在建隧道排水系统结晶堵塞试验

Experimental Study on Scaling and Clogging in Drainage System of Tunnels Under Construction

为了探究在建公路隧道排水系统结晶堵塞机理,分析隧道排水系统结晶堵塞的发展过程,自主研制了可模拟隧道初支混凝土、地下水渗流过程、隧道排水系统的试验装置系统。通过该系统模拟了富水隧道排水系统渗流结晶过程;通过检测隧道排水管排出溶液的pH值、总碱度、Ca^(2+)浓度以及排水管内的结晶量等,研究了速凝剂掺量、地下水水质对生成结晶体的影响。结果表明:结晶体的主要成分为CaCO_(3),结晶体中的钙元素主要来源于水泥;地下水的渗流过程会致使混凝土中的Ca^(2+)析出,最终流出排水管或以CaCO_(3)结晶体形式沉积在排水管内;排水管流出溶液的pH值和总碱度变化曲线基本呈现先快速下降,后缓慢下降趋于稳定的趋势,结晶体生成的溶液环境pH值和碱性较高。对于一般水质:4种速凝剂掺量条件下排水管流出溶液pH值变化范围在11.4~12.6之间,初始总碱度最高达12650 CaCO_(3)mg·L^(-1),稳定后溶液碱度均大于500 CaCO_(3)mg·L^(-1);对于碳酸氢钠型水质:4种速凝剂掺量条件下pH变化幅度在9.62~12.25之间;初始总碱度最高达1252 CaCO_(3)mg·L^(-1),稳定后溶液总碱度均大于550 CaCO_(3)mg·L^(-1);0%和6%速凝剂掺量下结晶体生成量明显大于10%和20%掺量,10%掺量下结晶体生成量最小;碳酸氢钠型水质条件下,水泥水化产物Ca(OH)_(2)会直接和HCO_(3)^(-)发生化学反应,生成CaCO_(3)结晶体,较一般水质结晶体的生成速率更快,生成量更多。

To explore and analyze the scaling and clogging mechanism and development process of Underground water in the drainage system of a highway tunnel Under construction,an experimental system was designed that comprised of primary support device,seepage device,and tunnel drainage system.Using this system,the seepage process of groundwater in water-rich tunnels could be simulated.Subsequently,by determining the pH value,alkalinity,concentration of calcium ions in the outflow solution of the drainage pipe,and amount of scaling in the drainage pipe,the effects of different dosages of accelerator and two types of groundwater scaling were explored.The results indicate that the main component of scaling is calcium carbonate,and the calcium element in the scaling is primarily derived from the cement in shotcrete.The seepage process of groundwater causes the calcium ions to separate from the shotcrete and flow into or deposit in the drainage pipe in the form of calcium carbonate scales.The pH and total alkalinity curves of the effluent solution from the drainage pipe show a trend of rapid decline followed by a slow decline that tends to be stable.Generally,scale formation occurs in environments with high alkalinity and pH value.For normal water,the pH value of the effluent solution from the drainage pipe ranges from 11.4 to 12.6 for four kinds of accelerator dosages,and the initial total alkalinity is approximately 12650 CaCO_(3)mg·L^(-1).The alkalinity of the stable solutions are higher than 500 CaCO_(3)mg·L^(-1).For sodium bicarbonate water type,the pH value of the effluent solution from the drainage pipe ranges from 9.62 to 12.25 for four kinds of accelerator dosages.The initial total alkalinity is up to 1252 CaCO_(3)mg·L^(-1),and the stable alkalinity of the solutions are higher than 550 CaCO_(3)mg·L^(-1).At 0%and 6%accelerator dosage,the amount of scaling is greater than 10%and 20%,respectively,and the minimum amount of scaling is at 10%accelerator dosage.In sodium bicarbonate water type,Ca(OH)_(2) reacts directly with the bicarbonate radical to form calcium carbonate scales.The scale formation rate is higher for sodium bicarbonate water type in the drainage pipe,and the amount of scales is more than that of general water type.