Issue 53

A. Kostina et alii, Frattura ed Integrità Strutturale, 53 (2020) 394-405; DOI: 10.3221/IGF-ESIS.53.30

(5)

   σ 0





:   σ C ε ε p

(6)

1 2

 

     

 

T

(7)

ε

u u

       n n F tg c

0

(8)



σ F

ε  p





(9)



where  ={  r ,   ,  z ,  rz } is the stress tensor,  ={  r ,   ,  z ,  rz } is the strain tensor, С is the tensor of elastic constants which reduces in the isotropic case to two elastic constants (E ′ – Young’s modulus,  – Poisson’s ratio), u ={ u r , u z } is the displacement vector,  p ={  p r ,  p  ,  p z ,  p rz } is the plastic strain tensor, F is the Mohr-Coulomb yield criterion,    n is the maximum tangential stress in the area with a normal n ,  n is the normal stress operating in the same area,  is the indefinite multiplier determined using Prager’s compatibility conditions, and the dots over the symbols denote time derivatives. The Prager compatibility conditions are written as

0   F

0, 0    F , (or

(10)

0, 0     F , (and

0   F )

(11)

The system of Eqns. (5)-(11) is supplemented with boundary conditions that correspond to the calculation scheme from Fig.1.



z u

0

(12)



1

 



(13)

n σ

P

2 

 



(14)

'

n σ

P



3

where the vectors P ={ p ,0} and P ′ ={ p ′ ,0} correspond to the calculated loads obtained by the formulas:

  r h p p p

(15)

2 90 

  

  

  

0

0









90

    

2  

p

' g h tg

c tg

(16)

 

r

m

2

2

    h w gw p g h

(17)

' '     m p g h

(18)

In formulas (15) - (18), the following notation is used:  m =2000 kg/m 3 – average density of the material, h ′ – bed rock density,  w =1000 kg/m 3 – water density, g =10 m/s 2 – gravitational constant, h gw =1.5 m – groundwater depth. The load p h is considered only for saturated rocks.

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