주입 데이터 분할과 상측 단측 허용한계를 이용한 터널 강관보강 그라우팅 주입량 임계치 산정

초록

This study aims to establish an injection volume threshold (Q*) for grouted steel pipe reinforcement in tunnels, where quantitative management criteria for injection volume have not yet been clearly defined, by applying data partitioning together with an upper one-sided tolerance limit. Based on this threshold, the necessity of additional reinforcement in high-injection sections and the resulting improvement in stability were examined from the perspective of ground treatment extent. Using field data from a tunnel section where steel pipe reinforcement grouting—as an auxiliary tunnelling method—was applied, this study reviewed injection volume management criteria intended to prevent face loosening and collapse during excavation and to secure overall tunnel stability. Injectability was evaluated using flowmeter-based time (T)–pressure (P)–flow rate (Q) data, and section-to-section variation in injection volume was interpreted as reflecting differences in rock quality and joint development. Macroscopic injection volume patterns were first identified from the acquired T-P-Q data, after which the injection data were reorganized at 1 m intervals to obtain detailed locational information on sections exhibiting highinjection tendencies. An iterative search algorithm for data partitioning was then applied to the reorganized data to identify the normal injection population, and an upper one-sided tolerance limit was applied to that population to derive the injection volume threshold (Q*). The threshold (Q*) was defined as a statistical upper-bound management criterion for distinguishing high-injection sections from typical injection behavior. In addition, excessive groundwater inflow of up to 1,300 tonf/day occurred within the study section, which was evaluated as an anomalous case directly related to face stability. Accordingly, this study compared the spatial distribution of injection volume with face observation records to examine the potential spatial correspondence between high-injection sections and weak ground locations, and also confirmed the correspondence with excessive groundwater inflow and poor face conditions. Furthermore, the ground in high-injection sections identified by the threshold (Q*) was assumed to consist of weathered soil, and numerical analyses were performed using the surrounding ground treatment thickness as a variable to evaluate the improvement in stability associated with an expanded reinforcement extent. The results confirmed that, rather than directly determining the actual treatment area, the injection volume threshold (Q*) can serve to identify potential high-injection and weak ground sections, thereby contributing to a proactive response for subsequent tunnel faces.

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