GSB Road Construction SOP

Standard Operating Procedure for Granular Sub Base (GSB) road construction, ensuring stability, durability, and compliance with industry standards and IS Codes.

Duration: 5-7 days Team: 8-12 workers Risk Level: Medium

1. Purpose

To define a structured procedure for Granular Sub Base (GSB) road construction, ensuring stability, durability, and compliance with industry standards and IS Codes.

2. Scope

This SOP applies to all GSB road construction projects, covering material selection, preparation, laying, compaction, quality control, and testing procedures as per relevant IS codes.

3. Responsibilities

Project Manager

Ensures compliance with specifications, IS codes, and project timelines

Site Engineer

Monitors execution & verifies compliance with drawings

Supervisor

Ensures availability of materials, tools & workforce coordination

Operators & Workers

Perform material spreading, grading, and compaction

Quality Inspector

Checks material quality, layer thickness, and compaction density

Safety Officer

Ensures all safety measures are followed at the construction site

4. Materials and Tools Required

Granular Materials

Aggregates, crushed stone, sand, gravel as per IS 383:2016

Water

For compaction as per IS 456:2000

Binding Material

If required for stabilization

Heavy Equipment

Excavator, loader, dumpers, grader

Water Tanker

For moisture control during compaction

Compaction Equipment

Vibratory or static roller

Measuring Tools

Tape, level indicators, survey tools

Testing Equipment

Core cutter, sand replacement apparatus, moisture meter

5. Procedure

1
Pre-Work Preparation
Survey and Planning:
  • Review approved drawings and plans for GSB layer specifications
  • Study site conditions including slopes, drainage patterns, and soil types
  • Identify and mark reference levels for GSB layer using survey tools
  • Ensure proper drainage planning to prevent water accumulation
  • Create work schedule with equipment and material delivery timelines
Material Verification:
  • Check availability of approved granular materials as per specifications
  • Verify material compliance with IS 383:2016 gradation requirements
  • Ensure materials are free from organic matter and deleterious substances
  • Check for adequate material quantities to avoid work stoppages
  • Conduct preliminary material testing if required
Equipment Inspection:
  • Ensure availability of all required equipment (graders, rollers, water tankers)
  • Check equipment functionality and maintenance status
  • Verify measuring and testing tools are calibrated and operational
  • Arrange for backup equipment in case of breakdowns
Safety Measures:
  • Brief workers on safety protocols and PPE requirements
  • Install safety signage and barricades around the work area
  • Ensure first aid kit and emergency communication devices are available
  • Create clear communication channels between equipment operators and ground crew
2
Subgrade Preparation
Subgrade Cleaning:
  • Remove all vegetation, roots, debris, and foreign materials from the subgrade
  • Ensure surface is clean and free from loose soil and organic matter
  • Level any depressions or high spots to achieve uniform surface
  • Check for soft areas and treat them as per engineer's instructions
Subgrade Compaction:
  • Compact the subgrade using appropriate rollers (8-10 ton capacity)
  • Adjust moisture content to achieve optimal compaction (±2% of OMC)
  • Conduct field density tests every 500 sq.m as per IS 2720 Part 28/29
  • Ensure minimum 97% compaction of Modified Proctor Density (MDD)
  • Re-compact areas failing density tests until requirements are met
Subgrade Profiling:
  • Check levels at regular intervals (typically 10m) to verify subgrade profile
  • Ensure proper camber/crossfall (2-2.5%) for effective drainage
  • Verify longitudinal gradient as per design drawings
  • Document subgrade acceptance before proceeding with GSB work
Drainage Provisions:
  • Create side drains if required as per design specifications
  • Install cross drainage structures where necessary
  • Ensure drainage paths remain unobstructed during construction
  • Test water runoff pattern to confirm proper drainage
3
GSB Material Preparation and Transportation
Material Selection:
  • Ensure aggregates meet gradation requirements as per IS 2386
  • Check aggregate quality for strength, durability, and cleanliness
  • Verify proper blending of different fractions if required
  • Conduct sieve analysis to confirm particle size distribution
Material Preparation:
  • Separate materials into stockpiles based on size fractions if needed
  • Ensure proper moisture conditioning at source or stockpile
  • Cover stockpiles during rainy weather to prevent excessive moisture
  • Measure moisture content before transportation to site
Transportation:
  • Transport material using dumpers from source to the site
  • Cover loads during transportation to prevent dust and material loss
  • Plan delivery schedule to maintain continuous work flow
  • Ensure proper access routes for material delivery
On-Site Storage:
  • Store material in designated stockpiles for easy access
  • Prevent contamination by keeping stockpiles on clean, firm surfaces
  • Maintain separate stockpiles for different material types/sources
  • Implement proper drainage around stockpile areas
4
GSB Laying and Spreading
Setting Reference Guides:
  • Install level controls like string lines or side forms
  • Mark thickness references at regular intervals
  • Establish spreading patterns to ensure uniform coverage
  • Verify alignment with design drawings before starting
Material Dumping:
  • Dump material in predetermined patterns with appropriate spacing
  • Avoid material segregation during dumping process
  • Ensure dumping doesn't damage prepared subgrade
  • Control dump heights to prevent material segregation
Material Spreading:
  • Spread the GSB material evenly using grader or dozers
  • Maintain consistent layer thickness as per design (typically 150-225mm)
  • Avoid segregation during spreading operations
  • Verify thickness at frequent intervals using level checks
  • Correct any uneven spreading immediately
Profile Shaping:
  • Shape material to required cross-section profile (camber/super-elevation)
  • Ensure proper longitudinal grade as per design
  • Check levels every 10m along length and at edges
  • Verify camber/crossfall (typically 2-2.5%) for drainage
5
Moisture Adjustment and Compaction
Moisture Content Adjustment:
  • Check existing moisture content of spread material
  • Add water using sprinkler tanker to achieve OMC (±2%)
  • Ensure uniform water distribution throughout the layer
  • Allow time for water to permeate through material if needed
  • Mix thoroughly using grader/rotavator to ensure uniform moisture
Initial Compaction:
  • Begin compaction immediately after moisture adjustment
  • Use vibratory roller (8-10 ton) for initial passes
  • Start compaction from edges and progress toward center
  • Ensure minimum 4-6 passes over each area
  • Maintain uniform roller speed (2-4 km/hr)
Final Compaction:
  • Complete compaction with pneumatic/smooth wheeled roller
  • Continue until no visible movement under roller
  • Verify density using field testing methods (core cutter/sand replacement)
  • Ensure minimum 98% of MDD as per IS 2720
  • Re-compact areas failing density requirements
Special Area Treatment:
  • Use plate compactors for areas inaccessible to rollers
  • Provide extra attention to joints between days' work
  • Ensure proper compaction near structures and edges
  • Verify transitions between different sections are smooth

6. Quality Checks and Tests

Material Gradation

Sieve analysis as per IS 2386 to verify material gradation requirements

Layer Thickness

Check thickness at min. 3 locations per 500 sq.m (tolerance: ±10mm)

Compaction Tests

Field density tests (minimum 98% MDD) at 1 test per 500 sq.m

Moisture Content

Verify moisture content (OMC ±2%) using rapid moisture meter

Surface Regularity

Maximum 8mm deviation under 3m straight edge

Camber & Grade

Check crossfall (2-2.5%) and longitudinal grade as per design

Aggregate Quality

Impact, abrasion, and flakiness index tests as per IS standards

Drainage Check

Verify drainage pattern after completion using water flow tests

7. Safety Measures

PPE Usage

Safety boots, gloves, helmets, and high-visibility vests for all personnel

Site Barricading

Ensure proper barricading and warning signs around work areas

Traffic Management

Control traffic movement during material transportation and construction

Equipment Safety

Maintain safe distance between working equipment and personnel

First Aid

First aid kits and trained personnel available on site at all times

Worker Coordination

Clear communication protocols between equipment operators and ground staff

Equipment Inspection

Daily inspection of all equipment before operation

Heat Stress Prevention

Regular hydration breaks and shade provisions during hot weather

8. Troubleshooting Common Issues

Segregation of Material

Problem: Separation of coarse and fine aggregates during transportation or spreading.

Solution: Remix material using grader or dozer, control dump heights during unloading, ensure proper moisture content before spreading, and adopt proper spreading techniques to minimize segregation.

Inadequate Compaction

Problem: Areas failing density tests despite multiple roller passes.

Solution: Adjust moisture content to OMC, increase number of roller passes, reduce layer thickness if too thick, check roller functionality and vibration settings, consider different roller types for problematic materials.

Surface Undulations

Problem: Uneven surface with depressions or high spots after compaction.

Solution: Scarify affected areas, add or remove material as needed, reshape to proper profile, and recompact. Ensure proper control of grader operations and frequent level checks during spreading.

Moisture Issues

Problem: Material too dry (dusty) or too wet (pumping).

Solution: For dry material, add water in controlled amounts with uniform distribution. For wet material, allow drying time with occasional turning, or consider adding dry material to balance moisture content.

9. Documentation and Approval

Maintain records of material testing reports and approvals
Document compaction test results and layer thickness measurements
Record daily progress, weather conditions, and equipment utilized
Take photographic evidence at each stage of construction
Obtain final approval from quality control team before proceeding to next layer
Prepare as-built drawing showing actual construction details
Maintain a comprehensive site register for future reference

10. References and Standards

IS 383:2016 - Specification for coarse and fine aggregates
IS 2386 (Parts 1-8) - Methods of test for aggregates for concrete
IS 2720 (Part 8) - Determination of water content-dry density relation
IS 2720 (Part 28) - Determination of dry density by sand replacement method
IS 2720 (Part 29) - Determination of dry density by core cutter method
IRC:SP:20 - Rural Roads Manual
MORTH 5th Revision - Specifications for Road and Bridge Works
IRC:36 - Recommended Practice for Construction of Earth Embankments

11. Pro Tips

Moisture Control

Always maintain OMC (Optimal Moisture Content) for best compaction results

Weather Consideration

Avoid GSB laying during heavy rain to prevent material washout

Layer Thickness

Compacting in thinner layers (max 150mm) achieves better density than single thick layer

Rolling Pattern

Start compaction from edges and move toward center for uniform density

Level Control

Install reference pegs at 10m intervals for better thickness and level control

Material Storage

Store GSB material on elevated platforms during monsoon season

Material Delivery

Plan material deliveries to match daily laying capacity to avoid stockpiling

Compaction Speed

Maintain consistent roller speed (2-4 km/hr) for effective compaction

12. Conclusion

By following this Standard Operating Procedure, GSB road construction can be executed efficiently, ensuring stability, durability, and compliance with IS standards. Proper execution and strict adherence to safety measures will result in strong, stable, and durable road foundations. The GSB layer provides essential support for subsequent pavement layers and contributes significantly to the overall performance and longevity of the road structure. Regular quality checks and documentation will help maintain high standards throughout the construction process, resulting in roads that provide reliable service throughout the project's operational life.

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