CIVL451 Construction Earthmoving Materials and Equipment Notes

The Construction Industry

• Nature of the Discipline: Construction is widely recognized as a combination of both art and science.

• Construction Contractors: These are companies and individuals engaged in the business of construction. They are termed "contractors" because they operate under a legal contract with the owner.

The Construction Process

Construction can be accomplished through several organizational methods. The delivery and management of a project are typically categorized by the following arrangements:

• Construction Employing an Owner Construction Force: The owner uses their own internal staff and labor to perform the work (Figure 1-5).

• Owner Management of Construction: The owner manages the project directly, potentially employing internal forces, external contractors, or both (Figure 1-6).

• Construction by a General Contractor: Also known as a Prime Contractor. The owner contracts with a single firm, which then manages subcontractors and a contractor workforce. A design firm usually works separately for the owner providing inspection (Figure 1-7).

• Design/Build (Turnkey) Contract: The owner contracts with a single firm responsible for both the design and construction force. The firm may also manage subcontractors (Figure 1-8).

• Construction Management Contract: The owner contracts with a design firm and a construction manager. The construction manager acts as the owner's agent, maintaining a management relation with various construction firms while the owner maintains the contractual relation (Figure 1-9).

Reducing Construction Costs

To maximize efficiency and minimize expenses, companies focus on several strategic areas:

• Implementing good work planning.

• Carefully selecting and training both workers and managers.

• Efficiently scheduling labor, materials, and equipment.

• Properly organizing work flows.

• Utilizing labor-saving techniques, such as prefabrication and preassembly.

• Minimizing the need for rework through timely quality control.

• Preventing accidents by maintaining rigorous safety procedures.

Material on Industry Financials and Case Studies

• Leighton Holdings Example: Historical data from October 1989 to October 1998 shows the return on a $\$10,000$ investment. By September 1999, the stock value reached approximately $\$200,000$, outperforming the general market and industry sector.

• Worley Share Prices: Data shows significant volatility in construction and engineering services:

  • July 2003: Low of $\$1.59$.

  • July 2007/08: High of $\$54.19$.

  • July 2016: Prices dropped significantly, reaching around $\$14.16$ in late 2013 and declining further.

• Industry Volatility Caution: A construction company case study highlights a firm that lost money even during the "boom years" (reflected in a $\$10,000$ investment dropping toward $\$2,000$ between 1990 and 2000), emphasizing the importance of management over market conditions.

Introduction to Earthmoving

• Definition: Earthmoving is the process of moving soil or rock from one location to another and processing it to meet specific construction requirements involving location, elevation, density, and moisture content.

• Equipment Selection: Choosing the correct equipment is a major influence on the efficiency and profitability of an operation.

• Basic Production Formula: The fundamental relationship for estimating production for all earthmoving equipment is: $\text{Hourly Production} = \text{Volume per Cycle} \times \text{Cycles per Hour}$

• Factored Hourly Production: $\text{Hourly Production} = \frac{\text{Volume per Cycle} \times 60}{\text{Cycle Time (Minutes)}} \times \text{Efficiency Factor}$

Job Efficiency Factors

Efficiency is determined by Management Conditions and Job Conditions as shown in Table 2-1:

• Management Conditions: Refers to the skill, training, and motivation of workers; selection and maintenance of equipment; and quality of planning, layout, and supervision.

• Job Conditions: Refers to the physical conditions, such as topography, work dimensions, surface and weather conditions, and specification requirements.

• Efficiency Table (Representative Values):

  • Excellent Management/Excellent Job: $0.84$

  • Good Management/Good Job: $0.75$

  • Poor Management/Poor Job: $0.52$

• Other Factors: Experience, attitude, judgment of management, equipment failures, and the availability of spare parts.

Soil Identification and Classification

Soil types are identified by grain size ($F$, diameter):

• Gravel: $6\,\text{mm}$ to $76\,\text{mm}$. Particles larger than $76\,\text{mm}$ are termed "Cobbles."

• Sand: $0.074\,\text{mm}$ ($200$ sieve) to $6\,\text{mm}$.

• Silt: $0.002\,\text{mm}$ to $0.074\,\text{mm}$.

• Clay: Less than $0.002\,\text{mm}$.

• Organic Soils: Contain partially decomposed vegetable matter.

Moisture Content and Atterberg Limits

• Moisture Content Formula: $\text{Moisture Content (\%)} = \frac{\text{Moist Wt} - \text{Dry Wt}}{\text{Dry Wt}} \times 100$

  • Example: A sample weighs $120\,\text{kg}$ natural and $100\,\text{kg}$ dry. The moisture content is $(\frac{120-100}{100}) \times 100 = 20\%$.

• Liquid Limit (LL): The moisture content at which soil starts to flow under a standard shaking test.

• Plastic Limit (PL): The moisture content at which soil begins to crumble when rolled into a $3\,\text{mm}$ diameter thread.

• Plasticity Index (PI): The difference between the liquid and plastic limits ($PI = LL - PL$), representing the range where soil remains plastic.

Field Investigation (Unified System)

1. Remove particles larger than $76\,\text{mm}$.

2. Separate visually at the No. 200 sieve ($0.074\,\text{mm}$; smallest particle visible to the naked eye).

3. If >50\% by weight is larger than No. 200, it is Coarse-Grained.

4. Divide coarse particles into those >6\,\text{mm} and <6\,\text{mm}.

5. If >50\% of coarse fraction is >6\,\text{mm}, it is Gravel; otherwise, it is Sand.

6. If <10\% is smaller than No. 200, assign second letter based on grading ($W$ for well-graded, $P$ for poorly graded).

7. If >10\% is smaller than No. 200, assign second letter based on plasticity ($L$ for low, $H$ for high).

8. If Fine-Grained (>50\% passes No. 200), use dry strength and shaking tests.

General Soil and Rock Characteristics

• Soil Trafficability: The ability of soil to support vehicle weight under repeated traffic.

• Soil Loadability: A measure of difficulty in excavating and loading the material.

• Unified System Suitability (Table 2-4):

  • GW (Well-graded gravel): Excellent drainage, excellent workability, good subgrade suitability.

  • CH (High-plasticity clay): Very poor drainage, poor workability, poor to fair subgrade.

  • Pt (Peat): Unsuitable for construction use.

Soil Volume Change Characteristics

Material exists in three states during earthmoving:

• Bank: Natural state before disturbance ("in situ"). Measured in bank cubic metres (BCM).

• Loose: Excavated or loaded state. Measured in loose cubic metres (LCM).

• Compacted: State after compaction. Measured in compacted cubic metres (CCM).

Swell and Shrinkage Formulas

• Swell: The increase in volume when excavated. $\text{Swell (\%)} = (\frac{\text{Bank Density}}{\text{Loose Density}} - 1) \times 100$

• Shrinkage: The decrease in volume after compaction. $\text{Shrinkage (\%)} = (1 - \frac{\text{Bank Density}}{\text{Compacted Density}}) \times 100$

• Load Factor: Used to convert loose volume to bank volume. $\text{Bank Volume} = \text{Loose Volume} \times \text{Load Factor}$ $\text{Load Factor} = \frac{1}{1 + \text{Swell}} = \frac{\text{Loose Density}}{\text{Bank Density}}$

• Shrinkage Factor: Used to convert bank volume to compacted volume. $\text{Compacted Volume} = \text{Bank Volume} \times \text{Shrinkage Factor}$ $\text{Shrinkage Factor} = 1 - \text{Shrinkage} = \frac{\text{Bank Density}}{\text{Compacted Density}}$

Typical Characteristics (Table 2-5)

• Common Earth: Swell $25\%$, Shrinkage $10\%$, Load Factor $0.80$, Shrinkage Factor $0.90$.

• Rock (Blasted): Swell $50\%$, Shrinkage $-30\%$ (Note: Compacted rock is less dense than in-place rock), Load Factor $0.67$, Shrinkage Factor $1.30$.

• Sand and Gravel: Swell $12\%$, Shrinkage $12\%$, Load Factor $0.89$, Shrinkage Factor $0.88$.

Spoil Banks and Piles

• Spoil Bank: A long pile created by removed excavation material.

• Angle of Repose: The angle the sides of the pile naturally form with the horizontal plane. Typical values include:

  • Clay: $35^{\circ}$

  • Sand (Dry): $25^{\circ}$

  • Sand (Moist): $37^{\circ}$

Triangular Spoil Bank Formulas

• Height ($H$): $H = \frac{B \times \tan(R)}{2}$

• Section Area ($A$): $A = 0.5 \times \text{Base Width (B)} \times \text{Pile Height (H)}$

• Volume ($V$): $V = A \times \text{Pile Length (L)}$

• Relationship: $V = \frac{L \times B^2 \times \tan(R)}{4}$

Conical Spoil Pile Formulas

• Height ($H$): $H = \frac{D \times \tan(R)}{2}$

• Volume ($V$): $V = \frac{\text{Base Area} \times H}{3}$

• Diameter ($D$): $D = (\frac{7.64 \times V}{\tan(R)})^{\frac{1}{3}}$

Estimating Earthwork Volume

Operations are divided into three principal categories:

1. Pit Excavations: Small, deep excavations used for basements or foundations.

2. Trench Excavation: Linear excavations required for utility lines.

3. Large Areas: General grading or excavation of relative large construction sites.

The Mass Diagram

• Definition: A continuous curve representing the accumulated volume of earthwork plotted against the linear profile of a roadway or airfield.

• Purpose: Used to select an alignment that minimizes earthwork by showing "Cut" (excavation) and "Fill" (embankment) requirements.

• Average Haul Distance: Within a balanced section, the approximate average haul distance is the length of a horizontal line midway between the balance line and the peak or trough of the section.