Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaf 113. / by Bak Kong Low. / M.S.

No description available.

Rockfall from rock slopes adjacent to roadways is a major hazard and poses a problem for transportation agencies across the country. The state of Tennessee has implemented the Tennessee Rockfall Management System (RMS) as a means of reducing the liabilities associated with rockfall hazard. It utilizes digital data acquisition via PDAs coupled with distribution via an expandable web-based GIS database. The Tennessee Rockfall Hazard Rating System (RHRS) is part of the Tennessee RMS and assigns a numeric hazard rating according relative hazard for all slopes identified as having a high potential for delivering rock blocks onto Tennessee Department of Transportation maintained roadways. The Tennessee RHRS uses standard rock slope failure mechanisms (planar failure, wedge failure, topple failure, differential weathering, and raveling) along with the site and roadway geometry to assess the rockfall hazard of an individual slope. This study suggests methods that will expedite fieldwork, including an informational guide on how to properly identify individual failure mechanisms in the field. Also, the study examines the current method of scoring abundance and suggests an alternative, multiplicative approach. The alternative of using a multiplicative abundance is considered and its results summarized. / Master of Science

No description available.

Slope stability assessments are classical problems for geotechnical engineers. The predictions of slope stability in soil or rock masses play an important role when designing for dams, roads, tunnels, excavations, open pit mines and other engineering structures. Stability charts continue to be used by engineers as preliminary design tools and by educators for training purposes. However, the majority of the existing chart solutions assume the slope problem is semi-infinite (plane-strain) in length. It is commonly believed that this assumption is conservative for design, but non-conservative when a back-analysis is performed. In order to obtain a more economical design or more precise parameters from a back-analysis, it is therefore important to quantify three dimensional boundary effects on slope stability. A significant aim of this research is to look more closely at the effect of three dimensions when predicting slope stability. In engineering practice, the limit equilibrium method (LEM) is the most popular approach for estimating the slope stability. It is well known that the solution obtained from the limit equilibrium method is not rigorous, because neither static nor kinematic admissibility conditions are satisfied. In addition, assumptions are made regarding inter slice forces for a two dimensional case and inter-column forces for a three dimensional case in order to find a solution. Therefore, a number of more theoretically rigorous numerical methods have been used in this research when studying 2D and 3D slope problems. In this thesis, the results of a comprehensive numerical study into the failure mechanisms of soil and rock slopes are presented. Consideration is given to the wide range of parameters that influence slope stability. The aim of this research is to better understand slope failure mechanisms and to develop rigorous stability solutions that can be used by design engineers. The study is unique in that two distinctly different numerical methods have been used in tandem to determine the ultimate stability of slopes, namely the upper and lower bound theorems of limit analysis and the displacement finite element method. The limit equilibrium method is also employed for comparison purposes. A comparison of the results from each technique provides an opportunity to validate the findings and gives a rigorous evaluation of slope stability.

The line mapping method of Piteau and Martin (1977) was tested on two different rock type road cuts in the Siskiyou National Forest, and was found to be an efficient means of collecting geological data for rock slope stability analysis. The unbiased approach of this method calls for close scrutiny of the outcrops in question, covering more ground than other methods in less time. In turn, this close attention to every crack in the outcrop reveals more about the stability of the slope, and can reveal hidden hazards of rock fall. The supportive systems for analyzing the data - stereonets and computer program packages of Watts (1986) - led to the discoveries of several potential plane and wedge failures which were not initially visible. Also revealed was the fairly stable condition of the massive wedge at Elk River, which appeared to be extremely hazardous. Each potential failure was analyzed for its Factor of Safety under dry and water saturated conditions, and the cohesion necessary to maintain stability was reported.

[pt] O entendimento dos processos que levam à instabilidade de taludes rochosos é de grande importância em análises de risco. Normalmente, desplacamentos e quedas de blocos de rocha ocorrem em épocas sem chuva, levando a crer que existem outros fatores deflagradores que devem ser analisados. Estudos relativamente recentes tem levantado a importância das tensões térmicas na propagação de fissuras e noacúmulo de tensões de tração. De forma a avaliar o impacto da ciclagem térmica sobre a rocha, foram realizadas análises termomecânicas utilizando o software de elementos finitos Abaqus 6.14. Nas simulações efetuadas foram utilizadas geometrias simplificadas, representativas de placas rochosas reais de áreas costeiras do Brasil. O maciço rochoso foi considerado isotrópico e homogêneo e os parâmetros térmicos utilizados (condutividade, calor específico e coeficiente de expansão térmica) foram adotados de acordo com valores obtidos na literatura para rochas de origem e constituição similar às rochas presentes na costa da região sudeste do Brasil (Gnaisses e Granitos). As condições de contorno de temperatura foram obtidas através de campanhas experimentais extraídas de estudo anterior. Admitiu-se ainda, apenas a ocorrência do modo I de propagação de fraturas, sendo a análise da propagação restrita a comparação entre K1c e os valores K1 desenvolvidos. Os resultados das simulações numéricas mostraram que a ocorrência de baixas temperaturas e de altos gradientes térmicos entre as faces externa e interna da placa ocasionam os maiores valores de K1, cuja magnitude é comparável aos valores de K1c típicos para rochas encontradas na região sudeste do Brasil. / [en] The understanding of the processes that lead to instability of rock slopes is of great importance in risk analysis. Normally, detachments and rockfalls occur in times without rain, leading to belief that there are other triggering factors that need to be evaluated. Relatively recent studies have raised the importance of thermal stresses in the propagation of cracks and in the accumulation of tensile stresses. In order to evaluate the impact of thermal cycling on the rock, thermomechanical analyzes were performed using Abaqus 6.14 finite element software. In the simulations, simplified geometries were used, representative of real rock plates of coastal areas of Brazil. The rock mass was considered isotropic and homogeneous and the thermal parameters (conductivity, specific heat and coefficient of thermal expansion) were adopted according to values obtained in the literature for rocks of origin and constitution similar to the rocks present in the coast of the southeastern region of Brazil (Gneisses and Granites). The temperature contour conditions were obtained through experimental campaigns extracted from a previous study. Only the occurrence of mode I of fracture propagation was allowed, with propagation analysis being restricted to the comparison between K1c and the K1 values developed. The results of the numerical simulations showed that the occurrence of low temperatures and high thermal gradients between the outer and inner faces of the plate cause the highest values of K1, whose magnitude is comparable to the values of K1c typical for rocks found in the southeastern region of Brazil.

Includes bibliographical references / xii, [291] leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Civil Engineering, 1992

Infrastructure is developing at an extremely fast pace which includes construction of metros, underground storage places, railway bridges, caverns and tunnels. Very often these structures are found in or on the rock masses. Rock masses are seldom found in nature without joints or discontinuities. Jointed rocks are characterized by the presence of inherent discontinuities of varied sizes with different orientations and intensities, which can have significant effect on their mechanical response. Constructions involving jointed rocks often become challenging jobs for Civil Engineers as the instability of slopes or excavations in these jointed rocks poses serious concerns, sometimes leading to the failure of structures built on them. Experimental investigations on jointed rock masses are not always feasible and pose formidable problems to the engineers. Apart from the technical difficulties of extracting undisturbed rock samples, it is very expensive and time consuming to conduct the experiments on jointed rock masses of huge dimensions. The most popular methods of evaluating the rock mass behaviour are the Numerical methods. In this thesis, numerical modelling of jointed rock masses is carried out using computer program FLAC (Fast Lagrangian Analysis of Continua). The objective of the present study is to study the effect of various joint parameters on the response of jointed rock masses in static as well as seismic shaking conditions. This is achieved through systematic series of numerical simulations of jointed rocks in triaxial compression, in underground openings and in large rock slopes. This thesis is an attempt to study the individual effect of different joint parameters on the rock mass behaviour and to integrate these results to provide useful insight into the behaviour of jointed rock mass under various joint conditions. In practice, it is almost impossible to explore all of the joint systems or to investigate all their mechanical characteristics and implementing them explicitly in the model. In these cases, the use of the equivalent continuum model to simulate the behaviour of jointed rock masses could be valuable. Hence this approach is mainly used in this thesis. Some numerical simulations with explicitly modelled joints are also presented for comparison with the continuum modelling. The applicability of Artificial Neural Networks for the prediction of stress-strain response of jointed rocks is also explored. Static, pseudo-static and dynamic analyses of a large rock slope in Himalayas is carried out and parametric seismic analysis of rock slope is carried out with varying input shaking, material damping and shear strength parameters. Results from the numerical studies showed that joint inclination is the most influencing parameter for the jointed rock mass behaviour. Rock masses exhibit lowest strength at critical angle of joint inclination and the deformations around excavations will be highest when the joints are inclined at an angle close to the critical angle. However at very high confining pressures, the influence of joint inclination gets subdued. Under seismic base shaking conditions, the deformations of rock masses largely depend on the acceleration response with time, frequency content and duration rather than the peak amplitude or the magnitude of earthquake. All these aspects are discussed in the light of results from numerical studies presented in this thesis.

The objective of this thesis was to identify the mechanisms associated with the recurrence of rock-slope instability along the R518 and R523 roads in Limpopo. Advanced geotechnical methods and ASTER imagery were used for the purpose while a predictive rockfall hazard rating matrix chart and rock slope stability charts for unsaturated sensitive clay soil and rock slopes were to be developed. The influence of extreme rainfall on the slope stability of the sensitive clay soil was also evaluated. To achieve the above, field observations, geological mapping, kinematic analysis, and limit equilibrium were performed. The latter involved toppling, transitional and rotational analyses. Numerical simulation was finally resorted to. The following software packages were employed: SWEDGE, SLIDE, RocData, RocFall, DIPS, RocPlane, and Phase 2. The simulation outputs were analyzed in conjunction with ASTER images. The advanced remote sensing data paved the way for landslide susceptibility analysis. From all the above, rockfall hazard prediction charts and slope stability prediction charts were developed. Several factors were also shown by numerical simulation to influence slope instability in the area of study, i.e. sites along the R518 and R523 roads in the Thulamela Municipality. The most important factors are extreme rainfall, steep slopes, geological features and water streams in the region, and improper road construction. Owing to the complexity of the failure mechanisms in the study area, it was concluded that both slope stability prediction charts and rock hazard matrix charts are very useful. They indeed enable one to characterize slope instability in sensitive clay soils as well as rockfall hazards in the study area. It is however recommended that future work is undertaken to explore the use of sophisticated and scientific methods. This is instrumental in the development of predictive tools for rock deformation and displacement in landslide events. / Electrical and Mining Engineering / D. Phil. (Mining Engineering)