Paolo Croce

The Theory of One-Dimensional Consolidation of Saturated Clays: III. Existing Testing Procedures and Analyses

The successful calculation of the progress of consolidation requires that both the theory used to model the field problem and the material properties used by the theory must be appropriate and suitable. Thus the testing procedure must provide reliable and consistent information on the material behavior. Further, the test procedure must be accompanied by methods of analysis that will produce values of the material properties that are appropriate to the theory. This paper presents a summary of the existing laboratory methods that are used to determine the consolidation properties of soils. Emphasis is placed on the analysis of the test data. It is shown that all the methods that are currently used contain inherent simplifying assumptions. These methods are restricted in their applicability to problems where linear or constant material properties or both are good approximations to real behavior.

Design of jet grouted excavation bottom plugs

AbstractA methodology for cost-effective design of jet grouted water-sealing bottom plugs is presented in this paper. These massive barriers, made of partially overlapping jet grouted columns, are required to ensure temporary waterproofing to excavation areas and adequate uplift resistance against water loads. Therefore, the proposed calculation procedure simultaneously focuses on the structural performance and continuity of the plug. The design may be optimized by considering the possibility of reducing column length, performing injections only in the lower part of the plug, and leaving the upper part of the plug untreated. The reduction in column length may then result in a very slender slab, and a structural check has to be performed to avoid tension fracturing or overall structural collapse. Additionally, in spite of strict controls, jet grouted columns are never perfectly cylindrical or exactly aligned along their prescribed position, and thus the plug may present imperfections. Statistical evaluatio...

JET-GROUTING PERFORMANCE IN TUNNELLING

The paper focuses on the role of jet grouting on tunnel support, although the influence of supplementary techniques is also considered. For this purpose, experience gained from two well documented case histories (highway tunnels in Italy) is presented. Reported observations and experimental data have been selected in order to help in the identification of proper design limit states. Jet grouting has proven to be quite effective, allowing tunneling in very difficult conditions, but some failures have also been recorded. Failure mechanisms can be classified according to three different modes: excavation face failure, canopy tip failure, provisional lining failure. With regard to the control of settlements, jet grouting has proven to be very effective but some ground uplift can be temporarily induced by soil treatment.

Seismic Microzonation of the Cassino Plain

Thanks to its favourable hydrogeological conditions, Cassino is one of the most studied sites of Central Italy. More than two hundred soil borings, some of them reaching depths as high as 100 m, have revealed a subsoil characterized by a calcareous platform and post-orogenetic series forming a tectonic basin filled by lacustrine and volcanic deposits. Together with the already available data, a number of geological, geotechnical and geophysical data have collected to study at a very detailed scale the seismic response of the site. Among them, a series of HVSR (horizontal to vertical spectral ratio) measurements have been performed to estimate the natural frequency of oscillation of the more deformable deposits. The combination of these data with the information given by the deep boreholes, permitted to rebuild the geological complexities of the tectonically driven seismic bedrock, outcropping continuously at east and west of the basin. This study forms the basis for mono, bi and three-dimensional numerical analyses aimed at predicting local amplification effects.