25th International Conference on Ground Control in Mining 

51

ABSTRACT 

 During the past quarter century, coal mine geologists have 

evolved from providing a qualitative description of drill core and 

coal reserves into quantitative geotechnical specialists who bridge 

the gap between geology and engineering. In the late 1970’s and 

early 1980’s, hazard prediction mapping was in its infancy. At 

best, hazard maps identified rudimentary structures and conditions 

such as stream valley locations, sandstone/shale transition zones, 

and lineaments. A “technical disconnect” had existed between 

geologists and mining engineers as each profession operated 

largely independent of each other. Engineers did not readily 

integrate geology and geologic conditions, with the exception of 

coal thickness, into mine planning. Geologists were relied upon for 

reserve estimates and did not participate in mine planning or 

design. The employment and market slump of the 1980’s and 

1990’s combined with mining more challenging reserves mandated 

that this gap be bridged and forced geologists to learn to speak 

more “numerically” to engineers so they could be understood. The 

purpose of this paper is to describe the procedures and thought 

processes used by coal mine geologists when determining various 

mineability and reserve extraction feasibility issues. The paper will 

also address underground geologic hazard mapping and prediction 

techniques. To achieve these objectives, the opinions and 

experiences of leading coal mine geologists, geotechnical and strata 

control specialists across the United States were solicited. 

INTRODUCTION 

 The duties and responsibilities of a coal mine geologist have 

changed considerably since the First Conference on Ground 

Control in Mining was held. A quarter century ago, a geologist’s 

primary concern was to locate the coal and to determine its 

thickness, quantity and quality. Stratigraphic correlations were also 

made between core holes to delineate rock unit positions and locate 

geologic anomalies like stream channels or faults. These crosssections were hand-drawn on mylar and hung from the office walls 

for engineering and operations personnel to review. Resident 

mining engineers were never at a loss for derogatory remarks about 

following the dots or playing with colored pencils. Engineers had a 

basic lack of understanding for depositional environments and 

facies changes which often resulted in orienting mine headings into 

unfavorable roof and horizontal stress conditions. Engineers 

widely held the belief that geologic conditions including seam 

splitting, facies changes, sandstone channels, and horizontal 

stresses and therefore ground control conditions were 

unpredictable. A mining engineer typically had two undergraduate 

geology courses that was limited to memorizing the different eras, 

basic geologic structures, plate tectonics, mineralogy, and the 

identification of igneous, metamorphic, and sedimentary rocks. 

The lack of knowledge and understanding of coal measure geology 

left the engineer able to recognize poor roof conditions through 

experience but unable to correlate current in-mine conditions to 

future conditions through drill core. A new coal mine geologist 

quickly learned that mining engineers knew little about the strata 

above and below the seam of interest. The concept of using hazard 

prediction mapping in order to identify zones of potential roof 

instability was fairly novel (Peng, 1978; Custer and Gaddy, 1981) 

at the time of the First Conference. The more sophisticated maps 

may have included geologic structures and conditions like 

transition zones, lineaments, stream valleys and topographic 

information. 

 Nearly all the people queried during this study indicated that 

to the best of their recollection, most geologists spent very little 

time underground prior to the early 1980’s. If there was a problem 

that was geologic in nature, geologists would sometimes go 

underground to make observations and render opinions. But, for 

the most part, geologists spent the majority of their time on drill 

rigs, logging core, or in the office working on reserve analyses. 

Subsequent to that, due to financial constrictions that occurred 

during the 1980’s and 1990’s and when the true cost of a roof fall 

was calculated, geologists started spending more and more time 

underground mapping hazards and establishing viable answers to 

roof falls. Many companies quickly realized the cost-effectiveness 

and other advantages of having a well trained eye underground 

observing subtle structures and other details that were lost on 

engineers, some of which were precursors of geologic hazards or 

conditions which dramatically affect mining. Previously, these 

details went unnoticed until the mine hit a sandstone channel, fault, 

or poor roof conditions which necessitated the operator to aimlessly 

turn headings left and right without success until the area had to be 

abandoned. Other mine operators were made aware of the benefits 

of underground mapping and geologic forecasting techniques 

through presentations delivered at the International Conference on 

Ground Control in Mining over the past quarter century. 

 

 The purpose of this paper is to present an assessment of the 

current state-of-the-art in coal mine geology. To this end, 12 senior 

COAL MINE GEOLOGY IN THE U.S. COAL FIELDS: A STATE-OF-THE-ART 

Frank E. Chase, Research Geologist 

NIOSH-Pittsburgh Research Laboratory 

Pittsburgh, PA, USA 

David Newman, President 

Appalachian Mining and Engineering, Inc. 

Lexington, KY, USA 

John Rusnak, Vice President 

Engineering, Peabody Energy 

St. Louis, MO, USA
25th International Conference on Ground Control in Mining 

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coal mine geologists, geotechnical and strata control specialists 

from across the United States were questioned regarding their “dayto-day” duties and responsibilities. It isn’t surprising that the 

majority of the respondents were from larger companies that 

operate longwalls. Longwall mining is the most sensitive and least 

able to adapt to geologic changes. By its nature, longwall mining is 

a capital intensive commitment to a 1,000 by 14,000-foot block of 

reserve that are the typical dimensions of the modern panel. The 

panel requires approximately 6 to 7 months to develop and nearly 

the same amount of time to mine. Because 80 to 90 percent of a 

large mine’s production is dependent upon a longwall, a failure to 

understand the geology can be a financial catastrophe. 

RESERVE EVALUATIONS 

 The amount of effort that goes into a reserve evaluation is 

somewhat proportional to its relative value and variability. For 

example, in a one-section hill top operation in central Appalachia, 

once the necessary drilling for coal thickness and acid/base 

(NP/PA) testing is conducted for permitting, the drill rig is moved 

to the next mine. Hill top reserves are generally small (200,000 to 

1,000,000-tons) and short lived (1-3 years). If the continuous 

miner encounters a sandstone washout or a fault, the operator will 

normally back out a few breaks, and drive a new butt off the 

crosscut. The reserve evaluations are normally based upon 3 to 5 

drill holes and confirmed by the ripper head of the miner. If the 

operator runs out of headings, they will backfill the drift mouth and 

move on to the next hill top. The diametrically opposite 

philosophy is reflected in one northern Appalachian longwall mine 

where the coal quality is variable and the geologic conditions 

change routinely. Coreholes are drilled on 800-foot centers along 

the center of each panel. Conversely, at a longwalling operation 

located in the Yampa Coal Field of Colorado, there is quite 

frequently very little variation in the core from holes drilled more 

than a mile apart. However, to be conservative, holes are drilled on 

one-half mile centers. The reason for variation, or lack thereof, in 

these longwall examples is the depositional environments in which 

these formations were deposited and later lithified. Depositional 

modeling was a relatively new concept 25 years ago because the 

majority of the principles were introduced in the mid 1970’s 

(Donaldson, 1974; Ferm, 1974; and Horne et al, 1978). Today, 

depositional modeling is a cornerstone of coal mine geology and is 

routinely used to spot drill hole locations, explain underground 

variations, and even predict geologic anomalies. 

 In general, it was reported that a wider exploratory drill hole 

pattern was employed for room-and-pillar operations due to the 

greater flexibility of the equipment. Conversely, a tighter plan is 

utilized for longwall operations because the financial viability of 

the mine is totally dependent upon the longwall panel and the 

ability to mine in excess of 20,000 clean tons/day. Therefore, drill 

hole spacing is a function of economic components, the regularity 

or uniformity of the reserve and the abundance or lack of 

anomalies, partings, seam splitting, etc. Corehole placement is also 

subject to restrictions such as land ownership, physical access, 

surface topography, and even political constraints. 

 Once the core has been collected, the geologist must provide 

an accurate description that should be understood from a “mining” 

viewpoint as well as determining what type of testing should be 

done on it. Normally, a proximate analysis is conducted on 

selected coal samples at an analytical laboratory. In addition, 

customers may also request that an ash mineral analysis, trace 

element analysis or grindability test be performed. Less than half 

of the geologists reported regularly sending coal samples to 

commercial laboratories for compressive strength and shear 

strength testing. While other geologists indicated that uniaxial 

compressive or shear strength tests were only conducted when 

pillar design problems occurred or when requested by an 

engineering consultant. Depending on the geologist, anywhere 

from 10 to 100-feet of roof rock core is retrieved and closely 

examined. The most common answers were from 20 to 30 feet. 

When the core is removed from the core barrel, all the fractures are 

marked with an indelible marker or lumber crayon to delineate 

naturally occurring fractures from those induced to fit the core into 

boxes. Fracture spacing and Rock Quality Designation (RQD) 

measurements can then be taken in the field or later to determine 

the inherent quality of the immediate roof. Approximately one half 

the geologists responded that uniaxial compressive strength testing 

was routinely performed on immediate roof rock members within 

and slightly above the bolted horizon. A few geologists stated that 

tensile and shear strength testing was also conducted on the roof 

rock. Other geologists indicated that physical properties testing 

was expensive and time consuming, and that the only time samples 

were sent for analyses was on rare occasions. 

All the geologists, except two, reported that they analyzed the first 

10 feet of floor rock. The other two examined the first 20 feet of 

floor rock. It should be noted that it is important to identify weak 

floor units, which have a low load bearing capacity and/or are 

moisture sensitive. One of the problems with these units is that 

they can heave on development causing reject and out of seam 

dilution issues. 

 A tremendous asset in bridging the gap between geologists and 

engineers, which has come into widespread usage since the First 

Conference, is the Ferm code for coal measure rocks (Ferm and 

Melton, 1977; Ferm and Smith, 1981; Ferm and Weisenfluh,1981). 

The code provides a unique number for common coal measure 

lithologies and has established a common language for the two 

professions. An engineer can immediately form a mental image of 

a 322-FLT or a flat dark gray shale and interbedded sandstone. In 

the engineer’s vernacular 322-FLT is “Zebra-rock” or “stack rock”, 

and associated with poor roof, especially in high horizontal stress 

conditions. Prior to the Ferm code’s, a typical qualitative geologic 

description may have been something on the order of a gray to dark 

gray medium to fine grained, thinly laminated shaley micaceous 

sandstone with plant fossils on the bedding planes. The “Ferm” 

books have a “dry” and “wet” picture for each numbered lithology 

for reference. Core photography may be done is some cases. This 

provides for an excellent record for later review and presentation to 

operations personnel. Though photographing core in the field can 

be difficult at times, the advent of digital photography has made 

this more effective from the standpoint of being able to see the 

photo when it is taken and make adjustments if necessary. Also it 

allows for easy storage and transfer of the photos. 

 All the geologists stated that geophysical/electric logs (E-logs) 

were routinely run on every drill hole. A few of the geologists 

pointed out that these logs provided a good method of doublechecking or verifying the driller’s core log depths, rock unit types, 

and for making various geologic correlations. As for sonic velocity 

logs, approximately one third of the geologists responded that they 

always ran them, while approximately the same number said they 

never used sonic logs. The remainder indicated that they have run 

sonic velocity logs from time to time, for example, if requested by 

a consultant, when exploring a new reserve, or for seismic profiles 

when looking for faults. Sonic velocity logs are also run to 

determine in situ rock strength and density, Young’s modulus, and 
25th International Conference on Ground Control in Mining 

53

Poisson’s ratio. Gas desorption testing may also be carried out at 

the drill site. This data may be utilized during ventilation design or 

when considering methane drainage techniques if necessary. 

 Other physical property determinations of roof or floor core 

that may be conducted by the geologist or in a laboratory include: 

Slake Durability, Point Load Testing (PLT), Fracture Analyses, or 

Coal Mine Roof Rating System (CMRR) analyses. The CMRR is a 

rock mass classification system designed to estimate the inherent 

strength of bedded coal measure rocks. It utilizes a number of rock 

mass properties including estimated uniaxial compressive strength 

(UCS), moisture sensitivity, and the presence of strong strata within 

the bolted horizon. It recognizes the importance of bedding to rock 

mass stability by placing special emphasis on the tensile strength, 

cohesion, and frequency of bedding planes within defined units in 

the roof. Bedding strength of rock core is measured using the point 

load index test. Data entry is made and strength values are 

calculated with the National Institute of Occupational Safety and 

Health’s CMRR software. 

 At this point, the geologist must turn into a detective. Every 

possible information resource on the reserve being investigated 

needs to be examined. This includes any available oil and gas Elogs, County Reports, professional papers, theses, dissertations, and 

Federal and State Geological Surveys. Geologic Surveys have 

various types of geological quadrangle maps. Abandoned mine 

maps may be obtained from the State Geologic Survey or the 

Office of Surface Mining. Maps of active mines may be examined 

at State and the Mine Safety and Health Administration (MSHA) 

District offices. A few State Geologic Surveys, most notably 

Kentucky, have excellent web site locations. Sometimes relevant 

data can be found on mine maps adjacent to the reserve in question 

like mining heights. One can also try to inspect the mining extents 

near the proposed reserve, are they erratic, headings dropped off, 

panels abandoned, or maybe the coal was not developed, why? 

Possibly a section was advanced, but was not retreated, or only 

partially retreated, again, why? Or, the area was advanced and 

retreat mined cleanly. Each of these scenarios has pertinent 

information and needs to be considered. Also, maps that show 

overmining or undermining need to be scrutinized for future 

multiple seam load transfer problems associated with remnant 

structures. If the proposed mine will be conducting full extraction 

in an undermining situation, the possibility for water inflow 

occurring must be closely examined. Although a lot can be said for 

a well-trained eye when reviewing these maps, it is advisable to 

question someone who actually worked at the mine with map in 

hand. Normally, the mine manager, superintendent, foreman 

and/or engineer would be solicited for an interview. Some of the 

geologists questioned indicated that it was surprising how much 

pertinent information can be obtained through this kind of process. 

While other geologists remarked that some of their experiences 

with second party perspectives have proven to be distorted and that 

hindsight is not always 20/20. Like history, if you don’t understand 

the circumstances and mining conditions in an adjacent abandoned 

mine, you may be doomed to repeat the failures of the previous 

mine. 

 Once all this information has been correlated and analyzed by 

the geologist, it will be forwarded to property acquisitions 

management personnel for consideration. If the reserve was 

previously acquired, the package will usually be sent to the 

Engineering Manager. 

 Exploration drilling, analytical testing, geological data 

collection and interpretation all play keys roles is allowing a coal 

geologist to define a particular coal deposit. An accurate definition 

of the attributes of a coal deposit is essential in order for engineers 

to formulate a viable economic mine plan. The vast amounts of 

data collected must be able to be stored, retrieved, analyzed, 

updated and re-stored for future use. This effort has been made 

possible with the ever increasing improvement in computer 

databases, geographic information systems (GIS) and geological 

modeling / mine planning software. Today a coal geologist must be 

well versed in computer applications in order to be effective. Gone 

forever are the days of hand drafting maps and cross-sections. 

 There also needs to be a close collaboration between 

geologists and mine planning engineers. It is the task of the 

geologist to define the coal deposit from which the engineer can 

design a mine. Just as the engineer needs to strive to understand 

geologic processes, the geologist should seek to gain an increasing 

knowledge of mine operations in regards to equipment selection, 

productivity, coal haulage and coal preparation. This engineering 

knowledge will assist the geologist from exploration data collection 

through reserve modeling to provide for the best definition of the 

coal deposit from which a successful mine plan can be developed. 

TROUBLESOME GEOLOGIC STRUCTURES AND 

CONDITIONS 

 Throughout the history of coal mining, geologic structures and 

conditions have been responsible for serious injuries and fatalities. 

Prior to the First Conference on Ground Control in Mining, 

published investigations on troublesome underground features were 

not common. Consequently, geologic structures were routinely 

misidentified and frequently inadequately supported. For these 

reasons, the MSHA prompted the former U.S. Bureau of Mines 

(USBM) to investigate several hazardous geologic structures and 

conditions during the late 1970’s and 1980’s. The purposes of 

these studies were 1) to examine the physical characteristics of the 

geologic anomalies in order to make support and other mining 

recommendations to help mitigate the problems associated with 

each feature. And 2), to determine methods to predict the hazards 

in advance of mining, if possible. Detailed investigations were 

conducted on clay veins (clastic or sedimentary dikes), faults, hill 

seams, kettlebottoms, paleochannels, and slickensides. All the 

geologists interviewed indicated that they had experienced 

problems with one of more of these structures to varying degrees. 

The most difficulties were reportedly associated with faults, one of 

which had a displacement of 200 feet. In another example given, 

no anomalies were detected in the mains, gateroads, or in the setup 

rooms during development. However, the shearer mined into a 

fault midway through the panel which wreaked havoc on the face 

for scores of feet of retreat. Roof control problems and face 

ignitions related to clay veins were also pointed out. 

 Problems with delineating paleochannels over a mile wide 

were also mentioned. The Galatia channel in southern Illinois is 

perhaps the best known most studied channel in coal mine geology. 

This channel is so extensive that it determines the boundaries 

between mine properties. Troubles were cited even when trying to 

mine through small channels. For example, a lesser known 

unnamed channel exists across three counties in southeastern 

Kentucky. Instead of drilling to locate the thinnest portions of the 

channel to develop across, lack of geological guidance led the 

company to repeatedly mine against the want, defining the 

perimeter using a continuous miner. When no other options existed 

for crossing the channel, a continuous miner was used to drive a 

three entry system through the channel. Eighteen months and a 
25th International Conference on Ground Control in Mining 

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worn-out JOY 12 CM later, the project was completed. Therefore, 

in order to avoid production interruptions, it is imperative to 

delineate the extent of channels, faults, and other major geologic 

anomalies so that their location can be incorporated into the mine 

layout and planning process. All the geologists indicated that they 

employ surface drilling to identify geologically disturbed zones 

from minable coal reserves. Depending on the structure trying to 

be pinpointed, geologists reported drilling holes as closely spaced 

as 50 feet apart. 

 Other structures which the geologists interviewed stated 

having problems with included undetected slickenslided slips or 

intersecting slickenslided slips which are commonly referred to as 

being horsebacks. On average, several serious injuries and a 

fatality occur each year due to undetected slips or horsebacks. A 

few geologists also indicated that they have experienced problems 

with well-defined roof joints which disrupt the lateral continuity of 

the roof beam. These joints can cause the roof to cantilever and/or 

segment it into blocks and necessitate a change in the heading 

orientation. Some of the respondents also had problems with wellpronounced face cleat. This is difficult for someone to understand 

until they have stood in a ten plus foot high entry of coal at 

1,500 feet of cover or more and experienced the magnitude of a rib 

roll. In this situation, the general consensus is that roadways 

should be driven at 45 degrees to the face cleat. 

 Almost universally, it was reported that roof control problems 

occurred under stream valleys and shallow cover. These poor 

ground conditions have been attributable to stress relief (Fergusen, 

1967), and are commonly referred to as “snap top” by the miners. 

Snap top, because when initially undermined, the roof makes a 

snapping sound. Bedding plane faults, which sometimes occur in 

areas which were tectonically active, were only mentioned as being 

troublesome by a few geologists but still warrant being addressed 

due to the lack of published material on the topic. Bedding plane 

faults are thought to occur when rock units are subjected to 

compressive forces and flexural slip folding occurs. During the 

folding process, rock units move relative to each other as shown in 

figure 1. A good analogy would be to consider a series of rock 

units as being a deck of playing cards. Now, bend the cards and 

you can visualize how the cards move or slide over one another. 

The same is true with rock units. Supposing prior to folding the 

rock units, you have a geologic structure, for instance a clay vein, 

penetrating through the roof and coalbed. After folding, this clay 

vein is segmented and displaced along the various bedding plane 

faults as shown in figure 1. As illustrated in figure 1, when this 

type of flexural slip folding occurs, roof rock is displaced up dip 

relative to floor units. In addition, supplemental support should be 

considered up dip because seemingly good top could be masking 

disturbed roof rock. 

 Most of the geologists from the Western Coalfields and to a 

lesser extent the Midwest mentioned difficulties with igneous dikes 

and sills. The concern is so great that they have gone to the 

expense of conducting airborne magnetic surveys to locate deep 

seated intrusions. Although not strictly limited to Western Mines, 

igneous dikes are rare in Eastern Mines but have affected 

operations in Eastern Illinois. 

 Several of the geologists questioned indicated that high 

horizontal stresses pose a major operational concern at their mines. 

Since the First Conference was held, considerable insight has been 

acquired through field studies examining the affects of high 

horizontal stresses in underground coal mines. This Conference 

has provided a forum for many of these investigations which have 

examined several important issues including panel orientation, 

advance and retreat directions, panel sequencing, and various other 

related topics. The majority of the geologists surveyed reported 

having experienced significant mining related problems associated 

with one or more of the following rock types or structures: 

sandstone/shale transition zones (roof brows), splay deposits (stack 

rock conditions), slumps, rock partings in the coalbed, rider 

coalbeds, and/or inherently incompetent roof rock. 

Figure 1. Bedding plane fault diagram. 
25th International Conference on Ground Control in Mining 

55

UNDERGROUND GEOLOGIC MAPPING AND 

PREDICTION TECHNIQUES 

 A considerable amount of pertinent information can also be 

obtained from underground observations and mapping. These 

examinations are best made at the working faces prior to rock 

dusting. Roof bolt operators can often provide a wealth of 

knowledge on rock types and quality and always seem to be willing 

to share their perspectives with you when asked. It is critical that a 

geologist earn some degree of credibility and gain the respect of the 

section personnel. As one geologist remarked, “you can’t be 

underground every day so the section personnel have to be your 

eyes and ears.” Information gathered underground can be used to 

augment and refine previous correlations and to fill in the blanks 

from drill holes surrounding the adjacent workings. Another 

geologist stated that “underground mapping goes hand in hand with 

exploratory core hole drilling, you refine the maps as you mine and 

you drill when you need additional data, it’s an evolutionary 

process.” When it comes to underground mapping, one geologist 

summed it up well by saying “a good geologist observes 

everything, measures everything, and writes down everything.” 

 Once a troublesome geologic anomaly is identified, the 

feature’s lateral extents need to be defined through vertical drilling, 

underground mapping, and sometimes, commercially available 

geophysical techniques are employed. Economically driven 

decisions on how to cross these structures also need to be 

addressed, for example, is it cheaper to sink a new shaft? The 

majority of the geologists reported routinely constructing geologic 

conditions/forecast/projections maps which are generated on a 

weekly or biweekly basis. Commonly, these maps are colored 

green, yellow (orange), and red indicating the likelihood of 

encountering mine impeding geologic anomalies or other problems 

in the highlighted areas. The geologist’s explanation for the color 

coding should be understandable and well documented. For 

example, in an area shaded yellow, the presence of a rider coal at or 

slightly above anchorage might be anticipated based on drill logs. 

Therefore, the face boss will be instructed to have the bolter 

operators drill a test hole one or more feet above the anchorage 

horizon at every crosscut for instance. Addition descriptions and 

details on the roof can be obtained through the use of a fiberscope 

or camera to examine the test holes. Red zones are mineable, but 

normally warrant some kind of precautionary measures and/or 

supplemental support. Geologic conditions maps are typically 

posted in the mine manager, superintendent and mine foreman’s 

offices. Some mines also display them in the shift change areas, 

underground dinner holes, and even in the bath house. Face 

personnel should be made aware geologic conditions if impending 

changes are anticipated. Further, the crew should report back as to 

what they encounter while mining and roof bolting during their 

shift. 

 At this point, the reader may be asking how do you construct 

these geologic conditions maps or project structures into unmined 

portions of the coalbed? The most appropriate response is probably 

a good working knowledge of depositional environments and an 

experienced past history. One needs to have a familiarity with the 

characteristics of the features encountered on the property. For 

example, normally are they linear or curvilinear? Usually, how 

wide are they? Generally, are they persistent or do they scour 

down out of the roof and just as quickly disappear? Is there 

anything observable in the coalbed or roof that will forecast an 

impending problem structure or condition? Where do I drill to 

pinpoint the extent of the structure or find the coal? Therefore, to 

try to answer the question at the beginning of the paragraph 

requires intitution, and almost a “sixth sense.” As previously 

indicated, 12 geologists were surveyed and each was asked if they 

had gathered any rules of thumb or tricks of the trade when it came 

to underground mapping and predicting geologic structures and 

conditions in advance of mining. The responses are summarized 

below: 

• When approaching a paleochannel, rock spars and channel 

lag deposits may occur in the roof and coalbed. The coal 

seam may thicken within 1-3 crosscuts from the channel. 

• Highly stressed ground conditions can occur at greater 

depths near paleochannel and igneous dikes and might 

cause bumps/thumps in the roof, coalbed, or floor. 

• When excessive water starts dripping from the roof, mining 

is near the margins of a paleochannel. 

• The size of plant fossils increase the closer you get to a 

paleochannel. That is to say, one should expect to find 

larger plant components like preserved trunks closer to the 

channel; whereas, fossilized branches are found further 

away from the channel. Also, the nearer you are to the 

channel the better aligned the fossils become. 

• Normally vertical coal cleat is sometimes inclined toward 

the trough of paleochannels. The more inclined the cleat is, 

the closer you are to the channel. Also, steep coalbed rolls 

are associated with channels and the coalbed can double in 

thickness. 

• Minor fracturing and faulting can be encountered just prior 

to mining into a major fault. 

• There is an increase in ground stresses as you near a major 

fault. In other operations, just the opposite was reported 

and approximately 50 feet from the fault the workings 

appeared stress relieved. 

• In southern West Virginia, most of the faults that occur 

outside of the overthrust belt are normal faults. A geologist 

at a large mining complex instructed the miners that in 

order to find the missing coalbed that they should locate the 

dip of the fault plane and go with or follow the dip in order 

to find the coalbed. 

• Kettlebottom concentrations will occur near paleochannel 

levees. 

• When a normally bright coal band turns dull, it may soon 

turn into a rock parting. 

The geologists were also questioned on what their experiences with 

lineaments have been. The general consensus was that they were 

another information source to examine. The critical question was, 

and always has been, are the linear features vertically penetrating 

and do they extend straight down all the way to the coalbed? For 

the most part, the geologists indicated good success with linears 

locating large scale regional structures like faults and igneous 

dikes. Some geologists also reported good correlations with linears 

locating straight and narrow stream valleys which are fracture 

controlled. One geologist stated that below these valleys poor roof 

conditions were prevalent when the depth of cover was less than 

500 feet. Another geologist had good success with linears finding 

hillseams on his mine property. A straight segment of a normally 

sinuous stream, creek, or river is correlative with a linement. 

Across the board, the geologists were skeptical of using lineaments 

as problem indicators of small scale features at greater depths. 
25th International Conference on Ground Control in Mining 

56

GEOTECHNICAL SPECIALIST: THE NEXT 

GENERATION 

In addition to previously mentioned responsibilities, the 

respondents indicated technical involvement to varying degrees 

with planning shafts, slopes, impoundments, dams, and surge 

binds. One geologist stated, that “if it has anything to do with 

rocks, I work on it.” Other reported duties include permitting and 

environmental work, hydrology, subsidence, underground 

instrumentation, and ventilation. To this end, the geologists 

surveyed suggested that those contemplating a career as a 

geotechnical specialists consider gaining a background in rock 

mechanics, geotechnical engineering, computer aided design 

(CAD), and in the various mining and geologic software 

modeling packages available. In addition, several geologists 

stressed the importance of acquiring a solid understanding of 

deltaic environments and sedimentation fundamentals, basic 

geologic field mapping techniques and good note taking abilities, 

and isopach mapping skills. 

SUMMARY 

Since the First Conference on Ground Control in Mining was 

held, the role of a coal mine geologist has changed dramatically. 

Todays geotechnical specialists are so to speak “wearing multiple 

hats” and time constraints have virtually mandated them to rely 

on software programs to construct cross-sections, isopach maps 

and other vital maps necessary for day to day mining operations. 

This was unheard of a quarter century ago, when this kind of 

information was generated by hand. Considerable time is also 

spent underground collecting the base-line data necessary for the 

engineer to make well-informed decisions. One geologist likened 

it to “handing a blind man a cane.” As far as the next quarter 

century is concerned, there is no doubt that the reserves will 

become more challenging from both geologic and mining induced 

causative factors. Our shallower cover, more easily mined 

reserves have been and are being depleted. We have no other 

choice than to go deeper. Some are mentioning mines on the 

drawing board exceeding a depth of 3,000 feet, which is indeed a 

different realm. In order to assess these demanding 

environments, geotechnical specialists who are well trained in 

geophysics and the engineering disciplines will be needed. One 

of the geologist surveyed summarized the role of a geologist well 

when she stated, “you have to look at the entire rock package, 

how does it look, will it get better, is there somewhere else we 

should be?” 

REFERENCES 

Custer, E.S. and Gaddy. F.L. [1981]. The Use of Geologic 

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