Mine Seismology: Seismic Response to the Caving Process

A Case Study from Four Mines

verfasst von: Dr. S.N. Glazer

Verlag: Springer International Publishing

Enthalten in: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik" , Springer Professional "Wirtschaft"

Einloggen, um Zugang zu erhalten

Über dieses Buch

This book presents the results of seismic data analysis and interpretation based on nearly one million seismic events. This seismicity was induced by the caving process in four copper mines, each located on a different continent. The book not only serves as an interpretation guide, it also illustrates the benefits of evaluating data from different mines:How to establish which seismic data base is faulty and why

The formation of a universal seismic response to the caving process

Indisputable evidence that hydro-fracturing improves underground safety  

This book invites discussion on more general aspects of research, such as:

Basic research, applied research and implementation

Predicting mine-induced seismic events

Quantitative versus qualitative seismology

Research versus pseudo-research

What is genuine research?

[In the Parlabora Mine] Stefan has demonstrated that [the] use of the seismic system was a very practical means of monitoring the progression of the cave up to and beyond break through into the open pit above. The seismic system was vital in drawing up the undercutting and seismic protocols and determining the maximum potential seismic hazard level. Peter Townsend Retired Mine Manager and Consultant

I consider Stefan the pioneer of using microseismic data to provide understanding of the mechanism and progress of cave mining. Science has advanced considerably since the use of less than reliable extensometers to monitor the cave back position and Stefan was leading this advance. (…)This book provides a lot of useful insight[s] in how we can best understand the data that we (…) gather and how to change this data into useful information. Neil Hepworth C. Eng, MIMMM, Geomin Consultorio – Brazil. Consultant Mining and Geotechnics

Stefan mine seismology trilogy is (…) a comprehensive tutoring on how to analyse and interpret mine induced seismicity. This coaching is based on multiple practical examples (…) presented from the problem to be solved [with] input data tests followed by analysis and interpretation. This last is presented with many details that explain the whole process. Mahdi Bayuargo, ST, MAScPT. Duaem Gada Bayuagus Managing Director

Inhaltsverzeichnis

Frontmatter

Chapter 1. Introduction

Abstract

Question—“Is mine seismology quantitative or qualitative?” The answer is straight forward as by its very nature the seismic source parameters are only estimates and in being objective they can be described as a conclusion of an educated guess. Once the main reason for mine seismology being qualitative is removed this may be a matter for future debates. Up to now, the dividing wall from it being considered qualitative is the measuring device the seismological software itself. With each software update, the resulting source parameters are different from the previous ones and the differences can be significant. It is as if with every new version of the software something fundamental is changed. As an example, take the definition of a metre. The metre is defined as the length of the path travelled by light in a vacuum in 1/299 792 458th of a second. Now just imagine the resulting pandemonium if various industries or research institutions used whatever definition of a metre they wanted at any specific time. It is for this very reason that I did not agree to an update to the PMC’s seismic processing software and right up to the end of 2013 all recorded data was processed using one version of the software. As a result, the PMC seismic database was consistent and allowed for a very detailed analysis of the caving process as evidenced by the recorded seismicity. All analysis and interpretation of this nearly perfect database was based on trends and their changes with the process of caving. This is typical for qualitative analysis (Glazer 2016).

S. N. Glazer

Chapter 2. Seismic Data Assessment

Abstract

In this chapter, I presented seismic data that was made available for analysis and interpretation. This data originated from four mines: El Teniente Diablo Regimento Sector (DR Sector), Northparkes Mines Lift 2 (NPM), PT Freeport Indonesia DOZ Mine (DOZ) and Palabora Mining Company (PMC). I have compared small size events that were recorded at the different mines against each other. The presented very basic data analysis leads to two important conclusions:

Hydro-fracturing resulted in seismicity with lower seismic energy releases than in other mines.
One of the mines was using a different and faulty version of the seismic processing software.

These conclusions were only possible because the analysis involved seismic data recorded in several mines. With regard to quality control of some of the seismic databases, the facts indicate that the quality decreases when the processing task is given to external contractor who is operating outside of the mine. Most of the recorded small size seismic events are an indication of the cave propagation process. This seismicity is a natural process indicating that the cave is progressing. The space and time distribution of these seismic events along with the changes of their source parameter values over time should be associated directly with what is happening in the rock mass around the cave and the mining excavations. Unfortunately, this is not always true as in some cases these changes can also be attributed to the difference in software versions or to the reprocessing after a new version of the software was installed.

S. N. Glazer

Chapter 3. Seismic Signature of the Caving Process

Abstract

The four seismic catalogues analysed in this chapter contain range from a couple of thousand events right up to a couple of hundred thousand events. The four seismic data sets are not only consistent as separate input catalogues, but also as a whole. The mines in question are not only using the same seismic system in the recording of the seismicity but the recorded data was subsequently processed using the same version of the software. Because of this the input data available was not only in sufficient quantity but also quality. I used two types of parameters in analysing the presented data. The first is based on the mining data and the second is derived from seismicity. By definition, the seismicity that I was analysing is mine-induced seismicity. The definition implies that there is a strong relationship between the mining activities and seismic parameters. This relationship is certainly there but it is not continuous in its nature, nor is it constant. As I have illustrated, an increase in production rates will not always result in an increase of the seismicity rates or in larger size seismicity taking place. The dependency between production and seismicity changes over time due to the progress of the caving process. The seismicity parameters that I have used are based on seismic moment and seismic energy, which are independent of each other. I have also used the locations of the seismicity as well as the rates. It is obvious that the seismicity rates, their locations and source parameters are independent of each other, and thus provide discrete results. The presented seismic data analysis and interpretation resulted in a description of precise and detailed seismic response to the caving process.

S. N. Glazer

Chapter 4. Comparison of Seismicity Induced While Mining Hydro-fractured and Non-preconditioned Rock Mass Volumes

Abstract

In this chapter, I will be comparing seismicity recorded in the Diablo Regimento hydro-fractured cave with the seismicity recorded in the two non-preconditioned caves of PMC and DOZ. For comparison between mines, I will be using cave volumes. At Diablo Regimento Sector, the cave volume that will was used is the volume that was reconditioned with the hydro-fracturing technique. Analysis of the seismicity recorded in the three caves presented in this chapter leads to a number of conclusions. The most important one is that the preconditioning of the DR rock mass had to result in substantial fracturing of the rock mass. A similar rock mass condition to what was already in place at DR right from the commencement of the cave mining, was achieved only after nearly 3 years of production at PMC. The PMC rock mass was gradually preconditioned by the caving process.

S. N. Glazer

Chapter 5. Summary and Conclusions

Abstract

Everything I have presented in my mine seismology trilogy appears to be very simple and uncomplicated. The most complicated tool used in research was the concept of Energy Index or Apparent Stress Index. The second most difficult element presented was the percentages perception. It seems that what I consider to be research might not come close to genuine research. What is then genuine research? Genuine research must start with a question, which then can be turned into an idea. In my case, the first question I asked myself as early as 1990 was: “How to make use of all the recorded seismicity in the analysis and interpretation process?” (Glazer in Mine seismology: seismic warning concept. Case study from Vaal Reefs gold mine, South Africa, Springer International Publishing, Switzerland, 2017) The answer or the idea was the Apparent Stress Index concept. At the time, the mine was experiencing severe problems with underground safety due to seismicity. That was the rationale for the next question: “Can the Index be used to solve or at least reduce this problem?” During 2002, I asked myself another question: “Can the recorded seismicity be used to monitor the caving process and the related seismic hazard?” As a result, there is now a methodology available on how to use the recorded seismicity to monitor the caving process. It is described in detail so that it can be used by others. These in my opinion are examples of where genuine research was followed up by implementation. In conclusion, I do not feel embarrassed that my research ended with the development of some very simple tools. These uncomplicated tools were used to solve complicated and complex problems. When the end result of the research, is the development of some very complicated super tools, then it is easy to forget their purpose. It appears that these tools then have a life of their own in which they must be maintained nonstop by adding life support apparatuses just to keep them alive. They also require plastic surgery just to keep them beautiful and attractive.

S. N. Glazer

Backmatter

Titel: Mine Seismology: Seismic Response to the Caving Process
verfasst von: Dr. S.N. Glazer
Verlag: Springer International Publishing
Electronic ISBN: 978-3-319-95573-5
Print ISBN: 978-3-319-95572-8
DOI: https://doi.org/10.1007/978-3-319-95573-5