Class: Senior Secondary School 1 (SS 1)
Term: 2nd Term
Week: 1
Age: 15 years
Duration: 45 minutes
Subject: Block Laying, Brick Laying and Concrete Work
Curriculum Theme: Entrepreneurship (Trade Subjects)
Previous Lesson: .
Topic: EXCAVATION OF TRENCHES TIMBERING
Subject Matter: timbering to trenches, types of timbering, soil support methods for trenches

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:

Define timbering as applied to trenches.
State the importance of timbering in trench excavation.
List different types of timbering methods.
Explain various soil support methods for trenches.

Affective Domain:

Appreciate the safety measures involved in trench excavation.
Develop an interest in safe construction practices.
Recognize the need for proper support systems in unstable soil conditions.

Psychomotor Domain:

Draw simple diagrams of timbering methods.
Identify appropriate timbering methods for different soil types.
Demonstrate how to select suitable materials for timbering.

Collaborate with peers to discuss safety in excavation.
Understand the collective responsibility for workplace safety.
Communicate ideas on effective trench support systems.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Senior Secondary School (Trade Subjects)
State Unified Scheme of Work for Block Laying, Brick Laying and Concrete Work (SS 1)
Building Construction for Senior Secondary Schools by J.O. Oyenuga

Instructional Materials

The teacher will teach this lesson with the aid of:

Timber samples
Charts showing different timbering methods
Drawings of trench excavations and timbering installations
Whiteboard and markers

Rationale for the Lesson

This lesson helps pupils understand how to make excavation trenches safe for workers. It teaches them methods to prevent trench collapses, which is important for preventing accidents and ensuring the stability of construction foundations. Understanding these techniques is a fundamental skill for anyone involved in building work.

Prerequisite/Previous Knowledge

Pupils should have basic knowledge of excavation, different types of soil, and the general principles of building construction.

Lesson Content/Board Summary

EXCAVATION OF TRENCHES TIMBERING

What is Timbering to Trenches?

Timbering to trenches refers to the temporary support system installed in excavated trenches to prevent the collapse of the trench walls. It uses timber or other materials to hold the soil in place, ensuring the safety of workers and the stability of the excavation.

Importance of Timbering in Trenches

The following are reasons why timbering is important in trenches:

It prevents the collapse of trench walls, protecting workers from injury or death.
It maintains the shape and dimensions of the trench, which is important for the foundation work.
It allows workers to work safely and efficiently within the trench.
It prevents damage to nearby structures or utilities due to ground movement.

Types of Timbering Methods

The type of timbering used depends on the depth of the trench, the type of soil, and the duration of the excavation. Common types include:

Vertical Sheeting: Used in firm soils for shallow to medium depths. Vertical planks (sheeting) are driven into the ground along the trench sides and supported by horizontal members (walings) and struts.
Horizontal Sheeting: Suitable for trenches in loose or unstable soils. Horizontal planks are placed against the trench walls and supported by vertical poling boards, walings, and struts.
Box Sheeting: Employed in very loose or waterlogged soils. It involves a complete box-like structure of timber to fully enclose and support the trench area.
Runners: A method where long, sharp-edged planks (runners) are driven ahead of the excavation, providing continuous support as the trench deepens. Used in soft, unstable, or water-bearing ground.

Soil Support Methods for Trenches

Soil support methods for trenches primarily involve various forms of timbering or shoring. These methods aim to counteract the lateral pressure exerted by the soil. The choice of method depends on the soil stability, moisture content, and trench depth.

Key components used in soil support include:

Sheeting/Poling Boards: Vertical or horizontal planks that bear directly against the soil.
Walings: Horizontal members placed against the sheeting to distribute pressure.
Struts: Horizontal compression members that span across the trench, bracing the walings on opposite sides.
Braces: Diagonal supports used in deeper excavations.

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher greets the pupils and reviews the previous lesson briefly. The teacher then asks pupils about the potential dangers of digging deep holes in the ground and how these dangers can be prevented. This leads into the topic of trench safety and support.
Pupils’ Activity: Pupils respond to questions and share their ideas on trench safety.
Learning Point: Pupils recall prior knowledge and are introduced to the lesson topic.

Step 2: Explanation of Timbering to Trenches

Time: 7 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines timbering to trenches, explaining its purpose as a temporary support system. The teacher shows drawings of simple timbering setups and explains why it is used in excavation.
Pupils’ Activity: Pupils listen attentively, ask questions for clarification, and take notes.
Learning Point: Pupils understand the meaning and basic purpose of timbering.

Step 3: Importance of Timbering in Trenches

Time: 7 minutes
Teaching Skill: Elucidation/Discussion
Teacher’s Activity: The teacher discusses with pupils the various reasons why timbering is important, emphasizing worker safety, maintaining trench dimensions, and preventing damage to surrounding areas. The teacher uses the charts to illustrate dangers of unsupported trenches.
Pupils’ Activity: Pupils contribute to the discussion, list the importance, and observe the charts.
Learning Point: Pupils understand the critical importance of timbering for safety and structural integrity.

Step 4: Types of Timbering Methods

Time: 10 minutes
Teaching Skill: Demonstration/Illustration
Teacher’s Activity: The teacher explains and demonstrates the different types of timbering methods (Vertical Sheeting, Horizontal Sheeting, Box Sheeting, Runners) using charts, drawings, and actual timber samples if available. The teacher explains which method is suitable for different soil types.
Pupils’ Activity: Pupils observe the illustrations, handle timber samples, ask questions, and draw simple diagrams of the methods in their notebooks.
Learning Point: Pupils identify and differentiate between various timbering methods and their applications.

Step 5: Soil Support Methods for Trenches

Time: 8 minutes
Teaching Skill: Explanation/Analysis
Teacher’s Activity: The teacher explains that soil support methods are essentially the components and techniques used within timbering systems to effectively support trench walls. The teacher identifies and explains the function of key components like sheeting, walings, and struts, linking them back to the types of timbering discussed.
Pupils’ Activity: Pupils listen, take notes, and relate the components to the timbering methods previously discussed.
Learning Point: Pupils understand the practical aspects and components of soil support in trenches.

Step 6: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

Define timbering as used in trench excavation.
State two reasons why timbering is important in trenches.
List three types of timbering methods.
Mention two key components used in soil support for trenches.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 7: Conclusion

Time: 3 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the importance of safety in excavation. The teacher assigns homework: “Draw and label any two types of trench timbering methods.”
Pupils’ Activity: Pupils listen to the summary and copy the homework assignment.
Learning Point: Pupils review the lesson and prepare for independent practice.

Lesson Keywords

Timbering – The temporary support system used in trenches to prevent collapse.
Trenches – Long, narrow excavations in the ground, typically for foundations or pipes.
Excavation – The process of digging or removing earth.
Sheeting – Boards or planks placed against trench walls for support.
Walings – Horizontal members supporting sheeting and braced by struts.
Struts – Horizontal compression members used to brace walings across a trench.
Soil Support – Methods and components used to stabilize trench walls.

Differentiation

For visual learners, the teacher will use more charts and diagrams. For kinesthetic learners, the teacher will encourage handling timber samples and drawing the methods. Slower learners will be given simplified diagrams and more direct questions, while advanced learners will be encouraged to research specific local regulations for trenching and shoring.

Note for teachers using this lesson plan

Teachers should emphasize the practical application and safety aspects of timbering. Where possible, relate the concepts to local construction practices. Encourage pupils to ask questions about real-life scenarios. Safety should be a continuous theme throughout the lesson.