Asphalt composite concrete pavement is one of the common pavement forms in China. However, due to the influence of design, materials, construction quality, and other aspects, asphalt composite concrete pavement develops various degrees of cracks after being put into use, which affects the service performance and life of asphalt pavement. The Burgers model is used to examine the effects of fiber-volume-fraction and length–diameter-ratio on the viscoelastic mechanical behavior model parameters and viscoelastic properties of asphalt composite concrete through the bend test for creep of polyester fiber asphalt composite concrete beam. The findings indicate that the fiber’s ability to control asphalt composite concrete bending creep deformation increases initially and subsequently diminishes as fiber-volume-fraction and length–diameter-ratio increase. Fiber-volume-fraction and length–diameter-ratio effects can be fully reflected by fiber amount characteristics. A viscoelastic mechanical behavior model of fiber-reinforced asphalt composite concrete is developed on this foundation while taking into account the influence of fiber amount characteristic factors. Theoretical study and practical research indicate that the ideal fiber volume ratio of polyester fiber asphalt composite concrete is 0.35 percent, the ideal length-to-diameter ratio is 324, and the ideal fiber amount characteristic parameter is 1.13. The test results can provide a certain reference value for the improvement of the long-term durability of fiber asphalt composite concrete pavement of road engineering.

High fluoride groundwater is a global environmental and public health issue. To explore the effects of fluoride in groundwater in the oasis of the Hotan River Basin in Xinjiang on human health, this study analyzed the content and spatial distribution of fluoride in groundwater. Moreover, health risk assessment was performed using the Monte Carlo method based on the Unite States Environmental Protection Agency (USEPA) model. The results revealed that the groundwater in the Hotan River Basin oasis has an average F⁻ content of 1.04 mg·L⁻¹, with an exceedance rate of 35.2%. High-fluoride groundwater is typically characterized by a high HCO₃⁻ content, low Ca²⁺ content relative to Mg²⁺ content, and the presence of hydrochemical types of Cl·HCO₃-Na and HCO₃-Na. The hazard quotient (HQ) of fluoride in groundwater > 1 for children and adults in Lop County, Karakax County, and Hotan city and for children in Hotan County. In the study area, the 1–95% quantile certainty of HQ is greater for children (58.30–38.74%) than for adults (52.65–28.26%). Therefore, most residents in the oasis are exposed to the nononcogenic health risks of fluoride in groundwater via the water drinking pathway, with children being highly sensitive. The fluoride content of groundwater in the study area significantly influences the nononcogenic health risk assessment for residents, with a variance contribution rate of 87.8–94.3%. Therefore, reducing the fluoride content in groundwater should be prioritized in decision-making regarding the safety of drinking water in the oasis.

Soil surfaces form complex crack networks as a result of water loss and shrinkage. A crack network destroys the integrity of the soil and becomes the main factor affecting rainfall infiltration, slope instability and soil integrity. In this paper, a soil fracture network is quantified using fractal characteristics and fractal dimensions, and the soil fracture network is identified and calculated using digital image processing technology. The fracture network of silty clay with different setaria viridis root content is studied during the process of evaporation. Saturated mud is prepared by taking soil samples and collecting setaria viridis roots. The content of setaria viridis roots in each saturated mud sample is 0 g, 0.1 g, 0.2 g and 0.3 g. In the artificial climate environment simulation system, thin-layer root soil is dried by controlling the temperature and humidity to simulate dry climate conditions. During the test, the crack development process is recorded using a digital camera. The results show that when the root content is 0, 0.1 g, 0.2 g and 0.3 g, the water content values when a fissure is generated are 35.2%, 41.2%, 42% and 46.4%, and the initial fractal dimension values are 1.100, 1.106, 1.112 and 1.115, respectively. The fractal dimension value increases rapidly in the early stage of fissure generation, and it reaches the maximum value when the water content reaches 13.66%, 15.2%, 15.66% and 17.98%, respectively. According to the change law of the fractal dimension, the fractal dimension increases rapidly following the initial appearance of the fracture, and, with a continuous reduction in water content in the later stage, the fracture characteristics gradually stabilize, and the change rate of the fractal dimension becomes slow.

Soil drying cracking is the most common natural phenomenon affecting soil stability. Due to the complexity of the geometric shapes of soil cracks during the cracking process, it has become a major problem in engineering science. The extremely irregular and complex crack networks formed in civil engineering materials can be quantitatively investigated using fractal theory. In this paper, fractal dimension is proposed to characterize the drying cracking characteristics of composite soil by adding recycled waste brick micro-powder. At the same time, the concept of the probability entropy of cracking is introduced to quantify the ordered state of crack development. Correspondingly, the endpoint value of probability entropy was solved mathematically, and the meaning of the probability entropy of cracking was clarified. In this study, the fracture fractal characteristics of composite soil mixed with different materials were first investigated. Then, five groups of composite soil-saturated muds with added recycled waste brick micro-powder of different contents were prepared in the laboratory. Using the evaporation test under constant temperature and humidity, the change rules of the fractal dimensions, probability entropy, crack ratios, and water contents of cracks during the cracking process of the soil samples were obtained. The results show that: (1) on the whole, the fractal dimensions of the soil samples added with recycled waste brick micro-powder of different contents increased over time, and the fractal dimensions of the soil samples without recycled waste brick micro-powder were obviously larger than those of the soil samples with recycled waste brick micro-powder. With the increase in the content of recycled waste brick micro-powder, the maximum fractal dimension decreased in turn. The maximum fractal dimensions of the five groups of soil samples were 1.74, 1.68, 1.62, 1.57, and 1.45. (2) The change trends of the probability entropy and fractal dimensions were similar; both of them showed an upward trend over time, and the probability entropy of the soil samples without recycled waste brick micro-powder was greater than that of the soil samples with recycled waste brick micro-powder. With the increase in the contents of recycled waste brick micro-powder, the probability entropy decreased in turn. The maximum values of the crack probability entropy of the five groups of soil samples were 0.99, 0.92, 0.87, 0.83, and 0.80. (3) Under the action of continuous evaporation, the moisture contents of the soil samples gradually decreased over time, while the crack ratios increased over time. To sum up, both from the perspective of the development process of the cracks of the soil samples and from the perspective of the final stable crack networks of the soil samples, the geometric shapes of the cracks of the soil samples without recycled waste brick micro-powder were the most complex. With the increase in the content of recycled waste brick micro-powder, the fractal characteristics of the cracks gradually changed from complex to simple.

Carbon fiber is a common waste building material, but its effect on the drying and cracking properties of clay materials is unknown. In this paper, crack rate and fractal dimension are used to characterize the influence of waste carbon fiber materials on the development of soil cracking. With the rise in carbon fiber content to 0.2%, 0.4% and 0.6%, the crack rate of soil cracking decreased by 7.9%, 17.3% and 23.3%, respectively, while the fractal dimension of soil cracking decreased by 2.4%, 8.7% and 21.2%, respectively. Accordingly, the critical moisture content of the soil samples increased by 33.2%, 110% and 151%, and the time of the soil constant evaporation stage decreased by 5.1%, 13.8% and 34.5%, respectively. When carbon fiber is combined with soil, carbon fiber will increase the interface bonding strength, friction and interlocking force, effectively inhibiting the cracking of soil, and it provides a channel for water transport in the soil in the early stage.

Under the influence of internal and external factors, a fracture network is easily generated in concrete and rock, which seriously endangers project safety. Fractal theory can be used to describe the formation and development of the fracture network and characterize its structure. Based on the flow balance in the node balance field, Forchheimer’s law is introduced to derive the control equation of high-velocity non-Darcy flow in the fracture network. The fracture network is established according to the geological parameters of Sellafield, Cumbria, England. A total of 120 internal fracture networks are intercepted according to 10 dimensions (1 m, 2 m, …, 10 m) and 12 directions (0°, 30°, …, 330°). The fractal dimension, equivalent hydraulic conductivity (K), and equivalent non-Darcy coefficient ($\beta$) of the fracture network are calculated, and the influence of the fractal dimension on K and $\beta$ is studied. The results indicate that the fractal dimension of the fracture network has a size effect; with the increase in the size, the fractal dimension of the fracture network undergoes three stages: rapid increase, slow increase, and stabilization. In the rapid increase stage, K and $\beta$ do not exist. In the slow increase stage, K exists and is stable, and $\beta$ does not exist. In the stabilization stage, K and $\beta$ both exist and are stable. The principal axes of the fitted seepage ellipses of K and $\beta$ are orthogonal, and the main influencing factors are the direction and continuity of the fracture.