Foam concrete (FC) has the potential of being an alternative to ordinary concrete, as it reduces dead loads on the structure and foundation, contributes to energy conservation, and lowers the cost of production and labor cost during the construction and transportation. The paper reports a state‐of‐the‐art review of foam concrete in terms of its components, manufacturing and material properties like drying shrinkage, compressive strength, stability and pore structure, etc. In view of the significance of the FC in engineering construction, it also includes a state‐of‐the‐practice review of foam concrete in tunnel and underground engineering. Some shortcomings and technical limitations as well as emerging direction for performance enhancement of FC are also discussed. Current review concludes that the long‐term performance and enhancement‐associated properties need to be deeply investigated. This study can help alleviate consumer concerns and further encourage the wider application of FC in civil engineering.

Tunnelling or undertaking below‐ground construction in squeezing ground can always present many engineering surprises, in which this complicated geology bring a series of tunnelling difficulties. Obviously, if the major affecting factors and mechanism of the structure damage in these complicated geological conditions are determined accurately, fewer problems will be faced during the tunnel excavation. For this study, reference is made to four tunnel cases located in the Qingling‐Daba mountainous squeezing area that are dominated by a strong tectonic uplift and diversified geological structures. This paper establishes a strong support system suitable for a squeezing tunnel for the purpose of addressing problems exhibited in the extreme deformation of rock mass, structure crack, or even failure during excavation phase. This support system contains a number of temporary support measures used for ensuring the stability of tunnel face during tunnelling. The final support system was constructed, including some key techniques such as the employment of the foot reinforcement bolt (FRB), an overall strong support measure, and more reserved deformation. Results in this case study showed significant effectiveness of the support systems along with a safe and efficient construction process. The tunnel support system proposed in this paper can be helpful to support design and provide sufficient support and arrangement before tunnel construction in squeezing ground.

Self-gravity is one key parameter for behavior characterization of grout permeation and diffusion. This study proposes mathematical models for permeation grouting with consideration of grout self-gravity effect. The models concerning power law, Bingham, and Newtonian grouts are based on the generalized Darcy’s law and spherical diffusion theory. In addition, a prediction model of grout concretion dimension used for Bingham grout was developed. An analysis of the injection pressure distribution law and a comparative evaluation of diffusion radius considering self-gravity effect using established models were conducted subsequently. Moreover, grouting experiments were performed to check and verify the prediction model. The experimental results showed that injection pressure decreases linearly with increase of diffusion radius for the power-law grout, while nonlinear decrease of injection pressure was confirmed in Bingham and Newtonian grouts in this case. Three grouts approximately diffuse in an “ellipsoidal” shape, and it is confirmed that the diffusion radius is closely related to grout self-gravity. The Newtonian grout produces the maximum diffusion radius compared with the other two grouts whether the gravity effects were considered or not. The grout quantity under a smaller water-to-cement w/c ratio exhibits a significant difference and undergoes two increasing stages, whereas the quantity simply tends to be stable after it reaches its maximum in terms of the larger w/c ratios. The constructed dimension prediction model agrees well with the experimental results, which can be helpful for design and assessment of the grouting scheme.

Longitudinal ventilation systems are commonly installed in new tunnels. In this paper, based on the similarity law, the scale model with a view to different conditions is carried out to study the effectiveness of twin-tunnel complementary ventilation system. The system can offer enough amount of fresh air to meet requirement of driving safety by using longitudinal ventilation without ventilation shaft. Field measurements were also performed to validate the numerical model. Results reveal that particle concentration distribution is influenced by the distance from air interchange cross-passages to uphill tunnel inlet (Lex) and the flow volume of air interchange cross (Qex) passage and jet fan thrust (Pjet) in tunnel. And Lex is the most important factor about influencing the ventilation efficiency.

Background: The primary objective of this study is to ascertain whether the Expectation Confirmation Model can be expanded by external variables including computer anxiety, social interaction, and self-efficacy to better understand the intention to continue using online learning systems in the post-pandemic era among vocational college students. Moreover, this research argues that the intention to continue using online learning systems among students may be gender-sensitive.Methods: The researchers surveyed 482 students from eight vocational colleges in Jiangxi Province using a structured questionnaire. Partial Least Squares Structural equation modeling is used to verify the research model.Results: The outcomes demonstrate that the proposed model adequately explains the continuous use intention for online learning systems at a 76.6% confidence level. All of the newly introduced variables in the ECM are shown to be significant and relevant to explicate continuous use intention. Our survey results show that gender differences in intention to continue using online learning systems exist objectively, but this difference is not a natural difference.Conclusion: This research fills a void in the current literature on online learning and probes into how learning may be made more long-lasting in intricate environments.

A method of load calculation in a tunnel was adopted in consideration of the state of covering depth. Due to the macropore characteristics of loess soil, the existing demarcation regulations of deep and shallow tunnels are inappropriate for large-section and shallow loess in highway tunnels. To determine the load of large-section loess tunnel and provide a proper reference for structural design, the theoretical basis for distinguishing depth of deep and shallow tunnels, as well as the characteristics of common calculation methods for surrounding rock load on depth, were analyzed. Through statistical analysis and significance analysis, the significance of the variation of surrounding rock pressure with cover depth was studied. Correlation analysis was carried out on significant results to fit the relationship between cover depth and surrounding rock pressure. The results showed that the surrounding rock pressure varied linearly with the cover depth, and the surrounding rock pressure was about 0.3 times the initial pressure in deep tunnels. The surrounding rock pressure of shallow tunnels did not change significantly with the cover depth, and the surrounding rock pressure was loose pressure. A method based on statistics was proposed to distinguish the cover depth threshold (CDT) of deep and shallow tunnels.