Do “mass” and “weight” mean the same thing in soil mechanics? Is void ratio presented as percentage (for example, e = 60%) or ratio (e = 0.6)?

Assignment 1(A) Soil Mechanics

Theoretical question sections:

1. Do “mass” and “weight” mean the same thing in soil mechanics?
2. Is void ratio presented as percentage (for example, e = 60%) or ratio (e = 0.6)?
3. The relative density seems to be mostly used for sand. What about clay?
4. If the soil is partially saturated, let’s say S = 0.75, what shall we call it?
5. Do the dry density and density of solids mean the same thing?
6. Why do we need to know the unit weight, isn’t just the soil density enough?
7. Can all soils have water content more than 100% or is it only possible for plastic soils?
8. Why is the range of Gs values very narrow?

Complex Problem-solving question sections:

Let’s apply your knowledge of soil constituents to determine the basic properties of soil from the project site. We will refer to the data from Table as an example.

1. There are too many variables in the table below. Name the three most important parameters and give your engineering judgment (qualitative and quantitative) based on your selection?
2. Which soil type will cause problems if the soil is not treated when the project continues and why?
3. What type of problems will happen from your answer in (2) and what topics in EAG245 will address this issue?
4. As an engineer responsible for the project, suggest several options that can be carried out to improve the situations in (3) (with the help of sketches)
5. Based on the information given in table 1 for Sand (Pit 1), recalculate the value of:

1. Void ratio
2. Degree of saturation, and
3. Relative density

Table 1

Complex Problem-solving question sections (field application)

Soil excavated from a borrow pit at another site is being used to construct an embankment (Fig. below). The soil sample from the borrow pit has a specific gravity of 2.7 and a unit weight of 17.8 kNm⁻³. The weight of the sample was 3.5 N. The sample was then placed in an oven for 24 h at 105°C and its weight reduced to a constant value of 2.9 N. The soil at the embankment is required to be compacted to a void ratio of 0.71. If the finished volume of the embankment (Ve) is 80,000 m³, what would be the volume of the soil (Vb) excavated at the borrow area? (assume the volume of solids (Vs) is equal to 1)

From the results of sieve analysis, liquid and plastic limits of soil given in Table 1:

1. Plot the grain-size distribution curve
2. Determine the uniformity coefficient (Cu)
3. By comparing the uniformity coefficient (Cu) obtained in (2) with the other soil sample which is Cu = 2.8, choose the soil that has a better drainage condition and explain the reason.
4. Classify the soil in Table 2 by the AASHTO classification system.

Table 2: Results of a sieve analysis, liquid and plastic limits of soil