PSI - Issue 32

A.A. Baryakh et al. / Procedia Structural Integrity 32 (2021) 17–25 Baryakh A.A / Structural Integrity Procedia 00 (2021) 000 – 000

22 6

subsidence of the Earth ’s surface by the end of the displacement process.

0,9 

mp





ok

where  =a/(a+b) is the recovery efficiency, m is the height of the chambers (pillars); p is the parameter that takes into account the effect of filling the chambers, p= 1 – A (1 – B ), А is the filling factor of the chambers, and В is the shrinkage factor of the filling mass, depending on the technology and type of filling (dry or hydraulic).

Fig. 2. A scheme to determine the system parameters taking into account dissolution: (a) is the original chamber block, (b) is the chamber block taking into account the degradation of the pillars, (c) is the reduced chamber block used in the design scheme.

Formally, the degra dation of pillars due to dissolution leads (Δ) to changes in the parameters of the pillar mining system (Fig. 2). For the unfilled chambers (А=0) , new mining parameters taking into account dissolution were determined as follows:

   2 * a a    2 * b b

(11)

) * a b       . For the filled chambers ( 2 /(

0  A )

*

2 (1 ) A 2 (1 ) A

a a     b b     *

(12)

) * A a b        . 2 (1 ) /(

In addition, in equations (11) and (12), the degradation value of the pillars Δ was corrected, depending on the degree of switching off of the chambers M      max (changes in their volume due to the deformation and destruction of pillars), where the correction factor was determined by the ratio of the current subsidence of the earth surface to the finite ones Δ M=η(t)/η ok . Taking into account the degradation of the pillars, changes in the degree of loading is estimated by the ratio:

k k

b

f f

*

,

(13)

C C 

* *

b

where С is the initial degree of the pillar loading; k f is the initial form factor of the pillar, which is characterised by