GEO CE MODULE 1: Geotechnical Engineering Flashcards
It is the technical specialty that deals with soil and rock as supporting materials for structures.
Geotechnical Engineering
It deals with the various foundation types that work between the structure and the ground.
Geotechnical Engineering
It deals with the stability of soil or rock slopes whose failure may cause loss of human lives or damage to property.
Geotechnical Engineering
It is the basic science that is concerned with the study of the history of the Earth, the rocks of which it is composed, and the changes that it has undergone or is undergoing.
Geology
It is the science of rocks and earth processes.
Geology
It deals with the application of geologic fundamentals to engineering.
Engineering Geology
True or False. An example of the application of engineering geology is the mapping of active seismic faults that are to be avoided when making plans for human habitat development, roadway construction, or power plant construction.
True
True or False. Understanding various geological formations and rock types does not provide geotechnical engineers the knowledge necessary in assessing the sustainability of a site for human activities.
False
These are formed from rocks as it is acted upon by physical, chemical, and biological forces.
Soils
The extent to which a parent rock changes to soil is a _________________________________________.
a function of the rate and overall time of the prevailing reactions and processes.
From an engineering viewpoint, it is any earthly material that can be removed with a spade, shovel, or bulldozer and is the product of natural weathering.
Soil
From an __________ viewpoint, the soil is any earthly material that can be removed with a spade, shovel, or bulldozer and is the product of natural weathering.
engineering
From an engineering viewpoint, the soil includes ________ and ___________.
gravel and sand deposits
From a geological viewpoint, it may be considered as the superficial unconsolidated mantle of disintegrated and decomposed rock material.
Soil
From a ____________ viewpoint, the soil may be considered as the superficial unconsolidated mantle of disintegrated and decomposed rock material.
geological
From a pedological (soil science) viewpoint, it is the weathered transformation product of the outermost layer of the solid crust, differentiated into horizons varying in type and amounts of mineral and organic constituents, usually unconsolidated and of various depths.
soil
From a __________ viewpoint, the soil is the weathered transformation product of the outermost layer of the solid crust, differentiated into horizons varying in type and amounts of mineral and organic constituents, usually unconsolidated and of various depths.
pedological (soil science)
It serves as the parent material for natural soil formation.
Rock
They are used as ground foundation support and the crushed rock fragments are used as major construction materials.
Rocks
What are the uses of rocks in construction?
a. ground foundation support
b. crushed rock fragments as major construction materials
Rock classification may be made on the basis of:
a. geological origin and genesis,
b. rock mass strength, and
c. weathering and environmental factors
It is the most common rock classification system.
classification of rock based on its geological origin and genesis
Three classifications of rocks based on geological origin or genesis.
a. igneous rocks
b. metamorphic rocks
c. sedimentary rocks
These are rocks that have solidified from a molten or partly molten siliceous solution.
Igneous rocks
The molten solution is called _______.
magma
When magma cools and solidifies in direct contact with the atmosphere it is referred to as _________ while cooling in the subsurface leads to an ___________ formation
Extrusive and Intrusive
True of False. When magma cools and solidifies in direct contact with the atmosphere it is referred to as intrusive while cooling in the subsurface leads to an extrusive formation.
False
These rocks are naturally consolidated or unconsolidated transported materials.
Sedimentary rocks
These rocks form as a result of subjecting igneous or sedimentary rocks to elevated temperatures and pressures.
Metamorphic rocks
Igneous rocks comprise about ________ and metamorphic rocks about ________ of the terrestrial and sub-oceanic earth crust, leaving about ____ for the sedimentary rocks.
80%, 15%, and 5%
Give common rock examples.
a. granite and basalt (igneous)
b. sandstone and limestone (sedimentary)
c. schist and gneiss (metamorphic)
Granite and Basalt are __________ rocks.
igneous
Sandstone and Limestone are _______ rocks.
sedimentary
Schist and gneiss are ________ rocks.
metamorphic
It is the study of the ways in which rocks or sediments are arranged and deformed on the earth, and it involves all three rock types.
Structural Geology
These rocks are deposited in horizontal layers.
Sedimentary rocks
Any rock unit that is recognizable and mappable in the field.
formation
True or False. Formations can include different rock types ( so long as the entire package cannot be distinguished from adjacent formations).
False
True of False. Sometimes formations are further subdivided into members.
True
These are the boundaries between formations.
contacts
Contacts can be ________, _________, and __________.
depositional, erosional, and structural
This is the two-dimensional view of rock distribution.
map view
It is a view of a vertical slice of the earth like you might see at a road cut or a stream cut.
Geologic cross-section
It is a combination of those two representations and gives a 3-d view of formations and contacts.
Block diagram
It looks like a block and shows a map view on top, and a cross-sectional view on each of its visible sides.
Block diagram
It can reveal details of a structure not visible in map view, such as cross-bedding.
Cross-sectional view
True or False. Geological structures, such as folds, faults, joints, and unconformities, encountered in geology are regularly encountered in civil engineering work.
True
These are defined as wavy undulations developed in the rocks of the Earth’s crust due to horizontal compression resulting from gradual cooling of the Earth’s crust, lateral deflection, and intrusion of magma in the upper strata.
folds
These are the rocks that are bent around an imaginary line.
fold axis
True or False. All geological folds have such a fold axis.
True
It is where the continuity of the rock mass breaks.
Fracture
These are fractures in crustal strata along which appreciable shear displacement of the adjacent rock blocks have occurred relative to each other, probably due to tectonic activities.
Faults
This is the fracture along which the shear displacement has taken place.
fault plane
True or False. The term ‘fault’ includes both the fault plane and the displacement that has occurred along it.
True
It is a fracture where little or no movement has taken place.
joint
The most common form of discontinuity encountered.
joint
These ______ can occur in several sets and are approximately parallel within specific sets of series of discontinuities that have the same geologic origin, orientation, spacing, and mechanical characteristics.
discontinuities
The discontinuities make the rock mass ________.
anisotropic
It is a material whose physical, and mechanical properties, etc., are not all the same in each direction.
Anisotropic
It is the surface or plane of separation between two series of rock beds or geological formations that belong to two different geologic ages and they are in, most cases, different in their geologic structure.
Plane of unconformity or unconformity
It constitutes the line of unconformity in the geological map.
intersection of the plane of unconformity with the ground surface/topography
It occurs when there is the erosion of a layer or layers of deposited rock followed by the deposition of new sedimentary rock on top.
unconformity
It is called _________ because the ages of the layers of the rock that are abutting each other are discontinuous at the ________.
unconformity
The expected age of layer or layers of rock is/are missing due to _________ and ________________.
erosion and some period in geologic time is not represented
Enumerate the three types of unconformities.
a. Discomformity
b. Angular unconformity
c. Nonconformity
Sedimentary layers are deposited over eroded horizontal sedimentary layers.
Disconformity
Sedimentary layers are deposited over an eroded angular (tilted or folded) rock.
Angular unconformity
Sedimentary layers are deposited over eroded igneous or metamorphic rock.
Nonconformity
It is a branch of mechanics that studies the mechanical properties of various types of soil and its strength at different moisture-content levels.
Soil mechanics
It provides the scientific base upon which design formulas and codes are developed for everyday engineering design practice.
Soil mechanics
Who is the father of Modern Soil Mechanics?
Karl von Terzaghi
The title of the writing of Karl von Terzgahi.
The Influence of Modern Soil Studies on the Design and Construction of Foundations
The Influence of Modern Soil Studies on the Design and Construction of Foundations was written on _______.
1951
According to Karl von Terzaghi, foundations can appropriately be described as a necessary _______.
evil
True or False. Architects or Engineers who do not wish to make use of the growing knowledge of foundation design are not rendering true service to their profession.
True
True or False. Since substructures are not as important as superstructures, persons who are well-qualified in the design of substructures should not always be consulted.
False
True or False. The old proverb ‘stitch in time saves nine’ should always be kept in mind.
True
It is not a coherent solid material like steel and concrete but it is a particulate material.
Soil
True or False. Soil mass is generally a three-phase system. It consists of solid particles, liquid, and gas.
True
The phase system may be expressed in SI units either in terms of _________ or ___________.
mass-volume or weight-volume relationships
Why are the interrelationships of the different phases are important?
They help to define the condition or the physical make-up of the soil.
As the relative proportions of the three phases vary in soil deposit, it is useful to consider a __________ which will represent these phases distinctly and properly quantify the amount of each phase.
Soil model
A schematic diagram of the three-phase system is shown in terms of?
weight and volume symbols respectively for solids, water, and air
True or False. In a schematic diagram of the three-phase system, the weight of the air can be neglected.
True
The void ratios of natural sand deposits depend upon what?
a. shape of the grains
b. uniformity of grain size
c. conditions of sedimentation
The void ratios of clay soils range from ________.
less than unity to 5 or more
True or False. The soils with higher void ratios have a loose structure and generally belong to the montmorillonite group.
True
The soils with higher void ratios generally belong to the ____________.
montmorillonite group
A material is ___________ if it contains continuous voids.
permeable
True or False. All materials such as rocks, concrete, soils, etc. are permeable.
True
It has a decisive effect on the stability of the foundations, seepage loss through embankments of reservoirs, drainage of subgrades, excavation of open cuts in water-bearing sand, rate of flow of water into wells, and many others.
Permeability of soils
It is simply a contour of constant.
Equipotential line
The interaction between soils and percolating water has an important influence on:
- the design of foundations and earth slopes
- the quantity of water that will be lost by percolation through a dam or its subsoil
True or False. Foundation failures due to ‘piping’ are quite rare.
False
It is a phenomenon by which the soil on the downstream sides of some hydraulic structures gets lifted up due to excess pressure of water.
Piping
It is the pressure that is exerted on the soil due to the seepage of water.
Seepage force or pressure
The pressure transmitted from grain to grain at the contact points through soil is mass.
intergranular or effective pressure
It is responsible for the decrease in the void ratio or increase in the frictional resistance of a soil mass.
intergranular or effective pressure
If the pores of a soil mass are filled with water and if pressure is induced into the pore water, tries to separate the grains, the pressure is termed as ________.
pore water pressure or neutral stress
The effect of pore water pressure or neutral stress on the soil.
to increase the volume or decrease the frictional resistance of the soil mass.
Constant ratios exist between stresses and strains.
Elastic theory
When a load is applied to the soil surface, it increases the _________ within the soil.
vertical stresses
True or False. The increased stresses are greatest directly under the loaded area but extend indefinitely in all directions.
True
Enumerate the two formulas widely used in computing stresses in soils.
Boussinesq and Westergaard formulas
The extent of the elastic layer below the surface loadings may be any one of the following:
- Infinite in the vertical and horizontal directions
- Limited thickness in the vertical direction underlain with a rough rigid base such as a rocky bed.
The loads at the surface may act on ________ or _________.
flexible or rigid footing
The stress conditions in the elastic layer below vary according to the __________________________.
rigidity of the footings and the thickness of the elastic layer
They transfer loads to the subsoil through the foundation.
Structure
True or False. The effects of the loads are felt by the soil normally up to a depth of about four to five times the width of the foundation.
False
The soil within this depth gets _________ due to imposed weight.
compressed
The compression of the soil mass leads to?
to the decrease in the volume of the mass which result in the settlement of the structure
How can the displacements that develop at any given boundary of the soil mass be determined?
by summing up the displacements of small elements of the mass resulting from the strains by a change in the stress system
It is due to imposed stresses that may be almost immediate or time-dependent according to the permeability characteristics of the soil.
Compression of the soil
These soils which are highly permeable are compressed in a relatively short period of time.
Cohesionless soils
These soils are less permeable.
cohesive soils
The compressibility characteristics of a soil mass might be due to any or a combination of the following factors:
- Compression of the solid matter
- Compression of water and air within the voids
- Escape of water and air from the voids
True or False. When a saturated clay-water system is subjected to external pressure, the pressure applied is initially taken by the water in the pores resulting thereby in an excess pore water pressure.
True
If ________ is permitted, the resulting hydraulic gradients initiate a flow of water out of the clay mass and the mass begins to compress.
drainage
A portion of the applied stress is transferred to the ________, which in turn causes a reduction in the excess pore pressure.
soil skeleton
This process involves a gradual compression occurring simultaneously with a flow of water out of the mass and with a gradual transfer of the applied pressure from the pore water to the mineral skeleton.
consolidation
The process opposite to consolidation is called _______.
Swelling
It involves an increase in the water content due to an increase in the volume of the voids.
Swelling
It is the ability to resist sliding along internal surfaces within a mass.
shear strength
They depend upon the shearing resistance offered by the soil along the probable surfaces of slippage.
a. stability of a cut
b. the slope of an earth dam
c. the foundation of structures
d. the natural slopes of hillsides
It depends on the strength and compressibility of the subsoil.
Stability of structures
The stability of Structures depends on the?
strength and compressibility of the subsoil
Field and laboratory investigations are required to obtain the essential information on the subsoil.
Soil Exploration or Soil Investigation
It is one of the most important parts of Foundation Engineering and at the same time the most neglected part of it.
Soil Exploration
The success or failure of a foundation depends essentially on the __________________________________________________.
reliability of the various soil parameters obtained from the field investigation and laboratory testing and used as an input into the design of foundations.
True or False. Sophisticated theories alone will give a safe and sound design.
False
It is a must in the present age for the design of foundations of any project.
Soil exploration
True or False. The extent of the exploration depends upon the magnitude and importance of the project.
True
Enumerate the two types of slope
- Natural slopes
- Manmade slopes
These are slopes that exist in nature and are formed by natural causes.
Natural slopes
The slopes whether natural or artificial maybe
- infinite slopes
- finite slopes
It is used to designate a constant slope of infinite extent.
infinite slope
Give an example of the infinite slope.
long slope face of a mountain
True or False. The slope length depends on the height of the dam or embankment.
True
It is an extremely important consideration in the design and construction of earth dams.
Slope stability
The important factors that cause instability in a slope and lead to failure are:
- Gravitational force
- Force due to seepage of water
- Erosion of the surface of slopes due to flowing water
- The sudden lowering of water adjacent to a slope
- Forces due to earthquakes
What is the effect of all the causes of the failure of slopes?
movement of soil from high points to low points
True or False. The most important of such forces is the component of gravity that acts in the direction of probable motion.
True
True or False. The various effects of flowing or seeping water are generally recognized as very important in stability problems, but often these effects have been properly identified.
False
It is caused by the removal of a certain weight of soil and may thus lead to increased stability as far as mass movement is concerned.
Erosion
True or False. Erosion in the form of undercutting at the toe may increase the height of the slope, or decrease the length of the incipient failure surface, thus increasing the stability.
False
These are structures that are built to retain vertical or nearly vertical earth banks or any other material.
Retaining walls
They may be constructed of masonry or sheet piles.
Retaining walls
Retaining walls may be constructed of ________ and ________.
masonry and sheet piles
True or False. Retaining walls may retain water also.
True
Enumerate the principal type of retaining walls.
a. Gravity walls
b. Semi-gravity walls
c. Cantilever walls
d. Counterfort walls
e. Buttressed walls
Enumerate the use of retaining wall
a. embankment
b. cut
c. a bridge abutment
d. water storage
True or False. Whatever may be the type of wall, all the retaining walls have to withstand lateral pressures either from earth or an other material on their faces.
True
It resists movement because of its heavy sections.
Gravity walls
True or False. Gravity walls are built of mass concrete or stone or brick masonry. Reinforcements are required in these walls.
False
These are walls that are not as heavy as gravity walls. A small amount of reinforcement is used for reducing the mass of the concrete.
Semi-gravity walls
The stems of _________ walls are thinner in section.
Cantilever
Cantilever walls are made of?
reinforced concrete
These walls are similar to cantilever walls except that the stem of the walls spans horizontally between vertical brackets.
Counterfort walls
They are provided on the backfill side.
Counterfort walls
These walls are similar to counterfort walls except the brackets or buttress walls are provided on the opposite side of the backfill.
buttressed walls
True or False. The backfill tries to move the wall from its position.
True
True or False. Sheet pile walls are more flexible than other types.
True
The earth materials that constitute relatively the thin outer shell, called the crust, of the Earth are arbitrarily categorized by civil engineers as _______ and _________.
soils and rocks
Soils and rocks are made up of small crystalline units known as _________.
minerals
It is basically a naturally occurring inorganic substance composed of one or more elements with a unique chemical composition, unique arrangement of elements (crystalline structure), and distinctive physical properties.
Minerals
It is a hard, compact, and naturally occurring earth material composed of one or more minerals and is permanent and durable for engineering applications.
Rock
Rocks generally require _________ and ________ for their excavation.
blasting and machinery
True or False. Radiologists consider engineering soils as unconsolidated rock materials composed of one or more minerals.
False
Rock is distinguished from the other essentially on the basis of its _____________.
mineralogical composition
When do the properties of rock become relevant?
a. when it is used as the foundation of a high-rise building or a large dam
b. when one examines the stability of the slope of a mountain or a tunnel
c. subject of the study for the occurrence of earthquakes
It is the subject concerned with the study of the response of rock to an applied disturbance caused by natural or engineering processes.
Rock Mechanics
It deals with the engineering applications of the basic principles and the information available in the subjects of engineering geology and rock mechanics in an economic way.
Rock Engineering
Rock Mechanics and Rock Engineering are closely concerned with several engineering disciplines such as?
civil, mining, petroleum, and geological engineering
It applies to a large extent of rock, from several meters to a few kilometers, which can include many discontinuities of different forms.
rock mass
True or False. The presence of discontinuities such as faults, joints, and bedding planes in the rock mass does not influence its engineering behavior.
False
True or False. In rock mechanics and geology, we deal with discontinuities, which include bedding planes, faults, and joints or the orientation (or attitude) of a plane.
True
True or False. It is very important to define the orientation of these planes without any ambiguity.
True
Give some of the common terms associated with the orientation of a plane.
a. dip
b. dip direction
c. strike
It is the steepest inclination of the plane to horizontal.
Dip or true dip
It is the inclination of any arbitrary line on the plane to horizontal, which is always less than the true dip.
Apparent dip
True or False. When marble is rolled down the plane, it follows the line of minimum inclination, defining the true dip.
False
It is the trace (or intersection) of the dipping plane with the horizontal reference plane.
Strike
It is the orientation of the horizontal line drawn on the dipping plane and it is perpendicular to the dip section.
Strike
Dip direction can be in the range of?
0 - 360 degrees
It is the direction of the horizontal trace (projection) of the line of dip, measured clockwise from the north.
Dip direction or Dip azimuth
The dip direction is measured ___________.
clockwise from the north
It is the angle of the inclined plane made with the horizontal, which is in the range of 0-90.
Dip
The dip is in the range of ______.
0-90 degrees
True or False. A horizontal plane has a dip of 90 degrees and a vertical plane has a dip of 0 degrees.
False
It is a systematic method of presentation that enables some simple stability analyses in engineering applications to be carried out.
Spherical Presentation of Geological Data
It is the interface between a superstructure and its supporting soil.
Foundation
True or False. A common type of foundation for single-family homes consists of strip footings placed under load-bearing basement walls.
True
True or False. Another common practice is to use a wooden slab to spread the weight of the building over the soil underneath.
false
It is the study of different types of foundation and their proper applications.
Foundation Engineering
It is the application and practice of the fundamental principles of soil mechanics and rock mechanics in the design of foundations of various structures.
Foundation Engineering
It involves the analysis and design of earth-retaining structures such as retaining walls, sheet-pile walls, and braced cuts.
Foundation Engineering
True or False. Depending on the properties of the soil at a site, shallow or deep piles may be deployed.
True
The construction of a bridge over water may require the use of ____________ on which piers are constructed.
deep caissons
True or False. It is customary practice to regard a foundation as shallow if the depth of the foundation is greater than or equal to the width of the foundation.
False
Enumerate the different types of footing.
a. plain concrete foundation
b. stepped reinforced concrete foundation
c. reinforced concrete rectangular foundation
d. reinforced concrete wall foundation
The stability of a structure depends upon the stability of the supporting soil. Two important factors that are to be considered are:
- The foundation must be stable against shear failure of the supporting soil.
- The foundation must not settle beyond a tolerable limit to avoid damage to the structure.
True or False. The theories based on shear failure criteria indicate the settlement that a footing may undergo uder the ultimate loading conditions.
False
How can the allowable bearing pressure be obtained?
by applying a suitable factor of safety to the ultimate value
When we design a foundation, we must see that the structure is safe on two counts. They are
- The supporting soil should be safe from shear failure due to the loads imposed on it by the superstructure
- The settlement of the foundation should be within permissible limits
Enumerate the two types of bearing pressures.
- A pressure that is safe from shear failure criteria (allowable bearing pressure)
- A pressure that is safe from settlement criteria (safe bearing pressure)
True or False. If the structure, as a whole, settles uniformly into the ground there will be detrimental effects on the structure as such.
False
Uniform settlement is possible only if the ___________________________________________
subsoil is homogenous and the load distribution is uniform
It is considered the common method of transmitting loads to subsoil through spread footings carrying single-column loads.
Shallow Foundation I
Enumerate the types of foundations
- Cantilever footings
- Combined footings
- Mat foundations
True or False. When a column is near or right next to a property limit, a square or rectangular footing concentrically loaded under the column would extend into the adjoining property.
True
True or False. If the adjoining property is a public sidewalk or alley, local building codes may not permit such footings to project into public property.
False
True or False. When the adjoining property is privately owned, the footing must be constructed within the property.
True
Enumerate the three alternatives when the adjoining property is privately owned.
- Cantilever footing
- Combined footing
- Mat or Raft Foundation
It normally comprises two footings connected by a beam called a strap.
Cantilever Footing or Strap Footing
It is a special case of a combined footing.
Combined footing
It is a long footing supporting two or more columns in one row.
Combined footing
It is a large footing, usually supporting several columns in two or more rows.
Mat or Raft Foundations
True or False. In the majority of cases, mat foundations are normally used where the soil has high bearing capacity and where the total area occupied by an individual footing is not less than 50% of the loaded area of the building.
False
They are normally used where the soil close to the ground surface and up to the zone of significant stress possesses sufficient bearing strength to carry the superstructure load without causing distress to the superstructure due to settlement.
Shallow foundation
True or False. Where the topsoil is either loose or soft or of a swelling type the load from the structure has to be transferred to deeper firm strata.
True
When the topsoil is either loose or soft or of a swelling type, the load from the structure has to be transferred to ______________.
deeper firm strata
The structural loads may be transferred to deeper firm strata by means of __________.
piles
They are long slender columns either driven, bored or cast-in-situ.
Piles
They are made of a variety of materials such as concrete, steel, timber, etc.
Driven piles
They are concrete piles.
cast-in-situ piles
True or False. Piles may be subjected to vertical or lateral loads or a combination of horizontal and lateral loads.
False
If the diameter of a bored-cast-in-situ pile is greater than about 0.75 m, it is sometimes called ________, __________, or __________.
drilled pier, drilled caisson, or drilled shaft
The distinction made between a small diameter bored cast-in-situ pile (less than 0.75 m) and a larger one is just _____________.
for the sake of design considerations
According to the method of construction, there are three types of piles. Enumerate
- Driven piles
- Cast-in-situ piles
- Driven and cast-in-situ piles
When the soil of low bearing capacity extends to a considerable depth, they are generally used to transmit vertical and lateral loads to the surrounding soil media.
piles
True or False. Piles that are used under tall chimneys, television towers, high-rise buildings, high retaining walls, offshore structures, etc. are normally subjected to low lateral loads.
False
Piles or pile groups should resist ________ and ________ movements.
vertical and lateral
Give the requirements for a satisfactory foundation.
- the vertical settlement or the horizontal movement should not exceed an acceptable maximum value
- there must not be failure by yield of the surrounding soil or the pile material
They are used in foundations to take normally vertical loads and small lateral loads.
Vertical piles
They are used in combination with vertical piles when the horizontal load per pile exceeds the value suitable for vertical piles.
Batter piles
Other names for batter piles.
inclined piles or raker piles
It is the angle made by the pile with the vertical, which may be up to 30 degrees.
Degree of batter
It is called _______ if the lateral load acts on the pile in the direction of the batter.
in-batter or negative batter pile
It is called _______ if the lateral load acts in the direction opposite to that of the batter.
out-batter or positive batter
True or False. Because piers and piles serve the same purpose, sharp deviations can be made between the two.
False
The distinctions of piers and piles are based on the ________________.
method of installation
It is a pile, ___________, with a diameter less than 0.75m (or 2.5 ft) is sometimes called a small diameter pile.
cast-in-situ
It is a pile, cast-in-situ, with a diameter less than 0.75m (or 2.5 ft) is sometimes called a ____________________.
small diameter pile
A pile greater than 0.75m is called __________________.
large diameter bored-cast-in-situ pile
Other names of large diameter bored piles.
drilled piers, drilled shafts and drilled caissons
True or False. All four types of drilled piers are similar in construction technique but differ in their design assumptions and in the mechanism of load consumption to the surrounding earth mass.
False
They develop their support from end-bearing on strong soil, “hardpan” or rock.
Straight-shaft end-bearing piers
True or False. The overlying soil in straight-shaft end-bearing piers is assumed to contribute nothing to the support of the load imposed on the pier.
True
They pass through overburdened soils that are assumed to carry none of the load and penetrate far enough into an assigned bearing stratum to develop design load capacity by side wall friction between the pier and bearing stratum.
Straight-shaft side wall friction piers
They are of the same construction, but with both side wall friction and end, bearing assigned a role in carrying the design load.
Combination of straight-shaft side wall friction and end bearing piers
When carried into rock, the combination of straight-shaft side wall friction and end-bearing piers may be referred to as a ______________ or ___________________________.
socketed pier or a drilled pier with a rock socket
When carried into rock, this pier may be referred to as a socketed pier or a drilled pier with a rock socket.
combination of straight-shaft side wall friction and end-bearing piers
These are piers with a bottom bell or under ream.
Belled or under-reamed piers
True or False. In belled or under-reamed piers, a greater percentage of the imposed load on the pier top is assumed to be carried by the base.
True
What is the general practice when the soil close to the ground surface possesses sufficient bearing capacity?
to use shallow foundations for the foundations of the building and other such structures
When the topsoil is either loose or soft, the load from the superstructure has to be ______________.
transferred to deeper firm strata
These are the obvious choices when the topsoil is either loos or soft and the load from the superstructure has to be transferred to deeper firm strata.
pile or pier foundations
Give some techniques that can be used to improve soil properties.
- The use of replacement material through excavation
- The injection of special material (grouts) into the original soil
- Placing geosynthetic fabrics or textiles in horizontal layers
- soil improvement
It is proven to be more economical than deep foundations or where the alternate method may become inevitable due to certain sites and other environmental conditions.
Soil improvement
It is frequently termed soil stabilization, which in its broadest sense is an alteration of any property of a soil to improve its engineering performance.
Soil improvement
Enumerate the uses of soil improvement.
- increases shear strength
- reduces permeability
- reduces compressibility
The methods of soil improvement considered in this topic are:
- Mechanical compaction
- Dynamic compaction
- Vibroflotation
- Preloading
- Sand and stone columns
- Use of admixtures
- Injection of suitable grouts
- Use of geotextiles
