Abstract: Objectives: Adverse geological risks in tunnel construction are characterized by progressive exposure, dispersed information, and dynamic updating. Existing methods mainly focus on the identification and assessment of individual risks, but lack the ability to organize and represent multi-source engineering information in an integrated and associative manner, making it difficult to meet the comprehensive requirements of on-site treatment. Methods: To address this issue, an auxiliary decision-making method for the treatment of adverse geological risks in tunnel construction based on a Hierarchical Risk Knowledge Tree (HRKT) is proposed. First, a large language model is employed to extract risk-related information from multi-source engineering texts, forming risk knowledge units that include risk types, geological conditions, construction context, treatment measures, as well as spatial chainage and construction time. Second, considering the type differences, contextual similarities, and hierarchical relationships among risk instances, the HRKT is constructed to achieve the hierarchical organization of dispersed risk information. Finally, for specific treatment-oriented queries, evidence chain reasoning based on the knowledge tree is conducted to generate treatment conclusions corresponding to the current risk scenario and their supporting evidence. Results: Case analyses show that the HRKT can organize and trace corresponding evidence at different hierarchical levels according to varying query requirements. Furthermore, based on 300 typical query samples from a section of an extra-long tunnel, the HRKT achieves an element coverage rate of 0.934, an effective unit rate of 0.940, and a hierarchical matching rate of 0.913, outperforming the baseline methods. Conclusions: The results indicate that the HRKT can effectively organize and represent multi-source adverse geological risk information, enhance the capability of evidence integration for treatment-oriented queries, and improve the interpretability and traceability of treatment conclusions, thereby providing auxiliary support for the treatment of adverse geological risks during tunnel construction.