Previous laboratory and field experimental studies of earth pressures exerted on retaining structures and laboratory studies of the at-rest earth pressure coefficient are summarized. The current methods used to evaluate the earth pressures due to compaction are reviewed. The design features of a new instrumented oedometer developed to investigate the effect of number of load cycles on the at-rest earth-pressure coefficient are presented along with the results of a series of tests on Monterey sand #0/30. The Instrumented Retaining Wall Facility developed to provide a means of obtaining experimental measurements of the earth pressures exerted on retaining structures is described. The instrumented wall of the facility is seven feet high and ten feet long and is instrumented to measure horizontal and vertical forces, horizontal earth pressures, horizontal deformations, and temperature. A description of the microcomputer-based data-acquisition system and the software used to record the test results is included. The results of four tests where Yatesville silty sand was compacted in layers in the Instrumented Retaining Wall Facility are presented. The experimental results are compared with the results of similar studies by others and to an analytical method used to estimate compaction-induced earth pressures. / Ph. D.

This dissertation is concerned with controlling the motion of a semisubmersible structure induced by high-frequency waves. The structure consists of a rigid platform and a flexible superstructure. Motion of a structure in fluids generates forces depending on the motion itself. The added mass and damping terms stemming from this motion depend on the frequency of motion. It is well known that for a given wave height, the wave energy is distributed according to a Rayleigh distribution. Because mass and damping terms vary with the frequency of the wave motion, there is an infinite number of sets of dynamical equations, one for each frequency in the Rayleigh distribution. Practical considerations make it necessary to discretize the frequency spectrum, so that there are as many dynamical equations as frequency increments. The center frequency in each increment is computed by equipartitioning of the wave energy distribution represented by a Bretschneider spectrum. The excitation forces are estimated for each increment and the design of optimal control is carried out by the Independent Modal-Space Control (IMSC) method. The net control forces can be found by summing the forces associated with each increment. The technique is demonstrated by means of a numerical example in which the wave-induced vibration of a cylindrical platform with a flexible cantilever beam is suppressed. / Ph. D. / incomplete_metadata

Introduktion – En fråga har väckts kring hur jordtryck beräknas enligt en klassiskjordtryckteori som beskrivs i läroböcker så som (Sällfors,2009), Trafikverket krav och Eurocode av företaget Vara byggkonsult AB. För att skapa en bättre förståelse så togett praktiskt test fram för att mäta jordtrycket utifrån klassiska teorier och jämförs med dessa.Metod – Den valda forskningsmetoden är en litteraturstudie och ett experimentellkvantitativ test. Framtagandet av testet är en iterativ process där metod och utformande uppdaterats efter observationer och diskussion.Resultat – Beräknade värden för den aktiva jordtryckskoefficienten med de olika metoderna varierar mellan 0,221 - 0,278 för materialet 0–4 och mellan 0,25 - 0,334 för materialet 8-16 beroende på vilken metod som avvänds. För de uppmätta värdena så varierar dessa från 0,173 - 0,279 för materialet 0–4 och 0,227 – 0,296 för materialet 8–16 beroende på vilken last som tillförts. Att värdena varierar beror på faktorer så sominre friktionsvinkel, friktion mellan stödvägg och material, beräkningsmetod, samt vilken last som använts vid utfört test.Analys – Genom att jämföra beräkningsmetoderna med de uppmätta testvärdena går det att se likheter och skillnader mellan resultaten. För materialet 0–4 går det att se en likhet mellan de beräknade värdena och de uppmätta värdena för de beräkningsmetoder där friktionen antas vara 0. För materialet 8–16 är det uppmätta värdet konstant lägre än de beräknade för alla beräkningsmetoder. För båda materialtyperna går det att se en trend där ökningen i det uppmätta värdet minskar ju högre last som läggs på.En analys utifrån frågeställning två har gjorts där modellen och metoden för utförandet av det praktiska testet analyserats. De resultat som producerats ur modellen är trovärdiga och är upprepbara till hög grad. Modellen har konstruerats med material och verktyg tillgängliga i en vanlig bygghandel. Materiallista samt ritning på konstruktionen har dokumenterats samt att metoden för genomförande av testerna är väl dokumenterad.Utifrån en analys av fraktionsstorlekens påverkan på det uppmätta trycket observeras det att ett finkornigt material som 0–4 kan uppnå ett högre tryck än ett grövre material som 8–16. De utförda testen stödjer detta då materialet 0–4 resulterar i en högre jordtryckskoefficient än materialet 8–16. Detta är dock motsägelsefullt till hur klassiskt sett så sker det en ökning i friktionsvinkel desto större fraktionsstorleken är.Diskussion – Trafikverkets metod att beräkna jordtryckskofficienten anses vara smidigare att använda i jämförelse med Eruocdes sätt, då det inte krävs mer än ett uppskattande av materialets egenskaper.Faktorer så som mänskliga faktorn är något som också tas upp i rapporten som har haft en inverkan på det slutgiltiga resultatet samt utförandet av tester. Att rita upp en modell digitalt med perfekta linjer är en sak, men att bygga ihop den i verkligheten är en annan sak. För att motverka faktorer så som mänskliga faktorn, så har en rad olika förändringar gjort på modellen samt utförandet av testerna. Enligt de resultat som framtagits så syns det att det finns en skillnad mellan de olika materialen, men detta är inte en stor skillnad. Friktionsvinklarna för materialen skiljer ivsig inte med många grader och därför har inte heller en stor kraftskillnad kunnat uppmätas.Då grundkunskapen vid undersökningens start inte var speciellt hög så lede det tillmisstag som kunde undvikits. Den tid som lagts ner på att fixa de misstagen kunde istället lagts ner på att förbättra modellen för att få ännu bättre värden. / Introduction – A question has been raised regarding how earth pressure is being calculated regarding classical textbook theory, the Swedish Transport Administration and Eurocode by the company Vara byggkonsult AB. To create a better understanding of the subject a practical test is being derived from classical theories and compared to these.Method – The chosen research method is a litterature study and an experimental quantitative test. To produce a test an iterative process is being used that is beeing updated according to observations and discussions.Results – Calculated values for the active earth pressure coefficient with the different methods vary between 0,221 – 0,278 for the material 0-4 and between 0,25 – 0,334 for the material 8-16 depending on which method is used. For the measured values, these vary from 0,173 – 0,279 for the material 0-4 and 0,227 – 0,296 for the material 8-16, depending on the load added. The fact that the values vary depends on factors such as internal friction angle, friction between the supporting wall and material, calculation method and which load was used when the test was carries out.Analysis – By comparing the calculation methods with the measured test values, it is possible to see similarities and differences between the results. For the material 0-4, it is possible to see a similarity between the calculated values for the calculation methods where the friction is assumed to be 0. For the material 8-16, the measured value is constantly lower than the calculated values for all calculation methods. For both material types, a trend can be seen where the increase in the measured value decreases the higher the load that is applied. An analysis based on question two has been done where the model and method for preforming the practical test has been analysed. The results produced from the model are credible and are repeatable to a high degree. The model has been constructed with materials and tools available in a regular hardware store. Material list and drawing of the construction have been documented and that the method for carrying out the tests is well documented.Based on an analysis of the effect of fraction size on the measured pressure, it is observed that a fine-grained material such as 0–4 can achieve a higher pressure than a coarser material such as 8–16. The tests carried out support this as material 0–4 results in a higher earth pressure coefficient than material 8–16. However, this is contradictory to how, classically speaking, there is an increase in friction angle the larger the fraction size is.Discussion – The Swedish Transport Administration's method of calculating the earth pressure coefficient is considered easier to use in comparison to Eruocde's method, as no more than an estimation of the material's properties is required.Factors such as the human factor is something that is also addressed in the report that has had an impact on the final result as well as the execution of tests. Drawing up a model digitally with perfect lines is one thing, but building it in real life is another. To counteract factors such as the human factor, a number of different changes have been made to the model and the execution of the tests.According to the results produced, it appears that there is a difference between the different materials, but this is not a big difference. The friction angles of the materials iido not differ by many degrees and therefore a large force difference has not been measured either.As the basic knowledge at the start of the survey was not particularly high, it led to mistakes that could have been avoided. The time spent on fixing those mistakes could instead be spent on improving the model to get even better values.

published_or_final_version / Applied Geosciences / Master / Master of Science

The problem of passive earth pressure is one of the important topics in Geotechnical engineering. At attempt is made in this thesis to generate passive earth pressure coefficients for general c-Φ soils using logarithmic spiral failure surface by limit equilibrium approach. Method of slices for the determination of passive force in c-Φsoils is presented and the method is extended to a typical problem of two layered soil system. The application of passive earth pressure coefficients has been demonstrated for pullout capacity of inclined strip anchors in sloping ground. A semi-empirical approach for the determination of displacement-related passive earth pressure is presented. The thesis is organized in seven chapters. In Ch.2, a brief summary of relevant literature is presented along with the scope of the thesis. In Ch. 3, limit equilibrium approach for the determination of the passive earth pressure in soils is presented. The passive earth pressure coefficients are developed for δ/Φ= - 1, - ¾ , -2/3, - ½, 0, ½, ¾ 1; ψ = -60º, -45º, -30º, -20º, -10º, 0º,10º,20º,30º and 45º; i= -30º, -20º, -10º,0º,10º,20º and 30º where δ is the wall friction angle, Φ is the angle of internal friction, Ψ is the inclination of the wall with the vertical and i is the ground inclination with the horizontal. Ch.4 deals with the method of slices. Satisfying all the three equilibrium conditions and using interstice friction as a variable, passive earth pressure coefficients are obtained for soils. Extension of the method to a two layered soil system is demonstrated by an illustrative example. A generalised approach for the determination of uplift capacity of inclined strip anchors in sloping ground subjected to surcharge is presented in Ch. 5. Expressions are provided for the determination of pullout capacity of deep anchors. Displacement-related passive earth pressure is discussed in Ch. 6. Using the earlier experimental observations on the passive earth pressure measurements with displacements, expressions have been fitted for the determination of displacement-related passive earth pressure for the three modes of rigid body movements viz., translation, rotation about the top and rotation about the bottom. The conclusions drawn from the present investigations are listed in Ch 7. (Pl see the original document for abstract)

No description available.

Bro 2004, BV Bro and the Eurocodes give guidelines for how to consider earth pressure induced by change in temperature and braking forces when designing backwalls. In this thesis those demands are investigated using PLAXIS for evaluation of the earth pressure. The results show that the model in PLAXIS corresponds quite well with the conventions in Bro 2004 and that modelling in PLAXIS gives reliable results. The demand in Bro 2004 that backwalls always shall be designed for passive earth pressure has been found to be pessimistic. In case of long bridges and short backwalls passive earth pressure is most often reached but for shorter bridge lengths in combination with longer backwalls this is almost never the case. It was also found that PLAXIS is sensitive and that the structure of the model and the choice of input are essential. A model in PLAXIS doesn’t make the design more effective but it may be a good tool for analysing the effect of the earth pressure combined with other effects such as the patterns for displacement as well as moment- and force distributions. / Bro 2004, BV Bro och Eurocode ger råd för hur jordtryck som uppkommer på grund av temperaturändring och bromskraft skall tas hänsyn till vid dimensionering av ändskärmar. I detta examensarbete undersöks dessa dimensioneringskrav med hjälp av PLAXIS för att göra en bedömning av jordtrycket. Resultaten visar att modellen i PLAXIS överensstämmer ganska väl med de konventioner som ges i Bro 2004 och att PLAXIS ger tillförlitliga resultat. Kravet att ändskärmar alltid ska dimensioneras för passivt jordtryck visade sig vara pessimistiskt. I fall med långa broar och korta ändskärmar nås ofta passivt jordtryck men för kortare broar med djupare ändskärmar är detta nästan aldrig fallet. PLAXIS visade sig vara känsligt för hur modellen byggs upp och vilka indata som ändvänds, varför dessa bör väljas försiktigt. En modell i PLAXIS medför inte en mer effektiv dimensionering men kan vara ett bra verktyg för analys av jordtryck i kombination med andra effekter så som förskjutningsmönster samt moment- och kraftdiagram.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Kamran Zarrabi-Kashani. / M.S.

In this investigation, seismic response of retaining walls constructed with cohesive and cohesionless backfill materials was studied. Fully dynamic analysis based on finite difference method was used to evaluate the performance of retaining walls during the earthquake. The analysis response was verified by the experimental study conducted on a retaining wall system with cohesive backfill material in the literature. The effects of cohesion and free-field peak ground acceleration (PGA) on seismic earth thrust, the point of action of earth thrust, and maximum wall moment during the earthquake were compared with analytical and experimental solutions. The numerical results were compared with various analytical solutions. The motion characteristics of the retaining wall during the earthquake were also considered. The relative displacement of the walls with various backfill cohesions, under different ground motions, and free-field PGAs were investigated. Current analytical and empirical correlations developed based on Newmark sliding block method for estimating retaining wall movement during earthquakes were compared with the numerical approach. Consequently, fragility analyses were conducted to determine the probability of damage to the retaining walls. To evaluate the fragility of the studied models, specific failure criterion was chosen for retaining walls based on the suggested methods in practice. Using numerical approaches, the effects of soil-wall interaction and wall rigidity on the seismic response of retaining walls were also evaluated in earthquake conditions for both cohesive and cohesionless backfill materials. According to the findings, practical correlations were presented for conducting the seismic design of retaining walls.

Two series of static full-scale lateral pile cap tests were conducted on pile caps with different aspect ratios, with full width (homogeneous) and limited width backfill conditions involving loose sand and dense gravel. The limited width backfills were constructed by placing a relatively narrow zone (3 to 6 ft (0.91 to 1.83 m)) of higher density gravel material adjacent to the cap with loose sand beyond the gravel zone. Test results indicated that large increases in lateral passive resistance could be expected for limited width backfills. The main focus of this study is to assess the contribution of plane strain stress effects and 3D geometric end effects to the total passive resistance mobilized by limited width backfills, using soil and pile cap properties associated with the field tests. For this purpose, the finite element program, PLAXIS 2D was used to investigate the static plane strain passive behavior of the full-scale tests. To validate the procedure, numerical results were calibrated against analytical results obtained from PYCAP and ABUTMENT. The analytical models were additionally validated by comparison with measured ultimate passive resistances. The calibrated model was then used to simulate the passive behavior of limited width gravel backfills. Parametric studies were also executed to evaluate the influence of a range of selected design parameters, related to the pile cap geometry and backfill soil type, on the passive resistance of limited width backfills. Numerical results indicated that significant increases in passive resistance could be expected for long abutment walls where end effects are less pronounced and the geometry is closer to a plane strain condition. Comparisons between measured and numerical results indicated that using the Brinch-Hansen 3D correction factor, R3D, as a multiplier to the plane strain resistances, will provide a conservative estimate of the actual 3D passive response of a pile cap with a limited width backfill. Based on results obtained from the parametric studies, a design method was developed for predicting the ultimate passive resistance of limited width backfills, for both plane strain and 3D geometries.