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[Display omitted] • RSM-BBD was selected to analyzed liquidity and rheological behavior of CASB slurry. • τ 0 , η increased and S f decreased with RSM single factor and interaction terms. • In interaction, an improvement in one factor promoted the effect of another factor. • τ 0 and η increased as a quadratic or primary function with the curing time. Slurry transportation in pipelines is the key link in the filling process. Liquidity and rheological behavior are important bases for evaluating the feasibility and stability of slurry pipeline transportation and the rheological behavior is time-dependent. Research on the performance and application of cemented aeolian sand (AS) backfill (CASB) is in the preliminary stage, and the time effect and continuous response of various factors to the rheological behavior of CASB slurry have not been studied. Here, the CASB slurry contained AS as an aggregate, fly ash (FA) as an auxiliary material, ordinary Portland cement (PO) as a cementitious material, and water. The response surface method (RSM) was adopted to analyze the influence of PO content (x 1), FA–AS ratio (x 2), concentration (x 3), and their interaction terms (x 1 x 2 , x 1 x 3 , and x 2 x 3) on the rheological parameters (yield stress (τ 0) and viscosity coefficient (η)) of slurry at 0, 40, 80 and 120 min. Additionally, liquidity (slump flow (S f) and bleeding rate (B r)) of fresh slurry was evaluated. The rheological parameters increased with PO content, FA–AS ratio, and concentration, except that the bleeding rate first decreased and then increased with PO content, the slump flow and bleeding rate decreased with each response factor. The interaction term, x 2 x 3 had a significant influence on τ 0 and η at each curing time and S f and B r , x 1 x 3 had a significant influence on the τ 0 and η at 40, 80, and 120 min, and x 1 x 2 influenced τ 0 and η at 80 and 120 min significantly. An improvement in one factor promoted the strengthening of another factor. τ 0 increased as a quadratic function, and η increased as a primary or quadratic function with curing time. The fitting degree between τ 0 , η , and curing time was > 0.9, indicating that the rheological parameters of the slurry had a strong time dependence. In conclusion, this study determined the influence and mechanisms of PO content, FA-AS rate, concentration, and their interaction terms on the rheological behavior with time dependence and fresh slurry liquidity of CASB, thereby providing theoretical and engineering guidance for CASB filling. [ABSTRACT FROM AUTHOR]

• The increase in load-bearing capacity of the FCF is dependent on the strength increase of the filling body. • The filling body restrains the lateral deformation of the coal pillar to increase its load-bearing capacity. • The load-bearing process of FCF has a distinct stage of transition between the primary and secondary load-bearing structures. • As the width of the coal pillar increases, the crack initiation gradually moves from the pillar to the filling body. The continuous mining and filling cemented coal mining (CMCB) technology solves the problem of unbalanced mining and filling efficiency in the coal mining with lane-type cemented filling. In order to study the alternate bearing characteristics of the roof of the field under this process, it is divided into the coal pillar bearing area, co-bearing area, and the filling body bearing area. In order to further study the mechanical properties and failure characteristics of the composite load-bearing structure composed of the filling body - coal pillar - filling body (FCF) in the co-bearing area, the strength growth law of the FCF and its crack expansion law is revealed through the uniaxial compression test. And the primary and secondary load-bearing relationships between the coal pillar and the filling body were obtained by the digital image correlation (DIC) method and the static strain test. The influence of coal pillar width on the strength of the FCF is further revealed by establishing the PFC model. The results show that: increasing the strength of the filling body can improve the overall strength of the FCF both directly and indirectly; while the interaction between the filling body and the coal pillar is distributed as large in the middle and small at the ends, and increases significantly with the increase in the strength of the filling body; the cracks of the FCF appear first at the weak structural surface formed by the coal pillar and the filling body, and the coal pillar is the main load-bearing structure before the peak stress, and gradually transitions to the secondary load-bearing structure in the post-peak deformation stage. The test results can be used as a reference for the design of the width of the lane, the optimization of the mining process, and the proportioning of the filling slurry. [ABSTRACT FROM AUTHOR]