Issue 27

G. Kuidong et alii, Frattura ed Integrità Strutturale, 27 (2014) 43-52; DOI: 10.3221/IGF-ESIS.27.06

shown in Tab.1. The shape and interrelated geometric parameters are shown in Fig.5. Fig.6 shows the theoretical and experimental vertical fracture angle under different cutting angle, the difference less than 5 percent between them indicates that the established vertical mechanical model of rock fragment is valid.

Properties

Value

Modulus of elasticity E (GPa)

19

Density ρ (kg/m 3 )

2650

Fracture toughness K I

(MPa . m 1/2 )

1.1

Compression strength σ c

(MPa)

103.2

Tensile strength σ t

(MPa)

7.1

Table 1 : Mechanical properties of marble.

Figure 4 : Laboratory furniture of rock cutting linearly: 1-rock specimen; 2-guideways; 3-clamping device of conical pick; 4-conical pick; 5- advancing hydro-cylinder.

Figure 5 : Geometric feature parameters of rock fragment.

Figure 6 : Vertical fracture angle of experiments and theoretical model.

Verification of peak cutting force The k is a geometric factor of the pick independent of material properties which has been mentioned in front contents. In reference [18], the researchers also took an intensive study and detailed explanation of the k . According to Eq.5, the k can be obtained by experiments. Fig.7 is the variation curve of cutting force in rock cutting process, which corresponds to Fig.5. So, the k can be expressed as:

2 2 E P h h   I tan cos ( )d

2 2



2 E K d

K d

4

tan

(18)

F  

I



k



cos E P h 

W

T

c max

48