Abstract
Deep excavation and tunnelling works in city centres always bring some risks to surrounding structures, especially in the case of old town centres, where the technical condition and structural stiffness of historical buildings is rather doubtful. When the new desired excavation depth goes deeper than the foundation of the surrounding buildings or when tunnelling works are conducted directly under them, the existing objects are subject to stress, vibrations and displacements imposed at almost every stage of building the new construction. The presented paper outlines, on the basis of the authors’ experience, the typical damages appearing during the supporting wall construction (sheet pile driving, piling and formation of diaphragm walls) and tunnelling works. Other damages appear due to soil mass unloading (caused by excavation stages) and horizontal loading during pre-stressing of struts or ground anchors. The selected case studies of steel sheet pile wall installation is given with regard to typical failures caused by an unplanned excavation and its impact on neighbouring structures.
Highlights
Every project starts from an outline proposal and preliminary design
That leads to a so-called “observational method” of design, where the design model may be currently updated on the basis of displacement monitoring. An example of such procedure was given by Gorska in articles [7, 8], on the basis of steel sheet pile wall design
Recent developments can be found in works of Drusa [9], Bednarski [10] and Muszyński [11], where the suitability of terrestrial laser scanning for the control of deep excavation support was examined
Summary
Constant development of town centres, accompanied by earthworks and tunnelling, brings about many problems that need resolving. Another problem refers to constructing underground storeys below the level of groundwater. In the typical case of old cities in river valleys such “hoarding off” the excavation and cutting off groundwater leads to temporary or permanent disturbances of groundwater flow and possible local swellings. Contemporary technologies make it possible to protect vertical fault and simultaneously to cut-off groundwater inflow by means of steel sheet pilings, diaphragm walls or secant pile walls. Many examples of case studies concerning the geological risks related to tunnelling works can be found in the references
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