季节性冻土层地浸井场管道防冻保温技术研究

Study on anti-freezing technology of in-situ leaching uranium well field pipeline in seasonal frozen soil area

某采铀工程点最大冻土深度高达2.5m,为解决管道防冻保温这一工程设计中的难点问题,对现场进行了冻土层温度监测和浸出液冰点温度测定等试验研究。结果表明,1.0m深处以上土壤从当年10月份开始冻结,冻结期5个多月;1.5至2.0m深处土壤从次年1月底开始冻结,冻结期2个多月;2.5m深处只在次年2月中旬出现过短暂的冻结期;距地表0.5、1.0、1.5、2.0、2.5 m处土壤最低温度分别为-7.5、-4.5、-1.5、-0.5、0.0℃左右;管道内溶液温度为9℃,冰点温度为-4℃,在埋地管道内以2m/s左右的流速常年流动,运行期间冻土层中会形成一个以管道为中心的保温圈。推荐该地浸井场管道采用浅埋不保温(最大底界埋深1.5m)方案铺设,可在保证管道冬季平稳安全运行同时,节省管沟工程量和投资。

One in-situ leaching uranium project is located in seasonal frozen soil area. The maximum depth of the frozen soil layer is 2.5 m. To solve anti-freezing and thermal insulation problem of well field pipeline in the design engineering works, on site temperature monitoring of frozen lays and freez- nt measurement of leached solution etc. test were carried. Experimental results indicate that ~ve 1.0 m beneath the surface begin to get frozen in October and this status last more than 5 3. Soil at 1.5 m and 2.0 m down the earth start to get frozen in the next January, which lasts 2 more. However, soil at 2.5 m down the surface only become frozen shortly in the mid Febru- ary. The lowest temperature of soil at 0. 5,1. 0,1. 5,2. 0, and 2. 5 m down the surface are -7. 5, -4.5,-1. 5, - 0. 5,0. 0 ℃ respectively. The temperature of the liquid within the pipeline during transportation is 9℃ while the freezing point of the liquid is --4 ~C. A pipeline centered melting-circle which is asymmetrical in orientation vertical to landscape but symmetrical in orientation parallel to landscape become into being in the winter when the pipeline is transported liquid. The liquid with a speed of 2 m/s flows in the pipe beneath the soil all the time, so it never gets frozen. Above all, the anti-freezing technology for pipelines and conformation of the depth of pipeline ditching become the key issue of engineering design. The pipeline laying scheme by shallow burying with no heat preserva- tion method was put forward. The largest burial depth is 1.5 m. By application of this scheme, the investment on pipeline laying works and pipe ditch engineering was minimized.