EQUIVALENT SIMPLIFIED SOIL PROFILES FOR LIQUEFACTION ASSESSMENT

The study of the phenomenon of liquefaction has always been a subject of great importance since it can occur without any warning and can cause very dangerous damage to structures with subsequent consequences for human lives. For these reasons, there is an increasing desire in the engineering world to anticipate the effects and find solutions that can prevent catastrophes. In virtue of what has been said before, an European project called LIQUEFACT has been carried out with the intention of studying in depth the problems related to the problem of the initiation of liquefaction and the interaction between soil and structure. This project is divided into different Work Projects and one of them, in particular WP3, is sponsored by the University of Porto and the team of which I was a member. This thesis work has participated in the cause of WP3 in the realization of a new and innovative expedient that is that of the modelling of the soil through the Equivalent Soil Profiles. In particular, the first part of the thesis work was to understand and study in depth the phenomenon of liquefaction of soils through a method, considered innovative, precise and modern, which is that of Boulanger and Idriss 2014. This method has been applied to two series of CPTu tests carried out on soils that have been liquefied in the past; these CPTu tests come from Christchurch (New Zealand) and Lisbon (Portugal). Moreover, from several recent studies, it has been decided to adopt the value of LSN as the main qualitative index of a single soil. Through it the soil can be classified as particularly subject or not to the phenomenon of liquefaction. The second part was about the calibration of the software in use (Python), in accordance with analyses conducted by a free software such as CLiq 2.0. This was followed by the outline of the guidelines for modelling the Equivalent Soil Profiles. First, it was inspired by what the team of Prof. Emeritus Cubrinovski (2017) has already achieved. The practice of Equivalent Soil Profiles essentially serves to model the real soil profiles obtained from a CPTu test, which is composed of multiple natural layers of soil, three simple layers. These three layers are superimposed on each other and have different characteristics, in fact the first and the third are non-liquefiable, while the second is. This particular conformation allows to concentrate all the liquefaction phenomenon only in one layer, where, in reality, it is spread in the different natural layers. This example allows to treat a natural soil profile in a simple and quick way. The LSN index has been used to achieve conformity between the actual profile and the equivalent one. This was followed by the implementation of different methods based on different parameters in order to obtain Equivalent Soil Profiles. The third part was simply to classify the Equivalent Soil Profiles in different classes based on crust thickness, liquefiable layer and CRR7.5 value of the latter. The last part, equally interesting, was that of an application of this method, in order to study the soil-structure interaction. The application was related to the bearing capacity of equivalent soil profiles, verifying the relationships between the answers of the latter considering the post and pre-liquefaction conditions. The key to reading this last part can be appreciated in the future as a study of prevention of soil-structure interaction.