Sustainable Urban Street Comprising Permeable Pavement and Bioretention Facilities: A Practice

Optimizing parameters for the preparation of low viscosity rubber asphalt incorporating waste engine oil using response surface methodology

Due to the high viscosity, rubber asphalt displays poor construction workability, which ultimately compromises the comfort and safety of pavement. In this study, specified control variates were used to study the effect of the waste engine oil (WEO) addition sequence on the properties of rubber asphalt while ensuring the consistency of other preparation parameters. Initially, in order to evaluate their compatibility, the storage stability and aging properties of the three groups of samples were determined. The variation of asphalt viscosity was then analyzed using a low-field nuclear magnetic resonance (LF-NMR) test, by predicting the fluidity of each sample. Subsequently, the results showed that the rubber asphalt prepared by premixing WEO and crumb rubber (CR) had the best properties of low temperature, compatibility, and fluidity. On this basis, the effects of WEO content, shear rate, shear temperature, and shear time on the properties of low viscosity rubber asphalt were investigated separately through response surface methodology (RSM). Quantitative data from the basic performance experiment were used to fit the high precision regression equation, thereby correlating a more precise level of factors with experimental results. The response surface model prediction analysis showed that the optimal preparation parameters of the low viscosity rubber asphalt were 60 min shear time, 180 °C shear temperature, and 5000 r/min shear rate. Simultaneously, the addition of 3.5% of WEO showed great potential as an asphalt viscosity reducer. Ultimately, this study provides an accurate method for determining the optimum preparation parameters of asphalt.

Experimental and numerical research on the hydrological characteristics of sunken green space with a new type of composite structure

Based on the characteristics of concentrated rainwater runoff in the mountainous areas of southwestern China and the low rates of rainwater infiltration into low-permeability soils. We have built a new type of sunken green space structure with a combination of a "overflow port and rainwater storage layer" and carried out model tests of storage and drainage performance under heavy rain conditions. The hydrological response of the new composite structure parameters to the sunken green space was analyzed using the HYDRUS-2D program. The results show that the new composite structure has a significant impact on runoff reduction, drainage, and rainwater storage. For the 100a return period, compared with RSL-0 (0 cm rainwater storage layer), the initial and peak drainage times of RSL-25 were delayed by 30 min and 38 min, respectively, and the rainwater storage rate increased by 13.5%. Compared with no overflow port, the peak drainage increased by 78%, the initial drainage time advanced by 73 min, and the cumulative drainage volume increased by 186%. In addition, as the height of the overflow increased, the surface rainwater absorbed by the sunken green space gradually decreased. The sunken green space with OPH-5 (overflow port height of 5 cm) could absorb more than 75% of the rainwater in the rainwater overflow layer, while the absorption capacities of OPH-7.5 and OPH-10 (overflow port height of 7.5 cm and 10 cm) were basically below 75%. In this case, the OPH-5 and the depth of the storage layer not being less than 250 cm provide the best setting for the new combined structure of the sunken green space. In conclusion, the new composite structure designed in this experiment effectively increased the hydrological performance of the layered sunken green space.

Identifying the Long-Term Thermal Storage Stability of SBS-Polymer-Modified Asphalt, including Physical Indexes, Rheological Properties, and Micro-Structures Characteristics

The thermal storage stability of styrene–butadiene–styrene tri-block copolymer modified bitumen (SBSPMB) is the key to avoid performance attenuation during storage and transportation in pavement engineering. However, existing evaluation index softening point difference within 48 h (ΔSP48) cannot effectively distinguish this attenuation of SBSPMB. Thus, conventional physical indexes, rheological properties, and micro-structure characteristics of SBSPMB during a 10-day storage were investigated in this research. Results showed that during long-term thermal storage under 163 °C for 10 days, penetration, ductility, softening point, recovery rate (R%), and anti-rutting factor (G*/sinδ) were decayed with storage time increasing. This outcome was ascribed to the phase separation of SBS, which mainly occurred after a 4-day storage. However, ΔSP48 after a 6-day storage met the specification requirements (i.e., below 2.5 °C). Thus, the attenuation degree of asphalt performance in field storage was not effectively characterized by ΔSP48 alone. Results from network strength (I) and SBS swelling degree tests revealed that the primary cause was SBS degradation and base asphalt aging. Moreover, conventional indexes, including penetration, ductility, and softening point, were used to build a prediction model for rheological properties after long-term storage using partial least squares regression model, which can effectively predict I, R, Jnr, G*/sinδ, and SBS amount. Correlation coefficient is above 0.8. G*/sinδ and I at the top and bottom storage locations had high coefficient with SBS amount. Thus, phase separation of SBSPMB should be evaluated during thermal storage.

Comprehensive Understanding the Disaster-Causing Mechanism, Governance Dilemma and Targeted Countermeasures of Urban Pluvial Flooding in China

Urban pluvial flooding in China has become one of the major challenges for sustainable development. This paper analyzes the impact of climate change, urbanization, and integrated disaster drivers on urban pluvial flooding hazards, starting from the disaster-causing mechanisms of urban pluvial flooding in China. This paper then analyzes the main features and progress of urban pluvial flooding governance in China. In particular, this paper describes the progress of sponge cities in China. On the basis of the above contents, this paper describes three manifestations of the fragmentation dilemma at the level of governance, namely, fragmentation in value integration due to conflicting management orders and service values, fragmentation in resource and power allocation due to the lack of vertical top-level design and blurred horizontal departmental management boundaries, and fragmentation in policy formulation and implementation due to outdated urban flood control standards and interdepartmental information compartmentalization. In response to the fragmentation dilemma in urban pluvial flooding management in China, this paper introduces the concept of holistic governance and clarifies the path of urban waterlogging management, i.e., forming a collaborative and diversified governance subjects, deeply optimizing the organizational structure of urban waterlogging management, creating a mature information-based governance platform, and improving the legal and rule of law construction model. This paper is informative for understanding the governance of urban pluvial flooding in China from a government-led management level.

Understanding China’s Urban Rainstorm Waterlogging and Its Potential Governance

Urban rainstorm waterlogging is one of the most important problems in urban development and a comprehensive embodiment of urban diseases. China is facing a severe risk of rainstorm waterlogging disasters, which is affecting sustainable development. Urban rainstorm waterlogging in China is caused by many factors, including natural factors and human factors, such as climate warming, unreasonable urban construction, inadequate upgrading of urban fortification standards, etc. Based on the analysis of the current strategies to deal with urban waterlogging around the world, including an increase in surface infiltration, and a reduction in runoff (and its various impacts), this paper holds that the connotation and goal of these measures are highly consistent with the construction of a sponge city in China. Based on the analysis of the problems, including construction of an urban rainwater recovery system, construction of urban rainwater storage facilities, and construction of data platforms faced by China’s sponge city, this paper puts forward the guiding principles of promoting the construction of a sponge city. The guiding principles are to cooperate to deal with climate change and ecological civilization construction, to study the foreign experience, and to unite multiple subjects, integrate multiple elements, design multiple processes, form a joint force, and create an all-round response system to deal with urban rainstorm waterlogging. Then, this paper gives policy recommendations on how to deal with the urban rainstorm waterlogging disasters, which include improving the defense standards, encouraging social participation, popularizing the construction of sponge cities, perfecting the monitoring and early warning system, strengthening the scientific planning of cities, strengthening the ability of dealing with catastrophes in metropolitan areas, the overall planning of cross-regional responses, and enhancing the awareness of decision makers. Finally, this paper expounds the reference significance of urban rainstorm waterlogging control in China to the global audience. This paper explores the significance of comprehensively and scientifically understanding urban rainstorm waterlogging disasters, and provides support for long-term planning and high-quality construction of future safe cities.