In recent years, owing to the advancement of highway infrastructure, modified asphalt has been extensively employed in pavement engineering. Asphalt mixture will invade the soil under high-temperature conditions, affecting soil cracking. Cracking characteristics caused by dryness of the mixed samples of modified asphalt and soil accounting for 0%, 2.5%, 5%, and 7.5% of the total weight were investigated in this paper. According to the water loss situation, the degree of cracking was determined. The crack development was quantitatively analyzed by digital image processing technology, so as to analyze the influence of modified asphalt on soil cracking under different contents. The results show that the soil was relatively better than the normal state. Under the same conditions, the moisture content of modified asphalt soil with 2.5%, 5%, and 7.5% increased by 30.17%, 63.49%, and 110.37% compared with that without modified asphalt. At the same time, due to its special bonding properties, it can effectively improve the cracking of soil. The cracking rate of modified asphalt soil with 2.5%, 5%, and 7.5% content is reduced by 11.58%, 20%, and 31.58%, respectively. The soil added with modified asphalt can effectively increase the total porosity of the soil, thus improving the ability of water absorption, and also can well inhibit the rate of soil evaporation and reduce cracking. Modified asphalt can be rationally applied not only to have soil mechanical properties improved but also to have waste asphalt utilized to reduce environmental pollution.

Cracking of soils associated with subsidence is a complex and multiparametric problem. Local soil conditions could be responsible for the dramatic differential settlements and fissures manifest when the water pumping reduces the volume of the compressible strata. This situation is of extreme importance due to the level of damage to urban infrastructure and buried facilities (gas, water, and drainage) as well as to housing structures. In this research, using a simple geotechnical model of subsidence (finite element method, Mohr-Coulomb criterion) parametric combinations of materials and basement geometry are tested to define the geotechnical settings more susceptible to deformation and derived cracking. These approximations are compared with measurements and field surveys in Mexico City to validate the hypothesis. Defining the zones that are more susceptible to respond with cracking due to the phenomenon of subsidence can be especially important when designing urban development programs, restoration campaigns for buried pipes, even for construction and operation of new pumping wells.

Purpose: Modifying soil surface conditions is essential in managing water and soil resources. Although the use of soil microorganisms in the bioengineering management in soil and water conservation has been confirmed, the controllability of the surface cracks morphometry on petroleum-contaminated soils using microorganisms has yet to be studied. Therefore, this study aimed to investigate the effect of inoculating soil microorganisms on changing the surface cracks' pattern of soil contaminated with petroleum.Materials and methods: In 2022, the studied soil was taken from Iran's Tehran Oil Refinery area from the top 30 cm of the earth's surface and transferred to the Rain and Erosion Simulation Laboratory of Tarbiat Modares University at the Faculty of Natural Resources. The predominant cyanobacteria of Microcoleus sp. Oscillatoria sp. Lyngbya sp. Nostoc sp, and Phormidium sp. bacteria of Bacillus sp. and Azetobacter sp. fungus of Penicillium oxalicum were identified, purified and proliferated. The study was conducted at a 0.5 x 0.5-m plot scale in two replications for four treatments. Uncontaminated and gasoil-contaminated soils, during one month, were inoculated by bacteria, cyanobacteria, and fungus. The soil was contaminated using 720 mL of gasoil evenly sprayed. The morphometric characteristics of soil surface cracks were investigated using the PCAS software.Results and discussion: Results indicated that soil microorganisms influence the soil cracking patterns. So, the mean area, length, and width of cracks increased by 99.55%, 50.90%, and 29.60% in uncontaminated plots inoculated with cyanobacteria compared to the control treatment. In gasoil treatment, fungus-inoculated soils performed better than control plots, and the mean area and length increased by 19.51% and 29.58%, respectively, while width decreased by 17.29%. Microorganisms caused the agglutination of aggregates by secreting enzymes and exopolysaccharides, stabilizing soil particles, generating cracks, covering the soil surface, and improving the soil's rheological properties.Conclusion: Finally, the results of the present study showed that modifying the surface of the petroleum-contaminated soil by inoculating soil microorganisms is a way to improve the hydrologic and rheologic characteristics of the soil.

Increasing soil salinization and microplastics (MPs) pollution of farmland have become global agricultural issues that have to be faced, destabilizing plant-soil systems and bringing threats to ecosystems. Few studies have focused on the effects of MPs on saline soil water evaporation and desiccation crack formation, and the underlying influencing mechanisms of MPs and salts in soils. A mechanism test was conducted to explore the effects of MPs concentrations (0.5 %, 1 %, 3 %, w/w) on the simultaneous changes of water evaporation and cracking patterns of saline soils with different salinities (0, 0.1 %, 0.3 %, 0.5 %, w/w). Quantitative findings showed that (1) the MPs significantly reduced saturated conductivity by 14.9-46.8 % and 4.6-54.5 % in non-saline soil and lightly saline soil, respectively, which showed a decreasing trend with increasing MPs concentration; besides, soil salts also significantly reduced saturated conductivity, but the inhibition weakened with increasing soil salinity. (2) The MPs significantly reduced total porosity by 2.2-7.9 % and 1.8-6.6 % in non-saline and saline soils, respectively, which exhibited a slight decreasing trend with increasing MPs concentration. (3) The MPs reduced total evaporation by 0.4-6.1 % and 0.9-6.5 % in non-saline and saline soils, respectively. As the MPs concentration increased, the total evaporation of non-saline soil decreased, and the total evaporation of saline soils firstly decreased and then increased. After evaporation, both soil salt and MPs inhibited cracking. Correlations indicated that the presence of soil salt and MPs and their interactions explained more than half of the variability of soil and water characteristics and crack parameters. Mechanism exploration suggested that the MPs affect the evaporation process and crack behavior by changing soil pore size distribution, damaging soil structure, and the water repellency of the MPs particles; besides, the salts inhibit the soil water evaporation and surface cracking through increasing osmotic suction, blocking soil macropores, and promoting inter-microaggregate cementation. Our findings provide evidences for MPs influences on saline soil physical properties, water evaporation, and crack development, deserving attentions to the regulations and developments of soil-crop systems that facing salinization and plastic pollution.