chapter 8: geologic hazards Flashcards
What are the factors affecting slope failures? ____
topography, geology, weather, seismic activity
______ in terms of inclination and height of the hill/cliff.
topography
_____ in terms of the material structure and strength of rocks and mineral formation.
geology
______ in terms of the seepage forces and run-off quantity and velocity of water during rainy days.
weather
______ as it affects inertial and seepage forces and due to the crustal movements of the earth
seismic activity
What are the seven methods of controlling slides? _____
- change the slope geometry to decrease the driving forces or increase the resisting forces by removal of very large volume of loose materials or debris along the top and side of slopes
- control surface water infiltration to reduce seepage forces
- planting the slope with thick, fast growing native vegetation and should be applied with burlaps bags and sprayed with mulch to increase growth
- sealing cracks and fissures with asphalt or soil cement and combines with grading to fill the cracks with soil
- providing retention structures to increase the resisting forces by constructing surface drains or drainage galleries, retaining walls and cribs, tie bars and shotcreting/guniting the rock slopes
- benching and placing materials at the toe to form a counterbermig forces, increase the driving forces
- driving sufficiently strong piles at an earth slope to a sufficient depth in a reliable stratum or strong rock founds
ation
These hazards are less disastrous than any other hazards in terms of lives lost but the total property damage exceeds than the others.
ground subsidence, settle/collapse
______ is defined as a downward movement of the natural ground surface to which no structures have been built.
subsidence
_____ is defined as a downward movement of the ground surface with the structure as caused by its dead life load and other forces.
settlement or collapse
What are the four causes of ground subsidence? _____
- extraction of fluids or solids, solution of rocks or a cementing agent in soils
- erosion
- physicochemical changes such change in environment condition as a result of human activities
- earthquakes or tectonic movements
What are the four sources of earthquakes? _____
- tectonic
- volcanic
- minor earth shaking attributed by the collapse of mines or caverns, to large slope failures such as avalanches, or to meteorites striking the earth
- man-made disturbances like blasting
______ are caused by a rupture in or near the earths’s crust that is usually associated with a faults, crustal warping pr fracturing in rocks.
tectonic
_____ are caused by effect of volcanic eruptions.
volcanic
What are the three causes of settlement? _____
removal of lateral support, sheared failure, fluctuation of the water table
_____ if an excavation is made next to a structure, the structure tend to move downward at a point due to the lateral yield of the slope.
removal of lateral support
______ causes the tipping of the structure and happens where the structure are constructed in saturated fine sand mass permitting the flow laterally it flows along together with the structure it supports.
sheared failure
_____ as the water table drop, either naturally or by pumping, the buoyancy in the dewatered region vanishes and the apparent weight of the earth mass & the structure increases.
fluctuation of the water table
____ is the center or source of the shock.
focus
____ is the place on the earth’s crust where the earthquake originates.
focus
____ the point on line on the surface directly above the focus.
epicenter
______ the projection of the focus on the ground surface or a limited area of the ground surface.
epicenter
Most earthquakes occur from 5 to 15 miles below the surface. However the foci of some earthquakes have been located at ____ miles down.
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What are the two measurements of an earthquake? _____
intensity, magnitude
_____ is a qualitative value based on the response of people and objectives on the earth’s surface.
intensity
_____ is a quantitative value computed from the seismograph.
magnitude
_____ is the study of earthquakes.
seismology
_____ is one who applies the methods or principles pf seismology as in earthquake prediction or seismic exploration.
seismologist
_____ is an instrument used to measure seismic waves.
seismograph
What are the eight major effects of earthquakes? ____
- collapse of man-mae structure especially those that can not withstand its magnitude
- disruption of utilities such as light and water
- fires caused by short circuits
- landslides and avalanches
- ground subsidence and settlement
- slope failures
- tsunamis
- floods
What are the four prevention of heave? ____
- excavation of the upper portion pf the swelling clays, mixing it with lime
- injection of lime
- coating with bitumen or a comparable air tight substance
- preflooding to permit expansion, then designing to contend with settlements of the softened material and attempting to maintain a balance between swell and consolidation
What are the five ways of flood control? _____
- floodplain zoning
- construction in high elevation
- diking to contain water
- channel straightening and lining
- flood-control dams
______ affords the best protection against flooding from the aspect of community development, since construction can be prohibited.
floodplain zoning
_____ as a necessary solution for many rapidly growing cities which are greatly affected by natural and development changes.
diking to contain water
_____ is a solution often applied to small rivers and streams to increase the flow of velocity and reduce the flood hazard and bank erosion.
channel straightening and lining
______ constructed upstream serve as storage reservoirs and are the most effective construction solution to flood protection.
flood-control dams
What are the four causes of slope failures/slides? _____
- the gravity of the weight of the slope materials which have saturated by water
- the increase in gravity and decrease in shearing strength acting together of the soil and rocks present along the slopes
- the removal of the lateral support particularly the removal of the toe of the slope
- ground movements caused by volcanic and tectonic movements like earthquake
What are the two slide-producing agents? ____
gravity, surface water
What are the classifications of slope failures? ____
creep, flow, falls, slides, avalanche and landslides
_____ are characterized by a sudden dislodgment of single or multiple blocks of soil or rock which fall in free descent.
falls
It is caused by the undercutting of slopes due to stream or wave erosion, usually assisted by seepage forces.
falls
_____ are characterized by a slow to rapid movements of soil and rocks along some well-defined planar failure surface.
slides
In ____ it is necessary to consider the character of the rock and its structure. Some rocks are hard and expensive to blast; others are soft or highly fractured that they may not stand up well on steep faces.
road cuts on a hill side
The _____ should be carefully considered in order to insure stability and constant slides.
slope of the sides of the road cut
_____ can usually be left standing with a steep face.
firm rock
_____ must be given their angle of repose.
unconsolidated materials
______, occurring during or after heavy rainfall and snow melt, cause ruin off to exceed the carrying capacity of the normal river channel which consequently overflows its banks and floods the adjacent valley.
natural floods
_____ of several kinds increase the incidence of flooding.
human activities
_____ involving the filling decreases the natural storage capacity, consequently increasing the extent of the floodplain.
construction in the river floofplain
______ represent substantial danger to humans and their works which may exist as a consequences of natural events, but often they are the result of human activities.
geologic hazards
What are the four types of geologic hazards? ____
floods, slope failures, ground subsidence, earthquakes
