Relationship between cyclic stress ratio causing liquefaction and n60 values for. Liquefaction is the phenomena when there is loss of strength in saturated and cohesionless soils because of increased pore water pressures and hence reduced effective stresses due to dynamic loading. Soil liquefaction, also called earthquake liquefaction, ground failure or loss of strength that causes otherwise solid soil to behave temporarily as a viscous liquid. Recent developments of soil improvement methods for. Evaluation of soil liquefaction potential for level ground. Soil liquefaction, ground failure or loss of strength that causes otherwise solid soil to behave temporarily as a viscous liquid. The first course in soil mechanicsgeotechnical engineering generally introduces.
Soil liquefaction is generally occurs in sand, silty sand and sandy silt soil 1. Soil dynamics video course civil engineering nptel. Soil liquefaction is defined as the transformation of a granular material from a solid into a liquefied state as a consequence of increased porewater pressures. The liquefaction of gases is a complicated process that uses various compressions and expansions to achieve high pressures and very low temperatures, using, for example, turboexpanders.
Soil can also be referred to as regolith, or loose rock material. The shaking results in the soil particles becoming suspended due to an increase in water pressure. In fact, much of the damage that occurs as a result of earthquakes is due to liquefaction. In terms of liquefaction mitigation, some relatively new concepts have been proposed such as passive. Liquefaction has been most abundant in areas where ground water lies within 10 m of the ground surface. Study on liquefaction of soil national institute of. Geotechnical engineering i notes pdf gte i notes pdf.
Pdf ce6405 soil mechanics sm books, lecture notes, 2marks. In this paper the field datas of two major earthquakes, namely chichi. Soil liquefaction analysis software novoliq novo tech software. Soil is formed from rock due to erosion and weathering action. General utilities lab techniques factors affecting.
It is based on a workshop held in dedham, massachusetts, on march 2830, 1985, at which liquefaction specialists from the united states. Deepankar choudhury, department of civil engineering, iit bombay, mumbai, india. The phenomenon occurs in watersaturated unconsolidated soils affected by seismic s waves secondary waves, which cause ground vibrations during earthquakes. The mechanism of liquefaction of clayey soils m124. Predicting soil liquefaction using soil survey data. If a soil layer is a fluvial, lacustrine or aeolian deposit of holocene age, a greater potential for liquefaction exists than for till, residual deposits, or older deposits fines content and plasticity index. To collect and classify soils and their physical properties on the basis of fundamental knowledge of soil mechanics. Following conditions are required for liquefaction to occur. The basic mechanisms of earthquakeinduced soil liquefaction are introduced by considering the shaking of a block on a thin granular layer, which mechanical behaviour is modelled with a.
Soil liquefaction during earthquakes the cliffs notes. These tilted buildings and liquefaction in this area are probably the most well known examples of liquefaction and loss of bearing strength. Weathering of rocks and types of soil, physical properties, e. Relationship between building characteristics, soil depth and damage potential coefficient s v k structure fundamental period damage intensity d r 2 to 3 storey 0. Unified modeling of flow liquefaction and cyclic mobility. Civil engineering geotechnical earthquake engineering nptel. This rapid evolution in the treatment of liquefaction has been pushed largely by a confluence of lessons and data.
In this paper the field datas of two major earthquakes, namely chichi, taiwan earthquake magnitude mw 7. Apr 08, 2015 2014 seed lecture developments in the assessment of liquefaction potential and its consequences duration. Purchase soil dynamics and liquefaction, volume 42 1st edition. Soil liquefaction engineering has evolved into a subfield in its own right, and engineering assessment and mitigation of seismic soil liquefaction hazard is increasingly well addressed in both research and practice. Sediments most susceptible to liquefaction include holocene less than 10,000yearold delta, river channel, flood plain, and aeolian deposits, and poorly compacted fills. Mod04 lec22 l22liquefaction, preliminary sceening, simplified.
Introduction liquefaction mechanics of liquefaction. It covers liquefaction assessment using various empirical methods, and estimation of postliquefaction lateral spread and reconsolidation settlement of the site. In terms of liquefaction mitigation, some relatively new concepts have been proposed such as passive site. Chapter 5 engineering properties of soil and rock 5.
Soil liquefaction occurs when the effective stress shear strength of soil is reduced to essentially zero. To develop suitable soil testing devices and soil testing methods. This water exerts a pressure on the soil particles that influences how tightly the particles themselves are pressed together. May 09, 2012 a brief explanation of soil liquefaction come see the accompanying article at. Cyclic mobility is a liquefaction phenomenon, triggered by cyclic loading, occurring in soil deposits with static shear stresses lower than the soil strength. Liquefaction occurs in saturated soils, that is, soils in which the space. A brief explanation of soil liquefaction come see the accompanying article at. Recent developments of soil improvement methods for seismic. Earthquake asics liquefaction what it is and what to.
Understanding the initiation of liquefaction identification of the state of the soil when. Soil dynamics and liquefaction, volume 42 1st edition. As a dynamic load is placed upon a saturated cohesionless soil the pore water pressure rises and, as a result, the effective stress reduces. Soil mechanics provide the theoretical basis for analysis in geotechnical engineering. A summary report, author seed, h b and arango, i and chan, c k, abstractnote the results of a threeyear research program conducted to investigate the settlement and liquefaction of sands under multidirectional shaking are evaluated. Soil sampling in general soil samples are categorized as shown in fig. Although earthquake shock is the best known cause of liquefaction. This movement can cause destruction of structures on the ground surface and settlement of the retained soil. Liquefaction means different things to different people use more specific technical terms to avoid confusion in technical discussions. These depend primarily on the nature of the soil grains, the current stress, the water content and unit weight. Novoliq is a powerful, userfriendly geotechnical software for soil liquefaction analysis. Liquefaction of soil during earthquakes maps, video. It is based on a workshop held in dedham, massachusetts, on march 2830, 1985, at. Visitors who are not familiar with soil liquefaction can find answer to typical questions below.
Tilted apartment buildings at kawagishi cho, niigata, japan. Liquefaction potential in a soil layer increases with decreasing fines content and plasticity of the soil. Oct 04, 2016 soil before liquefaction soil after liquefaction type of liquefaction 4. Variation of damping ratio of fine grained soils with cyclic shear strain amplitude and plasticity index after vucetic and dobry, 1991.
A procedure to estimate the liquefaction resistance of soils by means of swedish weight sounding tests is proposed. Soil liquefaction is the phenomenon in which the stiffness and the strength of the soil are lost under the action of earthquake force or due to rapid loading conditions. The phenomenon of liquefaction has been studied extensively over the past 40 years and substantial. The main objective of soil improvement techniques used for reducing liquefaction hazards is to large increases in pore water pressure during earthquake shaking by improving the strength, density, and drainage characteristics of soil. The structure of the soil is disturbed to the considerable degree by the action of the boring tools or the excavation equipments. Although traditional methods of liquefaction mitigation have been widely applied in engineering practice, some prominent problems remain such as limits on the size of the treated areas, disturbance of existing structures sensitive to deformation or vibration, and environmental impact. Soil liquefaction analysis software novoliq novo tech. Soil liquefaction occurs when a saturated or partially saturated soil substantially loses strength. Foundations are designed and constructed for structures of various sizes. Earthquake asics liquefaction what it is and what to do about it. The empirical formulae estimating the liquefaction resistance of soils r l directly from the penetration resistance, w sw and n sw, of swedish weight sounding tests are firstly derived by combining the correlation between the values for w sw and n sw and relative density d r and.
The soil in normal condition is closely packed to each other. Soil liquefaction occurs in saturated soils, that is, soils in which the space between individual particles is completely filled with water. The main triggers of this phenomenon are earthquakes. Liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. Liquefaction has been most abundant in areas where ground water lies within 10 m. Evaluation of liquefaction resistance of soils from. Dec 21, 2014 although traditional methods of liquefaction mitigation have been widely applied in engineering practice, some prominent problems remain such as limits on the size of the treated areas, disturbance of existing structures sensitive to deformation or vibration, and environmental impact. Flow liquefaction and cyclic mobility are two different phenomena that are encountered during strong earthquakes. Engineers are concerned with soil s mechanical properties. Soil liquefaction is the process by which saturated soil material loses its strength and can flow as a liquid. Critical state soil mechanics is a useful tool for appreciating the different behaviors of various soils over a range of densities and confining stresses.
Soil removed by this is disturbed but it is better than wash boring, percussion or rotary drilling. It is not suitable for very hard or cemented soils, very soft soils, as then the flow into the hole can occur and also for fully saturated cohesionless soil. Inertial soil structure interaction inertia from vibration of structure and foundation causes foundation translation and rotation u f and. Introduction to soil mechanics geotechnical engineering. The course also deals with various earthquake hazards including liquefaction, procedures to evaluate them. Liquefaction assessment geoconsult geotechnical engineers. It is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. Soil liquefaction occurs when a 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. Flow liquefaction was initiated at the instant it become irreversibly unstable i. The soil liquefaction web site was developed to provide general information for interested lay persons, and more detailed information for engineers. Liquefaction occurs when vibrations or water pressure within a mass of soil cause the soil particles to lose contact with one another. It occurs in saturated soils, which are subjected to shaking. Hence, a soils plasticity index is a better indicator.
Deformation due to cyclic mobility develop incrementally because of static and dynamic stresses. Liquefaction characteristics liquefaction is the loss of shear strength in saturated cohesionless soils that are subjected to a dynamic load coduto, 1999. Deepankar choudhury, department of civil engineering, iit bombay. Liquefaction and related phenomena have been responsible for tremendous amounts of damage in historical earthquakes around the world. Soil liquefaction can also exert higher pressure on retaining walls, which can cause them to slide or tilt. In this research effort, an empirical model was developed for predicting horizontal and vertical surface displacements due to liquefactioninduced lateral spreading. Further technical specifications of novoliq are presented below. The geotechnical engineering i notes pdf gte i notes pdf book starts with the topics covering soil formation soil structure and clay mineralogy, grain size analysis, soil water capillary rise flow of water through soils, neutral and effective stresses, immediate settlement primary consolidation and secondary consolidation stress. Engineers are concerned with soils mechanical properties.
The liquefaction of air is used to obtain nitrogen, oxygen, and argon and other atmospheric noble gases by separating the air components by fractional. Lecture31evaluation of liquefaction soil solid mechanics. Approaches for estimating liquefaction potential of soils. Presented also are the most widely accepted methods for evaluating the liquefaction potential of cohesionless oils in level ground, for estimating earthquakeinduced settlements and. As a result, the soil behaves like a liquid, has an inability to support weight and can flow down very gentle slopes. While the occurrence of soil liquefaction and lateral spreading can be predicted at a given site, methods are needed to estimate the magnitude of the resulting deformations. The liquefaction phenomenon of soil deposits can be described as the reduction of shear strength due to pore pressure buildup in the soil skeleton. Nptel syllabus geotechnical earthquake engineering video course course outline this course on geotechnical earthquake engineering introduces the fundamental concepts of earthquake engineering related to geotechnical problems, principles of earthquake, wave propagation, dynamic soil properties, liquefaction and seismic design of. Fce 311 geotechnical engineering lecture notes final2. The soil must be loosesoft to moderately densestiff. Jan 09, 2010 relationship between building characteristics, soil depth and damage potential coefficient s v k structure fundamental period damage intensity d r 2 to 3 storey 0.
It was found that an increase in clay content as well as the presence of bentonite clay raised the soil resistance to liquefaction. Lecture31 1 evaluation of liquefaction potential since the first widespread observations of liquefaction in the 1964 niigata and 1964 alaska earthquakes, liquefaction has been responsible for significant damage to buildings and bridges in numerous earthquakes. Flow liquefaction is associated with the contractive behavior of loose granular materials and cyclic mobility is associated with the dilative response of both loose and dense granular materials at low confining stresses. This definition avoids confusion between liquefaction and pos sible flowfailure conditions after liquefaction. To develop rational soil sampling devices and soil sampling methods. Download link is provided and students can download the anna university ce6405 soil mechanics sm syllabus question bank lecture notes syllabus part a 2 marks with answers part b 16 marks question bank with answer, all the materials are listed below for the students to make use of it and score good maximum marks with our study materials. The analysis of microstructures of bentonitesand mixtures along with the results from ringshear tests revealed that the soil microstructure is the key factor in determining the dynamic properties of soil. What is soil liquefaction university of washington. Nptel syllabus geotechnical earthquake engineering. The soil particles are closely packed due to the contact. The liquefaction phenomenon of soil deposits can be described as the reduction of shear strength. This paper presents the results of liquefaction potential evaluation for various sandy sites, with high seismic risk, where soil liquefaction is a major concern for all structures supported on. Soil liquefaction during earthquakes the cliffs notes version. Soil liquefaction occurs in a fully saturated soil.