What is the dotted line in the rectangular straight concrete sewage inspection well diagram? What is the circle drawn by the dotted line?

a: the dotted lines on the east and west sides of this drawing are: D3 and D, 4 walls in sewage pipe 2. The double-8 dotted line at the lower left L angle is that the top of the M tube is connected to the K tube. If you check the dotted line of the circle, you should look at section 2-2. Wjianjun63' s answer is "6. The circle drawn by the dotted line is well D, O (also called R as T-hole 3 or inspection hole )," if the answer is correct. The double 3 dotted line of the circle in the last 6 atlas is wrong, P! It should be a solid line from all angles of top view drawing and map recognition. M8 is used between D4 and D sewage pipes on the east and west sides. 4 water, 4 mortar, MU4 brick, painted launder, there is really nothing else. "The double 5 dotted line of circle in the graph set is wrong I!" It should be a double 6 solid line, and it is indeed a round well T-port R. Ueulr Chen ●p Er у UW κ C〃〃E.