Preliminary investigation on the water retention behaviour of cement bentonite mixtures

Cement bentonite mixtures are often used to build slurry walls for the containment of both aqueous and non aqueous pollutants, due to their quite low hydraulic conductivity and relatively high ductility and strength. Although their hydro-mechanical behaviour in saturated conditions has been studied in the past, a part of the slurry wall is expected to rest above the groundwater level. The hydraulic characterization in unsaturated conditions is then particularly relevant to evaluate the performance of the barrier, especially when it is aimed at containing non aqueous pollutant liquids which are lighter than water (LNAPL). These non wetting fluids rest above the water table and their penetration is possible just if the barrier is unsaturated. This paper presents some preliminary results of a laboratory characterization of the water retention behaviour of three different cement bentonite mixtures. The mixtures, prepared at cement - bentonite mass ratios ranging from 4:1 to 6:1, were immersed in water and cured for 28 days. Their water retention behaviour was then determined along drying and wetting paths through different techniques, namely axis translation, filter paper and vapour equilibrium. In the high suction range, the water content - suction relationship was found to be independent of cement-bentonite ratio. In the low suction range, the water content at a given suction was found to decrease for increasing cement bentonite ratios

Analisi numerica di diaframmi plastici dotati di dispositivi per il monitoraggio e la prevenzione dell'inquinamento ambientale

I diaframmi plastici costituiti da miscele di cemento e bentonite rappresentano una soluzione interessante e vantaggiosa in interventi di tutela e salvaguardia ambientale. Scopo dei diaframmi plastici in tale ambito è isolare e ridurre il più possibile la dispersione nell’ambiente di fluidi contaminanti; pertanto i loro requisiti principali sono una conducibilità idraulica molto bassa e una elevata durabilità. Questo implica la necessità di una valutazione sempre più accurata dell’efficienza dell’opera. A questo scopo, l’uso di specifici ed innovativi dispositivi inseriti durante la realizzazione stessa del diaframma evoluto si è dimostrato particolarmente adatto ad intercettare i fluidi potenzialmente contaminanti prima che fuoriescano dalla barriera e contaminino l’ambiente. In questa nota si presentano i risultati preliminari di uno studio numerico svolto con l’obiettivo di suggerire criteri di installazione di questi dispostivi, frutto di un accordo di collaborazione promosso dalla Direzione Generale per la Sicurezza anche Ambientale delle Attività Minerarie ed Energetiche del Ministero dello Sviluppo Economico con il Politecnico di Milano

Measurement of Lifetime and Decay-Width Difference in B0s -> J/psi phi Decays

We measure the mean lifetime, tau=2/(Gamma_L+Gamma_H), and the width difference, DeltaGamma=Gamma_L-Gamma_H, of the light and heavy mass eigenstates of the B0s meson, B0sL and B0sH, in B0s -> J/psi phi decays using 1.7 fb^-1 of data collected with the CDF II detector at the Fermilab Tevatron ppbar collider. Assuming CP conservation, a good approximation for the B0s system in the Standard Model, we obtain DeltaGamma = 0.076^+0.059_-0.063 (stat.) +- 0.006 (syst.) ps^-1 and tau = 1.52 +- 0.04 (stat.) +- 0.02 (syst.) ps, the most precise measurements to date. Our constraints on the weak phase and DeltaGamma are consistent with CP conservation. Dedicated to the memory of our dear friend and colleague, Michael P. Schmid

Dispositivi per il monitoraggio delle proprietà chemo-idrauliche dei diaframmi plastici

I diaframmi plastici costituiscono una delle soluzioni più comuni per la cinturazione di zone contaminate e il contenimento del trasporto degli inquinanti nel sottosuolo. Queste barriere sono generalmente costituite da miscele di sabbia-bentonite o di cemento-bentonite, che garantiscono un basso valore di condu-cibilità idraulica, un basso valore del coefficiente di diffusione e una durabilità dell'opera anche a lungo ter-mine. Tuttavia, l’ambiente chimicamente aggressivo al quale i diaframmi devono fare fronte e le incertezze legate ai processi costruttivi potrebbero causare un degrado delle proprietà di trasporto della miscela, renden-do fondamentale il monitoraggio dell’efficienza dell’opera. In questa nota si valutano quantitativamente le po-tenzialità di diaframmi plastici tecnologicamente avanzati, ovvero forniti di particolari dispositivi di monito-raggio al loro interno. I dispositivi, oltre a poter ridurre il flusso di contaminante in uscita, consentono di monitorare e stimare le proprietà chemo-idrauliche del diaframma alla scala del sito

Voluntary Intake of Alcohol is Attenuated by Ipspirone in Mice and Role of 5-HT1A Receptor

Cutoff walls represent an interesting solution for the containment of the pollution of superficial groundwater. For polluted sites, the purpose of a cement-bentonite cutoff wall is to minimize contaminant transport and the primary design requirement for such materials is the low hydraulic conductivity. Despite these barriers are often cast in place as provisional tools, recently their wide use imparted the need for a better understanding of cement-bentonite walls also in the long-term. This certainly implies not only the need to study the time evolution of the cement-bentonite hydro-mechanical properties in a contaminated environment, but also the necessity of a continuous monitoring of the efficiency of the system. To this aim, the use of dedicated devices cast in place inside the wall when the mixture is still fluid proved to be particularly suitable to intercept and analyse the fluids flowing through the barrier. In this paper, the results of a numerical study are presented, with the goal of suggesting criteria about the optimum spacing and geometry of these device

A procedure to estimate cutoff wall transport properties from monitoring wells

Owing to their capability in limiting the transport of pollutants in the subsoil, cutoff walls are popular solutions for the confinement of contaminants. These barriers are often made of soil-bentonite or cement-bentonite mixtures, which are characterized by low hydraulic conductivity, low hydrodynamic dispersion, and long-term durability. However, the aggressive chemical environment to which these walls are subjected might negatively impact on their performance. Assessment of their performance with time is thus a crucial issue in wall design. The use of dedicated monitoring wells, cast in place inside the wall during construction when the bentonitic mixture is still fluid, can be particularly suitable for both intercepting and detecting the fluids flowing through the barrier. In this research, the results of a numerical study aimed at providing a methodology to estimate the transport properties of the backfill material at the site scale are presented. The methodology relies on abaci and only requires (i) flow and concentration of contaminant data within a monitoring well inside the barrier and (ii) hydraulic head at inlet and outlet of the barrier to be known

ECO-TOUR: TURISMO ED AREE PROTETTE, UNA QUESTIONE DI SOSTENIBILITA'

Il connubio tra turismo ed aree protette presenta una serie di potenzialit\ue0 e successi, ma comporta anche potenziali rischi e problemi dovuti a conflitti tra usi economici e obiettivi di tutela. Il tema \ue8 stato affrontato attraverso indagini a livello locale su complessi formati dal Parco, comunit\ue0 locale e attivit\ue0 economiche, il cui sviluppo dovrebbe seguire criteri di sostenibilit\ue0 Sono stati utilizzati tre casi studio situati in tre parchi italiani: Alpi marittime, Stelvio (sezione Lombarda), e Laguna di Venezia, per indagare sui aspetti sociali, economici ed ecologici della sostenibilit\ue0 di usi turistici nei parchi. SUMMARY The alliance between tourism and protected areas presents some potential synergies and success stories, but it also brings some risks and eventual problems due to conicts between economic uses and protection aims. In three case studies, enquiries on the local contexts of economic uses, protection aims and local comunities have been made, using the experiences of Italian Parks (the Alpi Marittime Park, the Lombardia section of the Stelvio Park and the Venetian Lagoon), in order to investigate on social, economic and ecologic aspects of sustainability of tourist uses in parks