This study investigates the innovative reuse of sewage sludge with eco-friendly alkaline solutes to improve clayey soil without conventional cementitious binders.The unconfined compressive strength(UCS)was the main cr...This study investigates the innovative reuse of sewage sludge with eco-friendly alkaline solutes to improve clayey soil without conventional cementitious binders.The unconfined compressive strength(UCS)was the main criterion to assess the quality and effectiveness of the proposed solutions,as this test was performed to measure the strength of the stabilized clay by varying binders’dosages and curing times.Moreover,the direct shear test(DST)was used to investigate the Mohr-Coulomb parameters of the treated soil.Microstructure observations of the natural and treated soil were conducted using scanning electron microscope(SEM),energy-dispersive spectroscopy(EDS),and FTIR.Furthermore,toxicity characteristic leaching procedure(TCLP)tests were performed on the treated soil to investigate the leachability of metals.According to the results,using 2.5%of sewage sludge activated by NaOH and Na_(2)SiO_(3)increases the UCS values from 176 kPa to 1.46 MPa after 7 d and 56 d of curing,respectively.The results of the DST indicate that sewage sludge as a precursor increases cohesion and enhances frictional resistance,thereby improving the Mohr-Coulomb parameters of the stabilized soil.The SEM micrographs show that alkali-activated sewage sludge increases the integrity and reduces the cavity volumes in the stabilized soil.Moreover,TCLP tests revealed that the solubility of metals in the treated soil alkaliactivated by sewage sludge significantly decreased.This study suggests that using sewage sludge can replace cement and lime in ground improvement,improve the circular economy,and reduce the carbon footprint of construction projects.展开更多
Comfort is a major requirement in planning pedestrian facilities. Pedestrians walk where they feel comfortable and when they do not feel at ease, they walk elsewhere. A typical example is that filthy, distressed, or t...Comfort is a major requirement in planning pedestrian facilities. Pedestrians walk where they feel comfortable and when they do not feel at ease, they walk elsewhere. A typical example is that filthy, distressed, or too narrow sidewalks induce pedestrians to walk on carriageways. This behaviour jeopardizes road safety and highly dangerous to most users, leave them vulnerable. Unsuitable pavements can be the result of irregular maintenance operations to restore evenness after shock damage, weather phenomena, installation of equipment （e.g., posts, fences, urban furniture） with a reduction of walkable surface, or substandard repair work on pavements and patches due to emergency operations. These problems can be solved with an appropriate maintenance management system, which optimizes financial resources to make smart decisions about how to intervene with an adequate and lasting maintenance operation. This paper defines an evaluation index for sidewalk conditions as a part of an efficient set-up of a Sidewalk Management System, which is similar to the better known Road Management System. The study relies on sur- veys, as well as the classification and analysis of sidewalk distresses. The authors adapted an index already standardized by ASTM for roads and airports： the Pavement Condition Index （PCI）. PCI has been modified to consider the specific types on the sidewalks studied within this paper. To validate the method, a case study of a residential district in Rome, Italy, was carried out. The chosen area lacks regular maintenance and has therefore resulted in a network of unsafe sidewalks. Frequent detour routes were surveyed and related to the level of distresses within a general assessment of safety. This study con- centrates on sidewalks with flexible pavements because this type of pavement is the only one adopted in the survey areas and, in general, throughout Italy.展开更多
Although the construction of block pavements has grown fast in the last decades,there is still a need for simple tools that could be applied to design them.This paper analyzed and verified concrete block pavements for...Although the construction of block pavements has grown fast in the last decades,there is still a need for simple tools that could be applied to design them.This paper analyzed and verified concrete block pavements for urban and local roads composed of rectangular concrete pavers with plane side surfaces(no interlocking effect).The examined blocks were laid on a bedding sand layer,a cement treated base layer and a granular unbound foundation layer.The commercial finite element(FE)software ANSYS?was used to calculate the response of the pavement when subjected to different loading,construction configurations.Three wheel positions,five blocks patterns,three bedding sand thicknesses and joints gaps have been considered to evaluate stress-strain condition on pavement materials.Fatigue and rutting verification was performed respectively for bound and unbound pavement materials using analytical curves available in the literature.At the end of this study,a proposal for a catalogue is presented.It has nine pavement sets,because it takes into account three values of subgrade capacity(30,90,and 150 MPa of resilient modulus)and three levels of traffic(400,000,1,500,000,and 4,000,000 passages of commercial vehicles during the service life).The obtained results provide an inexpensive procedure for the preliminary design of concrete block pavements.展开更多
Home-to-school routes are very sensitive areas: they represent, for children, a learning tool for their everyday activities, but if poorly designed, maintained and equipped they can expose them to traffic risks. Sidew...Home-to-school routes are very sensitive areas: they represent, for children, a learning tool for their everyday activities, but if poorly designed, maintained and equipped they can expose them to traffic risks. Sidewalks' inappropriate level of service and poor maintenance, especially, are main factors contributing to walking unsuitability, thus to poor comfort and safety levels for young pedestrians, and more in general for all the vulnerable non-motorized road users. This paper deals with a methodology specifically developed to highlight the quality of the urban environment where the home-to-school routes are located, according to four main criteria: wellbeing, usage, appearance, and safety and security. Each criterion is associated with a checklist including the most relevant features to assess, with a focus on maintenance as a key parameter to create safe and comfortable routes to school. An application, a case study in Rome, where the lack of regular maintenance results into a network of unsafe sidewalks, is also presented, analyzing three different areas where a number of schools are located. Detours when approaching school premises were surveyed, due to the levels of distresses and linked to the poor comfort and safety levels. As the mutual influence of built environment over road safety and maintenance requirements for home-to-school paths is not largely investigated thus far, the paper's goal is to provide advanced knowledge for studies and applications further afield.展开更多
The attention to road safety-related issues has grown fast in recent decades. The experi- ence gained with these themes reveals the importance of considering these aspects in the resource allocation process for roadsi...The attention to road safety-related issues has grown fast in recent decades. The experi- ence gained with these themes reveals the importance of considering these aspects in the resource allocation process for roadside and guardrail improvement, which is a complex process often involves conflicting objectives. This work consists on defining an innovative methodology, with the objective of calculating and analysing a numerical risk factor of a road. The method considers geometry, accident rate, traffic of the examined road and four categories of elements/defects where the resources can be allocated to improve the road safety （safety barriers, discrete obstacles, continuous obstacles, and water drainage）. The analysis allows the assessment of the hazard index, which could be used in decision- making processes. A case study is presented to analyse roadsides of a 995 km long road network, using the cost-benefit analysis, and to prioritize possible rehabilitation work. The results highlighted that it is suitable to intervene on roads belonging to higher classes of risk, where it is possible to maximize the benefit in terms of safety as consequence of rehabilitation works （i.e., new barrier installation, removal and new barrier installation, and new terminal installation）. The proposed method is quantitative; therefore, it avoids providing weak and far from reliable results; moreover, it guarantees a broad vision for the problem, giving a useful tool for road management body.展开更多
文摘This study investigates the innovative reuse of sewage sludge with eco-friendly alkaline solutes to improve clayey soil without conventional cementitious binders.The unconfined compressive strength(UCS)was the main criterion to assess the quality and effectiveness of the proposed solutions,as this test was performed to measure the strength of the stabilized clay by varying binders’dosages and curing times.Moreover,the direct shear test(DST)was used to investigate the Mohr-Coulomb parameters of the treated soil.Microstructure observations of the natural and treated soil were conducted using scanning electron microscope(SEM),energy-dispersive spectroscopy(EDS),and FTIR.Furthermore,toxicity characteristic leaching procedure(TCLP)tests were performed on the treated soil to investigate the leachability of metals.According to the results,using 2.5%of sewage sludge activated by NaOH and Na_(2)SiO_(3)increases the UCS values from 176 kPa to 1.46 MPa after 7 d and 56 d of curing,respectively.The results of the DST indicate that sewage sludge as a precursor increases cohesion and enhances frictional resistance,thereby improving the Mohr-Coulomb parameters of the stabilized soil.The SEM micrographs show that alkali-activated sewage sludge increases the integrity and reduces the cavity volumes in the stabilized soil.Moreover,TCLP tests revealed that the solubility of metals in the treated soil alkaliactivated by sewage sludge significantly decreased.This study suggests that using sewage sludge can replace cement and lime in ground improvement,improve the circular economy,and reduce the carbon footprint of construction projects.
文摘Comfort is a major requirement in planning pedestrian facilities. Pedestrians walk where they feel comfortable and when they do not feel at ease, they walk elsewhere. A typical example is that filthy, distressed, or too narrow sidewalks induce pedestrians to walk on carriageways. This behaviour jeopardizes road safety and highly dangerous to most users, leave them vulnerable. Unsuitable pavements can be the result of irregular maintenance operations to restore evenness after shock damage, weather phenomena, installation of equipment （e.g., posts, fences, urban furniture） with a reduction of walkable surface, or substandard repair work on pavements and patches due to emergency operations. These problems can be solved with an appropriate maintenance management system, which optimizes financial resources to make smart decisions about how to intervene with an adequate and lasting maintenance operation. This paper defines an evaluation index for sidewalk conditions as a part of an efficient set-up of a Sidewalk Management System, which is similar to the better known Road Management System. The study relies on sur- veys, as well as the classification and analysis of sidewalk distresses. The authors adapted an index already standardized by ASTM for roads and airports： the Pavement Condition Index （PCI）. PCI has been modified to consider the specific types on the sidewalks studied within this paper. To validate the method, a case study of a residential district in Rome, Italy, was carried out. The chosen area lacks regular maintenance and has therefore resulted in a network of unsafe sidewalks. Frequent detour routes were surveyed and related to the level of distresses within a general assessment of safety. This study con- centrates on sidewalks with flexible pavements because this type of pavement is the only one adopted in the survey areas and, in general, throughout Italy.
文摘Although the construction of block pavements has grown fast in the last decades,there is still a need for simple tools that could be applied to design them.This paper analyzed and verified concrete block pavements for urban and local roads composed of rectangular concrete pavers with plane side surfaces(no interlocking effect).The examined blocks were laid on a bedding sand layer,a cement treated base layer and a granular unbound foundation layer.The commercial finite element(FE)software ANSYS?was used to calculate the response of the pavement when subjected to different loading,construction configurations.Three wheel positions,five blocks patterns,three bedding sand thicknesses and joints gaps have been considered to evaluate stress-strain condition on pavement materials.Fatigue and rutting verification was performed respectively for bound and unbound pavement materials using analytical curves available in the literature.At the end of this study,a proposal for a catalogue is presented.It has nine pavement sets,because it takes into account three values of subgrade capacity(30,90,and 150 MPa of resilient modulus)and three levels of traffic(400,000,1,500,000,and 4,000,000 passages of commercial vehicles during the service life).The obtained results provide an inexpensive procedure for the preliminary design of concrete block pavements.
文摘Home-to-school routes are very sensitive areas: they represent, for children, a learning tool for their everyday activities, but if poorly designed, maintained and equipped they can expose them to traffic risks. Sidewalks' inappropriate level of service and poor maintenance, especially, are main factors contributing to walking unsuitability, thus to poor comfort and safety levels for young pedestrians, and more in general for all the vulnerable non-motorized road users. This paper deals with a methodology specifically developed to highlight the quality of the urban environment where the home-to-school routes are located, according to four main criteria: wellbeing, usage, appearance, and safety and security. Each criterion is associated with a checklist including the most relevant features to assess, with a focus on maintenance as a key parameter to create safe and comfortable routes to school. An application, a case study in Rome, where the lack of regular maintenance results into a network of unsafe sidewalks, is also presented, analyzing three different areas where a number of schools are located. Detours when approaching school premises were surveyed, due to the levels of distresses and linked to the poor comfort and safety levels. As the mutual influence of built environment over road safety and maintenance requirements for home-to-school paths is not largely investigated thus far, the paper's goal is to provide advanced knowledge for studies and applications further afield.
文摘The attention to road safety-related issues has grown fast in recent decades. The experi- ence gained with these themes reveals the importance of considering these aspects in the resource allocation process for roadside and guardrail improvement, which is a complex process often involves conflicting objectives. This work consists on defining an innovative methodology, with the objective of calculating and analysing a numerical risk factor of a road. The method considers geometry, accident rate, traffic of the examined road and four categories of elements/defects where the resources can be allocated to improve the road safety （safety barriers, discrete obstacles, continuous obstacles, and water drainage）. The analysis allows the assessment of the hazard index, which could be used in decision- making processes. A case study is presented to analyse roadsides of a 995 km long road network, using the cost-benefit analysis, and to prioritize possible rehabilitation work. The results highlighted that it is suitable to intervene on roads belonging to higher classes of risk, where it is possible to maximize the benefit in terms of safety as consequence of rehabilitation works （i.e., new barrier installation, removal and new barrier installation, and new terminal installation）. The proposed method is quantitative; therefore, it avoids providing weak and far from reliable results; moreover, it guarantees a broad vision for the problem, giving a useful tool for road management body.
