基于Rockfall数值模拟的边坡落石防护网修复加固方案研究∗

某水电站尾水支洞边坡多次发生落石灾害,原被动防护网已发生局部破损,严重威胁着尾水支洞施工期和运行期的安全,需对原防护网进行修复加固。由于山体陡峭、地貌复杂,人工调查无法确定落石源,采用高精度无人机航摄初步排查出四处可疑危险源区域,利用Rockfall 软件进行落石轨迹模拟计算,通过对比分析计算成果与观测到的落石落点位置与威胁区域分布情况,反分析确定了两处落石源。在此基础上,根据落石源的落石运动特征,复核分析了原防护能力不足的原因,发现原防护网的能级和高度不足是导致落石灾害发生的主要原因。通过提高防护网的能级和高度,提出了原位修复和增高加固两种方案。研究结果表明：两种方案均能有效减小落石威胁区域面积、降低落石率、改善运动特征参数。其中增高加固方案的防护效果更加显著,落石被全部拦截,落石弹跳高度和动能的最大值分别降低了69.64%、66.02%。对被动防护网破损部位的修复加固,综合考虑现场实际情况与落石模拟计算成果进行修复方案设计更为科学合理。研究成果可为该工程的落石防护方案提供科学依据,为类似工程设计与落石分析提供参考。     

Preparation of high concentration polyaluminum chloride by chemical synthesis-membrane distillation method with self-made hollow fiber membrane

A method of direct contact membrane distillation (DCMD) with a self-made hollow polyvinylidene fluoride membrane was applied to prepare high concentration polyaluminum chloride (PACl) with high Al_b content based on chemical synthesis. The permeate flux and Al species distribution were investigated. The experimental results showed that the permeate flux decreased from 14 to 6 kg/(m²·hr) at the end of the DCMD process, which can be mainly attributed to the formation of NaCl deposits on the membrane surface. The Al_b content decreased slightly, only from 86.3% to 84.4%, when the DCMD experiment finished, correspondingly the Al_c content increased slightly from 7.2% to 8.5%, and the Al_a content remained at 7% during the whole DCMD process. A PACl with Al_b content of 84% at total aluminum concentration 2.2 mol/L was successfully prepared by the chemical synthesis-DCMD method.