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Channel Tunnel Cut and Cover Works (1988–1990)
Published in Alan Powderham, Tony O’Brien, The Observational Method in Civil Engineering, 2020
The escarpment, which has a slope of about 1 in 3, consists of Lower Chalk capped by the harder basal bed of the Middle Chalk. The Lower Chalk, Glauconitic Marl and Gault Clay outcrop in succession at the base of the escarpment. The regional dip is about one degree to the north east, although this may increase near to the escarpment due to stress relief. The Gault Clay is heavily over-consolidated and of high plasticity. Although this clay is generally very stiff or hard, weathering has substantially reduced its strength at the surface and there is a history of instability at outcrops. These presented the risk of significant ground movements being initiated by the construction at the portals. Groundwater within the coombe areas are maintained close to ground level by infiltration from the base of the chalk escarpment. Springs occur at the base of the scarp along the line of the outcrop of the Glauconitic Marl.
Lubrication and soil conditioning for pipejacking and tunnelling in clays
Published in T. Adachi, K. Tateyama, M. Kimura, Modern Tunneling Science and Technology, 2020
E-grade kaolin is an inactive clay of low plasticity, composed of kaolinite mineral. The Panther Creek clay is composed predominantly of montmorillonite, resulting in a very high plasticity and high activity. The exchangeable cations in this clay are mostly divalent, lowering the liquid limit and plasticity of this montmorillonite clay. Gault clay is a natural clay soil of high plasticity, typically composed of predominantly illite, with some kaolinite and montmorillonite. The tests with the clay mineral soils measure the effects of the swelling inhibition agents on the different types of clay individually. This provides a basis for estimating the swelling inhibition of natural clay soils of mixed mineralogy over a wide range of plasticity.
The DINGO database of axial pile load tests for the UK: settlement prediction in fine-grained soils
Published in Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards, 2022
Elia Voyagaki, Jamie J. Crispin, Charlotte E. L. Gilder, Konstantina Ntassiou, Nick O’Riordan, Paul Nowak, Tarek Sadek, Dinesh Patel, George Mylonakis, Paul J. Vardanega
Figure 10 presents data for four different geology categories (London Clay – LC; Gault Clay – GLT, Mercia Mudstone – MMC, and Others). The observed trends are analogous to those in Figures 7–9, with the settlement predictions being somewhat on the conservative side by both methods. An exception is observed with the Mercia Mudstone where there is no apparent bias in the settlement predictions, especially at high loads, and the Gault Clay where the overprediction in settlement is shown to be more considerable (see Figure 10).