## 1 Introduction  
In recent years, many countries have not been sufficiently attentive to environmental protection due to their pursuit of economic development as it rapidly advances. Consequently, the emission of \"greenhouse gases\" has become an environmental problem that must be urgently resolved. Moreover, \"carbon neutrality\" has become a popular topic of discussion worldwide. Because of the severe impact of automobile exhaust on the environment, governments have urged people to travel using low-carbon transportation, thus promoting the rapid development of subways. Air travel has the advantages of speed and efficiency, and the number of travelers preferring this mode of transportation to save time and cost has continued to increase. Presently, most cities have initiated projects linking subways and airports to optimize urban transportation planning further. Accordingly, a form of travel that links transportation modes has been created, directly enabling the transfer of passengers to a corresponding flight without leaving the station. For example, the internal cargo lane of Beijing Capital International Airport crosses airport taxiway L, a shield tunnel under the runway of Taipei Songshan Airport. The underground service lane of Guangdong Zhuhai Airport crosses the apron; two railroad tunnels of Chengdu Metro Line 10 are under the apron and taxiway at Shuangliu Airport. In the UK, two railroad tunnels are under the taxiway and station apron of Heathrow Airport [1; 2; 3; 4; 5]. A subway tunnel crossing an airport runway is a large-scale project. To resolve the problems of high cost, time consumption, and resource consumption associated with this type of project, scholars generally employ numerical simulation in research. Aircraft load has a strong impact and can cause considerable damage. In view of the foregoing, the means for applying aircraft load to finite element numerical models has become a significant problem that requires solving. Research results are synthesized and summarized in the following three ways according to aircraft load application: (1) When the carload is simplified, pavement design is approximated as an elliptical ground area. In China, however, the current specification and engineering design mainly uses a circle for simplicity, and the aircraft load is typically simulated using this method in the preliminary study [6; 7; 8; 9; 10]. (2) The domestic \"Specification for Airport Cement Concrete Pavement Design\" (MHT5004-2010) prescribes the shape of a single wheel print of the main landing gear of the aircraft. According to this specification, the wheel print area is equated to a rectangle based on the principle of area equivalence and then converted to a nodal force or uniform load. This approach is employed by most scholars because it has been developed based on specifications [11; 12; 13]. (3) The aircraft load is simplified to a concentrated force that propagates to the bottom plate of the pavement at a 45\({}^{\circ}\) concrete punching tangent angle; thus, a load-spreading area is formed [14]. After solving the problem of aircraft load application through numerical simulations, the research of most scholars focuses on several areas, such as parking lots, airport runways, aircraft carriers, dynamization, and mechanization of system equipment subjected to pressure waves [15; 16; 17]. Such studies are implemented to analyze the airport runway material, dynamic response, and stability under aircraft load [18; 19; 20; 21]. In addition, because airport construction starts late, although investigations on the dynamic response of the space under airport runways subjected to aircraft loads have been conducted, the number of these studies are limited compared with those performed on airport pavement structures. For example, [PERSON] et al., (2018) [14] attributed aircraft loads to nodal and surface dynamic loads according to the finite element method.