1545 Journal of Engineering Geology, Vol.6, No.2, Autumn 2012 & Winter 2013

Evaluation of rockburst potential in second part of Karaj-Tehran water conveyance tunnel

*Gh. Khanlari, R. Ghaderi Meybodi:
Department of Geology, Bu-Ali Sina University, Hamedan,
Received: 18 Jan 2010 Revised 2 Jan 2011
Abstract
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One of the geotechnical hazards in the tunnels under high overburden and high in situ stresses is the phenomenon of rock burst. Rock burst is a typical geologic phenomenon caused by excavation in rock masses. In this phenomenon, because of stress released and explosion in rock masses, they are broken as large and small pieces and are distributed, so that leads to damage of peoples or equipments. Therefore, familiar with this phenomenon and its mechanism of occurrence, is need to analyze this issue. The second part of water supply Karaj-Tehran tunnel with a length of 14 km and about 4.5 m diameter is located in Tehran province. Rock burst analysis has been carried out in the tunnel from kilometer 6 to 9.5 that is critical section because of high overburden (up to 800 m) and presence of faults and crushed zones. In this paper, for predicting rock burst in the critical section of second part of Karaj-Tehran tunnel, four criteria including, Strain energy, Rock brittleness, Seismic energy and Tangential stress criterion are used. Analysis results show that units with high overburden have high possibility of rock burst.
KeyWords: Geotechnical Hazards, Tunnel, Rockburst, Predict.
-4419577

*Corresponding author [email protected]
Introduction
When an excavation for a deep underground tunnel or chamber is undertaken in a strong and brittle rock, the change in stress results in dynamic damage to the adjacent rock, referred to as rockburst or break ways. Such rockbursts are a major hazard for the safety of engineers and engineering equipment as well as affecting the shape/size of the structure (Jiang et al. 2010).
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The first recorded rockburst was in a British coal mine at Stafford in 1938(Jiang et al. 2010). Since that time there have been a number of reports of rock burst from all over the world. In recent years the importance of this geological hazard has become appreciated in infrastructure such as tunnelling and mining. Consequently rock burst has attracted a high degree of attention in engineering geology and rock mechanics. Cook et al. (1966), through experimental work, provided a theoretical method of predicting rockburst based on the opinion that violent damage of rock occurs when an excess of energy becomes available during the post peak deformation stage. Brady and Leighton (1977) recorded a seismicity phenomenon before a moderate rock burst while Heunis (1980) introduced control strategies with regard to rockbursts in South African gold mines.
Rock burst analysis has been carried out in critical section of second part of Karaj-Tehran tunnel because of high overburden and presence of brittle rock in tunnel route.

Study area characteristics
The second part of water supply Karaj-Tehran tunnel with a length of 14 km and about 4.5 m diameter is located in Tehran province which is located in the north of Iran (Fig.1).
This tunnel is a part of water supply plan for the purpose of drinking water for Tehran. This tunnel is started from Amir Kabir Karaj dam and will continued to water softening (No: 6) of Tehran.
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Fig.
1
Location

of study area in Iran

Fig.

1

Location

of study area in Iran

Rock burst analysis has been done in the tunnel from kilometer 6 to 9.5 as critical section because of high overburden (up to 800 m) and the presence of faults and crushed zones (Fig.2). Engineering geological units in this section are formed with specific signs that are the initial letters of lithology of units.
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Fig.
2
Critical section of Karaj

Tehran tunnel route



قیمت: تومان

دسته بندی : زمین شناسی

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