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双弦控制法,是自切点确定以后,再确定短弦“a”的长度,并计算出第一条短弦的方向(弦切角)及长弦“b”的长度,然后由四人两把钢尺利用两弦的长度来完成曲线的测设定线工作。双弦控制法操作简单,使用方便,易掌握,精度高。本文就双弦控制法的基本原理进行了浅析:对于测设方法及步骤作了叙述。当曲线半径确定后,关于两弦长度及弦切角“β”的确定、切点位置的确定(分弯道顶点能相交在一平面内与不能相交在一平面内两种情况)分别进行了推导演算。为使用方便起见,列出了半径“R”短弦“a”长弦“b”及“tgβ”的关系表,以期能够保证工程质量,节约时间,在没有经纬仪的情况下,解决基层科技人员铺设曲线工作中的困难有所帮助。
The double-string control method determines the length of the short string “a” after determining the starting point, and calculates the length of the first short string (chord cut) and the long string “b” Two steel ruler to use the length of the two strings to complete the curve of the test set the line work. Double-string control method is simple, easy to use, easy to grasp, high precision. In this paper, the basic principles of double-chord control method are analyzed: the methods and steps for measuring set out. When the radius of the curve is determined, the determination of the tangent point “β” and the determination of the chord cut angle “β” of the two chord lengths (the two points can be intersected in one plane and can not intersect in a plane) Derive calculation. For ease of use, a list of the relationship between the long strings “b” and “tgβ” of the short “a” chords of “R” is listed, with a view to ensuring the quality of the project and saving time. Without the theodolite, Laying the curve of the difficulties in the work of help.