Soil mechanics

Question 1

Mechanical properties of soil largely depend on….

Answer 1

grain size
mineralogy
water content

Question 2

Shear strength

Answer 2

Ability to resist shear

Question 3

Consistency

Answer 3

Strength which hold soils together

Question 4

Consolidation

Answer 4

decrease in volume under stress

Question 5

Fluids cannot resist…..

Answer 5

shear at rest

Question 6

High shear stresses occur in minerals….

Answer 6

with high shear strength

Question 7

Soil has mixed properties because….

Answer 7

mix of water (can’t resist) + solid (can resist)

Question 8

2 components of stress in soil

Answer 8

soil skeleton

pore water

Question 9

Effective stress =

Answer 9

total stress - pore fluid pressure

Question 10

Cohesion

Answer 10

point where failure crosses y axis

Question 11

Consistency dependent on….

Answer 11

Water content

Question 12

Clays can be described as…

Answer 12

• solid
• semi-plastic
• plastic
• liquid

Question 13

Plasticity index =

Answer 13

Liquid limit - plastic limit

Question 14

Activity =

Answer 14

plasticity index / % clay minerals

greater A - more plastic

Question 15

Primary consolidation involves…

Answer 15

expulsion of water
considerable and fast
progress until PWP = 0

Question 16

Secondary consolidation involves…

Answer 16

restructuring

small and slow

Question 17

If particles loosely packed…

Answer 17

compression will occur

Question 18

If particles already tightly packed…

Answer 18

shear -> dilation

Question 19

Dilation/compression leads to

Answer 19

soil reaching critical state

Question 20

In critical state…

Answer 20

continued deformation without change in V or stress

Question 21

Loose packed soils show gradual….

Answer 21

increase in shear stress until they reach critical state

Question 22

At critical state the rock is….

Answer 22

stable

Question 23

Densely packed soils reach a..

Answer 23

peak strength

up to this dilation increases at a rapid rate

Question 24

Beyond peak strength

Answer 24

any increase in dilation = lowered strength

Question 25

Between Peak strength and critical state is dangerous because…

Answer 25

strength falls towards critical state as strain increases