Geotech

Question 1

What is a Residual soil

Answer 1

a soil that has remained at the place of foramtion

Question 2

What is a gap graded soil?

Answer 2

on a graduation curve a gap or missing range of particle sizes, shown as a straight line

Question 3

Soil can be derived from

Answer 3

Igneous Rock
Sedimentary Rocks
Metamorphic Rocks

Question 4

For the same volume - What soil particles has more surface area? large or small particles or is it equal ?

Answer 4

small particles of soil

When a substance is in smaller pieces, more of the particles that make up that substance are exposed on the surface, so the surface area is large. When the substance is in larger pieces, not as many of the particles are exposed to the surface, so the surface area is smaller in this case.

Question 5

Hydrometer Analysis is used for ?

Answer 5

to provide more info grain sized distribution and gradient for fine grains only

Question 6

What happens to soil strength during compaction?

Answer 6

the soil gets stronger

** add more

Question 7

What happens to soil permiability during compaction?

Answer 7

compaction reduces permiability

Question 8

what is responsible for the slow of water in soils?

Answer 8

total head

Question 9

what is liquefaction? and what causes it?

Answer 9

sudden shit it soil that make it appear like quiksand/liquid

Dry granular soils tend to densify under vibration,

when the granular soil is saturated the densification tendency generates excess pore water pressure

The excess pore water pressure reduces the shear strength of soil;

failure occurs when the shear stress exceeds the shear strength of soil

Question 10

what three things are needed for the process of liquefaction to take place?

Answer 10

earthquake
sand
Ground water table at certain height

Question 11

what is a CH soil?

Answer 11

high plasticity Clay

Question 12

What is SP soil?

Answer 12

poorly grated sand

Question 13

clays are formed from two fundamental building blocks, what are those two blocks ?

Answer 13

X

Question 14

Resistivity (Conductivity) of Soil and rock is affected by what?

Answer 14

Porosity , moisture content, Salinity of pore water and grain size distribution

Question 15

What is Soil Group Index? how to you find it for a soil?

Answer 15

Group index helps classify the quality of the soil - this goes along with the ASSHTO classification Number ( i. A6 - this is found with the table - however sometimes group index is needed to find the classification)

solving the Group index is an equation on page 125

Question 16

The lateral stain required to fully mobilize the soil passive pressure is larger or smaller than the lateral strain to fully mobilize the soil active pressure?

Answer 16

passive requires larger lateral stain-

The wall translation ( or strain required to achieve the passive state is TWICE that required to reach the Active state

Question 17

A footing is to be constructed in sand, the groundwater is at ground surface - the ultimate bearing capacity is based on what type of soil unit weight

Answer 17

the ultimate bearing capacity would be based on buoyant unit weight, also referred to as the effective unit weight

Effective unit weight = saturated unit weight - unit weight of water

Question 18

two identical footings are constructed in two different soil types: one in Medium Dense Sand, another in Lean Clay that is lightly over consolidated

which will have less long term settlement?

Answer 18

The Dense Sand will have less long-term settlement

because clay is subject to long term settlement

Question 19

what is long term settlement

Question 20

what is the minimum safety factor for permanent slopes?

Answer 20

1.5

Question 21

A horizontal pipe where diameter one is larger than diameter two further down the pipe

from 1 to 2 Pressure head does what?

Answer 21

Pressure head decreases from 1 to 2

Question 22

what is SPT and what does the n-value tell you?

Answer 22

The standard Penetration Test - N -Valve provides indication of the relative density of cohesionless soils

Question 23

Describe a shallow foundation?

Answer 23

foundation system in which the depth of the foundation is shallow relative to its width, usually D f /B ≤ 1. This category of foundations includes spread footings, continuous (or wall) footings, and mats.

Question 24

Describe Bearing capacity

Answer 24

is the ability of the soil to support the foundation loads without shear failure.

bearing capacity failures have the potential to cause major damage or collapse.

Question 25

Describe Settlement

Answer 25

is the tendency of soils to deform (densify) under applied loads.

Question 26

The most damaging settlements

Answer 26

differential settlements—those that are not uniform across the supported area.