1,721,025 research outputs found
Mechanisms of Earthquake-Induced Landslides: Insights in Field and Laboratory Investigations
No full textIn this lecture, the author will share his experience in investigating several earthquake-induced landslides that occurred in Japan, Indonesia, and China, and discuss the mechanisms of slope failures and contributing factors. This work will present data from reconnaissance field surveys conducted at landslide sites and analysis of geological conditions related to slope instability. It will also discuss the results from a series of laboratory tests performed on soil specimens subjected to various loading modes and issues that may occur during investigations. This lecture will be of interest to researchers in the field of soil dynamics as well as engineers and decision-makers who are interested in the causes and mechanisms of earthquake-triggered landslides.Full Tex
Prediction of Shallow Rainfall-Induced Landslides Using Shear Strength of Unsaturated Soil
No full textRainfall-induced landslides occur more often with climate change, resulting in destruction and loss of lives in many parts of the world. Predicting such landslides is paramount to maintain local infrastructure and the well-being of communities. Several models have been proposed in the past years; however, most of them only work well when being applied to local site conditions for which they were developed. This work describes a new approach to estimate a model parameter related to shear strength conditions of local soils. To validate the theoretical concepts of a model, a series of shear box and undrained triaxial tests were conducted on soil specimens prepared at different values of water content. The refined model was then applied to three landslide sites to estimate the stability of slopes against past rainfall events. The obtained results showed more accurate predictions of landslide occurrence compared to the existing models. This paper presents and discusses field and laboratory data as well as the outcomes of numerical analysis.Full Tex
Coupled thermo-mechanical constitutive damage model for sandstone
No full textUnderground rock dynamic disasters are becoming more severe due to the increasing depth of human operations underground. Underground temperature and pressure conditions contribute significantly to these disasters. Therefore, it is important to understand the coupled thermo-mechanical (TM) behaviour of rocks for the long-term safety and maintenance of underground tunnelling and mining. Moreover, investigation of the damage, strength and failure characteristics of rocks under triaxial stress conditions is important to avoid underground rock disasters. In this study, based on Weibull distribution and Lemaitre's strain equivalent principle, a statistical coupled TM constitutive model for sandstone was established under high temperature and pressure conditions. The triaxial test results of sandstone under different temperature and pressure conditions were used to validate the model. The proposed model was in good agreement with the experimental results up to 600 °C. The total TM damage was decreased with increasing temperature, while it was increased with increasing confining pressure. The model's parameters can be calculated using conventional laboratory test results.Full Tex
Effects of pre-existing cracks and infillings on strength of natural rocks – Cases of sandstone, argillite and basalt
No full textThis study aims to examine the influence of pre-existing discontinuities on the strengths of four natural rocks of different origins. A series of unconfined compression tests was performed on specimens of two types of sandstones, argillite and basalt that contain open and filled cracks. It was found that the presence of cracks tends to decrease the overall strength for all studied rocks; however, the magnitude of strength reduction is related to the property of rock. The larger strength decrease was observed for the relatively harder argillite and basalt, compared to the softer sandstone. It was also found that the infill material could increase the strength of rock specimens, while the obtained strength depended on the characteristics of the fill material.Full Tex
Effect of Geosynthetics on Swell Reduction During an Extreme Rainfall Event
No full textExpansive (reactive) soils can swell during rainfall causing damage to engineering structures. This paper seeks to investigate the effect of geosynthetic material on the swell reduction of such soils. A series of large-scale long-term soil column experiments were conducted on a very high plasticity reactive soil under simulated rainfall conditions. Non-woven geosynthetics combined with geogrid and woven geosynthetics were used as primary geosynthetic material to provide reinforcement and drainage for the soil mass. The obtained results revealed that these geosynthetics did not improve the California Bearing Ratio values of the soil. However, when placed in the soil mass, the geosynthetic materials greatly reduced the total swell of the soil. Visual observations and the experimental data on water content, suction, and vertical displacements indicated that the geosynthetics provided better drainage of the soil mass. This limited the time of water–soil interaction, thus reducing the total swell of the soil.Full Tex
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Engineering properties of sandstone heated to a range of high temperatures
No full textThis study is an investigation of the effect of high temperatures on the engineering properties of sandstone. The rock was first subjected to a range of temperatures such as 25 °C, 200 °C, 400 °C, 600 °C and 800 °C, and a series of porosity, unconfined compression, X-ray diffraction and scanning electron microscope tests were then performed on the heated specimens. In addition, sandstone specimens were also subjected to different numbers (i.e. 1, 2, 4, 6 and 10) of thermal cycles to better understand the effect of high temperature variations on rock behaviour. It was observed that high temperature in the range of 200–400 °C had some influence on the rock properties; that is, the porosity slightly decreased while the strength of the rock increased. However, for T ≥ 600 °C, there was a significant increase in rock porosity that correlated with a decrease in rock strength. The observed changes in engineering properties were attributed to the changes in rock mineralogy and microstructure that occurred at T > 600 °C where the major minerals underwent the process of phase transformation and a significant increase in rock cracking. Regardless of the temperature, almost all specimens failed in tension during unconfined compression. The effect of thermal cycles was seen in a progressive increase in rock porosity and a corresponding decrease in the elastic modulus of the rock.Full Tex
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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