Geotech Flashcards
What is a Residual soil
a soil that has remained at the place of foramtion
What is a gap graded soil?
on a graduation curve a gap or missing range of particle sizes, shown as a straight line
Soil can be derived from
Igneous Rock
Sedimentary Rocks
Metamorphic Rocks
For the same volume - What soil particles has more surface area? large or small particles or is it equal ?
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.
Hydrometer Analysis is used for ?
to provide more info grain sized distribution and gradient for fine grains only
What happens to soil strength during compaction?
the soil gets stronger
** add more
What happens to soil permiability during compaction?
compaction reduces permiability
what is responsible for the slow of water in soils?
total head
what is liquefaction? and what causes it?
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
what three things are needed for the process of liquefaction to take place?
earthquake
sand
Ground water table at certain height
what is a CH soil?
high plasticity Clay
What is SP soil?
poorly grated sand
clays are formed from two fundamental building blocks, what are those two blocks ?
X
Resistivity (Conductivity) of Soil and rock is affected by what?
Porosity , moisture content, Salinity of pore water and grain size distribution
What is Soil Group Index? how to you find it for a soil?
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
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?
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
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
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
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?
The Dense Sand will have less long-term settlement
because clay is subject to long term settlement
what is long term settlement
what is the minimum safety factor for permanent slopes?
1.5
A horizontal pipe where diameter one is larger than diameter two further down the pipe
from 1 to 2 Pressure head does what?
Pressure head decreases from 1 to 2
what is SPT and what does the n-value tell you?
The standard Penetration Test - N -Valve provides indication of the relative density of cohesionless soils
Describe a shallow foundation?
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.
Describe Bearing capacity
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.
Describe Settlement
is the tendency of soils to deform (densify) under applied loads.
The most damaging settlements
differential settlements—those that are not uniform across the supported area.
