ANALYSIS OF GEOTECHNICAL MODELING OF THE SOIL INSIDE THE BUNGE PLANT LOCATED IN PORTO CORSINI, RAVENNA

CLIENT: Bunge
LOCATION OF INTERVENTION: Municipality of Ravenna, Porto Corsini locality.
SERVICES RENDERED: geotechnical modeling and load bearing calculations of foundations
BEGINNING/END OF WORKS: 2014

PROJECT DESCRIPTION

An accurate geotechnical model of the ground inside the Bunge plant located in Porto Corsini in the Municipality of Ravenna has been elaborated.
For this purpose has been conducted an extensive campaign of geognostic investigations, agreed with the customer.
Since it is known that the soil is highly compressible, the water table is found close to the level of the country floor and we are in an area with high seismicity, the investigations have provided mainly in situ tests (CPTu and DMT) as it is known that these investigations are those that best suit the land found and cause the least disturbance.
These investigations have also been accompanied by surveys that have the purpose, in addition to the collection of samples for laboratory tests, to be the site of geophysical investigation in down hole and environmental investigations (installation of piezometers).

1. List of investigations carried out

ON-SITE TESTS

• 10 static penetrometric tests with piezocone CPTu with lengths between 25.0 and 40.0 m from the ground level;
• 2 dilatometric tests with flat dilatometer Marchetti DMT having lengths of 30.0 m from the ground level;
• 3 continuous core drilling with lengths of 40.0 m from the ground level;
• Installation of 2 piezometers in borehole;
• Execution of a geophysical test in hole type Down-Hole DH for the measurement of the propagation speed of seismic waves of shear Vs;
• Execution of 3 single station measurements of microtremors with HVSR technique for the measurement of the propagation velocities of seismic shear waves Vs.

LABORATORY TESTS

• Sampling of 5 undisturbed soil samples from cohesive soil horizons;
• 6 tests for the determination of the physical parameters of the samples and for the measurement of the limits;
• Execution of 4 edometric compression tests to determine the parameters of deformability and consolidation;
• Execution of 1 direct shear test for the determination of shear strength parameters in drained conditions;
• 1 consolidated and drained triaxial test TX CD for the determination of the parameters of deformability and shear strength in drained conditions;
• 2 consolidated and undrained triaxial tests TX CIU for the determination of the parameters of deformability and shear strength in undrained conditions;
• 1 RC resonant column test for the measurement of the stiffness degradation and for the variation of the damping coefficient as a function of the magnitude of the tangential deformation.

We will propose, only for the main geotechnical parameters, comparisons between the interpretations of all 10 CPTu performed, so as to screen the uniformity of the geotechnical conditions measured and, subsequently, we will illustrate an interpretation of the DMT dilatometric test.

This will give a complete picture of the results of the tests conducted in situ, their spatial variability and the correlation obtained between the two different types of investigation, all demonstrating the robustness of the geotechnical modeling performed.

From a lithological point of view, after an initial altered surface layer, a sandy layer is encountered, formed by poorly thickened sands if not dissolved, in the water table, with low mechanical properties. This layer, of power about 9.0 m, from the analysis conducted shows a high susceptibility to liquefaction.
This aspect is to be seen as completely determinant both for the choice of the foundations to be used and for the characteristics of the foundation itself.
A next layer of about 17 m thickness, that is from -9.0 m to -26.0 m, is of clayey, or silt-clay nature. In this layer there are only local intercalations of an inconsistent nature which, however, according to the deduction of the geotechnical parameterization, do not change the general behavior of the layer.
This layer can in turn be separated into two, but only from the lithological point of view, having found in the lower half a higher sandy component. In any case, from the mechanical and deformation point of view, all the in situ analyses conducted converge in asserting that this layer behaves in a rather homogeneous way and can be well equated to a so-called “soft soil”, that is a layer of silt-clay nature with sandy intercalations of high compressibility and poor mechanical characteristics.
Therefore, barring purely lithological evaluations, this layer can be uniformly defined from a mechanical point of view.

All data have been elaborated by Teleios using the most recent theories on the subject, crossing more data and more variables, in order to reach an accurate series of geotechnical models suitable for all the different foundation hypothesis that can be adapted to the works and to the geotechnical characteristics in question.
The programs with which the parameters constituting the geotechnical models have been deduced have been directly elaborated by Teleios based on the most updated scientific bibliography produced at international level.
The models created range from those suitable for the calculation of piles and surface foundations, both in terms of strength and deformability, to hardening soil models to be used in finite element programs such as Plaxis, and hyperbolic models for a BEM calculation program, specific for the calculation of pile foundations, such as Repute (Geocentrix).
An example of a small HS geotechnical model that can be used in Plaxis is shown.