In this thesis, some aspects concerning building embankments founded on sulphide clay are studied, with special reference to ground improvement by preloading in combination with prefabricated vertical drains (PVD’s). The main purpose of the research was to increase empirical knowledge of the mechanical behaviour of sulphide clays subjected to embankment loadings and of the interaction between vertical drains and sulphide clays. Important aspects related to ground improvement with PVD’s in more general terms are also treated, in particular how various uncertainties regarding the properties of the clay and the clay-drain interaction imposed in the design phase can be addressed. The benefits of using theobservational method for handling these uncertainties are discussed, and a description of how the method was used in an embankment project is presented. The results from the research are presented in one conference paper and two papers submitted to peer-reviewed international journals, which are appended. The design of PVD’s involves describing the consolidation characteristics of the clay and the interaction between the drains and the clay. Primarily, the rate of consolidation is determined by the hydraulic conductivity (permeability) of the clay in the horizontal direction. Hence, accurate determination of this material property is of paramount importance in making reliable design predictions. As conventional laboratory tests for assessing the consolidation characteristics of a clay only provide information about its properties in the vertical direction, one is often left to make assumptions about the horizontal properties based on empirical correlations. Reliable empirical knowledge of these correlations for a certain clay is there forevital. A large number of CRS tests were performed on horizontal and vertical samples ofsulphide clay in order to investigate the correlation between the horizontal and verticalhydraulic conductivity and coefficient of consolidation. The results show that there is very small anisotropy in these parameters and that the scatters in the results are large. For designpurposes, sulphide clays should therefore be assumed to be isotropic in this respect. In orde rto handle the variation in properties, several parallel tests should be made and partial factors of safety should be introduced in the design. Introducing partial factors of safety in the design of PVD’s is one of the main topics suggested for further research. Regarding the clay-drain interaction, a study of the disturbance effects (smear effects) during the installation of drains in sulphide clays was performed. Back-calculations of measurements of pore pressure dissipation were made via a parameter study. It was shown that smear affects the consolidation rate to some extent but that the natural (undisturbed) hydraulic conductivity is more significant. The undrained shear strength su of a clay is dependent on the preconsolidation pressure σ 'p . As the clay consolidates under a loading, the effective stress increases, possibly to magnitudes surpassing the initial preconsolidation pressure and thereby leading to increased undrainedshear strength of the clay. The relation between su and σ 'p, i.e. the ratio su /σ 'p for asulphide clay, was investigated based on results from a large number of in situ tests andlaboratory tests. There were large scatters in the measurements, but su /σ 'p =0.25 is suggested as being relevant in the direct shear zone for design purposes in sulphide clays. / <p>QC 20101101</p>

Rapid constructed embankments founded on soft deposits have a negative influence on the short term stability. Many engineering constructions such as road and railway embankments are often constructed on soft clay deposits. In stability analysis calculation of safety factor (SF), as the primary design criteria can be evaluated through different numerous methods such as limit equilibrium method (LEM) and finite element method (FEM). It is of particular interest to determine/estimate appropriate stability of the specified embankment which is highly dependent on the analysis method used. Therefore, it is a challenge for geotechnical engineers to judge which analysis method can simulate better the reality.  The aim of this thesis is to increase understanding applicability of the three applied programs; Plaxis2D, Plaxis3D and Slope/W in simulating and stability analysis/estimation of embankments founded on clay deposits.  The work has involved analysis and comparison of the stability through estimate of the SF and the critical failure surfaces obtained through 2D and 3D programs. Four case configurations were studied for the stability analysis. In each case variation in plastic parameters of clay (φ-c) or load geometry, was the scenario to make the comparison analysis. Moreover, application FEM3D offers an attractive alternative to traditional approaches to the problem (especially for LEM).  The main conclusions from this study are the following:  (1)   Concerning the three applied programs, FEM3D has the minimum SF sensitivity to change in plastic parameters of clay deposit. (2)   For embankments founded on clay deposit, the 3D failure surfaces are easily found via the FEM3D analysis program, which is closer to reality, while failure results of 2D analysis programs can never occur in reality. (3)   Using 2D analysis method instead of 3D, to investigate the stability of 3D embankment model tend to give higher SF results up to 14% for embankments  founded on undrained clay deposit. (4)   The failure surfaces in 3D analysis are likely to be shallower than in the corresponding 2D model. (5)   Results from the 3D analysis through hand calculation and program calculation do not correspond with each other for embankment founded on soft clay deposit. The first reason is rooted in limitation of the hand formula. The formula is suitable for embankment founded on one layer deposit (soil); however an embankment founded on 3 layers of deposit (soil) was analyzed in this study. The second reason is related to applied method of calculation. 3D hand calculation formula is based on method of slices however; analysis method in program calculation is based on FEM.

Thesis. 1978. Sc.D.--Massachusetts Institute of Technology. Dept. of Civil Engineering. / Vita. / Bibliography: leaves 342-349. / Sc.D.

Numerical methods and specifically the finite element method have improved significantly since their introduction in the 60's. These advances were mainly in: 1) introducing higher-order elements, 2) developing effective solution schemes, 3) developing sophisticated means of modeling the constitutive behavior of geotechnical materials, and 4) introducing iteration techniques to model material non-linearity. This thesis, on the other hand, deals with the topic of modeling the boundary conditions of the finite element problem. Typically, the boundary conditions will be approximated by specifying displacement constraints. such as restraining the bottom boundary of the finite element mesh against displacements in the horizontal and vertical directions (x- and y-directions). Where bedrock or dense residual soils underlie the soft foundation soil at a relatively shallow depth, this is a good assumption. However. when soft soil is encountered for large depths, the assumption of zero movement constraints for a mesh boundary at a shallower depth than the actual bedrock will result in a serious underestimation of stresses and displacements. By coupling boundary elements to the finite elements and using them to model the infinite extent of the foundation soil, a more realistic answer is obtained. Employing the coupled boundary element - finite element method, four cases were analyzed and the results compared to values of the pure finite element method. The results show that the coupled method indeed yielded higher stress- and displacement-values, indicating that the pure finite element method underestimates stresses and displacements when modeling very deep soils. / Master of Science

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2005. / There has always been some debate in the past about the most effective and economical type of revetment to be used to combat or prevent erosion in rivers and channels. Some of the most common materials used for these mitigation measures are gabions, Reno mattresses and rip rap. A study done by the Colorado State University (CSU, 1984), comprised hydraulic tests of Reno mattresses used as a channel bed revetment. The result were compared with those of rip rap. This thesis mainly deals with the evaluation of incipient motion conditions for rock used in Reno mattresses and as rip rap. In this thesis the results of the CSU study and the design criteria of Maccaferri are evaluated and compared with the result obtained when applying the stream power theory and the Shields' theory with respect to incipient motion. This thesis includes the theory with respsect to incipient motion conditions, background to the CSU study and comparisons of the results of the CSU study and Maccaferri's design criteria with theoretical calculations. A cost comparison of Reno mattresses and rip rap as channel bed revetment measures, as well as conclusions and recommendations with regard to the design and use of these options, are also included. The frame of reference for this thesis is the set of CSU test results. The calibrations achieved, proposals made and accuracy of conclusions thus depend on those results.

Based upon the upper bound limit analysis, the stability numbers have been developed for a two-layered soil slope both for an associated flow rule material and for a homogeneous slope with non-associated flow rule material. The failure surface was assumed to be an arc of logarithmic spiral and it automatically ensures the kinematics admissibility of the failure mechanism with respect to the rigid rotation of the soil mass about the focus of the logarithmic spiral. The effect of the pore water pressure and horizontal earthquake body forces was also included m the analysis. For a non-associated flow rule material, the stress distribution along the failure surface was developed with the assumption of interslice forces given by Fellenius and Bishop. The stability numbers have been found to reduce appreciably with increases m the (i) horizontal inclination (β) of slope, (ii) pore water pressure coefficient, ru and (iii) horizontal earthquake acceleration coefficient (kh). The values of the stability numbers for a non-associated co-axial flow rule, with dilatancy angle ψ =0, have been found to be considerably lower as compared to the associated flow rule material. For a given height of the slope, with associated flow rule, the values of the stability numbers have been found to increase with increase in the thickness of a layer with greater value of the friction angle Φ. The results have been given in the form of non-dimensional stability charts, which can be used for readily obtaining either the value of the critical height or the factor of safety The methodology can be easily extended even for multi-layered soil slopes with different values of cohesion (c), bulk unit weight (γ) and friction angle (Φ). An attempt has also been made in this thesis to study experimentally the effect of the frequency of the excitation and the addition of non-plastic fines on the liquefaction resistance of the material Shake table studies, generating uni-axial sinusoidal horizontal vibrations, were earned out for this purpose. During the period of excitation of the material, the settlement at the surface of the sample increases continuously with time up to a certain peak value and thereafter, it becomes almost constant. For the excitation of the material with higher frequency, more number of cycles was seen to reach the final settlement. With the continuous excitation of the material, the magnitude of the pore water pressures increases up to a certain peak value and there after, its magnitude decreases till it again becomes the hydrostatic pressure as it was before the excitation of the material. The peak magnitude of the pore water pressure tends to be higher for the excitation with smaller frequency especially at greater depths from the ground surface. The addition of non-plastic fines tends to increase the magnitude of the settlement as well as the increase in the pore water pressure.

Esta dissertação apresenta a investigação geotécnica, análise crítica de projeto e o desempenho de aterros sobre solos moles para a construção do novo acesso à ZIP Zona Industrial Portuária, em SUAPE. Esta pesquisa é de suma importante por se tratar de um estudo de solo em uma área com pouca informação geotécnica e com grandes perspectivas de desenvolvimento. A obra apresenta uma extensão de 4,254 Km, o projeto contempla a construção de aterros em duas etapas, com a implantação de geodrenos, aplicação de manta geotêxteis, colchão drenante, geossintéticos e sobrecarga temporária. O objetivo desta pesquisa é a realização de um estudo de camada do solo presente no local, além de fazer uma análise crítica de projeto e do monitoramento dos deslocamentos verticais e das poro- pressões. A partir dos resultados adquiridos, observou-se que há uma espessa camada de solo mole, com variações de espessuras, nos quatro trechos de obra. Foi verificado, de um modo geral, que os recalques estimados pela dissertação são superiores aos medidos e inferiores aos previstos em projeto. Vale ressaltar que a instrumentação foi instalada no final da construção da primeira etapa, o que dificulta a interpretação das leituras. Também constatou-se, na análise de projeto, que o número adotado como índice de compressão é aceitável para a previsão do recalque. Nota-se ainda que ocorreram recalques diferenciais, nos sentidos longitudinais e transversais em todos os trechos da obra / This paper presents the geotechnical investigation, critical analysis of design and performance of embankments on soft soils for the construction of new access to ZIP - Port Industrial Zone in SUAPE. This research is very important because it is a study of soil in an area with little information and geotechnical huge potential for development. The work presents an extension of 4.254 km, the project includes construction of landfills in two stages, with the placement of geodrenos, blanket application of geotextiles, drainage mat, placement of geosynthetics and temporary overload. The objective of this research work is to conduct a study of the soil layer at the scene, and make a critical analysis of design and monitoring of vertical displacements and pore pressures. From the results, it was observed that there is a thick layer of soft soil, with variations in the thickness of four pieces of work. It was found, in general, that the settlements are higher than estimated by the paper and the measured lower than envisaged in the project. It is noteworthy that the instrumentation was installed at the end of the first phase of construction, which complicates the interpretation of the readings. It was also seen in the analysis of project, the number adopted as the compression rate is acceptable to the prediction of repression. Note also that differential repression occurred in the longitudinal and transverse directions in all parts of the work

Made available in DSpace on 2017-06-01T17:57:31Z (GMT). No. of bitstreams: 1 dissertacao_mario_paulo.pdf: 5670378 bytes, checksum: 7c22407dc1eb904769d6e6a97da2c66c (MD5) Previous issue date: 2011-10-01 / This paper presents the geotechnical investigation, critical analysis of design and performance of embankments on soft soils for the construction of new access to ZIP - Port Industrial Zone in SUAPE. This research is very important because it is a study of soil in an area with little information and geotechnical huge potential for development. The work presents an extension of 4.254 km, the project includes construction of landfills in two stages, with the placement of geodrenos, blanket application of geotextiles, drainage mat, placement of geosynthetics and temporary overload. The objective of this research work is to conduct a study of the soil layer at the scene, and make a critical analysis of design and monitoring of vertical displacements and pore pressures. From the results, it was observed that there is a thick layer of soft soil, with variations in the thickness of four pieces of work. It was found, in general, that the settlements are higher than estimated by the paper and the measured lower than envisaged in the project. It is noteworthy that the instrumentation was installed at the end of the first phase of construction, which complicates the interpretation of the readings. It was also seen in the analysis of project, the number adopted as the compression rate is acceptable to the prediction of repression. Note also that differential repression occurred in the longitudinal and transverse directions in all parts of the work / Esta dissertação apresenta a investigação geotécnica, análise crítica de projeto e o desempenho de aterros sobre solos moles para a construção do novo acesso à ZIP Zona Industrial Portuária, em SUAPE. Esta pesquisa é de suma importante por se tratar de um estudo de solo em uma área com pouca informação geotécnica e com grandes perspectivas de desenvolvimento. A obra apresenta uma extensão de 4,254 Km, o projeto contempla a construção de aterros em duas etapas, com a implantação de geodrenos, aplicação de manta geotêxteis, colchão drenante, geossintéticos e sobrecarga temporária. O objetivo desta pesquisa é a realização de um estudo de camada do solo presente no local, além de fazer uma análise crítica de projeto e do monitoramento dos deslocamentos verticais e das poro- pressões. A partir dos resultados adquiridos, observou-se que há uma espessa camada de solo mole, com variações de espessuras, nos quatro trechos de obra. Foi verificado, de um modo geral, que os recalques estimados pela dissertação são superiores aos medidos e inferiores aos previstos em projeto. Vale ressaltar que a instrumentação foi instalada no final da construção da primeira etapa, o que dificulta a interpretação das leituras. Também constatou-se, na análise de projeto, que o número adotado como índice de compressão é aceitável para a previsão do recalque. Nota-se ainda que ocorreram recalques diferenciais, nos sentidos longitudinais e transversais em todos os trechos da obra

Over 115 miles of rock revetment have been constructed in the Willamette Basin to protect river banks. This study examines the effect on riparian mammals of maintaining these revetments by vegetation and debris clearing. Differences between cleared and uncleared revetments were measured using a canopy coverage method of vegetation analysis; mammals were studied by trapping, by direct observation, and by noting such signs as scats, tracks, etc.

Preloading without a surcharge is a common method for ground improvement. Thereare however uncertainties related to the number of site investigations and the partialfactor method has been identified as a problem. This thesis proposes a probabilisticdesign approach, using a Monte Carlo simulation to calculate the failure probabilityin the serviceability limit state for preloading without a surcharge. The methodwas applied to a case where the possibility of using preloading without a surchargewas determined. A parameter influence and sensitivity analysis were performed todetermine what parameters were most important for the calculation. Problems withthe generation of random samples for the parameters; preconsolidation pressure andlimit pressure were identified, and four different methods of generating the randomsamples were tested, and discussed.The failure probability was calculated as a function of preloading time which wasused to determine what preloading time is needed to fall below the acceptable failureprobability of 5%. The required preloading time was found to be 580 days. Themost important parameters were found to be preconsolidation pressure, the modulusM0 and the coefficient of vertical consolidation.The proposed method is working and has several advantages, among them are theability to calculate the failure probability and the compatibility with the observationalmethod. The model uncertainty has been discussed, and a general commentis that with more research can the model uncertainty be decreased. Only 1D consolidationis considered in the method, this simplification is very practical as 2D and3D effects often can be neglected.