1,720,977 research outputs found
Assessment of non-linear rock strength parameters for the estimation of pipe-jacking forces. Part 2. Numerical modeling
No full textIn the earlier companion paper (Ong and Choo, 2018), direct shear tests were performed on reconstituted tunneling rock spoils for the development of equivalent tangential cohesion, c't,p and friction angle, ϕ't,p. These equivalent rock strength parameters were used in assessing jacking forces, which were measured from three pipe-jacking drives negotiating the highly weathered lithologies from the Tuang Formation, Malaysia. The measured jacking forces were back-analyzed, leading to the development of frictional coefficient, μavg and the vertical stress at the tunnel crown, σEV. In this paper, the reliability of using the parameters, c't,p, ϕ't,p, μavg and σEV was assessed through the use of three-dimensional finite element modeling of the studied pipe-jacking drives. The peak tangential strength parameters, c't,p and ϕ't,p were applied to the modeled rock mass and the strength parameters of the pipe-rock interface were developed from μavg. Arching ratios were developed from σEV, which were subsequently used for post-analysis assessment of the results from numerical modeling. There was sound agreement between the resulting pipe-rock interface shear stresses, τ1 and reaction loads, ΣFy from the numerical analysis against the field measured jacking forces, thus demonstrating the reliability of the use of developed equivalent rock strength parameters, c't,p, ϕ't,p, μavg and σEV in the assessment of pipe-jacking forces through highly weathered lithologies.Full Tex
Interpretation of Pressuremeter Test in Fractured and Weathered Phyllite for Back-Analysis of Pipe Jacking Forces
No full textCharacterisation of highly fractured and weathered rock masses within the young Tuang Formation in Sarawak, Malaysia is challenging, mainly due to the difficulties in extracting intact samples for conventional rock testing. Pressuremeter test was used as a viable alternative since it is performed in-situ, hence eliminating the need for sample extraction. A methodology was developed to interpret pressuremeter test results in highly fractured and weathered phyllite using an analytical approach, from which useful strength and stiffness parameters can be obtained. The interpretation method was based on the fundamental theory of cylindrical cavity expansion, which was originally established for soils. The results of the interpretation were in terms of commonly known Mohr–Coulomb strength parameters, which were subsequently used for assessment of frictional pipe jacking forces through back-analysis method. The results of the back-analysis showed the reliability of the developed methodology in analysing pressuremeter test results within highly fractured and weathered phyllite.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
Determination of jacking forces based on highly weathered non-linear 'soft rock' strength parameters considering arching
No full textAs microtunnelling by pipe-jacking continues to remain an efficient method of constructing buried infrastructure in densely populated urban areas, it is paramount to understand the effects of geology on pipe-jacking forces. There continues to be a knowledge gap when understanding the accrual of frictional jacking forces for drives negotiating geological rock formations, particularly highly erratic and highly weathered geology. This paper presents a methodology for understanding the effects of highly weathered geology on pipe-jacking forces. This method was developed during the construction of a 7.7 km long trunk sewer network at depths of up to 30 m below the central business district of Kuching city, Sarawak, Malaysia. At such depths, the encountered lithologies from the Tuang Formation predominantly presented RQD values of 0%, which created difficulties when extracting rock samples for strength characterization. Therefore, excavated tunnelling rock spoils were instead collected and subjected to direct shear testing. The reconstituted tunnelling rock spoils demonstrated behaviour, characteristic of the nonlinear power law. For application to assessment of jacking forces, the developed peak tangential strength parameters, c't,p and ϕ't,p were found to have been closely related to the mineralogy of the respective lithological units, which subsequently affected the lubrication and accrual of jacking forces. This was explained through back-analysed values of pipe-rock frictional coefficient, μavg and vertical stresses at the pipe crown, σEV. These back-analyzed parameters provided insight into the effectiveness of lubrication efforts and the development of arching, which were closely related to the traversed lithologies. It was found that the highly weathered geology was able to arch, suggesting that the highly weathered and discontinuous 'soft rock' masses demonstrated soil-like behaviour.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
Effect of interparticle behavior on the development of soil arching in soil-structure interaction
No full textDirect shear tests have been commonly used to study the frictional stresses during pipe-jacking. Particle angularity and mineralogy will influence the shear strength with apparent cohesion contributing to the arching effect during soil-structure interaction via pipe-jacking. Past researchers found it challenging to physically study particle behavior along the shear band during shearing due to the opaque nature of the equipment. This study used an original transparent shear box to conduct direct shear tests on tunneling rock spoils of sandstone and shale. Sequential images were captured during shearing and analyzed using GeoPIV software to demonstrate localized activities which were found to influence the apparent cohesion. Furthermore, the findings were successfully used to assess the arching phenomenon observed during pipe-jacking and other established pipe-jacking case studies. Rounded particles with strong mineralogy were found to be more likely to produce an arching effect as compared to angular particles with weaker minerals.No Full Tex
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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