tag:blogger.com,1999:blog-2907980016894811549.post1126161889433703148..comments2024-03-28T13:35:40.706+00:00Comments on HPANWO Voice: Stonehenge TunnelBen Emlyn-Joneshttp://www.blogger.com/profile/13858990047274822000noreply@blogger.comBlogger1125tag:blogger.com,1999:blog-2907980016894811549.post-56475804410444523512017-01-16T20:41:39.566+00:002017-01-16T20:41:39.566+00:00Interestingly, background technical information on...Interestingly, background technical information on the Stonehenge tunnel indicates that the chalk is atypical of the chalk deposits found elsewhere in the south of England, containing as it does loose sand and silt layers and radioactive phosphates (radon) leading potentially to tunnel collapse and groundwater contamination. (Thus the tunnelling method (EPB) is relatively very expensive compared with simpler, unsupported tunnels in chalk.) Laurencenoreply@blogger.com