Master's portal of DonNTU
At present, the structure of fossil fuel reserves in the world and in Ukraine is dominated by coal. Obviously, the economic development of our country largely depends on the energy sector in general and the coal industry in particular. Provided for the energy strategy of Ukraine activities for reconstruction of existing and construction of new coal mines are impossible without the construction of a large amount of capital mines, where a special place on the functional significance and technological specifics occupy vertical shafts for various purposes. From reliability stems largely depends on the rhythm and efficiency of the mines.
One of the most important tasks in the construction of trunks is increased efficiency, manufacturability and reliability of their attachment. In general, complex mining modern mine shafts have to share up to 30% of the cost and the cost of fixing at the sinking of shafts - up to 80% of their value. The analysis shows that increasing the thickness of the most common practice monolithic concrete lining of 10 cm leads to an increase in the cost of the trunk at 15%, while consumption of concrete - 30%. The use of other types of roof support, usually leads to even more significant increase in cost. In connection with the transition of mining in the Donets Basin to a depth of 1400 m, increasing the design load capacity roof supports a factor of 2, 1,5 ... 2,5 times increased the cost of materials lining and hard work of the fastening shafts. Despite this, currently lining half of the existing trunks requires urgent repairs.
Thus, today there is an urgent the need to find ways to improve the scientific and technical base of construction of vertical shafts in the direction of reducing the cost of material resources, foremost among which is the material lining. Thus, in this paper the relevant scientific and technical challenge.
Objective is to justify the effective parameters of monolithic concrete lining vertical shafts.
Objectives of research:
• conduct an analysis of the literature on the topic of this work;
• conduct laboratory experiments to establish relationships that characterize the influence prigruzok on the strength Hardening Concrete class B20, B25, B30 with additives to accelerate the setting;
• a computer simulation of the geomechanical processes in the vicinity of the bottom hole in the sinking of the barrel in various mining and geological conditions;
• Based on these studies to develop recommendations for optimal selection of the thickness of the concrete lining and the concrete class at the sinking of the stem in different geological conditions;
Possible scientific results work is to establish relationships that characterize the influence of rock pressure on the strength of Hardening Concrete class B20, B25, B30 with additives to accelerate the setting.
Possible practical results is to develop recommendations for optimal selection of the thickness of the concrete lining and the concrete class at the sinking of the stem in different geological conditions.
The issue of upgrading the technology facilities barrels in domestic and foreign mining literature has always been emphasized. The variety of ways to solve this problem completely reflected in the work carried out in the last ten years.
In this category only staff of the Department of school and PS DonNTU from 1999 to 2009. protected 2 PhD, 5 Ph.D. theses, holds two research.
One can identify the main directions (because of the very of a substantial number of publications on this topic provided links to abstracts of dissertations only):
• geomechanical framework development and selection of combined methods of fastening vertical shafts in structurally inhomogeneous rocks (Prof. V. Levit [1], 1999);
• physical-technical and organizational basis of intensive construction technology trunks in high water-bearing rock mass (Prof. SV Barshcheuski [2], 2008);
• support parameters of a combined technology (with wells) of vertical shafts (Prof. SV Barshcheuski [3], 2001);
• justification options anchor-concrete lining in the construction of interfaces vertical shafts of coal mines (Asst. Prof. AA Borodulya [5], 2002);
• improving drilling and blasting operations at the sinking of vertical shafts (Reader Kupenko IV [6], 2004, Assoc. Rublev OI [7], 2008);
• improvement in the technology facilities sprayed-concrete lining at the sinking of vertical shafts (Associate Professor Homenchuk OV [8], 2006).
Serious attention to this problem is traditionally paid staff Shi (f) SRSTU (NPI). There are the following ways of resolving the aforementioned problems (because of the very large number of publications on the subject give only link to abstracts of dissertations completed in recent years):
• improvement of design and technology facilities reinforcement shafts (FI Yagodkin, SG Stradanchenko, AJ Prokopov, MS Pleshko, MV Prokopova, R. Sahakian, A. Bogomazov and others [9-14]);
• improvement in the technology building vertical shafts through the study and selection of rational parameters of the parallel process flowsheet (JH Kokunko [15]);
• improvement of structures lining and fastening technology vertical shafts (FI Yagodkin, SP Syrkin, S. Maslennikov et al [9, 16, 17]).
Study of the geomechanical processes in the surrounding rocks barrel, the protection of the trunks, the justification of calculation methods of different types of lining the trunk dedicated to thousands of printed works employees IGTM NAS (VT Glushko, AF Bulat, BM Usachenko, V. V. Vinogradov, I. Vaganov, AN Zorin and others); VNIMI (GA Krupennikov, NS Bulychev, A. M. Kozel, VN Reva, AA Repko, etc.), NSU (AP Maximov, L. Ya Parczew, AN Shashenko, etc.), TSU (NS Bulychev, NN Fotieva, A. Sammal and etc.) and many others.
As can be seen even from this short review, a bibliography on the mounting shafts now has a huge number of works, due to urgency and complexity of the problem.
Next, we consider the current state of technology penetration and retention vertical shafts, used in domestic practice.
As is known, the sequence and the relationship of time and the space implementation of the basic processes that make up the tunneling cycle, and reinforcing the barrel is a flow chart of construction of the trunk. Classification of existing technological schemes tunneling [18-19] is shown in Fig. 1.
The main points describing technological schemes are given in Table. 1.
It should be noted that in recent years about 98% of all wells in our country took place in a combined scheme. Most likely, the scheme will remain the most frequently used in the next few years. Its main advantages: all the works are concentrated in the bottom of the barrel, which simplifies and enhances the security of work; trunk fixed nearly to the breast constantly strengthen, thus increasing the safety of works, no need to install temporary supports or shield-shell provides high mechanization of the main technological processes is simplified equipment slaughtering and surface, as well as reduced costs and time for equipment.
The most significant drawback of this scheme is that set of concrete strength is in complex geological conditions in the roadhead during the redistribution of rock pressure and intensified the displacement of rock walls.
Most currently, as a permanent roof supports used uses a monolithic concrete roof supports, the specific volume of which amounts to 90% of the total mount barrels.
The monolithic concrete lining has been used successfully for the retention of extended sections of tree trunks in the rocks of stable, high stability and unstable in the absence of effects of treatment works, adjacent developments and other factors.
The advantages of monolithic lining: the minimum number of seams; favorable conditions for ventilation (drag coefficient is 4 times smaller than the piece are fixed); a good relationship with the surrounding rocks, there is no need for construction support crowns on long sections of tree trunks; technological construction, high mechanization of tunneling works (up to 85% of all works mechanized); relatively low cost, use of local materials (sand, gravel), high durability and fire resistance. The most common concrete in domestic practice fixing barrel is a heavy concrete class B15.
One of the main deficiencies this lining is slow set of concrete strength. In practice, to accelerate setting and hardening process of concrete mixture, calcium chloride (SaSl2), less sodium sulfate (Na2SO4), calcium nitrate (Ca (NO3) 2? 4H2O).
As stated above, the cost of fixing at the sinking of shafts are quite substantial and can reach 80% of their value, increasing the thickness of the most common in practice, a monolithic concrete lining of 10 cm leads to an increase in the cost of the trunk at 15% and the flow of concrete - 30%. The use of other types of roof support, usually leads to even more significant increase in cost. Thus, reducing the thickness of the concrete lining can lead to very significantly reduce the construction cost of the trunk. This assumption for the conditions of penetration of several trunks of the Eastern Donbass confirmed in [16].
Thus, the use of concrete for fixing barrel higher than B15 brands can ceteris paribus reduce the cost of construction of the trunk.
Studies [20] found that the interaction of the system "concrete fix-breed" in time divided into two periods. The first is characterized by rapid growth of displacements of rocks and loads on the supports, the second - a relatively slow increase of displacements and loads. In this paper, the same [16] showed that when combined technological scheme of sinking the barrel, providing for the construction of the concrete lining after face advance, the process of concrete hardening is combined with the first period. In this case, the higher the rate of face advance of the barrel, the more intensive construction of rock pressure progressing concrete lining at an early age hardening. Under the influence of the stresses in the hardening material is the development of plastic deformation and creep, which do not destroy the design, to cut the ties and the formation of crystal dislocations, which reduces the ultimate strength of the Hardening of the material.
[16] was used to estimate the negative impact of mining pressure on the concrete (B15) is fixed at the early stages of hardening. This was tested samples from B15 at the age of 1, 3 and 7 days with prigruza 10, 30, 50, 70 and 90% of the strength of the specimen. Based on the data of the experiment were obtained depending on characterizing the change in strength properties of concrete B15 on the value of the additional load due to the passage of time.
Given this, it seems advisable to conduct additional series of experiments using concrete stamps B20, B25 and B30, and several types of setting accelerators, in accordance with GOST 10180-90 and GOST 24211-03 in order to obtain similar [16] relationships.
Using the results of these experiments will adequately define the physical and mechanical characteristics of hardening in the lining of the bottom hole for subsequent computer simulation of the geomechanical processes in the vicinity of the bottom hole of the trunk.
Results of laboratory experiments and computer simulations will formulate recommendations on the choice of optimal parameters of concrete lining (thickness and grade of concrete) at the sinking of the barrel in the given geological conditions.
An analysis of the literature identify the purpose and objectives of the master's thesis.
The dependencies characterizing the influence prigruzok Strength Hardening Concrete class B20, B25, B30 with additives to accelerate the setting;
Obtained depending on the results of computer simulation of the geomechanical processes in the vicinity of the bottom hole allowed to formulate recommendations for optimal selection of the thickness of the concrete lining and the concrete class at the sinking of the stem in different geological conditions.