Following the interesting article on Folkestone Warren (GE Nov 2013) I felt compelled to write to you but I thought it wise to speak to Eddie Bromhead first as he seemed to be the main source.
There were two things that particularly bothered me. First the paragraph: “It is reported that soil mechanics specialist Karl von Terzaghi visited the site in 1939, but concluded that it wasn’t a landslide and the problems were caused by chalk dissolution.” To refer to Terzaghi as a “soil mechanics specialist” seemed odd as he was in fact the person who laid the foundations for our whole discipline.
Then the remark that he “concluded that it wasn’t a landslide” was very odd as that was the very reason that he was consulted by George Ellison, the chief engineer of the Southern Railway following the failures in 1936 and 1937 (He had previously visited the site in September 1938). The story is recounted by Richard Goodman in his biography of Terzaghi, The Engineer as Artist.
At the time of his visit Terzaghi did not fully understand the failure mechanism but Goodwin (page 177) says that the reason dawned on him in December 1940 that “the instability of the entire section of the coast must be caused by unusually high water pressures in the pervious sandstone (the lower greensand formation)”.
The other point is the reference to “dissolution” which occurs on page 14 of Terzaghi’s report. As I understand it, he was trying to explain what happened to the large mass of “chalk debris” overlying the Gault Clay which is a considerable distance above current sea levels. This can be seen in figure 8 of his 1950 paper “Mechanism of Landslides” which was reprinted in the 1960 volume From Theory to Practice in Soil Mechanics that celebrated Terzaghi’s contribution to our profession.
Ron Williams, firstname.lastname@example.org