Current Issue : April-June Volume : 2024 Issue Number : 2 Articles : 5 Articles
Microshield structure replacement technology is commonly used to control the freezing damage of railway roadbeds, featuring high efficiency and easy operation. However, improper disposal of measures in the construction process will still cause excessive deformation of the line and endanger the safety of train operations. On the background of a subgrade freezing damage improvement and speed improvement project of the Xige section of Quinghai–Tibet railway, this study performed numerical simulation of the microshield based on the measured data of the field automatic monitoring system to improve the operation safety of the existing lines and optimize the construction technology of the microshield. The effect of the changes in the microshield segment material, construction process, and formation loss on the settlement of the operating railway subgrade was analyzed to control the construction disturbance settlement of the existing operating line. The results obtained show that the overall settlement deformation of the line is small when the steel pipe is used as the shield segment, which meets the safety management requirements of the existing operating line. When PE tube segments are used for construction, construction measures should be strictly controlled to reduce the effect of settlement deformation on the operational lines. When steel pipe segments are used, the settlement generated by the construction process from both sides to the middle is minimal. When PE tube segments are adopted in the construction, the settlement generated by the construction process with unilateral advancement and an interval of two pipe diameters is the least, producing unimodal settlement curve of the line. The latter features a double peak when the shield pipe interval is three pipe diameters or more. When using PE tube pieces for the microshield construction, it is necessary to strictly control the formation loss rate within 10% by optimizing the construction control measures....
The construction industry has witnessed a surge in heat-related accidents alongside rising summertime temperatures, exposing workers to potential injuries. The absence of specific heat stress standards by the Occupational Safety and Health Administration (OSHA) underscores the urgent need for more comprehensive and interactive educational materials to prevent such incidents in construction projects. This study proposes the adoption of an interactive Virtual Reality (VR) application to offer construction workers realistic and effective training, mitigating heat-related injuries. During the training sessions, VR headsets were utilized to immerse workers in two lifelike scenarios: (1) Addressing self-care during heat exhaustion; (2) Assisting a coworker experiencing heat exhaustion. A case study evaluated the effectiveness of the proposed VR training for 82 construction workers from two companies. Company A had traditional training, while Company B used VR training. Both groups took pre- and post-assessment surveys with six questions. The pre-assessment found no significant knowledge difference between the groups. After training, VR showed a significant reduction in incorrect answers compared to traditional training. Statistical tests confirmed the superiority of VR training (p-value = 0.00152 < 0.05), suggesting its effectiveness in preventing heat-related injuries in construction compared to traditional training methods....
In the backdrop of China’s rapid economic growth and urbanization, the surge in construction waste poses mounting disposal challenges. This study primarily focuses on in-depth research and exploration of construction waste recycling technologies. By repurposing towering heaps of construction debris into artificial landscapes, it achieves resource reutilization and waste reduction, bearing profound significance for environmental protection, and resource utilization. Taking the Xi’an Meibei Lake Scenic Area construction waste embankment project as a case study, experiments on the physical properties of soil-construction waste mixtures were conducted. A three-dimensional computational model of the site was established, and typical cross-sections were selected for the slope stability calculations and analysis. This was coupled with on-site measurements to validate the practicality and effectiveness of the technology. The successful execution of the project has demonstrated the reliability of this technology, offering significant potential for widespread application and serving as a crucial reference for the similar projects....
Grinding aids (GAs) are polar chemicals introduced in cement mills in either liquid or powder form to improve on mill grindability efficiency. Studies have shown that some GAs not only help in grinding efficiency but also play vital roles in improving the product particle size distribution, product ability to flow in the mill, grinding energy reduction, and improvement on the separator efficiency. This review investigated the impacts of the GAs on the performance of some properties of cement when used as either mortar and/or concrete. The influence of the GAs incorporation in cement grinding on properties such as workability and setting times of the placed concrete and/or mortar has been covered in this review. The performance of GAs on ordinary portland cement (OPC) and blended cements with other supplementary cementitious materials such as pozzolana, fly ash, and slag has also been discussed. This is in view to tapping the maximum benefits of using GAs in cement production and use. This review work established that GAs have a positive influence on mill performance when properly applied. It further established that blended cements work better when dosed with additives such as GAs and/or quality improvers when compared to OPC. The review work demonstrated that some superplasticizers help in lowering the water demand in highly blended pozzolanic-based cements. The review finally recommended that the future course of action in the production of blended cements should apply GAs. This is in order to help produce highly replaced blended cements that are sustainable....
The construction of underwater shield tunnels under high water pressure conditions and seepage action will seriously impact the stability of the surrounding rock. In this study, an analytical model for the strength of the two-lane shield tunneling construction under anisotropic seepage conditions was established, and a series of simulations were carried out in the engineering background of the underwater section of Line 2 of the Taiyuan Metro in China, which passes through Yingze Lake. The results show that: (1) the surface settlement has a superposition effect, and the late consolidation and settlement of the soil body under seepage will affect the segment deformation and the monitoring should be strengthened; (2) under the influence of the weak permeability of the lining and grouting layers, the pore pressure on both sides of the tunnel arch girdle is reduced by about 72% compared with the initial value, with a larger hydraulic gradient and a 30% reduction at the top of the arch; (3) within a specific range, the tunneling pressure can be increased, and the grouting pressure and the thickness of grouting layer can be reduced to control the segment deformation; (4) the more significant the overlying water level is, the larger the maximum consolidation settlement and the influence range of surface settlement. This study can provide a reliable reference for underwater double-lane shield tunnel design and safety control....
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