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Mesoscopic characteristics of residual contact force in block array subjected to partial loading and unloading |
FU Longlong,ZHOU Shunhua,WANG Changdan,GONG Quanmei |
(Key Laboratory of Road and Traffic Engineering of the Ministry of Education,Tongji University,Shanghai 201804,China) |
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Abstract Photo-elastic test was performed to analyze the evolution of force chain and block displacement in block array under a multi-stage loading and unloading cycle. The results demonstrate that both the contact force and block displacement show the visible ‘hysteresis’ during unloading. The evolution characteristics of both the contact force and block displacement indicate a critical load during unloading. A serial contact model was established to simplify the contact state of the block column transmitted by primary force chain,which reveals that the residual contact force depends on the lateral friction resistance,including the inter-particle friction and inter-particle lock. The contact force acted on the representative block was quantified by fringe analysis to achieve the evolution of lateral friction resistance on primary force chain during loading and unloading. The lateral friction resistance is positively associated with the applied load,indicating that greater inter-particle friction and contact resistance induced by the inter-particle lock are activated to resist the increasing applied load. The difference of lateral friction resistance under the same applied load between loading phase and unloading phase is the mechanism of residual contact force in block array.
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