Table 4 The results of the regression analysis.

From: Influence of rock heterogeneity on the correlation between uniaxial compressive strength and Brazilian tensile strength

Sample types

Equation

Equation No.

R2

P-value

AIC

PI

Fine grain size

\(\:\text{UCS=15.043}\text{BTS}\)

(1)

0.985

1.55 × 10− 6

37.44

63.86

Coarse grain size

\(\:\text{UCS=29.645}\text{BTS}\)

(2)

0.958

2.43 × 10− 5

45.49

10.52

All sandstone samples

\(\:\text{UCS=18.175}\text{BTS}\)

(3)

0.876

2.24 × 10− 7

103.43

-133.43

Gneissosity: β = 0°

\(\:\text{UCS=20.541}\text{BTS}\)

(4)

0.962

9.42 × 10− 5

37.00

44.03

Gneissosity: β = 45°

\(\:\text{UCS=29.01}\text{BTS}\)

(5)

0.988

4.96 × 10− 6

28.49

59.70

Gneissosity: β = 90°

\(\:\text{UCS=-1.306}\text{BTS+109.45}\)

(6)

0.0198

0.76

33.65

-8.35

Gneissosity: β = 45°, 90°

\(\:\text{UCS=22.972}\text{BTS}\)

(7)

0.947

2.21 × 10− 8

74.65

15.91

All gneiss samples

\(\:\text{UCS=25.554}\text{BTS}\)

(8)

0.887

6.00 × 10− 10

134.18

-141.93

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