Horizontal Directional Drilling technology is widely used in urban underground pipe laying engineering.
在非开挖工程中，水平定向钻进技术广泛应用于城市地下管线铺设工程。
So the establishing of(horizontal) control datum with appropriate precision standards systematically is the precondition to make sure the precision of ballastless track laying.
系统建立适宜精度标准的平面控制基准，是保障无碴轨道铺设精度指标顺利实现的前提。
The calculation formulas of yarn laying angles as well as critical values at vertical and horizontal planes were also deduced in this paper.
推导了确立地、面纱垫纱纵、横角的一般值与临界值公式。
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