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Abstract

There are many problems associated with the surrounding rocks of the gob-side entry retaining by roof cutting (GERRC) as they are difficult to stabilise in deep mines. The following needs to be studied to understand the problems such as the pressure relief mechanism, evolution law of the surrounding-rock stress and the key technologies of GERRC in deep mines. Cracks are formed by advanced directional blasting to sever the path of stress transmission from the roof of the goaf to the roof of the entry and reduce the lateral cantilever length of the roof. Therefore the surrounding-rock stress and roof structure are optimised. The broken and expanded gangue formed by the collapse of the strata in the range of roof cutting fills the mining space adequately, which avoids a rapid pressure increase caused by the roof breaking impact and slows down the movement of overlying strata. The deformation of the deep surrounding rocks is transformed from “abrupt” to “slow”, and the surrounding-rock deformation of the retained entry in deep mines is significantly reduced. The average pressure and periodic pressure of the supports near the blasting line can be reduced by the blasting cracks to a certain extent, mainly due to the reduction of the length of the immediate roof cantilever and the effective load of the main roof. The combined support technologies for GERRC in deep mines were proposed, and field tests were performed. The monitoring results show that the coordinated control system can effectively control the deformation of deep rock masses, and all indexes can meet the requirements of the next working face after the retained entry is stabilised.
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Authors and Affiliations

Shangyuan Chen
1
ORCID: ORCID
Qian Lv
1
ORCID: ORCID
Yue Yuan
2
ORCID: ORCID

  1. School of Civil and Architectural Engineering, Anyang Institute of Technology, Anyang, Henan 455000, China
  2. Work Safety Key Lab on Prevention and Control of Gas and Roof Disasters for Southern Coal Mines, Hunan University of Science and Technology, Xiangtan Hunan 411201, China
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Abstract

The δ18O data for the last 8000 years in the Greenland NGRIP1, GRIP, DYE-3 and GISP2 ice cores have been analyzed stratigraphically in search of potentially meaningful boundaries and units. Pattern matching of the profiles is supported by using graphical display enhancements, calculating spectral trend curves and generating a compound profile. Techniques routinely used in subsurface geology have been applied in correlating the profiles. Four major stratigraphic units are identified (8.1–4.9, 4.9–3.3, 3.3–1.9 and 1.9–0.1 ka b2k), resulting in an improved understanding of the climate change after the Holocene Climate Optimum. Correlatable higher-order boundaries are identified within these units. The layers between the boundaries show δ18O patterns which generally are similar in character, the differences being ascribed to lateral variations in the factors that control the isotope content of the ice. The layering forms a series of short-lived low-amplitude aperiodic oscillations on a centennial time scale. The suggestion is that these higher-order boundaries and δ18O oscillations have climatic significance. Equivalent units are tentatively identified in ice-core data from the Agassiz and Renland ice caps. Comparison with other climate proxies or stratigraphies from the Northern Hemisphere is expected to render support for the here proposed scheme. It will then serve to guide and constrain the analysis of the dynamics of the climatic fluctuations for the study period.

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Authors and Affiliations

Matheus G.G. De Jong
Arie C. Seijmonsbergen
Leo W.S. De Graaff
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Abstract

The author applies terminology and methods employed in legal theory (i.e. superflua, practical inconsistencies, legal gaps) to laws on protection o f marine environment. The central question is whether there is overabundance o f rules on the subject, including rules o f law, and whether such overabundance is detrimental. The problem is explicated by the case o f Dębki (Krokowa County), a remarkably beautiful marine ecosystem west of Władysławowo, where an initiative to construct 33 wind turbines towering 150 meters within 5 kilometers from the coastline evoked civil protests. The debate was sparked by a controversial decision o f 9 September 2009 by Regional Director for Environmental Protection. The author explores general issues of civic participation and property dispute in the context o f environmental protection.

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Authors and Affiliations

Piotr Lewandowski

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