PDF | Application of civil engineering to earthen materials Soil Rock Groundwater . 1/19/ MnDOT Geotechnical Manual ii. GEOTECHNICAL ENGINEERING MANUAL. GEOTECHNICAL ENGINEERING SECTION. Geotechnical engineering is an interesting subject. Unlike many engineering disciplines, it is not a pure science but rather it is an art form that requires both.
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Introduction to Geotechnical Engineering. Evert C. Lawton, Ph.D., P.E. and. Steven F. Bartlett, Ph.D., P.E.. “Why You Should Study. Geotechnical Engineering ” or. FCE – GEOTECHNICAL ENGINEERING I. OSN - Lecture Notes. University of Nairobi. Page i. TABLE OF CONTENTS. 1. OVERVIEW. Proceedings of the Eighth Regional Conference for Africa on Soil Mechanics and Foundation Engineering /Harare / Geotechnical evaluations for tailings.
Unsourced material may be challenged and removed. September Main article: Retaining wall A retaining wall is a structure that holds back earth. Retaining walls stabilize soil and rock from downslope movement or erosion and provide support for vertical or near-vertical grade changes.
Cofferdams and bulkheads, structures to hold back water, are sometimes also considered retaining walls. The primary geotechnical concern in design and installation of retaining walls is that the weight of the retained material is creates lateral earth pressure behind the wall, which can cause the wall to deform or fail.
The lateral earth pressure depends on the height of the wall, the density of the soil, the strength of the soil , and the amount of allowable movement of the wall. This pressure is smallest at the top and increases toward the bottom in a manner similar to hydraulic pressure, and tends to push the wall away from the backfill. Groundwater behind the wall that is not dissipated by a drainage system causes an additional horizontal hydraulic pressure on the wall.
Gravity walls[ edit ] Gravity walls depend on the size and weight of the wall mass to resist pressures from behind. Gravity walls will often have a slight setback, or batter, to improve wall stability.
For short, landscaping walls, gravity walls made from dry-stacked mortarless stone or segmental concrete units masonry units are commonly used. Earlier in the 20th century, taller retaining walls were often gravity walls made from large masses of concrete or stone.
Today, taller retaining walls are increasingly built as composite gravity walls such as: geosynthetic or steel-reinforced backfill soil with precast facing; gabions stacked steel wire baskets filled with rocks , crib walls cells built up log cabin style from precast concrete or timber and filled with soil or free draining gravel or soil-nailed walls soil reinforced in place with steel and concrete rods.
For reinforced-soil gravity walls, the soil reinforcement is placed in horizontal layers throughout the height of the wall. Commonly, the soil reinforcement is geogrid, a high-strength polymer mesh, that provide tensile strength to hold soil together. The wall face is often of precast, segmental concrete units that can tolerate some differential movement.
The reinforced soil's mass, along with the facing, becomes the gravity wall. The reinforced mass must be built large enough to retain the pressures from the soil behind it. Some of the ideas may be close to reality whereas others may turn out to be elusive, but they all present possibilities to strive for and potential goals for the future.
Geoengineers are poised to expand their roles and lead in finding solutions for modern Earth systems problems, such as global change, emissions-free energy supply, global water supply, and urban systems.
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Opportunities for Research and Technological Innovation Finding similar items Geological and Geotechnical Engineering in the New Millennium: Read Online. View Cover. Login or Register. download Paperback: E-mail this page Embed book widget. Geotechnical engineering is the branch of civil engineering concerned with the engineering behavior of earth materials.
Geotechnical engineering is important in civil engineering, but also has applications in military , mining , petroleum and other engineering disciplines that are concerned with construction occurring on the surface or within the ground.
A typical geotechnical engineering project begins with a review of project needs to define the required material properties.
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Then follows a site investigation of soil , rock, fault distribution and bedrock properties on and below an area of interest to determine their engineering properties including how they will interact with, on or in a proposed construction. Site investigations are needed to gain an understanding of the area in or on which the engineering will take place. Investigations can include the assessment of the risk to humans, property and the environment from natural hazards such as earthquakes , landslides , sinkholes , soil liquefaction , debris flows and rockfalls.
Foundations are designed and constructed for structures of various sizes such as high-rise buildings, bridges , medium to large commercial buildings, and smaller structures where the soil conditions do not allow code-based design. Foundations built for above-ground structures include shallow and deep foundations. Retaining structures include earth-filled dams and retaining walls.
Earthworks include embankments , tunnels , dikes and levees , channels , reservoirs , deposition of hazardous waste and sanitary landfills. Geotechnical engineers are extensively involved in earthen and concrete dam projects, evaluating the subsurface conditions at the dam site and the side slopes of the reservoir, the seepage conditions under and around the dam and the stability of the dam under a range of normal and extreme loading conditions.
Geotechnical engineering is also related to coastal and ocean engineering. Coastal engineering can involve the design and construction of wharves , marinas , and jetties.
Ocean engineering can involve foundation and anchor systems for offshore structures such as oil platforms. The fields of geotechnical engineering and engineering geology are closely related, and have large areas of overlap.
However, the field of geotechnical engineering is a specialty of engineering , where the field of engineering geology is a specialty of geology.
Coming from the fields of engineering and science, respectively, the two may approach the same subject, such as soil classification, with different methods. Humans have historically used soil as a material for flood control, irrigation purposes, burial sites, building foundations, and as construction material for buildings. First activities were linked to irrigation and flood control, as demonstrated by traces of dykes, dams, and canals dating back to at least BCE that were found in ancient Egypt , ancient Mesopotamia and the Fertile Crescent , as well as around the early settlements of Mohenjo Daro and Harappa in the Indus valley.
As the cities expanded, structures were erected supported by formalized foundations; Ancient Greeks notably constructed pad footings and strip-and-raft foundations. Until the 18th century, however, no theoretical basis for soil design had been developed and the discipline was more of an art than a science, relying on past experience.
Several foundation-related engineering problems, such as the Leaning Tower of Pisa , prompted scientists to begin taking a more scientific-based approach to examining the subsurface. The earliest advances occurred in the development of earth pressure theories for the construction of retaining walls. Henri Gautier, a French Royal Engineer, recognized the "natural slope" of different soils in , an idea later known as the soil's angle of repose.
A rudimentary soil classification system was also developed based on a material's unit weight, which is no longer considered a good indication of soil type. The application of the principles of mechanics to soils was documented as early as when Charles Coulomb a physicist, engineer, and army Captain developed improved methods to determine the earth pressures against military ramparts. In the 19th century Henry Darcy developed what is now known as Darcy's Law describing the flow of fluids in porous media.
Joseph Boussinesq a mathematician and physicist developed theories of stress distribution in elastic solids that proved useful for estimating stresses at depth in the ground; William Rankine , an engineer and physicist, developed an alternative to Coulomb's earth pressure theory. Albert Atterberg developed the clay consistency indices that are still used today for soil classification. Modern geotechnical engineering is said to have begun in with the publication of Erdbaumechanik by Karl Terzaghi a mechanical engineer and geologist.
Considered by many to be the father of modern soil mechanics and geotechnical engineering, Terzaghi developed the principle of effective stress, and demonstrated that the shear strength of soil is controlled by effective stress.
Terzaghi also developed the framework for theories of bearing capacity of foundations, and the theory for prediction of the rate of settlement of clay layers due to consolidation. The interrelationships between volume change behavior dilation, contraction, and consolidation and shearing behavior were all connected via the theory of plasticity using critical state soil mechanics by Roscoe, Schofield, and Wroth with the publication of "On the Yielding of Soils" in Critical state soil mechanics is the basis for many contemporary advanced constitutive models describing the behavior of soil.
Geotechnical centrifuge modeling is a method of testing physical scale models of geotechnical problems. The use of a centrifuge enhances the similarity of the scale model tests involving soil because the strength and stiffness of soil is very sensitive to the confining pressure.
The centrifugal acceleration allows a researcher to obtain large prototype-scale stresses in small physical models.
Geotechnical engineers are typically graduates of a four-year civil engineering program and some hold a masters degree. In the USA, geotechnical engineers are typically licensed and regulated as Professional Engineers PEs in most states; currently only California and Oregon have licensed geotechnical engineering specialties. GE certification in State governments will typically license engineers who have graduated from an ABET accredited school, passed the Fundamentals of Engineering examination, completed several years of work experience under the supervision of a licensed Professional Engineer, and passed the Professional Engineering examination.
In geotechnical engineering, soils are considered a three-phase material composed of: The voids of a soil, the spaces in between mineral particles, contain the water and air. The engineering properties of soils are affected by four main factors: Fine particles fines are defined as particles less than 0. Some of the important properties of soils that are used by geotechnical engineers to analyze site conditions and design earthworks, retaining structures, and foundations are: Geotechnical engineers and engineering geologists perform geotechnical investigations to obtain information on the physical properties of soil and rock underlying and sometimes adjacent to a site to design earthworks and foundations for proposed structures, and for repair of distress to earthworks and structures caused by subsurface conditions.
A geotechnical investigation will include surface exploration and subsurface exploration of a site. Sometimes, geophysical methods are used to obtain data about sites. Subsurface exploration usually involves in-situ testing two common examples of in-situ tests are the standard penetration test and cone penetration test. In addition site investigation will often include subsurface sampling and laboratory testing of the soil samples retrieved.
The digging of test pits and trenching particularly for locating faults and slide planes may also be used to learn about soil conditions at depth.
Large diameter borings are rarely used due to safety concerns and expense, but are sometimes used to allow a geologist or engineer to be lowered into the borehole for direct visual and manual examination of the soil and rock stratigraphy. A variety of soil samplers exist to meet the needs of different engineering projects.
The standard penetration test SPT , which uses a thick-walled split spoon sampler, is the most common way to collect disturbed samples. Piston samplers, employing a thin-walled tube, are most commonly used for the collection of less disturbed samples.
More advanced methods, such as ground freezing and the Sherbrooke block sampler, are superior, but even more expensive. Atterberg limits tests, water content measurements, and grain size analysis, for example, may be performed on disturbed samples obtained from thick walled soil samplers. Properties such as shear strength, stiffness hydraulic conductivity, and coefficient of consolidation may be significantly altered by sample disturbance.
To measure these properties in the laboratory, high quality sampling is required. Common tests to measure the strength and stiffness include the triaxial shear and unconfined compression test.
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Surface exploration can include geologic mapping , geophysical methods , and photogrammetry ; or it can be as simple as an engineer walking around to observe the physical conditions at the site. Geologic mapping and interpretation of geomorphology is typically completed in consultation with a geologist or engineering geologist.
Geophysical exploration is also sometimes used. A building's foundation transmits loads from buildings and other structures to the earth. In general, geotechnical engineers:. The primary considerations for foundation support are bearing capacity , settlement, and ground movement beneath the foundations.
Bearing capacity is the ability of the site soils to support the loads imposed by buildings or structures. Settlement occurs under all foundations in all soil conditions, though lightly loaded structures or rock sites may experience negligible settlements. For heavier structures or softer sites, both overall settlement relative to unbuilt areas or neighboring buildings, and differential settlement under a single structure, can be concerns. Of particular concern is settlement which occurs over time, as immediate settlement can usually be compensated for during construction.
Field instrumentation in geotechnical engineering
Ground movement beneath a structure's foundations can occur due to shrinkage or swell of expansive soils due to climatic changes, frost expansion of soil, melting of permafrost, slope instability, or other causes. Many building codes specify basic foundation design parameters for simple conditions, frequently varying by jurisdiction, but such design techniques are normally limited to certain types of construction and certain types of sites, and are frequently very conservative.
In areas of shallow bedrock, most foundations may bear directly on bedrock; in other areas, the soil may provide sufficient strength for the support of structures.
In areas of deeper bedrock with soft overlying soils, deep foundations are used to support structures directly on the bedrock; in areas where bedrock is not economically available, stiff "bearing layers" are used to support deep foundations instead. Shallow foundations are a type of foundation that transfers building load to the very near the surface, rather than to a subsurface layer. Shallow foundations typically have a depth to width ratio of less than 1.
Footings often called "spread footings" because they spread the load are structural elements which transfer structure loads to the ground by direct areal contact. Footings can be isolated footings for point or column loads, or strip footings for wall or other long line loads. A variant on spread footings is to have the entire structure bear on a single slab of concrete underlying the entire area of the structure.
Slabs must be thick enough to provide sufficient rigidity to spread the bearing loads somewhat uniformly, and to minimize differential settlement across the foundation.Until the 18th century, however, no theoretical basis for soil design had been developed and the discipline was more of an art than a science, relying on past experience.
Also, the unit weight of clean dry sand see Chapter 3 and ordi- nary earth were recommended to be Coefficientof gradation,C. In areas of deeper bedrock with soft overlying soils, deep foundations are used to support structures directly on the bedrock; in areas where bedrock is not economically available, stiff "bearing layers" are used to support deep foundations instead.
The pressureex- erted by ice becauseof volume cxpansionis str"clng cnough to break down even large rocks.
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