Review of Studies on Retaining Wall's Behavior on Dynamic / Seismic Condition
Current theories, experimental investigations and numerical findings for retaining walls subject to dynamic excitations are reviewed. Brief features of each method, and experimental and numerical methods are introduced and compared. Tables are listed after each section for a clear and brief view of methods in a categorized manner. Conclusive comments plus current concerns and future expectations of this area are made at last. This review aims at shedding light on the development and concepts of different researches in dynamic retaining wall design and analysis.
Earthquake-Induced Soil Pressures on Structures
The earthquake-induced pressures on soil-retaining structures are investigated. The study was motivated by the lack of suitable earthquake design data for relatively rigid structures on firm foundations in situations where the foundation, structure and retained soil remain essentially elastic. Pressures and forces on the walls of a number of idealized wall-soil problems are analyzed. The solutions obtained are evaluated for a range of the important parameters to give results useful for design. In the idealized problems the soil is represented by an elastic layer of finite length bonded to a rigid foundation or rock layer. The wall or structure is represented by a rigid element resting on the rock layer and is permitted to undergo rotational deformation about the base. The mass or moment of inertia of the structure and its rotational stiffness are included as parameters in the idealization. Static and dynamic solutions are obtained using both analytical and finite element methods. Solutions are evaluated for the assumption of perfectly rigid behavior of the wall. The general solution for the deformable wall case was developed by superposition of the solution for the perfectly rigid case and solutions derived for displacement forcing of the wall structure. The assumption of linear elastic behavior of the wall- soil system is likely to be approximately satisfied in situations where a building or other large civil engineering structure is founded on firm soil or rock strata. In contrast to the linearly elastic assumption made in this study, the commonly used Mononobe-Okabe method employs the assumption of sufficiently large wall deformations to induce a fully plastic stress condition in the soil. It was concluded that both the elastic theory and the Mononobe-Okabe method have valid applications in the design of wall structures subjected to earthquake motions, but that because of significant differences in the solutions obtained from each method, care is required in selecting the most appropriate method for a particular situation.
Correlation of the Upper Cretaceous White Chalk (Turonian to Campanian) in the Anglo-Paris Basin
Using key lithological, biostratigraphic and geophysical borehole-log markers a correlation of the Upper Cretaceous Chalk stratigraphies across the whole Anglo-Paris Basin has been achieved. A common lithological marker bed stratigraphy applies and key fossil markers (inoceramids, Micraster and Echinocorys ) are consistently related to the same lithological markers throughout the basin. The major lithological changes consistently occur at the same levels but are not necessarily equally strongly developed. The magnificent dip section along the French Channel coast between the Somme and the Seine, and the inland sections at Precy-sur-Oise and Verlin (Loiret) illustrate the influence of long-lived tectonic lines on Chalk sedimentation history recognised by: (i) rapid thickness variations; (ii) channel flooring hardgrounds and associated anomalous bedding dips: (iii) stratigraphically anomalous infills of channels which may be metres to kilometres across; (iv) redeposited chalks containing abundant Bathichnus paramoudrae ; (v) tectonically induced slumps and slides with flint and chalk shatter beds (palaeoseismic horizons). These features are found along may axes including the Anticlinal du Bray at Precy and Dieppe, the Anticlinal de Margny-les-Compiegne at Nourard le-Franc and Le Treport (the Bresle Valley Axis) and the Fecamp and Verlin fault systems. The ‘events’ recognised along these axes link with similar events recognised in Sussex (e.g. Kingston Anticline), on Portsdown, at Culver Cliff, Isle of Wight (Sandown Pericline) and on the Weymouth Anticline (White Nothe). Such events are common in the high Turonian, low Coniacian, basal Santonian, and the low and mid Campanian. The recurrence of key marker beds dominated by a particular trace fossil association or sequence, Bathichnus-Thalassinoides suevicus-Zoophycos associated with major changes in lithology, micro and macro-fauna indicates more widespread ‘oceanographic’ cycles of transgression and regression related to Atlantic opening.