Kai Wang

Taxiing is one of the most important operational processes in airports. Accurately predicting aircraft taxi time is essential for achieving efficient and robust airport management. In recent decades, taxi time prediction has received considerable research attention and machine learning prediction algorithms are perhaps the most popular methods in this field. However, existing research mainly concentrates on developing various taxi time prediction methods by adopting existing machine learning models and testing their performance is different airports. Another vital process, i.e., feature selection, receives relatively less attention, which may lead to some unnecessary features being involved in the taxi time prediction process and eventually reducing the overall prediction accuracy. To address the shortage of traditional prediction methods, this study integrates a popular feature selection technique with different machine learning models to develop more efficient taxi time prediction methods. Before starting the prediction process, the RReliefF feature selection method is employed to identify important features and form the feature subset, which is helpful to not only improve the prediction accuracy but also reduce computational complexity. Based on the obtained feature subset, three prediction models including multiple linear regression, support vector regression and artificial neural network are trained and used to realize accurate taxi time prediction. To investigate the performance of the proposed prediction methods, historical flight data from an international airport is collected to test their performance. Experimental results indicate that feature selection technique has the potential to enhance the taxi time prediction ability and save computing resources during the prediction process.

With the rapid development of China's economy, the industrial structure of industry is undergoing tremendous changes. There are many idle old industrial buildings. In the field of its transformation planning, LOFT is being used more and more widely. This paper mainly studies the LOFT mode and the overview of the old building space, the influencing factors of the old building space transformation, and the LOFT mode transformation of the old building space.

This paper introduces a case study on the failure mechanism and support design of a roadway tunnel in the fault fracture zone of the 106 mining area in the Yuandian no.2 coal mine. Based on the on-site geological conditions (in-situ stress test, borehole television imaging, and lithological analysis), the failure mechanism of the roadway tunnel in the fault fracture zone was studied. The test results showed that the high tectonic stress, fractured rock, and poor lithology are the primary reasons for the roadway instability. According to the support principles of grouting reinforcement, pre-reinforced support, and rational support range, a new type of combined support technology was proposed, including advanced grouting, grouting bolts, and grouting anchor cables. A 100 m roadway section was selected for field testing using the new support scheme, and detailed deformation monitoring was performed. Monitoring results showed that the roadway deformation under the new support was significantly reduced. During the roadway excavation process, no roof collapse phenomenon occurred, and the safety of roadway excavation was ensured. This successful case provides an important reference for similar roadway projects in the fault fracture zone.

Mining-induced fractures in underground coal mining face affect the stability of overburdens and provide preferential channels for water and material transfer in the underground environment. Therefore, to study the development of water-flowing fracture zones in overburdens of working face and goaf is of great significance for roof control, gas drainage, water resistance, disaster reduction, and efficient mining from the mining. In this study, a new method for predicting the development of overburden water-flowing fracture zone height (DHOWFFZ) was proposed based on the characteristics of overburden rock in No. 3 coal seam of Xin’an Coal Mine. First, the stope of No. 3 coal seam exhibits a rock stratum structure of mudstone and sandstone overlapping. Considering this characteristic, the overburden strata of No. 3 coal seam are divided into several “mudstone-sandstone” rock stratum groups. Furthermore, the ultimate tensile deformation of soft rock is greater than that of hard rock. It is proposed to judge the development degree of penetrating fracture in each rock stratum by adopting the elongation rate of mudstone intermediate layer. Meanwhile, the DHOWFFZ of “mudstone sandstone” composite rock stratum structure in the 3402 working face of No. 3 coal seam is calculated to be smaller than 43.1 m according to the actual situation. Finally, the DHOWFFZ in the 3402 working face was measured in the field, which verifies the rationality of the new DHOWFFZ prediction method. The research results provide new ideas for the prediction of DHOWFFZ and are helpful for future research in related fields.

In coal mines, under high in situ stress and strong mining activity, roadway surrounding rock commonly contains large amounts of larger fractures and microfractures. Along with the large deformation and continuous rheology of the soft rock roadway, the fractures in the surrounding rock are likely to be compressed and closed, forming undeveloped microfractures, which hinder conventional grouting support methods. Based on the fluid-solid coupling between slurry seepage and microfracture deformation, a theoretical model of microfracture grouting seepage is established. A program for the analysis and calculation of microfracture grouting is developed to quantitatively describe the variation in slurry seepage distance and fracture opening. Numerical experiments are carried out to study the grouting seepage of microfractures under different grouting pressures and fracture opening conditions, and the variation rules for the spatial distribution of fracture opening and slurry seepage distance during grouting pressure are obtained. Fluid-solid coupling has a significant influence on grout seepage characteristics. The grouting pressure and the fracture opening changes are nonlinearly attenuated along the grout seepage direction.

In grouting support projects, due to the small concealment of micro-fractures, the support effect often fails to meet design requirements. The percolation effect is a common factor that causes grouting failure, and the influence of grouting pressure on the percolation effect is very obvious. In this article, a design of a micro-fracture grouting experimental system is presented that can realize high-pressure grouting and then uses a variety of ultrafine cements to carry out high- and low-pressure grouting tests under different fracture opening conditions, thereby obtaining the grouting pressure and accumulated grouting weight during the grouting process. The results show that a combination of the grouting pressure curve and the cumulative grouting weight curve can determine whether the ultrafine cement will have a percolation effect. Increasing the grouting pressure can reduce the critical fracture opening value and also reduce the occurrence of the percolation effect. The research results provide a theoretical basis for the high-pressure grouting of micro-fracture rock masses and offer certain guiding significance for the design of high-pressure grouting support schemes.

Accurate calculation for the critical support pressure of tunnels plays an important role in tunnel stability evaluation and support design. In this study, a mechanical model for circular tunnels is developed. Considering the intermediate principal stress and strain‐softening characteristic of rock mass, the critical support pressure when the plastic zone and damage zone begin to occur is determined based on the unified strength criterion and strain‐softening model. Through the example study, the critical support pressure under different intermediate principal stress coefficient is solved. Furthermore, the effect of initial field stress, softening coefficient, and maximum damage variable on the critical support pressure are also discussed. The results show that the critical support pressure and radii of plastic and damage zones all decrease with the increase of the intermediate principal stress coefficient. The larger the initial field stress, the larger the critical support pressure. The softening coefficient and maximum damage variable of rock mass has no influence on the critical support pressure when the plastic zone begins to form, but has a significant effect on the critical support pressure when the damage zone begins to form. As softening coefficient increases and maximum damage variable decreases, the critical support pressure when the damage zone which begins to form increases. Data presented in this contribution provide significant theoretical insights into evaluating tunnel stability and support system reliability.