海水条件下Cd-CaCO3共沉淀过程的动力学表达:方解石

采用稳定加液系统对海水中方解石(CaCO3)沉淀形成时镉元素(Cd)的共沉淀现象进行了实验模拟,并对Cd-Ca-CO3共沉淀过程中Cd的分异行为进行了定量评估。实验结果显示:Cd在共沉淀过程中发生了明显的分异,基于方解石沉淀和海水溶液各自Cd/Ca比值计算得出的分异系数分别为33.0～61.8(5℃)、31.8～55.0(15℃)和17.4～31.8(25℃)。在各个温度下,DCd值都随着方解石沉淀速率的增加而有规律的下降。进一步分析表明温度和碳酸根浓度是影响Cd分异行为的根本因素。这一实验结果对于Cd/Ca古海洋指标的应用具有重要的参考价值。     

考虑滑面贯通和退化的岩质边坡动力稳定性分析

本文在岩质边坡离散元模型中的岩石块体中设置虚拟节理,将滑动面切割为许多线段相连的直线段,使得模拟滑动面贯通破坏过程成为可能,进而改进了UDEC软件中的Mohr-Coulomb结构面接触模型,使其能够反映结构面在循环荷载下的退化效应。通过算例分析结果表明:考虑滑动面贯通过程的岩质边坡安全系数小于不考虑贯通过程的安全系数,且随着虚拟节理间距的减小,安全系数逐渐增大,最后趋于定值;考虑滑动面退化过程的岩质边坡的安全系数小于不考虑滑动面退化的安全系数,且随着滑动面抗损伤能力的下降,安全系数变小。     

The effects of phosphorus-free inhibitors on the ignition of lycopodium dust

The minimum ignition temperature of dust suspension (MIT) and the hot surface ignition temperature of the dust layer (LIT) are essential safety parameters for the process industry. However, the knowledge of the ignition behavior when solid mixtures of flammable fuels and phosphorous-free inhibitors are considered is still scarce and further experimental and theoretical analyses are requested. In this work, the ignition temperature of phosphorous-free inhibitors (coal fly ash and calcium carbonate) mixed with lycopodium dust have been studied in terms of LIT analysis (hot plate thickness: 5 mm, 12.5 mm and 15 mm), and by the Godbert-Greenwald test for the MIT. Both coal fly ash and calcium carbonate have been tested at different concentrations and particle sizes.Results show that the effects of the inhibitor can be counter-productive when layer ignition temperature is considered even if the minimum ignition temperature of the dust suspension shows a positive effect from the safety point of view. This behavior has been analyzed in the terms of thermal conductivity and diffusivity of the mixture, by using Maxwell's equation for two-phase solid mixtures. Standard empirical correlations for the ignition temperature of solid mixtures have been also tested, showing their weakness in reproducing mixture behavior.     

综放开采覆岩“两带”高度影响因素及预测模型研究*

为研究影响综放开采覆岩“两带”高度预测模型,采用理论分析与经验公式方法系统分析影响覆岩“两带”高度的因素,包括覆岩岩性、覆岩组合结构、煤层赋存状态、顶板控制方法、开采厚度、工作面走向长度与倾向长度、工作面推进速度、覆岩破坏残余变形;并将上述因素划分为采矿地质因素、顶板控制方法、采煤工作面三维尺寸设计参数、时间因素4类;基于此建立综放开采“两带”高度预测模型,并通过工程实例对比、现场实测等方法进行合理性验证。结果表明:芦沟矿与盛泰矿2个工作面的“两带”高度预测值均在实测值范围之内,说明得出的回归式预测效果较好,验证综放开采“两带”高度预测模型的合理性。     

基于弹塑性损伤-渗流耦合模型的隧道洞口段围岩稳定性研究

为分析复杂条件下隧道洞口段稳定性问题,建立基于Mohr-Coulomb准则的岩石弹塑性损伤-渗流耦合模型,利用完全隐式的向后欧拉算法编制弹塑性损伤模型的应力积分程序。在此基础上,利用ABAQUS平台的子程序接口实现耦合模型的有限元计算。将该模型应用于福建某洞口段隧道工程的围岩稳定性评价中,分析不同降雨强度下洞口段结构的安全系数、位移及损伤值的变化规律。结果表明:隧道洞口段结构的安全系数、损伤区和位移均会随着降雨进程的发展发生变化,雨季应加强监测频率。     

深水高桩嵌岩桥墩抗撞能力分析

以2007年6月15日广东九江大桥船撞倒塌事故中被撞深水高桩嵌岩桥墩为研究对象,采用更新拉格朗日列式考虑结构几何非线性,Hognestad模型和Mander模型分别模拟无约束和受约束混凝土,理想弹塑性模型模拟钢筋作用;考虑桩基和周围介质的非线性作用,采用P-Y、T-Z和Q-Z弹簧模拟计算了单个高桩桥墩的抗撞能力,揭示了...     

应用BP神经网络进行隧道围岩快速分级

在隧道施工过程中,为准确、及时地进行围岩快速分级,引入BP神经网络方法,通过制定快速分级参数标准,对已经开挖的隧道工作面按照隧道围岩分级规范进行分级,并测量其快速分级参数,将围岩分级的结果与其对应的快速分级参数建立BP神经网络的训练集合,从而得到围岩分级模型。最后测量正在开挖隧道工作面的快速分级参数,并提供给模型进行判别,从而达到快速、精确分级目的。通过某隧道围岩样品实例验证,该模型判断结果与实际施工情况吻合,可用于指导施工阶段的隧道围岩快速分级。     

Agronomic application of olive mill wastewaters with phosphate rock in a semi-arid Mediterranean soil modifies the soil properties and decreases the extractable soil phosphorus

Olive mill wastewater (OMW), a by-product of the olive-mill industry, is produced in large amounts in Mediterranean countries. The presence of indigenous phosphate deposits in some countries like Tunisia provides an incentive for direct application or local chemical treatment at low cost to improve the solubility of low reactive phosphate rocks (PRs). The use of naturally occurring low-molecular weight organic acids (LMWOAs) that are present in OMW represents a new perspective in PR research and a possible solution for the recycling of the OMW. The present work was aimed at evaluating, under natural situations (field of olive trees), the effects of agronomic application of OMW (amounts applied: 30, 60 m(3) ha(-1)) with PR (amounts applied: 150 kg ha(-1)) on olive trees soil properties. We measured organic C, nitrogen (N), extractable phosphorus (P), exchangeable calcium (Ca), and exchangeable potassium (K), as well as other properties (pH and electrical conductivity). Our data provide evidence that agronomic application of OMW with PR has important effects on soil properties. Increases in organic C, total N, extractable P and exchangeable potassium (K) were found after the first agronomic application of OMW and PR. These increases were only temporary, following the second agronomic application of OMW and PR, significant reductions were detected in the extractable soil P (19.67 mg kg(-1) in the control soil vs. 8.99 mg kg(-1) in the amended soil). Changes in the extractable soil P could alter plant productivity and plant community structure because shifts in nutriment availability can affect the balance between limiting and non-limiting nutrients.     

长江链子崖危岩区崩滑灾害灾情分析

本文对长江链子崖危岩区崩滑地质灾害灾情进行历史回顾,并分析链子崖危岩体潜在崩滑地质灾害灾情,最后讨论其防治效益。     

软岩煤巷锚杆支护的安全性分析及防治对策

总结了在高地应力条件下巷道治理的基本原则,利用有限元软件对软岩巷道采用锚杆复合支护的安全可靠性进行了分析,并结合实际工程监测,证明了锚杆复合支护的有效性。