scholarly journals Stability Assessment and Geomorphological Evolution of Sea Natural Arches by Geophysical Measurement: The Case Study of Wied Il-Mielah Window (Gozo, Malta)

2021 ◽  
Vol 13 (22) ◽  
pp. 12538
Author(s):  
Giovanni Leucci ◽  
Raffaele Persico ◽  
Lara De Giorgi ◽  
Maurizio Lazzari ◽  
Emanuele Colica ◽  
...  
Keyword(s):  
Methodological Approach ◽  
Western Coast ◽  
The North ◽  
Open Sea ◽  
Passive Seismic ◽  
Geophysical Measurement ◽  
Natural Monument ◽  
The Stability ◽  
Geomorphological Evolution ◽  
Ground Penetrating

The Wied il-Mielaħ Window (Gozo–Malta) is a limestone natural arch on the north-western coast of the island of Gozo in Malta. It is located at the end of the Wied il-Mielaħ valley north of the village of Għarb. This natural arch is less well known than the Azure Window, which collapsed in March 2017 following a heavy storm, but notwithstanding, it is an imposing and important natural monument too. In the past, the Wied il-Mielah valley was responsible for discharging wastewater from the surrounding localities to the Mediterranean directly at the Wied il-Mielah Window. The sewage flag was often clearly visible underneath the archway into the open sea. The natural features of the arch provide an outstanding touristic attraction. To avoid what happened to the Azure Window, a methodology for the evaluation of the collapse hazard, combining passive seismic, ground penetrating radar (GPR), geological/geomorphological surveys and mine engineering methods, is here proposed. In this study, a methodological approach was applied, based on the following: (i) passive seismic method to study the physical–mechanical characteristics of the rock mass that constitutes the window; (ii) GPR method in order to demonstrate the conservation state (i.e., the intensity of fracturing); (iii) geological/geomorphological surveys in order to obtain a crack pattern; and (iv) scaled span empirical analysis in order to evaluate the stability of the arch. The calculation of the safety factor, with a static method, gave a value equal to 3.75 with a probability of collapse of the marine arch within 50 and 100 years.

On-Bottom Stability Analysis for a Pipeline on a Mobile Seabed

2012 ◽  
Author(s):  
Scott Y. McMaster ◽  
Dermot O’Brien ◽  
David E. Scholtz ◽  
Jay R. Ryan
Keyword(s):  
Physical Model ◽  
Model Testing ◽  
Western Coast ◽  
Design Storm ◽  
The North ◽  
Physical Model Tests ◽  
Overall Stability ◽  
Two Factors ◽  
3D Fea ◽  
The Stability

This paper describes the work performed to assess the stability of an existing pipeline off the North Western coast of Western Australia. Originally, the pipeline was post-trenched (for stability), by ploughing. The plough formed an open v-shaped trench below the pipeline. Several years after the pipeline was installed, a severe cyclone caused significant changes to the seabed along the pipeline. The v-shaped ploughed trench is generally no longer visible with the trench backfilled in places and the pipeline exposed in others. In addition to this, the embedment profile either side of the pipeline was often found to be assymetrical, with higher embedment on one side of the pipeline relative to the other. Current on-bottom stability guidelines and recommended practices do not account for the effects of assymetrical embedment and seabed mobility (Ref. 5). These two factors are believed to contribute significantly to the overall stability of the pipeline. Consequently, it was decided to use physical model testing to obtain a better understanding of hydrodynamic loading and changes in embedment over the duration of a design storm. The physical model testing was performed for various pipeline embedment profiles. The results of these 2D physical model tests were then applied to the 3D FEA on-bottom stability software, CORUS 3D. This paper provides a detailed description of the physical model testing program performed as part of the pipeline stability assessment. The method used to combine the results of the physical model testing and apply them to the 3D FEA on-bottom stability software is also presented.

scholarly journals I. On the laws of the tides on the coasts of Ireland, as inferred from an extensive series of observations made in connection with the ordnance survey of Ireland

1845 ◽  
Vol 135 ◽  
pp. 1-124 ◽  
Keyword(s):  
Accurate Determination ◽  
High Water ◽  
Eastern Coast ◽  
Western Coast ◽  
Ordnance Survey ◽  
The North ◽  
Small Depth ◽  
Open Sea ◽  
The Difference ◽  
Hydrostatic Level

In the spring of 1842 I was informed by Colonel Colby, R. E., Director of the Trigonometrical Survey, that in the operations of the Survey of Ireland it had become necessary to adopt a line of reference for the elevations ascertained in the running of various lines of level through the country; and that it was his intention to institute a series of observations of the height of the water in different states of the tide, in order to refer the levels to the mean height of the sea, or to its height at some definite phase of the tide. Colonel Colby stated also that he was desirous that the observa­tions should be made subservient to improvements in the theory of the tides, and requested my assistance in sketching a plan of observation which would be most likely to contribute to that end. In reply, I made the following suggestions:—That great care should be taken in the accurate determination of time at every station, and that for this purpose the non­commissioned officer of the Royal Sappers and Miners who had the care of the observations at each station, should be entrusted with a pocket chronometer, and that an officer should, at least twice during the series of observations, visit every station, carrying, for comparison, an itinerant chronometer whose error on Greenwich time was accurately known from astronomical observations. That stations should be chosen on the eastern as well as on the western coast, in order to determine the difference of level, if any, between an open sea and a partially inclosed sea. That on the north-eastern coast, stations should be selected at smaller intermediate distances than at other parts of the coast, with the purpose of removing, if possible, the doubt which appears to exist as to the progress of the semidiurnal tide-wave through the North Channel. That, where practicable, several stations should be selected on each of the large rivers or estuaries, in order to ascertain the nature of the modification which the tide-wave undergoes in passing up a contracted channel of comparatively small depth. That the series of observations should be so arranged, that, at every station, one complete tide (from high water to high water, or from low water to low water) should be completely observed on every day, its observations being made at small equidistant intervals. That supplementary observations, applying only to the neighbourhood of the low water or high water omitted in the observations of the complete tide, should also be made, for the development of the principal facts of diurnal tide. Finally, that the zeros of the tide-gauges should be connected with the principal lines of level, so that every observation should be referred to the same hydrostatic level.

scholarly journals GEOTEXTILE TUBE REVETMENT WITH TETRAPODS IN MAYU ISLAND, MYANMAR

2020 ◽  
pp. 11
Author(s):  
Hein Thit Aung ◽  
Chit Yan Toe ◽  
Hendra Hidayat
Keyword(s):  
Bay Of Bengal ◽  
Weather Conditions ◽  
Small Island ◽  
Western Coast ◽  
The North ◽  
Geotextile Tube ◽  
Total Destruction ◽  
Open Sea ◽  
Navy Personnel ◽  
North Western

Mayu Island (formerly known as Oyster Island) is a very small island of 7,284 squared-meter located off the north-western coast of Myanmar, Bay of Bengal. In mid-April 2006, Cyclone Mala had caused partial damages to the stone revetment. Over the years, the raft foundation of the lighthouse was badly affected and starting to give way. In addition, the safety of the Navy personnel stationed on the island is a major concern as well. Therefore, rectification works has to be carried out to protect the island from total destruction. This paper presents the proven viability of integrating geotextiles tubes into a rock revetment facing harsh weather conditions from the open sea, and the fastest method of filling up geotextile tubes.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/fsTsdqbVAc4

scholarly journals Basal seismicity of the Northeast Greenland Ice Stream

2020 ◽  
Vol 66 (257) ◽  
pp. 430-446 ◽  
Author(s):  
Ian W. McBrearty ◽  
Lucas K. Zoet ◽  
Sridhar Anandakrishnan
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Outlet Glacier ◽  
North East ◽  
The North ◽  
Ice Stream ◽  
Long Duration ◽  
Passive Seismic ◽  
Spatio Temporal ◽  
Ground Penetrating

AbstractSeismic studies of glaciers yield insights into spatio-temporal processes within and beneath glaciers on scales relevant to flow and deformation of the ice. These methods enable direct monitoring of the bed in ways that complement other geophysical techniques, such as geodetic or ground penetrating radar observations. In this work, we report on the analysis of passive seismic data collected from the interior of the North East Greenland Ice Stream, the Greenland ice sheet's largest outlet glacier. We record thousands of basal earthquakes, many of which repeat with nearly identical waveforms. We also record many long-duration glacial tremor episodes that migrate across the seismic network with slow velocities (e.g. ~4–12 m s−1). Analysis of the basal earthquakes indicates a transition between times of individual event activity and times of tremor activity. We suggest that both processes are produced by shear slip at localized asperities along the bed. The transition between discrete and quasi-continuous slipping modes may be driven by pore-water pressure transients or heterogeneous strain accumulation in the ice due to strength contrasts of the underlying till.

The New Swedish Cyprus Expedition 2010. Excavations at Dromolaxia Vizatzia/Hala Sultan Tekke. Preliminary results

2011 ◽  
Vol 4 ◽  
pp. 69-98 ◽  
Author(s):  
Peter M. Fischer ◽  
Patrik Klingborg ◽  
Fanny Kärfve ◽  
Fredrika Kärfve ◽  
C. Hagberg ◽  
...  
Keyword(s):  
Ground Penetrating Radar ◽  
Main Task ◽  
Phase 2 ◽  
The North ◽  
12Th Century ◽  
Area 6 ◽  
Recent Phase ◽  
The Rich ◽  
Ground Penetrating

Determination of the complete occupational sequence of the site, including investigation of pre-12th century levels which were thoroughly studied by P. Åström since the 1970s, is the main task of the planned project. During the course of the expedition (NSCE11) in spring 2010 a ground-penetrating radar survey (GPR) was carried out at Dromolaxia Vizatzia/Hala Sultan Tekke in Area 6, leading to the discovery of a large Late Cypriote complex. The compound is bordered to the north by a substantial wall, against which nine rooms (so far) could be exposed. Two occupational phases have been verified but there are indications of a third. The suggested functions of the various structures of the most recent phase are: living, working, storage and administration spaces. The rich find contexts point to the production of textiles and metal objects, and the locally produced pottery is generally of a high quality. There are also many imports, mainly from the Mycenaean sphere of culture. The locally produced vessels from Phase 2 include the “Creature krater” which is a masterpiece of a high artistic standard. Another piece of elevated artistry is the piece of a “Warrior vase”.

MONITORING THE DYNAMICS OF THERMOABRASION COASTS AT KHARASAVEY AREA, WESTERN YAMAL (KARA SEA)

2017 ◽  
Author(s):  
Dmitry Kuznetsov ◽  
Dmitry Kuznetsov ◽  
Anatoliy Kamalov ◽  
Anatoliy Kamalov ◽  
Nataliya Belova ◽  
...  
Keyword(s):  
Human Impact ◽  
Remote Sensing Data ◽  
Kara Sea ◽  
Motor Vehicles ◽  
Yamal Peninsula ◽  
Western Coast ◽  
Frozen Ground ◽  
Coastal Dynamics ◽  
The North ◽  
Ice Content

The dynamics of thermoabrasion coasts on loose sediments under permafrost conditions are highly variable due to several factors: length of the dynamic period of the year, mechanic composition of the frozen ground and its ice content, hydrometeorological conditions, and human impact. Multiannual monitoring of the coastal zone was carried out by Lab. Geoecology of the North (Moscow State University) at the 22 km long Kharasavey deposit site, Western Coast of Yamal Peninsula (Kara Sea). The methods include direct measurements and observations (repeated topographic survey of shore transects from 1981 to 2012) along with remote sensing data analysis (images from 1964 to 2011). This allowed producing detailed characteristics of coastal dynamics. At the site, thermoabrasion coasts occupy the most part, and accumulative coasts are present in the north. Data on natural relief forming factors and ground composition are included in the detailed geomorphologic map of the site. Shore retreat rate shows correlation to amounts of wind-wave energy and to specific wind directions. Human impact on the coast includes dredging at the port channel, mining of sand, driving motor vehicles, and deposition of construction debris. Relations between shore retreat rate and aforementioned factors were studied, including dependencies on ice content, and shore segmentation was carried out. This allows for coastal dynamics forecasts in the region.

Subglacial topography and thickness of ice caps on the Argentine Islands

2019 ◽  
Vol 31 (6) ◽  
pp. 332-344 ◽  
Author(s):  
Jānis Karušs ◽  
Kristaps Lamsters ◽  
Anatolii Chernov ◽  
Māris Krievāns ◽  
Jurijs Ješkins
Keyword(s):  
Land Surface ◽  
Geological Structure ◽  
Aerial Images ◽  
Ice Thickness ◽  
Ice Caps ◽  
The North ◽  
Prevailing Wind Direction ◽  
Aerial Vehicle ◽  
Subglacial Topography ◽  
Ground Penetrating

AbstractThis study presents the first subglacial topography and ice thickness models of the largest ice caps of the Argentine Islands, Wilhelm Archipelago, West Antarctica. During this study, ground-penetrating radar was used to map the thickness and inner structure of the ice caps. Digital surface models of all studied islands were created from aerial images obtained with a small-sized unmanned aerial vehicle and used for the construction of subglacial topography models. Ice caps of the Argentine Islands cover ~50% of the land surface of the islands on average. The maximum thickness of only two islands (Galindez and Skua) exceeds 30 m, while the average thickness of all islands is only ~5 m. The maximum ice thickness reaches 35.3 m on Galindez Island. The ice thickness and glacier distribution are mainly governed by prevailing wind direction from the north. This has created the prominent narrow ice ridges on Uruguay and Irizar islands, which are not supported by topographic obstacles, as well as the elongated shape of other ice caps. The subglacial topography of the ice caps is undulated and mainly dependent on the geological structure and composition of magmatic rocks.

scholarly journals Evidence of Unknown Paleo-Tsunami Events along the Alas Strait, West Sumbawa, Indonesia

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 46
Author(s):  
Bachtiar W. Mutaqin ◽  
Franck Lavigne ◽  
Patrick Wassmer ◽  
Martine Trautmann ◽  
Puncak Joyontono ◽  
...  
Keyword(s):  
Radiocarbon Dating ◽  
Pyroclastic Flows ◽  
Western Coast ◽  
Eastern Shore ◽  
Tsunami Deposits ◽  
The West ◽  
Marine Deposits ◽  
Sedimentary Records ◽  
The North ◽  
Large Earthquakes

Indonesia is exposed to earthquakes, volcanic activities, and associated tsunamis. This is particularly the case for Lombok and Sumbawa Islands in West Nusa Tenggara, where evidence of tsunamis is frequently observed in its coastal sedimentary record. If the 1815 CE Tambora eruption on Sumbawa Island generated a tsunami with well-identified traces on the surrounding islands, little is known about the consequences of the 1257 CE tremendous eruption of Samalas on the neighboring islands, and especially about the possible tsunamis generated in reason of a paucity of research on coastal sedimentary records in this area. However, on Lombok Island, the eruption of the Samalas volcano produced significant volumes of pyroclastic flows that entered the sea in the North and East of the island. These phenomena must have produced a tsunami that left their traces, especially on Sumbawa Island, whose western coastline is only 14 km away from Lombok’s eastern shore. Therefore, the main goal of this study is to investigate, find evidence, and determine the age of marine-origin sediments along the shore of the Alas Strait, Indonesia. We collected and analyzed samples of coral and seashells from marine deposits identified along the west coast of Sumbawa, i.e., in Belang Island and abandoned fishponds in Kiantar Village, in order to identify the sources and the occurrence period of these deposits events. Based on the radiocarbon dating of coral and seashell samples, we concluded that none of the identified marine deposits along the western coast of Sumbawa could be related chronologically to the 1257 CE eruption of Samalas. However, possible tsunami deposits located in Belang Island and abandoned fishponds in Kiantar Village yielded 4th century CE, 9th century CE, and 17th century CE. We also conclude that past large earthquakes triggered these tsunamis since no known volcanic eruption occurred near the Alas Strait at that time that may have triggered a tsunami.

Assessing the temporal reliability of rhythm metrics

2011 ◽  
Vol 41 (3) ◽  
pp. 271-281 ◽  
Author(s):  
Rachael-Anne Knight
Keyword(s):  
Current Paper ◽  
Empirical Measure ◽  
The Sun ◽  
British English ◽  
The North ◽  
North Wind ◽  
The Stability ◽  
Current Popularity ◽  
Temporal Reliability

Despite the current popularity of rhythm metrics, there has been relatively little work aimed at establishing their validity or reliability, important characteristics of any empirical measure. The current paper focuses on the stability, or temporal reliability, of rhythm metrics by establishing if they give consistent results for the same speakers, in the same task, on successive occasions. Four speakers of Southern British English were recorded reading ‘The North Wind and the Sun’ (NWS) passage on three consecutive days. Results indicated that some measures correlate more highly across time than others, and the choice of a measure that is both reliable and valid is discussed. It is suggested that the metric that best fits these criteria is formulated in terms of the proportion of vowels within an utterance (%V).

Nondestructive Test on Typical Roadway Supports of a Mine via Drilling Core and Ground Penetrating Radar

2011 ◽  
Vol 368-373 ◽  
pp. 2411-2416
Author(s):  
Jian Ping Han ◽  
Hai Peng Liu
Keyword(s):  
Ground Penetrating Radar ◽  
Geological Structure ◽  
Surrounding Rock ◽  
Potential Threat ◽  
Real Performance ◽  
Design Requirements ◽  
And Performance ◽  
The Stability ◽  
Ground Penetrating ◽  
Drilling Core

Temporary or permanent supports are necessary in underground construction for maintaining the stability and limiting the damage of surrounding rock. Due to the uncertainty of geological structure, the specificity of the underground environment as well as other factors, the quality and performance of supporting structure are often difficult to satisfy the design requirements, which not only seriously affects the normal construction and operation of mines but also has the potential threat to the safety of underground production. In order to investigate the influence of the unfavorable geologic environment on supporting concrete and evaluate the real performance of roadway supports of a mine, 17 typical projects were chosen and the strength of supporting concrete was detected by nondestructive drilling core method. The result shows that the strength is widely less than the design value. Furthermore, 4 projects of them were investigated by the ground penetrating radar (GPR) in order to evaluate the feasibility of GPR in the performance investigation of the roadway supports of a mine. The results indicate that ground penetrating radar is capable of measuring the thickness of the support, the distribution of rebars and the defects of the surrounding rock.

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