풍화토 지반에서 전력구 쉴드 TBM 터널 굴착에 따른 침하 거동의 확률론적 평가

초록

Urban power cable tunnels constructed using shield TBM methods are often located beneath roadways and near buried utilities, where excavation-induced ground settlement may cause significant social and economic risks. Weathered soil exhibits high spatial variability and uncertainty in mechanical properties, making deterministic evaluations based on mean values insufficient to represent settlement risks. To address this, we probabilistically evaluated ground surface and tunnel crown settlement induced by shield TBM excavation in weathered soil using Monte Carlo simulation and three-dimensional finite difference analysis under different cover depths (20, 30, and 40 m). The results show that surface settlement decreases with increasing cover depth, and the exceedance probability of settlement also decreases. The exceedance probabilities for cover depths of 20, 30, and 40 m were estimated as 9%, 3%, and 1%, respectively, while the corresponding reliability indices increased to 1.34, 1.88, and 2.33. In contrast, crown settlement showed an opposite trend, where both mean settlement and the probability of exceeding the allowable limit increased with increasing cover depth. The failure probabilities were estimated as 2%, 8%, and 25%, and the corresponding reliability indices decreased to 2.05, 1.41, and 0.67. By presenting settlement responses as probability distributions and risk levels rather than a single deterministic value, this study complements limitations of conventional deterministic approaches and proposes a quantitative risk assessment framework based on exceedance probability and reliability index for shield TBM tunnels in weathered soil.

키워드