Geotechnical engineering is the branch of civil engineering concerned with the engineering behavior of earth materials. It uses the principles of soil mechanics and rock mechanics for the solution of its respective engineering problems. It also relies on knowledge of geology, hydrology, geophysics, and other related sciences. Geotechnical (rock) engineering is a subdiscipline of geological engineering.
Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated slope failures, mudflows, and debris flows. Landslides occur in a variety of environments, characterized by either steep or gentle slope gradients, from mountain ranges to coastal cliffs or even underwater, in which case they are called submarine landslides. Gravity is the primary driving force for a landslide to occur, but there are other factors affecting slope stability that produce specific conditions that make a slope prone to failure. In many cases, the landslide is triggered by a specific event, although this is not always identifiable.
Soil liquefaction occurs when a cohesionless saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress such as shaking during an earthquake or other sudden change in stress condition, in which material that is ordinarily a solid behaves like a liquid. In soil mechanics, the term "liquefied" was first used by Allen Hazen in reference to the 1918 failure of the Calaveras Dam in California. He described the mechanism of flow liquefaction of the embankment dam as:
If the pressure of the water in the pores is great enough to carry all the load, it will have the effect of holding the particles apart and of producing a condition that is practically equivalent to that of quicksand... the initial movement of some part of the material might result in accumulating pressure, first on one point, and then on another, successively, as the early points of concentration were liquefied.
Engineering geology is the application of geology to engineering study for the purpose of assuring that the geological factors regarding the location, design, construction, operation and maintenance of engineering works are recognized and accounted for. Engineering geologists provide geological and geotechnical recommendations, analysis, and design associated with human development and various types of structures. The realm of the engineering geologist is essentially in the area of earth-structure interactions, or investigation of how the earth or earth processes impact human made structures and human activities.
A geologic hazard or geohazard is an adverse geologic condition capable of causing widespread damage or loss of property and life. These hazards are geological and environmental conditions and involve long-term or short-term geological processes. Geohazards can be relatively small features, but they can also attain huge dimensions and affect local and regional socio-economics to a large extent.
In physical geography, a channel is a type of landform consisting of the outline of a path of relatively shallow and narrow body of water or of other fluids, most commonly the confine of a river, river delta or strait. The word is cognate to canal, and sometimes takes this form, e.g. the Hood Canal.
Seismic retrofitting is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes. With better understanding of seismic demand on structures and with our recent experiences with large earthquakes near urban centers, the need of seismic retrofitting is well acknowledged. Prior to the introduction of modern seismic codes in the late 1960s for developed countries and late 1970s for many other parts of the world, many structures were designed without adequate detailing and reinforcement for seismic protection. In view of the imminent problem, various research work has been carried out. State-of-the-art technical guidelines for seismic assessment, retrofit and rehabilitation have been published around the world – such as the ASCE-SEI 41 and the New Zealand Society for Earthquake Engineering (NZSEE)'s guidelines. These codes must be regularly updated; the 1994 Northridge earthquake brought to light the brittleness of welded steel frames, for example.
Mass wasting, also known as mass movement, is a general term for the movement of rock or soil down slopes under the force of gravity. It differs from other processes of erosion in that the debris transported by mass wasting is not entrained in a moving medium, such as water, wind, or ice. Types of mass wasting include creep, solifluction, rockfalls, debris flows, and landslides, each with its own characteristic features, and taking place over timescales from seconds to hundreds of years. Mass wasting occurs on both terrestrial and submarine slopes, and has been observed on Earth, Mars, Venus, Jupiter's moons Io, and on many other bodies in the Solar System.
Soil mechanics is a branch of soil physics and applied mechanics that describes the behavior of soils. It differs from fluid mechanics and solid mechanics in the sense that soils consist of a heterogeneous mixture of fluids and particles but soil may also contain organic solids and other matter. Along with rock mechanics, soil mechanics provides the theoretical basis for analysis in geotechnical engineering, a subdiscipline of civil engineering, and engineering geology, a subdiscipline of geology. Soil mechanics is used to analyze the deformations of and flow of fluids within natural and man-made structures that are supported on or made of soil, or structures that are buried in soils. Example applications are building and bridge foundations, retaining walls, dams, and buried pipeline systems. Principles of soil mechanics are also used in related disciplines such as geophysical engineering, coastal engineering, agricultural engineering, hydrology and soil physics.
A concrete slab is a common structural element of modern buildings, consisting of a flat, horizontal surface made of cast concrete. Steel-reinforced slabs, typically between 100 and 500 mm thick, are most often used to construct floors and ceilings, while thinner mud slabs may be used for exterior paving (see below).
A rockslide is a type of landslide caused by rock failure in which part of the bedding plane of failure passes through compacted rock and material collapses en masse and not in individual blocks. Note that a rockslide is similar to an avalanche because they are both slides of debris that can bury a piece of land. While a landslide occurs when loose dirt or sediment falls down a slope, a rockslide occurs only when solid rocks are transported down slope. The rocks tumble downhill, loosening other rocks on their way and smashing everything in their path. Fast-flowing rock slides or debris slides behave similarly to snow avalanches, and are often referred to as rock avalanches or debris avalanches.
Sir Alec Westley Skempton was an English civil engineer internationally recognised, along with Karl Terzaghi, as one of the founding fathers of the engineering discipline of soil mechanics. He established the soil mechanics course at Imperial College London, where the Civil and Environmental Engineering Department's building was renamed after him in 2004, and was knighted in the 2000 New Year Honours for services to engineering. He was also a notable contributor on the history of British civil engineering.
A mudflow or mud flow is a form of mass wasting involving fast-moving flow of debris that has become liquified by the addition of water. Such flows can move at speeds ranging from 3 meters/minute to 5 meters/second. Mudflows contain a significant proportion of clay, which makes them more fluid than debris flows, allowing them to travel farther and across lower slope angles. Both types of flow are generally mixtures of particles with a wide range of sizes, which typically become sorted by size upon deposition.
On 17 February 2006, a massive rock slide-debris avalanche occurred in the Philippine province of Southern Leyte, causing widespread damage and loss of life. The deadly landslide followed a 10-day period of heavy rain and a minor earthquake. The official death toll was 1,126.
Internal erosion is the formation of voids within a soil caused by the removal of material by seepage. It is the second most common cause of failure in levees and one of the leading causes of failures in earth dams, responsible for about half of embankment dam failures.
Sand boils or sand volcanoes occur when water under pressure wells up through a bed of sand. The water looks like it is boiling up from the bed of sand, hence the name.
There have been known various classifications of landslides. Broad definitions include forms of mass movement that narrower definitions exclude. For example, the McGraw-Hill Encyclopedia of Science and Technology distinguishes the following types of landslides:
Slope stability analysis is a static or dynamic, analytical or empirical method to evaluate the stability of earth and rock-fill dams, embankments, excavated slopes, and natural slopes in soil and rock. Slope stability refers to the condition of inclined soil or rock slopes to withstand or undergo movement. The stability condition of slopes is a subject of study and research in soil mechanics, geotechnical engineering and engineering geology. Analyses are generally aimed at understanding the causes of an occurred slope failure, or the factors that can potentially trigger a slope movement, resulting in a landslide, as well as at preventing the initiation of such movement, slowing it down or arresting it through mitigation countermeasures.
The Lower Greensand Group is a geological unit present across large areas of Southern England. It was deposited during the Aptian and Albian stages of the Early Cretaceous. It predominantly consists of sandstone and unconsolidated sand that were deposited in shallow marine conditions.
George Ter-Stepanian was a Soviet Armenian scientist in the field of soil mechanics and engineering geology, one of the founders of the landslide studies, and the originator of the theories of the depth creep of slopes, the structural composition of post-ice-age clay and suspension pressure acting against filtration. Ter-Stepanian was a member of the National Academy of Sciences of Armenia.
