Dynamic analysis of granite rockburst based on the PIV technique

This paper describes the deep rockburst simulation system to reproduce the granite instantaneous rockburst process.Based on the PIV(Particle Image Velocimetry)technique,quantitative analysis of a rockburst,the images of tracer particle,displacement and strain fields can be obtained,and the debris trajectory described.According to the observation of on-site tests,the dynamic rockburst is actually a gas–solid high speed flow process,which is caused by the interaction of rock fragments and surrounding air.With the help of analysis on high speed video and PIV images,the granite rockburst failure process is composed of six stages of platey fragment spalling and debris ejection.Meanwhile,the elastic energy for these six stages has been calculated to study the energy variation.The results indicate that the rockburst process can be summarized as:an initiating stage,intensive developing stage and gradual decay stage.This research will be helpful for our further understanding of the rockburst mechanism.

Particle swarm optimization and its application to seismic inversion of igneous rocks

In order to improve the fine structure inversion ability of igneous rocks for the exploration of underlying strata, based on particle swarm optimization(PSO), we have developed a method for seismic wave impedance inversion. Through numerical simulation, we tested the effects of different algorithm parameters and different model parameterization methods on PSO wave impedance inversion, and analyzed the characteristics of PSO method. Under the conclusions drawn from numerical simulation, we propose the scheme of combining a cross-moving strategy based on a divided block model and high-frequency filtering technology for PSO inversion. By analyzing the inversion results of a wedge model of a pitchout coal seam and a coal coking model with igneous rock intrusion, we discuss the vertical and horizontal resolution, stability and reliability of PSO inversion. Based on the actual seismic and logging data from an igneous area, by taking a seismic profile through wells as an example, we discuss the characteristics of three inversion methods, including model-based wave impedance inversion, multi-attribute seismic inversion based on probabilistic neural network(PNN) and wave impedance inversion based on PSO.And we draw the conclusion that the inversion based on PSO method has a better result for this igneous area.

磷矿正-反浮选产品粒度分布与存在问题分析(II)——回水流程实验

通过对浮选产品的粒度分析,指出了某磷矿正反浮选连续性实验(回水流程)存在的问题,并提出了改进建议。

Simultaneous investigation of blast induced ground vibration and airblast effects on safety level of structures and human in surface blasting

The significance of studying, monitoring and predicting blast induced vibration and noise level in mining and civil activities is justified in the capability of imposing damages, sense of uncertainty due to negative psychological impacts on involved personnel and also judicial complaints of local inhabitants in the nearby area. This paper presents achieved results during an investigation carried out at Sungun Copper Mine, lran. Besides, the research also studied the significance of blast induced ground vibration and air- blast on safety aspects of nearby structures, potential risks, frequency analysis, and human response. According to the United States Bureau of Mines （USBM） standard, the attenuation equations were devel- oped using field records. A general frequency analysis and risk evaluation revealed that： 94% of generated frequencies are less than 14 Hz which is within the natural frequency of structures that increases risk of damage. At the end, studies of human response showed destructive effects of the phenomena by ranging between 2.54 and 25.40 mm/s for ground vibrations and by the average value of 110 dB for noise levels which could increase sense of uncertainty among involved employees.

A numerical test method of California bearing ratio on graded crushed rocks using particle flow modeling

In order to better understand the mechanical properties of graded crushed rocks （GCRs） and to optimize the relevant design, a numerical test method based on the particle flow modeling technique PFC2D is developed for the California bearing ratio （CBR） test on GGRs. The effects of different testing conditions and micro-mechanical parameters used in the model on the CBR numerical results have been systematically studied. The reliability of the numerical technique is verified. The numerical results suggest that the influences of the loading rate and Poisson＇s ratio on the CBR numerical test results are not significant. As such, a loading rate of 1.0-3.0 mm/min, a piston diameter of 5 cm, a specimen height of 15 cm and a specimen diameter of 15 cm are adopted for the CBR numerical test. The numerical results reveal that the GBR values increase with the friction coefficient at the contact and shear modulus of the rocks, while the influence of Poisson＇s ratio on the GBR values is insignificant. The close agreement between the CBR numerical results and experimental results suggests that the numerical simulation of the CBR values is promising to help assess the mechanical properties of GGRs and to optimize the grading design. Be- sides, the numerical study can provide useful insights on the mesoscopic mechanism.

Influence of water and rock particle contents on the shear behaviour of a SRM

The contents of both water and rock particles are important factors affecting the mechanical strength of a soil–rock mixture(SRM)filled subgrade in the western mountainous area of China.Therefore,the purpose of this paper is to study the mechanisms of reconstituted landslide deposit samples with different water and rock particle contents by analysing the characteristics of shear strength,volumetric strain and‘jumping’phenomenon via large-scale direct shear tests.The results show that the influence of water content on shear strength is greater than the influence of rock particle content under a lower normal stress,and the results are reversed in the case of a higher normal stress.The effect of water content on the equivalent cohesion is bigger,especially for the sample with a high rock particle content.The friction angle of the specimen with same water content increases with the increasing rock particle content,but when the number of rock particles increases to a certain extent,there is a little effect on the friction angle.However,the friction angle decreases with increasing water content at the same rock particle content.Specimens with the same rock particle content change from dilation to compression with increasing water content.Finally,the continuous stage of the‘intense jumping’at different water content has been analysed.The‘jumping’phenomenon of samples with low water and rock particle content will first strengthen and then weaken the samples with increasing normal stress.