Earthmoving and Material Handling

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:

The Bulldozer Work Cycle

The production cycle of a bulldozer consists of four distinct phases:

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:

Table 1: Typical traction coefficients (dry soil)

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

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.

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:

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.

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:

Table 3: Conversion between states

Bulldozer Grading Techniques

Rough Grading

Rough grading involves moving large volumes of material to get close to the final grades. The techniques used are:

Fine Grading

Fine grading (or precision grading) aims to achieve the final surface with a tolerance of ± 20 mm. Techniques:

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

Grading Using Grade Stakes

The traditional method uses grade stakes with colour markings:

Procedure:

Material Handling

Types of Materials

The bulldozer operator must know the characteristics of the materials being handled:

Material Losses

Side losses are the material that escapes off the sides of the blade during transport. They depend on:

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

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:

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:

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:

Safety Procedures for Earthwork

Before Starting Work

During Work

After Work

Production Estimation

Factors Influencing Production

The hourly production of a bulldozer (in m³/h) depends on:

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

Blade Maintenance and Inspection

Blade Components

The bulldozer blade includes:

Daily Inspection

Cutting Edge Wear

Cutting edge wear directly affects performance:

Common Pitfalls to Avoid

Summary

Review Questions

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!