In multi-angle dynamic light scattering measurements, due to the inevitable presence of baseline measurement noise, the normalized intensity autocorrelation function (ACF) data deviates from the true value. This leads to incorrect angular weighting estimates, which affect the accuracy of inversion results and determination of particle size distributions (PSDs). We outline a method to calculate better angular weighting coefficients from the noisy intensity ACF data. The method involves first compensating for the baseline error in the ACF data and then determining the weighting coefficients. We demonstrate the method using simulated ACF data containing baseline error for unimodal and bimodal PSDs and also for experimental data for unimodal and bimodal samples. For the unimodal PSDs ACF data were simulated for 100-900 nm and 100-650 nm particle size ranges, and for bimodal PSDs 360-900 nm and 100-900 nm particle size ranges were used. The performance of our method was shown by comparing the results of weighting coefficient and PSD determination with and without baseline compensation to the known coefficient values and PSDs. With baseline compensation the relative error of the weighting coefficients decreased significantly. Furthermore, with baseline compensation, the PSD results for the four groups of simulated data were improved. The deviations between the known and recovered PSDs were decreased, the relative error of peak position obviously decreased, and the occurrence of false peaks was reduced. The PSD results from the experimental data further validates the conclusion that the method proposed apparently reduces the relative error of peak position, effectively eliminates the false peak, and improves the accuracy of the recovered PSD.

Dynamic light scattering (DLS) is a popular method of particle size measurement. Multiangle dynamic light scattering (MDLS) collects DLS data at multiple angles and analyzes the data simultaneously to improve the particle size measurement. Using data from several scattering angles admits the possibility of introducing noise caused by scattering angle error in the measurement, which may have an impact on the performance of the MDLS technique. We investigate the effect of scattering angle noise on recovered particle size distributions (PSDs) using simulated and measured MDLS data and various levels of angular noise. Our results show that, for unimodal PSDs, those with small particle sizes are more strongly affected by the noise than are medium and large particle size systems. For bimodal PSDs, those containing small-sized particles are also more affected by the noise than the systems of larger particles. Furthermore, broad PSDs are more vulnerable to angular noise than narrow PSDs.

The Barun Open-pit Mine has formed a 2-benches or 4-benches parallel mining condition due to the steep end-slope mining. In the enlarging process, the operation safety conditions of equipment are poor. In order to improve the operating conditions, increase the efficiency of slope enlarging, and reduce the mining cost, a technical solution is proposed that uncoupling the top air-deck charge structure by loosening blasting in the 24-m high bench. Based on the Holmquist-Johnson-Cook (HJC) constitutive model, the physical mechanism of the stress wave attenuation in the rock is analyzed. Considering the attenuation, reflection, transmission, and superposition of the pressure produced by the charge, the stress of any point in the rock medium is calculated. Furthermore, the rock state at that point is judged. The results show that the top air-deck reduces the stress at the top of the slope. Although the top resistance line is smaller than the bottom of the slope, with the top air-deck, the rock stress state at the top of the slope is not much larger than the bottom charge section, which makes the rock loose and does not produce a throwing phenomenon. After blasting, the muck pile has a good shape. The top air-deck charge structure has obvious effects in loose blasting, which provides a practical exploration for the slope enlarging of high benches in open-pit mines.

The present study considers the so-called air deck blasting, one of the most commonly used techniques for the improvement of blasting efficiency in mining applications. In particular, it aims to improve the operating conditions of large-scale equipment, increase the efficiency of the slope enlarging process, and reduce the mining cost. These objectives are implemented through a two-fold approach where, first, a program for slope enlarging based on the middle air-deck charge blasting-loosening technology is proposed, and second, the physical mechanism responsible for the stress wave attenuation in the rock is analyzed in the framework of a Holmquist-Johnson-Cook constitutive model. Field test results verify that the proposed approach is highly efficient and economical when used in medium-hard rock blasting and thus provides a basis for the practical implementation of slope enlargement for high benches in Open-Pit Mines.

The microparameter calibration of the particle flow parallel bond model (PBM) is mostly based on a uniaxial compression test. The microparameters calibrated only by uniaxial compression tests cannot be directly used to study the mechanical properties of rocks with surrounding pressure conditions. To analyze the relationship between the macroparameters and microparameters in the model and select appropriate particle flow model parameters, this study conducted a particle flow numerical simulation experiment based on the basic test principles of the uniaxial compression, Brazilian splitting, and triaxial compression tests. An orthogonal experimental design was performed for the calibration of the microparameters of the particle flow PBM, and multifactor analysis of variance was used to screen out the factors that have a considerable influence on the experimental indicators. Regression analysis was performed on the significant influencing factors and test indicators, and the corresponding linear and nonlinear relationships between the macroparameters and microparameters were obtained. Lastly, the microparameters of the model were determined in accordance with the macroparameters of the mechanical test of the Barun open-pit mine dolomite, and a numerical simulation test was conducted. Simulation test results were consistent with the actual test results, thus providing a basis for a subsequent numerical simulation study on the mechanical properties of dolomite.