Site Exploration

Question 1

Aims to get more detailed information about the subsurface materials

Answer 1

site exploration

Question 2

objectives of site exploration

Answer 2

nature of soil and its stratification
disturbed and undisturbed samples for visual identification and appropriate lab tests
depth and nature of bedrock
in situ field tests
drainage conditions from and into the site
special construction problems with existing structures nearby
position of water table

Question 3

direct methods of site exploration

Answer 3

test pits or trenches
drillholes or boreholes
rock coring
soil sampling
augers
water-pressure testing
water table measurement
standard penetration test SPT
cone penetrometer test CPT
vane shear test

Question 4

Typically the site exploration
technique for horizontal structures
which only requires a shallow layer of
foundation

Answer 4

test pits or trenches

Question 5

Holes in the ground are drilled and
samples are taken. Holes commonly
reaches several meters in depth.

Answer 5

drillholes or boreholes

Question 6

accomplished with a diamond tip
rock core barrel attached to a drill
rig. The coring recovers a
cylindrical core of rock by rotating
and advancing the hollow core
barrel.

Answer 6

rock coring

Question 7

typically in percent, is the amount or length of material collected divided by the total length of the core run

Answer 7

core recovery

Question 8

a modified core recovery percentage in which the lengths of all sound rock core pieces over
100 mm in length are summed and
divided by the length of the core run. The
lengths must be measures along the
centerline of the core.

Answer 8

rock quality designation

Question 9

3 rock core tests

Answer 9

moisture content
point load index
unconfined compression test

Question 10

degree of wetness/dryness of the rock

Answer 10

moisture content

Question 11

measures the durability of a rock, can be
correlated to the compressive strength

Answer 11

point load index

Question 12

to determine the compressive
strength

Answer 12

unconfined compression test

Question 13

drilling devices/drilling bits to
excavate soil from a hole. Only used to
advance the depth of the hole.

Answer 13

augers

Question 14

sampler in conjunction
with standard penetration testing.
Hollow tube with driving shoe at the
bottom. The tube can be split
longitudinally.

Answer 14

split spoon

Question 15

also known as thin-walled tubes are usually used in obtaining undisturbed clay samples

Answer 15

Shelby tubes

Question 16

lab tests for soils

Answer 16

soil density and specific gravity
moisture content
Atterberg limits
compaction tests
permeability
soil strength

Question 17

water is pumped under pressure in drillholes
and the rate of resulting water flow is measured. The water loss coefficient, ratio of pressure to flow, indicates degree of openness of joints and the spacing of significant water conductors.

Answer 17

water-pressure testing

Question 18

holes are typically left overnight for
groundwater to stabilize and the depth of water is measured.

Answer 18

water table measurement

Question 19

indirect methods

Answer 19

geophysical methods

Question 20

These are methods where soil is not directly
sampled, although, may still be disturbed in
some manner.

Answer 20

geophysical methods

Question 21

artificial geophysical methods

Answer 21

seismic and resistivity (can be controlled to a certain degree)

Question 22

natural geophysical methods

Answer 22

gravity and magnetic methods (forces are only observed and measured, can’t be controlled)

Question 23

Uses the energy from an explosion or pounding/hammering in/on
the ground

Answer 23

seismic methods

Question 24

wave travelling along the surface

Answer 24

direct wave

Question 25

The point where refracted and direct waves come at the same time

Answer 25

critical distance

Question 26

only works if the lower layer has higher velocity than the layer above. Usually works when it is a soil upper layer and rock lower layer.

Answer 26

seismic refraction

Question 27

Used to locate faults, landslides,
and bedrock channels
Requires much deeper area
compared to the shot-to-detector-array distance – this makes sure that refracted
waves are not going to be a
problem in the measurement

Answer 27

seismic reflection

Question 28

Dependent on porosity and fracturing of rock, salinity of pore water, ground temperature, and clay content

Answer 28

resistivity methods

Question 29

Involves measurement of one or more magnetic or electric field components

Answer 29

electromagnetic methods

Question 30

a device with transmitter and receiver

Answer 30

terrain conductivity meter

Question 31

use radio transmitters and wider
in range (thousands of kilometers)

Answer 31

very low frequency VLF method

Question 32

uses pulsed electromagnetic waves
and their time needed to be reflected (from surface to subsurface interface back to surface) and provides high resolution.

Answer 32

ground probing radar GPR

Question 33

can be done on ground but can also be done using airplanes carrying magnetometers in what is called Aeromagnetic Surveying.

Answer 33

magnetic methods

Question 34

Probes are sent down drill holes to measure certain properties of along the wall of the hole

Answer 34

drillhole logging techniques

Question 35

Two holes are used with one hole having the
disturbance source (at a certain depth) and a
receiver is at the other hole (at same depth as
disturbance source) and receives seismic waves from the first hole.

Answer 35

cross hole technique