Today climate change represents one of the most important topic that has raised a great mediatic impact. This is due to the negative effects that hit our planet in several fields but, in most cases, its consequences deal with the civil and environmental preservation. Indeed, in this context, in the regions that have high-latitude, the increase of the temperature involves a degradation of the permafrost that produces the famous phenomenon known as frost heave. This phenomenon consists in an upward swelling of the soil that damage several structures such as roads, oil pipelines or railways; this is the reason why the scientific community strives to find a way to measure it. These studies began in the ’70 with few analytical models but, if the hydrology part is clearly transcribed, it wasn’t the same for the mechanical deformation which cause the motion of the soil. This thesis has the purpose to quantify numerically the radial pressure that have been caused by the frost heave. The purpose is to define a test setup starting with creating a load cell which contains the soil that will be deformed. During the experiment, this cell is put into a fridge at the temperature of -40°C while an extensimeter measures the radial strain generated on the upper and lower part of the load cell. The structure of the thesis follow this phases. First of all there is a short introduction on the phenomenon that is helpful to understand the elements which are part of the theoretical problem. In the second part there is a comparative analysis of the state of art in order to investigate the advantages and the issues of the analytic description of the phenomenon. Finally, the last section deals with an innovative setup contribution which begins from a Finite Element Method (FEM) with the software Comsol Multiphysics with the aim to develop the shape, the thickness and the material of the load cell with awareness. After this step, the outputs of the software are compared with the same stress strain obtained from the load cell in the experimental laboratory tests.
Ad oggi, il climate change, rappresenta una delle tematiche che ha suscitato il maggiore impatto mediatico; questo perché gli effetti negativi che si riscontrano sul nostro pianeta sono svariati e disastrosi, sicuramente in larga scala, colpiscono il comparto civile e ambientale. É Proprio in questi settori che si cela una tra le conseguenze più particolari, difatti, l'aumento termico in territori situati ad alta latitudine, ove in genere si registrano temperature rigide, provoca una degradazione del permafrost dando vita al famoso fenomeno del frost heave. Quest'ultimo si concretizza in un sollevamento differenziale del piano campagna comportando notevoli danni infrastrutturali; motivo per il quale la comunità scientifica ha cercato di tradurne il suddetto comportamento in termini numerici. Questi studi hanno origine a partire dagli anni ’70 tuttavia, se lo stato dell’arte ha portato alla luce delle brillanti risoluzioni dal punto di vista idraulico, così non si può dire per quanto riguarda il comparto meccanica soprattutto in termini quantitativi resta tutt'oggi poco chiaro. La seguente tesi ha quindi lo scopo di produrre un set-up sperimentale che sia in grado di decifrare e quantificare gli aspetti tenso-deformativo, concretizzando quanto dichiarato dalla controparte analitica. La struttura generale dell’elaborato seguirà questa traccia: inizialmente viene proposta una breve introduzione caratterizzante il fenomeno, questo è utile per richiamare alcuni elementi teorici necessari alla completa comprensione del problema. Successivamente verrà presentato lo stato dell’arte dove saranno analizzati, in ordine cronologico, i modelli sviluppati allo scopo di marcare quelli che sono i punti di forza ma anche le problematiche riscontrate nella traduzione del fenomeno. Nella terza ed ultima parte verrà proposta un’analisi ad elementi finiti (FEM) su Comsol Multiphysics, utile al fine di scegliere con grande consapevolezza la forma e il materiale di quello che sarà il contenitore del terreno. Con questo strumento sarà possibile, tramite dei sensori, leggere le deformazioni radiali indotte dal fenomeno del congelamento. A seguire, con quanto creato, saranno effettuati dei test in laboratorio allo scopo di confrontare i risultati sperimentali con l'output di Comsol Multiphysics.
Analisi del suolo in condizioni non isoterme : stato dell'arte e indagine sperimentale tramite dispositivo R.D.P
Somaschini, Alberto
2020/2021
Abstract
Today climate change represents one of the most important topic that has raised a great mediatic impact. This is due to the negative effects that hit our planet in several fields but, in most cases, its consequences deal with the civil and environmental preservation. Indeed, in this context, in the regions that have high-latitude, the increase of the temperature involves a degradation of the permafrost that produces the famous phenomenon known as frost heave. This phenomenon consists in an upward swelling of the soil that damage several structures such as roads, oil pipelines or railways; this is the reason why the scientific community strives to find a way to measure it. These studies began in the ’70 with few analytical models but, if the hydrology part is clearly transcribed, it wasn’t the same for the mechanical deformation which cause the motion of the soil. This thesis has the purpose to quantify numerically the radial pressure that have been caused by the frost heave. The purpose is to define a test setup starting with creating a load cell which contains the soil that will be deformed. During the experiment, this cell is put into a fridge at the temperature of -40°C while an extensimeter measures the radial strain generated on the upper and lower part of the load cell. The structure of the thesis follow this phases. First of all there is a short introduction on the phenomenon that is helpful to understand the elements which are part of the theoretical problem. In the second part there is a comparative analysis of the state of art in order to investigate the advantages and the issues of the analytic description of the phenomenon. Finally, the last section deals with an innovative setup contribution which begins from a Finite Element Method (FEM) with the software Comsol Multiphysics with the aim to develop the shape, the thickness and the material of the load cell with awareness. After this step, the outputs of the software are compared with the same stress strain obtained from the load cell in the experimental laboratory tests.File | Dimensione | Formato | |
---|---|---|---|
Alberto_Somaschini_Tesi.pdf
solo utenti autorizzati dal 15/05/2022
Descrizione: Analisi del suolo in condizioni non isoterme: stato dell'arte e indagine sperimentale tramite dispositivo R.D.P
Dimensione
14.07 MB
Formato
Adobe PDF
|
14.07 MB | Adobe PDF | Visualizza/Apri |
I documenti in POLITesi sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
https://hdl.handle.net/10589/174902