Interaction Between Pillar And Cemented Tailings Backfill And Their Cooperative Support Mechanism

In the cemented tailings backfill method of metal mines,the backfill cooperate with the reserved pillar to support the upper roof,forming a pillar-backfill cooperative support system.As roof-contacted filling is very difficult in the field application,so it is generally considered that the filling body mainly plays a passive supporting role by restraining the lateral expansion of the pillar.However,the passive lateral support effect of the backfill is more likely to be played in the stage of instability of the pillar.During the support process of the filling body,the shearing characterristics in the interface between the pillar and backfill is an important factor affecting the pillar-backfill interaction and their supporting performance.Therefore,it is important to study the effect of backfill quality,interface shearing characteristics and pillar state on the pillar-backfill interaction mechanism,which is of great theoretical significance for evaluating the the stability of the cooperative supporting system and has engineering value for guiding the design of deep underground stope.Based on the above recognazition,the research contents of this paper include the following aspects:1.The internal strain,temperature and settlement of cemented backfill with different cement content were studied by using the Bragg grating sensor and displacement sensor.The coupling mechanism of bleed shrinkage,chemical shrinkage,structure stiffness and internal temperature change in the solidification stage of backfill was revealed,and the key factor that influencing roof-contacted fill was analyzed.2.Based on the principle of coordinated deformation and load transfer method,the mechanical models of the cooperative pillar-backfill support system under the conditions of roof-contacted or not were established respectively,the ultimate bearing capacity of the pillar-backfill cooperative support unit under different conditions were studied,and the influence of interface friction force on the bearing characteristics of support unit were revealed when the backfill were not roof-connected.3.The intertal shear tests of pillar and backfill and interface shear tests between different pillar and backfill series were carried out.The shear strength parameters and shear deformation characteristics in peak and residual shear stages were studied.The intrinsic variation evolution of shear parameters at different stage for internal and interface were analyzed.4.Using the self-developed biaxial loading device,the bearing capacity of the pillar-backfill support unit,the variation in pillar strength and failure mode of the pillar and backfill under different filling rates and lateral stress conditions were studied.The obtained results revealed the interaction mechanism between the pillar and backfill and the influence of the friction force on the bearing capacity of the support system in the pillar pre-peak deformation stage.5.The interaction mechanism between the jointed pillar and backfill was further experimental studied,the variaration in bearing capacity of the support unit and pillar strength under different filling rates and lateral stress conditions were studied.The obtained results were used to analysize the effect of pillar state on the support mechanism of backfill.