Study on static and dynamic strength characteristics of tailings silty sand and its engineering application

Through high pressure oedometer-undrained triaxial tests and dynamic triaxial tests, researches were conducted on the static and dynamic strength characteristics of the tailings silty sand of No. 4 tailings reservoir in De-xing copper mine. The Mohr-stress circles of the tailings silty sand under all the testing confining pressure show that the single line failure envelope cannot represent the strength characteristics absolutely, the double line failure envelope can express the strength properties when confining pressures are less than 1400 kPa, and the parabolic failure envelope can reflect the strength characteristics well under all the testing confining pressures. The grading curve of the tailings silty sand indicates that the grain composition is relatively homogeneous. Thus, the tailings silty sand is susceptible to liquefy under the dynamic loading. Dynamic triaxial tests of the tailings silty sand show that the tailings silty sand in deep areas has more liquefaction resistance strengths than in shallow. The possible explanation is that the structure of the deep tailings silty sand is more stable than the shallow one. The tests also reveal that the liquefaction resistance increases with the dry density when it is in the range of 1.51-1.61. The results can be used to guide the construction and ensure the safety of No. 4 tailings dam or other high tailings dams.     

Dynamic numerical simulation of coal mine fire for escape capsule installation

Fire in mine laneway leads to disordered ventilation system airflow, and smoke will result in staff poisoning. In such situation, it necessitates to install a rescue capsule in the common staff area. In this paper, the software Fluent was used to simulate the airflow conditions dynamically in No. 5 belt roadway of Kongzhuang Coal Mine when fire broke out. The migration law of CO front was determined. By underground escape experiments, personnel escape velocity model in pathway was established. Based on the numerical simulation and results of field experiments, the escape capsule installation location in the passageway of No. 5 belt roadway was ascertained.     

Mining disturbance effect and mining arrangements analysis of near-fault mining in high tectonic stress region

Dynamic disasters can be easily induced by mining disturbance in the tectonic stress concentration region near the fault. Based on the fault Coulomb failure stress criterion, a dynamic Coulomb failure stress increment model is established for quantitative assessment of mining disturbance effect. Furthermore, the disturbance effects of two possible working face arrangements near the same fault are compared by using the proposed dynamic Coulomb failure stress model and numerical method. The results show that Coulomb failure stress increment, as a comprehensive mechanical parameter, can well reflect the mining disturbance to the stress environment of fault. The disturbance effect on the fault in the case of the working face perpendicular to fault is much less than that of the working face parallel to fault, therefore the dynamic disaster risk induced by the former arrangement is much lower.     

Nonlinear molecular based modeling of the flash point for application in inherently safer design

New chemical process design strategies utilizing computer-aided molecular design (CAMD) can provide significant improvements in process safety by designing chemicals with required target properties and the substitution of safer chemicals. An important aspect of this methodology concerns the prediction of properties given the molecular structure. This study utilizes one such emerging method for prediction of a hazardous property, flash point (FP), which is in the center of attention in safety studies. Using such a reliable data set comprising 1651 organic and inorganic chemicals, from 79 diverse material classes, and robust dynamic binary particle swarm optimization for the feature selection step resulted in the most efficient molecular features of the FP investigations. Apart from the simple yet precise five-parameter multivariate model, the FP nonlinear behavior was thoroughly investigated by a novel hybrid of particle swarm optimization and support vector regression. Besides, 195 missing experimental FPs of the DIPPR data set are predicted via the presented procedure.     

Pressure characteristics and dynamic response of coal mine refuge chamber with underground gas explosion

Coal mine refuge chambers are new devices for coal mine safety which can provide basic survival conditions after gas explosion. In order to simulate the propagation of underground methane/air mixture blast wave, and check structural safety of coal mine mobile refuge chamber, an underground tunnel model and a refuge chamber model have been established based on explicit nonlinear dynamic ANSYS/LS-DYNA 970 program. Results show that the reflected wave pressure on the impact surface was about two times higher than that on the incident one. The relationship between the pressure fields of the chamber was analyzed. The maximum pressure of gas explosion reached about 0.71 MPa, and the pulse width was 360 ms. The maximum absolute displacement and stress occurs at the main door center and the connection of stiffeners and the front plate, respectively. The entire coal mine mobile refuge chamber was in elastic state and its strength and stiffness meet the safety requirements. The cabin door, the front plate and the connecting flange at cabin back as well as the stiffeners on each side were the most critical components. Suggestions were put forward for the refuge chamber.     

Alternative transportation fuel standards: Welfare effects and climate benefits

This paper develops an integrated model of the fuel and agricultural sectors to analyze the welfare and greenhouse gas emission (GHG) effects of the existing Renewable Fuel Standard (RFS), a Low Carbon Fuel Standard (LCFS) and a carbon price policy. The conceptual framework shows that these policies differ in the incentives they create for the consumption and mix of different types of biofuels and in their effects on food and fuel prices and GHG emissions. We also simulate the welfare and GHG effects of these three policies which are normalized to achieve the same level of US GHG emissions. By promoting greater production of food-crop based biofuels, the RFS is found to lead to a larger reduction in fossil fuel use but also a larger increase in food prices and a smaller reduction in global GHG emissions compared to the LCFS and carbon tax. All three policies increase US social welfare compared to a no-biofuel baseline scenario due to improved terms-of-trade, even when environmental benefits are excluded; global social welfare increases with a carbon tax but decreases with the RFS and LCFS due to the efficiency costs imposed by these policies, even after including the benefits of mitigating GHG emissions.     

基于光纤光栅的斜拉索振动参数监测实验研究

斜拉索是斜拉桥的主要受力构件 ,对其动力特性进行监测具有重要意义。斜拉索工作条件恶劣 ,现有的测试方法难以实现长期在线监测 ,实现斜拉索的振动在线测量 ,传感器是问题的关键。光纤光栅传感器具有极其优良的稳定性 ,已被证实适用于长期监测 ,在结构监测领域具有非常广泛的应用前景。笔者提出了一种基于光纤光栅传感器的斜拉索动力特性在线监测方法 ,建立了用光纤布拉格光栅作传感器监测斜拉索振动的测量模型 ,为验证该模型建立了模拟试验装置 ,在实验室进行了模拟实验研究 ,并将光纤光栅和传统的电阻应变片两种测量方法进行了实验对比。与传统测试手段相比 ,该方法结构简单 ,成本低 ,并能实现斜拉索动力特性的长期在线监测。     

锚杆支护巷道安全监测技术

锚杆支护巷道顶板冒落具有突发性和冒落面积大的特点 ,安全监测非常必要。笔者介绍了国内近年来最新研制的CM— 2 0 0型测力锚杆、GYS— 30 0型锚杆 (索 )测力计、LBY— 3型顶板离层指示仪、ZW— 4型遥测多点位移计等监测仪器 ;提出锚杆支护巷道动态信息施工方法 :监测施工、监测信息反馈、检验和修正设计 ,循环往复 ,以达到最佳施工效果。     

基于神经网络的煤层自然发火的非线性预测

煤炭自燃是一典型的非线性现象。笔者论述了煤炭自燃的危害 ,从非线性理论的角度分析了煤炭自燃的本质特征 ;应用神经网络中BP网络这一高度非线性关系映射建立了自然发火预测模型 ,克服了传统预测方法的不足并在山东枣庄矿业集团公司柴里煤矿进行了预测分析 ,预测结果与验证结果基本吻合 ,取得了满意的效果 ,为解决煤炭自燃的预测提供了一条良好的思路和方法 ,具有较大的理论意义和应用价值。     

薄膜结构在动风荷载下的安全性能分析

从理论和实践两方面对薄膜结构在风荷载下的安全性能进行了研究。根据随机过程理论 ,用计算机模拟生成具有空间相关性的风场。发展建立了膜结构几何非线性动力响应问题的有限元公式 ,并以此为基础对一具体的膜结构进行了动力时程响应分析。通过观察膜结构在不同风速下的位移时程曲线 ,笔者发现 :当外界风速小于一定的临界风速时 ,结构的位移响应会逐渐趋于稳态 ,结构的振动逐渐趋于稳定 ,这时结构是安全的 ;当外界风速超过或接近临界风速时 ,结构的振幅会逐渐增大 ,膜结构将可能发生驰振损坏。进而提出了通过增大膜内预应力或提高膜曲面的曲率来防止膜结构风振破坏的方法 ,并指出了在设计和施工中为保证膜结构的风振安全应当采取的措施。