould-board Plough] --> B[Break Clods - Disc Harrow]
    B --> C[Further Pulverise - Off-set Harrow]
    C --> D[

IRC SP 24: Compatibility in Working (Clause 4.5(iv))

While the code does not provide explicit formulas or detailed tables under "Compatibility in Working," the key principle is:

• Ensure all selected construction methods and equipment are compatible with each other and with related project tasks.
• Exclude any methods that conflict operationally or logistically.

Practical Approach:

1. Check Equipment Compatibility:

   • Match capacities and output rates (e.g., earthmoving equipment capacity vs. haulage truck volume).
   • Synchronize working speeds and cycle times.

2. Gang Balance Calculations:

   • Use balanced resource allocation to avoid bottlenecks.
   • Refer to Table 12 for gang balance calculations (earthwork with flat-bed trucks).

3. Cross-Check with Related Tasks:

   • Verify that earthwork, compaction, and paving equipment work in harmony.
   • Avoid overlapping or conflicting schedules.

Example: Gang Balance Formula (Earthwork)

[ \text{No. of Trucks} = \frac{\text{Volume of Earthwork per hour}}{\text{Truck Capacity} \times \text{Trips per hour}} ]

Summary:

• Compatibility ensures smooth workflow and efficient resource utilization.
• Use gang balance tables and output rates for equipment.
• Exclude incompatible methods to maintain project continuity.

flowchart LR
    A[Select Equipment & Methods] --> B{Check Compatibility}
    B -->|Compatible| C[Proceed with Method]
    B -->|Incompatible| D[Exclude Method]
    C --> E[Balanced Workflow]
    D --> A

For detailed equipment output and cost norms, refer to Tables 13-21 in IRC SP 24.

IRC SP 24: Economic Viability & Break-Even Analysis

While IRC SP 24 does not provide explicit formulas under Clause 4.3 or 7, the general approach to economic viability and break-even analysis in road projects includes:

Key Concepts:

• Economic Viability: Comparing total project cost with benefits over its life.
• Break-Even Point: When cumulative benefits = cumulative costs.

Typical Formulas:

1. Net Present Value (NPV): [ NPV = \sum_{t=0}^{n} \frac{B_t - C_t}{(1 + r)^t} ]

• (B_t): Benefits at year (t)
• (C_t): Costs at year (t)
• (r): Discount rate
• (n): Project life (years)

2. Benefit-Cost Ratio (BCR): [ BCR = \frac{\sum \text{Present Value of Benefits}}{\sum \text{Present Value of Costs}} ]

• Economic Viability: BCR > 1 or NPV > 0 indicates viability.

Cost Components (Clause 7):

• Initial construction cost
• Maintenance cost
• User cost savings
• Salvage value (if any)

Summary Table:

flowchart LR
    A[Initial Cost] --> B[Annual Costs]
    B --> C[Calculate Present Value]
    A --> D[Annual Benefits]
    D --> C
    C --> E{NPV > 0?}
    E -->|Yes| F[Project Economically Viable]
    E -->|No| G[Not Viable]

Note: Adopt discount rates and project life as per IRC guidelines or local economic conditions.

The IRC SP 24 does not explicitly provide formulas or tables under "Social Desirability and Employment Considerations." However, based on general engineering practice and local job conditions, here are key points:

Social Desirability & Employment Considerations (General Guidance)

• Social desirability in construction projects often relates to:

  • Employment generation for local labor.
  • Use of locally available materials and resources.
  • Minimizing environmental and social disruption.

• Employment considerations include:

  • Balancing mechanized and manual work to maximize local employment.
  • Training and skill development for local workers.
  • Ensuring fair wages and safe working conditions.

Related IRC SP 24 Clauses and Tables for Practical Calculations:

• Gang balance calculations (Clause 12) help optimize labor and equipment deployment.
• Tables for equipment output and resource calculations (Clauses 13-19) assist in estimating workforce needs and machine usage.
• Costing tables (Clauses 20-21) support decisions on manual vs. mechanized methods, impacting employment.

Example: Gang Balance Calculation Formula

[ \text{Number of gangs} = \frac{\text{Total work volume}}{\text{Output per gang per day} \times \text{Number of working days}} ]

This formula helps plan labor deployment balancing mechanization and manual work to align with social employment goals.

flowchart LR
    A[Project Planning] --> B[Assess Local Labor Availability]
    B --> C[Decide Mechanization Level]
    C --> D[Calculate Gang Balance]
    D --> E[Optimize Employment & Productivity]
    E --> F[Implement & Monitor Social Impact]

Summary: Use IRC SP 24's equipment and labor output tables to balance mechanization and manual work, enhancing social desirability by maximizing local employment under safe and fair conditions.

IRC SP 24: Norms for Calculating Usage Charges of Machines

Key Components of Usage Charges (Clause 7.3.1)

1. Ownership Charges

   • Total Investment (A): Cost of equipment + taxes + transport + erection
   • Salvage Value = 15% of A → 0.15A
   • Depreciable Amount = A - 0.15A
   • Economic Life (D): 10,000 to 15,000 working hours
   • Depreciation/hour = (A - Salvage) / Economic Life
   • Storage Charges = 1% of Depreciation/hour
   • Total Ownership Charges = Depreciation/hour + Storage Charges

2. Repair Charges (H)

   • Approx. 150% of depreciation/hour (includes maintenance, tyre replacement)

3. Running Charges

   • Fuel consumption (litres/hour) = BHP × 0.6 × 0.0067
   • Other lubricants cost = 2× lubricating oil cost (heavy machinery)
   • Operator wages = Annual wages ÷ Annual working hours

4. Overhead Charges

   • 5% of total charges per hour

Formula Summary

Example Usage Charges (Table 19 Extract)