The document discusses core recovery in geological and civil engineering, focusing on its importance in determining the properties of soil and rock. It details methods of rock mass classification, various factors affecting core recovery, and approaches to sample collection. The research aims to enhance site investigations and objectively classify different rock masses for better engineering practices.

1. Core Recover CR

2. Contents:
1. Abstract
2. Introduction
3. Rock mass classification
3.1 Design methods
3.2 Objective
3.3 Benefits
3.4 Rock mass classification systems
4. Definition of core recovery
5. Core recovery use
5.1 Civil engineering
5.2 Geological area.
6. Factors that affects TCR
6.1 geological factors
6.2 technical factors6.2
7. Method of taking the core sample

3. 8. Problems occurred through taking the sample
9. Calculation method of core recovery
10. Measurement examples
11. Core recovery results
12. Conclusion
13. References
Contents:

4. 1. Abstract
• In this research, we‟ll discuss that the basic core recovery function is to determine
the initial state of the soil and rock mass strength, which in turn is related to many
technical and geological factors that affect it Obtaining results by analyzing the
sample resulting from drilling to different depths.
• These samples are used to discover soil problems and calculateTCR then we could
Concludesthe values of RQD.

5. 2. Introduction
• Site investigation is the process of the collection of information, the
considerationof data, calculation, and reportingwithout which the risks in the
ground beneath the site that cannot be known. So, there are a lot of methods of
boring and sampling depend on the soil type, Then testing, Engineering analysis
and finally geotechnical reports.
• UndisturbedSamplingof Rock (Rock Coring) is one of sampling methods
tends to know the rock quality and it‟s important to calculatethe FractureState.
It‟s A number of indices can be used for quantitative description of the fracture
state of the rock mass as determined from boreholecores. These are Total Core
Recovery, Solid Core Recovery, Rock Quality Designation and FractureIndex.
• These indices should be used whenever possibleto supplementthe description of
discontinuities in rock core. The measurement of these indices should followthe
measurement of TCR and is based on the definition of solid core

6. 3. Rock mass classification
3.1 Design methods (18)
In rock engineering, one can distinguish three design strategies: analytical,
empirical, and numerical. Empirical, i.e. rock mass analysis, methodsare
commonly used in feasibility studies and pre-design research, and sometimes also
in the final design.
3.2 Objectives (1 )
1. Identify the most significant parameters that influence a rock mass‟s behavior.
2. Divide a particularformulation of rock mass into groups of similar behavior-
varying qualityrock mass classes.

7. 3. Provide a basis for understandingthe propertiesof each type of rock mass
4. Relate the rock conditionsfaced at one locationto the conditionsand experiences
witnessed at others
5. Drive quantitative data and engineering guidelines
6. Provide common communication ground between engineers and geologists
3.3 Benefits (1 )
1. Improve the standard of site investigations by asking for minimum input data as
criteria for the classification.
2. To have quantitative information for the purposesof design.
3. Enablingbetter judgement of engineering and more effective communication on a
project.
4. Provide an understandingbasis for the characteristics of each rock mass

8. 3.4 Rock mass classification systems (22)
1. Systems For Tunneling:
- Rock Mass Rating (RMR). - Mining Rock Mass Rating (MRMR).
- Q-System .
2. Other Systems :
- New Austrian tunneling method (NATM). - Size Strength classification.
3. System For Slope engineering:
- Slope Mass Rating (SMR). - Q- Slope.
- Rock Mass Classification System for Rock Slopes .
- Slope Stability Probability Classification (SSPC).
4. Earliersystems : (22)
- Rock load classification method - Stand-up time classification
- Rock Quality Designation - Rock StructureRating (RSR)

9. • The total core recovery(TCR) is defined as the proportion of core recovered
to the total length of the drilled run. The core run is the length reported by the
drilleras the actual depth penetrated. The TCR includesboth the solid core and
the non-solid (or non-intact)core. ( )
• The recovery is measured in the field using a tape measure and the records are
made as lengths (not calculatedas ratios), and it's expressed as a percentage on
the boreholelog. ( )
4. Definition of core recovery
• This value may exceed 100% if core drilled during the previous run is recovered
in the run described. may generally be anticipated that weak rock and fracture
zones are most likely to be present in the sections of core not recovered. (1 )
• Although this index gives littleinformation on the characterof the material its
measurement is required in the logging of cores recovered from rocks, soils and
made ground such as concreteand brickwork. ( )

10. • Poor core recovery is thereforeindicative of poorrock mass strength. This
parameter is considerablyaffected by the quality of drilling and drilling tools
used. (1 )
• When recording the core recovery in any drill run, the core should be
reassembled as far as is possible, as many drillers tend to spread the core out in
the core box which gives a misleading impression of the recovery. Wherever
possible the logger should indicatethe probablereasons for core loss. (1 )
4. Definition of core recovery

11. 5. Core recovery use
1. Civil Engineering
It is used to determine foundation
depth by making site samples and
to determine the propertiesof
rocky soil and its spaces (3)
2. Geological area
It is used to determine the physical
and chemical propertiesof the rocky
soils and the formation of rocky soil
layers ( )
Fig. (1) Core Recovery

12. Fig. (2) E.g. drilling equipment
Fig . (3) Example steps to drill

13. 6. Factors that affect TCR
6.1 Geological factors ( )
1. soft friable ground due to alteration, weathering or leaching
2. unconsolidatedmaterials & unexpectedfault zones
3. broken ground with clay infill
4. solublecomponentsremoved by unsuitableflushing medium
5. high frequency of discontinuities per meter
6. cavities induced by karstic weathering alongjoints and faults and also
mining (stopes and caved zones)

14. 6.2 Technical factors ( )
1. The following list presents a summary of some of the factors that could
contributeto either low recovery or to badlybroken core, even in good
ground conditions:
2. bent inner tubeso that:
(a)the core will not travel up the tubeand will be subject to grinding;
(b) it rotateswith the outertubeagain disturbingand grinding the core;
and
(c) it fails to seat properlyin the outerbarrel resulting in total core loss
3. core spring missing, displaced, damaged, worn or not lubricated
4. vibration induced by poor equipment, insecure rig mountings and hole
deviation
5. blocked waterways
6. inexperienced drilleror drillerchasing productionbonus.
6. Factors that affect TCR

15. 7. Method of taking the core sample (6)
 The main unit that used in core drilling is the core run and this is the distance
drilled from one removal of core from the barrel to the next.
 Normally a run will extend for the full length of the core barrel (usually 3 m).
 Usually because the drill bit is clogged and is not cuttingthe in situ rock, the
drillermay terminate a core run short of the full length of the barrel.
The materialsthat pass up into the core barrel may be dividedinto :(10)
• Solid core pieces 100mm or more in length, called sticks
• Solid core less than 100mm length, called pieces
• Fragments of core (not full cylindrical sides)

16. Additional materials may
have been lostfrom
previouscore runs
including:(10)
 The core stump left from
the previous run.
 Material droppedfrom the
core barrel while its
previous withdrawal.
 Cuttings that settled when
drilling fluid circulation
stopped.
Fig (4): Core recovery example and RD computation (from FHWA-IF-02-034) (7)

17. 8. Types of core
drilling:(1)
(a) Single Tube Core Barrel .
(b) Rigid Type DoubleTube
Core Barrel .
(c) Swivel Type DoubleTube
Core Barrel .
Fig (5): Types of core drilling(1)

18. 9. Problems occurred through taking the sample
During taking core sample, errors can be induced by : (23)
1. Errors occurred in the estimation of true sample length due to measurement of
intersection angles and depths
2. The selection of unsuitablesample intervals concerningchanges in mineralogy, host
lithology, metallurgy, etc.
3. If core is lost in a mineralized interval or broken and disturbed, it presents 3 main
problems:
(i) Depth and thickness estimation is difficult for specific lithological or grade zones in
the overall mineralized zone.
(ii) Accurate estimation of the grade is impossible.
(iii) Accurate determination of tonnage factor is impossible.

19. 10. Calculation method of core recovery
Assuming that depth measurement and blockinghas been donecorrectlyand
checked
Core recover can be determined using the total core recovery (TCR) parameter,
which is defined as:
Total Core Recovery (TCR): (17)
It is the total length of the core recovered expressed as a percentage of the core run
length
Which used to :
1. Identify the amount of loss and the depth at which it occurs.
2. Then the losses is recorded using a tag such as “ Assessed Zones of Core Loss”
(AZCL).

20. 3. Recording ALL (AZCL) will allow correctionsto the actual depthsof the recovered
core and thus the true depth of any logging observations. (13) Fig1
But, this hides the fact that the qualityof the core may be poor and the measurement of
solid core
Recovery (SCR) is more accurate(13)
Fig 6: illustration of
core measurement (16)

21. Table 1:scheme for core recover recording (21)

22. 10.
Measurement
examples
Fig. (7) Calculation example of core recovery ( )

23. Fig. (8) Calculation example
of core recovery (1 )

24. 11. Core recovery results
Fig. (9) Calculation example of core recovery ( )

25. 12. Conclusion
• Core recovery is a simple step, But it's necessary because it lets the civil
engineer identify the soil and its faults, and then we were able to identify the
soil's properties.

26. 13. References:
1. British standard bs 5930:1999 code of practice for site investigations.
2. BIENIAWSKI, Z. T. "Engineering Classification of Jointed Rock Masses". TRANS. OF THE
SAICE, Vol. 15, No. 12, 1973.4
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Dominy - Technical note .
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sampling and assaying in a coarse gold environment‟, Appl. Earth Sci. (Trans. Inst. Min. Metall. B),
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5. Commission on Recommendations on Site Investigation Techniques. "Recommendations on Site
Investigation Techniques". INTERNATIONAL SOCIETY OF ROCK MECHANICS. Final Report
July 1975.
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pe pdh online | pdh center.

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handbook‟, 2nd edn, Littleton, Society of Mining Engineers
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Technical note
14. N. BARNTON, W. E. BAMFORD, C. M. BARTON et al.: „Suggested methods for the quantitative
description of discontinuities in rock masses‟, J. R

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29. 21. Soil and rock description in engineering practice david norbury consultant;director, david
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