Contatti intergranulari e resistenza a taglio di una sabbia "serrata"

A Landslide in Overconsolidated Clays that Has Involved an Important Road of Access to an Internal Mountain Town

The paper presents a case study on the interference of a landslide in overcosolidated clays, triggered in autumn 2004 - winter 2005 by high pore water pressures, on the usability of an important provincial road of an internal town. In the period of 2004–2019 the landslide suffered several mobilisations that led to temporary closures of the road and continuous interventions on the roadway for its use, that caused significant inconvenience for the population and damage to the commercial, sanitary, touristic, agricultural and other activities. In 2018 a study has allowed to identify the kinematic characters of the landslide and the depth of the sliding surface. The study has confirmed that the…

Quantum chemical models of acidic sites in H-ZSM-5 zeolites

La microstruttura di una "locked sand"

Nella nota si riportano alcuni risultati sperimentali sul comportamento meccanico di una locked sand. Si descrive la microstruttura della sabbia sulla base di osservazioni al microscopio ottico e al SEM. Si descrivono in particolare i tipi di contatti intergranulari, che sono prevalentemente interpenetranti (concavo-convessi e suturati), gli indici grain contact e packing density caratterizzanti la struttura del materiale, e la loro influenza sul comportamento meccanico della sabbia. I risultati ottenuti sono confrontati con quelli di altre locked sands.

H−ZSM-5 Modified Zeolite:  Quantum Chemical Models of Acidic Sites

A ZSM-5 fragment, containing 52 tetrahedral moieties, each of them formed by one silicon or one aluminum atom surrounded by four oxygen atoms, was employed to model (52T systems) by quantum chemical calculations (i) the influence of the positions of the acidic sites on the energetics of 22 aluminum monosubstituted and bisubstituted 52T acidic zeolite (H-ZSM-5) systems and (ii) the local adsorption properties and acidic strength of the corresponding -OH sites. The energetics and the structural properties of simpler acid H-ZSM-5 systems containing only five Tetrahedral moieties (5T systems) were also modeled for comparison. B3LYP/6-31G(d,p) partial geometry optimization routines were performe…