©JUSTTRACY EXAM SOLUTIONS
19/11/2024 2:50pm
Soil Mechanics Exam Questions And
Improved Responses
Permeability - answers✔✔soils permeable due to existence of interconnected voids through
which water can flow from high energy points to low energy points
hydraulic gradient - answers✔✔i = ∆h/L
Darcy's Law - answers✔✔discharge velocity of water through saturated soils
v = ki k is hydraulic conductivity (coefficient of permeability)
seepage velocity - answers✔✔velocity of water through void space
constant-head test - answers✔✔laboratory determination of hydraulic conductivity where the
difference of head between inlet and outlet remains constant
falling-head test - answers✔✔laboratory determination of hydraulic conductivity where water
from a standpipe flows through a soil. head difference and time are recorded at t1 and t2
hydraulic conductivity and void ratio for granular soils - answers✔✔increases linearly
3 methods to estimate in situ hydraulic conductivity of compacted clay soils -
answers✔✔boutwell permeameter, constant-head borehole permeameter, porous probes
boutwell permeameter - answers✔✔hole is drilled and casing placed in it. casing filled with
water and falling-head permeability test is conducted, hole is deepened, repeat
constant-head borehole permeameter - answers✔✔constant head is maintained by supplying
water, rate of flow q is measured
, ©JUSTTRACY EXAM SOLUTIONS
19/11/2024 2:50pm
porous probes - answers✔✔driven into soil, constant or falling-head permeability test is
performed
accuracy of k determined in lab depends on 6 variables - answers✔✔temperature of fluid,
viscosity of fluid, trapped air bubbles present in soil specimen, degree of saturation of the soil
specimen, migration of fines during testing, and duplication of field conditions in the lab
laboratory consolidation tests - answers✔✔hydraulic conductivity of saturated cohesive soils
can be determined
flow line - answers✔✔line along which a water particle will travel from upstream to
downstream side in the permeable soil medium
equipotential line - answers✔✔line along which the potential head at all points is equal
flow nets - answers✔✔can be used to determine the uplift pressure at the base of a hydraulic
structure
stress in saturated soil without seepage - answers✔✔stress = H*gamma w + (HA -
H)*gamma sat
sigma - answers✔✔stress = effective stress + pore pressure
sigma prime - answers✔✔effective stress (intergranular stress) sum of vertical components of
all intergranular contact forces over a unit gross cross-sectional area
u - answers✔✔neutral stress or pore water pressure
FS against heaving - answers✔✔submerged weight of soil in heave zone per unit length of
sheet pile / uplifting force caused by seepage on the same volume of soil
effective stress in partially saturated soil - answers✔✔consists of intergranular, pore air, and
pore water pressures
19/11/2024 2:50pm
Soil Mechanics Exam Questions And
Improved Responses
Permeability - answers✔✔soils permeable due to existence of interconnected voids through
which water can flow from high energy points to low energy points
hydraulic gradient - answers✔✔i = ∆h/L
Darcy's Law - answers✔✔discharge velocity of water through saturated soils
v = ki k is hydraulic conductivity (coefficient of permeability)
seepage velocity - answers✔✔velocity of water through void space
constant-head test - answers✔✔laboratory determination of hydraulic conductivity where the
difference of head between inlet and outlet remains constant
falling-head test - answers✔✔laboratory determination of hydraulic conductivity where water
from a standpipe flows through a soil. head difference and time are recorded at t1 and t2
hydraulic conductivity and void ratio for granular soils - answers✔✔increases linearly
3 methods to estimate in situ hydraulic conductivity of compacted clay soils -
answers✔✔boutwell permeameter, constant-head borehole permeameter, porous probes
boutwell permeameter - answers✔✔hole is drilled and casing placed in it. casing filled with
water and falling-head permeability test is conducted, hole is deepened, repeat
constant-head borehole permeameter - answers✔✔constant head is maintained by supplying
water, rate of flow q is measured
, ©JUSTTRACY EXAM SOLUTIONS
19/11/2024 2:50pm
porous probes - answers✔✔driven into soil, constant or falling-head permeability test is
performed
accuracy of k determined in lab depends on 6 variables - answers✔✔temperature of fluid,
viscosity of fluid, trapped air bubbles present in soil specimen, degree of saturation of the soil
specimen, migration of fines during testing, and duplication of field conditions in the lab
laboratory consolidation tests - answers✔✔hydraulic conductivity of saturated cohesive soils
can be determined
flow line - answers✔✔line along which a water particle will travel from upstream to
downstream side in the permeable soil medium
equipotential line - answers✔✔line along which the potential head at all points is equal
flow nets - answers✔✔can be used to determine the uplift pressure at the base of a hydraulic
structure
stress in saturated soil without seepage - answers✔✔stress = H*gamma w + (HA -
H)*gamma sat
sigma - answers✔✔stress = effective stress + pore pressure
sigma prime - answers✔✔effective stress (intergranular stress) sum of vertical components of
all intergranular contact forces over a unit gross cross-sectional area
u - answers✔✔neutral stress or pore water pressure
FS against heaving - answers✔✔submerged weight of soil in heave zone per unit length of
sheet pile / uplifting force caused by seepage on the same volume of soil
effective stress in partially saturated soil - answers✔✔consists of intergranular, pore air, and
pore water pressures
