TUNNEL BENEATH THE THAMES

Press, Volume LXXII, Issue 21715, 24 February 1936, Page 15

TUNNEL BENEATH THE THAMES

ENGINEERS MEET GREAT DIFFICULTIES

£3 t ooo,ooo> TO BE SPENT

(r»ou ov» on coEEJt»rbin»«rt.)

« LONDON, January 26. Further dedans are announced by the Ministry of Transport of the £/3,0040D0 tunnel which is to be constructed under the Thames between Purfleet (Essex) and Dartford (Kent). The construction of the tunnel will be Under the direct control of the Ministry, which states, that it will be an event in engineering history. The length will be more than a mile, exclusive of the open approaches, which will be constructed with )a maximum gradient of one in 28.

Close investigation of the plans that were originally considered showed that the construction of the tunnel might present insuperable difficulties and possibly involve loss of life. It is only after long investigation that a solution of the problem has been found.

The formidable engineering difficulties involved, adds tthe Ministry,, make it all the more remarkable that it has been possible to provide a carriageway of 20 feet, with a Eatrol path on each side protected y a hand-rail. Ventilation will be provided by fresh air driven through a duct at the top of the tunnel, whence tubes wQI convey it to ori-

- Jv3 flees placed at intervals along kerb line, the foul air '■behw}«x? t ;V. tracted from the main -tNjti£jd*<£••• M^f. The tunnel wm constaictecl by a shield driven by conipi«we4'«Wirl from shafts more-than ' 100 '• feet deep on.each fide of the Thames. The top of the tunnel at its lowest point will be 80 feet below, high water level, and the upper part will be in. the form of a> semi-circle of 30 feet outside diameter, -with ate flattened lower Jialf.; ).;•• • > - &"y . Connecting of eommunica-'' tion between th 6 tunnel arid the terial roads on each side have beeri carefully planned.. The north ap- ' proach will connect to the PurfleetGrays road. The approach roads will ultimately.be «irt<uided r norjth- v wards to the London-Southehd road,. cross the Xondon-Chelmsford road .. and couple up with the.. NorthVQr?, bital road* , ■* - The south approach will connect to the Dartford by-pass and ulti- -,- mately be extended southwards to - the London-Folkestone road and the' London-Hastings road at I»olhili; The . population oh both sides of the Thames near the proposed tunnel increased by 29 per cent in the 10 years from 1921-1931, and reached a ■ y total of 2,250,000. •■. ', T