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24 SMA Confined Confining Stress, +2% Dense Confined Dense Unconfined Dwell, +0.01 sec Contact Stress, +2% Axial Stress, + 2% -Teflon / +Latex - Milled / +Sawed -Water / +Air Time, min Temperature, +0.5 C -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 Change in Permanent Strain, % Figure 15. Effect of statistically significant ruggedness factors on the permanent strain after 2,000 load cycles. The specimen end condition also has a major effect on the significant ruggedness factors, Table 30 presents the effect measured permanent strains in the dense-graded mixture, of the factor on the flow number and the measured perma- but not the SMA mixture. Dense-graded specimens with milled nent strains after 2,000 load cycles. Table 30 also presents ends had consistently higher permanent strains. Apparently, acceptable values based on anticipated test variability. The the smooth, milled ends of dense-graded mixture further following conclusions were drawn for each of the rugged- reduced end friction resulting in an increase in permanent ness factors: deformation. Because end milling is time consuming sawed ends meeting the specimen end condition requirements in 1. Equilibrium temperature. The current temperature the Equipment Specification for the Simple Performance Test control of 0.5C in the SPT is acceptable. Temperature System should be used. changes over this level are expected to result in less than a 7 percent change in the flow number and less than a 5 percent 2.3.3 Summary change in the permanent strain. Table 30 summarizes the results of the analysis of the 2. Transfer time. The transfer time over the range of ruggedness test data for the flow number test. For statistically 3 to 5 min was found to be a significant factor only for the SMA Confined Confining Stress, +2% Dense Confined Dense Unconfined Dwell, +0.01 sec Contact Stress, +2% Axial Stress, + 2% -Teflon / +Latex - Milled / +Sawed -W ater / +Air Time, min Temperature, +0.5 C -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 Change in Permanent Strain, % Figure 16. Effect of statistically significant ruggedness factors on the permanent strain after 5,000 load cycles.

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25 SMA Confined Confining Stress, +2% Dense Confined Dense Unconfined Dwell, +0.01 sec Contact Stress, +2% Axial Stress, + 2% -Teflon / +Latex - Milled / +Sawed -Water / +Air Time, min Temperature, +0.5 C -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 Change in Permanent Strain, % Figure 17. Effect of statistically significant ruggedness factors on the permanent strain after 8,000 load cycles. permanent strains in the confined tests. Increasing transfer 4. End condition. The method of preparing the specimen time to 5 minutes is expected to result in no change to the ends had a major effect on the permanent strain measured in flow number and less than a 4 percent change in the meas- both unconfined and confined tests. Milled ends resulted in ured permanent strain. Based on an acceptable range of larger permanent deformations for the dense-graded mixture 7 percent which is one-half of the coefficient of variation probably because end friction was less with the smoother of the flow number test, the transfer time can be increased milled end. Because end milling is time consuming sawed to 5 min. ends meeting the specimen end condition requirements in the Equipment Specification for the Simple Performance Test 3. Conditioning fluid. The use of water as a condition- System should be used. ing fluid can result in moisture damage in the specimen during repeated loading if sufficient water penetrates the specimen. 5. Friction reducer. Of all the factors included in the Air should, therefore, be used as the conditioning fluid. If the ruggedness testing, the end friction reducer had the greatest specimens are to be conditioned in a water bath, they should effect on the flow number and the measured permanent de- be sealed in plastic to keep the water from penetrating the formation. Flow numbers were much lower and permanent de- specimen. formation much higher when the greased latex friction reducer Table 30. Summary of the effect of ruggedness test factors on the flow number and permanent strain. Unconfined Confined Flow p, 2000 Flow p, 2000 Factors Control Number cycles Number cycles Equilibrium 0.5 C <7% <5% NF < 2% Temperature Transfer time 3 versus 5 min NS NS NF < 4% Conditioning Fluid Air versus Water NS < 24 % NF NS End Condition Milled versus NS < 14 % NF < 15 % Sawed Friction Reducer Greased Latex < 20 % < 24 % NF < 25 % versus Teflon Axial Stress 2% NS NS NF < 1% Contact Stress 2% NS NS NA NA Dwell 0.01 sec NS NS NA NA Confinement 2% NA NA NF <3% Acceptable 10 % 7% 10 % 7% NA = not included NF = no flow detected NS = not statistically significant

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26 was used. Flexibility can not be permitted in the selection of the had no significant effect on the flow number or the measured end friction reducer. Since the greased latex membranes pro- permanent strains. vide less friction and were specified in Project 9-19, these fric- tion reducers should be used in the flow number testing. 8. Dwell time. Data from the flow number test was not affected by a range in dwell time of 0.1 sec. The computer 6. Axial stress. The axial stress control of 2 percent in control used in the SPT is capable of controlling the dwell the SPT is acceptable. Stress variations over this level are ex- time much more precisely at this level. pected to result in no change in the flow number and less than a 1 percent change in the permanent strain. 9. Confinement. The current confining pressure control of 2 percent is acceptable in confined tests. Over this range 7. Contact stress. The contact stress control of 2 per- of control, the permanent strain is expected to vary by less cent in the SPT is acceptable. Stress variations over this level than 3 percent.