This study investigates the time-dependent rheological behavior of cemented paste backfill (CPB) that contains alkali-activated slag (AAS) as a binder. Rheological measurements with the controlled shear strain method have been conducted on various AAS-CPB samples with different binder contents, silicate modulus (Ms: SiO₂/Na₂O molar ratio), fineness of slag and curing temperatures. The Bingham model afforded a good fit to all of the CPB mixtures. The results show that AAS-CPB samples with high binder content demonstrate a more rapid rate of gain in yield stress and plastic viscosity. AAS-CPB also shows better rheological behavior than CPB samples made up of ordinary Portland cement (OPC) at identical binder contents. It is found that increasing Ms yields lower yield stress and plastic viscosity and the rate of gain in these parameters. Increases in the fineness of slag has an adverse effect on rheological behavior of AAS-CPB. The rheological behavior of both OPC- and AAS-CPB samples is also strongly enhanced at higher temperatures. AAS-CPB samples are found to be more sensitive to the variation in curing temperatures than OPC-CPB samples with respect to the rate of gain in yield stress and plastic viscosity. As a result, the findings of this study will contribute to well understand the flow and transport features of fresh CPB mixtures under various conditions and their changes with time.

Blasting vibration could cause dynamic instability of rock masses within a critical steady state. To control the blasting vibration, it is necessary to understand the complete dynamic response process of the rock masses under the blasting vibration. The Long Short-Term Memory (LSTM) technique uses blast monitoring data to predict the full waveform of the blast vibration. Based on the LSTM, a new full waveform prediction model is proposed in this study. To verify the feasibility of the proposed model, the sample data were constructed using the well-known linear blast wave superposition prediction formula. The full waveform prediction model is trained and the predicted waveform and the actual waveform are then evaluated and compared. The loss function is calculated and discussed, which verifies the feasibility of the prediction method. In addition to the numerical research, the actual blasting vibration data are also used for verification. The parameters, such as sequence size, training algorithm, and some hidden layer nodes, are discussed and optimized. The results show that the proposed full waveform prediction model based on LSTM can predict the full blasting waveform. This study provides a new idea for the prediction and control of blasting vibration.

Considering the problems related to hard rock blasting under high in-situ stresses at large depths, we conducted crater blasting tests on sandstone specimens under three static load conditions to investigate the strain field evolution of rock blasting under high stress. The digital image correlation (DIC) technique was used to monitor the evolution of the strain field on the free surface. Thus, the influence of the static stress on the blasting strain field was analyzed, and the formation mechanism of cracks on the free surface was elucidated. The results indicate that a circular tensile strain zone was formed without static loading. The direction of the maximum principal strain was perpendicular to the radius, which lead to the random emergence of multiple radial tensile cracks. Under a uniaxial static loading, an elliptical tensile strain zone was formed. The direction of the maximum principal strain was perpendicular to the static loading direction. This facilitated the initiation and propagation of tensile cracks preferentially in the direction parallel to the static loading. Under an equal biaxial static loading, the initial compressive strain in the specimen reduced the increment rate of the blasting strain, and restrained the formation of surface cracks. Besides, a determination method for dynamic tensile fracture strain of rock was proposed.

The construction of urban subway tunnels typically induces soil settlement within a specific radius of the surrounding area. However, the accuracy of current methods for predicting ground deformation curves corresponding to the excavation of double-track tunnels with small spacing remains insufficient. Most studies simplify this problem by modeling it as a two-dimensional plane problem; however, the actual ground deformation exhibits pronounced three-dimensional characteristics. Consequently, studying the ground settlement patterns caused by the construction of small-spacing double-track tunnels is crucial. This study is based on the Peck formula, used to calculate surface settlement caused by the excavation of single-track tunnels. By incorporating the maximum settlement offset e and the soil loss rate η(y), the soil displacement calculation formula is derived for small-spacing double-track tunnel excavation. The accuracy of the derived formula is then validated through a case study. The findings provide a theoretical reference for predicting surface settlement induced by the excavation of small-spacing double-track tunnels. Furthermore, the influence of different parameters on ground settlement patterns is explored. The results indicate that appropriately increasing the tunnel spacing, increasing burial depth, and adopting a sequential excavation method for the two tunnels help reduce ground settlement.

Underground mining is a complex dynamic system. Traditional static analytical methods are insufficient to characterize the operational behavior and efficiency variations in such systems under coupled multidimensional constraints. To address this limitation, this study proposes a novel hybrid simulation-modeling method for underground mining processes with multidimensional constraints. The method integrates discrete-event simulation and agent-based simulation. It reconstructs the spatiotemporal constraints of multiple stopes, process constraints, and organizational constraints into an explicit multidimensional constraint system. Using the upward horizontal layered cut-and-fill mining method at the Sanshandao Gold Mine as an engineering case, a simulation model was established for development, cutting, stoping cycles, haulage, and backfilling. Key factors, including stope availability, backfill curing delays, centralized blasting, shift organization, and equipment availability, were embedded as explicit mechanisms. The results show that simulated operating time, production, and efficiency are generally consistent with field statistical data at multiple scales, including cycle operations, individual stopes, individual horizontal layers, and complete mining blocks. This indicates that the model can effectively reproduce the operating characteristics of the underground mining system under multidimensional constraints. Further analysis shows that production rhythm is governed by the combined effects of stope spatiotemporal relationships, process coordination, backfill waiting, and organizational resource constraints, rather than by single-process capacity. Spatiotemporal and process constraints define operation initiation and advancement sequence, while organizational constraints mainly appear as waiting accumulation, process disturbances, and resource-utilization fluctuations. The proposed method provides a reusable tool for capacity evaluation, production organization analysis, and decision optimization in complex underground mines.