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测压管是渗流观测中最基本的手段,通常采用单层测压管,其做法是在钻孔内垂直埋入一根钢管,底部为进水段,在此段以上大都不做封孔(见图1),测得的水位即认为是该处的潜水位.密云水库最初观测均采用此法,但发现问题很多,主要是孔内水位实际上并不代表周围真正的潜水面,二者相差很大.为此,1968年以后陆续将一批单层测压管改建为多层测压管.新的多层测压管观测表明,沿铅垂线上各点的水位并不相同,一般是上部水位高于下部,也有少数相反.而旧式的单根测压管实际上只是反映了某种混合假水位,有时比真正的潜水面要低10多米.只有在渗透比降很缓,介质比较均匀的情况下,这种单根测压管才能
Piezometric tube is the most basic means of seepage observation, usually using a single piezometric tube, the practice is buried in the borehole perpendicular to a steel pipe, the bottom of the water section, most of this section do not seal ( See Figure 1), the measured water level is considered to be the diving position here Miyun Reservoir were initially observed using this method, but found a lot of problems, mainly because the water level inside the hole does not actually represent the real diving surface around the two A great difference.Therefore, after 1968, one after another will be a number of single-layer piezometric tube into a multi-layer piezometric tube.The new multilayer piezometer tube observations show that the water level along the plumb line is not the same, Usually the upper part of the water level is higher than the lower part, there are a few opposite, while the old single piezometric tube actually reflects only some kind of mixed false water level, sometimes more than 10 meters lower than the real diving surface.Only when the infiltration ratio is slow, Medium more uniform case, this single piezometer to