加固底板控制软岩巷道底鼓数值模拟和现场试验

 随着开采深度的进一步增加,贵州开磷集团马路坪矿区深部主要开拓及采准巷道支护困难,原有的支护技术与措施失效,巷道返修率高,永久性巷道支护后存在经常性冒顶、片帮、底鼓等现象。针对开磷集团马路坪矿区深部红页岩巷道围岩严重破坏问题,通过现场调查和理论分析,提出加固底板控制巷道底鼓的措施,在原支护方案的基础上设计了3种改进方案。使用离散元软件3DEC对上述原方案及其改进方案分别进行了数值模拟计算,同时选取了100m试验巷道进行现场试验。模拟结果表明,底角锚杆可以切断底板基角部位塑性滑移线从而控制巷道底鼓,浇灌混凝土地坪并铺设钢筋网,能增强底板的韧性,保证底板围岩的整体性,可以大大提高底板围岩抵抗岩块碎胀压力的能力,防止底板围岩开裂挤出。现场测试数据显示联合支护方案减小底鼓量83%,较好控制了巷道底鼓灾害,解决了长期困扰开磷矿山红页岩巷道的支护难题。     

医用钛合金海尔贝克磁场阵列化学磁流变抛光研究

为了提高医用钛合金（TC4）抛光中的精度以及效率,采用基于海尔贝克磁场阵列的化学磁流变抛光方法加工医用钛合金. 利用海尔贝克磁场阵列强化磁场强度,将过氧化氢溶液作为氧化剂来进行抛光加工. 通过仿真模拟对比海尔贝克磁场阵列与常规N-S磁场阵列,改变羰基铁粉的活性来验证实验可行性,研究了加工间隙、主轴转速以及磨粒粒径对工件表面粗糙度以及接触角的影响规律. 结果表明,海尔贝克磁场阵列比常规N-S磁场阵列有更高的磁场强度;采用本文方法抛光的医用钛合金表面粗糙度比单一纯磁流变抛光降低80%;当加工间隙为0.8 mm,主轴转速为400 rad/min,磨粒粒径为1 μm时,可使工件表面达到光滑效果,表面粗糙度最优可达15.5 nm,同时测量出实验组钛合金表面接触角数值多数小于90°. 应用该方法抛光医用钛合金可以得到超光滑表面,表面具有亲水性,符合医用钛合金标准.     

Utilization of waste polyethylene terephthalate as a reducing agent in the reduction of iron ore composite pellets

The increasing consumption of plastics inevitably results in increasing amounts of waste plastics. Because of their long degradation periods, these wastes negatively affect the natural environment. Numerous studies have been conducted to recycle and eliminate waste plastics. The potential for recycling waste plastics in the iron and steel industry has been underestimated; the high C and H contents of plastics may make them suitable as alternative reductants in the reduction process of iron ore. This study aims to substitute plastic wastes for coal in reduction melting process and to investigate their performance during reduction at high temperature. We used a common type of waste plastic, polyethylene terephthalate (PET), because of its high carbon and hydrogen contents. Composite pellets containing PET wastes, coke, and magnetite iron ore were reduced at selected temperatures of 1400 and 1450°C for reduction time from 2 to 10 min to investigate the reduction melting behavior of these pellets. The results showed that an increased temperature and reduction time increased the reduction ratio of the pellets. The optimum experimental conditions for obtaining metallic iron (iron nuggets) were reduction at 1450°C for 10 min using composite pellets containing 60% PET and 40% coke.     

未确知聚类理论在顶板沉降量预测中的应用

 从距离判别的思想出发,对未确知聚类理论中的置信度准则进行优化,并将该理论应用于顶板沉降量预测中。选取岩体抗拉强度、埋藏深度、暴露面积等9 个影响因子,构建顶板沉降量预测的未确知聚类预测模型。根据收集的15 组样本数据确定了未确知测度函数,并利用熵权法计算指标权重,预测得出顶板沉降的分类等级及顶板沉降量。经计算验证,该方法的平均预测误差为7.38%,较模糊数学、灰色关联及神经网络3 种方法有更高的预测精度。为进一步验证其实用性,以辰州矿业沃溪矿区为例,采用该方法对4142 采场进行顶板沉降量预测。结果表明,预测结果与实际监测结果相吻合,证明该方法用于采场顶板沉降量预测是客观合理的,可为矿山安全生产提供决策依据。     

超市购物受到无端检查致人发病是否该担责

编辑老师： 前不久的一天中午,我父亲到超市购物后,在无异常现象的情况下,保安将其拦下,称怀疑他有东西未付款．但检查后未发现问题,双方随即发生争吵。虽经协调,但我父亲余怒未消．在走到卖场北出口时瘫坐在地。热心人拔打了“110”报警电话。警方赶到现场见状后即拨打“120”救护中心,由超市派员将我父亲陪护至医院就诊。     

SEM in situ laboratory investigations on damage growth in GFRP composite under three-point bending tests

Glass fiber-reinforced polymer (GFRP) composites are widely used in low-weight constructions.SEM (scanning electron microscopy) in situ experiments of damage growth in GFRP composite under three-point bending loads are carried out.By summarizing the experimental results of three groups of samples with different orientation angles of fibers,the dependence of mechanical parameters on the orientation angles of fibers are analyzed.The regression analysis show that the peak strengths,the elastic strengths and th...     

水岩作用下岩石亚临界裂纹的扩展规律

采用双扭试件,利用常位移松弛法,分别进行自然状态以及水岩作用下大理岩和混合岩的亚临界裂纹扩展实验,获得2种环境下岩石裂纹扩展速率v与应力强度因子KI的关系,并计算得到亚临界裂纹扩展参数A和n。通过对比,研究水对岩石亚临界裂纹扩展规律的影响。研究结果表明:对于大理岩,其A为自然状态下的8.07×1016倍,n由自然状态下的48.33下降到8.28;对于混合岩,其A为自然状态下的5.45×109倍,n则由自然状态下的60.20下降到21.86,说明对应于同一应力强度因子水平,水作用下的岩石亚临界裂纹扩展速度要快;水的存在使得岩石的断裂韧度KIC明显降低,对于大理岩,自然状态下的KIC为3.0316MN/m3/2,水岩作用后KIC为2.2070MN/m3/2,下降27.19%;对于混合岩,2种状态下的KIC分别为2.0877和1.9398MN/m3/2,下降7.08%。该实验结果可为复杂矿岩的稳定性分析提供可靠依据。     

Influences of 2.5wt% Mn addition on the microstructure and mechanical properties of Cu-Al-Ni shape memory alloys

The influences of 2.5wt% Mn addition on the microstructure and mechanical properties of the Cu-11.9wt%Al-3.8wt%Ni shape memory alloy (SMA) were studied by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and differential scanning calorimeter (DSC). The experimental results show that Mn addition influences considerably the austenite-martensite transformation temperatures and the kind of martensite in the Cu-Al-Ni alloy. The martensitic transformation changes from a mixed xed β₁→β'₁+γ'₁ transformation to a single β₁→β'₁ martensite transformation together with a decrease in transformation temperatures. In addition, the observations reveal that the grain size of the Cu-Al-Ni alloy can be controlled with the addition of 2.5wt% Mn and thus its mechanical properties can be enhanced. The Cu-Al-Ni-Mn alloy exhibits better mechanical properties with the high ultimate compression strength and ductility of 952 MPa and 15%, respectively. These improvements are attributed to a decrease in grain size. However, the hardness decreases from Hv 230 to Hv 140 with the Mn addition.     

Utilization of waste vehicle tires in concrete and its effect on the corrosion behavior of reinforcing steels

The mechanical and physical properties of concrete specimens obtained from replacing natural coarse aggregate with waste vehicle rubber tires at levels of 2vol%, 5vol%, 7vol%, and 10vol% were studied, and the corrosion behavior of reinforcing steels was investigated in these specimens. Corrosion rates were determined by measuring the galvanic current between steel-reinforced concrete specimens both with and without chloride addition. The change in electrode potential of reinforcing steels in these concrete specimens was measured daily for a period of 60 d in accordance with the testing method in ASTM C876. The results show that the use of waste vehicle tires in concrete instead of coarse aggregate decreases the mechanical strength of the specimens, and increases the corrosion rates of the reinforcing steels embedded in the concretes.     

基于GIS与随机森林的巫山县滑坡易发性区划

【目的】对三峡库区典型县域巫山县进行滑坡易发性区划,为该县滑坡灾害风险管理和城市建设规划提供科学参考。【方法】选取地形地貌、地质条件、环境条件、人类工程活动及诱发因素共5个方面下的22个因子作为滑坡易发性影响因子,结合研究区963个历史滑坡数据,以30m精度栅格建立滑坡影响因子地理空间数据库;进一步在地理空间数据库中,基于全体样本(包括滑坡点与非滑坡点),采用十折交叉验证选择训练和测试数据集;随后,利用随机森林进行模型训练,用训练好的模型对整个研究区进行全域滑坡易发性仿真分析,将结果划分为低、较低、中、较高、高5种易发性等级。【结果】混淆矩阵的准确率高达100%;受试者工作特征曲线训练数据、测试数据和全体数据的曲线下面积值均为1.000;高易发区面积占整个县面积的5.83%,而区内历史滑坡数占该县历史滑坡总数的35.72%;高程、多年平均降雨量、兴趣点核密度这3个因子对滑坡的发生有更大贡献。【结论】基于巫山历史滑坡数据和随机森林构建的滑坡易发性模型具有较高的准确性、稳定性以及良好的预测功能。