مجموعه ای از تزهای دوره دکترا شاخه مهندسی خاک و پی به زبان انگلیسی

P. Smith (2003) - "Numerical analysis of infiltration into partially saturated soil slopes". PhD Thesis. University of London.

Download this thesis : http://www3.imperial.ac.uk/geotechnics/publications/phdtheses/smith

The issue of slope stability is a core concern to geotechnical engineers. Traditional methods of analysis assume that the soil is fully saturated. However, throughout much of the world, slopes exist in residual soil deposits. Such soils are often unsaturated, and it has become clear that the traditional saturated approach to assessing these slopes is inadequate.

Current knowledge of the infiltration processes into unsaturated soil slopes is inadequate to enable reliable assessment of stability. This thesis constitutes an investigation into these infiltration processes, using numerical modelling techniques.

A discussion on the general nature of unsaturated soils is followed by a survey of previous attempts to apply numerical modelling to unsaturated soils. The core equations governing the fully coupled constitutive behaviour of unsaturated soils are developed and presented, along with details of how these equations were implemented in numerical form. A conceptual model that qualitatively assesses the behaviour of unsaturated soils is also presented.

The behaviour of unsaturated soil slopes was investigated through numerical simulations of the Tung Chung slope in Hong Kong, using the Imperial College Finite Element Program ( ICFEP ), with the numerical predictions compared to field monitoring data of the pore water pressures / suctions from the site.

It is shown that the variation of pore pressures is very sensitive to the relationship between suction and degree of saturation, as represented by the Soil Water Characteristic Curve. Also critical are the permeability parameters of the soil, including the variation of permeability with suction.

The importance of accurately reproducing the true nature of the rain event is also clearly demonstrated.

Many areas where further work is required are identified. In particular, there is a need to establish methods to obtain reliable soil parameters to permit accurate modelling of the behaviour of unsaturated soils.
http://www3.imperial.ac.uk/geotechnics/publications/phdtheses/smith

. Colmenares Montañez (2002) - "Suction and volume changes of compacted sand-bentonite mixtures". University of London.

Download this thesis : http://www3.imperial.ac.uk/portal/pls/portallive/docs/1/7293179.PDF

Engineered barriers are used in the containment of hazardous materials and are usually a composite of compacted clayey soil and a synthetic membrane. Containment elements such as landfill liners should be designed to control or prevent leachate migrate or groundwater ingress.

Engineering specifications for a compacted clay liner are based mainly in a hydraulic conductivity less than 10E-9 m/s and the need for stability during construction and operation of the landfill.

Sand-bentonite mixtures are often used as a barrier material. The addition of relatively small amount of bentonite (5-15%) can improve the performance of a granular material providing both a low permeability and an enhanced mechanical stability. However not all the possible compaction conditions produce a low permeability and mechanically stable material. Changes in water content after compaction can cause swelling or collapse depending on the stress and suction conditions before the water content change occurs.

A laboratory investigation of the swelling-collapse behaviour of compacted mixtures of sand-bentonite has been undertaken. Compaction and suction characteristics were established. The suction and volume change characteristics were investigated through a series of oedometer tests.

The central part of the experiment programme focused on the detailed investigation of the processes of swelling and collapse during controlled wetting. To do this, a significant number of modifications were required to the existing apparatus.

Fabric studies including Environmental Scanning Electron Microscopy and Mercury Intrusion Porosimetry were also undertaken. Intrinsic behaviour and the relationship between suction and water content were comprehensively studied. A parametric study of the influence of bentonite content and sand grading was also undertaken.

The results are presented and analysed. Recommendations for future research are made.

. Colmenares Montañez (2002) - "Suction and volume changes of compacted sand-bentonite mixtures". University of London.

Download this thesis : http://www3.imperial.ac.uk/portal/pls/portallive/docs/1/7293179.PDF

Engineered barriers are used in the containment of hazardous materials and are usually a composite of compacted clayey soil and a synthetic membrane. Containment elements such as landfill liners should be designed to control or prevent leachate migrate or groundwater ingress.

Engineering specifications for a compacted clay liner are based mainly in a hydraulic conductivity less than 10E-9 m/s and the need for stability during construction and operation of the landfill.

Sand-bentonite mixtures are often used as a barrier material. The addition of relatively small amount of bentonite (5-15%) can improve the performance of a granular material providing both a low permeability and an enhanced mechanical stability. However not all the possible compaction conditions produce a low permeability and mechanically stable material. Changes in water content after compaction can cause swelling or collapse depending on the stress and suction conditions before the water content change occurs.

A laboratory investigation of the swelling-collapse behaviour of compacted mixtures of sand-bentonite has been undertaken. Compaction and suction characteristics were established. The suction and volume change characteristics were investigated through a series of oedometer tests.

The central part of the experiment programme focused on the detailed investigation of the processes of swelling and collapse during controlled wetting. To do this, a significant number of modifications were required to the existing apparatus.

Fabric studies including Environmental Scanning Electron Microscopy and Mercury Intrusion Porosimetry were also undertaken. Intrinsic behaviour and the relationship between suction and water content were comprehensively studied. A parametric study of the influence of bentonite content and sand grading was also undertaken.

The results are presented and analysed. Recommendations for future research are made.

J. Douglas (2001) - "A critical reappraisal of some problems in engineering seismology". University of London.

Download this thesis: http://www3.imperial.ac.uk/portal/pls/portallive/docs/1/7293180.PDF

The estimation of strong-motion characteristics is important for engineering design. Such an estimation, often in terms of peak ground acceleration and spectral ordinates, is usually based on the combination of physical models that describe the process with observed ground motions recorded during earthquakes.

A multitude of results have been derived over the past thirty years, based on different models and different quantities and qualities of input data. However, there is still little consensus on their validity and on the associated uncertainties which are important for the estimation of expected ground motions in design.

This thesis describes investigations of whether best use is being made of the strong-motion observations now becoming available, given the assumptions underlying the relationships to estimate ground motions, in the hope that this estimation can be improved. Potential sources of scatter, from each stage of the derivation of attenuation relations are highlighted, and many of these are critically examined to assess their importance. This is achieved by: assessing the inherent uncertainty of the input strong-motion data including that arising from accelerogram processing, examining the importance of independent parameters and the effect of uncertainties and errors in these variables and by investigating the effect of the data distribution with respect to the independent variables.

This thesis presents updated relations for horizontal and vertical near-field strong-motion characteristics including peak ground acceleration and spectral acceleration, examines the assessment of permanent ground displacements in the near field due to faulting and estimates the effect of vertical ground motion on horizontal response. It concludes that any further improvement of the scaling of ground motions with seismological parameters and local site conditions depends primarily on the acquisition of more high-quality observational data.

منبع: http://www.keshavarz.org/modules/rmdp/down.php?id=118
مطالعه ای در مشخصات تنش-کرنش-مقاومت رس Eocence
An investigation of the stress-strain-strength characteristics of an Eocence clay

پایان نامه دکتری
دانشگاه: Emperial Colledge London
نویسنده: N. A. Minh
زبان: انگلیسی
سال دفاع:2007
366 صفحه، 32 مگابایت
http://www3.imperial.ac.uk/portal/pls/portallive/docs/1/7941696.PDF

Energy-Based Evaluation and Remediation of Liquefiable Soils

Type of Document Dissertation
Author Green, Russell A.
Author's Email Address rugreen@vt.edu
URN etd-08132001-170900
Title Energy-Based Evaluation and Remediation of Liquefiable Soils
Degree PhD
Department Civil Engineering
Advisory Committee Advisor Name Title
James K. Mitchell Committee Chair
J.R. Martin Committee Member
M. Gutierrez Committee Member
M.P. Singh Committee Member
S.F. Obermeier Committee Member
T. Kuppusamy Committee Member

Keywords Remediation
Ground Improvement
Liquefaction
Energy
Earthquake
Densification

Date of Defense 2001-08-06
Availability unrestricted
Abstract
Energy-Based Evaluation and Remediation of Liquefiable Soils

Russell A. Green

Dr. James K. Mitchell, Chair

Charles E. Via, Jr. Department of Civil and Environmental Engineering

ABSTRACT

Remedial ground densification is commonly used to reduce the liquefaction susceptibility of loose, saturated sand deposits, wherein controlled liquefaction is typically induced as the first step in the densification process. Assuming that the extent of induced liquefaction is approximately equal to the extent of ground densification, the purpose of this research is to assess the feasibility of using earthquake liquefaction data in remedial ground densification design via energy-based concepts.

The energy dissipated by frictional mechanisms during the relative movement of sand grains is hypothesized to be directly related to the ability of a soil to resist liquefaction (i.e., Capacity). This hypothesis is supported by energy-based pore pressure generation models, which functionally relate dissipated energy to residual excess pore pressures. Assuming a linearized hysteretic model, a ?simplified? expression is derived for computing the energy dissipated in the soil during an earthquake (i.e., Demand). Using this expression, the cumulative energy dissipated per unit volume of soil and normalized by the initial mean effective confining stress (i.e., normalized energy demand: NED) is calculated for 126 earthquake case histories for which the occurrence or non-occurrence of liquefaction is known. By plotting the computed NED values as a function of their corresponding SPT penetration resistance, a correlation between the normalized energy capacity of the soil (NEC) and SPT penetration resistance is established by the boundary giving a reasonable separation of the liquefaction / no liquefaction data points. NEC is the cumulative energy dissipated per unit volume of soil up to initial liquefaction, normalized by the initial mean effective confining stress, and the NEC correlation with SPT penetration resistance is referred to as the Capacity curve.

Because the motions induced during earthquake shaking and remedial ground densification significantly differ in amplitude, duration, and frequency content, the dependency of the derived Capacity curve on the nature of the loading needs to be established. Towards this end, the calibration parameters for energy-based pore pressure generation models are examined for their dependence on the amplitude of the applied loading. The premise being that if the relationship between dissipated energy and pore pressure generation is independent of the amplitude of loading, then the energy required to generate excess pore pressures equal to the initial effective confining stress should also be independent of the load amplitude. However, no conclusive statement could be made from results of this review. Next, first order numerical models are developed for computing the spatial distribution of the energy dissipated in the soil during treatment using the vibratory probe method, deep dynamic compaction, and explosive compaction. In conjunction with the earthquake-derived Capacity curves, the models are used to predict the spatial extent of induced liquefaction during soil treatment and compared with the predicted spatial extent of improvement using empirical expressions and guidelines. Although the proposed numerical models require further validation, the predicted extent of liquefaction and improvement are in very good agreement, thus giving credence to the feasibility of using the Capacity curve for remedial ground densification design.

Although further work is required to develop energy-based remedial densification design procedures, the potential benefits of such procedures are as follows. By using the Capacity curve, the minimum dissipated energy required for successful treatment of the soil can be determined. Because there are physical limits on the magnitude of the energy that can be imparted by a given technique, such an approach may lead to improved feasibility assessments and initial designs of the densification programs.

لينکهاي دانلود را از باکس زير انتخاب نماييد:

مقاومت برشی توده های سنگ
The Shear Strength of rack masses

نویسنده: K.J. Douglas
پایان نامه دکتری
سیدنی- استرالیا-2002
برای دانلود به لینک زیر مراجعه نمایید و یا از باکس زیر لینکهای دانلود را انتخاب نمایید:
http://www.library.unsw.edu.au/~thesis/adt-NUN/uploads/approved/adt-NUN20040107.094847/public/

www.keshavarz.org
dr . amin . keshavarz homepage

صفحه اصلی: http://emjm.blogfa.com/

R.J. Bathurst, D. Walters, N. Vlachopoulos, P. Burgess, T.M. Allen, Full
scale testing of Geosyntetic Reinforced Walls, proceeding of
GeoDenver 2000. Available by the Geoengineer Website and donated
by Captain N. Vlachopoulos
http://www.geoengineer.org/geodenver2000.PDF

صفحه اصلی: http://emjm.blogfa.com/
Neil Morgan (2002), The Influence of Variation in Effective Stress on
the Serviceability of Soil Nailed Slopes, A thesis submitted for the
degree of Doctor of Philosophy, Department of Civil Engineering
School of Engineering, University of Dundee, September 2002. Thesis
available by the Geoengineer website.

http://www.geoengineer.org/files/morganthesis.pdf
لینک کمکی دانلود:
http://persiandrive.net/950854