Dynamic Risk Assessment of Ultra-Shallow-Buried and Large-Span Double-Arch Tunnel Construction

Abstract

Ultra-shallow-buried and large-span double-arch tunnels face complex risks during construction. The risk sources are hidden, complicated, and diverse. The dynamic risk assessment problem cannot be solved satisfactorily by using the static method as an insufficient amount of research has been conducted. The land part of the Xiamen Haicang double-arch tunnel was selected as the background for the dynamic risk assessment of ultra-shallow-buried and large-span double-arch tunnel construction. The construction process was divided into five stages: pre-construction preparation; ground and surrounding rock reinforcement; pilot tunnel excavation; and the single-and the double-tunnel excavations of the main tunnel. Through consultation with tunnel experts, six first-level and thirty second-level risk evaluation indexes were proposed. The benchmark weight of the dynamic risk assessment index was determined by using the analytic hierarchy process. The weight of the risk evaluation index was revised according to the monitoring data and the construction stage. The fuzzy evaluation matrix of the construction risk membership degree was obtained by using the fuzzy comprehensive assessment method, and the calculation results were analyzed using the subsection assignment method. Control measures were suggested according to the risk assessment results. The risk assessment result of the double tunnel excavation stage of the main tunnel was level II, and the risk level was the highest among the five construction stages. The risk assessment result of the ground and surrounding rock reinforcement stage was level IV, and the risk level was the lowest. The dynamic construction safety risk assessment based on the fuzzy comprehensive assessment method is more timely, accurate, and reasonable than the traditional assessment method. The method can be adopted in similar engineering projects.

Using Fuzzy Comprehensive Evaluation to Assess the Competency of Full-Time Water Conservancy Emergency Rescue Teams

“…In the judgment matrix, the most common method is to use 1-9 and the reciprocal for comparison [34]. The degree of importance increases with the increase in number.…”

“…The specific rules are shown in Table A6 [51] (see the Appendix A), and the judgment matrix is shown in Table A7 (see the Appendix A). The consistency ratio (CR) is often used to test the consistency of the judgment matrix [34,53]. If CR < 0.1, the consistency is acceptable [52].…”

“…Ruan et al [32] used fuzzy comprehensive evaluation to calculate subjective indicator scores, and AHP to estimate weight distribution, in the process of establishing a comprehensive assessment indicator system for the containment rescue measures of the national nuclear emergency engineering rescue team. The combination of these two methods [33] makes the results more accurate, because a single assessment method often cannot obtain accurate assessment results [34]. It also makes the system stronger and can better solve fuzzy and unquantifiable problems.…”

Construction practice of water conveyance tunnel among complex geotechnical conditions: a case study

“…Drilling holes to carry out blasting excavation, blasting surrounding rocks with explosives, which caused large-scale disturbance and damage of surrounding rocks, is widely used in metamorphic rocks and igneous rocks 13 . At the same time, with the continuous improvement of blasting technology and level, the blasting range is controlled by adjusting the number of explosives, and drilling and blasting construction technology is also well used in soft rocks or hard soils 14 . Full-face tunnel boring machine (TBM) have been proposed by several researchers as a method of tunnel excavation 15 .…”