Chapter 4 - Further properties of Soil

Question 1

What do the particles that make up soil vary significantly in?

Answer 1

Size

Question 2

What is a good way of classifying the soil being dealt with?

Answer 2

By looking at the size of particles

Question 3

What does ‘PSD’ stand for?

Answer 3

Particle Size Distribution

Question 4

What is the particle size distribution?

Answer 4

A graphical way of representing the range of particle sizes present in the soil.

Question 5

How is a PSD plot obtained?

Answer 5

Sample of the soil is washed through a series of sieves, each one progressively having smaller holes, resulting in the smaller particles falling to the bottom and the larger particles staying at the top

Question 6

What does Dxx stand for?

Answer 6

The particles size of which percentage the soil is smaller than, e.g D50 would be the particle size 50% of the particles are smaller than.

Question 7

What does the Uniformity Coeffient tell us?

Answer 7

How steep are PSD curve is

Question 8

What does a ‘well graded’ soil have?

Answer 8

Particles distributed across all sizes

Question 9

What does a ‘poorly graded’ soil have?

Answer 9

Particles that are all similar in size

Question 10

When is the term ‘uniform’ used?

Answer 10

When particles all have the same sizes

Question 11

What does the amount of void space depend on?

Answer 11

The particle size distribution and the arrangement of particles

Question 12

If the PSD has a high uniformity coefficent value, and the particles are arranged in an optimal fashion, what will occur?

Answer 12

There will be little void space and the soil will be very dense

Question 13

What is the equation for relative density, Id?

Answer 13

Emax - e / Emax - Emin

Question 14

How do we classify fine particles, such as silt and clay?

Answer 14

By using a plasticity index

Question 15

Why do clay particles ‘stick’ to each other?

Answer 15

Due to the electro-static attraction between the surfaces of clay platelets

Question 16

Do clay particles remain stuck to each other when in water?

Answer 16

Yes

Question 17

How do silt particles ‘stick’ to each other?

Answer 17

Small quantities of water hold the particles together due to surface tension forces

Question 18

What does the term ‘plastic’ mean?

Answer 18

When a soil can be deformed and keep its shape and does not crack when deformed

Question 19

What is the liquid limit, WL?

Answer 19

Boundary in terms of water content between ‘plastic’ behaviour and ‘liquid’ behaviour

Question 20

What is the plastic limit, Wp?

Answer 20

The boundary in terms of water content between ‘plastic’ and ‘brittle’ behaviour.

Question 21

How do you determine the liquid limit of clay?

Answer 21

Find the water content at which a metal cone will penetrate to a certain depth into a sample of the clay ‘The fall cone test’

Question 22

How do you determine the plastic limit of clay?

Answer 22

Roll a thread of the clay under your finger tips, the water content of the clay when it cracks is defined as the plastic limit. D = 3mm