Analyses of the Distribution and Nature of the Natural Cementation of Quaternary Sediments: The Case of the Turin Subsoil (Italy)

Abstract

The finding of a remarkable number of stratigraphies from mechanical surveys and water research wells, drilled in the urban area of Turin over the last few decades, has made it possible to reconstruct the geology of the subsoil in great detail. In particular, it has been possible to define the distribution of the cementation in the Quaternary alluvial sediments through geological planimetries that refer to different depths from the ground level. The cementation map of the Turin subsoil can be considered very useful for the planning of future underground works and for the definition of the necessary construction methods. An accurate mineralogical analysis has identified a ''meniscus'' type structure of the cementation; this leads us to believe that the cementation has formed in a vadose environment. The reason for the precipitation of the calcium carbonates is therefore probably due to infiltration of the slightly acidic meteoric water into the subsoil and not to the mixing of water with different temperatures, hardness and pH values, as some authors believed in the past.

Productivity and working costs of modern trench-cutters for the construction of concrete diaphragms in an urban environment

“…Using the data above, the incidences per m 3 are: Amortisation of equipment: 2.5%  3,990,000 e/22 days/100 m 3 = 45.3 e/m 3 Personnel: 36,000 e/22 days/100 m 3 = 16.4 e/m 3 Fuel and lubricants: 1400 e  1.1/100 m 3 = 15.4 e/m 3 Transport and installation: 100,000 e/6 months/22 days/100 m 3 = 7.6 e/m 3 All this leads to an outlay cost (excluding indirect costs, risks, etc.) of about 185 e/m 3 of diaphragm. Should the geology be composed of loose sand and gravel, the daily productivity could rise to about 140 m 3 /day panels.…”

“…Degree of cementation (C1, C2 and C3) of a horizontal section of the Turin subsoil at a depth of 15 m from the surface[3][4][5].…”

Automatic Measurement of Drilling Parameters to Evaluate the Mechanical Properties of Soils

“…Specific energy values of E ≥ 142 MJ/m 3 with s ≥ 40 cm make it impossible to excavate diaphragms with a clamshell bucket shovel (Barla and Vai, 1999). Some diagraphies realized more recently have allowed to validate the developed 3D geotechnical model of the subsoil of Turin (De Rienzo et al, 2008;De Rienzo and Oreste, 2011), identifying cemented layers (with values of specific energy higher than those related to not cemented levels) to a depth of about 10 m from the surface (Fig. 1 and 2).…”

“…One of the indirect methods used to evaluate the geotechnical conditions and stress state of the subsoil (Cardu et al, 2009;Cardu and Oreste, 2011;De Rienzo et al, 2008;De Rienzo and Oreste, 2011;Oggeri and Oreste, 2012;Oreste, 2005) involves the monitoring of drilling parameters through instrumented surveys, generally with destruction of the core. This practice is very flexible and versatile, efficacious and quick in any geological context and it makes it possible to obtain continuous information on the soil or rock not only through analysis of the drilling debris (which can only characterise the ground through chemical-physical and particle size distribution tests), but also through the evaluation of the resistance of the ground or rock to the drilling.…”