The sizing of any geotechnical engineering industry and technology requires, first of all, a good knowledge of the foundation soil. Thus, the first stage of the project is a geotechnical exploration satellite; it allows the engineer to select representative values of the soil characteristics necessary for the calculations. However, choosing these values is a difficult task that requires a lot of experience and know-how from a practicing engineer.
Indeed, it is obvious that it is impossible to determine soil properties at any point in the plot; therefore, representative parameter values are usually determined on the basis of some results of testing samples taken almost randomly and field tests carried out in a more or less wide grid. Classical soil mechanics is based on simplifying assumptions that ignore soil characteristics; Soil, as a rule, is determined by heterogeneity, diversity, variability in space and uncertainty.
The information extracted from physical properties mechanically determines representative values of the calculation parameters, these values are globally uncertain, which translates due to uncertainties into predicting the behavior of work in the future. In addition, it is generally accepted that the models that we use to calculate the behavior of base soils are not very satisfactory. Many of them seem irrelevant as soon as they are applied to real-sized soil massifs and their forecasts in comparison with the results of measurements performed on a real site.
From the classical “deterministic” point of view, this unfavorable comparison should lead to the rejection of the rheological model or to the search for better values of the parameters. Therefore, a new approach to soil mechanics is needed in order to try to solve these problems of soil heterogeneity and model their behavior, or at least to better understand them. Thus, statistical and probabilistic methods complement the classical deterministic methods. That is why, over the course of forty years, a statistical and probabilistic approach to soil mechanics has developed and gained certain significance in many branches of geotechnics. The purpose of applying the methods of statistical and probabilistic analysis is to quantify the effect of natural soil variability on the behavior of structures and eliminate subjectivity in the choice of an engineer. As far as we know, very few studies on factor analysis of data have been carried out in the field of geotechnics: one rarely sees, for example, the development of studies on the main components or factor analysis of correspondence in geotechnics.
Civil engineering methods have benefited from a wide range of innovations in the recent past. This process continues with innovative time constants in the heavy equipment and engineering software sectors. These modifications are very diverse; they relate to almost all aspects of civil engineering. The following few examples illustrate the most characteristic aspects of the evolution of the methods used in civil engineering. Two of these examples relate to materials whose use is currently undergoing rapid development. On the one hand, it is geotextile placed in the soil, and on the other hand, it is a mixture of bitumen and polymers used in road constructions. Two other examples relate to methods recently developed or under development. The selected cases are, firstly, the transfer of methods from geophysics to civil engineering and, secondly, the first use of optical fibers for measurements on bridges and roads.
Naturally, the machines that allow it to be produced are new, their creation required ingenuity and long development. The same applies to sizing and control methods. The relevance of the use of geotextiles in civil engineering is currently recognized by other industrialized countries: 50% of geotextiles used in this area in 1988 were in America. Naturally, manufacturing companies (more than a hundred) and users offer many processes that would be too long to list easily, and which differ from each other in the nature of the basic materials, their assembly methods and their implementation. The main raw materials are synthetic polymers, which are much less biodegradable than natural polymers: polyesters, polyamides, polypropylenes, polyethylene, polyvinyl chloride.