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Reznichenko Aleksandr

Reznichenko Aleksandr

Faculty: Mining surveying

Speciality: Mining surveying


Theme of master's work:

Using of breakout shape of a hole to recover stress state in situ

Scientific adviser: professor, doc. teach. ski. Nazimko V. V.

About author

Summary on final work


Introduction

Mining in underground mining with the negative manifestations of rock pressure. These manifestations occur in such dangerous phenomena as sudden outbursts of coal, gas and rock, rock bursts, warping mines, collapsed roofs, etc.

The intensity of the manifestations depend on the magnitude of stresses in the rock mass and their orientation. At present, there are several different methods to assess stress-strain state of rock mass. However, all these methods are unreliable and do not provide satisfactory accuracy.

One of the promising methods of restoration of the field of strain and stress based on the study form the cross-section of wells and boreholes after their destruction under the action of these stresses. The reliability of the results of restoration of stress-strain state increases as a result of aggregation methods, such as experimental and calculated.

Improvement of this complex method is an urgent task. This area is part of a promising research area, for several decades developing in Donetsk National Technical University and the Department of Surveying.

Objective

Improved method for studying the stress of the array of rocks to improve the safety of underground mining.

Tasks of the research

1) an overview of the theory of elasticity and strength of the rocks;

2) development of a device for measuring the diameter of wells;

3) implementation of mine instrumental measurements and analysis of experimental results;

4) numerical simulation of the stress-strain state of rock massif around the hole and a study of its destruction;

5) of the integrated methodology for determining the parameters of rock pressure.

The idea

Based on the aggregation methods of field observations of deformation of the walls boreholes and wells with the method of numerical calculation of the form of destruction of these boreholes under the influence of rock pressure.

The object and subject of research

The object of research is the process of destruction under the action of the walls of the hole zamezhnih stress, the subject of research is the direction and magnitude of stresses.

Main content

The first part of my work dedicated to creating an instrument for measuring the internal diameter of the hole and determine the azimuth of the fracture. The destruction of wells is a consequence of normal stresses at the borehole wall.
The destruction of a well under normal stress

Fig.1 The destruction of a well under normal stress

To determine the location and nature of the devastation, I propose to use your device. The device is a four-hinged slats which are fixed at the ends of two tubes. Which are inserted one after another and move freely relative to each other. The basic principle of measurement is based in determining the direction of destruction and on his determination of the direction of the normal stresses.

Wellсaliper s

Fig. 2 Wells сaliper

To do this, using the device to find the zone with maximum destruction of the walls of the wells, sequentially measuring the diameter of the hole. And in a change in the diameter of the large side, to determine angle pair of levers on the azimuth. The measurements were carried out zones of influence and develop within a single layer of rock. Number of dimensions 5-10 wells at one site. The direction of the normal stress is perpendicular to the direction of destruction. The main problem is the problem of measuring differences in the destruction of the borehole walls all of erosion, the use of tunneling tools and mowing of rocks from destruction by the impact of rock pressure.

Main criteria for selection are:

1. One of the two measurements at the same depth should be close to the design diameter of the hole

2. The upper and lower part of the destruction should be clearly identified.

3. Diameter measurement should not exceed the diameter of the hole by more than 10%

4. The slope of the well should not exceed 10 °.

5. The length of the fracture zone should not exceed 1 m.

An example of the well without destruction

Fig. 3 An example of the well without destruction

Example wells destroyed under the influence of rock pressure

Fig. 4 Example wells destroyed under the influence of rock pressure


Example of borehole failure under washout

Fig. 5 Example of borehole failure under washout


Example wells destroyed by the impact of drilling tools

Fig. 6 Example wells destroyed by the impact of drilling tools


This method of determining the stress is widely used abroad, in particular 19% of the measured database of world tensions.

Second part of my work dedicated to the modeling of stress deformed condition of mountain. As the object of study is not used a large array of rocks (500-1000m.) With steeply dipping layers of different capacities and structures.

Fracture model well when the lateral load of 200MPa

Fig.7 Fracture model well when the lateral load of 200MPa


In geological history were formed about 20 tectonic processes. We simulate the stress-strain state of the array and observe the processes in the present tektonogeneze This work has been done for a better presentation of the formation mechanism of disturbances in the Earth's crust, uplift and subsidence of large areas of soil, mountain building, etc. And also for the study of processes occurring at the same time in the strata. To carry out planned work creates a digital model of the deposit. Getting to work, determined the size of the model, the well diameter and features an array

When creating a model for each stratum in the program impose the parameters:

• Poisson's ratio;

• Modulus of elasticity;

• Strength;

• The angle of internal friction;

• Angle fluidity;

• Density;

Boundary conditions by fixing realizes conventional boundaries, the creation of free boundaries, the application load on the individual border. In the present case is very important to simulate the tectonic stresses that easily allows finite element method.

Boundary conditions by fixing realized by conventional boundaries, the establishment of free boundaries, application of the load on individual boundaries. In this case, it is important to simulate the tectonic stresses that easily allows a finite element method.

The models reviewed.

The fracture model of well under lateral load. The number of frames, 8 frame delay 0,5 sec, repeat - permanently.

Fig.8 Fracture model well when the lateral load

Review of research on the topic in DonNTU

Mountain Institute of Donetsk National Technical University is one of the leading scientific organizations, which deals with geomechanical processes occurring in the coal containing the array as a result of underground mining. In surveying service coal companies responsible for the safe and efficient mining. The department Surveying in the study of stress state of a massif, its prediction and control of rock pressure in order to secure mining deal Ph.D. prof. Nazimko VV

Review of research on the topic in Ukraine

The territory of Ukraine research geomechanical processes taking place in the coal containing the array as a result of underground mining, are engaged in scientific research institute UkrNII National Academy of Sciences and Department of Physical and Technical Problems DonFTI NAS.

Main results

Be improved method for determining the orientation and magnitude of rock pressure component complex method

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