Available online at www.sciencedirect.com
ScienceDirect Procedia Engineering 165 (2016) 385 – 393
15th International scientific conference “Underground Urbanisation as a Prerequisite for Sustainable Development”
Some problems of buildings and structures service within permafrost area Vladimir Frolov a
a,
*
SC “Institute Giprostroymost Saint-Petersburg”, Russia
Abstract
Cryolithic zone occupies almost quarter of our planet area or 66% of the territory of Russian Federation. For our country longstanding permafrost is an essential factor of nature, economy and social sphere. Construction, deposit of commercial minerals within area of longstanding permafrost is very sophisticated activity for the following factors: availability of hazardous geological (geocryological) processes and occurrences - thermokarst, soilfluction, crack formation of soils and ettls, freeze over, knobs, stratificated missives, ice of repeated ice veins, thermal erosion, bogging of territories, cryopeg development and permafrost mound. Nowadays Extreme North is the biggest raw hydrocarbon deposit together with other treasures of the soil. Negligence of design specialties and construction within area of longstanding permafrost, lack of information regarding natural conditions of severe environment are the reason of man-made accidents with crucial effects to nature. Being conducted climatic change of our planet has negative influence on interaction of men with environment. Permafrost may form continuous, broken and island type features. Concerning temperature it may be classified as low temperature and high temperature permafrost soils. Very often permafrost has various grade of salinity with presence of salt brine which makes serious influence on soil features and interaction with buildings and other facilities under construction stage. To preserve permafrost basic characteristics systems of soil thermo stabilization are being applied (STS). The experience of Bovanenkovsky oil and gas condensate field showed that foundations are 42-60% of cost estimate and the share of STS considered from 5.8 up to 16.4% from construction expenses. During design stage of underground mine openings within permafrost conditions it is very important to be familiar with nature specialties for the reason to avoid man-made disasters as we had on minery Ihal. 2016Published The Authors. Published by Elsevier ©2016 © by Elsevier Ltd. This is an openLtd. access article under the CC BY-NC-ND license Peer-review under responsibility of the scientific committee of the 15th International scientific conference “Underground (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under theSustainable scientific committee of the 15th International scientific conference “Underground Urbanisation as a Urbanisation as aresponsibility Prerequisiteoffor Development. Prerequisite for Sustainable Development
* Corresponding author. Tel.: +7-812-233-96-66. E-mail address:
[email protected]
1877-7058 © 2016 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the 15th International scientific conference “Underground Urbanisation as a Prerequisite for Sustainable Development
doi:10.1016/j.proeng.2016.11.714
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Vladimir Frolov / Procedia Engineering 165 (2016) 385 – 393 Keywords: permafrost, cryolithic zone, thermokarst, soilfluction, bogging of territories, cryopeg, ice veins, thermal erosion, cryopeg development, minery.
1. Introduction The area of permafrost development (Criolithic zone) occupies almost quarter part of land surface of our planet (66% of Russian Federation). Criolithic zone includes entire European Northern Part, Central and Northern parts of Western Siberia, total territory of Eastern Siberia with Baikal Lake district, most part of Amur River area, Russian Far East, Northern Part of Kamchatka peninsula, Chukotka and Yakutia. Concerning geographical features Criolithic zone is divided as follows: on-shore subsurface plus sub-glacial permafrost and off-shore sub-shelf permafrost zones. On the above territories we have the most part of mineral resources of our Country including raw hydrocarbons (oil and gas). Permafrost may be presented as massive, scattered, massive-island and island allocation. The main features of permafrost formation are: genesis, extent in latitude direction, thickness of mass, cryogenic texture, state of solidly frozen, plastic frozen, loosely frozen, temperature of permafrost soils, ice content, availability of cryogenic processes and, dynamics processes. Development of permafrost soils within profile has heterogeneous structure and varies from the firs meters toward hundreds of meters. Permafrost may be classified on merge type and discrete type during summer period of time when thawed soils are being formed from not frozen layers at winter time. For our County permafrost condition is an important factor of nature, economy and social sphere. Service period of time for buildings and structures within permafrost conditions depends on various circumstances, but the keystone factor of life ability is a complex of civil-engineering survey. Design, construction, service of buildings, structures, management of structural foundations, and fulfillment of structural health monitoring are totally impossible without implementation of engineering survey. The importance of engineering survey efficiency is the keystone matter for Criolithic zone.[10, 11, 12]. 2. Problems of diamond fields development in Yakutia regarding kimberlite pipe Aihal Diamond fields locations were discovered in the beginning of 50-s of last century. Almost entire kimberlite pipes were developed via open method even with pit depth down from 320 to 500 meters and deeper. Open type method resulted negative outcomes such as: pit’s slopes demolition, gas burst, blow out of ground waters (salt brine), and necessity of pit area enlargement operation for the reason of big depths availability. From year 2000 development of mineral deposits was transformed to underground method. On diamond field minery Aihal the experiment site was arranged for underground method implementation. Total scope of work with the above method was accomplished on the depth of 320meters in 1997. Bottom level mark for South-Western lot was +235meters, for North-Eastern lot +195meters. 2.1. Geological and geothermic conditions Kimberlite pipe Aihal is located within permafrost masses. In accordance with geophysics survey area with bottom frontier of frozen rocks (icy rocks) is being located on the depth of 340-450meters. Ice-covered rock composition and kimberlite depends on cleavage with maximum values into zones of endo-contacts and exocontacts. Thickness of cryolithic zone is 720 meters with temperature gradient 0.8-1.2qС per each 100meters. Bottom layer of cryolithic zone is located on the level of -200meters with soil temperature based on temperature log within diamond drill-hole on depth of 260meters was –3.7qС; on the depth of 725meters +0.2qС; on the depth of 1000meters +3.6qС. In accordance with temperature log for drill-hole 21 (absolute depth mark +376): down to level of 260meters from –4.2 till –3.6; down to depth of 720meters gradually increased to 0qС. Pit reserves were presented by super cooled massive for the reason of low winter temperature influences, so for the purpose of actual temperature rage of underground massive detection, special research is required. On the territory of permafrost
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massive development including cryolite zone with thickness of 720meters. The lowest temperature range per the abovementioned mass were indicated near the upper surface -4.2qС , zero isotherm is placed on the depth of about 700meters (–200meters). The thickness of permafrost soil massive composed of 40-450meters (absolute depth mark+100 - +180m) which serves as a cover of upper Cambrian aquifer system [1, 2, 3, 7, 9]. 2.2. Geological conditions Area of diamond field deposit Aihal belongs to Tungussk cryo-artesian basin, composed of three types of underground waters: over-permafrost, inter-permafrost and under-permafrost. Over-permafrost waters does not influence on water content of mineral deposit. Important feature of underground waters is availability of dissolved gas, mostly hydrocarbon composition such as methane and butane with high level of mineralization up to 300347gram per liter. For the reason of miscommunication of different companies being involved in ware removing, part of waters were dumped on the bottom of pit, so by July 2003 there were level of two and half million cubic tons of pulp with particles in suspension of kimberlite and massive materials. 2.3. Mountain scope of works During emergency situation origin, underground work performance was conducted within both ore bodies of the Aihal located between markings +205 and –100meters (South-Western ore body) as well as +125 and –100meters (North-Eastern ore body). Parallel work performance was aimed on vertical supports concreting with initial pits preparation on the depth of more than 150meters. Ceiling of mine was not properly fixed which resulted water and pulp burst from the bottom of the pit. The outcome of that accident was closure of mining field Aihal for the period of two and half years. Mining Institute of Novosibirks being collaborated with Northern Mining Institute from Yakutsk regarding research of rock mass temperature range during work performance of mining field Aihal, received the data concerning sophisticated interaction of permafrost masses. Fulfillment of visual and instrumental engineering measurements on Aihal Minery, resulted the statement of negative self-inflicted outcome on permafrost nature. Intensive mining performance drastically altered not only the uniformity of permafrost masses but as well as on natural physical conditions of masses (cleavage, penetrating, heat transfer etc.) plus geothermal field for the reason of progressive ventilation rate with intensive and altered heat rate accumulation.
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Fig 1. Seasonal air temperature variation on Aihal Minery.
Heat interchange within masses of minery has complicated and variable nature such as: periodical (cyclical), those which annually increases sub-thermal, geo-thermal, hydrogenous negative physical and chemical effects, such as, for instance, weathering especially within air ducts of minery, which causes reliability features deterioration, icing of rock masses plus complexity of work performance, which were proved several times by survey results. Based on radical influence of thermal condition on safety and work production effectiveness on minery, attention was focused on detailed features of such factor. 2.4. General research summary concerning dynamic of temperature range of minery The most lowest temperatures during winter time period were indicated within mouth of air ducts -40qС, with gradual temperature increase following the duct flow up to -18qС. Consequently in summer time (Julu, August) peaks of ventilation flow were from +5qС up to +15qС. Air relative humidity in winter time was not higher than 50% with sublimation effect presented. During summer season the highest values of relative humidity were observed and sometimes it was 100%, within minery in the event of active penetration of upper ground waters. Contact layer temperature was about from +3 up to +9qС in summer and in winter from -11 up to -1.5qС within two meters depth with annual variations from -7qС up to +4.7qС. The start of mass thawing period was indicated by all control stations by the end of May and consequently freezing period starts from the middle of September. Interesting event was noticed at summer time of survey fulfillment at one of control stations – positive mass temperature on the depth of 3meters! The above may be subjection of intensive temperature interchange within mine field deposit at summer period of time [3, 13].
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Fig. 2. Diagram of rock mass temperature variation per depth, month and control stations.
Based on intensive work activity aimed on diamond deposits together with clean out jobs in mines including new production methods research actions should be continued. According to world experience in the field of tunnels construction, attention should be paid to survey works focused on water bearing formations forecast regarding filtration and deformation actions possibility. Geological targeting should be more focused on hydrodynamic pressure stability for masses within zone of rock fracture as well as washout of joining material from fractures, dispersive masses transformation in movable condition shall be the matter of monitoring to ensure designated tunnels safety and reliability Features of Cryolithic zone such as: temperature range of permafrost masses, variations of permafrost temperature range during job performance, alteration of soil layers features during industrial activity, unfortunately, very often were not the matter of designer’s attention. For the reason of transportation network development together with mining fields enlargement tendency within Cryolithic zone of Northern territories of Russian Federation more survey and research action (engineering protection) are essential in the above sphere. Total mentioned factors apparently shall increase the costs of design works, construction and service. 2.5. Problems concertizing construction oil and gas complex with mainland pipelines within Cryolithic zone Areas of Cryolithic zone development is an important and sophisticated task as well as underground mining arrangement procedure. Intensive need of mineral resources, mining as well as hydrocarbon materials necessity resulted requirements of construction of huge industrial complexes on territories of complicated engineering, geological and geo –cryological severe conditions. Civil engineering, industrial construction, highways and rail roads development, mineral resources mining grows in rigorous Northern territories are very complicated concerning arrangement of infrastructure net within mining of mineral resources. Expenses analysis regarding development of Bovanenkovskiy oil/gas-condensate field (based on collaborated researchers of “VNIPIgazdobicha”) showed 75% of total costs belong to foundations and thermo stabilization arrangement.[10, 11, 12]
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Fig 3. Expenses analysis regarding development of Bovanenkovskiy oil/gas-condensate field: ОФ-foundations; ТСГ thermo stabilization of soils; АС-per building structure; ГТМ-per the net of geotechnical monitoring system.
Number of industrial disasters and incidents within Cryolithic zone is dramatically raised for the reason of manmade nature disturbance. Natural gas production losses are down to 29 % for the reason Cryolithic zone disorder.
Fig. 4. Gas production in Russia and failures of geotechnical system for the reason of Criolithic zone disturbance.
In the event of temperature rate violation, general negative processes are as follows: permafrost disorder within building foundation because of soil feature alteration based on excessive accumulation of snow masses around the structure, formation of seasonal soil expansion in foundation body, thermokarst and piles body deterioration. In case of linear structure, development of the abovementioned troubles expansion are more rapid, which is really an obstacle for construction and services of pipe lines, highways, power transmission lines especially in intersection areas of rivers, mountains and hills.
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Fig. 5. Geotechnical problems regarding service of linear structures: pipeline damage caused by thermokast; bogging formation; rail roads swell and marl weathering.
Air temperature plus soil masses monitoring are the essential part of the scope of works relating development of Cryolithic zone. Long term statistics highlighted air temperature climb started from 2001. Soils temperature varies as well together with air conditions alternation but with long time delay.
Fig. 6. Results of drill-holes temperature logging.
To ensure safe and stable service of buildings, structures and linear facilities various systems of vertical and horizontal thermo stabilization are being implemented. Without those systems application, mining development within Northern and mountain territories is absolutely impossible. Combined vertical and horizontal thermo stabilization performance is being implemented within sophisticated structures (for example, thermo stabilization systems of enterprises like “Fundamentstroyarkos Ltd” and JSC “Fundamentproject”. For the purposes of soils thermo stabilization actions on linear facilities, passive systems are being applied at winter time only. Those systems
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are very popular in areas of low winter temperatures like Yakutia, Taimyr and Yanao. In this sphere the experience of our Chinese colleagues is very impressive regarding construction of rail roads in highland areas of Tibet. In case of permafrost temperature rate conservation is counter-productive for the building foundation, application of artificial defrosting systems shall be implemented for safe and reliable foundation functioning.
Fig. 7. Vapor- liquid system of thermo stabilization at Gazprom site in Nadym.
Liquid Natural Gas terminal systems allows to fulfill reliable forecast of soil fields temperatures variations (even for conditions of climatic temperature alternations) [12].
Fig. 8. Forecast results regarding formation of temperature field per permafrost soils of workshop equipped with thermo stabilization system. Event trend concerning annual average air temperature raise as follows: +0.004°/year.
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Based on the above said the conclusion is as follows: the development of permafrost masses of Cryolithic zone makes construction performance with services of buildings and structures very complicated and expensive as well. In this event, for the improvement of Northern territories development more intensive study of engineering – geological characteristics is essential together with permanent environment monitoring to overcome the challenge we have. References [1] V.I. Ustinov et al, Study of structural-tectonic and geochemical features of the diamond mine fields areas “Aikhal” and “Udachnaya”, Report of fulfilled industrial works per 1980-1982, Funds of Amakinsk Geological Research Expedition, 1984. [2] A.S. Gladkov, K.Zh. Seminskiy, O.V. Lunina et al., Study of fracture segmental features of the diamond mine field “Aikhal” and “Yubileynaya”, 2002. [3] B.A. Kartozia, Construction of mountain mines within hard mine technical conditions. Manual, Nedra, Moscow 1992. [4] V.N. Skuba, Improvement of development of Northern mine fields, Mining Institute of North, Yakutsk, 1986. [5] V.A.Sherstov. Analysis, estimation and technical level indices forecast per underground development of permafrost deposits, Mining Institute of North, Yakutsk, 1991. [6] V.S. Popov, V.G. Grinev. Construction technology of underground kimberlite tubes, Mining Institute of North, Yakutsk, 1997. [7] V.U. Izakson et al, Reliability questions regarding open permafrost deposits, “Nauka”, Novosibirsk, 1995. [8] A.A. Kozeev, V.U. Izakson, N.K. Zvonarev, Thermo and geo mechanics of the diamond mine fields, “Nauka”, Novosibirsk, 1995. [9] D. S. Drozdov, V. A. Dubrovin. Arctic Oil and Gas Exploration and Environmental Aspects of the Mining Industry Development in Arctic. [10] D. S. Drozdov, Informational mapping modeling of environmental techno genetic conditions within geo cryology, Abstract of thesis for academic degree of Doctor of Geological and Mineralogical Science, Tyumen, 2004. [11] D. S. Drozdov, G.V. Malkova, N.G. Ukraintseva, U.V.Korostelev. Monitoring of geo cryology environment of Southern landscapes of European North with Western Siberia. Reports of Tenth International Conference of permafrost (TICOP), Resources and risks of permafrost within changing environment. 3 (2012) 159-164. [12] V.A. Dubrovin, L.N. Kritsuk. Problems of geo cryology research in areas of Arctic and Sub Arctic, Exploration and preservation of underground resources. 8 (2014). [13] V.S. Popov, V.G. Grinev. Temperature range during development of diamond deposits of Alrosa Company. “Aikhal”, Report of 2000-2003, Mining Institute of North, Yakutsk, 2004.
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