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84-487: The cushioning of water gives quicksand, and other liquefied sediments, a spongy, fluid-like texture. Objects in liquefied sand sink to the level at which the weight of the object is equal to the weight of the displaced soil/water mix and the submerged object floats due to its buoyancy. Soil liquefaction may occur in partially saturated soil when it is shaken by an earthquake or similar forces. The movement combined with an increase in pore pressure (of groundwater) leads to

168-577: A x {\displaystyle e_{max}} is the "maximum void ratio" corresponding to a very loose state, e m i n {\displaystyle e_{min}} is the "minimum void ratio" corresponding to a very dense state and e {\displaystyle e} is the in situ void ratio. Methods used to calculate relative density are defined in ASTM D4254-00(2006). Thus if D r = 100 % {\displaystyle D_{r}=100\%}

252-527: A change in pressure, or a shock initiates the liquefaction, causing the sand to form a suspension with each grain surrounded by a thin film of water. This cushioning gives quicksand, and other liquefied sediments, a spongy, fluidlike texture. Objects in the liquefied sand sink to the level at which the weight of the object is equal to the weight of the displaced sand/water mix and the object floats due to its buoyancy . Quick clay, known as Leda Clay in Canada ,

336-568: 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

420-569: A decrease in shear strength , i.e. reduction in effective stress . Deposits most susceptible to liquefaction are young ( Holocene -age, deposited within the last 10,000 years) sands and silts of similar grain size (well-sorted), in beds at least metres thick, and saturated with water. Such deposits are often found along stream beds , beaches , dunes , and areas where windblown silt ( loess ) and sand have accumulated. Examples of soil liquefaction include quicksand , quick clay, turbidity currents and earthquake-induced liquefaction. Depending on

504-439: A foot from quicksand at a speed of 1 cm/s would require the same amount of force as that needed to lift a car. It is impossible for a human to sink entirely into quicksand, due to the higher density of the fluid. Quicksand has a density of about 2 grams per cubic centimeter, whereas the density of the human body is only about 1 gram per cubic centimeter. At that level of density, sinking beyond about waist height in quicksand

588-432: A liquefied soil layer (termed 'lateral spreading'), opening large ground fissures , and can cause significant damage to buildings, bridges, roads and services such as water, natural gas, sewerage, power and telecommunications installed in the affected ground. Buried tanks and manholes may float in the liquefied soil due to buoyancy . Earth embankments such as flood levees and earth dams may lose stability or collapse if

672-542: A liquid (hence 'liquefaction'). Although the effects of soil liquefaction have been long understood, engineers took more notice after the 1964 Alaska earthquake and 1964 Niigata earthquake . It was a major cause of the destruction produced in San Francisco 's Marina District during the 1989 Loma Prieta earthquake , and in the Port of Kobe during the 1995 Great Hanshin earthquake . More recently soil liquefaction

756-430: A mixture of gravel and fine sand, with no coarse sand, the sample may be gap graded . Uniformly graded and gap graded soils are both considered to be poorly graded . There are many methods for measuring particle-size distribution . The two traditional methods are sieve analysis and hydrometer analysis. The size distribution of gravel and sand particles are typically measured using sieve analysis. The formal procedure

840-415: A mixture of particles of different size, shape and mineralogy. Because the size of the particles obviously has a significant effect on the soil behavior, the grain size and grain size distribution are used to classify soils. The grain size distribution describes the relative proportions of particles of various sizes. The grain size is often visualized in a cumulative distribution graph which, for example, plots

924-417: A relatively large specific surface area. The specific surface area (SSA) is defined as the ratio of the surface area of particles to the mass of the particles. Clay minerals typically have specific surface areas in the range of 10 to 1,000 square meters per gram of solid. Due to the large surface area available for chemical, electrostatic, and van der Waals interaction, the mechanical behavior of clay minerals

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1008-422: A river bed. Wind blown soil deposits ( aeolian soils) also tend to be sorted according to their grain size. Erosion at the base of glaciers is powerful enough to pick up large rocks and boulders as well as soil; soils dropped by melting ice can be a well graded mixture of widely varying particle sizes. Gravity on its own may also carry particles down from the top of a mountain to make a pile of soil and boulders at

1092-407: A situation where other factors such as exposure (i.e., sun stroke , dehydration and hypothermia ), drowning in a rising tide or attacks by predatory or otherwise aggressive animals may harm a trapped person. Quicksand may be escaped by slow movement of the legs in order to increase viscosity of the fluid, and rotation of the body so as to float in the supine position (lying horizontally with

1176-579: A small but non-negligible amount of fines (5–12%) may be given a dual classification such as SW-SC . Clays and Silts, often called 'fine-grained soils', are classified according to their Atterberg limits ; the most commonly used Atterberg limits are the Liquid Limit (denoted by LL or w l {\displaystyle w_{l}} ), Plastic Limit (denoted by PL or w p {\displaystyle w_{p}} ), and Shrinkage Limit (denoted by SL ). The Liquid Limit

1260-419: A soil in a saturated loose state, and one which may generate significant pore water pressure on a change in load are the most likely to liquefy. This is because loose soil has the tendency to compress when sheared, generating large excess porewater pressure as load is transferred from the soil skeleton to adjacent pore water during undrained loading. As pore water pressure rises, a progressive loss of strength of

1344-414: A soil. As the transitions from one state to another are gradual, the tests have adopted arbitrary definitions to determine the boundaries of the states. The liquid limit is determined by measuring the water content for which a groove closes after 25 blows in a standard test. Alternatively, a fall cone test apparatus may be used to measure the liquid limit. The undrained shear strength of remolded soil at

1428-465: A suction effect that causes anyone or anything that walks into it to sink until fully submerged and risk drowning. This has led to the common misconception that humans can be completely immersed and drown in quicksand, which is impossible. According to a 2010 article by Slate , this gimmick had its heyday in the 1960s, when almost 3% of all films showed characters sinking in clay, mud, or sand. Soil liquefaction Soil liquefaction occurs when

1512-505: A sudden loss of support, which will result in drastic and irregular settlement of the building causing structural damage, including cracking of foundations and damage to the building structure, or leaving the structure unserviceable, even without structural damage. Where a thin crust of non-liquefied soil exists between building foundation and liquefied soil, a 'punching shear' type foundation failure may occur. Irregular settlement may break underground utility lines. The upward pressure applied by

1596-419: A variety of parameters used to describe the relative proportions of air, water and solid in a soil. This section defines these parameters and some of their interrelationships. The basic notation is as follows: V a {\displaystyle V_{a}} , V w {\displaystyle V_{w}} , and V s {\displaystyle V_{s}} represent

1680-546: Is quartz , also called silica , which has the chemical name silicon dioxide. The reason that feldspar is most common in rocks but silica is more prevalent in soils is that feldspar is much more soluble than silica. Silt , Sand , and Gravel are basically little pieces of broken rocks . According to the Unified Soil Classification System , silt particle sizes are in the range of 0.002 mm to 0.075 mm and sand particles have sizes in

1764-405: Is a common example of a residual soil. The common mechanisms of transport are the actions of gravity, ice, water, and wind. Wind blown soils include dune sands and loess . Water carries particles of different size depending on the speed of the water, thus soils transported by water are graded according to their size. Silt and clay may settle out in a lake, and gravel and sand collect at the bottom of

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1848-442: Is a soil test-based definition, usually performed via cyclic triaxial , cyclic direct simple shear , or cyclic torsional shear type apparatus. These tests are performed to determine a soil's resistance to liquefaction by observing the number of cycles of loading at a particular shear stress amplitude required to induce 'fails'. Failure here is defined by the aforementioned shear strain criteria. The term 'cyclic mobility' refers to

1932-461: Is a water-saturated gel , which in its solid form resembles highly sensitive clay . This clay has a tendency to change from a relatively stiff condition to a liquid mass when it is disturbed. This gradual change in appearance from solid to liquid is a process known as spontaneous liquefaction. The clay retains a solid structure despite its high-water content (up to 80% by volume), because surface tension holds water-coated flakes of clay together. When

2016-543: Is defined as the difference between the Liquid Limit and the Plastic Limit of the specimen; it is an indicator of how much water the soil particles in the specimen can absorb, and correlates with many engineering properties like permeability, compressibility, shear strength and others. Generally, the clay having high plasticity have lower permeability and also they are also difficult to be compacted. According to

2100-417: Is defined as the size for which 10% of the particle mass consists of finer particles. Sands and gravels that possess a wide range of particle sizes with a smooth distribution of particle sizes are called well graded soils. If the soil particles in a sample are predominantly in a relatively narrow range of sizes, the sample is uniformly graded . If a soil sample has distinct gaps in the gradation curve, e.g.,

2184-541: Is described in ASTM D6913-04(2009). A stack of sieves with accurately dimensioned holes between a mesh of wires is used to separate the particles into size bins. A known volume of dried soil, with clods broken down to individual particles, is put into the top of a stack of sieves arranged from coarse to fine. The stack of sieves is shaken for a standard period of time so that the particles are sorted into size bins. This method works reasonably well for particles in

2268-413: Is determined primarily by their Atterberg limits , not by their grain size. If it is important to determine the grain size distribution of fine-grained soils, the hydrometer test may be performed. In the hydrometer tests, the soil particles are mixed with water and shaken to produce a dilute suspension in a glass cylinder, and then the cylinder is left to sit. A hydrometer is used to measure the density of

2352-550: Is generally governed by the loading rate, soil permeability , pressure gradient , and boundary conditions . It is well known that for a sufficiently high seepage velocity, the governing flow law in porous media is nonlinear and does not follow Darcy's law. This fact has been recently considered in the studies of soil-pore fluid interaction for liquefaction modeling. A fully explicit dynamic finite element method has been developed for turbulent flow law. The governing equations have been expressed for saturated porous media based on

2436-425: Is impossible. Even objects with a higher density than quicksand will float on it if stationary. Aluminium, for example, has a density of about 2.7 grams per cubic centimeter, but a piece of aluminium will float on top of quicksand until motion causes the sand to liquefy. Continued or panicked movement, however, may cause a person to sink further in the quicksand. Since this increasingly impairs movement, it can lead to

2520-892: Is primarily derived from friction between the particles and interlocking, which are very sensitive to the effective stress. The article concludes with some examples of applications of the principles of soil mechanics such as slope stability, lateral earth pressure on retaining walls, and bearing capacity of foundations. The primary mechanism of soil creation is the weathering of rock. All rock types ( igneous rock , metamorphic rock and sedimentary rock ) may be broken down into small particles to create soil. Weathering mechanisms are physical weathering, chemical weathering, and biological weathering Human activities such as excavation, blasting, and waste disposal, may also create soil. Over geologic time, deeply buried soils may be altered by pressure and temperature to become metamorphic or sedimentary rock, and if melted and solidified again, they would complete

2604-470: Is the Aberfan disaster . Casagrande referred to this type of phenomena as 'flow liquefaction' although a state of zero effective stress is not required for this to occur. 'Cyclic liquefaction' is the state of soil when large shear strains have accumulated in response to cyclic loading. A typical reference strain for the approximate occurrence of zero effective stress is 5% double amplitude shear strain. This

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2688-474: Is the ratio of the volume of voids to the volume of solids: Porosity , n {\displaystyle n} , is the ratio of volume of voids to the total volume, and is related to the void ratio: Degree of saturation , S {\displaystyle S} , is the ratio of the volume of water to the volume of voids: From the above definitions, some useful relationships can be derived by use of basic algebra. Geotechnical engineers classify

2772-405: Is the water content at which the soil behavior transitions from a plastic solid to a liquid. The Plastic Limit is the water content at which the soil behavior transitions from that of a plastic solid to a brittle solid. The Shrinkage Limit corresponds to a water content below which the soil will not shrink as it dries. The consistency of fine grained soil varies in proportional to the water content in

2856-412: Is very sensitive to the amount of pore fluid available and the type and amount of dissolved ions in the pore fluid. The minerals of soils are predominantly formed by atoms of oxygen, silicon, hydrogen, and aluminum, organized in various crystalline forms. These elements along with calcium, sodium, potassium, magnesium, and carbon constitute over 99 per cent of the solid mass of soils. Soils consist of

2940-514: The 1929 Grand Banks earthquake that struck the continental slope off the coast of Newfoundland . Minutes later, transatlantic telephone cables began breaking sequentially, further and further downslope, away from the epicenter . Twelve cables were snapped in a total of 28 places. Exact times and locations were recorded for each break. Investigators suggested that a 60-mile-per-hour (100 km/h) submarine landslide or turbidity current of water-saturated sediments swept 400 miles (600 km) down

3024-480: The Unified Soil Classification System (USCS), silts and clays are classified by plotting the values of their plasticity index and liquid limit on a plasticity chart. The A-Line on the chart separates clays (given the USCS symbol C ) from silts (given the symbol M ). LL=50% separates high plasticity soils (given the modifier symbol H ) from low plasticity soils (given the modifier symbol L ). A soil that plots above

3108-497: The Unified Soil Classification System , a #4 sieve (4 openings per inch) having 4.75 mm opening size separates sand from gravel and a #200 sieve with an 0.075 mm opening separates sand from silt and clay. According to the British standard, 0.063 mm is the boundary between sand and silt, and 2 mm is the boundary between sand and gravel. The classification of fine-grained soils, i.e., soils that are finer than sand,

3192-633: The continental slope from the earthquake's epicenter, snapping the cables as it passed. [REDACTED] Media related to Soil liquefaction at Wikimedia Commons Soil mechanics 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 (usually air and water) and particles (usually clay , silt , sand , and gravel ) but soil may also contain organic solids and other matter. Along with rock mechanics , soil mechanics provides

3276-413: The effective stress ( shear strength ) of soil is reduced to essentially zero. This may be initiated by either monotonic loading (i.e., a single, sudden occurrence of a change in stress – examples include an increase in load on an embankment or sudden loss of toe support) or cyclic loading (i.e., repeated changes in stress condition – examples include wave loading or earthquake shaking). In both cases

3360-538: The A-line and has LL>50% would, for example, be classified as CH . Other possible classifications of silts and clays are ML , CL and MH . If the Atterberg limits plot in the"hatched" region on the graph near the origin, the soils are given the dual classification 'CL-ML'. The effects of the water content on the strength of saturated remolded soils can be quantified by the use of the liquidity index , LI : When

3444-446: The LI is 1, remolded soil is at the liquid limit and it has an undrained shear strength of about 2 kPa. When the soil is at the plastic limit , the LI is 0 and the undrained shear strength is about 200 kPa. The density of sands (cohesionless soils) is often characterized by the relative density, D r {\displaystyle D_{r}} where: e m

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3528-429: The USCS, gravels (given the symbol G ) and sands (given the symbol S ) are classified according to their grain size distribution. For the USCS, gravels may be given the classification symbol GW (well-graded gravel), GP (poorly graded gravel), GM (gravel with a large amount of silt), or GC (gravel with a large amount of clay). Likewise sands may be classified as being SW , SP , SM or SC . Sands and gravels with

3612-614: The arrangement of particles in a load carrying framework as well as the pore size and pore fluid distributions. Engineering geologists also classify soils based on their genesis and depositional history. In the US and other countries, the Unified Soil Classification System (USCS) is often used for soil classification. Other classification systems include the British Standard BS 5930 and the AASHTO soil classification system. In

3696-420: The base; soil deposits transported by gravity are called colluvium . The mechanism of transport also has a major effect on the particle shape. For example, low velocity grinding in a river bed will produce rounded particles. Freshly fractured colluvium particles often have a very angular shape. Silts, sands and gravels are classified by their size, and hence they may consist of a variety of minerals. Owing to

3780-456: The case of flowing underground water, the force of the water flow opposes the force of gravity, causing the granules of sand to be more buoyant. In the case of earthquakes, the shaking force can increase the pressure of shallow groundwater, liquefying sand and silt deposits. In both cases, the liquefied surface loses strength, causing buildings or other objects on that surface to sink or fall over. The saturated sediment may appear quite solid until

3864-468: The cohesionless soil to liquefaction will depend on the density of the soil, confining stresses, soil structure (fabric, age and cementation ), the magnitude and duration of the cyclic loading, and the extent to which shear stress reversal occurs. Three parameters are needed to assess liquefaction potential using the simplified empirical method : The interaction between the solid skeleton and pore fluid flow has been considered by many researchers to model

3948-525: The density of the mixture minus the density of water is useful if the soil is submerged under water: where ρ w {\displaystyle \rho _{w}} is the density of water Water Content , w {\displaystyle w} is the ratio of mass of water to mass of solid. It is easily measured by weighing a sample of the soil, drying it out in an oven and re-weighing. Standard procedures are described by ASTM. Void ratio , e {\displaystyle e} ,

4032-462: The density of the mixture, i.e., the total mass of air, water, solids divided by the total volume of air water and solids (the mass of air is assumed to be zero for practical purposes): Dry Density , ρ d {\displaystyle \rho _{d}} , is the mass of solids divided by the total volume of air water and solids: Buoyant Density , ρ ′ {\displaystyle \rho '} , defined as

4116-444: The early points of concentration were liquefied. The phenomenon is most often observed in saturated, loose (low density or uncompacted), sandy soils. This is because a loose sand has a tendency to compress when a load is applied. Dense sands, by contrast, tend to expand in volume or ' dilate '. If the soil is saturated by water, a condition that often exists when the soil is below the water table or sea level , then water fills

4200-622: The extension of the Biot formulation. The elastoplastic behavior of soil under earthquake loading has been simulated using a generalized plasticity theory that is composed of a yield surface along with a non-associated flow rule. Pressures generated during large earthquakes can force underground water and liquefied sand to the surface. This can be observed at the surface as effects known alternatively as " sand boils ", "sand blows" or " sand volcanoes ". Such earthquake ground deformations can be categorized as primary deformation if located on or close to

4284-437: The face and torso facing up). The quicksands were of great extent at low water, and had an infamous reputation in the country. Close in shore, between the islet and the promontory, it was said that they would swallow a man in four minutes and a half; but there may have been little ground for this precision. Quicksand is a trope of adventure fiction , particularly in film, where it is typically and unrealistically depicted with

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4368-414: The gaps between soil grains ('pore spaces'). In response to soil compressing, the pore water pressure increases and the water attempts to flow out from the soil to zones of low pressure (usually upward towards the ground surface). However, if the loading is rapidly applied and large enough, or is repeated many times (e.g., earthquake shaking, storm wave loading) such that the water does not flow out before

4452-408: The genesis and composition of soil, the distinction between pore water pressure and inter-granular effective stress , capillary action of fluids in the soil pore spaces, soil classification , seepage and permeability , time dependent change of volume due to squeezing water out of tiny pore spaces, also known as consolidation , shear strength and stiffness of soils. The shear strength of soils

4536-475: The geologic cycle by becoming igneous rock. Physical weathering includes temperature effects, freeze and thaw of water in cracks, rain, wind, impact and other mechanisms. Chemical weathering includes dissolution of matter composing a rock and precipitation in the form of another mineral. Clay minerals, for example can be formed by weathering of feldspar , which is the most common mineral present in igneous rock. The most common mineral constituent of silt and sand

4620-525: The ground surface. Studies of liquefaction features left by prehistoric earthquakes, called paleoliquefaction or paleoseismology , can reveal information about earthquakes that occurred before records were kept or accurate measurements could be taken. Soil liquefaction induced by earthquake shaking is a major contributor to urban seismic risk . The effects of soil liquefaction on the built environment can be extremely damaging. Buildings whose foundations bear directly on sand which liquefies will experience

4704-402: The horizontal. One positive aspect of soil liquefaction is the tendency for the effects of earthquake shaking to be significantly damped (reduced) for the remainder of the earthquake. This is because liquids do not support a shear stress and so once the soil liquefies due to shaking, subsequent earthquake shaking (transferred through ground by shear waves ) is not transferred to buildings at

4788-427: The initial void ratio , the soil material can respond to loading either strain-softening or strain-hardening. Strain-softened soils, e.g., loose sands, can be triggered to collapse, either monotonically or cyclically, if the static shear stress is greater than the ultimate or steady-state shear strength of the soil. In this case flow liquefaction occurs, where the soil deforms at a low constant residual shear stress. If

4872-414: The liquid limit is approximately 2 kPa. The Plastic Limit is the water content below which it is not possible to roll by hand the soil into 3 mm diameter cylinders. The soil cracks or breaks up as it is rolled down to this diameter. Remolded soil at the plastic limit is quite stiff, having an undrained shear strength of the order of about 200 kPa. The Plasticity Index of a particular soil specimen

4956-430: The loss of particle cohesion , causing buildings or other objects on that surface to sink. Quicksand is a shear thinning non-Newtonian fluid : when undisturbed, it often appears to be solid (" gel " form), but a less than 1% change in the stress on the quicksand will cause a sudden decrease in its viscosity (" sol " form). After an initial disturbance—such as a person attempting to walk on it—the water and sand in

5040-641: The mass, M, by the acceleration due to gravity, g; e.g., W s = M s g {\displaystyle W_{s}=M_{s}g} Specific Gravity is the ratio of the density of one material compared to the density of pure water ( ρ w = 1 g / c m 3 {\displaystyle \rho _{w}=1g/cm^{3}} ). Specific gravity of solids , G s = ρ s ρ w {\displaystyle G_{s}={\frac {\rho _{s}}{\rho _{w}}}} Note that specific weight , conventionally denoted by

5124-433: The masses of air, water and solids in a soil mixture; ρ a {\displaystyle \rho _{a}} , ρ w {\displaystyle \rho _{w}} , and ρ s {\displaystyle \rho _{s}} represent the densities of the constituents (air, water and solids) in a soil mixture; Note that the weights, W, can be obtained by multiplying

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5208-609: The material comprising the embankment or its foundation liquefies. Over geological time, liquefaction of soil material due to earthquakes could provide a dense parent material in which the fragipan may develop through pedogenesis. Mitigation methods have been devised by earthquake engineers and include various soil compaction techniques such as vibro compaction (compaction of the soil by depth vibrators), dynamic compaction , and vibro stone columns . These methods densify soil and enable buildings to avoid soil liquefaction. Existing buildings can be mitigated by injecting grout into

5292-408: The material softening associated with the liquefaction phenomenon. The dynamic performance of saturated porous media depends on the soil-pore fluid interaction. When the saturated porous media is subjected to strong ground shaking, pore fluid movement relative to the solid skeleton is induced. The transient movement of pore fluid can significantly affect the redistribution of pore water pressure, which

5376-435: 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

5460-716: The mechanism of progressive reduction of effective stress due to cyclic loading. This may occur in all soil types including dense soils. However, on reaching a state of zero effective stress such soils immediately dilate and regain strength. Thus, shear strains are significantly less than a true state of soil liquefaction. Liquefaction is more likely to occur in loose to moderately saturated granular soils with poor drainage , such as silty sands or sands and gravels containing impermeable sediments . During wave loading , usually cyclic undrained loading, e.g. seismic loading , loose sands tend to decrease in volume , which produces an increase in their pore water pressures and consequently

5544-411: The movement of liquefied soil through the crust layer can crack weak foundation slabs and enter buildings through service ducts and may allow water to damage building contents and electrical services. Bridges and large buildings constructed on pile foundations may lose support from the adjacent soil and buckle or come to rest at a tilt. Sloping ground and ground next to rivers and lakes may slide on

5628-507: The next cycle of load is applied, the water pressures may build to the extent that it exceeds the force ( contact stresses ) between the grains of soil that keep them in contact. These contacts between grains are the means by which the weight from buildings and overlying soil layers is transferred from the ground surface to layers of soil or rock at greater depths. This loss of soil structure causes it to lose its strength (the ability to transfer shear stress ), and it may be observed to flow like

5712-454: The percentage of particles finer than a given size as a function of size. The median grain size, D 50 {\displaystyle D_{50}} , is the size for which 50% of the particle mass consists of finer particles. Soil behavior, especially the hydraulic conductivity , tends to be dominated by the smaller particles, hence, the term "effective size", denoted by D 10 {\displaystyle D_{10}} ,

5796-453: The quicksand separate and dense regions of sand sediment form; it is because of the formation of these high volume fraction regions that the viscosity of the quicksand seems to decrease suddenly. Someone stepping on it will start to sink. To move within the quicksand, a person or object must apply sufficient pressure on the compacted sand to re-introduce enough water to liquefy it. The forces required to do this are quite large: to remove

5880-447: The range of 0.075 mm to 4.75 mm. Gravel particles are broken pieces of rock in the size range 4.75 mm to 100 mm. Particles larger than gravel are called cobbles and boulders. Soil deposits are affected by the mechanism of transport and deposition to their location. Soils that are not transported are called residual soils —they exist at the same location as the rock from which they were generated. Decomposed granite

5964-415: The ruptured fault, or distributed deformation if located at considerable distance from the ruptured fault. The other common observation is land instability – cracking and movement of the ground down slope or towards unsupported margins of rivers, streams, or the coast. The failure of ground in this manner is called 'lateral spreading' and may occur on very shallow slopes with angles only 1 or 2 degrees from

6048-401: The sand and gravel size range. Fine particles tend to stick to each other, and hence the sieving process is not an effective method. If there are a lot of fines (silt and clay) present in the soil it may be necessary to run water through the sieves to wash the coarse particles and clods through. A variety of sieve sizes are available. The boundary between sand and silt is arbitrary. According to

6132-469: The soil occurs as effective stress is reduced. Liquefaction is more likely to occur in sandy or non-plastic silty soils but may in rare cases occur in gravels and clays (see quick clay ). A 'flow failure' may initiate if the strength of the soil is reduced below the stresses required to maintain the equilibrium of a slope or footing of a structure. This can occur due to monotonic loading or cyclic loading and can be sudden and catastrophic. A historical example

6216-409: The soil particle types by performing tests on disturbed (dried, passed through sieves, and remolded) samples of the soil. This provides information about the characteristics of the soil grains themselves. Classification of the types of grains present in a soil does not account for important effects of the structure or fabric of the soil, terms that describe compactness of the particles and patterns in

6300-601: The soil strain-hardens, e.g., moderately dense to dense sand, flow liquefaction will generally not occur. However, cyclic softening can occur due to cyclic undrained loading, e.g., earthquake loading. Deformation during cyclic loading depends on the density of the soil, the magnitude and duration of the cyclic loading, and amount of shear stress reversal. If stress reversal occurs, the effective shear stress could reach zero, allowing cyclic liquefaction to take place. If stress reversal does not occur, zero effective stress cannot occur, and cyclic mobility takes place. The resistance of

6384-572: The soil to stabilize the layer of soil that is subject to liquefaction. Another method called IPS (Induced Partial Saturation) is now practicable to apply on larger scale. In this method, the saturation degree of the soil is decreased. Quicksand forms when water saturates an area of loose sand, and the sand is agitated. When the water trapped in the batch of sand cannot escape, it creates liquefied soil that can no longer resist force. Quicksand can be formed by standing or (upwards) flowing underground water (as from an underground spring), or by earthquakes. In

6468-584: The stability of quartz compared to other rock minerals, quartz is the most common constituent of sand and silt. Mica, and feldspar are other common minerals present in sands and silts. The mineral constituents of gravel may be more similar to that of the parent rock. The common clay minerals are montmorillonite or smectite , illite , and kaolinite or kaolin. These minerals tend to form in sheet or plate like structures, with length typically ranging between 10  m and 4x10  m and thickness typically ranging between 10  m and 2x10  m, and they have

6552-682: The structure is broken by a shock or sufficient shear, it enters a fluid state. Quick clay is found only in northern countries such as Russia , Canada , Alaska in the U.S., Norway , Sweden and Finland , which were glaciated during the Pleistocene epoch . Quick clay has been the underlying cause of many deadly landslides . In Canada alone, it has been associated with more than 250 mapped landslides. Some of these are ancient, and may have been triggered by earthquakes. Submarine landslides are turbidity currents and consist of water-saturated sediments flowing downslope. An example occurred during

6636-482: The suburb of Balaroa and Petobo village 3 metres (9.8 ft) deep in mud. The government of Indonesia is considering designating the two neighborhoods of Balaroa and Petobo, that have been totally buried under mud, as mass graves. The building codes in many countries require engineers to consider the effects of soil liquefaction in the design of new buildings and infrastructure such as bridges, embankment dams and retaining structures. Soil liquefaction occurs when

6720-624: The suspension as a function of time. Clay particles may take several hours to settle past the depth of measurement of the hydrometer. Sand particles may take less than a second. Stokes' law provides the theoretical basis to calculate the relationship between sedimentation velocity and particle size. ASTM provides the detailed procedures for performing the Hydrometer test. Clay particles can be sufficiently small that they never settle because they are kept in suspension by Brownian motion , in which case they may be classified as colloids . There are

6804-406: The symbol γ {\displaystyle \gamma } may be obtained by multiplying the density ( ρ {\displaystyle \rho } ) of a material by the acceleration due to gravity, g {\displaystyle g} . Density , Bulk Density , or Wet Density , ρ {\displaystyle \rho } , are different names for

6888-659: 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 , and hydrology . This article describes

6972-525: The volumes of air, water and solids in a soil mixture; W a {\displaystyle W_{a}} , W w {\displaystyle W_{w}} , and W s {\displaystyle W_{s}} represent the weights of air, water and solids in a soil mixture; M a {\displaystyle M_{a}} , M w {\displaystyle M_{w}} , and M s {\displaystyle M_{s}} represent

7056-550: Was largely responsible for extensive damage to residential properties in the eastern suburbs and satellite townships of Christchurch during the 2010 Canterbury earthquake and more extensively again following the Christchurch earthquakes that followed in early and mid-2011 . On 28 September 2018, an earthquake of 7.5 magnitude hit the Central Sulawesi province of Indonesia. Resulting soil liquefaction buried

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