Soil Behaviour And Critical State Soil Mechanics Pdf Sand

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Soil Mechanics In The Light Of Critical State Theories An Introduction

Refworks Account Login. UBC Theses and Dissertations. Featured Collection. Mahdi Taiebat, Professor, Civil Engineering, UBC Additional Examiner iii Abstract A newly designed and developed triaxial permeameter is presented, along with results from a series of commissioning tests for drained and undrained compression on uniformly graded Fraser River sand.

Results are compared to previous studies on Fraser River sand, with generally excellent agreement. The commissioning test series verify that the newly developed device is generating accurate and repeatable results. An experimental study was undertaken, using the triaxial device, to improve the understanding of the mechanics of gap-graded sandy soil. The effects of reconstitution method, density, and gradation on shear response are examined within a critical state framework for gap-graded BSM sand in drained triaxial compression tests.

The critical state of gap-gradations of BSM sand is found independent of reconstitution method and initial void ratio. The strength and void ratio at the critical state are dependent on the finer fraction content, as well as the size ratio of fine to coarse component in a gap-gradation. The findings are attributed to differences in packing characteristics and the relative contribution of each component fraction during shear. The Muir Wood grading state index is examined as a candidate parameter to quantify a change in the critical state with change in gradation, with promising results.

In , two sinkholes were discovered within the dam. The sinkholes are believed to be partially caused by water seeping from the reservoir to erode, with time, fractions of soil in the embankment dam; a phenomenon termed internal erosion. The current state of practice relies heavily on empiricism to assess the susceptibility of soil mixtures to internal erosion.

A mechanics-based understanding of the phenomenon is needed. A new test device with which to accomplish this has recently been designed, developed and commissioned at UBC.

This thesis details an experimental program undertaken to characterize strength parameters of soil mixtures of WAC Bennett Dam borrow source material believed susceptible to internal erosion. The results form a database with which tests on eroded soil can be compared to characterize how strength parameters are changed by internal erosion.

Jonathan Fannin, in collaboration with the research team of Dr. All other items in this thesis, including the identification and design of the research program, performance of the experimental work, and analysis of the research data is the original, unpublished, independent work of the author, Vincent McClelland, done in consultation with research advisor, Dr.

Jonathan Fannin. Bennett Dam Fannin, for his continuous support, guidance, and genuine interest in my professional development over the course of my time at UBC. I feel exceptionally lucky to have had the opportunity to work with him on this project.

I would like to thank my coworkers past and present on the UBC internal erosion research team; A. Antunes, S. Ataii, V. Ganapathiraman, Dr. Slangen, and A. Swerid for their collaboration, feedback and support. In particular I would like to thank S. Ataii and Dr. Slangen for their work designing and developing the test device used in this thesis.

I wish to express my gratitude to Dr. Vaid, for his interest and feedback on elements of test equipment, test methodology, and data interpretation. It has been a privilege to learn from such a knowledgeable and esteemed member of the geotechnical engineering field. Schremp, S. Jackson, B. Leung, D. Hudniuk, and S. Lee, to fabricate and troubleshoot elements of the test device is acknowledged with gratitude. The feedback and collaboration of Dr. Hartford and S. Garner are deeply appreciated.

I would like to thank Dr. Taiebat for his feedback as the additional examiner of this thesis. Finally, I wish to express gratitude to Dr. Verdugo, for answering questions related to test equipment and methodology posed via my supervisor, Dr. Fannin, and for providing me with a copy of his thesis, which I found to be a valuable source of reference. In , two sinkholes were discovered within the core of the dam.

The sinkholes are thought to be caused in part by finer fraction migration due to internal instability Stewart and Garner , a phenomenon whereby seepage flow removes a finer fraction of the soil gradation. Empirical methods provide a means to assess the susceptibility of a zoned gradation to erosion by internal instability. The empirical methods, whilst useful as a screening-tool, are not a substitute for a physically-based analytical model of soil behavior. Accordingly, there is need to develop a mechanics-based understanding of seepage-induced internal instability.

Critical state soil mechanics Schofield and Wroth has successfully been used in the world of liquefaction as a mechanics based modelling framework. Critical state constitutive modelling approaches have been proposed by Muir Wood et al. Muir Wood et al. The critical state is well studied for uniformly graded sands susceptible to liquefaction e. Verdugo and Ishihara , Been et al.

Fewer studies have been performed on gap-graded sand or sand-silt mixtures e. Very few studies have been performed on gap-gradations susceptible to internal instability, with comparison between eroded and uneroded material e.

A comprehensive characterization of uneroded and eroded materials within a critical state framework is a potential method to develop a mechanics based understanding of the mechanical consequences of internal erosion.

The Coursier dam, near Revelstoke, BC, was decommissioned in due in part to several sinkholes thought to be caused by internal instability within a gap-graded fluvial foundation unit Crawford-Flett The compacted fill of the body, and fluvial units within the foundation of an embankment dam have differences in fabric and structure.

Fabric is well studied for uniformly graded sands e. Oda , Oda et al. Initiation of internal erosion is thought to be dependent on a combination of stress, hydraulic load and material susceptibility Garner and Fannin The microstructure and fabric of a material partially controls its susceptibility to internal instability.

For binary mixtures of coarse and fine granular material, particle packing characteristics vary with percentage finer fraction content and size disparity between coarse and fine components Thevanayagam et al.

These test variables have important micromechanical implications regarding force chain contributions of different components and potential susceptibility to internal instability Shire et al. It is important to understand how varying these parameters also affects the shear response of gap-graded materials. The primary motivator for the current research is the Bennett dam, specifically the transition zone of the Bennett Dam, which is believed susceptible to internal instability Stewart and Garner The transition zone of the dam is immediately downstream of the core of the dam.

The current research is intended to establish a database of triaxial tests on uneroded gap-gradations of Bennett material believed potentially susceptible to internal instability. The findings provide a base case with which to compare shear data on eroded material in subsequent studies. In conjunction with this overarching goal, the objectives of the current study are to: I.

Characterize a new sand, Bennett South Moraine sand, within a critical state framework and benchmark it against other previously established materials. Examine differences in response due to differences in initial fabric arising from different methods of reconstitution.

Test the uniqueness of the critical state in triaxial compression for gap-graded Bennett South Moraine sand with respect to initial void ratio and reconstitution method. Examine how variations in microstructure affect critical state parameters VI. Examine modelling approaches to quantitatively describe changes in the critical state with changes in gradation 4 Chapter 2: Literature review This chapter summarizes the current body of knowledge pertinent to the present study.

Upon completion of construction in it was the highest zoned embankment dam in the world, and is classified as an extreme consequence dam. The dam impounds the km long Williston reservoir, one of the largest in North America Stewart and Watts The dam contains a large, central, non-plastic silty-sand core. Downstream and adjacent to the core is a gravelly-sand transition zone, followed by a sandy-gravel filter, and gravel drainage units chimney and blanket drains Figure 2.

The dam foundation consists of interlayered sandstone and shale bedrock units, and a grout curtain extends below the core into the bedrock foundation. The Dam was built primarily from a nearby moraine deposit, believed to be glacio-fluvial in origin Morgan and Harris It was noted prior to construction that the moraine material used in the body of the dam had a tendency for particle deficiencies within certain size ranges. These deficiencies were one of the reasons the moraine deposit was thought to be glacio-fluvial in nature, as this was thought to be a characteristic of fluvial deposits Morgan and Harris Difficulties placing material without segregation were reported at the time of construction Low and Lyell Quality control of construction relied on method specifications.

Mechanical sieving was performed on grab samples of processed material and results were relayed back to the blending facility to make necessary adjustments to prevent excessive placement of inadequate material; nevertheless material was 5 still being placed at record rates of approximately 6, cubic yards per hour, 24 hours a day Low and Lyell Construction records indicate that the average placed gradation of the transition zone appears to be gap-graded Low and Lyell Seepage flow is measured at several weir locations.

Weir flows vary annually and, with correction for the annual melt of snow cover on the embankment, exhibit a trend that is believed to correlate reasonably well with elevation of the reservoir surface Garner Pore water pressure is measured at several instrument-planes in the core of the dam. Piezometric levels rose steadily after first-filling to yield measured values that were considerably greater than expected values.

The pressures peaked between and , proceeded by a gradual decline towards anticipated values for steady state seepage Stewart and Garner

Soil mechanics

The application of critical state framework depends on the presence of either a unique critical state line CSL. However, many authors have observed that a transitional behaviour occurs in certain granular intermediate soils in which the fines content and the initial void ratio have a significant effect on the location of this line. This work investigates these effects in poorly graded granular soils as previous studies reported that this type of soil does not exhibit transitional behaviour. A unique state boundary surface is identified by determining the critical state parameters from each group and using these parameters to normalise the stress paths; this shows that the critical state framework can be successfully applied to this type of soil. This is a preview of subscription content, access via your institution. Rent this article via DeepDyve.

Instability of liquefaction is one of the major reasons which results in the failure of earth structure such as dam. The present study focuses on the simulation of static liquefaction behavior for granular materials such as sand and sand-silt mixtures. Based on micromechanical analysis of inter-particle behavior, a simple one-scale model is proposed to simulate the stress-strain response of sand; then the proposed model is extended to simulate the sand-silt mixtures using the mixture theory combining the properties of sand and silt according to their proportions. Empirical expressions are introduced to fit the critical state strength and the location of the critical state line for each mixture. Parameters of the model can be divided into two categories: the first seven parameters have the same values either with pure sand or pure silt for silt-sand with any given fines content; the other three parameters are the function of fines content and three more parameters are required to estimate their values. The predicted results of triaxial test of sand and sand-silt mixtures with different fine content, which has a good agreement with the results of laboratory tests, suggest that the proposed model can simulate static liquefaction behavior of sand and sand-silt mixtures. Instability of liquefaction is one of the major reasons which results in the failure of earth structures such as dam.

Nevertheless, the development of the critical state of sand matrix soils is lacking. This paper discusses the development of critical state lines and corresponding critical state parameters for the investigated material, sand matrix soils using sand-kaolin mixtures. The output of this paper can be used as an interpretation framework for the research on liquefaction susceptibility of sand matrix soils in the future. The strain controlled triaxial test apparatus was used to provide the monotonic loading onto the reconstituted soil specimens. All tested soils were subjected to isotropic consolidation and sheared under undrained condition until critical state was ascertain. Based on the results of 32 test specimens, the critical state lines for eight different sand matrix soils were developed together with the corresponding values of critical state parameters, , , and.

Critical State Soil Mechanics

The soil water content at the stage where the plant dies, is called permanent wilting point. The soil still contains some water, but it is too difficult for the roots to suck it from the soil see Fig. Some soil moisture characteristics.

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. 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. Principles of soil mechanics are also used in related disciplines such as geophysical engineering , coastal engineering , agricultural engineering , hydrology and soil physics. This article describes 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 particulate implementation of the discrete element method DEM can replicate many of the complex mechanical characteristics associated with sand. This research firstly shows that the CSSM framework is useful to assess whether a DEM simulation gives a response that is representative of a real soil. The influence of sample size on the critical-state response observed in DEM simulations that use rigid-wall boundaries was examined. The observed sensitivity was shown to be caused by higher void ratios and lower contact densities adjacent to the boundaries. True-triaxial simulations with different intermediate stress ratios b were performed.

Influence of Initial Void Ratio on Critical State Behaviour of Poorly Graded Fine Sands

Critical State of Sand Matrix Soils

Refworks Account Login. UBC Theses and Dissertations. Featured Collection. Mahdi Taiebat, Professor, Civil Engineering, UBC Additional Examiner iii Abstract A newly designed and developed triaxial permeameter is presented, along with results from a series of commissioning tests for drained and undrained compression on uniformly graded Fraser River sand.

PhD thesis, University of Nottingham. One of the greatest breakthroughs in soil mechanics was the development of Critical State Soil Mechanics CSSM in the s and s and the derivation of a continuum elasto-plastic constitutive model, namely Cam clay, which was the foundation for other continuum models for clays, and much later for sands. However, as yet there has been no micro mechanical analysis which explains the existence of such continuum models; such a micro perspective must take into account the discontinuous nature of soil. Without such insight, the engineer cannot understand which micro parameters affect soil behaviour.

 - Потом в его голосе зазвучали зловещие нотки.  - Но как только я узнаю, что вы следите за мной, я немедленно расскажу всю эту историю журналистам. Я расскажу, что Цифровая крепость - это большая липа, и отправлю на дно все ваше мерзкое ведомство. Стратмор мысленно взвешивал это предложение. Оно было простым и ясным.

Crooks, J.H.A., Becker, D.E., and Jefferies, M.G. (), 'The cone penetration test in sands: Part I, state parameter interpretation', Géotechnique 36 CrossRef |.

Soil mechanics

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Санта-Крус - самый старый район Севильи, где нет проездов между зданиями, лишь лабиринт узких ходов, восходящих еще к временам Древнего Рима. Протиснуться здесь могли в крайнем случае только пешеходы, проехал бы мопед. Беккер когда-то сам заблудился в его узких проходах. Набирая скорость на последнем отрезке Матеус-Гаго, он увидел впереди горой вздымающийся готический собор XI века. Рядом с собором на сто двадцать метров вверх, прямо в занимающуюся зарю, поднималась башня Гиральда.

 Мы успеем найти его партнера. - Думаю. У нас есть кое-какие данные. Танкадо неоднократно публично заявлял, что у него есть партнер. Наверное, этим он надеялся помешать производителям программного обеспечения организовать нападение на него и выкрасть пароль.

Он решил было обратиться в полицию - может быть, у них есть данные о рыжеволосых проститутках, - но Стратмор на этот счет выразился недвусмысленно: Вы должны оставаться невидимым. Никто не должен знать о существовании кольца. Может быть, стоит побродить по Триане, кварталу развлечений, и поискать там эту рыжую девицу. Или же обойти все рестораны - вдруг этот тучный немец окажется. Но и то и другое вряд ли к чему-то приведет. В его мозгу все время прокручивались слова Стратмора: Обнаружение этого кольца - вопрос национальной безопасности. Внутренний голос подсказывал Беккеру, что он что-то упустил - нечто очень важное, но он никак не мог сообразить, что .

 - Ты только подумай: ТРАНСТЕКСТ бьется над одним-единственным файлом целых восемнадцать часов. Слыханное ли это. Отправляйся домой, уже поздно. Она окинула его высокомерным взглядом и швырнула отчет на стол. - Я верю этим данным.

Стратмор пришел вчера с самого утра, и с тех пор его лифт не сдвинулся с места. Не видно, чтобы он пользовался электронной картой у главного входа. Поэтому он определенно .

 Проваливай и умри.

Беккер зашагал по комнате. - На руке умершего было золотое кольцо. Я хочу его забрать. - У м-меня его. Беккер покровительственно улыбнулся и перевел взгляд на дверь в ванную.

Сьюзан заколебалась, но все же поехала. По приезде группу сразу же разделили. Все они подверглись проверке на полиграф-машине, иными словами - на детекторе лжи: были тщательно проверены их родственники, изучены особенности почерка, и с каждым провели множество собеседований на всевозможные темы, включая сексуальную ориентацию и соответствующие предпочтения. Когда интервьюер спросил у Сьюзан, не занималась ли она сексом с животными, она с трудом удержалась, чтобы не выбежать из кабинета, но, так или иначе, верх взяли любопытство, перспектива работы на самом острие теории кодирования, возможность попасть во Дворец головоломок и стать членом наиболее секретного клуба в мире - Агентства национальной безопасности. Беккер внимательно слушал ее рассказ.

Чудесным образом Северная Дакота обнаружился прямо под носом и теперь попал в западню.


Ruby A.
28.05.2021 at 07:26 - Reply

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