As regards the carbon emission levels of the logistics stage of prefabricated buildings, this study aims to fill the gap in scientific and unified carbon emission calculation models and standards. Thus, the calculation boundary for carbon emissions was first defined in this study. Secondly, various carbon emission factors related to China’s energy consumption characteristics were summarized. Subsequently, a carbon emission calculation model for the logistics stage was established, based on the carbon emission factor method. Finally, taking a project as an example, the carbon emission level at the transportation stage was calculated using the proposed model. The effect of full-load rates on the carbon emission levels of prefabricated components was also evaluated. The results demonstrate that the full-load rate has a significant effect on carbon emissions during the transportation stage (54.32% reduction in carbon emissions at 100% full load). Therefore, increasing the full-load rate can reduce carbon emissions from transportation, as long as the loading requirements are met.

Aiming at the uncertainty in the existing tunnel surrounding rock stability evaluation methods and the inability to make scientific explanations in the process of determining the weights of multiple evaluation indicators, this paper combines subjective weighting based on the nonlinear characteristics of the surrounding rock stability evaluation criteria. Based on the advantages of the method AHP and the objective weighting method CRITIC, a comprehensive weighting method with multiple evaluation indicators is proposed, which is integrated with the multidimensional normal cloud model to establish a surrounding rock stability evaluation method for the improved weighted multidimensional cloud model and accurately obtain the safety level of tunnel surrounding rock construction. The multidimensional cloud model based on improved weighting not only solves the two major problems of randomness and ambiguity in surrounding rock stability evaluation but also fully considers the influence of the information contained in each evaluation factor on the results. The surrounding rock stability evaluation method in this paper is applied to the tunnel construction of the Beijing‐Shanghai Expressway and Jinan Expressway connecting line construction project, and the evaluation results have a scientific guiding role for construction risk control.

The waterproof sealing performance of the shield tail sealing system is an important factor to ensure the safe construction of shield tunnels. This paper focuses on analyzing the shield project of the Wuhan metro, specifically examining the spatial arrangement of the shield tail sealing cavity and tail brush. By incorporating the linear permeability of the tail brush into our model, we aim to conduct numerical simulations using computational fluid dynamics (CFD) to investigate the performance of the shield tail sealing system under high water pressure. This study delves into the flow patterns of water and grease in the event of a failure in the shield tail sealing system. We aim to investigate how various parameters, including the structure of the shield tail brush, properties of the grease used, and other conditions, impact the waterproof sealing performance. The results show that under high-pressure water intrusion into the shield tail sealing system, water tends to permeate primarily through the bottom of the shield tail brush, which exhibits the highest permeability. This creates a dominant flow channel within the grease cavity. The failure process of the shield tail sealing is divided into five stages. Between pressure differences of ΔP = 0 to 1 MPa, the sealing ability of the shield tail shows minimal variation. Increasing the viscosity of grease and reducing the permeability of the tail brush can effectively prolong the breakdown time and enhance the safety capability of the shield tail. Beyond a pressure difference of ΔP = 1 MPa, these measures generally prove ineffective. Utilizing this model and the designated time limit for shield tail failure, we propose optimal grease and tail brush parameters to guide the safe construction of shield tunnels.