CC BY
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UDC 622.755
A.A. Abirov, V.S. Molchanov, E.B. Zharkenov,
D.A. Yegizbaev, B. Esenov, J.M. Omarov, K..B. Suleymenov
the practice of using trenchless technologies for pipeline laying in extreme cold conditions of astana city in kazakhstan
The modern temp of civilization growth require implementation of innovative techniques and methods in all spheres of construction process. Using trenchless technologies for pipeline and other communication lines laying proved to be the best replacementfor an old "open trench" technique. Though trenchless methods have many advantages, they also have limitations connected with risk. Experience of using such methods in a cold climate of Astana city shows that, only by careful assessment of all possible risks and proper planning of a work process, it becomes possible to achieve positive results even in a harsh weather conditions.
Being the capital of the Republic of Kazakhstan, fast growing Astana city faced a need in new pipeline and communication lines laying alongside with renewal of ageing infrastructure. In many cases, "open trench" methods are problematic or not even acceptable for social, economical or ecological reasons. Construction of water supply and sewer water disposal systems is an integral part of the urban and industrial construction process. The rate of the population growth is nearly 45000 people a year that provokes the high speed of the city growth. This forces to conduct construction even in hash weather conditions.
The city is situated in the center of Eurasian continent, what leads to high fluctuations of temperature, humidity and other meteorological elements both during a day and a year. Average air temperature of cold months is -13 -18°C, while for warm months it is+18 +21°C. During hash winters temperature falls down to -49-52°C (absolute minimum). Warm period length is about 200 days. Depth of frost penetration is within 2-2,5 meter range.
Great achievements and developments have been done in trenchless technology for the last 30 years mainly in European countries and North America. While research being conducted mainly in countries with moderate climate conditions, the vector of developments is aimed at pipeline laying during warm periods of year. Only recently our industry has forced research groups and equipment constructors and engineers to adapt trenchless technologies to cold climate conditions. Experience of Russian colleagues in trenchless
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technology was firstly shown in "No-Dig" annual conference in 2008 which showed the wide specter of equipment and techniques [1].
Below is an overview of trenchless experience gained in Astana which was based on the foreign, mainly Russian experience. Extremely low temperatures down to -30°C make engineers think of possible and negative consequences of conducting a work in such severe conditions. Moreover, it is interesting to mention that trenchless pipeline laying can even be advantageous for cold climate regions [3].
Microtunneling
Several microtunneling projects have been implemented in Astana during winter time. Such technique was used to install a water supply pipeline under the road. High traffic load of one of the main roads didn't allow to use "open trench" technique thus forcing to use trenchless method. Microtunneling technology was firstly put into practice. Laser guided boring machine was used allowing to control the boring process accurately achieving desirable grade and alignment. At the beginning stage, in order to build starting and receiving shafts in the frozen ground more force were applied comparing to the warm period, thus pick hammers and heavy excavators were used.
Two types of spoil removal systems were tested in microtunneling projects in Astana: slurry and auger removal systems.
Soil skip or
Figure 1 - Used scheme of microtunneling (slurry removal system)
The work site with all surface equipment was tented; several heaters were installed under the tent to make the working environment less cruel
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both for the crew and equipment. The main problem that could have been met by the workers was the possibility of slurry freezing down. While the outside temperature being around -30°C, climate under the tent and in the shafts was around 0°C.
Though such conditions were fairly enough for the circulating bentonite mixture not to freeze down, there were always a possibility for climate to become worse. Thus to prevent the possibility of some parts of the system become over frozen especially during night cold, Ditch Witch drillmud heaters were installed to keep the bentonite mud warm and liquid (Fig. 2).
Implementing drillmud heating equipment in the circulating system gave several benefits:
- increasing uptime, eliminating downtime due to some operations for unfreezing of some parts;
- full utilization of the drilling mud;
- preventing over freezing of parts of equipment;
- temperature control helps to achieve high quality of bentonite mud, increasing its soil removal capability.
Figure 2 - "YUKON" drill mud heating unit
In another case auger soil removing system were used in microtunneling process of water pipeline construction. As while using the slurry soil removing system, the work site was tented and heated. Comparing to the "slurry" method, this method proved to be less capricious. There was no need to install additional heaters and control temperature of a slurry mixture, which led to an increase in a rate of penetration.
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HDD
HDD is a method of trenchless pipeline laying which consists of drilling a pilot hole, followed by reaming and pipeline pulling (Fig.3). Usually drilling using HDD can be done in cold climates with temperatures down to -25°C
A construction of a 180 mm diameter HDPE pipeline 150 m long was undertaken under the river which divides the city apart. As while microtunneling operations, work place was tented and the heaters were installed. The upper layer of the ground composed of clay and silt was frozen to the depth of 2,3 meters. In spite of the upper layer of the ground being frozen, there was no need to use special hard face drill bits. Using aforementioned drill mud heaters, the temperature of the mixture was increased allowing to minimize the load on bit while drilling through frozen soil. Tenting preserved crew and equipment from negative temperature effects.
Figure 3 - Principal scheme of HDD
Several aspects of HDD in winter were noticed:
- low temperature made the upper layer of a swampy terrain frozen, thus assisting in delivering heavy machines and equipment on site;
- level of subsoil water is much deeper in winter;
- less interruption to everyday life is caused while HDD in winter;
- absence of heavy rains do not disturb working process;
- work site was remained much cleaner and less disturbed;
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HDD in winter, without proper selection of tools and preliminary work, can lead to severe accidents, crash of expensive equipment, or even abandoning the work /3/. Thus several precautions were taken into account:
- Warm water was used to prepare bentonite mud;
- Constant temperature control of the drill mud was done;
- Auxiliary mud heating equipment was used;
- Work site tented.
HDD unit was operating nonstop and decreasing the mud flow rate and ROP ifneeded.
Great attention was paid to improving working conditions for the crew, and limit workers exposure to negative temperatures. Worth mentioning is that only healthy crew can achieve a success.
Regardless the way you construct an underground pipeline in extreme cold. It should be remembered that material properties change in extreme cold. Thus PE pipe becomes stiffer in cold temperature which affects the tensile force and allowable bending radius, however the pressure rating stays the same.
LIST OF REFERENCES
1 Najafi, M. Trenchless Technology Piping. Installation and inspection. - McGraw Hill. 2010, 56566 p.
2 American Society of Civil Engineers (ASCE). Journal of Pipeline Systems Engineeringand Practice (JPS). http://www.editorialmanager.com/jrnpseng/.
3 American Society of Civil Engineers (2005). "Pipeline Design for Installation by Horizontal Directional Drilling," ASCE Manuals and Reports on Engineering Practice No. 108, Reston, Va.
LLP "Kazakhstan Scientific and technical center for HCS development", STE "Ertis". The material received on 21.09.12.
А.А. Абиров, Д.А. Егизбаев, В.С. Молчанов, Е.Б. Жаркенов, Б.У. Есенов, Ж.М. Омаров, К.Б. Сулейменов
Качакстаннын Астана каласында аса темен температура жаFдайында к^бырдыц тесемес1 аркылы орсыз технологияны колдану тэж1рибес1
А.А. Абиров, Д.А. Егизбаев, В.С. Молчанов, Е.Б. Жаркенов, Б.У. Есенов, Ж.М. Омаров, К.Б. Сулейменов
Практическое использование бестраншейных технологий при прокладке трубопроводов в условиях предельно низких температур в г. Астана, Казахстан
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0ркениеттiц вркендеу жагдайында курылыстыц барлык багыттарында инновациялык эдютермен технологияны ендiру щжеттт туындайды. Орсыз технологиялар курылыстыц «аспъщ» тэсШне жэне инженерлж жуйелер мен коммуницацияныц цайта жацгаруына тиiмдi альтернатива болып табылады.
Бiракl бул технологияларулкен жетютжтерге ие болгандыцтан, олардыц крлданылуы жогары дэрежелi каут щтердщ жагдайында мумкт емес.
Астана каласындагы суык экстремалды жагдайында орсыз технологиялардыц колдану тэжiрибесi кврсеткендей, мумкт болатын катердi сараптаудан жэне жумыс процесст жоспарлаудан кейт мундай жумыстарды катал климат жагдайында да жург1зуге болады.
В условиях стремительного развития цивилизации, особо остро встает вопрос о необходимости внедрения инновационных методов и технологий во всех направлениях строительства. Бестраншейные технологии представляют собой выгодную альтернативу традиционному «открытому» способу строительства и восстановления инженерных сетей и коммуникаций. Хотя данные технологии имеют многие преимущества, их использование может быть нецелесообразным в ситуациях с высокой степенью риска.
Опыт использования бестраншейных технологий в условиях экстремального холода г. Астаны показывает, что только после тщательного анализа возможный: рисков и надлежащего планирования рабочего процесса становится возможным вести работы даже в таких суровых условиях.
УДК 004.94
Б.Т. Абдрахманов
компьютерное моделирование в информатике
В этой статье автор дает справку компьютерному понятию модели на курсе информатики. Применять прикладные программы, говорится о компьютерных способах модели.
Компьютерное моделирование является, пожалуй, самым важным направлением курса информационных технологий. Процесс пректирования склада данных по сети вселенной постоянно происходит и абсолютно непрерывен. Ведь все существующие в природе явления, в какой - то мере зависимы друг от друга и имеют своё чисто математическое объяснение. Наглядную последовательность любых реальных событий можно проиллюстрировать с помощью каких-либо числовых последовательностей, функций одной или нескольких переменных, дифференциальных уравне-
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