With the increasing automation of mining, the underground mining forecourt mining is becoming increasingly important. In order to determine the tectonic content of the apron, a weather-protected measuring system was developed, which detects the position of disturbances by seismic channel waves.
There are two methods for mapping:
1. The Through-Transmission Measurement provides information about a fault in the seam
2. The reflection measurement provides information about the situation.
A great sense of accuracy can be achieved with combined use of both methods. The analysis of 111 measurements shows that geological conditions made the accuracy of the measurements very good, while in geologically complex structures the location of the disturbance proved to be very difficult.
The loss of resolution associated with envelope formation prevents the detection of clutter. To remedy this situation, the reflected Flözwellenzug must be attributed to a needle pulse. Theoretical investigations confirm this approach.
Since flute waves are subject to absorption - the higher the frequency, the stronger the absorption - and the loss of energy in reflection occurs, research in this area still needs to be done in order to use the insights gained in data processing. Remedies cause a spatial distribution of energy and thus complicate the indication of a possible disorder. This shows that complex geological structures have to be further investigated by model seismic investigations. This requirement is underlined by the high costs of underground measurement, which depending on the length of the track to be measured amount to 50,000 DM to 150,000 DM
Table of Contents
1 Introduction
2 Theoretical Basics
3 Measuring Principles
3.1 Reflection Measurements
3.2 Through-transmission Measurements
4 Measuring Equipment And Implementation Of Measurements
5 Susceptibility To Interference Of The Measuring-System
5.1 In The Apparatus
5.2 In The Measuring-System
6 Measurement Results In The Acquisition Of Disturbances And Measurements With Special Objective
7 Evaluation Of Measurement Results
8 Future Development
9 Summary
10 Bibliography
Research Objectives and Themes
This work explores the use of seismic measurements within seams as a geophysical method to detect geological disturbances, which pose significant financial and operational risks in mining. The research aims to evaluate the accuracy and reliability of these seismic techniques in predicting underground conditions to optimize extraction processes and prevent costly production stoppages.
- The importance of detecting geological faults for mining efficiency.
- Theoretical fundamentals of seam-wave propagation and dispersion.
- Application of reflection and through-transmission measurement methods.
- Technical implementation and equipment requirements for digital seismic data acquisition.
- Statistical assessment of measurement success rates in various geological conditions.
Excerpt from the Book
3. Measuring Principles
To explore the apron by seam-waves two methods are available. The reflection measurement makes it possible to detect tectonic disturbances locally. The measurement of the sound transmission provides data for the determination of interference contributions in comparison to the seam thickness, which means crosstalk disturbances are detected. For the accuracy, it proves useful to apply both procedures in parallel.
3.1 Reflection Measurements
An explosion at a depth of about 2 meters causes an energetic stimulus, which causes waves to fan out. These are reflected according to the laws of optics, when they encounter a problem, because behind the seam transfer are other physical constants exist as before. The geophone introduced in the seam pick up the reflected waves and pass analogue voltage signals to a recording device, where they are recorded in the form of seismograms, as shown in Figure 4.
Summary of Chapters
1 Introduction: Discusses the economic impact of geological disturbances in the coal industry and establishes the need for reliable underground seismic forecasting.
2 Theoretical Basics: Explains the physics of seam waves, the role of density contrast, and the phenomenon of dispersion in seismic channel waves.
3 Measuring Principles: Details the two primary geophysical approaches: reflection measurements for local fault detection and through-transmission measurements for monitoring channel continuity.
4 Measuring Equipment And Implementation Of Measurements: Describes the development of impact-resistant digital acquisition systems and the practical challenges of deploying geophones and explosive charges underground.
5 Susceptibility To Interference Of The Measuring-System: Analyzes technical failure points in the electronic apparatus and environmental obstacles affecting the vibration sensors.
6 Measurement Results In The Acquisition Of Disturbances And Measurements With Special Objective: Presents the application of the system in varying geological environments, from simple tectonic jumps to complex structural interferences.
7 Evaluation Of Measurement Results: Provides a summary assessment of the system's current capability to locate disturbances depending on tectonic complexity.
8 Future Development: Addresses the need for improved resolution through needle pulse attribution and ongoing research into managing wave energy absorption.
9 Summary: Concludes the findings, emphasizing the high accuracy of the combined seismic methods for standard geological structures.
10 Bibliography: Provides a list of cited literature and research reports used to support the technical findings.
Keywords
Seam waves, seismic measurements, mining, geophysical tools, geological disturbances, reflection seismics, through-transmission, coal industry, Airy phase, dispersion, data acquisition, tectonic structures, geophones, digital measurement, fault detection.
Frequently Asked Questions
What is the core focus of this research?
The work focuses on using seismic measurements within coal seams as a tool to map geological disturbances, which are crucial for maintaining continuous and safe mining operations.
What are the primary themes addressed?
The main themes include the physics of seam-waves, specific methodologies for seismic exploration (reflection and transmission), and the practical implementation of digital data collection under harsh underground conditions.
What is the main goal of this study?
The goal is to establish a reliable geophysical forecasting method that can accurately detect tectonic faults to minimize the high financial risks associated with interrupted mining production.
Which scientific methods are employed?
The study utilizes seismic channel wave theory and compares two specific techniques: reflection measurements for localized faulting and sound transmission measurements for assessing seam homogeneity.
What is covered in the main body of the text?
The main body details the theoretical wave physics, the hardware requirements for digital recording systems, the susceptibility of this equipment to interference, and an analysis of performance across different tectonic scenarios.
Which keywords characterize this work?
Key terms include seam waves, seismic measurement, coal mining, fault detection, Airy phase, and tectonic disturbances.
How do reflection measurements work for fault detection?
Reflection measurements involve initiating a seismic shock and recording reflected waves at geophones; if waves encounter a physical discontinuity (a fault), they are reflected back, indicating the location of the disturbance.
What is the function of the "Airy phase"?
The Airy phase is a specific, high-frequency component of seam waves that remains bound to the seam, making it an ideal "useful signal" for seismic analysis while filtering out background noise.
Why is digital equipment susceptible to failure?
The digital apparatus is exposed to heavy vibrations and transport shocks in mining environments, which can dislodge internal electronic components or cause physical fractures in the circuitry.
How does the seam act as a waveguide?
Due to the density contrast between coal and surrounding rock, seismic waves are trapped within the coal seam, effectively guiding the energy and allowing for long-distance measurements.
- Quote paper
- Dipl.-Ing. Dieter Wessels (Author), 1990, Seismic Measurements Of Waves In Seams As A Geophysical Tool In The Extraction Of Raw Materials, Munich, GRIN Verlag, https://www.grin.com/document/432632
