Determination and IT Supported Evaluation of Rock Mechanical Parameters and Thir Utilization During Application of Roof Bolting Techniques

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20" International Conference onGround Control In Mlnlng

Determinationand IT-supportedEvaluation of Rock MechanicalParameters and Their UtilizationDuringApplication of Roof Bolting

Techniques

Nikolaos Polysos, Chief Geologis t

D e u t s c h e S t e i n k o h l e A G

H e m e , G E R M AN Y

Stephan Peters, Senior Ge olog i s t

D e u t s c h e M o n t an T e c h n o l og i e G m b H

E s s e n , G E R M A NY

ABSTRACT

For the planning and driving of gateroads supported by roof boltsa practical conapt has been developed in order to determine the

geolog~cal and mck mechanical parameters derived fromexploration drillholes. Based on this, an assessment scheme for thedesign of roof bolting has been established.

The new methcds of inveshgation comprise of geotechnicallog g~o g f drill cores for the determination of structural-geologicalrock characteristics and complementary geophysical well-loggingwhich enables the evaluation of pem -pb ys~ cal nd rock mecharucalproperties. The tools and their measurements will be bneflypresented. The relationship between the geophysical log read~ngsand the geotechnical pa ra m te n w ill be illustrated.

The aim of the data acquisition is to im prove roof bolting designwhich is based on the assessment scheme. This will be adjusted tothe prevailing rock mechanical conditions and stands up to the

required stability of the gate roads.

In order to ensure consistent data acquisit~on, method of corelogging has been standardized for the respective demands. Toachieve t h ~ st was necessary to introduce specific parameters andnew methods. For the recording of h e a r and planar sbucturalelements at the drill core, a spscial system for the do cumen tat~on fthe ang les in relation to each other has been ~ e tp.

The rock mechaniaal parameters and their acquisition will beexplained. In order to carry out an objestive analysis as fast aspossible, sotbare bas been developed for the acquisition,management and presentation of the d ata. These programs and theirfunctions will also be presented. The software is characterized bybeing user-friendly and the flexibility of its interfaccs. Different

options for the combined presentation of input and evaluated datagive a more objective basis for the planning o f roof bolt design.

Examples will illustrate the operailanal implementation of the

results during the planning and driving phases.

Roof bolt support in DSK mines (DSK is the German coalmining division of RAG) is applied at min ~n g epths of up to 1,500m and under complex rock mechanical conditions caused by multi-

seam working and subsequent increase in pressure resulting h mprevious working bound aries (I).

The processing scheme for he application of roof bolt support in

this ldnd of deposit (2) is shown in Figun 1.

Figure 1 Plow chart for the application of roof bolt support

This process starts with the planning and design wns~deringgeotechnical and ro& mechanical parameters, proceeds to a high-quality execution of the construction accompanied by monitoringmasurementa and returns again to the design based on the f d b a c kof actually observed values. Equal significance u attributed to eachelement of this cycle. Support and advance technology, qualityassurance and mining of personnel represent the additionalcornerstones of the support system "roof bolting". In thisconnection, the importance of m easurement techniques (2.3.4) asan integrated pan of roadway heading has to be emphasized.Particularly d m g the working phase monitoring measnrementsplay a substantial role.

The operational target for a high er rate of advance under existingstability standards by applying roof bolt tnh niq ues can be reachedfrom a geomechanical point of view by colleaing and arsssinggeotechnical and rock mechanical parameters.These should then be

taken into consideration during planning anddesign.

ROCK CLASSIFICATION

Planning, design, on-sik4tendance and evaluation of DSK'sroof bolting projects allowed the systematization and quantification



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of geomechanical parameters which are decisive for themechanisms and influences in the interaction between rock and mofbolt support (3).

This led to the set-up of a rock technological evaluation schemecomprising 21 parameters. Weighted indices are assigned to theindividual properties (5). T he consecutively determined total of theindividual assessments results in a rock quality class in the form of

an overall graded index (Fig . 2).

2. Bed thickness struc ture (will be calculated by the software):

BlOO = > 0.80 [m]B80 = 0.80 - 0.60 [m]

B60 = 0.60 - 0.40 [m]B40 = 0.40 - 0.20 [m]B20 = 0.20 - 0.10 [m]B10 = ~ 0 . 1 0 m]

3. Rock properties:ko = cornac t

Figure 2: Rock classification system

Applying this classification scheme which has been adapted toconditions in German deposits, the rock to be cut through can beclassified already during the planning phase.

Resulting from this, a specific design of roof bolt support can becarried out adjusted to match the forecasted conditions. 'Ihis meansthat depe nd~ ng n the detemu ned rock type the Frequency of roofbolts and the connected suppolt resistance can be established. Theabsolute prerequisite for a rock assessment is the development of ageological and geotechnlcal logging method. It has to be tuned toGemumy's hard coal bearing formations com pri s~n g tandardized

lithological, structural-geological, and rock m echanical parameters.

GEOTECHNICAL ROCK DATA

Geotechn ical rock d ata can b e a cqu ~re d from drill cores, inadjacent exposures and in the road-head (6). Terms and definitionsof parameters from different surveys shou ld be coord inated in a waythat they complement each other.

In order to be able to combine geotechnical information fromdrill cores with that from subsequent logging of road-heads duringthe ongoing driving, a standardized geotechnical description of rockand structural features is necessary.

Within the scope of the geotechnical core logging, the followingcriteria and terms are used for the description of the strata and thestructure of bedding and bed thickness:

1. Structure of bedding:ug = massivere = regularly beddedUI = irregularly beddedwe = alternate bedding with sandstone bandsgb = bandedsub. R= subaquatic slumping

sandingFriablefractured / shearedlettenlike I mylonitized

The following properties demibe the type and character ofseparation planes:

4. Type:

Ss =K1 =

beddingioint

Br = fractureSf = schistosity

ER = relaxation fracture

5.a Character of separation plane surface:H = slickensided s urfaceSH = slickenside on be dding planeSP = polished slickenside ("Usen")ra = roughob = no findingsar = abrasionF A = fossil sepa ration planes, e.g. layers of fragmental

plant remains, shell bankKA = coaly layers, e.g. layers of vitrain, coal streaks

5.b Additional description of sepa ration plane surface:

gr = straight

gg = bentwl = undulating

ag = steppedmu = conchoidal

6. Character of separation plane:0 = open

g = closedk = cavernousz = fractured

7. Mineralization:

X = yes0 - noCa = Ca C0 3 (calcium carbonate)Fe = FeS2 (pyrite)Pb = PhS (galena)Zn = ZnS (sphalerite)Si = Si02 (quartz)Ba = Bas04 (baryte)

Finally, a description of tectonically disturbed sections of thecored drillho les is carried out, including a certain evaluation.



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Tectonic description of disturbed section: The horizontal angle between the dip direction of the beddiig

and the dip direction of a tectonic element, right hand rotated, is

g =m inor: compact rock mass with isolated joint s referred to as TW.m =m edium : jointed rock mass, rock brokens =in tense : intensely jointed rock mass, rock The angle TW can directly be read from the Gon-scale. Using

broken and sheared these data, every element can be re-orientated to its true dip and dip

z ='&red: rock mass almost completely direction, knowing the true dip parameters of the bedding .disintegrated, rock she ared, scaled into

each other, and mylonitized tThe abbreviations listed above occur consistently in the variouslogging and output formats.

In addition to the general stratig raph~ c nd tectonic core logging,geotechnical parameters 10 m above and below any workable seamare recorded. In the course of data acquisition, it is important towork with extreme accuracy of (drilling) depths, which allows thetrue orientated position of separation planes (e.g. "L6sen") to b eshown afterwards with respect to the seam roof.

Since the complex three-dimensional pattern of bedd ing planes,cleat systems and slickensided surfaces cannot be attributed to itstrue position immediately during logging, a simplified orientated

method has been developed. Individual separation planes aredescribed by two angle va lues based on a defined orientation of thecore. Considering borehole deviation and regional geology theirthree-dimensional position can be calculated by the data acquisitionprogram, with the bedding serv ing as a reference.

RELATION BETWEEN ANG LES OF SEPARATIONPLANES AND CORE AXIS

Relation behveen apparent dip of bedding (WaKS) and apparentdip of tectonic elements (WaKT)

The dip direction of the bedding planes has to be orientatedtowards 0 gon, (I gon = 0,9") i.e. apparent "north". The anglebetween the bedding and the core axis, i.e. drilling direction is

referred to as WaKS. The ang le between a tectonic element and thecore ax ~ s= dnlli ng direction) is referred to as WaKT.

Figure 3a: Relation between d ~ pirections

Tectonic

Element. (joint)1

Figure 3b: Example from a vertical drillho le

The W aKT of the joint (tectonic element) is 70 gon. The TW is137.5 gon relative to the dip direction of the bedding. The real dipdirection of the bedding is towards east, that is towards 100 gon.The true dip direction of the joint can be calculated as: 100 gon +

137,s gon = 237.5 gon. Therefore the true dip parameters of thejoint are: 70 gon (dip angle) towards 237.5 gon, i.e. towardsSSWISW.

General abbreviations:WAKS I T = angle between bedding I separation

plane and the core axis, i.e. drilling directionTW - horizontal angle between the dip

direct~ on f the bedding and the d ip direction of the separation plane(right hand rotated)

Provided true strike and dip of the bedding are known, possiblywith the aid of the diplog analysis, the true three-dimensionalposition of every single structural element can thus be defined andrepresented.

Additionally, the RQLD-factor is determined duringgeotechnical core logging. The RQLD (Rock Qualily LithologicDes igna tion)- factor is a (core-related) value for the degree of

natural internal fragme ntation of the rock mass.

This factor is quoted as a value between 0 and 100. For itsdetermination the size of the core fragments is related to the corediameter. The evaluation is always restricted to one individuallithological unit. This reflects the dependency of this parameter onthe lithology. When it comes to the description of heading faces



20a International Conference on Ground Control in Minlng

additional characteristics like degre e of fragmentation, deformation The new data acquisition program called COREDAT has been

structure and bed thickness properties are recorded. programmed in VB6. ACCESS 97's data engine serves as the database.

DATA ACQUISITION AND GRAPHICALPRESENTATION OF GEOTECH NICAL ROCK

PROPERTIES

In order to optimize the standardized geotechnical descriptionsof rock characteristics a data acquisition program has beendeveloped for storing and managing these data and also all otherdata obtained from the drill cores. Interfaces to other programs ofthe deposit's technological data base have also been developed,which allow analysis and fur ther processing of these data.

Geotechnical data are collected from the core and entered intothe data acquisition program COREDAT at the surface.Differentiated data acquisition has been made easier by thematicuser control. Subsequent to the input of drillhole deviation data or

by reading in a respective file points of penetration can becalculated in COREDAT. After the diplog analysis and theattribution of the true strike and dip of the strata, true 3D-positionso f the originally relatively recorded separation planes can a lso beworked out.

b ldMrion mQ Geotech"Wanalysis o f d s CI

1070m

1072mF121

1074m1076m

'm ,mP

Seam 24- - --078m

1080m

Figure 4: Presentation of logged drillhole section with additional geotechnical characteristics

The range of functions of CORED AT is fairly complex, because separation planes can b e determined, as well based on the drillholeit attends several interfaces. Besides pure data recording the deviation and the entered relations of the angles relative to thedrillhole deviation will be calculated using respective deviation bedding.data. Several printing options also will be available to the user.Points of penetration are calculated for all elements included in the In addition to data acquisition, management and analysis of drillsystem. Since the data input can be carried out according to core inform ation, the visualisation of geotechnical key pararneters

stratigraphy, core runs and num ber of boxes as well as according toplays an important part. In order to give the interpreter easy access

input of geotechnical structures, depth adjustmats will become to the information, the data arevisually processed.necessary in order to ensure, for instance, a problem-free editing ofcure losses. The graphical presentation of the complex information has been

developed following already commonly used patterns and extendedCodes for differen t rock types are backed up by a table with for geotec hnically relevan t parameters. Figure 4 shows a short

respective numbers. They are equivalent to the BIF2 - format (BIF = section of a drillhole in this newly developed panem of graphicalBoreholelnFormation) already in use. For the description of presentation. In order to get a sound diagram showing geotechnicageotechnical parameters previously not included in the BIF2-format inform ation as fast as possible, an additional program has beena revised B F Z + - format has been developed. By means of a drawn up generating these standardized diagrams automatically.

controlled input mask, the data acquisition has already beenoptimized practically orientated. Now, the program calculatesindependently e.g, the RQLD-factor. The true 3D-position of

245



20L intematlonal Conference on Ground Control In Mlnlng

DATA FLOW Thus, the required comparison between forecasted values andvalues actuallymeawed in the face canbe ensured.

The program for this synoptic presentation of geotechnical andstratigraphic characteristics is an application progranuned underACAD (7). The ACAD environment makes the graphical exchange GEO TECH NICA L PARA MET ERS FROMof this information easier. Simple merging with any kind of maps GEOPHY SICAL WE LL LOG S

and plans as well as with sections of adjacent drillholes has becomepossible. The program TEKCAD is an application based on C++ Interpretation methods for the determination of rock mechanical

which allows seneration of comoonents of this drawinn and to m e t e r s r om m ohvs i c a l borehole me am e me nt s a re de ve lo d. .combine them Znder ACAD in an; combination desired. 5 e IF2 t i8.9, 10). A proper calihrah on of th e derived parameters with tliose- format comorisinc all the data of the drillhole. serves as the determined on rock sanmles in laboratorv tests are carried out.~ "reading ih&kace.Additionally, this program has di & t access to theACCESS database of COREDAT and allows, therefore, the fast Geophysical well logs offer a suitable base for gwtahnicalsectional display of drillhole sections. evaluation of rocks. Lithological, structural and m k echanic

information can be derived from well logs (Fig. 7) (12). Twoprocedures hereby can he distinguished.

1. Direct derivation of petrophys ical, structural and elasticparameters from well logs.

2. Indirect determination of strength parameters from well logsafter a suitable calibration with rock mechanicmeasurwents in laboratory.

According to our experience the following information areobtained directly from geophysical borehole m easurements:

Lithology,

Rock structural features,Physical properties,

Elasticparameiers,

Weakness zones,

Direction of horizontal str ess field

Rock mechanic parameters as:

Figure 5: Data flow for geotahn ical data starling from aquis itionto final presentation. . Compressive strength,

Cohesion,Friction angle.Point load index,

Static young's modulus

can be derived from well logs after a proper calibration withlaboratory tests.

Our investigations have indicated that petropbysical information,especially those derived from acoustic measurementsare invaluableaids to geotechnical studies in mining and civil engineering becauseof their ability to charaderise geotechnically relevant properties and

tNT) structures of rocks.

Figure 6: Data flow from COREDAT to GTP-DB

Acoustic and op tical imaging of the borehole wall and drill coresallows exact mapping of fractures, joints, and strata. Zones of

weakness in solid formations can be derived from measurements ofseismic velocities and electrical resistivity.

Aonlication of borehole s?eonhvsics has the advantase of. u . < -providing formation parameters continuously and in situ.Information mthered hv different eeoohvsical methods toeether. .with additiolally a c q u k geological I geotechnical p&ers

T and definitions for the logging ofd rill core which are used provide an optimal input for an objective decision on support

in this program sequence are identical to those of the road-headdescriptions. %ugh this, a standardized rock evaluation has beenmade i~ossihle.



20* internationalConference on Ground Control In Mlnlng

Figure 7: Dynamic elastic modules calculated from density and seismic velocity logs as compared to volumetic analysis from weU logs(right) and core record (left) (12)

Application of geophysical memods provides valuableinformatton to solve many problem en co u n t ed in geotechnicalimmigatian for underground opPPtions. Mmwemnt s of densityan d velocity of compressional and shear w a v a will be wad M

aalouEate the elartic jwamtna of formations. Different litbelogioslunit6 with Qffemnt pGtmphyrical propetties can be reliablydetermined by comb i i evaluatiun of their log responses.Additionel propatim of these lithologic8 can then be m e d

based on 6eld experience and laborstory rests.

So far the methad fw ock evaluation as wc~wlted bove basbeen applied for the driving of c. 80,000 rnof r oo f bolted roadways.

With the help of two examples, the operational implementationof the results of geotechnical core logging and - based on this - thegeomechanicalmck evaluation will be demonstrated.

During planning and driving of a negngvlar mof bolteroadway in the Auguste Victoria mine (1 1, 12) c o d b o l a hav

been M e d and I& geotechnically in the course of the x p l o w a y work.The d w a y ied 1,050 rm deep and is expod t

high rack premre of up to 45 MPa due to p a d e l wakinboun&m above the targel oeam Zollvmein IR. The rock strengtwuim between 20 Nlmm' and 33 N M . According to thpnscnted evaluation demo, themck that bas to bemi saoss Fig8)may be clsgpifled asbeing vsry slightly squeezing.



20" InternattonalConferenceonGroundControl In Mlnlng

Figure 8: Geomechanical evaluation of seam Zollverein 112





20" International Conference on Ground Control In Mining

Figure 12: Geomechanical assessment, seam P 1



Figure 13: Two phase roof bolting, driving phase (a), workingphase @) ('IT = Tell Tale)

20'" Intematlonal Conf@rencaon Ground Control in Mining

In this case the roadway has been driven with a roof bolt 7. Peters, S.; SchlUter, R (1995): Enhanced PC-Aidedeequency of 0.92 a/d (Fig. 13 a). For the utilization of the Applications in Coal Bed Me thane Exploration Europeanroadway during working the roof bolt frequency was later Coal Conference 95 Prague, Czech Republic.supplemented to 1.77ad (Fig. 13 b). 8. To& A. 1999: Fuzzy classification for lithology

determination b m ell logs. In Geophysical A pplicationsof ArMcial Neural Nehvorks and Fuzzy Logic (ed. bySandham B. & Legget M.). Modern Approaches inGeophysics, Kluwer publication.

9. Deltom be J.L. Schepe rs R and Toum ani A. 1999: Thepractice of combined core image and image loginterpretation for shuctural, sedimentalogical andgeotechnical application. GEOVISION 99, InternationalSymposium on Imaging and Applications in Geology, 6-7May, Liege, Belgium.

10. Unterstell B., Toum ani, A., Polysos N, Rtlkers E, et. all.(2001): Application of Geophysical Well Logs inGeotechnical Evaluation of Subsurface Deposits andGeoengineering- Preview Borehole Geophysics. Australia.

II . Preusse, A.; H m o g, C.; Brandt, K.H.: Evaluation ofMeasurement System for Monitoring the Stability of RoofBolted Roadways with Rectangular Cross Section bySelected Examples. 19th Intern. Conference Ground Con tmlin Mining, Morgantown, 2000, pp. 241-248.

12. Vierhaus, R.; Arenk, A.: A u f f h g von Rechteck-Ankerstrecken als Abbaubegleitstrecken in Zonen hohenGebirgsdruckes.4. Intern. A nkerkolloquium, Aachen, 2001.

The continuous process of optimization of the pnsented andopationally tested geomechanical evaluation scheme for roof boltdesign will he complemented with the determination ofpebophysical parameters Rom geophysical logging of drillholes.

ACKNOWLEDGMENTS

This work was partly supported by a grant of the EuropeanCommission @ GKS-No. 7220-RRIO55).

REFERENCES

1. Lautsch, T.; Opolony. K.; Polysos, N.: The Utilization ofRockboltink! Tec hno lorn and M onitorinn Techniaues in theGetmanC&I Field. 1% Intern. Confer& ce Gro&d Controlin Mining, Morganrown, 2000, pp. 225-233.

2. Opolony, K; Polysos, N.: GebirgsspeziiischeKlassifiz~ening ir den E ~ns atz er Ankerausbaue und neueAnkerkonzepte. 3. Intern. Ankerkolloquium , Anchen, 1998

3. Opolony, K.; Polysos, N.; Barrel, R.; LBtTig, F.:AnkW techk be1 d n DSK - Theone und Prws, Glitokauf136, Nr. 3,2 000

4. Bartel, R.; LUttig, F.: Neue Schulungs- undQualit~tss~chenmgskoozepte der DSK fir dieAnkerstreckenauffahmng. 4. Intern. Ankerkolloquium,Aachen, 200 l

5. Opolony, K.; Polysos, N.: Neue D imensionierungswege undEnhvicklungen im Ankerausbau he1 DSK. 4. Intern.Anknkolloqu~um,Aachen, 2001

6. Peters, S.; Polysos, N.; Tang, U.: EDV-Programme fllr d ~ eAuhahme und DarsteUung von geotechnischcnGesteinJparamnem im unt-gigeil Steinkohlmberhau 4.

Intern. Ankerkolloquium, Aachen , 2001

Determination and IT Supported Evaluation of Rock Mechanical Parameters and Thir Utilization During Application of Roof Bolting Techniques

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