Municipal solid waste incineration bottom ash (MSWIBA) emerges as a potential alternative to natural aggregates due to its similar mineral composition and engineering properties as embanking fillings. However, the instability and environmental pollution risks of MSWIBA limit its large-scale application. This study proposes to employ Enzyme Induced Carbonate Precipitation (EICP) technology to enhance the mechanical properties of MSWIBA and reduce its environmental impact. Initial analyses focused on the basic physicochemical properties and morphological changes of MSWIBA before and after modification. Then the modified MSWIBA exhibited improvements in shear resistance, resilient modulus, and permanent deformation behavior. It was also found that existing resilient modulus and permanent deformation predicting models for soils are applicable to EICPmodified MSWIBA. The column leaching tests were conducted on samples subjected and not subjected to freeze-thaw and dry-wet cycles. The results revealed the modified MSWIBA released reduced heavy metal concentrations in both water and acid leaches. These findings establish a solid theoretical foundation for employing EICP-modified MSWIBA as an embankment fill material, highlighting the potential for wider adoption of this eco-friendly alternative in road constructions.

Recovery of field samples provides unique information about the strength and the long-term functionality of deep stabilized soil in actual transportation infrastructures. This paper presents the results of uniaxial compressive tests for the stabilized field samples of two railway sites and one street site located in Finland. Based on the research findings, there is considerable variation in the shear strength of the field samples, with coefficients of variation (COV) ranging from 0.12 to 0.61. However, the average strengths across all sites achieved their target values set during design. The results demonstrate a significant increase in strength over time, especially at the older research sites. In a railway site where deep stabilization was performed 3.5 years ago, the average shear strength of the stabilization was 797 kPa, which is more than seven times greater than the target strength for the stabilized columns. The relationships between shear strength and deformation ratios for the columns and soil surrounding the columns exceed the assumed ratio values presented in the guidelines of Finnish Transport Infrastructure Agency (FTIA), which present a value of less than 20 for completed stabilization. Based on the results of all sites, the deformation ratio between columns and clay was found to be as much as 101. This result implies that the stress concentrates more on the columns than assumed in the FTIA's guidelines. Nevertheless, the structures have performed well without any visible differences in settlement or other damages.

In recent years, there has been a concerning increase in road collapses triggered by failures in urban drainage systems. Concrete pipes, commonly uesd in urban drainage pipelines, endure prolonged cyclic loading from traffic above. However, the mechanisms governing the long-term performance and fatigue damage remain unclear. Through conducting fatigue model box tests on concrete pipes, the effects of different fatigue loading cycles on the circumferential strain of concrete pipes were investigated. A fatigue life prediction equation for concrete pipes was proposed, and the crack propagation under various fatigue loading cycles was observed. Additionally, corresponding 3D FE models of concrete pipe-soil interaction with bell-and-spigot joints and gaskets were constructed. These models were used to explore the vertical displacements, circumferential bending moments, and circumferential stresses of the concrete pipes under different fatigue loading cycles, the damage and failure mechanisms of the concrete pipes under fatigue loading were revealed. The results indicate that the potential failure location of concrete pipes is within the inner crown of the bell under the fatigue traffic loads. The circumferential strains and crack propagation exhibiting a three-stage evolution pattern under fatigue loads. The proposed fatigue life prediction equation accurately predicts the remaining life of concrete pipes. Upon reaching 21.89 million loading cycles, the strain at the inner crown of the bell reaches 575.0 mu epsilon, resulting in complete failure. Cracks on the inner crown of the bell extend inward and to the right from the middle of the joint, forming a channel for crack propagation. The vertical displacements at the crown and the circumferential bending moments of the bell and spigot exhibit rapid increases, stabilization, and subsequent declines with the increasing loading cycles. When concrete pipes undergo fatigue fracture, the maximum vertical displacement and circumferential bending moment at the bell are measured as 2.26 mm and 17.82 kN & sdot;m/m, respectively. Stress concentration at the bell and spigot during fatigue loading leads to crack propagation and convergence, causing redistribution of stress fields characterized by an initial increase followed by a decrease in the inner crown and invert of the bell.

Large amounts of steel slag (SS) stockpiled and buried leads to land occupation, and is prone to cause soil and water contamination. Partially replacing natural minerals in pavement construction can contribute to the rapid consumption of stockpiled SS, but its poor volume stability limits its widespread adoption into engineering applications. Meanwhile, the potential leaching of hazardous substances (HS) should also be emphasized. This study prepared different pretreated SSs and asphalt mixtures. The differences and improvement mechanisms of the pretreatment on the SS properties were investigated through micro-morphology and chemical composition analyses. The physical properties of different SS and the long-term volume stability and moisture damage resistance of the steel slag asphalt mixture (SSAM) were tested. Moreover, a revised HS leaching test method for the SSAM was proposed, and the effectiveness of various pretreatment methods in reducing HS leaching was evaluated. The results revealed that the porous characteristics and free oxides contained in SS were the main obstacles to their large-scale application in pavement engineering. Natural aging, thermal immersion, and acid modification alter the composition of SS through chemical reactions and accelerate the consumption of free oxides. The polymer film formed by the silane coupling agent on the SS surface mitigated the environmental effects on the performance. The long-term performance of the SSAMs was improved, and the amount of HS precipitated was significantly reduced. Acetic acid modification and surface treatments are recommended because they are more effective in improving moisture damage resistance and reducing potential adverse environmental impacts. The findings are significant for reasonable pretreatment and application of converted SS as well as for contributing to the sustainable development of transportation infrastructure.