Figure 9. Triaxial testing white sandstone discrete failure

Figure 10. Triaxial testing red sandstone discrete failure

Figure 11. Triaxial testing red sandstone multi state failure

It should be noted that shear and normal stress acting on any plane within sample. And they always lie on a Mohr’s circle (figure 12).

Figure 12. Mohr’s circle

According to figure 12 it can possible to find :

	(6)
	(7)

where – radius of the Mohr’s circle;

– central point of the Mohr’s circle on axis;

Type of test and material	R	Area	№ of sample	Axial load, kN	Axial stress - σ₁, MN/	Confining stress - σ₃, MN/		Confining stress, psi	Center of the Morh circle
White Sandstone	0.019	0.00113	w6		187.907	6.895	90.506		97.401
w7		281.419	20.684	130.367		151.052
w8	399.5	352.436	34.474	158.981		193.455
Red Stone	0.019	0.00113		52.5	46.315	6.895	19.710		26.605
		66.164	13.790	26.187		39.977
	102.5	90.425	27.579	31.423		59.002
Red Stone (Multi state test)	0.019	0.00113			44.9918	6.9	19.0459		25.9459
		65.28221	13.8	25.74111		39.54111
		77.6329	20.7	28.46645		49.16645

Table 4. Results of triaxial testing analysis

It should be noted that relationship between shear and normal stress must generate a straight line that touches each of the Mohr’s circles at only one point. As a result it can possible to determinate cohesion – C and internal fraction angle – tan φ (figure 13).

Дата добавления: 2015-11-14