POP-cement mix

Figure 4. POP-cement mix specimens with marks representing the position of joints...

POP-cement mix samples is shown in Figure 5 and Figure 6, respectively. 

The d5mamic modulus of elasticity of POP and POP-cementmixsamples was found by determination of seismic velocity of samples, viz. P-wave velocity and S-wave velocity. The values of Vp, and dynamic modulus of elasticity for both POP and POP-cement mix samples are given in... 

With the help of these equations the uniaxial compressive strength/elastic modulus of jointed rocks can be determined for known values ofjoint factor and uniaxial compressive strength/elastic modulus of intact rock. It is observed that the ratios of both static and dynamic elastic modulus decreases with an increase inthe jointfactorunder unconfinement. The test results of POP and the POP-cement mix specimens are given in Table 5. Figure 14 shows the experimental values of uniaxial compressive strength ratio versus joint factor along with a fitted curve. 

Figure 17. UCS ratio versus joint factor for combined data of POP and POP-cement mix specimens...

The influence of joints on static and dynamic elastic modulus was investigated based on the data provided in Table 4 and Table 5. Regression analysis was done for the data on ratios of static and dynamic elastic modulus of plaster of Paris (POP) specimen. Plaster of Paris-cement mix specimen and mixed data of plaster of Paris and Plaster of Paris-cement mix specimen. The curves were plotted for the ratio of static elastic modulus and dynamic elastic modulus for all the three groups of data. The plotted curves are shown in Figure 24 to Figure 26. Figure 24 shows the experimental values of ratio of static elastic modulus versus ratio of dynamic elastic modulus for POP specimens. Figure 25 shows the trend of ratio of static elastic modulus versus ratio of dynamic elastic modulus for POP-cement mix specimens. The plot of ratio of static elastic modulus versus ratio of dynamic... 

Figure 25. Ratio of static elastic modulus versus ratio ofdynamic elastic modulus for POP-cement mix...

It is clear from the analysis shown in Figure 25, Figure 26 and Figure 27 that the trends of ratio of static elastic modulus versus ratio of dynamic elastic modulus for POP specimens and POP-cement mix specimen are always below the line of comparison. This indicates that the anisotropy of the specimen is influencing the dynamic elastic modulus more than the static elastic modulus. The low strain experiments on the POP and POP-cement mix models also indicate that the effect of joints is more predominant for the sample material of higher strength than the lower strength material. 

The low strain experiments on the POP and POP-cement mix models also indicate that the effect of joints is more predominant for the sample material of higher strength than the lower strength material. 

POP mixed with 10% Portland cement by weight was also used to prepare cylindrical specimens to have relatively higher uniaxial compressive strength and to represent higher wall strength, in case of jointed specimens. A total of 110 gm mixture was taken containing 11 gm Portland cement and was thoroughly dry mixed with a stirrer. This POP with cement mix was then mixed with specific quantity of water (always kept constant for every sample) to cast cylindrical specimens with split moulds similar to POP without cement mix specimens. These specimens of POP with ce-... 

In all the cases, with increase in the joint frequency, there is a decrease in the strength. Figure 13 shows the failed cylindrical specimens of POP with different number joints at 90 inclination, after the test. As can be seen, mostly horizontal cracks were formed similar to the POP specimen without cement mix, but with a more pronounced brittle nature due to the addition of cement. In... 

Figure 10. Stress-strain curves for POP with cement mix specimen with different number of joints at 90° joint inclination tested...

Figure 13. Failed cylindrical specimens of POP with cement mix...

Table 5. Calculatedjoint factor values with corresponding uniaxial compressive strength ratio for POP with cement mix specimens...

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