102,708 research outputs found
Hydrological behaviour of rain gardens and plant suitability: A study in the Veneto plain (north-eastern Italy) conditions
No full textSince spring 2011 the roof of a building on the Agripolis Campus of the University of Padova (Italy) has been used as a drainage area for two rain gardens with a circular area of about 10% and 20% of the drainage area respectively. To improve soil infiltration, the topsoil was removed up to the depth of 1 m and filled with a mix of 50% sand, 25% compost and 25% of the existing topsoil. Herbaceous perennials were selected and planted to test their adaptability to different soil water conditions in the rain garden. To evaluate the capacity of each rain garden to manage stormwater runoff a simplified water balance was done, estimating actual evapotranspiration using the WUCOLS method. From autumn 2012 runoff volumes were collected just from one pitch of the roof, and directed only into the smaller rain garden that became equal to 15% of the new roof drainage area. We thus had the possibility to test the functionality of rain gardens with three different percentages of roof drainage area: 10, 15 and 20%, even if in different periods. Results are presented relating to a four-year experimental period. Regarding hydrological behaviour, the input water volumes caused a slight overflow only during a few rainfall events. Consequently, the results showed a high capacity to manage stormwater runoff and also in the smaller rain garden almost the total roof runoff volumes infiltrated into the soil. As regards plants, the results indicated that the growth is affected by their position in the rain garden, from the wettest condition in the centre to the driest at the perimeter, except for Hemerocallis hybrida that showed great adaptability in all positions. Aster novi-belgii, Echinacea purpurea, Iris pseudacorus, Molinia caerulea and Rudbeckia fulgida also showed good adaptation, even if not in all rain garden zones, with highly aesthetic results. Lythrum salicaria and Saponaria officinalis plants appeared to be unsuitable for rain gardens. The results of the experiment have shown that, in the Veneto plain environment, rain gardens with a size of 10–15% of the roof drainage area can ensure both the sustainable management of stormwater runoff and a high aesthetic functionality
Influence of lighting on road safety on motorways
No full textContributing towards safety is a primary objective of modern and efficient planning, in accordance with the Directives from the European Union and national legislation. Nowadays, guaranteeing a suitable safety level is the main aim to be pursued by the road engineer and manager of the road infrastructure.
The research verifies the impact of lighting on road safety and its effectiveness in reducing the number and gravity of accidents: in particular, attention is focused on the lighting of the principal Italian motorways.
A descriptive comparison has been done between the macroscopic variables observed in the presence or absence of artificial lighting. A qualitative estimate has been made of how much the lighting contributes towards traffic safety on motorways. It has been verified that artificial lighting makes a decisive contribution, reducing the number and seriousness of night-time accidents by around 30
The accident rate in urban area intersections: the use of neural artificial net to improve the road safety
No full textThe paper presents a research which tackles two issues. The first involves the study of different types of survey reports with reference to road accidents in urban areas: the aim is the identification of characteristics to make the survey reports more functional.
The second one consists of defining the functional relationship between some variables which the hazard level of an intersection depends upon. Particularly, accident data are used to check, with a neural artificial net model, what type of dependence links the accident rate in urban areas to the traffic flows, the geometric features of the intersection and the environmental characteristics (road paving, weather conditions...).
The pursued objectives contemplate a safety increase in the flow of traffic at urban intersections. An improved survey report layout implies a higher level of reliability of the data processing, and the use of neural nets allows a fast identification of the most suitable technical solutions to improve the safety of the intersections
Cold-mix asphalt for road foundations: use of cement and foamed bitumen in "high performance" pavements
No full textThe reduced availability of traditional aggregate, increasing environmental sensitivity and the high intrinsic value of marginal materials from the milling of the old damaged road pavements, have in recent years justified growing interest in “cold recycling” as a technique which can be used in the construction or rehabilitation of pavements, in spite of the use of “poor” materials. Cold recycling can be developed by means of cement and foamed bitumen. The technique gathers the benefits of the cold in situ recycling and those related to the use of the foamed bitumen. Despite its undisputed advantages, the above-mentioned technique has not yet been supported by a consolidated experimentation in Italy that attests to which factors could mainly affect the performances of the foamed mixture.
The paper describes an investigation aimed at testing foamed mixtures to be used in major roads. In particular, the influence of moisture, temperature and fine content on the mechanical performances of the material have been checked. The results demonstrate that pavements with cement and foamed bitumen foundations can be compared – in terms of bearing capacity and durability – with flexible pavements, on the basis of the Italian Design Pavement Catalogue
The experimental and educational rain gardens of the Agripolis Campus (north-east Italy): Preliminary results on hydrological and plant behavior
No full textIn most urbanized areas stormwater runoff, flowing on impervious surfaces, can increase the risk of floods and overload of drainage systems. Landscape designers may contribute to the mitigation of the problem by incorporating appropriate solutions in the design of green spaces. Rain gardens are green infrastructures that can contribute to more sustainable urban development. Since 2011, an experiment has been carried out at the University of Padova with the aim to assess the use of rain gardens for a sustainable management of the stormwater runoff. Two circular rain gardens with herbaceous perennials, differently sized and equipped with TDR soil moisture sensors, were designed and built to intercept equal amounts of runoff draining from a building roof with an area of 215 m2. The experiment consisted of testing the capacity of intercepting runoff caused by storm of different magnitude, in measuring the dynamics of water in the topsoil after the rainfall events and in evaluating the growth and aesthetic quality of the different plant species used. Input and output water volumes were measured and actual ET was estimated using WUCOLS Landscape Coefficient Methods. Results of the preliminary phase showed that both the rain gardens were able to satisfactorily manage the roof runoff, which was taken off the urban drainage system, with a good aesthetic result
Mechanical characterisation of hydraulically bound mixtures for road foundations made with waste foundry sand and C&D aggregate
No full textThe paper describes a study of hydraulically bound mixtures, composed of foundry sands and C&D aggregate, produced for use in the foundation of road pavements. The investigations involved a physical and mechanical characterisation of the individual components, followed by that of the mixtures (by means of tensile strength, compressive strength, elastic modulus etc.). The results of the tests have been compared with the requisites for acceptance of traditional hydraulic mixtures in the main italian Contract Specifications, which has demonstrated that the analysed material is suitable for use
Acquisizione, elaborazione ed analisi spaziale di immagini per la gestione del degrado delle pavimentazioni stradalI
No full textRoad maintenance is till today, in many cases, left to improvisation. It is often performed when the pavement has been damaged, through interventions and repairing times based upon previous experience or consolidated practice. The continuous increase in road traffic and stresses on the pavements, the necessity to ensure high safety levels and, moreover, the reduction of the available funds for the Public Administrations impose different and innovative managerial choices. Therefore, repair works need to be planned and executed with the best quality-cost rate, in the shortest time possible and with the smallest discomfort to road users.
The automatic survey technique represents the only possible solution to carry out a modern and efficient Pavement Management System (PMS).
The paper describes a research which defines a systematic method for the analysis and the study of the image acquisition and processing techniques useful to develop a non-destructive automatic system for the maintenance state survey of the pavement and for the management of the optimum interventions in a GIS.
Once defined the procedure to use for image acquisition, the processing was made through operations of segmentation, extraction and classification. After reclassifying the image and vectorializing the cracks, was estimated the entity of the damage.
Furthermore, it was verified how spatial resolution and brightness are fundamental factors for a correct implementation of the entire system.
The ArcGIS proves to be the most suitable support to integrate all the procedures used for imaging elaboration and spatial analysis. This software presents user-friendly interfaces and provides efficient visualizations of surveyed results, not only for the use of transportation engineers (engaged in maintenance management), but also for Road Administrators
- …
