unconfined compression tests on specimens from the drift ...unconfined compression tests on...

Unconfined Compression Tests on Specimens from theDrift Scale Test Area of the Exploratory Studies Facility

at Yucca Mountain, Nevada

Sandia National LaboratoriesAlbuquerque, NM 87185

30 May 1997

iechnical Data Information Form Number 306126

Data Tracking Number SNLO2100196001.001

Unconfined Compression TestSpecimen Assembly

Unconfined Compression Tests on Specimens from the DriftScale Test Area of the Exploratory Studies Facility at Yucca

Mountain, Nevada

Sandia National LaboratoriesAlbuquerque, NM 87185

30May 1997

Technical Data Information Form Number 306126

Data Tracking Number SNL02100196001.001

ABSTRACT

Sample material was recovered from the Drift Scale Test area in the Thermal Testing Facility(Alcove 5) of the Exploratory Studies Facility at Yucca Mountain, Nevada for laboratory thermaland mechanical properties tests. The objectives of these tests were to detect spatial variations inproperties and also to characterize the Drift Scale Test area. The results of the laboratorymechanical properties testing are reported here. Sixteen test specimens were prepared frommaterial taken from four instrumentation boreholes and tested in unconfined compression todetermine failure strrgth and static elastic moduli. Mean Young's modulus was 36.8 $3.5 GPa,mean Poisson's ratio was 0.20 O.04, and mean unconfined compressive strength was 176.4±65.8 MPa. The error bars represent plus or minus one standard deviation. Young's modulus,Poisson's ratio, and strength are all slightly higher than values obtained during characterization ofthe Single Heater Test area.

These tests were performed by Sandia National Laboratories during March and April of 1997.The specimens tested represent tuff specimens from the TSw2 thermal/mechanical unit and theTptpmn lithostratigraphic unit. All data used in the preparation of this report were collectedunder Sandia National Laboratories' Quality Assurance program.

Unconfined Compression Tests on Specimens from the Drift Scale Test Area5/30/97

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Page iii of iv

CONTENTS

1. Introduction ................ 12. Sample Acquisition ............... .33. TestMethods ................ 7

3.1 Instrumentation ................ 73.2 Procedure ................ 73.3 Data Reduction ............... 73.4 Validation Tests ................ 8

4. Experimental Results .................. 114.1 Elastic Moduli and Unconfined Compressive Strengths ..................................................... 114.2 Spatial Variability ............................................................... 114.3 Failure Mode .............................................................. 204.4 ASTM Reporting Requirerments .............................................................. 20

5. Conclusions .............................................................. 236. References.................................................................................................................................25

FIGURES

Figure 1. Index map showing location of Drift Scale Test area within the ExploratoryStudies Facility ............................................................... 4

Figure 2. Locations of instrumentation boreholes used for sample collection ................................. 5Figure 3. Original locations of test specimens used for unconfined compressive tests ................... 6Figure 4. Specimen assembly showing instrumentation ............................................................... 9Figure 5. Distribution of Young's moduli for DST area characterization ...................................... 13Figure 6. Distribution of Poisson's ratios for DST area characterization ...................................... 13Figure 7. Distribution of unconfined compressive strengths for DST area

characterization............................................................................................................. 14Figure 8. View of DST area showing individual determinations of Young's moduli; is

the average Young's modulus for each borehole . ......................................................... 15Figure 9. View of DST area showing individual determinations of Poisson's ratios; v is

the average Poisson'b ratio for each jorehole . .............................................................. 16Figure 10. View of DST area showing individual determinations of unconfined

compressive strength; f is the average stress at failure for each borehole .................. 17Figure 11. Distribution of Young's modulus values for DST and SHT areas ................................ 18Figure 12. Distribution of Poisson's ratios for DST and SHT areas .............................................. 18Figure 13. Distribution of unconfined compressive strengths for DST and SHT areas ................. 19


Page iv of iv

TABLES

Table 1. List of Milestone Criteria Satisfied by this Document ...................................................... ITable 2. Borehole Nomenclature ......................................................... 3Table 3. Summary Data: Drift Scale Characterization Unconfined Compression

Tests................................................................................................................................ 12Table 4. Comparison of Mechanical Data from Single Heater and Drift Scale

Test Areas ........................................................ 19Table 5. Summary of Drillhole Mechanical Properties Data ........................................................ 19

Unconfined Compression Tests on Specimens from the Drift Scale Test Area5130/97

Page I of 26

1. IntroductionThis document contains the results of a suite of laboratory mechanical tests designed to

assist in the characterization of the Drift Scale Test (DST) area in the Thermal Testing Facility ofthe Exploratory Studies Facility (ESF) at Yucca Mountain, Nevada. Sixteen test specimens weremanufactured from core taken from four instrumentation boreholes. The specimens were testedin unconfined compression to determine unconfined compressive strength, Young's modulus, andPoisson's ratio. All specimens were taken from boreholes drilled into the Access ObservationDrift. Core from the heated drift was not available in time for inclusion in this report. The testmethods, instrumentation, data reduction procedures, and results are given in this report.

These tests were performed by Sandia National Laboratories (SNL) during March andApril of 1997. The specimens tested represent tuff specimens from the TSw2 thermal/mechanical (T/M) unit and the Tptpmn lithostratigraphic unit (Tptprnn is an abbreviation forTertiary, Paintbrush, Topopah Spring Tuff Formation, crystal poor, middle nonlithophysal unit).All data used in the preptnation of this report were collected under SNL's Quality Assurance(QA) program.

The work was performed by SNL under Yucca Mountain Project WBS number 1.2.3.14.2.The completion of this document satisfies, in part, CRWMS M&O Level 4 MilestoneSP5145M4. This document (TDIF No. 306126) and TDIF No. 306127 satisfy this milestone infull. Table 1 outlines the criteria for this milestone and shows where they are met in thisdocument.

Table 1. List of Milestone SP5 145M4 Criteria

Results of the laboratory measurements of thermal and mechanical properties will besubmitted as a level 4 deliverable SP5145M4, by 5/30/97 to be incorporated into the level 3deliverable SP3308M3, due by 8/4/97.

Criteria for SP5145M4 LocationSample preparation

Thermal conductivity TDIF No. 306127Thermal expansion TDIF No. 306127Young's modulus and Poisson's ratio Section 2.0

Thermal Conductivity Testing TDIF No. 306127Thermal Expansion Testing TDIF No. 306127Uniaxial Compression Tests (15 tests)

Young's modulus Section 4.1, Table 3Poisson's ratio Section 4.1, Table 3Uniaxial compressive strength Section 4.1, Table 3ASTM reporting requirements Section 4.4Thermal/Mechanical, lithologic units Section 4. 1, Table 3


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Page 3 of 26

2. Sample Acquisition

The location of the DST area within the ESF is shown in Figure 1, and an enlarged viewof the DST area is shown in Figure 2. Boreholes were drilled into the Access Observation Driftarea to accommodate placement of instrumentation. Material taken from these boreholes wasused to prepare specimens for both mechanical and thermal properties testing. Figure 2 shows theapproximate locations of the boreholes used for sample acquisition. Figure 3 shows an enlargedview of one section of the DST area and the approximate original locations of the mechanical testspecimens. Sampling was performed at evenly spaced intervals of 6 m as core availabilitypermitted. Table 2 shows the correlation between borehole designation (given in Figures 2 and 3and in the text of this report) and the full borehole designation.

Table 2. Borehole Nomenclature

Abbreviated HDFRI MPBX I MPBX2 MPBX3Borehole NumberBorehole ESF-AOD- ESF-SDM- ESF-SDM- ESF-SDMDesignation HDFR#1 MPBX-1 MPBX-2 MPBX-3

Mechanical test specimens were prepared according to Sandia National Laboratories(SNL) Technical Procedure SNL TP-05 1 entitled "Preparing Cylindrical Specimens IncludingInspection of Dimension and Shape Tolerances." All specimens were ground, right circularcylinders with nominal specimen dimensions of 38.1 mm diameter and 76.2 mm length. The rawcore was less than 50 mm in diameter, so the specimens used in this study were smaller thanthose used for characterization of the NRG and SD boreholes (50.8 mm).

Specimens were assigned identification numbers according to SNL Quality AssuranceImplementation Procedure (QAIP) 20-3 entitled "Sample Control." The specimen identificationnumber begins with the designation of the borehole, followed by the depth (distance from theborehole collar) of the top of the piece of core from which the specimen was prepared. Ifmultiple test specimens were prepared from a single piece of core, then the specimens weresequentially labeled A-Z.

Specimens were tested in the air dried state, i.e., in the as-received condition with noeffort made to preserve or alter the moisture content. The moisture content durinp testing wassubstantially differtiiE than in situ. After recovery from the ESF, the cores may have dtied out atthe Sample Management Facility at the Nevada Test Site. They were then machined intospecimens using water as a coolant, and then they dried out somewhat in the laboratory untiltesting. Immediately after testing, specimen fragments were collected and weighed. They weresubsequently dried using SNL TP-065, "Drying Geologic Samples to Constant Weight" todetermine moisture contents during testing.

Unconfined Compresson Tests on Specimens from the Drift Scale Test Area

5130/97Page 4 of 26

17+1

To North Portal

SI gg3

17

Ghost Dance Fault

(a) Plan View

Possible Ghost DanceFault Trace

II Jr Upper Uthophysal Zone

11 ____________________

Middle Non-Uthophysal Zone

iL Heat Main Drift

Sly Poss;y OOm 1 8Gm_50m

(b) Profile ViewReference Only(Not to Scale)

Figure . Index mapTshoMving location of Drift Scale Test arRarn wOly

Figure F.ciexmap showing location Of Drift Scale Test area within. the Exploratory Studies

Drift Scale -�


Page 5 of 26

Drift Scale-:Test Region

Heated Drift

AccessObservationDrift

ESF Norj ~mCenterline e CS 28+27 ESF Main Drift

Section a-a'

I

0o

U-Ir

R1I-852f-OI2

Figure 2. Locations of instrumentation boreholes used for sample collection.


Page 6 of 26

a

HDFR1

a' Section a-a'

8.6

I

I

Connecting Drift

i 32.2

i 48.7

I 68.8

MPBX1

i"I

w

80.5 62.0 40.8 32.1 1.C

MPBX2

84.6 71.5 48.4 29.0

MPBX3

Caco

co0Ca

0

5.

0

HDFR1

85.3 38.7 17.7

* Original Location of Test Specimens

Values correspond to specimen IDsgiven in Table 3 and are distances(in feet) from borehole collars

TR1-8117.35"

Figure 3. Original locations of test specimens used for unconfined compressive tests.


Page 7 of 26

3. Test Methods

3.1 Instrumentation

The specimen assembly is illustrated in Figure 4. The specimen was placed in a flexiblejacket to maintain constant moisture content during testing and to contain the specimen fragmentsduring failure. Ports were cut out of the jacket at the requisite locations to accommodate axialand lateral deformation gages. The axial displacement gage consisted of two Linear VariableDisplacement Transformers (LVDTs) located on opposite sides of the specimen. The LVDTbarrels were located in a ring, which was attached approximately one specimen radius from theupper end of the specimen. The LVDT cores were on extended rods that rested in cups locatedon a lower ring placed approximately one specimen radius from the lower end of the specimen.The axial displacement gage therefore measured displacements occurring over the central sectionof the specimen. Radial strains were measured across one diameter of the specimen using theradial displacement gage developed by Holcomb and McNamee (1984). This gage consists of anLVDT mounted in a ring, which is spring-loaded against the specimen. The barrel oi the LVDTis mounted in the ring, and the core of the LVDT is attached to a leaf spring that directly contactsthe specimen surface. Changes in specimen diameter directly displace the LVDT core relative tothe barrel. The accuracies of calibrations for both the axial and lateral displacement gages werewithin ±2% of reading over the verified range of 10-100% of full scale. LVDTs were calibratedwhile mounted in the rings using SNL TP-257, "LVDT Calibration at Sandia NationalLaboratories."

Tests were conducted in a servo-controlled hydraulic loading frame. The servo-controllerwas operated in strain-control feedback mode and force was applied so that a constant axial strainrate of I0 s' was imposed. The axial force was measured with a load cell calibrated in place bythe manufacturer. The calibration constant for the load cell has a standard deviation of 0.02%.

3.2 Procedure

Testing was performed in accordance with SNL TP-219, "Unconfined CompressionExperiments at Ambient Conditions and Constant Strain Rate." Specimens were inspected forsurface irregularities, vugs, and preexisting fractures. After being jacketed and instrumented,specimens were loaded at a constant strain rate of l 5 sX until peak force was reached. Data onall channels were collected whenever the output of one channel increased by a preset anolint.Data were stored if time incremented by 60 seconds, if axial stress incremented by 2 MPa, if axialstrain incremented by 3x1 0 5, or if lateral strain incremented by 2x1 0 5. Specimens wereunloaded after passing the peak in axial force.

3.3 Data Reduction

Strains were calculated by dividing the measured axial and lateral displacements by theoriginal gage separations. The axial gage consisted of two LVDTs, and the average axial strain isreported. Peak stress is the unconfined compressive strength and is obtained by dividing the peakforce by the original cross-sectional area of the specimen. The static elastic constants werecalculated by performing linear least squares fits to the data collected between 10 and 50% of the

Full scale output for the lateral gage was 0.635 mm (0.025 in) or 0.0167 strain; for the axial gage, full scale outputwas 1.27 nun (0.05 in) or 0.0333 strain.


Page 8 of 26

stress difference at failure. Young's modulus is the slope of the linear fit to the axial strain versusaxial stress data, and Poisson's ratio is the slope of the linear fit to the axial strain versus lateralstrain data.

3.4 Validation Tests

Before testing tuff specimens, validation tests were performed on 6061 aluminum tovalidate the test method. Tests were also performed midway through the testing program andafter completion of the test suite. For the pretest validation, measurements of Young's modulusand Poisson's ratio were within 9% and 15% of the expected values, respectively. Measurementsof Young's modulus and Poisson's ratio were within 2% and 8% of the expected values,respectively, for the midtest and posttest validations.


Page 9 of 26

Specimen

Axial LVDT

- Axial LVDT Barrel Support Ring

-|<RRad ial LVDT Barrel Support Ring(detilbe low)

- LVDT Core Extension Rod

- 3 * Axial LVDT Core Extension Rod Support Ring

/Radi isplacement Gauge\

T ~~~Adjusting Screw\

Deflection - Support RingSp7ring,

S r 4 LV~DT Coret o ~~~~Extension Rod /

- Radial LVDT /

TR14117494

Figure 4. Specimen assembly showing instrumentation.


Page 10 of 26

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Page II of 26

4. Experimental Results

4.1 Elastic Moduli and Unconfined Compressive Strengths

Sixteen specimens were tested in unconfined compression; the experimental data aresummarized in Table 3. Mean values, standard deviations, and 95% confidence limits are givenin Table 3 for Young's modulus, Poisson's ratio, unconfined compressive strength, and axialstrain at peak stress. One specimen, MPBX 1-1.0-A (test UCDSTOO 1), was unloaded after forcebegan to drop at approximately 53 MPa. The specimen was later reloaded (test UCDST017) to apeak stress of 179 MPa. Data from the first loading of this specimen were used to calculate themean elastic moduli in order to be consistent with the other tests. Data from the second loadingwere used in calculations of mean unconfined compressive strength and mean axial strain at peakstress. Stress-strain curves for all tests are given in Appendix A.

The distribution of Young's moduli is given in Figure 5. Young's moduli ranged from28.9 GPa to 43.1 GPa, with a mean value of 36.8 GPa. The standard deviation was ±3.5 GPa andthe 95% confidence limit was ±1.7 GPa. The high Young's modulus value (43.1 GPa) correspondsto the first loading of MPBX1-1.0-A. Because this specimen was unloaded at a low stressdifference, the modulus was calculated over a lower stress range than for the other specimens.

The distribution of Poisson's ratios is given in Figure 6. Poisson's ratio ranged from 0.17to 0.34, with a mean value of 0.20. The standard deviation was *0.04 and the 95% confidencelimit was ±0.02. The three specimens with the highest Poisson's ratios (0.34 corresponding toHDFRI-32.2-A, 0.22 corresponding to MPBXl-80.5-A, and 0.22 corresponding to MPBX3-38.7)were the only specimens that had preexisting open fractures.

The distribution of unconfined compressive strength values is given in Figure 7. Strengthranged from 71 MPa to 324 MPa with a mean value of 176 MPa. The standard deviation was±66 MPa and the 95% confidence limit was :32 MPa. The highest and lowest strengths wereobtained on specimens from MPBX2 that were in relatively close proximity (4 m apart.) Neitherspecimen had notable surface features that might indicate anomalous behavior.

The data shown in Figure 7 appear to be symmetrically distributed about the mean. Noanalyses were performed to determine the best fitting distribution curves for Young's modulus,Poisson's ratio, or unconfined compressive strength.

4.2 Spatial Variability

Individual determinations of Young's moduli, Poisson's ratios, and unconfinedcompressive strengths are shown in Figures 8, 9, and 10, respectively, plotted at the locations ofthe original test specimens. The mean values for each borehole are also shown. Because the dataare very variable and there are very few tests per borehole, caution must be exercised whencomparing boreholes. Bearing this in mind, note that the mean Young's modulus for eachborehole decreases with increasing distance from the connecting drift. Although the meanunconfined compressive strength systematically increases with distance from the connecting drift,the standard deviations associated with strength data for each borehole are extremely large. Thehighest strength values were obtained close to the heated drift. The Young's modulus data maybe indicative of some spatial variability within Alcove 5. No systematic variation in Poisson'sratio is indicated. Data from HDFRI show no systematic changes in properties with depth.There are insufficient data to assess anisotropy.

Table 3. Summary Data: Drift Scale Characterization Unconfined Compression Tests

Test ID UCDSTWOI UCDST002 UCDST003 UCDSTO4 UCDST005 UCDST006 UCDST007 UCDSTOO8 UCDSToo9 UCDSTOIO UCDSTO I

Specimen ID ESF-SDM- ESF-SDM- ESF-SDM- ESP-SDM ESF-SDM- ESF-SDM- ESP-SDM- ESF-SDM- ESF-SDM- ESP-AOD- ESF-AOD-MPBXI- MPBXI- MPUXI- MPBXI- MPBXI- MPBX2- MPBX2- MPBX2- MPBX2- HDFRI- HDPRI-

1.0-A 32.1-A 40.6-A 62.0-A 80.5-A 29.0-A 48.4-A 71.5-A 84.6-A 8.6-A 32.2-ADate Tested 3/28197 3/28/97 3/31/97 3/31/97 3/31/97 3/31/97 3/31/97 3/31/97 4/1/97 4/1/97 4/1/97

Thennal/Mechanical Unit TSw2 TSw2 TSw2 TSw2 TSw2 TSw2 TSw2 TSw2 TSw2 TSw2 TSw2

Lithostratigraphic Unit Tptpmn Tptpn Tptpmn Tptpmn Tptpmn Tptpmn Tpy.,mn Tptpmn Tptpmn Tptpmn TptpmnDry Bulk Density 2.27 2.26 2.27 2.27 2.30 2.26 2.23 2.30 2.31 2.28 2.28

Moisture Content (%) 0.48 0.51 0.60 0.81 0.61 0.45 0.53 0.49 0.56 0.67 0.32Confining Pressure 0 0 0 0 0 0 0 0 0 0 0

Static Young's Modulus (GPa) 43.1 38.5 38.2 39.3 36.2 37.8 34.5 40.2 37.8 37.4 34.5Static Poisson's Ratio 0.18 0.21 0.19 0.19 0.22 0.20 0.19 0.17 0.19 0.20 0.34Unconfined Compressive 52.7 201.0 232.6 114.1 97.2 178.0 128.n 71.3 324.1 268.3 123.1Strength (MPa) IAxial Strain at Peak Stress 0.001267 0.005642 0.006191 0.003016 0003577 0.005467 0.003877 .001852 0.009506 0.007966 0.003497

- - - - - - -

Test ID UCDST0I 'B2 DSTI UCDST1I UCDST1I UCDST1I UCDST0I Sasc Summary2 3 4 5 6 7

ReloadingSpecimen ID ESF-AOD- SF-AOD- ESP-SDM- ESF-SDM ESF-SDM- ESF-SDM- Mean Standard Count 95%

HDFRI- HDFRI- MPBX3- MPBX3- MPBX3- MPBXI- Deviation Confidence48.7-A 68.8-A 17.7-A 38.7-A 85.3-A 1.0-A | Limit

Date Tested 4/1/97 4/1/97 4/1/97 4/2/97 4/2/97 4/1/97ThermaU/Mechanical Unit TSw2 TSw2 TSw2 TSw2 TSw2 TSw2Uthostratigraphic Unit Tptpmn Tptpmn Tptpmn Tptpmn Tptpmn TpzpmnDry Bulk Density 2.28 2.24 2.24 2.29 2.26 2.27Moisture Content (%) 0.46 0.83 0.74 0.42 0.48 0.48ConfiningPressure 0 0 0 0 0 0 Static Youngs Modulus (GPa) 40.0 31.6 28.9 34.8 35.4 38 36.8 3.5 16 1.7

Static Poisson's Ratio 0.19 0.17 0.18 0.22 0.18 2.06 0.201 0.040 16 0.020Unconfined Compressive 175.6 159.0 172.2 158.6 239.1 179.4 176.4 68 16 32.3Strcngth (MPa) I -

Axial Strain at Peak Stress 0.003668 QOO.5536 0.006551 0.007332 0.006082 0.003582 0.005209 0.002048 16 0.001004

Test Conditions: Nominally 38.1 mmin diameer, 76.2mm in n.ibent temperature and piessur nominal strain rate of IWos f.(a) Test specimen ESF-SDM-MPBXI-.0-A was tested twice. Mean Young's modulus and mean Poisson's ratio were calculated using data from the first loading only (UCDST0O). Meanunconfined compressive strengths was calculated using data frm the second loading only (UCDST017).

C

0

a

0(A

0

0

0

0

U2

I

(A~

90

9'-4~

7~~~~~,.

Unconfined Compression Tests on Specimens from the Drift Scale Test Area^s 4 5/30197

Page 13 of 26

3

.0

Mean Youns Modulus =t

36.8 3.5 GPaJ.

21

E

V f I -

028-29 30-31 32-33 34-35 36-37 38-39 40-41 42-43

Young's Modulus (GPa)

Figure 5. Distribution of Young's moduli for DST area characterization.

6

Mean Poisson's Ratio= 0.20 0.04

Cn 4

0I-I

EZ 2

0 J MI I III I I I

0.15-0.16 0.17-0.18 0.19-0.20 021-0.22 023-024 025-026 027-028 029-0.30 0.31-0.32 0.33-0.34

Poisson's Ratio

Figure 6. Distribution of Poisson's ratios for DST area characterization.


Page 14 of 26

3

Mean Value of UnconfinedCompressPe Strength 176 ±66 MPa

4-2

U)C-

EZ

0-50- 75- 100- 125- 150- 175- 200- 225- 250- 275- 300-75 100 125 150 175 200 225 250 275 300 325

Peak Stress (MPa)

Figure 7. Distribution of unconfined compressive strengths for DST area characterization.

The data obtained in this study are compared with data obtained during characterization ofthe Single Heater Test (SHT) region (TDIF # 305602) in Table 4 and in Figures 11, 12, and 13.Mean values of Young's modulus, Poisson's ratio, and compressive strength are all higher for theDST data set. Minor differences in the testing programs should be discussed. The SHT testspecimens had a length to diameter (L:D) ratio of 2.5 whereas the DST test specimens had an L:Dratio of 2.0. Work reported in Paterson (1978) indicates that a 3% increase in unconfinedcompressive strength resulted from decreasing the L:D from 2.5 to 2.0 in Westerly granite. Thesame strength-versus-L:D relationship is not necessarily expected in tuff, but the work reported inPaterson (1978) is cited to prn-ide an indication of the magnitude of the effect. The increase inobserved strengths is approximately 21%, so the effect of different L:D ratios is consideredminor. Differences in results of validation tests on aluminum could account for approximately a4-8% difference in Poisson's ratio. Moisture contents for DST specimens were all less than 1%.Two of the SHT specimens were saturated and the remainder were tested "as is," similar to theDST tests.

The differences in properties between the DST and SHT, and a possible systematic changein Young's modulus with increasing distance from the connecting drift as shown by the DSTdata, may be indicative of spatial variability within Alcove 5.

For comparison, drillhole data are summarized in Table 5 (DOE, 1996). Compared to thedrillhole data, Young's moduli for the DST area appear high, while Poisson's ratios andunconfined compressive strengths for the SHT area appear low.

Unconfined Compression Tests on Specimens from the Drift Scale Test Area5130197

Page 15 of 26

a a' Section a-a'

U0 _HDFR1

37.4Connecting Drift

34.5

40.0

31.6

MPBX1 = (39.1 f 2.5) GPa0

36.2 39.3 38.2 38.5 43.1 3

5 ~~HDFR1:EMPBX2: E (37.6 * 2.3) GPa o H D F R 1 GE

I 37.8 40.2 34.5 37.8

MPBX3; = (33.0 * 3.6) GPa

35A 3.8 28.9

Original Location of Test Specimens(values are in units of GPa)

1R141738.

Figure 8. View of DST area showing individual determinations of Young's moduli; S is theaverage Young's modulus for each borehole.


Page 16 of 26

as

- 0 -HDFR1

Section a-a'

0.20

I

I

Connecting Drift

0.34

0.19

0.17

aa

co

MPBX1: V = (0.20 t 0.02)

0.22 0.19 0.19 0.21 0.18

MPBX2:V = (0.19 0.01)

0.19 0.17 019 0.20

MPBX3: V= (0.19 * 0.03)

CI)0

CD

0

HDFR1: v =(0.22 ± 0.08)

I0.18 0.22 0.18

* Oniginal Location of Test Specimens(vakues are unitless)

TRI-17-37-0

Figure 9. View of DST area showing individual determinations of Poisson's ratios; v is theaverage Poisson's ratio for each borehole.


Page 17 of 26

a' Section a-a'

0)_ O _HDFRI

__ Connecting Drift268

123

176

0raa,,

MPBX1: a = (165:t 80) MPa

97 114 233 201 179

MPBX2: af = (175*t 108) MPa

324 71 128 178

MPBX3: bt = (190*: 43) MPa

239 159 172

oco00*

0,

a,

159

HDFR1: Af =(182 * 62) MPa

* Original Location of Test Specimens(values are In units of MPa)

TRI4117-38

Figure 10. View of DST area showing individual determinations of unconfined compressivestrength; of is the average stress at failure for each borehole.


Page 18 of 26

4 .

l

*DST: Mean = 36.8 ±3.5 GPa

3SHT: Mean = 32.4 ±2.9 GPa

3

u)4-

w

w0

Ez

2

4

i

i

i

I

i

I

I

i

i

I

II - .

. I

I -

1

n R~~~~~~~ 1~25-26 27-28 29-30 31-32 33-34 35-36 37-38 39-40 41-42

Young's Modulus (GPa)

Figure 11. Distribution of Young's modulus values for DST and SHT areas.

43-44

8

6

* DST: Mean = 0.20 ±0.04

| SHT: Mean- 0.17±tO.02

u)

w-0

(DI-

Ez

4

2

IO I 6 i I i i I i I I -

0.15-0.16 0.17-0.18 0.19-020 021-0.22 023-024 025-026 027-0.28 029-0.30 0.31-0.32 0.33-0.34

Poisson's Ratio

Figure 12. Distribution of Poisson's ratios for DST and SHT areas.


Page 19 of 26

l

I DST: Mean = 176 ±66 MPaI1SHT: Mean = 143 *50 MPaI

qa

Ez

l

80 7 TO. T& UOF - 17- 200e 225- 250- 27 - 300.75 D0 T5 to 15 200 225 250 275 300 325

Peak Stress (MPa)

Figure 13. Distribution of unconfined compressive strengths for DST and SHT areas.

Table 4. Comparison of Mechanical Data from Single Heater and Drift Scale Test Areas

Test Region Young's Modulus (GPa) Poisson's Ratio Unconfined CompressiveS A&gth (MPa)

Mean Standard No. of Mean Standard No. of Mean Standard No. ofDeviation Tests Deviation Tests Deviation Tests

SHT 32.4 2.9 22 0.17 0.02 22 1432 50.3 22DST 36.8 3.5 16 0.20 0.04 16 176.4 65.8 16Difference 13% 16% __ 21% _ _ _

Table 5. Summary of Drillhole Mechanical Properties Data for Tptpmn

Drillhole Young's Modulus (GPa) Poisson's Ratio Unconfined CompressiveStreogth _pla)

Mean Standard No. of Mean Standard No. of Mean Standard No. ofI Deviation Tests Deviation Tests Deviation Tests

NRG-5 32.5 10.8 8 0.20 0.06 8 173.3 99.4 8NRG-6 32.1 3.0 8 0.19 0.03 8 193.0 55.7 8NRG-7/7A 33.2 4.2 19 0.22 0.03 19 192.1 51.1 9SD-9 32.8 5.1 15 0.21 0.02 15 189.1 64.8 7SD-12 34.3 2.0 4 0.20 0.01 4 195.8 3.5 2All Drillholes 32.9 5.5 54 0.21 0.03 54 187.5 64.9 34


Page 20 of 26

4.3 Failure Mode

All specimens failed audibly except for MPBX 1-1.0-A, which was loaded twice. Mostrocks failed explosively. A qualitative assessment was made concerning the failure mode of eachspecimen. Specimens were categorized as having failed either by axial splitting, development ofshear planes, or "other" mode. This last category included rocks that were difficult to categorizeor appeared to have failed by a combination of both axial splitting and shear. This qualitativeassessment showed that the four rocks with the highest compressive strengths (tests UCDST003,009, 010, and 016) all failed by axial splitting. Three additional rocks also failed by axialsplitting, including UCDST006, 011, and 013. These three specimens had average to belowaverage strengths. The three specimens that failed along shear planes (UCDST002, 007, and 008)had above average, below average, and well below average strengths, respectively. The datasuggested a possible weak correlation between failure mode and unconfined compressive stress,so a correlation calculation was performed. Failure modes were assigned numerical values.Axial splitting was assigned a '1,' other modes or mixed modes were assigned a '2,' and failurealong shear planes was assigned a '3.' The correlation coefficient (r2 ) was then calcuiaed forpeak stress versus failure mode. The correlation coefficient obtained was 0.30, implying that30% of the variance in peak stress values could be attributed to failure mode. For the similarsuite of unconfined compressive tests conducted on specimens from the SHT area (TDIF #305602), it was reported that no correlation existed between strength and the mode of failure.This data set is consistent with the earlier conclusion (although the data analysis is documentedmore completely) that there does not appear to be a significant correlation between the failuremode and the peak stress values.

4.4 ASTM Reporting Requirements

Two ASTM standards are applicable to this work. They include ASTM D2938-86,"Standard Test Method for Unconfined Compressive Strength of Intact Rock Core Specimens,"and ASTM D3148-93, "Test Method for Elastic Moduli of Intact Rock Core Specimens inUniaxial Compression." The reporting requirements of ASTM D2938-86 are addressed asfollows:

1. Source of sample including project name and location, and, if known, storage environment.The location is frequently specified in terms of the borehole number and depth of specimenfrom the collar of hole: This information is given in Section 2.0.

2. Physical description of the sample including rock type; location and orientation of apparentweakness planes, bedding planes, and schistosity; large inclusions or inhomogeneities, ifany: A description of each specimen was prepared before testing. The description includesrock type, dimensions, color, vugs, irregularities, fractures, large inclusions orinhomogeneities, and direction of inclusion elongation. The descriptions are included in therecords package'. Relevant information from the descriptions was included in the discussionof results. All specimens were from the TSw2 thermal/ mechanical unit and the Tptpmnlithostratigraphic unit.

'The test records are available through the Sandia National Laboratories Participant Data Archive under thefollowing data set identification number: 5 11L02-100196.


Page 21 of 26

3. Date of sampling and testing. The instrumentation boreholes were drilled during Augustand September of 1996. Specimens were prepared during January and February of 1997.Test dates are given in Table 3.

4. Specimen diameter and length, conformance with dimensional requirements: Nominaldimensions are given in this report: Complete inspection reports that include length,diameter, straightness, flatness, parallelism, and perpendicularity are given in the testrecords. Specimens conform to the L:D requirements given in the ASTM standard. Thespecimen diameter was constrained by the diameter of the recovered core.

5. Rate of loading or deformation rate: All tests to failure were conducted at I0 5s-l. Allspecimens failed within the ASTM guideline of 5 to 15 minutes except for MPBX2-84.6-A,which failed within 16 minutes.

6. General indication of moisture condition of sample at time of test such as as-received,saturated, laboratory air dry, or oven dry. It is recommended that the moisture condition bemore precisely determined when possible and reported as either water content or degree ofsaturation: Water contents are given in Table 3.

7. Unconfined compressive strength for each specimen and calculated average unconfinedcompressive strength of all specimens tested, standard deviation or coefficient of variation.These data are given in Table 3.

8. Type and location offailure. A sketch of the fractured sample is recommended: Allspecimens were photographed after testing and the photographs are included in the testrecords. Relevant information was discussed in Section 4.3.

9. Other available physical data: Stress-strain curves are given in Appendix A for allspecimens. Pretest and posttest mass measurements are given in the test records.

The reporting requirements of ASTM D3 148-93 are addressed as follows:

1. Source of sample including project name and location (the location is frequently specified interms of the drillhole number and depth of specimen from the collar of hole: See Section2.0 and Table 3.

2. Lithologic description of the rock, formation name, and load direction with respect tolithology: See item 2 above.

3. Moisture condition of sperimen before testing. See item 6 above.

4. Specimen diameter and height, conformance with dimensional requirements: See item 4above.

5. Temperature at which test was performed. All tests were performed at room temperature.

6. Rate of loading or deformation rate. See item 5 above.

7. Plot of the stress-versus-strain curves. These are given in Appendix A.

8. Young's modulus, E, method of determination, and at what stress level or levels determined.Young's modulus is given in Table 3. The calculation method is given in Section 3.3.

9. Poisson's ratio, v, method of determination, and at what stress level or levels determined.Poisson's ratios are given in Table 3. The calculation method is given in Section 3.3.


Page 22 of 26

10. A description of the physical appearance of specimen after test, including visible end effectssuch as cracking, spalling, or shearing at the platen-specimen interfaces. See item 8 above.There were no indications of significant end effects.

11. If the actual equipment or procedure has variedfrom the requirements contained in this testmethod, each variation and the reasons for it shall be discussed. The standard recommendsthat one platen be spherically seated. The testing machine alignment is sufficient such that aspherical seat is not necessary.


Page 23 of 26

5. ConclusionsTest specimens were prepared from core recovered from instrumentation boreholes in the

DST area. Unconfined compression tests were performed to determine Young's modulus,Poisson's ratio, and unconfined compressive strength. Mean Young's modulus was 36.8 ±3.5GPa, mean Poisson's ratio was 0.20 ±0.04, and mean compressive strength was 176.4 ±65.8 MPa.The error bars represent plus or minus one standard deviation. Mean values of Young's modulusand compressive strength for each borehole show a possible systematic change with distance fromthe connecting drift. Mean values of Young's modulus, Poisson's ratio, and strength are allhigher than values obtained during characterization of the SHT area. Coefficients of thermalexpansion were also somewhat higher for the DST than for the SHT (TDIF # 306127) Thevariations in strength and modulus within the DST, and differences in all measured propertiesbetween the SHT and DST areas, may be indicative of spatial variability within Alcove 5.Young's modulus is used to translate thermal strains into stresses. Insufficient characterization ofspatial variability in Young's modulus will affect calculations of stresses as the temperature of theDST area increases.

Further work that will clarify some of the issues raised here includes the following:

1. If regional differences are significant to design calculations, then lateral variability should beevaluated throughout the ESF. In general, mechanical properties data from Yucca Mountainare highly variable, even for specimens in close proximity. For this suite of 16 tests, thestandard deviation and 95% confidence limit associated with Young's modulus are 10% and5% of the mean, respectively. For Poisson's ratio, the standard deviation and 95%confidence limit are 20% and 10% of the mean, respectively, and for unconfinedcompressive strength they are 37% and 18% of the mean, respectively. The large scatterimplies that large numbers of tests (10-20) may be required to adequately characterizeregions.

2. The anisotropy of elastic and failure characteristics should be assessed by testing orthogonalspecimens (at controlled moisture contents) cored adjacent to one another.

3. Failure strengths under unconfined conditions depend on time (strain rate), temperature, andmoisture content. Only sparse data exist pertaining to time-dependent properties ofrepository horizon rocks, especially at elevated temperatures. Short term and some longerterm creep tests can be used to map out time to failure as a function of differential stress.


Page 24 of 26



Page 25 of 26

6. References

ASTM. 1986. Standard Test Method for Unconfined Compressive Strength of Intact Rock CoreSpecimens. ASTM D2938-86. West Conshohocken, PA: American Society for Testingand Materials.

ASTM. 1995. Standard Test Methodfor Elastic Moduli of Intact Rock Core Specimens inUniaxial Compression. ASTM D3148-95. West Conshohocken, PA: American Societyfor Testing and Materials.

DOE (US Department of Energy). 1996. "Civilian Radioactive Waste Management SystemManagement and Operating Contractor." Yucca Mountain Site Geotechnical ReportBAAAOOOOO-01717-4600-00065 REV 00. Las Vegas, NV: US DOE.

Holcomb, DJ., and MJ. McNamee. 1984. Displacement Gage for the Rock MechanicsLaboratory. SAND84-0651. Albuquerque, NM: Sandia National Laboratories.

Paterson, M.S. 1978. Experimental Rock Deformation-The Brittle Field. Berlin HeidelbergNew York: Springer-Verlag.

TDIF # 305602. 1996. Data Tracking Number (DTN) SNL22080196001.002. "UnconfinedCompression Tests on Specimens from the Single Heater Test Area in the Thermal TestingFacility at Yucca Mountain, Nevada."

TDIF #306127. 1997. DTN SNL22100196001.001. "Thermal Expansion and ThermalConductivity of Test Specimens from the Drift Scale Test Area of the Exploratory StudiesFacility at Yucca Mountain, Nevada."


Page 26 of 26



Page A-I of A-12

Appendix AStress-Strain Diagrams


Page A-2 of A-12

Note:

Some of the plots in Appendix A show inconsistent strain data at or near peak stress (e.g.,MPBX 1-40.6-A). Once the specimen begins to fail, the contact points for the axial and lateralstrain gages may become unstable, causing this apparent noise in the stress-strain curve.


Page A-3 of A- 12

60

50

_ 40

> 30co

20

10

o

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Millistrain

Figure A-1.

250

200

0L 150

aa)U) 10

50

0

Stress-strain curves for test UCDSTOO1 on specimen ESF-SDM-MPBX 1-1.0-A.Specimen is from TSw2 thermal/mechanical unit and Tptpmn lithostratigraphic unit.

-10 -8 -6 -4 -2 0 2 4 6

Millistrain

Figure A-2. Stress-strain curves for test UCDST002 on specimen ESF-SDM-MPBX1-32.1-A.Specimen is from TSw2 thermal/mechanical unit and Tptpmn lithostratigraphic unit.


Page A-4 of A- 12

250

200

ci01..

150

100

50

0-6 -4 -2 0 2 4 6

Millistain

8

Figure A-3.

120

100

Stress-strain curves for test UCDST003 on specimen ESF-SDM-MPBX1-40.6-A.Specimen is from TSw2 thermal/mechanical unit and Tptpmn lithostratigraphic unit.

co)

a-

Cl)co

80

60

40

20

0

-1 -1 0 1 1 2 2 3 3 4Millistrain

Figure A-4. Stress-strain curves for test UCDST004 on specimen ESF-SDM-MPBX 1-62.0-A.Specimen is from TSw2 thermal/mechanical unit and Tptpmn lithostratigraphic unit.


Page A-S of A-12

100

90

80

70

CD

a

Cn

60

50

40

30

20

10

0-1 0 1 2 3

Millistrain

4

Figure A-5.

180

160

140

120co

E 1000)

Wo 80

60

40

20

0

Stress-strain curves for test UCDST005 on specimen ESF-SDM-MPBX 1-80.5-A.Specimen is from TSw2 thermal/mechanical unit and Tptpmn lithostratigraphic unit.

-15 -10 -5 0 5

Millistrain

10



Page A-6 of A-12

140

120

100

co

w12.CD

80

60

40

20

0-15 -10 -5 0 5

Millistrain

Figure A-7.

80

70

60

' 50

ax40-.

ctO30

20

1020

Stress-strain curves for test UCDST007 on specimen ESF-SDM-MPBX2-48.4-A.Specimen is from TSw2 thermal/mechanical unit and Tptpmn lithostratigraphic unit.

4 -3 -2 -1 0 1 2 3

Millistrain

Figure A-8. Stress-strain curves for test UCDST008 on specimen ESF-SDM-MPBX2-7 1.5-A.Specimen is from TSw2 thermal/mechanical unit and Tptpmn lithostratigraphic unit.


Page A-7 of A-12

350

300

250

toAL 200

aw

2 150

100

50

0-10 -5 0 5

Millistrain

10

Figure A-9.

300

250

200

X) 150en

100

50

0

Stress-strain curves for test UCDSTOO9 on specimen ESF-SDM-MPBX2-84.6-A.Specimen is from TSw2 thermal/mechanical unit and Tptpmn lithostratigraphic unit.

-20 -10 0 10 20 30 40

Millistrain

Figure A-10. Stress-strain curves for test UCDSTO10 on specimen ESF-AOD-HDFR1-8.6-A.Specimen is from TSw2 thermal/mechanical unit and Tptpmn lithostratigraphic unit.


Page A-8 of A-12

140

120

100

CDco2

CD

80

60

40

20

0-20 -15 -10 -5 0 5 10

Millistrain

15

Figure A- 1.

180

160

140

120

7- 1000' 80

60

40

20

0

Stress-strain curves for test UCDSTO1 1 on specimen ESF-AOD-HDFRI-32.2-A.Specimen is from TSw2 thermal/mechanical unit and Tptpmn lithostratigraphic unit.

-20 -15 -10 -5 0 5

Millistrain

10

Figure A-12. Stress-strain curves for test UCDSTO12 on specimen ESF-AOD-HDFRI-48.7-A.Specimen is from TSw2 thermal/mechanical unit and Tptpmn lithostratigraphic unit.

Unconined Compression Tests on Specimens from the Drift Scale Test Area5/30/97

Page A-9 of A-12

160

140

120

100

80

60

a-

u,

am2CD

40

20

0-2 0 2 4 6 8

Millistrain

Figure A-13. Stress-strain curves for test UCDSTO13 on specimen ESF-AOD-HDFR 1-68.8-A.Specimen is from TSw2 thermal/mechanical unit and Tptpmn lithostratigraphic unit.

180

160

140

co

(L

we

i

120

100

80

60

40

20

0-4 -2 0 2 4 6

Miffistrain

8



Page A-I0 of A-12

160

140

120

o

C)0)1..

100

80

60

40

20

0-20 -15 -10 -5 0 5 10

Millistrain


250

200

a 150

0

50

-20 -15 -10 -5 0 5

Millistrain

10

Figure A-16. Stress-strain curves for test UCDSTO16 on specimen ESF-SDM-MPBX3-85.3-A.Specimen is from TSw2 thermal/mechanical unit and Tptpmn lithostratigraphic unit.


Page A-IlI of A-12

180

160

140

120

2 1000

D 80

60

40

20

0-20 -15 -10 -5 0 5

Millistrain

Figure A-17. Stress-strain curves for test UCDSTO17 on specimen ESF-SDM-MPBXI-I.0-A.Specimen is from TSw2 thermal/mechanical unit and Tptpmn lithostratigraphic unit.


Page A-12 of A-12


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