How to design an underground station using a time machine
Channel: Deryck Chan
Date: 2020-08-05

"Long-term basement heave in over-consolidated clay, or how to design an underground station using a time machine"

Cambridge University geotechnical seminar by Deryck Chan, with introduction by Prof. Gopal Madabhushi

Synopsis: The Earth is a giant sponge. This is particularly noticeable when underground spaces are constructed in places with stiff clay, like London and Cambridge. When a large basement is excavated in stiff clay, the removal of soil overburden causes the remaining soil to swell slowly and push the new basement upwards, in a phenomenon known as “long-term heave”. The underlying stress-strain relationships are highly non-linear and these movements often continue for many years after the end of construction, causing significant conservatism in design. This seminar will present a series of physical experiments of basement heave that used the technique of geotechnical centrifuge modelling to reduce the size of the model and speed up the process of heave while preserving the mechanisms of deformation. The experimental results will be compared with finite element simulations of the same prototypes and with 21 years of monitoring data from a site in London, to discern the mechanisms of heave and propose improvements to the methods of basement structure design.

Recorded live on 23 July 2020
Original talks.cam event listing: http://talks.cam.ac.uk/talk/index/149950

00:00 Introduction by Prof. Gopal Madabhushi
03:22 Welcome to our underground interchange
07:15 What is basement heave?
15:20 Give me a time machine!
30:03 A self-fulfilling prophecy
39:43 Back to the real world
44:35 Upgrade the design methods!
49:11 Q&A