FEATURES OF DRILLING-AND-BLASTING AT CONSTRUCTION OF BESKIDSKIY TUNNEL

*Dep. «Bridges and Tunnels», Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan, Lazaryan St., 2, Dnipro, Ukraine, 49010, tel. +38 (056) 373 15 53, e-mail 1937@gmail.com, ORCID 0000-0002-5902-6155 Dep. «Bridges and Tunnels», Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan, Lazaryan St., 2, Dnipro, Ukraine, 49010, tel. +38 (056) 373 15 53, e-mail tutkin@mail.ru, ORCID 0000-0003-4921-4758 Main engineer of State Enterprise «Zachiddorvybuchprom», Ternopil, 46006, Gayova St., 47, e-mail zvubyxprom@ukr.com


Introduction
In contemporary environment the construction of railway tunnels has found a widespread application in difficult engineering and geological condi-tions.The most significant example of this building is the construction of basic Gotthard tunnel in the Alps, length of 57.3 km, completion is scheduled for 2016 [3].A distinctive feature of tunneling driving of such a type is the extensive use of tunnel boring machines in hard and strongest rocks.
However, drilling and blasting method for breaking rocks in the tunneling driving including the workings of large section can be successfully used in such conditions [14][15][16].

Purpose
In Ukraine, currently tunneling driving of Beskydskiy double-track tunnel in the Carpathians is being completed.It is under construction in order to increase rail logistics between Western and Eastern Europe with using tunnel.Its length is 1850 m.Alternation of rocks of different types and strength, including sandstone, siltstone and mudstone with Protodyakonov scale of hardness respectively 6…8, 4…6 and 2…3 occurs in geological structure on construction sites.Hydrogeological conditions are characterized by the expected inflow of water in the range of 5…10 m 3 /day.Tunneling driving of double-track railway tunnel is carried out with the division of the face on calotte and stross with the way of lower ledge using drilling-and-blasting operations (DBO) [8] in to "bricked-up windows" with movement overlapping of trains in the Beskydskiy acting tunnel, located 30 meters away from the tunnel under construction.Moreover, the existing single-track tunnel was built in 1886.
Drilling operations are carried out when driving with the help of a self-propelled double beam electro-hydraulic unit "Sandvik DT 820-C" from Finland.At this the diameter of holes is 45 mm, and their length is 1.5; 2.3; 2.8 m when calotte driving and 4.2…4.5 m in stross development.Correspondingly stope length, depending on the engineering and geological conditions when calotte driving is 1.25, 2.0 and 2.5 m, and stross one -4.0…4.2 m.
Drilling of holes is produced by blowing with compressed air and water washing.Compressed air is supplied from the mobile compressor stations, located on near-entrance sites, and water via a pipeline that is laid as far as tunneling driving.
DBO nameplate is made at the stage of preproduction of works and refined accordingly to the results of at least three conducted test blastings [2,11].Breaking of rocks with blast-hole charges is provided to carry out using the method of successive contouring with mandatory application of de-lay-action and long-delay blasting of blast-hole charges groups in the following order depending on the stope size, mentioned above: coal-cutting, contour-hole, under contour, contour, plantar and under-bottom.Deceleration time (interval between multiple-shot blasting) taking into account rock hardness is from 20 to 10000 ms.
For blasting, the following blasting explosives are applied: ammonite № 6 ZhV -for dry and flooded holes, Grammonit 79.21 -for dry holes, ammonal M5 -for dry and flooded holes, gremixfor dry and flooded holes.At this cartridges of 28.32 and 36 mm are used [9].
At complex blasting operating two ways of charges blasting are applied: non-electric and electric [9,10].The non-electric initiation system (NIS) «Impulse» is used at non-electrical method.It includes the UNS-SH and UNS-ShK devices, detonating cord (DC), a main waveguide, connecting tube and the starting device.Unlike traditional methods of initiating explosive charges BB, this system has an increased level of security, since, due to insensitivity and stray currents it allows carrying out drilling works without de-energizing of power equipment.In electric mode NIS system «Impulse», UNS-SH device, UNS-ShK, DC and two detonators, type ED-1-3-T are also applied.

Methodology
One of the important issues of blasting operation is to ensure the seismic safety, acting at a distance of 30 m in the axes of single-track tunnel, as the distance to it will be 20 m from the nearest charge in the laying tunnel [1,4,6,7,13].
Seismic safety charge masses for complex engineering structures, like undoubtedly Beskydskiy tunnel is, can be calculated by the formula according to the work [5], . ., kg, where cr V -permissible critical velocity fluctuations, is determined from table 80 [5] and equal to 20 sm/s cr V = ; ε -coefficient depending on the conditions of work and the state of the engineering object is accepted within 1.5...3.0 ε = ; β -coefficient, which depends on the distance to the object, and equals to 1.5...2.0 β = ; Kg -coefficient depending on the geological and engineering condi- Consequently, there is a certain limit upon seismic at conducting of blasting operations with a maximum total charge BB on the stope when calotte driving of 163.5 kg.

Findings
Solving this problem was carried out by applying the combined blasting of blast-hole charges with delay-action and long-delay ways (Fig. 1).
At this the total mass of charges in the stope was divided into three groups, in which the first group is exploded by short-delay firing with slow intervals of 20…200 ms, and the second one is exploded by short-delay firing too with intervals of 200…400 ms, the third is exploded by long-delay blasting at intervals of 500…10000 ms.The total mass of blast-hole charges, length of 1.Thus, the maximum charges mass in groups are less than the maximum permissible under the terms of seismic safety.
As follows from the analysis of presented data in the first group of charges using short-delay blasting with intervals of 20…200 ms, wave interaction with the interference of longitudinal waves may occur.Charges blasting of the second group with an interval of 300…400 ms is performed after 100 and 200 ms.During this period a longitudinal wave from the charges blasting of the first group at its speed in rocks with a hardness coefficient 2...8 f = , equal to 2500…4000 m/s, will cover the distance from the blasting site of 250…400 m, namely the interaction of the waves and their interference are completely excluded.
Long-delay blasting of charges in the third group with intervals of 500…10000 ms will be performed with a significant margin in time and distance from the previous short-delay one.As a result the interaction of longitudinal waves in the subsequent blasting is completely excluded, which was confirmed by measuring the vibration velocity of rock in active tunnel, which were equal to 0.13…0.15m/s.Thus, the combined blasting of short-delay charges and delay action ones let significantly reduce seismic action at a mass explosion of charges when driving of double-track railway tunnel of a large cross-section.

Originality and practical value
The choice of a rational system of ventilation in face working is of great importance in these conditions.In accordance with current safety regulations [9] and classic work upon the tunnel ventilation [12] in workings, where people may be, the air must contain at least 20 % of oxygen (by volume) in its composition.Carbon dioxide content in the air of working at the places of operation should not exceed 0.5%, and in the working with a common upward current -0.75 %.In addition the air in active underground workings must be free of harmful substances exceeding the maximum permissible concentration (MPC), indicated in Table 1.
In accordance with the Safety specifications the amount of air required for working ventilation, should be calculated upon the largest number of people employed at the same time in underground works, quantity of harmful gases, calculated on a notional carbon monoxide in blasting operations, upon harmful gases from arc welding operations, as well as of harmful substances released during operation of machines and mechanisms with internal combustion engines.
The calculations showed that the maximum level of gas contamination of the working area in Beskidskiy tunnel is achieved at blasting operations, for which it is necessary to supply to the face of at least 165 m 3 /min of fresh air.
In accordance with this ventilation of the Beskidskiy tunnel when driving is carried out by independent systems with mechanical ventilation by blowing using mine the fans of "Donventilyator" enterprise.The main technical parameters of the fan are presented in Table 2.
Ventilation system operating principle is as follows.Airing face after blasting is carried out by air supply system from the Eastern portal with the help of an axial fan of the main airing, type IN-14-10D (Table 2) installed on near-entrance site.In the metal pipe with a diameter of 1600 mm made of sheet steel, thickness of 2 mm, fresh air is fed into the bottom-hole zone, which dilutes harmful gases and carries them over the working to the East portal.Along with plenum system also runs the local (near the face) exhaust system, which provides with CFT equipment (Kormann), dedusting exhaust air before its release to the general air flow that moves over the working from the face up to the portal.As advance of face the air supply pipeline, consisting of 4 m long pipes, is increased (built up) to provide effective ventilation.

Conclusions
Thus, the high-level scientific and technical preparation of operational materials upon technology penetration in the rocks in difficult engineering and geological conditions allows solving the problem of building the most complex railway artificial construction -Beskydskiy tunnel.

Fig. 1 .
Fig. 1. Circuit of the disposition and connection of explosive charges