No description available.

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<p>QC 20120703</p>

<p>The main aim of this PhD dissertation is to investigate the inherent and induced anisotropy in granular materials. The study includes both the experimental and theoretical aspects and provides a methodology for characterizing the mechanical response of granular materials that display anisotropy.</p> <p>The content of this thesis is divided into two main parts. The first part is focused on investigating the mechanical properties of materials with inherent anisotropy. In particular, an experimental program designed to investigate the mechanical properties of Ottawa standard sand (C109), with inherent anisotropy that is generated by the initial densification process, is described. The program involves a series of direct shear as well as triaxial axial tests. Its primary objective is to demonstrate that anisotropy may occur in sands that have nearly spherical particles (i.e. are typically considered as isotropic) provided the distribution of pore space has a preferred orientation due to the initial densification process. Following the experimental part, the mathematical formulation based on the Critical Plane Approach (CPA) is presented for describing anisotropic mechanical behavior of the material. The procedure for identification of parameters embedded in the constitutive model is outlined and an extensive numerical analysis is conducted simulating the experimental tests.</p> <p>The second part of this thesis deals with induced anisotropy and its focus is on developing an evolution law for the fabric of particulate materials as a function of continuing deformation. The microstructure descriptors are based on lineal intercept measurements and include the areal porosity and the mean intercept length distribution. The methodology involves performing a series of Discrete Element simulations for a granular assembly under evolving directions of the principal stress/strain and defining a correlation with the evolution of material axes. It is demonstrated that granular materials with spherical particles may become anisotropic due to the initial compaction process and that the induced anisotropy is characterized by the coaxiality between the microstructure and the total strain tensors. The proposed evolution law is incorporated into the constitutive framework for anisotropic materials, as discussed in the first part, and some numerical simulations are conducted. It is demonstrated that the proposed approach can describe, at least in a qualitative manner, several manifestations of induced anisotropy in granular materials.</p> / Doctor of Philosophy (PhD)

Thesis (DEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Geotechnical engineering is a relatively young field of engineering and one in which there are still many unanswered questions and gaps in our knowledge. Added to this, the geotechnical materials on each new site on which geotechnical work is undertaken are the unique product of many influences including geology, geomorphology, climate, topography, vegetation and man. There is thus plenty of scope for innovation. This dissertation describes the contributions made to Geotechnical Engineering in South Africa by the Candidate over a period of close on 40 years. It describes the three-step process followed in the majority of these contributions. Step one is the identification of a problem that requires investigation, the application of new techniques or simply the consolidation of existing knowledge. Step 2 is the investigation of the problem and the development of a solution. Step 3 is sharing the outcome of this work with the profession by means of publications, by presentations at seminars and conferences or by incorporation into standards / codes of practice. Part 1 of the dissertation describes the exciting environment in which geotechnical engineers operate. This environment is characterised by openness and cooperation between practitioners of geotechnical engineering, be they geotechnical engineers, engineering geologists, contractors, suppliers or academics. This part also explores the parallels in the roles played by academics and practitioners and how each can contribute to the advancement and dissemination of knowledge. Part 2 describes contributions made in various fields including problem soils (dolomites, expansive clays, uncompacted fills, etc.), lateral support, pile design and construction, health and safety, and cooperation with international organisations. Part 3 describes the Candidate's involvement in the introduction of limit states geotechnical design into South African practice culminating in the drafting of SANS 10160-5 on Basis of Geotechnical Design and Actions. It also describes the Candidate's work with the ISSMGE Technical Committee TC23 dealing with limit states design. Part 4 deals with the Candidate's contribution to other codes and standards and his role on various committees of the Engineering Council of South Africa and the South African Bureau of Standards. The final part of the dissertation provides an overview of the process followed in making such contributions, highlighting the role played by curiosity and a desire to share the knowledge gained with others in the profession. It continues by identifying work that still needs to be done in many of the areas where contributions have been made and concludes with a statement of what the candidate would still like to achieve during the remainder of his career. The Candidate gratefully acknowledges the generous opportunities afforded to him by his colleagues at work and the invaluable guidance and mentorship received from fellow professionals in academia and practice. / AFRIKAANSE OPSOMMING: Geotegniese ingenieurswese is 'n relatiewe jong wetenskap en een met vele kennisgapings en waarin daar nog talle vrae onbeantwoord bly. Daarby is geotegniese materiale uniek tot elke terrein waarop werk aangepak word en die produk van 'n kombinasie van prosesse; insluitend geologie, geomorfologie, klimaats toestande, topografie, plantegroei en menslike aktiwiteite. Daar is dus nog ruim geleentheid vir innoverende bydraes. Hierdie verhandeling beskryf die Kandidaat se bydraes tot Geotegniese Ingenieurswese in Suid-Afrika oor die afgelope 40 jaar. Dit beskryf 'n drie-voudige benadering wat in die meeste van die bydraes gevolg is. Die eerste stap is om die probleem te definieer en te omskryf in terme van die ondersoek wat geloods moet word, asook die noodsaaklikheid vir die ontwikkeling van nuwe tegnologie teenoor die konsolidasie van bestaande inligting. Tydens die tweede stap word die probleem ondersoek en 'n oplossing ontwikkel. Die derde stap is om die resultate te deel met die geotegniese bedryf by wyse van publikasies, voorleggings by konferensies en seminare, en insluiting in praktykkodes en standaarde. Deel 1 beskryf die opwindende werksomstandighede waarbinne geotegniese ingenieurs hul bevind. Dit word geken aan die ope samewerking tussen belanghebbende partye; onder andere ingenieurs, ingenieursgeoloë, kontrakteurs, verskaffers en akademici. Deel 1 beklemtoon ook die parallelle rolle wat vertolk word deur akademici en praktiserende ingenieurs en hoe beide partye bydraes maak tot die ontwikkeling en verspreiding van tegnologie. Deel 2 beskryf die Kandidaat se bydraes tot verskeie navorsingsvelde; waaronder probleemgrondtoestande (dolomiet, swellende kleie, ongekonsolideerde opvullings ens.), laterale ondersteuning, ontwerp en konstruksie van heipale, beroepsveiligheid, en samewerking met internasionale organisasies. Deel 3 beskryf die Kandidaat se betrokkenheid by die bekendstelling van limietstaat geotegniese ontwerp in die Suid-Afrikaanse bedryf wat uitgeloop het op die samestelling van SANS 10160-5 Basis of Geotechnical Design and Actions. Dit beskryf ook die Kandidaat se samewerking met die ISSMGE Technical Committee TC23 wat te make het met limietstaat ontwerp. Deel 4 beskryf die Kandidaat se bydraes tot ander kodes en standaarde en die rolle wat hy vertolk het op verskeie komitees van die Suid-Afrikaanse Raad vir Ingenieurswese asook van die Suid-Afrikaanse Buro van Standaarde. Die laaste deel van die verhandeling bied „n oorsig oor die proses wat gevolg is in bostaande bydraes met die klem op die rol van weetgierigheid en die begeerte om sulke kennis te deel met ander belanghebbendes. Om af te sluit, identifiseer die Kandidaat oorblywende tekortkominge in baie van die vraagstukke waar hy bydraes gelewer het en gee 'n opsomming van wat hy graag nog sal wil bereik tydens die verdere verloop van sy loopbaan. Die Kandidaat gee met dank erkenning aan sy kollegas vir die ruim geleenthede wat hom gebied is en die waardevolle leiding en mentorskap wat hy ontvang het van mede praktiserende ingenieurs en akademici.

Uncertainty in rockmass and in situ stress parameters poses a critical design challenge in geotechnical engineering. This uncertainty stems from natural variability (aleatory) due to the complex history of formation and continual reworking of geological materials as well as knowledge-based uncertainty (epistemic) due to a lack of site specific information and the introduction of errors during the testing and design phases. While such uncertainty can be dealt with subjectively through the use of conservative design parameters, this leads to a lack of understanding of the variable ground response and the selection of an over-conservative design that can have a negative impact on both the project cost and schedule. Reliability methods offer an alternative approach that focuses on quantifying the uncertainty in ground conditions and utilizing it directly in the design process. By doing so, a probability of failure can be calculated with respect to a prescribed limit state, providing a measure of design performance. When multiple design options are considered, reliability methods can be paired with a quantitative risk analysis to determine the optimum design on the basis of safety and minimum cost rather than subjective conservatism. Despite the inherent benefits of such an approach, the adoption of reliability methods has been slow in geotechnical engineering due to a number of technical and conceptual challenges. The research conducted pertaining to this thesis aims to address these issues and remove the perceived “cloak of mystery” that surrounds the use of reliability methods. The scientific and engineering research in this thesis was divided into four sections: (1) the assessment of uncertainty in geotechnical input parameters, (2) a review of reliability methods in the context of geotechnical problems, (3) the development of a reliability-based, quantitative risk approach for underground support design and (4) the application of such a method to existing case studies. The completion of these areas is critical to the design of underground structures and may bring about a shift in design philosophy in the geotechnical industry. / Thesis (Ph.D, Geological Sciences & Geological Engineering) -- Queen's University, 2013-09-18 10:35:26.265

Tyréns ABs har utfört stabilitetsundersökningar för fastigheterna Plogen16samtVälten2 och 3 i Umeå kommun. Områdena är attraktiva vid Umeälv och fastighetsbolaget Cityfastigheter i Umeå AB har önskan att exploatera dem. De beaktade områdena innesluts av Tvärån och Umeälv som medför att området får ett komplext utseende. Det finns således två slänter som omsluter områdena, en mot Tvärån och en mot Umeälv. Områdena består främst av silt med inslag av sand och sulfidsilt men mäktighet på 10 meter. Slänten mot Tvärån visade på markrörelse medan den branta slänten mot Umeälv inte visade några stabilitetsproblem. Tidigare utförda stabilitetsberäkningarna av Tyréns AB visade på 13-14 meter säkerhetsavstånd från slänten mot Umeälv. Då områdena är bebyggda närmare än säkerhetsavståndet och då anses stabil när ingen deformation av slänten har kunnat tydas, väcks frågan hur vida 2D-beräkningar är tillräckliga för att beskriva stabiliteten i dessa typer av slänter kring älvar. Det ledde fram till en önskan om att genomföra stabilitetsberäkningar i 3D. Programvara som valdes för att genomföra 3D-beräkningar var PLAXIS 3D. Då de utförda beräkningarna av Tyréns AB genomfördes i programmet SLOPE/W som tillhör programvaran Geostudio bedömdes att beräkningar i PLAXIS 2D vara nödvändiga att genomföra för att en jämförelse skulle kunna ske. Detta för att PLAXIS och SLOPE/W har olika beräkningsmetoder för att beräkna stabiliteten. Beräkningarna genomfördes i PLAXIS 2D för de båda slänterna med dränerad och odränderad analys. Det för att beakta det mest ogynnsamma situationen. 2D-modellen i SLOPE/W replikerades till PLAXIS 2D medan 3D-modellen byggdes upp från en inmätt terrängmodell av områdena. Undersökningarna visade att odränerade förhållanden gav den lägsta säkerheten av slänterna för 2D och för 3D. Resultaten mellan 2D- och 3D-beräkningar påvisade en betydande stabilitetsökning vid 3D-beräkningar. Beräkningarna i 2D, odränerat, genomfördes inte då modellen kollapsade i beräkningsförfarandet, det tolkades som att säkerhetsfaktorn är under 1 för slänten mot Umeälv. För samma slänt i 3D-modellen uppgick säkerhetsfaktorn till 1,48. Den dränerade beräkningen gav i 2D ett brott på 8 meter från släntkrön och en säkerhetsfaktor på 1,2 och i 3D-beräkningen beräknades den värsta brottytan i den strandpromenaden som ligger vid släntfoten av Umeälv. Det tyder på att de tredimensionella effekterna är av avgörande betydelse för stabiliteten. Det är därmed av värde att utföra 3D-beräkningar för komplexa områden.

The characterization of silty soils is usually designated by the percentage of silt contained within the soil matrix, along with the soil’s void ratio, which is used to describe the soil’s current state. The use of these parameters to assess a soil’s strength and undrained behavior is limited when finer material is contained within the soil. Therefore, additional parameters must be considered in order to correctly assess the strength and liquefaction potential of silty soils. These additional parameters include the skeleton void ratio, equivalent void ratio and granulometric factors. The current research investigates the influence of granulometric parameters, specifically the Median Grain Size Ratio (D50/d50), denoted as μDR (or MDR within graphs and charts), on the strength and liquefaction potential of loose silty sands. A series of undrained monotonic triaxial compression tests (σ3’= 69, 83, and 103 kPa) are performed on reconstituted soil samples, using three different base sand samples and a constant silt material. As a result, three distinct median grain size ratios (μDR = 4.2, 6.75, and 9) were tested with fines content ranging from 0-30% for each μDR. The undrained shear strength at all confining pressures tends to increase with in μDR; beyond 10% fines content there was no noticeable influence of μDR. At any μDR the excess PWP is higher than that of clean sand, when fines content is larger than 5% fines content. The slope of the instability line and phase transformation line are directly affected by the μDR and fines content, with an increase in the instability line and decrease in the phase transformation line with a growing μDR. The results indicate loose granular fills can be designed to be stronger and more resilient under extreme conditions by careful choice of materials in which the μDR>6.75 and the fines content does not exceed 10%. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

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The purpose of this master thesis is to evaluate the results from the completed SCPT (Seismic Cone Penetration Test) surveys with respect to the methods ability to estimate dynamic young´s modulus. This has been done by comparing the result from SCPT to other seismic methods and dynamic parameters converted from “static” geotechnical surveys. SCPT is a relatively new method which has not been used by Sweco or in Sweden to any greater extent and is therefore of interest to be looked in to. By adding two geophones to an ordinary CPT (Cone Penetration Test) equipment as well as including strike plates, hammer and logger system one can log dynamic parameters in addition to the regular parameters logged by a CPT system. This is done by stopping the otherwise continuous CPT survey every meter and striking the strike plates, which are placed under the tracks of the drilling rig. Seismic waves will then travel through the soil down to the geophones and be used to calculate dynamic parameters. For this master thesis a total of 47 geotechnical and geophysical surveys have been considered. The location of these 47 are approximately 7 km north of Norrköping and have been conducted between the years 2016-2017 for the East Link Project. The geotechnical surveys are composed of weight-sounding, ram-sounding and CPT while the geophysical ones are SCPT, refraction-survey and MASW (Multichannel Analysis of Surface Waves). Static elastic parameters have been calculated using the geotechnical survey results according to the Swedish transportation administrations standardized methods. These have then been converted to dynamic parameters with the help of different relationships. When these have been converted they can be compared to SCPT results and other seismic survey methods which also use wave velocity, Poisson’s ratio and density to calculate dynamic elastic parameters. Based on the results from this thesis it can be concluded that the seismic test add-on to a standard CPTu survey is a good method for accessing dynamic modules and it gives extended information of the soil stratigraphy from one single survey point. After the studies and analyses conducted for this thesis it can be concluded that the proposed conversion between static and dynamic young’s modulus using the Alpan curve gives slightly higher values than the ones derived directly from shear waves using SCPT. The other conversion using cone tip resistance to shear wave velocity gives on the other hand slightly lower values than the ones measured with the SCPT. The analysis also indicate similar trends in results between the different seismic methods. These results does however also shows that the used assumptions are somewhat general for accurate comparisons between the methods.