近年來，無支撐擋土系統已逐漸成為開挖工程中另一種的選擇，相對於支撐擋土系統，它具有無可比擬的優勢。本文著重研究新穎一樓樓版先行無支撐擋土系統以及無支撐開挖系統在TPKE案例中的實際應用情況。TPKE案例是一個無支撐開挖的成功應用案例。此案例開挖深度為13.2 m，範圍約為 127 m × 105 m，屬於大範圍開挖工程。在設計過程中，考慮到節約成本和縮短工期，採用連續壁、扶壁、地中壁和環樑版的配置，進而設計出無支撐開挖擋土系統。此系統經三維有限元分析驗證是可行的。最終TPKE案例成功完成開挖，最大連續壁壁體變形與開挖深度比為0.25%，且分析結果與監測數據結果相吻合。然而，無支撐開挖系統的壁體變形呈現懸臂式位移，最大壁體變形位於壁體頂端，且壁體變形會有過大的疑慮。因此，本文提出另一種創新的無支撐擋土系統，即一樓樓版先行無支撐擋土系統。此系統由三個主要結構組成: 地中壁與扶壁組合的U壁、連續壁及地上一樓樓版。其最大的優點為可充分利用地上一樓樓版並取代鋼構工作台，且有效抑制連續壁頂端的壁體變形，適合於都市開挖。此外，在U壁間加入扶壁有助於降低開挖面上方的壁體變形，然而對於開挖面下方的壁體變形影響相對較小。此結果在假設案例和TPKE案例應用中均得到驗證。因此，在設計一樓樓版先行的無支撐擋土系統時，應將U壁間距作為主要考量因素，建議先確定合適的間距，再加入一道扶壁以有效改善壁體變形。

In recent years, the strut-free excavation retaining system has gradually become an alternative option in excavation engineering. This method offers distinct advantages compared to the traditional supported retaining wall system. This paper studies an innovative strut-free excavation retaining system with first-floor slabs and a strut-free excavation retaining system implemented in the TPKE project. TPKE project is a successful design of a strut-free excavation retaining system. The TPKE excavation project was 13.2 m deep, covering approximately 127 m × 105 m, considered an extensive excavation. Considering the cost savings and construction period shortening, the configurations of the diaphragm walls, buttress walls, cross walls, and the capping slab were used to design a strut-free excavation retaining system. This is feasible through the three-dimensional finite element analysis. This project was completed with the maximum diaphragm wall deflection to the excavation depth ratio of 0.25%. However, the wall deflection in the strut-free excavation system presents a cantilever-type displacement, with the maximum wall deflection occurring at the top of the wall, and there is a concern that the wall deformation might be excessive. Therefore, this paper introduces an innovative strut-free excavation system, namely a strut-free excavation retaining system with first-floor slabs. This system consists of three main components: U-Shaped walls, formed by the combination of cross walls and buttress walls, diaphragm walls, and the first-floor slab above ground. The significant advantage of this system is that it fully exploits the first-floor slab in place of a steel work platform and effectively controls the deformation of the top of the diaphragm wall, making this system suitable for urban excavation. Moreover, introducing buttress walls between the U-Shaped walls helps to reduce the wall deformation above the excavation face. In contrast, the impact on the wall deformation of the wall below the excavation face is relatively minor. This result has been validated in both the hypothetical and TPKE project. Therefore, the spacing between the U-Shaped walls should be a primary consideration when designing a strut-free excavation system with first-floor slabs. Determining an appropriate spacing first is recommended, then introducing a buttress wall to improve wall deformation effectively.

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