关井过程防喷器胶芯的冲蚀性能研究

目的预测井涌或井喷发生时关闭防喷器闸板对胶芯的冲蚀,为评估关井后胶芯的密封性能提供依据。方法首先依据橡胶试件的冲蚀试验,基于LM优化算法反演分析确定丁腈橡胶的冲蚀模型参数,将所确定的冲蚀模型通过UDF嵌入Fluent软件,建立关井过程中防喷器半封闸板附近流场的数值模型,计算密封胶芯的冲蚀性能,研究关井全过程胶芯材料去除量与关井时长的变化规律。结果得到了丁腈橡胶材料的改进Finnie冲蚀模型参数,该冲蚀模型预测的试件冲蚀率随冲击角的变化与试验数据的最大相对误差仅为5.77%,可用于模拟丁腈橡胶构件的冲蚀性能。在防喷器关阀过程中,携岩钻井液对胶芯的冲蚀主要发生在端面边缘处的岩屑高速碰撞区。胶芯的冲蚀率与钻井液的含砂量呈线性正相关,与钻井液的流速呈非线性正相关。随着闸板开度的减小,冲蚀率呈现指数增长。在文中的参数条件下,当闸板开度分别为104、26、6 mm时,胶芯的材料去除率分别为1.52、5.22、28.3 mm^(3)/s,表明在关井后期闸板即将关闭前,胶芯受到的冲蚀最严重。在关井全过程中,胶芯的材料去除量随着关井时长的增加而增加,关井时长分别为3、8 s时对应的胶芯体积去除量分别为5.04、13.43 mm^(3)。结论在井涌或井喷发生时,关闭防喷器闸板的时机和时长对于处置事故至关重要,需综合评价关井时长对井口动载荷和胶芯冲蚀量的影响,制定科学的关井预案,以保障井筒、地面装备和施工人员的安全。

Distribution and Transport of Residual Lead and Copper Along Soil Pro?les in a Mining Region of North China

Residual heavy metals are commonly considered to be immobile in soils,leading to an underestimation of their environmental risk.This study investigated the distribution and transport of residual heavy metals along soil pro?les,using the Xiaoqinling gold mining region in North China as a case study.Soil samples were collected at three depths from three locations near the tailing heap.The speciation of copper(Cu) and lead(Pb)(exchangeable,carbonate-bound,Fe-Mn oxide-bound,organic matter-bound,and residual fractions) was determined using a sequential extraction procedure.The residual fraction's morphology was observed using scanning electron microscopy(SEM).Results showed that metal fraction distributions along the soil pro?les were in?uenced by each fraction's mobility.Residual fraction with high chemical stability can not be transformed from or into other fractions.This led to the conclusion that the high concentration of residual metals in soils mainly resulted from residual fraction transport.The SEM analysis showed that ?ne particles(submicrons) were mainly attached to large particles and were likely released and transported by water?ow.The more sorptive fractions(non-residual fractions) were mainly retained in the top soil,and the more mobile fractions(residual fraction) were mainly leached to the deep soil.Cu and Pb concentrations in the residual fraction decreased slightly and those in the non-residual fractions decreased signi?cantly with soil depth.These suggest a relatively higher residual metal mobility along the soil pro?les.Therefore,residual metals can be transported in soils and their environmental risk can not be ignored in assessing soil contamination.

一起乘客坠落至电梯轿顶事故的原因分析及预防措施

1事故概况2020年7月12日,某市一小区住宅楼内发生一起乘客(王某)坠落至电梯轿顶,并最终抢救无效死亡事故。据现场监控视频显示,当天晚上王某从21楼进入电梯轿厢后按下1楼按钮,当轿厢到达6楼的时候停梯开门,王某随之走了出去,又迅速转身返回至层门前,此时电梯层、轿门已开始关闭。