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Sergey Stelmakh

Sergey Stelmakh 

Faculty: Mining and Geological

Speciality: Mining surveying

Stress-strain state of rock mass around a roadway having irregular shape of the face

Scientific adviser: Full Doctor, Professor Victor Nazimko 


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Summary of research and developments


Contents

  1. Introduction
  2. Relationship of the Master’s Work with Scientific Programs, Plans, the Fulfillment of the Work According to the Scientific Institution or Industrial Organizations
  3. Purpose of the Work
  4. The Problems of the Research
  5. The Idea of the Work
  6. The Object and Subject of Research
  7. Possible Results Expected During the Work, Their Novelty and Importance
  8. Planned Evaluation of the Results
  9. Summary
  10. Conclusion
  11. Sources

Introduction

At present coal is the only source of energetic independence of Ukraine. The development of Coal industry defines the energetic independence. Coal is extracted in many mines at a great depth. As a result there are abutment zones which cause the reduction of mining safety and serious catastrophes. To avoid this scientists all over the world deal with stress-strain state of rock mass studying.
The standard stress assessment method in rock mass is “overcoring” one [1]. However it is not reliable enough due to small gauge length. The urgency of the new method introduced at the Mining surveying department is that stress “load relief” is fulfilled on great strain gauge length in a tunneling face or longwall face directly. With the help of numerical methods it is possible to restore the initial stress state of rock mass. After this one can measure the strain “load relief”. At the same time the algorithm of stress recovering becomes complicated and requires developing of more advanced models. It gives the possibility to apply these models at numerous measurements.

Relationship of the Master’s Work with Scientific Programs, Plans, the Fulfillment of the Work According to the Scientific Institution or Industrial Organizations

Mining surveying department has dealt with problems of mining pressure in the conditions of the great stress-strain state of rock mass level for a few of decades.

Purpose of the Work

To improve mining safety at the expense of reliability of stress-strain state of rock mass obtaining advancement.

The Problems of the Research

  1. To study strain and strength properties of rock in the model and mass;
  2. The bases of design and modeling physical and computer methods of stress-strain state of rock mass;
  3. ANSYS [2] program studying;
  4. Structural model preparing, boundary conditions and initial state of modeled system validation;
  5. Stress-strain state for different variants analysis of boundary conditions with the purpose of stress recovering operating in rock mass;
  6. Correction and analysis of calculation results.

The Idea of the Work

Stress recovering in rock mass on its strains measured on the surface of the face having irregular shape.

The Object and Subject of Research

The object of the research is the process of stress redistribution in rock mass [3]. The subject of research is the stress recovering procedure in rock mass on its strains measured on the surface of the face having irregular shape.

Possible Results Expected During the Work, Their Novelty and Importance

After the researches a new stress recovering procedure in rock mass on its strains was developed. The novelty is strain measuring on the surface of the face having irregular shape and great area. The importance of the work is in increase of reliability of stress-strain state of rock mass recovering. It is possible at the expense of the improvement of strain measuring accuracy. The mining safety is increased as a consequence of more accurate analysis of stress in rock mass.

Planned Evaluation of the Results

The report at the conference of young scientists, applying the work for the contest, publication of the article in the professional scientific collection.

Summary

Stress recovering procedure is released with the help of modified load relief method at the tunneling face or longwall face by anchoring several monuments (see Figure 1).
Two monuments
Figure 1 – Two monuments.

The distance between them is accurately measured with special mining surveying tools. After the first measurement for the initial distance determination between reinforcing bars one should make an advance. It is made on one half of the face area. For this purpose a tunneling machine makes coal extraction at the depth of 1 meter. As a result there is load relief of the rest of the face. The rest of the rock extends towards roadway entry space. The rock expansion is accurately measured with the same special mining surveying tools and strain is calculated.
The second stage of component strain recovering is released with the help numerical methods of the stress-strain state of rock mass analysis.
Structural model
Figure 2 – Structural model.

Figure 2 shows the structural model. Structural model bounds are spaced far enough from the roadway entry face to avoid great disturbance of stress-strain state of rock mass around the face. Practically it is attained because the distance from the face to structural model bounds proportioned to be 3 or 4 times oversize of tunneling roadway entry. The bottom side of structural area and wall sides are spaced in 2 or 3 diameters from the roadway entry. The top side is spaced at the distance of 3 or 5 diameters of the roadway entry.
Normal components of displacements are prohibited on three sides (two wall sides and a bottom one of the structural model). See Figure 2. On the rest three sides one can give components of required stress. The top side of the model is free. The weight of the upper bulk is replaced with stress on the top bound of the model or displacements on the top edge. Vertical component is taken as a geostatic level of mining pressure at the depth of roadway entry placement. The side components of stress are selected to make calculated strain on the plane of face equal to measured one in the mine.
The search process of horizontal stress component quantities is released with iteration method [8] founded on the research algorithm of minimum or maximum of the function [9]. In this case the search of minimum of angular and linear deviations of calculated strain from measured one will be released. The adaptation of gradient, the fastest descent or artificial intelligence methods [10] is allowed in this work.
Figure 3 shows the search process of ratio and quantities of horizontal stress components. On this figure the deviation to direction and on calculated strain quantity from measured one reduces on the next step of search.
The search of ratio and quantities of horizontal stress components
Figure 3 – The search of ratio and quantities of horizontal stress components.
Animation was created with Zoner Gif Animator 5. 6 stills with delay 1 second. Loop 6 times.

Conclusions

This stress recovering method has great applied significance as the reliable evaluation of stress components allows forecasting negative manifestations of mining pressure in particular coal and gas outburst, mining bumps and other dangerous phenomena. While using this method it is possible to improve the reliability of forecasting dangerous zones on negative manifestations of mining pressure. It can increase mining safety and lead to reduction of workers injuries and deaths.

At the moment, Master's work is in progress. After the December 2011 full text paper can be obtained from the author or supervisor.

Sourses

  1. Проектирование и строительство городских тоннелей / [Электронный ресурс] - http://www.citytunnel.ru/naturnye_eksperimentalmznye_issledovaniya.html
  2. Материал из Википедии — свободной энциклопедии / [Электронный ресурс] - http://ru.wikipedia.org/wiki/ANSYS
  3. Борисов А.А. Механика горных пород и массивов. М.: Недра, 1980. - 360 с.
  4. Мухин Александр, Блинов Олег. Что такое конечный элемент / [Электронный ресурс] - http://www.ispa-soft.ru/statxi/statxq2.htm
  5. Урев М. В. Сходимость метода конечных элементов для осесимметричной задачи магнитостатики. Сибирский журнал вычислительной математики, 2006. - 63–79 с.
  6. Розин Л. А. Метод конечных элементов / [Электронный ресурс] - http://www.fea.ru/docs/FEM/Rozin.pdf
  7. Зенкевич О. Метод конечных элементов в технике. Пер. с англ. — М.: Мир, 1975. - 543 с.
  8. Итерационные методы решения систем линейных алгебраических уравнений / [Электронный ресурс] - http://www.nsu.ru/education/cmet/node33.html
  9. Трифонов А.Г. Постановка задачи оптимизации и численные методы ее решения / [Электронный ресурс] - http://matlab.exponenta.ru/optimiz/book_2/2_1.php
  10. Исаев Сергей. Популярно о генетических алгоритмах / [Электронный ресурс] - http://algolist.manual.ru/ai/ga/ga1.php

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