Mining Institute of Kola Scientific Center of Russian Academy of Sciences, Apatity, Russia:

Abramov N. N., Senior Researcher, e-mail: abramov@goi.kolask.net.ru

Epimakhov Yu. A., Head of Laboratory, Doctor of Engineering Sciences

Kabeev E. V., Leading Technologist

Federal State Unitary Enterprise Construction Department No. 30, Mezhgorye, Bashkortostan Russia:

Kostenko V. V., Chief Engineer

The quality control of holding the large span mine working in severe geological conditions is an actual technological issue. Due to the accumulated experience of Russian and foreign construction works, this problem solving is closely connected with usage results of rock massif state monitoring during the driving operations. Realization of the proposed approach is demonstrated by the example of construction of Yuksporsky tunnel of “Apatit” JSC.

Geological driving conditions are characterized by ijolites and urtites and are complicated by separate areas with oxidized rocks with 6 – 18 meters thickness. Watering is slight and seasonal. Stress state of rock mass before driving is defined by presence of vertical (gravitational) and horizontal (tectonic) components.

The driving conditions are classified as prone to rockburst. The following activities are accepted as the methods of rock massif geomechanics monitoring, based on monitoring tasks and driving conditions:

-performance control of deformations on the structural rock massif break, while crossing the tunnel track;

-statistical analysis of magnitudes of out-contour rock overbreaks in tunnel’s sections, which are relative to the project contour on each drilling run and assessment of parameters of the disturbed area from the contour rock massif.

It was proposed to assess a stability of outcrops as a face advanced and quality of drilling-and-blasting breakage on three-level scale, using the performance control of deformations on the structural rock massif, while crossing the tunnel track, along with a statistical analysis of magnitudes of out-contour rock overbreaks in tunnel’s sections, which are relative to the project contour on each drilling run and determining parameters of disturbed area from the contour rock massif.

According to the results of the carried out analysis of blasting-and-drilling operations quality by magnitudes of out-contour overbreaks, it was established that driving was performed with an "excellent” grade for 62% of the tunnel’s track, with a “good” grade for 24% of the tunnel’s track, and a “satisfactory” grade for 14% of the tunnel’s track. Thus, the geomechanics monitoring of rock massif state, which has been organized during the Yuksporsky tunnel driving operations, permits to solve a complex of technological issues which increases safety and efficiency of a tunnel’s driving.

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