Pertes de charge des ancrages actifs injectés dans un massif rocheux

1989 ◽  
Vol 16 (1) ◽  
pp. 72-81 ◽  
Author(s):  
Brahim Benmokrane ◽  
Gérard Ballivy

Estimation of loss of prestress is an essential part of the design of permanent or temporary prstressed anchors since stability of the retained structure must not be compromised. Findings of a field study on long-term behaviour of prestressed anchors are presented herein: different lengths of anchors in solid rock were injected with cement grout or epoxy resin. Load variation in the anchors with time indicated two distinct stages of loss of prestress: an initial stage of rapid loss of prestress and a second stage of very minor and uniform loss ending about 6 months after prestressing. Our study also showed that restressing anchors after a period of time reduces subsequent prestress loss and that overdimensioning of the injected length does not. Key words: rock, prestressed injected anchor, grout, loss of prestress, creep, relaxation.

SPE Journal ◽  
2007 ◽  
Vol 12 (03) ◽  
pp. 272-281 ◽  
Author(s):  
Jim Dean Weaver ◽  
Mark Parker ◽  
Diederik W. van Batenburg ◽  
Philip Duke Nguyen

Summary Rapid loss of fracture conductivity after hydraulic fracture stimulation has often been attributed to the migration of formation fines into the proppant pack or the generation of fines derived from proppant crushing. Generation of crystalline and amorphous porosity-filling minerals can occur within the proppant pack because of chemical compositional differences between the proppant and the formation, and the compaction of the proppant bed because of proppant pressure solution reactions. Findings presented in this paper suggest that diagenesis-type reactions that can occur between proppant and freshly fractured rock surfaces can lead to rapid loss of proppant-pack porosity and loss of conductivity. Introduction Lehman et al. (2003) reported that the use of surface-modification agents (SMA) to coat proppants used in propping hydraulic fractures resulted in sustained and more uniform production from wells. Fig. 1, taken from that publication, shows the production decline curves from some of their data, and it does appear to show a significant change in decline rate compared to the use of untreated proppant. This SMA was described as a nonhardening resin that is insoluble in water and oil. It is supplied in a solvent that is quickly extracted once it is introduced to aqueous-based frac fluids, leaving a tacky, hydrophobic coating on the proppant. Initial use of this type of SMA treatment (Dewprashad et al. 1999; Nguyen et al. 1998a, b) was promoted as a method to increase the conductivity of proppant owing to its capability to prevent close packing of the proppant, which can result in increased porosity and permeability of the pack, by rendering the proppant surface tacky. Subsequent studies indicated that its use provided proppant-pack protection from fines infiltration and migration. This mechanism has been employed to explain the observations that sustained production results from the use of SMA on proppants. This is further substantiated by long-term results obtained in a single field study known for fines production problems. That both mechanisms are active has been well established through laboratory studies, but they alone do not completely explain the reduction in production decline rate as reported. A field study of SMA-treated proppant was reported to the Arkansas Oil and Gas Commission 2004 CBM Workshop that disclosed long-term results on gas production. These were CBM wells in the San Juan basin that typically required refracturing each year to produce at an economical rate. With the SMA-treated proppant, no refracs have been required, and as shown in Fig. 2, production has remained essentially constant for 5 to 6 years. This longevity was initially attributed to prevention of fines invasion into the proppant pack; however, it is possible that there are additional mechanisms operational.


1970 ◽  
Vol 16 (2) ◽  
pp. 3-11 ◽  
Author(s):  
H Meilby ◽  
L Puri ◽  
M Christensen ◽  
S Rayamajhi

To monitor the development of four community-managed forests, networks of permanent sample plots were established in 2005 at sites in Chitwan, Kaski and Mustang Districts, Nepal. This research note documents the procedures used when preparing for establishment of the plot networks, evaluates the applied stratification of the forest on the basis of data gathered in pilot surveys conducted in the early 2005, and provides a discussion on the implications of the choices made. Key words: Community-managed forests; permanent sample plots; stratification; allocation; estimates Banko Janakari Vol.16(2) 2006 pp.3-11


2019 ◽  
Vol 19 (28) 2019 ◽  
pp. 169-190
Author(s):  
Dalia Sabaliauskienė

This paper examines the concept and practices of the Iranian ritual courtesy ta’ârof in northern Tehran, based on field-study findings, and analyses its expression in intercultural communication. It examines how contemporary Iranians perceive ta’ârof, what practices of ritual courtesy are commonly found, and whether configurations of the Iranian code of courtesy remain stable in the changing cultural environment. The study employs the theory of face maintenance and data from Iranian face and diaspora research. It shows emic perceptions of ta’ârof, and reveals its practices in Tehran, alongside tendencies of expression among Iranians living in Lithuania. Key words: ta’ârof, ritual courtesy, capital-city culture, intercultural communication, contemporary Iran.


2021 ◽  
pp. 152483802110302
Author(s):  
Caroline Bailey ◽  
Jessica Shaw ◽  
Abril Harris

Adolescents experience alarmingly high rates of sexual violence, higher than any other age-group. This is concerning as sexual violence can have detrimental effects on teens’ personal and relational well-being, causing long-term consequences for the survivor. Still, adolescents are hesitant to report the assault or seek out services and resources. When an adolescent survivor does seek out services, they may interact with a provider who is a mandatory reporter. This scoping review sought to synthesize the current U.S.-based research on the role, challenges, and impact of mandatory reporting (MR) in the context of adolescent sexual assault. Database searches using key words related to MR, sexual assault, and adolescence identified 29 peer-reviewed articles. However, none of these articles reported on empirical investigations of the phenomenon of interest and instead consisted of case studies, commentaries, and position papers. The scoping review was expanded to provide a lay of the land of what we know about the intersection of adolescent sexual assault and MR. Results of the review indicate that though implemented broadly, MR policies vary between individuals, organizations, and states and have historically been challenging to implement due to this variation, conflicts with other laws, tension between these policies and providers’ values, and other factors. Based on the available literature, the impact of MR in the context of adolescent sexual assault is unknown. There is a critical need for research and evaluation on the implementation and impact of MR policies, especially in the context of adolescents and sexual violence.


2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Nasrin Hafezparast ◽  
Ellie Bragan Turner ◽  
Rupert Dunbar-Rees ◽  
Alice Vodden ◽  
Hiten Dodhia ◽  
...  

Abstract Background Defining multimorbidity has proved elusive in spite of attempts to standardise definitions. For national studies, a broad definition is required to capture national diversity. For locally based studies, the definition may need to reflect demographic and morbidity patterns. We aimed to define multimorbidity for an inner city, multi-ethnic, deprived, young age community typical of many large cities. Methods We used a scoping literature review to identify the international literature, standards and guidelines on Long Term Condition (LTC) definitions for inclusion in our multimorbidity definition. Consensus was categorised into high, medium or low consensus, depending on the number of literature sources citing each LTC. Findings were presented to a workshop consisting of local health service stakeholders who were asked to select LTCs for inclusion in a second stage review. In the second stage, each LTC was tested against seven evaluation domains: prevalence, impact, preventability, treatment burden, progression to multiple LTCs, impact on younger people, data quality. These domains were used to create 12 target criteria. LTC rankings according to consensus group and target criteria scores were presented to a second workshop for a final decision about LTC inclusion. Results The literature review identified 18 literature sources citing 86 LTCs: 11 were excluded because they were LTC clusters. The remainder were allocated into consensus groupings: 13 LTCs were ‘high consensus’ (cited by ≥ 11 sources); 15 were ‘medium consensus’ (cited by 5–10 sources); 47 were ‘low consensus’ (cited by < 5 sources). The first workshop excluded 31 LTCs. The remaining 44 LTCs consisted of: 13 high consensus LTCs, all with high target score (score 6–12); 15 medium consensus LTCs, 11 with high target scores; 16 low consensus LTCs, 6 with high target scores. The final workshop selected the 12 high consensus conditions, 12 medium consensus LTCs (10 with high target scores) and 8 low consensus LTCs (3 with high target scores), producing a final selection of 32 LTCs. Conclusions Redefining multimorbidity for an urban context ensures local relevance but may diminish national generalisability. We describe a detailed LTC selection process which should be generalisable to other contexts, both local and national.


Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2218
Author(s):  
Sylwia Słupik ◽  
Joanna Kos-Łabędowicz ◽  
Joanna Trzęsiok

The issue of energy behaviour among Polish consumers, and especially the motives and attitudes they manifest, is relatively under-researched. This article attempts to identify individual attitudes and beliefs of energy consumers using the example of the residents of the province of Silesia (Poland). The authors conducted the expert segmentation of respondents in terms of their motivation for saving energy, based on the results of their proprietary survey. The second stage of the study involved using a classification model that allowed for the characterisation of the obtained groups. Psychological and financial factors were of greatest significance, which is confirmed by the results of other studies. Nonetheless, the obtained results explicitly indicate the specificity of the region, which requires transformation towards a low-emission economy. Despite the initial stage of changes both in the awareness of the consumers and the public interventions of the authorities, it should be emphasized that a majority of the respondents—at least to a basic extent—declared taking energy-saving measures. Financial motives are predominant among the respondents, although pro-environmental motives can also be noticed, which might translate into increased involvement and concern for the environment and climate.


2019 ◽  
Vol 9 (22) ◽  
pp. 4813 ◽  
Author(s):  
Hanbo Yang ◽  
Fei Zhao ◽  
Gedong Jiang ◽  
Zheng Sun ◽  
Xuesong Mei

Remaining useful life (RUL) prediction is a challenging research task in prognostics and receives extensive attention from academia to industry. This paper proposes a novel deep convolutional neural network (CNN) for RUL prediction. Unlike health indicator-based methods which require the long-term tracking of sensor data from the initial stage, the proposed network aims to utilize data from consecutive time samples at any time interval for RUL prediction. Additionally, a new kernel module for prognostics is designed where the kernels are selected automatically, which can further enhance the feature extraction ability of the network. The effectiveness of the proposed network is validated using the C-MAPSS dataset for aircraft engines provided by NASA. Compared with the state-of-the-art results on the same dataset, the prediction results demonstrate the superiority of the proposed network.


2012 ◽  
Vol 65 (10) ◽  
pp. 1895-1902 ◽  
Author(s):  
Rita Hilliges ◽  
Eberhard Steinle ◽  
Bernhard Böhm

The two-staged WWTP ‘Gut Grosslappen’ has a capacity of 2 mio. PE. It comprises a pre-denitrification in the first stage using recirculation from the nitrifying second stage. A residual post-denitrification in a downstream sand filter is required in order to achieve the effluent standards. Presently the process water from sludge digestion is treated separately by nitrification/denitrification. Due to necessary reconstruction of the biological stages, the process water treatment was included in the future overall process concept of the WWTP. A case study was conducted comparing the processes nitritation/denitrititation and deammonification with nitrification/denitrification including their effect on the operational costs of the planned main flow treatment. Besides the different operating costs the investment costs required for the process water treatment played a significant role. Six cases for the process water treatment were compared. As a result, in Munich deammonification can only be recommended for long-term future developments, due to the high investment costs, compared with the nitritation/denitritation alternative realizable in existing tanks. The savings concerning aeration, sludge disposal and chemicals were not sufficient to compensate for the additional investment costs. Due to the specific circumstances in Munich, for the time being the use of existing tanks for nitritation/denitritation proved to be most economical.


1995 ◽  
Vol 75 (3) ◽  
pp. 357-359 ◽  
Author(s):  
E. Bremer ◽  
H. H. Janzen ◽  
E. de Jong

Soil erosion may be difficult to quantify from redistribution of 137Cs at sites where stubble-mulch techniques were adopted prior to 137Cs deposition, because appreciable 137Cs may have been transported before it was mixed into the soil Ap layer. We present evidence that this occurred in two long-term cropping experiments in southern Alberta. Key words: Cesium-137, tillage, long-term crop rotations, fallow


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