The construction of underground project can be seriously affected due to the uncertainty and ambiguity of geological conditions. However

the geological risk factors are not given a thorough consideration in the risk assessment methods

while the weight is determined subjectively. In this paper

six first-level geological risk assessment indicators: soil mechanical properties

rock mass properties

inrush conditions

groundwater

karst

and regional stability are selected. Each of first-level indicators is characterized by several secondary-level evaluation indicators. Then a more comprehensive and reasonable geological risk evaluation index system is established by integrating and applying existing evaluation methods of single geological risk evaluation indicators to determine the risk level of the first-level evaluation indicators. In view of the diversity of the indicators and the incompatibility of the assessment result given by a single indicator

a geological risk assessment model is established based on the extension method. The simple correlation function in extension theory is used to calculate the weight of each indicator

which is more objective and reasonable than traditional methods. The model was adopted to evaluate the risk of a station in Guangzhou. It is found that the geological risk level division is reasonable

and can reflect the local geological risk situation objectively; the geological risk level of the station in untreated condition is “moderate risk”

and the eigenvalues of risk grade is 1.94

which indicates that “moderate risk” is biased toward the “low risk” level. The assessment result agrees with the site investigation

so the evaluation result is precise.