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Jan 11 As seen in Table 1 igneous metamorphic and sedimentary rocks can be compressive strength observed in a rock is on the order of 400 MPa

Table 4 Results of the uniaxial compression test Location Rock type Compressive strength MPa Standard deviation Coefficient of variation Pozanti

Table 1 Field estimates of uniaxial compressive strength of intact rock3 Point load tests on rocks with a uniaxial compressive strength below 25 MPa are likely

The highest primary rock stress 30 MPa is horizontal and oriented perpendicularly to the Table 2 Strength reduction factor sx/sc volume x=pd3/4 in cm3

the omission of Table 27 USBR Unified Soil Classification Chart This is strength of less than 1 MPa ie to that of a soil and the parent rock fabric is visible

has a uniaxial compressive strength below 20 MPa determined directly by factor of 24 as a correlation between UCS and IS 50 However this conversion

May 14 rate of 1 MPa/s until failure occurs Fig Table 2 shows the triaxial compressive strength Table 1 Uniaxial compressive strengths of rock salt

Feb 14 between the strength and cuttability for rock that is commonly associated with Table 1 A summary of the samples and material properties included in the analysis Rock Type No of Samples UCS MPa Density t/m3

Point load tests on rocks with a uniaxial compressive strength below 25 MPa are likely to Table 113 Values of the constant mi for intact rock by rock group

The Rock Mass Rating system is presented in Table 44 giving the ratings for each of load strength index values of 8 MPa and average RQD values of 70

has also been observed that rock strength is dependent on the type of test or test Table 4 BTS tests results Parameter D mm H mm σBTS MPa σDTS

strength test UCS and the point load strength PLS can be very useful because it allows test size correction factor unconfined compression Is 50 MPa

Unconfined Compressive Strength UCS of rock is considered as an essential Table 1 Recent correlations between UCS and BTS Table 2 the UCS of limestone core samples ranges between to 100 MPa while BTS rang

Nine rock types including Sandstone Limestone Siltstone Dolomite and Marl Table 3 The point load strength index values range from 036 MPa for the

Jun 7 rock strength and RAT grind energy for rocks with compressive MPa Sample identifications are given in Table 1 THOMSON ET AL ROCK

A basaltic rock mass is the relevant material for which strength properties must be This value contrasts with the average tensile strength of intact basalt of about 1 8 MPa listed in the Typical values of these parameters are given in Table 1

studies of rock strength rock magnetism and seismic velocity with detailed geologic Table 4 Hayward Fault Sample Results Sample run Pe MPa failure

questionable values for the rock mass strength and should be used with caution in low stress APPENDIX 1 Tables for Estimation of Parameters in the Hoek Brown 25 MPa mi = 10 GSI = 20 = Original criterion Equation 21

Compressive strengths range from 25 MPa 3 670 psi to 97 MPa 13 970 psi strength concrete containing basalt is controlled by the strength of the rock and the There is strong evidence that aggregate type is a factor in the strength of

It is the author s contention that the uniaxial strength of rock Mean Median Mean Median MPa MPa MPa MPa MPa MPa 90 86 178 146 179 190 Table 5

Jun 4 What is needed still is an initial measure of rock strength provided by C0 Table 2 Uniaxial compressive strength Co Fig With a lower porosity of 19 Berea sandstone has a much higher strength of 440 MPa Fig 4b

2 TABLE IV CLASSIFICATION OF ROCK MATERIALS FOR STRENGTH Description Point load strength index MPa Uniaxial compressive strength MPa

Polygon with four rock strength contour lines and their UCS values plotted square inch = psi and megapascal = MPa where 1MPa = psi

friction tanϕ is 05 to 07 Cohesive strength τ0 Rock 10 000 kPa Silt 75 kPa Clay Gravel soil 70 170 MPa loose to compact Soft clay 1 3 MPa Hard clay

compressive strength of approximately 1 MPa 145 psi for safe re entry of miner shotcrete to set sufficiently for safe re entry is a key factor in the mining cycle

The point load strength index for location 1 has an average value of 16 MPa and Figure 2 Correlation chart for Schmidt L hammer relating rock density