Lecture 13

Question 1

excavation support systems are used to

Answer 1

minimize the excavation area
to keep the sides of deep excavations stable
to ensure that movements will not cause damage to neighboring structures or to utilities in the surrounding ground
for soil stability to keep worksers safe

Question 2

what are the causes of soil instability

Answer 2

1- increase in depth of a cut
2- increase in the water content in the soil
3- hydrostatic pressure in ground cracks near the walls of excavation
4-the weight of the excavated material equipement and buildings adjacent to the excavation
5 - shock and vibration from machinery traffic or blasting
6 - soil frost action

Question 3

what is soil frost action

Answer 3

it is where the soil freezes and expands due to low temperatures. when soil freezes ice lenses can form in the soil causing it to expand and push against the surrounding soil particles

Question 4

if the construction site is sufficiently larger than the area to be covered by the building….

Answer 4

the edges of the excavation can be sloped back or bench at a low enoough angle that soil will not slide back into the hole

Question 5

the maximum possible slope of soil not cause instability is called the

Answer 5

angle of repose

Question 6

the angle of repose can be steep for ____ or shallow for ___

Answer 6

steep for cohesive soils like stiff clays or shallower for frictional soils like sand and gravel

Question 7

on constricted sites the soil must be held back by….

Answer 7

some kind of excavation support capable of resisting the pressures of earth and groundwater

Question 8

what