A collaborative approach for urban underground space development toward sustainable development goals: Critical dimensions and future directions

A LSTM-RNN based intelligent control approach for temperature and humidity environment of urban utility tunnels

Temperature and relative humidity are important indicators of utility tunnel indoor atmosphere hazards and operational risks, which can be effectively mitigated by accurate forecasting and corrective control measures. To this end, this paper proposed a multi-layer long short-term memory (LSTM) recurrent neural network (RNN) architecture to forecast the changing trend of temperature and relative humidity inside utility tunnels with distant past monitoring data. Based on the forecasting architecture, an intelligent control approach was designed, including early warning and ventilation control measures. Case study results showed that the proposed architecture fit the training dataset well and the prediction accuracy on testing datasets of temperature and relative humidity exceeded 98% and 99%, respectively. Meanwhile, the proposed LSTM-RNN architecture can also be used to simulate and evaluate the ventilation effects on the temperature and relative humidity environment of urban utility tunnels. Findings of this paper provide a reference for the safe, efficient and energy-saving indoor environment control of urban utility tunnels.

Experimental Research on the Workability and Mechanical Properties of Grouting Materials with Nano-Oxides

This work studied the effect of the nano-oxides, such as Nano-Fe₂O₃ (NF), Nano-Al₂O₃ (NA), Nano-MgO (NM), and Nano-SiO₂ (NS), on the workability and mechanical properties of quick-setting grouting materials serviced in the underground environment. The results show that 2.0% NS could remarkably shorten the setting time of the grouting materials by 29.16%, compared to the control one (without nano-oxides), and the final setting time was shortened by 46.51%. The results also show that 2.0% NS could decrease the initial fluidity of the grouting material by 41.09%, compared to the control one, and the 30 min fluidity was decreased by 48.93%. The XRD results show that NF, NM, and NS contribute to a higher quantity of AFt than that NA. Moreover, grouting material doped with NF, NM, and NS produces more needle-like ettringite, leading to a more compact structure.

Data Analysis and Optimization of Thermal Environment in Underground Commercial Building in Zhengzhou, China

Underground commercial buildings have received increasing attention as an emerging place of consumption. However, previous studies on underground commercial buildings have mainly focused on the impact of a specific environment on comfort or energy consumption. Few studies have been conducted from the perspective of functional use. The purpose of this paper is to investigate, in terms of functional angles, the indoor thermal environment and air quality of an underground commercial building in Zhengzhou, China, and put forward an optimal control strategy of ventilation organization. The results showed that the relative humidity of the underground shopping mall was generally above 60%, and the average temperature of 29.1 °C led to a thermal comfort problem in the catering area in summer. Meanwhile, the concentration of CO2 exceeded the allowed figures during the peak of the customer flow rate, and PM2.5 concentration in the catering area also exceeded the standard, by 43.3% and 33.3%, respectively. Furthermore, to solve the indoor thermal environment and air quality problems found in the field measurements, this study assessed the air distribution by adopting three different air supply schemes for the catering area. Optimization results showed that compared with the ceiling supply, the side supply scheme kept the air temperature 0.4 °C cooler in summer and 0.5 °C warmer in winter. The temperature uniformity increased by 5.4% and 3.7%, and the velocity uniformity increased by 6.5% and 8.8%, respectively. This study can provide theoretical support for thermal environment construction and ventilation organization control of underground commercial buildings.