Materials Flashcards
Purpose of subsurface exploration
to determine the soil types, soil strengths, depth of rock, rock type and quality, and groundwater levels
Three components of exploration
Boring, Sampling, Testing (Lab & In-situ)
Boring Definition
Soil and rock samples obtained by drilling vertical holes known as boring
purpose of boring
obtain samples of geologic materials for examination, classification, and laboratory testing, and permit in-situ measurements of the physical and engineering properties of materials
Drilling machine
consist of power source, mast for lifting, and pump for circulating water or mud to lower, rotate, and raise the drilling tools to advance the hole and obtain samples
Casing
used to retain the hole in the normal test boring operation
drill rods
connect the drilling machine to the drill bits or sampler during the normal test or core boring operation with rotary machines
drilling bits
used to cut soil or rock, rock bits are used for rock drilling, core bits (tungsten carbide teeth or diamonds) used for rock coring while advancing the hole
sampling tools
many types of samplers are used and discussed elsewhere in this section
Hollow-stem auger
during advance, the auger fights remove the soil from the hole and the hollow stem serves as casing. a bottom bit cuts the soil and a removable plug on a rod prevents soil from rising in the hollow portion of the stem, may be used with all types of soil including sandy but not suitable if the soil is mixed with gravel
Wash boring
soil exploration below the ground water table is usually very difficult to perform by means of pits or auger-holes. wash boring in such cases is a very convenient method provided the soil is either sand, silt, or clay. the method is not suitable if the soil is mixed with gravel or boulders.
disturbed soil samples
have experienced large structural disturbances during the sampling operation and may be used for identification and classification tests
undisturbed samples
structural disturbance is kept to a minimum during the sampling process, undisturbed samples are used for consolidation and strength tests
split-barrel sampler (split-spoon)
used in conjunction with the Standard Penetration Test (SPT), disturbed sample, suitable for moisture content, gradation, atterberg limits tests, and valuable for visual identificaiton
shelby tube (thin wall tube)
pushed into the soil with a relatively rapid, smooth stroke and then retracted, undisturbed sample, suitable for strength and consolidation tests
stationary piston sampler (thin wall tube)
piston positioned at bottom of thin-wall tube while the sampler is lowered to the bottom of the hole, undisturbed samples, required when highly undisturbed sample is needed
denison core barrel (double tube soil core barrel)
used in materials such as hard clays and cemented sands, includes a rotating outer barrel and bit containing a fixed inner barrel
standard penetration test (SPT)
identifies penetration resistance value “N”, angle of internal friction of cohesionless soil, the unconfined compressive strength of a cohesive soil, and the material’s unit weight, measure in-situ compactness of soils, 140lb hammer falling from 30 in high
refusal
a penetration of less than 6 in for 50 hammer blows or 18 in for total 100 hammer blows
penetration resistance (N)
sum of the blows per foot from the second and third intervals
boring log
two sets required, field log and report log
An undisturbed clay is required for consolidation testing. The sample is best obtained using a: (A) Cone penetration test (B) pressure meter (C) split spoon (D) shelby tube
(D) shelby tube, only split spoon and shelby tube are the only test options provided, shelby tube is undisturbed samples, split spoon is disturbed samples
coarse grain soil
gravel and sand
fine grain soil
silt and clay
Particle Size Distribution
used for obtaining the grain size distribution of coarse grained soils, used to identify well graded and poorly graded soils
consistency limits
atterberg limits define the water contents at which the fine grained soil changes consistency
soil classification
USCS - Unified Soil Classification
AASHTO Soil Classification
characteristics of coarse grained soils/Sand and Gravel
can see individual gains by eye
cohesionless
non-plastic
granular
characteristics of fine grain soil/Clay
cannot see individual grains by eye alone
cohesion
plastic
expansive soil
characteristics of fine grain soil/Silts
cannot see individual grains by eye alone
cohesionless
non-plastic
granular
Frost
`Atterberg limits
define the water contents at which the fine grained soil changes consistency (at least 50% soil passing the #200 sieve)
liquid limit (LL)
the moisture content at which the cohesive soil pass from liquid state to plastic state
plastic limit (PL)
the moisture content at which the cohesive soil pass from plastic state to semisolid state
shrinkage limit (SL)
the moisture content at which the cohesive soil pass from semisolid state to solid state
plasticity index (PI)
LL-PL
For soils of group MH, LL of a sample is
LL is greater than or equal to 50
