Pervious concrete is considered to be porous concrete because of its pore structure and excellent permeability. In general, larger porosity will increase the permeability coefficient, but will significantly decrease the compressive strength. The effects of water-cement ratio, fiber types, and fiber content on the permeability coefficient, porosity, compressive strength, and flexural strength were investigated. The pore tortuosity of the pervious concrete was determined by volumetric analysis and two-dimensional cross-sectional image analysis. The concept and calculation method of porosity tortuosity were further proposed. Results show that the permeability coefficient of the pervious concrete is the most suitable with a water-cement ratio of 0.30; the water permeability of the pervious concrete is influenced by fiber diameter. The permeability coefficient of pervious concrete with polypropylene thick fiber (PPTF) is greater than that with copper coated steel fiber (CCF) and the polypropylene fiber (PPF). The permeability coefficient is related to tortuosity and porosity, but when porosity is the same, the permeability coefficient may be different. Finally, general relations between the permeability coefficient and porosity tortuosity are constructed.

The behavior of steel fiber concrete, which is the most widely used building material, has been widely examined. However, methods for calculating Fracture parameters differ by fracture behavior of SFHSC with different strengths. In this study, the fracture behavior of steel-fiber-reinforced high-strength concrete (SFHSC) was -investigated using three-point bending tests. A total of 144 notched concrete beams with a size of 100 mm × 100 mm × 515 mm were tested for three-point bending in 26 groups. The effects of the steel fiber volume ratio, steel fiber type, and relative notch depth on the fracture toughness (K_IC) and fracture energy (G_F) of SFHSC specimens were studied. The results show that an increase in the volume fraction of steel fiber (ρ_f) added to high-strength concrete (HSC) significantly improves the fracture behavior of HSC. As compared to milled and sheared corrugated steel fibers, cut bow steel fibers significantly improve the fracture behavior of SFHSC. The effect of incision depth changes on the K_IC and G_F of SFHSC and HSC for the comparison group has no common characteristics. With an increase in incision depth, the values of K_IC of the SFHSC specimens decrease slightly. The G_F0.5/G_F0.4 of the SFHSC specimens show a decreasing trend with an increase in ρ_f. According to the test results, we propose calculation models for the fracture behavior of SFHSC with different strengths. Thus, we present a convenient and accurate method to calculate fracture parameters, which lays a foundation for subsequent research.

This study aimed to determine the influence of the volume fraction of steel fibers on the fracture parameters of concrete. Fifty notched steel-fiber-reinforced concrete (SFRC) beams and ordinary concrete beams with 100 mm × 100 mm × 515 mm were cast and tested via a three-point bending test. Among them, the type of steel fiber was the milling type (MF), and the volume fraction of steel fiber added was 0%, 0.5%, 1%, 1.5% and 2%, respectively. The effects of the steel fiber volume fraction (V_F) on the critical stress intensity factor (K_IC), fracture energy (G_F), the deflection at failure(δ₀), the critical crack mouth opening displacement (CMOD_C) and the critical crack tip opening displacement (CTOD_C) were studied. Through the analysis of test phenomena and test data such as the load-deflection (P-δ) curve, load-crack mouth opening displacement (P-CMOD) curve and load-crack tip opening displacement (P-CTOD) curve, the following conclusions are drawn: with the increase of the steel fiber volume fraction, some fracture parameters increase gradually and maintain a certain linear growth. The gain ratio of the fracture parameters increases significantly, and the gain effect is obvious. Through this law of growth, the experimental statistical formulas of fracture energy and the critical stress intensity factor are summarized.

Water resources, the social economy, and the ecological environment are interrelated and interacting complex systems, and the relationship among them affects the sustainable development of a region. To explore the interactive relationship and driving factors between water resources, the social economy, and the ecological environment, the Yellow River Golden Triangle region is taken as the research object in this paper. By constructing a coupling-coordination evaluation index system of water resources, the social economy, and the ecological environment system, the coupling-coordination development of this region from 2011 to 2021 is studied using the coupling-coordination degree model, and the influencing factors of coupling-coordination development are identified by gray relational analysis. The results show that from 2011 to 2021, the comprehensive evaluation index of the water resources, social economy, and ecological environment in the Yellow River Golden Triangle region shows a trend of steady development followed by a gradual increase. The water-resources subsystem restricts the development of the coupling system. The coupling-coordination degree increased from a barely coordinated stage in 2011 to a well-coordinated stage in 2021. The social economy subsystem and water-resources subsystem are the main factors affecting the coordinated development of the coupling system.