Abstract
To reveal the mechanical response of a multi-pillar supporting system under external loads, compressive tests were carried out on single-pillar and double-pillar specimens. The digital speckle correlation method and acoustic emission technique were applied to record and analyse information of the deformation and failure processes. Numerical simulations with the software programme PFC2D were also conducted. In the compressive process of the double-pillar system, if both individual pillars have the same mechanical properties, each pillar deforms similarly and reaches the critical stable state almost simultaneously by sharing equal loads. If the two individual pillars have different mechanical properties, the pillar with higher elastic modulus or lower strength would be damaged and lose its bearing capacity firstly. The load would then be transferred to the other pillar under a load redistribution process. When the pillar with higher strength is strong enough, the load carried by the pillar system would increase again. However, the maximum bearing load of the double-pillar system is smaller than the sum of peak load of individual pillars. The study also indicates that the strength, elastic modulus, and load state of pillars all influence the supporting capacity of the pillar system. In underground space engineering, the appropriate choice of pillar dimensions and layout may play a great role in preventing the occurrence of cascading pillar failure.
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Abbreviations
- DSCM:
-
Digital speckle correlation method
- PFC2D :
-
Two-dimensional particle flow code
- AE:
-
Acoustic emission
- RIO:
-
Region of interest
- EMR:
-
Elastic modulus rate
- LCR:
-
Load-carrying rate
- P :
-
The force acting on single-pillar system
- a, b, c, d, e :
-
The load state of pillar in single-pillar system
- a′, b′, c′, d′, e′:
-
The cumulative AE counts state of pillar in single-pillar system
- a I, c I, e I :
-
The load state of pillar I in double-pillar system
- \(a_{\text{I}}^{\prime } ,c_{\text{I}}^{\prime } ,e_{\text{I}}^{\prime }\) :
-
The cumulative AE counts state of pillar I in double-pillar system
- a II, c II, e II :
-
The load state of pillar II in double-pillar system
- \(a_{\text{II}}^{\prime } ,c_{\text{II}}^{\prime } ,e_{\text{II}}^{\prime }\) :
-
The cumulative AE counts state of pillar II in double-pillar system
- E I, E II :
-
The elastic modulus of pillar I, pillar II, respectively
- L I, L II :
-
The load carried by pillar I, pillar II, respectively
- F I+II, F I, F II :
-
The limit bearing capacity of double-pillar system, pillar I and pillar II, respectively
- m :
-
The start point of load redistribution
- n :
-
The endpoint of load redistribution
- u, u I, u II :
-
The displacement increment of double-pillar system, pillar I and pillar II, respectively
- P I+II, P I, P II :
-
The forces acting on double-pillar system, pillar I and pillar II, respectively
- f(u I), f(u I):
-
The stiffness coefficient of pillar I, pillar II, respectively
- A, B, C :
-
The local extreme load value state of double-pillar system
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Acknowledgements
The work reported here was supported by financial grants from the National Basic Research Program of China (2015CB060200), the National Natural Science Foundation of China (51322403, 51274254), Hunan province science and technology plan (2016SK2003) and the state scholarship fund (201606370118). The authors wish to acknowledge these financial contributions and their appreciation of the organizations for supporting this basic research.
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Zhou, Z., Chen, L., Zhao, Y. et al. Experimental and Numerical Investigation on the Bearing and Failure Mechanism of Multiple Pillars Under Overburden. Rock Mech Rock Eng 50, 995–1010 (2017). https://doi.org/10.1007/s00603-016-1140-8
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DOI: https://doi.org/10.1007/s00603-016-1140-8