长距离输水工程采用大口径PCCP管的安全防护对策

Countermeasures for safety protection of large-diameter PCCP pipeline for long-distance water conveyance project

针对输水管道工程中PCCP管材爆管事故引发对PCCP管耐久性的担忧,对相关管道爆管案例进行了归纳研究,结果表明爆管的主因是预应力钢丝断丝。微观分析可知钢丝断丝是由于快拉拔引起晶格缺陷、阴极保护过负、氢脆等因素导致;宏观分析其原因是由于砂浆保护层开裂、有效外防护缺失导致钢丝腐蚀破坏。通过对比研究国内外有关规范差异、管材设计考虑的内外服役环境、管芯混凝土和砂浆制造工艺,以及已建工程不同外防护效果等方面,提出了PCCP管道安全防护对策如下:(1)标准规范需细化和设计优化;(2)提高管芯质量和改进砂浆工艺;(3)做好有效外防护,如三油两布和适宜厚度的环氧煤沥青涂层措施;(4)慎重选择阴极保护等措施,由此可提高PCCP管道的承载力和耐久性。与此同时,还需做好运行监测和检测,并及时进行管道修补及换管工作,从而降低爆管风险。

Aiming at the impact from the pipe-bursting accident of PCCP(pre-stressed concrete cylinder pipe)pipe line caused by pre-stressed steel wire braking occurred in water conveyance pipe line project on the durability of it,the causation of the steel wire braking is analyzed herein through summarizing and studying the relevant pipe-bursting cases.The study result shows that microscopically,the steel wire braking is caused by the factors of lattice defect from rapid drawing,over negative of cathode protection,hydrogen embrittlement,etc.,while the steel wire braking is macroscopically caused by the corrosive destruction of wire from cracking of mortar protective layer and lack of effective external protection.Through the comparative study made in the aspects of the differences among the relevant specifications at home and abroad,the consideration from the pipe material design on the internal and external service environments,the pipe-core concrete and pipe-core mortar preparing technologies,the comparison among different external protection effects of existing projects,etc.,the relevant PCCP pipeline safety protection countermeasures are put forward:(1)refining the relevant criteria and specifications and optimizing the relevant design;(2)enhancing the quality of pipe-core and improving the preparing technology of mortar;(3)making effective protection well,i.e.three asphalt layers and two cloth layers as well as epoxy coal tar pitch coating with suitable thickness;(4)carefully selecting the measures of catholic protection,etc.,so as to improve the bearing capacity and durability of PCCP pipeline.Additionally,it is necessary to do the operation monitoring and detection well and make pipe repairing and replacing in time for lowering the risk of pipe-bursting.