Earthwork and Material Handling
Chapter Introduction
This chapter covers the essential skills related to earthwork and material handling for the bulldozer operator in the context of the Red Seal exam. You will learn cutting and filling principles, grading techniques, volume calculations, swell and shrinkage factors, as well as applicable Canadian standards. Mastering these concepts is fundamental, as they represent a significant portion of exam questions and are at the heart of the operator's daily work.
Fundamental Principles of Earthwork
Key Definitions
Earthwork is the set of operations involving the movement, excavation, filling, and grading of soils. For the bulldozer operator, this includes:
Cut (excavation): the removal of material above the desired elevation grade.
Fill: the addition of material to raise the ground to the required grade.
Grading: the operation aimed at achieving a level surface at a precise slope or elevation.
Shaping/profiling: the forming of terrain according to specific transverse and longitudinal slopes.
The Bulldozer Work Cycle
The production cycle of a bulldozer consists of four distinct phases:
14.Cutting: the blade penetrates the soil to excavate the material.
15.Hauling/Transporting: the material is pushed toward the dump point.
16.Dumping: the material is released.
17.Returning: the machine travels in reverse back to the cutting point.
Understanding this cycle is essential for estimating hourly production and optimizing efficiency.
Forces at Play and Traction
The bulldozer moves material using the tractive force generated by its tracks. The available tractive force depends on:
Engine power.
Machine weight.
The soil traction coefficient (see table below).
Rolling resistance.
Table 1: Typical traction coefficients (dry soil)
| Soil Type | Traction Coefficient |
|---|
| Dry clay | 0.90 |
| Wet clay | 0.70 |
| Dry sand | 0.30 |
| Wet sand | 0.50 |
| Compacted gravel | 0.70 |
| Crushed rock | 0.60 |
| Topsoil | 0.80 |
Rolling resistance is the force that opposes the machine's movement. It is expressed as a percentage of the machine's weight. For a track-type bulldozer, it typically ranges between 2% and 5% depending on ground conditions.
Swell and Shrinkage Factors
Swell
Swell is the increase in volume of soil when it is excavated and disturbed. This phenomenon is due to the introduction of air between particles. The swell factor is the ratio between the bank volume and the loose volume.
Formula:
Swell factor = Bank volume ÷ Loose volume
Table 2: Typical swell and shrinkage factors
| Material Type | Swell (%) | Swell Factor | Shrinkage (%) | Shrinkage Factor |
|---|
| Clay (topsoil) | 25 | 0.80 | 10 | 0.90 |
| Compact clay | 40 | 0.71 | 15 | 0.85 |
| Sand and gravel | 12 | 0.89 | 5 | 0.95 |
| Natural gravel | 15 | 0.87 | 8 | 0.92 |
| Rock (blasted) | 50 | 0.67 | 20 | 0.80 |
| Topsoil | 30 | 0.77 | 12 | 0.88 |
Shrinkage
Shrinkage is the reduction in volume of fill soil under the effect of compaction. The shrinkage factor is the ratio between the final compacted volume and the loose volume.
Formula:
Shrinkage factor = Final compacted volume ÷ Loose volume
Practical Application
Calculation example:
You need to backfill an excavation of 500 m³ (bank volume). The available material is compact clay.
43.Required loose volume = 500 m³ ÷ 0.71 = 704 m³ (volume to transport).
44.Final compacted volume = 704 m³ × 0.85 = 598 m³ (after compaction).
Common trap: Never confuse the swell factor and the shrinkage factor. The former applies during excavation, the latter during filling and compaction.
Volume Calculations
The Average End Area Method
To calculate the volume between two cross-sections, use the formula:
V = (A₁ + A₂) ÷ 2 × L
Where:
V = volume (m³)
A₁ = area of the first section (m²)
A₂ = area of the second section (m²)
L = distance between the two sections (m)
The Cross-Section Method
This method is used for cut and fill calculations along an alignment. Sections are taken at regular intervals (typically 20 m or 50 m).
Example:
A road 100 m long requires excavation. The section areas at 0 m, 50 m, and 100 m are 12 m², 18 m², and 15 m² respectively.
Volume between 0 and 50 m: (12 + 18) ÷ 2 × 50 = 750 m³
Volume between 50 and 100 m: (18 + 15) ÷ 2 × 50 = 825 m³
Total volume = 750 + 825 = 1,575 m³
The Average Surface Method
For large areas (parking lots, platforms), you can use the average surface method:
V = A × (h₁ + h₂ + h₃ + ... + hₙ) ÷ n
Where A is the total surface area and h are the cut or fill heights at the measurement points.
Volume Conversions
It is essential to correctly convert volumes according to their state:
Bank volume: material in its natural state.
Loose volume: excavated material.
Compacted volume: filled and compacted material.
Table 3: Conversion between states
| Conversion | Formula |
|---|
| Bank → Loose | Bank volume ÷ Swell factor |
| Bank → Compacted | Bank volume × (1 - Shrinkage %) |
| Loose → Bank | Loose volume × Swell factor |
| Loose → Compacted | Loose volume × Shrinkage factor |
| Compacted → Bank | Compacted volume ÷ (1 - Shrinkage %) |
| Compacted → Loose | Compacted volume ÷ Shrinkage factor |
Bulldozer Grading Techniques
Rough Grading
Rough grading involves moving large volumes of material to get close to the final grades. The techniques used are:
Full-blade cutting: the blade is loaded to maximum capacity, used for large movements.
Corner cutting: the blade is angled to concentrate the cut on one side, useful for hard soils.
Trench cutting: successive passes are made in the same trench to reduce side losses.
Fine Grading
Fine grading (or precision grading) aims to achieve the final surface with a tolerance of ± 20 mm. Techniques:
Light cutting: the blade is barely loaded, with a cutting depth of 2 to 5 cm.
Smoothing: the blade is used with a slightly angled position to spread the material.
Reverse grading: used for finishing, the blade is dragged in reverse to smooth the surface.
Slopes and Grades
Slope is expressed as a percentage (%) or in degrees (°). The conversion is:
Slope (%) = (Vertical rise ÷ Horizontal distance) × 100
Example:
A 3% slope means a rise of 3 m over 100 m of horizontal distance.
Table 4: Slope percentage / degrees conversion
| Slope (%) | Angle (°) |
|---|
| 1% | 0.57° |
| 2% | 1.15° |
| 5% | 2.86° |
| 10% | 5.71° |
| 15% | 8.53° |
| 20% | 11.31° |
| 30% | 16.70° |
| 45% | 24.23° |
Grading Using Grade Stakes
The traditional method uses grade stakes with colour markings:
Cut stake: the mark indicates the height to be cut.
Fill stake: the mark indicates the height to be filled.
Finish stake: the mark indicates the exact final level.
Procedure:
99.Identify the stakes and their markings.
100.Calculate the difference between the current ground and the target grade.
101.Perform grading passes while checking regularly.
102.Use a straightedge or level for precise finishing.
Material Handling
Types of Materials
The bulldozer operator must know the characteristics of the materials being handled:
Cohesive materials (clay, silt): adhere to each other, difficult to move, but form stable loads.
Granular materials (sand, gravel): move easily but tend to flow off the sides of the blade.
Rock: often requires pre-splitting or a rock breaker; the blade can be used to push blocks.
Organic materials (topsoil): must be removed before foundation work.
Material Losses
Side losses are the material that escapes off the sides of the blade during transport. They depend on:
Blade width.
The nature of the material.
The haul distance.
Travel speed.
Loss estimation:
For a straight blade, side losses can reach 10% to 30% of the loaded volume depending on the material and distance.
Techniques for Reducing Losses
Use an angled blade to channel the material.
Work in a trench so the walls retain the material.
Reduce travel speed for granular materials.
Use blade extensions (wing plates) if available.
Canadian Standards and Regulations
Canadian Electrical Code, Part I, Chapter V
Although the bulldozer is not directly connected to the electrical grid, the operator must know the minimum clearances to maintain near power lines. The Canadian Electrical Code, Part I, Chapter V (CSA C22.3 No. 1 standard) defines clearance distances for power transmission lines.
Minimum approach distances for mobile equipment:
| Line Voltage | Minimum Distance |
|---|
| 0 to 750 V | 3 m |
| 750 V to 75 kV | 3 m |
| 75 kV to 250 kV | 4.5 m |
| 250 kV to 550 kV | 6 m |
| Over 550 kV | 8 m |
Important rule: If the minimum distance cannot be maintained, the operator must stop work and contact the line owner.
CSA B149.1 — Natural Gas and Propane Code
During earthwork operations, the operator may encounter gas pipelines. CSA B149.1 (Natural Gas and Propane Code) requires:
Obtaining utility location plans before excavation.
Compliance with location procedures (calling the one-call service).
Immediate cessation of work in the event of damage to a pipeline.
Article 4.6.1 of CSA B149.1: Any person who damages a gas pipeline must immediately notify the pipeline owner and the appropriate authorities.
Canada Occupational Health and Safety Regulations
The Canada Occupational Health and Safety Regulations (SOR/86-304) apply to work under federal jurisdiction. The relevant sections for the bulldozer operator include:
Section 14.1: Requirements for motor vehicles and equipment.
Section 14.2: Training and competency of operators.
Section 14.3: Inspection and maintenance of equipment.
Safety Procedures for Earthwork
Before Starting Work
145.Site inspection: identify hazards (power lines, pipelines, unstable slopes).
146.Utility verification: obtain location plans and mark the locations.
147.Machine inspection: check brakes, steering, tracks, blade, and hydraulic cylinders.
148.Soil condition assessment: detect unstable or water-saturated zones.
During Work
Maintain a safe distance from slope edges and excavation edges.
Work facing the slope when working on slopes, never across.
Use the operator seat and seat belt at all times.
Signal your presence to other workers on site.
After Work
Park the machine on level ground, blade on the ground, parking brake engaged.
Shut off the engine and remove the key.
Perform daily maintenance (greasing, checking fluid levels).
Production Estimation
Factors Influencing Production
The hourly production of a bulldozer (in m³/h) depends on:
162.Blade volume (capacity in m³).
163.Blade load factor (0.6 to 1.0 depending on material).
164.Operator efficiency (0.75 to 0.95).
165.Cycle time (cut + haul + dump + return).
Production Formula
Production (m³/h) = (Blade volume × Load factor × Efficiency × 60) ÷ Cycle time (minutes)
Example:
A bulldozer with a 4.5 m³ blade, load factor of 0.85, efficiency of 0.85, and a cycle time of 1.5 minutes:
Production = (4.5 × 0.85 × 0.85 × 60) ÷ 1.5 = 195.1 m³/h (loose volume)
To obtain the bank volume: 195.1 × 0.80 = 156.1 m³/h (for a swell factor of 0.80).
Cycle Time Optimization
Reduce haul distance: plan the work to minimize travel.
Use the slope: work downhill for cutting and hauling.
Avoid sharp turns: manoeuvres increase cycle time.
Maintain a constant speed: avoid frequent stops and starts.
Blade Maintenance and Inspection
Blade Components
The bulldozer blade includes:
The moldboard (blade body).
Cutting edges (wear plates).
Corner bits (wear tips).
Wing plates (side extensions).
The hydraulic system (lift and tilt cylinders).
Daily Inspection
Check the wear on cutting edges (minimum thickness per the manufacturer's manual).
Check mounting bolts (torque specifications).
Inspect hydraulic hoses (cracks, leaks).
Check hydraulic oil level.
Check track condition and tension.
Cutting Edge Wear
Cutting edge wear directly affects performance:
Worn edge: increases the force required to penetrate the soil.
Broken edge: risk of damage to the blade and frame.
Replacement: edges should be replaced when wear reaches 50% of the original thickness.
Common Pitfalls to Avoid
199.Confusing swell and shrinkage factors: swell applies to excavation, shrinkage to fill. Read the question statement carefully.
200.Forgetting to convert volumes: a question may give a bank volume and ask for a loose volume. Always check the material state.
201.Neglecting side losses: in production calculations, losses can reduce the effective volume by 10% to 30%.
202.Ignoring electrical clearances: questions on minimum approach distances are common. Memorize the distance table according to voltage.
203.Using the wrong slope formula: percentage slope is the ratio of vertical rise to horizontal distance, not the inclined distance.
204.Forgetting the efficiency factor: in production calculations, operator efficiency and working conditions always reduce theoretical production.
205.Not accounting for return time: the full cycle time includes cutting, hauling, dumping, AND the reverse return.
206.Confusing the standards: the Canadian Electrical Code, Part I, Chapter V concerns power lines; CSA B149.1 concerns gas. Don't mix them up.
207.Forgetting location procedures: before any excavation, utility locating is mandatory. A question may cover this procedure.
208.Neglecting pre-work inspection: questions on daily blade and machine inspection are common. Know the check points.
Summary
Earthwork includes cutting, hauling, dumping, and returning. Each phase influences production.
The swell factor (bank volume ÷ loose volume) is always less than 1. The shrinkage factor (compacted volume ÷ loose volume) is also less than 1.
Volume calculations use the average end area method: V = (A₁ + A₂) ÷ 2 × L.
Slopes are expressed as percentages: Slope (%) = (Vertical rise ÷ Horizontal distance) × 100.
Side losses can reach 30% for granular materials. Use reduction techniques (trenching, angled blade).
The Canadian Electrical Code, Part I, Chapter V imposes minimum approach distances to power lines (3 m to 8 m depending on voltage).
CSA B149.1 governs work near gas pipelines. Any damage must be reported immediately.
Production is calculated: (Blade volume × Load factor × Efficiency × 60) ÷ Cycle time.
Daily inspection of the blade, tracks, and hydraulic system is mandatory before each shift.
Safety comes first: distance from slopes, working facing the slope, seat belt, and engine shutdown before any maintenance.
Review Questions
223.What is the loose volume of an 850 m³ bank excavation if the swell factor is 0.75?
Answer: 850 ÷ 0.75 = 1,133 m³.
225.A slope has a vertical rise of 4.5 m over a horizontal distance of 150 m. What is its slope in percentage?
Answer: (4.5 ÷ 150) × 100 = 3%.
227.A bulldozer has a 5.2 m³ blade, a load factor of 0.80, an efficiency of 0.85, and a cycle time of 2 minutes. What is its hourly production in loose volume?
Answer: (5.2 × 0.80 × 0.85 × 60) ÷ 2 = 106.1 m³/h.
229.What is the minimum approach distance for a 150 kV power line?
Answer: 4.5 m (according to the Canadian Electrical Code, Part I, Chapter V).
231.A fill of 600 m³ (compacted volume) is required. The available material has a shrinkage factor of 0.85. What loose volume is needed?
Answer: 600 ÷ 0.85 = 706 m³.
This chapter has provided you with the essential knowledge on earthwork and material handling for the Red Seal exam. Review the factor tables, calculation formulas, and safety standards. Practicing the calculations is essential: redo the examples and review questions until the methods are fully mastered. Good luck with your preparation!
