Numerical Simulation of the Stability of Rock Mass around Large Underground Cavern

Geotechnical problems are complicated to the extent and cannot be expected in other areas since non-uniformities of existing discontinuous, pores in materials and various properties of the components. At present, it is extremely difficult to develop a program for tunnel analysis that considers all complicated factors. However, tunnel analysis has made remarkable growth for the past several years due to the development of numerical analysis method and computer development, given the situation that it was difficult to solve formula of elasticity, viscoelasticity, and plasticity for the dynamic feature of the ground when the constituent laws, yielding conditions of ground materials, geometrical shape and boundary conditions of the structure were simulated in the past. The stability of rock mass around an underground large cavern is the key to the construction of large-scale underground projects. In this paper, the stability analysis was carried out based on those parameters by using 2D FEM RS2 program. The calculated stress and displacements of surrounding rock and rock support by FEM analysis were compared with those allowable values. The pattern of deformation, stress state, and the distribution of plastic areas are analyzed. Finally, the whole stability of surrounding rock mass of underground caverns was evaluated by Rock Science - RS2 software. The calculated axial forces were far below design capacity of rock bolts. The strong rock mass strength and high horizontal to vertical stress ratio enhanced safe working conditions throughout the excavation period. Thus wide span caverns and the system of caverns could be stability excavated sedimentary rock during the underground cavern and the system of caverns excavation by blasting method. The new method provides a reliable way to analyze the stability of the caverns and the system of caverns and also will help to design or optimize the subsequent support. Doi: 10.28991/CEJ-2022-08-01-06 Full Text: PDF

What Is the Knowledge of Evacuation Procedures in Road Tunnels? Survey Results of Users in Poland

This paper presents a preliminary assessment of road tunnel safety issues among respondents—specifically, real and potential users of road tunnels. We recruited a group of respondents to study their knowledge of evacuation procedures and awareness of safety issues in road tunnels. We conducted surveys with 504 participants, 12.7% of whom had previously participated in real-scale evacuation experiments in a road tunnel. Analysis of respondents’ answers reveals that their knowledge of safety procedures is unfortunately not sufficient. On average, the respondents selected the most recommended answer for approximately 5.35 out of 15 questions. Only 16% of respondents correctly answered more than 50% of the survey questions; moreover, no respondent provided the correct answers for 12 or more questions. Interestingly, most respondents were convinced that they had a better knowledge of road tunnel safety issues than was actually the case. The results of the survey demonstrate a significant educational role of evacuation exercises. Individuals who have participated in an evacuation have better knowledge, allowing them to apply the correct rules of road tunnel safety procedures. Various aspects addressed in this paper can be taken into consideration in an information campaign regarding safety in road tunnels during a fire.

Refrigeration Capacity and Effect of Ageing on the Operation of Cellulose Evaporative Cooling Pads, by Wind Tunnel Analysis

This study investigates the temperature reduction capacity and water consumption of a fan-pad system installed in a greenhouse located in the coastal regions of Almería. The suitability of this system for coastal zones with high environmental humidity during the summer is analyzed. Historical temperature and relative humidity series are studied, obtaining the thermal difference and maximum, medium, and minimum monthly water consumption of the pads based on the operation data of the pads. Despite the high relative humidity of the air in the hottest hours of the day, a decrease of 5.92 °C in the mean temperature and a water consumption of 13.55 l/h per square meter of an evaporative cooling pad are obtained in the month of August. Additionally, the operation of a cellulose evaporative cooling pad installed for 3 years in a greenhouse is analyzed in a wind tunnel and compared with that of a new pad of the same model. Over time and with low maintenance, the porosity of the pad decreases due to salt incrustation. The salt incrustation makes airflow more difficult in the pad, increasing the pressure drop by 170.04%; however, the air saturation efficiency of the pad increases by 6.6% due to the greater contact time between the air and the water.