Environmental Risk Assessment of Subway Station Construction to Achieve Sustainability Using the Intuitionistic Fuzzy Analytic Hierarchy Process and Set Pair Analysis

Table 3

Index system and interpretation of environmental risk assessment for metro stations.

Indicator	No.	Indicator interpretation
Harsh hydrological conditions	E1	Metro stations are usually constructed underground and are substantially affected by hydrological conditions. When the groundwater table is high, measures are required to deal with water inflow, which increases the structural requirements and prolongs the construction period. After lowering the groundwater level, uneven settlement of the surrounding buildings may occur, and the main structure of the station may experience “floating.” Harsh hydrological conditions also adversely affect the stability of the foundation pit support.
Adverse geological conditions	E2	Adverse geological conditions will increase the difficulty of subway station excavation, increase the cost, and prolong the construction period. The worse the geological environment, the more complex the foundation pit support has to be, and the worse the stability is. The supporting structure may not adapt adequately to adverse geological conditions, resulting in geological disasters, such as landslides.
Adverse geomorphological conditions	E3	Adverse geomorphic conditions may cause landslides, waterlogging, and other natural disasters. If the stability of the deep foundation pit of the station project is poor, additional measures are required during project construction, affecting the project cost and the construction period.
Frequency of natural disasters	E4	Typhoons, earthquakes, tsunamis, landslides, mudslides, and other natural disasters may have a devastating impact on the subway station project, and people, materials, and equipment at the construction site may be damaged.
Frequency of severe weather	E5	Low or high temperatures, heavy snow, strong wind (blowing sand), heavy rainfall, and other severe weather does not only reduce the safety of construction workers but also causes accidents and adversely affects the construction cost and construction period.
Density of underground pipelines	E6	Underground pipeline protection is an important aspect of subway station construction. The denser the underground pipelines are, the more difficult the construction is, and the more likely it is that the construction period and cost are affected. Underground pipelines are often municipal pipelines. Once damaged, people, materials, and equipment at the construction site may be seriously damaged, and the daily life of residents may be affected.
Density of surrounding buildings	E7	The greater the density of buildings around the station, the greater the difficulty of construction is, and the more likely it is that the construction period and cost will be affected. The greater the density of the buildings around the foundation pit, the more complex the supporting structure of the foundation pit has to be, and the worse the stability is.