1. Introduction😲

1.1. Background Information and Context

Soil is the loose surface material that covers most land. It consists of inorganic particles and organic matter. They vary greatly in their chemical and physical properties. (Agriculture Victoria, 2021)

Soil provides structural support to buildings that are used for all manners of things. Supports are inserted into soil to stabilise buildings and the right type of soil is important to make a strong foundation.

1.2 Specific Topic of Research and Importance

All structures in the world are built on soil. Thus, understanding soil is important. Shear and tensile strength of soils are part of what we need to know about soil before construction and are what this study focuses on.

Soil is common and is found in most parts of the world as it forms on the surface of the land. Humans have been constructing shelters on or by using soil in early times. This study will give us a better understanding of soil strengths, by testing the shear and tensile strength of soils. By knowing this information, buildings will be able to withstand more natural disasters and erosion.

1.3 Past Attempts

There was an investigation conducted by SST students Sim et al. (2021) about the type of soil affecting soil erosion and soil shear strength. Their investigation was done for their Science Talent Development Programme where the 3 students participated in Kumamoto Kita High School’s Science Research Fair. They conducted Shear Strength and Erosion Resistance experiments.

In a study by Fang et al. (1970) from the Department of Civil Engineering, Lehigh University, they discovered a new method for the determination of tensile strength of soils, called the double punch test. The double punch test is a simple and easy test to perform, and only steel punches are needed for the test. Based on the plasticity theory, they developed a simple equation for computing the tensile strength of soils.

Unlike the previous experiments stated above, the relationship that we are looking into is the relationship between the soil's moisture and the soil's strength, which is, in other words, how the water content of the soil affects the tensile and shear strength of the soil. We will change the moisture of the soils and compare the moisture values after measuring them. Then, we will be able to determine whether the moisture of the soil is affecting the shear and tensile strengths. In conclusion, we wish to find out how different water contents in the soils affect the readings of both tensile and shear strength tests.

1.4.2 Research Questions

Our research question is as follows:

What are the soil strengths for soils with different moisture levels?

1.4.3 Research Hypotheses

We decided to test the following hypothesis:

H1: We hypothesise that soils with a higher moisture level will have greater shear strength.

H2: We hypothesise that soils with a higher moisture level will have greater tensile strength.

1.4.3.1 Independent variable

Moisture level of the soil

1.4.3.2 Dependent variable

Shear and Tensile strength of the soils

1.4.3.3 Controlled variables

(a) Mass of soil

(b) Same hand held shear vane device

(c) Same location of experiment