Full-scale load testing of two large-diameter drilled shafts in coral-reef limestone formations

Some U.S. transportation agencies have recently applied mass concrete provisions to drilled shafts, imposing limits on maximum temperatures and maximum temperature differentials. On one hand, temperatures commonly observed in large-diameter drilled shafts have been observed to cause delayed ettringite formation (DEF) and thermal cracking in above-ground concrete elements. On the other, the reinforcement and confinement unique to drilled shafts should provide resistance to thermal cracking, and the provisions that have been applied are based on dated practices for above-ground concrete. This paper establishes a rational procedure for design of drilled shafts for durability requirements in response to hydration temperatures, which addresses both DEF and thermal cracking. DEF is addressed through maximum temperature differential limitations that are based on concrete mix design parameters. Thermal cracking is addressed through calculations that explicitly consider the thermo-mechanical response of concrete for predicted temperatures. Results from application of the procedure indicate consideration of DEF and thermal cracking potential for drilled shafts is prudent, but provisions that have been applied to date are overly restrictive in many circumstances, particularly the commonly adopted 35°F maximum temperature differential provision.

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Destress blasting in deep mines of NorNickel’s Polar Division

Gornyi Zhurnal ◽

10.17580/gzh.2021.02.04 ◽

2021 ◽

pp. 32-36

Author(s):

G. V. Sabyanin ◽

S. Yu. Shilenko ◽

A. V. Trofimov ◽

A. P. Kirkin

Keyword(s):

Horizontal Plane ◽

Large Diameter ◽

Geophysical Methods ◽

Full Scale ◽

Underground Mines ◽

Destress Blasting ◽

Drilling Cost ◽

Full Scale Tests ◽

Polar Division ◽

Oktyabrsky Mine

Talnakh and Oktyabrsky ore fields are estimated as rockburst-hazardous starting from the depth of 700 m downward according to safety rules. This means that mining is only permitted within certain protected zones. At the present times, such protected zones are generated in underground mines by means of the large-diameter destressing drilling. Despite proved efficiency, the high cost and large amount of the destressing drilling are the grave faults of this approach. Aiming to save drilling cost, it is proposed to make rock mass rockburst-unhazardous using destress blasting. This article gives a brief description of the destress blasting mechanism. This method has been effectively used in relaxation of pillars from stresses before extraction of the reserves from the pillars both in Russia and abroad. In Oktyabrsky Mine stress relaxation of pillars was implemented by slotting, and the drilling and blasting data were available. This study proposes to destress rock masses by means of directional destress fracturing in horizontal plane through blasting of decked charges of special design. The initial parameters for destress blasting using holes with diameters of 76 and 130 mm are determined. The charge design aimed to ensure a zone of fractures in the horizontal plane, at minimized vertical fracturing is described. This information can be used in planning of full-scale tests to refine parameters and application ranges of the method. For the full-scale tests, it is suggested to undertake destress blasting at different blast patterns on different test sites, and to compare the results with the current destressing method (destressing drilling). Efficiency can be proved using geomechanical and geophysical methods. The authors appreciate participation of V. P. Marysyuk and T. P. Darbinyan from NorNickel’s Polar Division in this study.

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Rigid Inclusions Ground Improvement for a New Energy Facility: Design, Construction, and Full-Scale Embankment Load Testing and Results

Geo-Congress 2019 ◽

10.1061/9780784482117.009 ◽

2019 ◽

Author(s):

David Mazzei ◽

Ken Kniss ◽

Fathey Elsaid ◽

Yan Zhang

Keyword(s):

Ground Improvement ◽

Full Scale ◽

Load Testing ◽

Facility Design ◽

Energy Facility ◽

New Energy ◽

Embankment Load ◽

Design Construction

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Field Study on the Behavior Super-Long and Large-Diameter Grouted Drilled Shafts

Springer Series in Geomechanics and Geoengineering - Proceedings of China-Europe Conference on Geotechnical Engineering ◽

10.1007/978-3-319-97115-5_67 ◽

2018 ◽

pp. 1192-1196

Author(s):

Zhihui Wan ◽

Guoliang Dai ◽

Weiming Gong ◽

Mingxing Zhu

Keyword(s):

Field Study ◽

Large Diameter ◽

Drilled Shafts

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Qualification of UOE SAWL Linepipes With Enhanced Collapse Resistance for Ultra Deepwater Applications

Volume 4B: Pipeline and Riser Technology ◽

10.1115/omae2013-10957 ◽

2013 ◽

Author(s):

Fábio Arroyo ◽

Rafael F. Solano ◽

Luciano Mantovano ◽

Fábio B. de Azevedo ◽

Hélio Alves ◽

...

Keyword(s):

New Technology ◽

Large Diameter ◽

Final Analysis ◽

Load Testing ◽

Offshore Pipelines ◽

Cold Forming ◽

Collapse Resistance ◽

Offshore Pipeline ◽

Key Factor ◽

Combine Load

Large diameter UOE pipes are being increasingly used for the construction of offshore pipelines. Since oil discoveries are moving towards ultra-deepwater areas, such as Pre-Salt in Brazil, collapse resistance is a key factor in the design of the pipelines. It is known that the cold forming, and the final expansion in the UOE linepipe manufacturing process, reduces the elastic limit of the steel in subsequent compression. Due to this, the DNV collapse formula includes a fabrication factor that derates by a 15% the yield strength of UOE Pipes. However, DNV also recognizes the effect of thermal treatments and the code allows for improvement of the fabrication factor when heat treatment or external cold sizing (compression) is applied, if documented. This paper presents the qualification of UOE pipes with enhanced collapse capacity focusing the use of a fabrication factor (αfab) equal to 1. TenarisConfab has performed a technology qualification process according to DNV-RP-A203 standard “Qualification Procedures for New Technology”. The main aspects of the qualification process are presented in this paper which included significant material and full scale testing, including combine load testing, and final analysis. The qualification process achieved successful results and this will allow use of a fabrication factor equal to 1 directly in deepwater and ultra-deepwater offshore pipeline projects with a possible reduction in material and offshore installation costs and also potentially enhancing the feasibility of many challenging offshore projects.

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Cost Effective Fabrication of Large Diameter High Strength Titanium Catenary Riser

21st International Conference on Offshore Mechanics and Arctic Engineering, Volume 3 ◽

10.1115/omae2002-28445 ◽

2002 ◽

Cited By ~ 2

Author(s):

Agnes Marie Horn ◽

Mons Hauge ◽

Per-Arne Ro̸stadsand ◽

Bjarne Bjo̸rnbakk ◽

Peer Dahlberg ◽

...

Keyword(s):

Fatigue Testing ◽

Fatigue Cracks ◽

Large Diameter ◽

High Strength ◽

Cost Effective ◽

Full Scale ◽

Scale Production ◽

Wear Properties ◽

Field Development ◽

Main Challenge

A large diameter high strength titanium free-hanging catenary riser was evaluated by the Demo 2000 Ti-Rise project, from initiative of the Kristin Field development license. In order to reduce the uncertainties related to the schedule, cost, and special technical issues identified in the work related to a similar riser for future installation on the A˚sgard B semi-submersible platform, a fabrication qualification of a full scale riser in titanium was run. Several full-scale production girth welds were made in an in-situ fabrication environment. The welding was performed on extruded titanium grade 23 (ASTM) pipes with an ID of 25.5″) and wall thickness of 30 mm. The main challenge was to develop a highly productive TIG orbital welding procedure, which produced welds with as low pore content as possible. It is well known that sub-surface pores often are initiation sits for fatigue cracks in high strength titanium welds. This paper describes how a greatly improved productivity was obtained in combination with a high weld quality. NDT procedures were developed whit the main on the reliability to detect and locate possible sub-surface weld defects, volumetric defects such as pores and tungsten particles and planar defects such as lack of fusion. The results from the actual Non Destructive Testing (NDT), the mechanical testing, and the fatigue testing of the subjected welds are presented. The response of the catenary is optimised by varied distribution of weight coating along the riser’s length. A satisfactory weight coating with sufficient strength, bond strength, and wear properties was developed and qualified. The riser is planned to be fabricated from extruded titanium pipes, welded together onshore to one continuous piece. The field coating is added and the riser is loaded into the sea and towed offshore and installed.

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