Lateral Pressure of Poured Concrete: Arguments from Ultra-Deep Diaphragm Wall (120 m) Construction

Abstract

Formwork lateral pressures are critical with respect to engineering safety, and laboratory tests are often limited by time, height, etc. Formwork lateral pressures are related to early concrete fluid behavior (e.g., thixotropy). In this paper, we propose the use of ultra-deep underground diaphragm walls instead of formwork for conventional lateral pressure testing. During the construction process, three measurement points were set up in an ultra-deep diaphragm wall at −40 m, −80 m and −100 m. The concrete was divided into 22 casts, and the development of lateral pressure and the effect of time on lateral pressure were observed under each of the casts. We found that the characteristic height of all three measurement points was approximately 21 m. The average casting speed for this test was 16.846 m/h, with the fastest speed of 32.148 m/h. A time-dependent phenomenon of rapid rise and fall in lateral pressure with each casting was observed. This method provides a new way to conceptualize formwork lateral pressure, with the advantages of long testing time, high casting height and multiple tests, not only for formwork lateral pressure but also for early age thixotropy measurement of concrete.