Experimental Study on Deformation Behavior of Shield Tunnel Subjected to Riverbed Scour Based on DOFS

Xuanyi Lu,Kun Feng,Meilin Qi,Wenqi Guo 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.4

Exploring the deformation behavior of shield tunnels is significant to design and safety assessment for shield tunnel structures. This paper carries out a reduced scale model test of shield tunnel subjected to riverbed scour for the first time. A new loading device system is designed to simulate the initial stress field of stratum and effect of riverbed scour. Distributed optical fiber sensing (DOFS) technology is adopted as measuring method to achieve the surrounding soil deformation and structural deformation, ovality, and radius of curvature of shield tunnel. The test results show that uneven rebound deformation of stratum and shield tunnel structure occurs in both transverse and longitudinal directions under the action of riverbed scour. Variations in ovality differences exist along the longitudinal direction of the shield tunnel, indicating that the transverse and longitudinal deformation of the shield tunnel affects each other. The radius of curvature of the longitudinal deformation of the shield tunnel at the vault is much smaller than that of the bottom. The results demonstrate the broad application value of DOFS technology in shield tunnel structure monitoring and reveal the deformation mechanism of shield tunnels subjected to riverbed scour, which can provide important reference values for the structure design and safety monitoring of shield tunnels.

Settlement behaviours and control measures of twin-tube curved buildings-crossing shield tunnel

Jianwei Jia,Ruiqi Gao,Defeng Wang,Jianjun Li,Ziwen Song,Jinghui Tan 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.5

Settlement control techniques are critical for the safety of shield tunnel constructions, especially for facing complex situations. In this study, the shield tunnel structure from Huaita east road station to Heping Road station in Xuzhou metro No.3 line (China) is taken as engineering background, which has various complex problems of the upper-soft and lower-hard composite stratum conditions, twin curve shield tunnels, and underpass the foundation of the piled raft. The deformation characteristics of shield tunnelling passing through buildings are explored. Subsequently, comprehensive research methods of numerical simulation and field measurement are adopted to analyzing the effectiveness of settlement control by using the top grouting technique. The results show that the settlement of the buildings has obvious spatial characteristics, and the hysteresis effect can be obviously observed in soil deformation caused by shield construction. Meanwhile, the two shield constructions can cause repeated disturbances, reducing the soil deformation's hysteresis effect. Moreover, the shield tunnel's differential settlement is too large when a single line passes through, and the shield construction of the outer curve can cause more significant disturbance in the tunnel than the inside curve. Notably, the proposed process control parameters and secondary topgrouting method can effectively control the deformation of the shield tunnel, especially for the long-term deformation.

터널굴착 시뮬레이션을 위한 터널굴착장비의 개발에 대한 연구

김상환 사단법인 한국터널지하공간학회 2003 한국터널지하공간학회논문집 Vol.5 No.2

Tunnel modelling in the field of geotechnical engineering essentially requires models of tunnelling machines and the simulation of tunnelling processes to clarify the detailed behaviour of tunnel construction. Modern advanced mechatronics, including construction processes, machinining and control technologies, are making it possible to fabricate such models. These technologies, however, are essentially developed in a gravity field condition and are needed to examine in a 1g or cenrifuge field condition. This paper presents the simulation method for tunnelling processes and the design method for tunnelling machines with special reference to the problem of earth pressure acting on the lining of a shield tunnel. The paper then introduces and verifies the design method for tunnelling machines in the 1g field by means of checking the reproduceability of experiment data and their comparison with data in the field. 지반공학적인 측면에서의 터널에 대한 모델링작업은 실질적인 터널공사시 야기되는 상세거동을 재현할수 있는 터널장비의 개발로 터널굴진과정을 실질적으로 묘사하는데 있다고 볼수 있다. 최신기계정보활용기술은 즉 시공과정 및 기계제어기술등을 실험실에서 재현할 수 있도록 하였다. 그러나, 이러한 기술 등은 중력장상태에서 사용되도록 개발되어지고, 1g 또는 원심장 (Centrifuge Field)상태의 실험에서 주로 활용되고 있다. 이에 따라 본 논문은 터널링과정에 대한 씨뮬레이션기법과 실험실에서 활용되는 쉴드터널장비의 설계기법 및 개발에 대한 연구 결과를 수록하였다. 또한 개발된 장비의 정밀성과 신뢰성을 반복적인 실험을 통하여 검증하고, 개발된 장비를 이용하여 얻은 결과와 실질적인 현장자료와 비교분석하였다.

Study on the applicability of load calculation method for large-diameter shield tunnel in argillaceous sandstone stratum under high water pressure

Yinjun Tan,Qianshen Wang 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.12

Surrounding rock pressure is an important factor to be considered during designing tunnel structures. In this research, the on-site surrounding rock pressure of a large diameter shield tunnel in argillaceous sandstone stratum was tested, and the evolution process of surrounding rock pressure was analyzed, based on which the variation law of surrounding rock pressure with buried depth and span of the tunnel was discussed. Combined with the numerical simulation method, the applicability of the load calculation method for the large-diameter shield tunnel in the argillaceous sandstone stratum was studied. The results showed that the variation of surrounding rock pressure generally changed from a rapid and substantial increase to a slight decrease and finally tended to be stable. Before reaching stability, the deformation pressure was dominant; then, the loosening pressure became the main pressure, and the surrounding rock pressure almost reached the maximum value in the synchronous grouting stage. Moreover, it was also found that the shield construction had a great influence on the surrounding rock pressure of the 15-ring segments behind the working face. While calculating the surrounding rock pressure, the tunnel section shape, buried depth and surrounding rock conditions should be fully considered. The Full Soil Column Theory, Terzaghi’s Theory, Xie’s Theory and Bierbauman’s Theory were more suitable for tunnels with a buried depth of less than 2.5 hp. When the buried depth of the tunnel exceeded 2.5 hp, the calculation results needed to be enlarged by 2 ~ 3 times if the Statistical Method or Protodyakonov’s Theory was used for calculation. Xie’s Theory can be used to calculate the surrounding rock pressure of shallowly buried argillaceous sandstone stratum large-diameter shield tunnel. For a deeply buried argillaceous sandstone stratum large-diameter shield tunnel, it is recommended to use Numerical Simulation Method.

Shield 및 TBM 터널의 유지관리계측 관리기준 설정에 관한 연구

우종태 한국재난정보학회 2024 한국재난정보학회 논문집 Vol.20 No.1

Purpose: The objective of this study was to improve the tunnel maintenance and monitoring technology by establishing the maintenance, management, and monitoring standards for shield and TBM tunnels, which had been applied more in recent years. Methods: This study comprehensively analyzed and compared the data and model simulations of Seoul Subway Lines 7 and 9 and Bundang Line, shield and TBM tunnels in South Korea, tunnels in France and Japan, and Channel Tunnel in the UK. Results: This study set maintenance and monitoring standards when there was no design estimate based on numerical analyses such as section design and section analysis regarding the maintenance and monitoring section of shield and TBM tunnels. Conclusions: It is necessary to determine safety by comprehensively considering not only each monitoring item but also the changing trend and correlation of all items and compensation of the tunnel.

다양한 지반 및 지진하중 조건을 고려한 해저철도 터널의 동적 수치모델 분석

곽창원,박정준,유민택 사단법인 한국터널지하공간학회 2023 한국터널지하공간학회논문집 Vol.25 No.6

Recently, the advancement of mechanical tunnel boring machine (TBM) technology and the characteristics of subsea railway tunnels subjected to hydrostatic pressure have led to the widespread application of shield TBM methods in the design and construction of subsea railway tunnels. Subsea railway tunnels are exposed in a constant pore water pressure and are influenced by the amplification of seismic waves during earthquake. In particular, seismic loads acting on subsea railway tunnels under various ground conditions such as soft ground, soft soil-rock composite ground, and fractured zones can cause significant changes in tunnel displacement and stress, thereby affecting tunnel safety. Additionally, the dynamic response of the ground and tunnel varies based on seismic load parameters such as frequency characteristics, seismic waveform, and peak acceleration, adding complexity to the behavior of the ground-tunnel structure system. In this study, a finite difference method is employed to model the entire ground-tunnel structure system, considering hydrostatic pressure, for the investigation of dynamic behavior of subsea railway tunnel during earthquake. Since the key factors influencing the dynamic behavior during seismic events are ground conditions and seismic waves, six analysis cases are established based on virtual ground conditions: Case-1 with weathered soil, Case-2 with hard rock, Case-3 with a composite ground of soil and hard rock in the tunnel longitudinal direction, Case-4 with the tunnel passing through a narrow fault zone, Case-5 with a composite ground of soft soil and hard rock in the tunnel longitudinal direction, and Case-6 with the tunnel passing through a wide fractured zone. As a result, horizontal displacements due to earthquakes tend to increase with an increase in ground stiffness, however, the displacements tend to be restrained due to the confining effects of the ground and the rigid shield segments. On the contrary, peak compressive stress of segment significantly increases with weaker ground stiffness and the effects of displacement restrain contribute the increase of peak compressive stress of segment.

In-site Experiments on the Swelling Characteristics of a Shield Tunnel in Expansive Clay: A Case Study

Jianxiu Wang,Jiaxing Liu,Xiaotian Liu,Yunhua Jiang,Xuezeng Liu 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.3

Expansive soil swells, softens, and disintegrates when absorbing water, whereas it shrinks when losing water. Understanding the swelling characteristics of a shield tunnel in expansive soil is important. However, most in-site experiences on the swelling characteristics of a tunnel are obtained from the NATM tunnels constructed in swelling rock using drill and blast method; most laboratory experiments or theoretical analyses on the swelling characteristics of a shield tunnel in expansive soil are under certain hypotheses which have not been verified in actual situation. To solve the problems, the Slender West Lake tunnel was selected as the background, laboratory and in-site experiments were performed to understand the swelling characteristics of a shield tunnel in expansive clay. Four experimental sections were constructed in the actual tunnel. The measuring gauges were pre-installed in the segments in factory and the segments were installed in-site to observe the actual earth pressure and temperature during construction. The influences of expansive soil to the distributions and variations of earth pressure, bending moment, and temperature were analyzed. The increasing earth pressure was divided into three stages. Large earth pressure was detected at the top, bottom, left, and right sides of the tunnel. The earth pressure at the left and right sides was larger than that at the top and bottom. Large negative bending moment was detected at the top and bottom of the tunnel, whereas large positive bending moment was detected at the left and right sides of the tunnel. The minimum bending moment appeared at 45° oblique. The largest negative bending moment was larger than the largest positive bending moment. Based on the observations, a load mode of swelling pressure for a beam-spring model was suggested. It can be referred by the similar tunnels.

An Artificial Freezing Technique to Facilitate Shield Tail Brush Replacement under High Pore-Water Pressure Using Liquid Nitrogen

Ping Yang,Jiling Zhao,Lin Li 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.4

During tunnelling, with the progression of the shield tunnelling machine, the shield tail brush, which is an important accessory required to seal the shield tail and prevent the tunnel from ground water or grouting fluid discharging, will gradually be worn-out/damaged and inevitably lead to safety problems. As a result, problematic tail brush needs to be replaced to prevent more serious problems from happening before any further tunnelling. The replacement of this shield tail brush can be very risky, especially when the shield tunnelling machine is located at a soil layer under high pore-water pressure. This study introduces an engineering practice to facilitate the shield tail brush replacement under high pore-water pressure through the development of a frozen soil wall with the help of an artificial freezing technique using liquid nitrogen. A case study is adopted to demonstrate the implementation of this technique. For the specific site condition, a numerical simulation is usually performed first to determine the design parameters (e.g., liquid nitrogen temperature, length and spacing of the freezing pipes) required for artificial freezing process. Several holes along the radial direction of the tunnel were then made to monitor the temperature of the soil around the tunnel. Subsequently, the artificial freezing process was performed according to the design. The replacement of the tail brush was initiated when the frozen soil wall developed during freezing met the requirements for tail brush replacement. The artificial freezing technique using liquid nitrogen proved to be a reliable and time-effective option to facilitate the tail brush replacement under high pore-water pressure.

Experimental Study on the Longitudinal Mechanical Behavior of Shield Tunnel in Soft-Hard Uneven Strata and the Reinforcement Effect of Longitudinal Channel Steel

Tingjin Liu,Shuyi Zhang,Yongfeng Tang,Zhenwei Ye 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.1

This paper investigates the longitudinal behavior and failure pattern of shield tunnel, as well as the reinforcement mechanism of longitudinal channel steel, using reduced-scale tunnel models assembled with 24 lining rings. The longitudinal behavior of the shield tunnel and the reinforcement effect are discussed in terms of vertical deformation, joint deformation, and concrete cracking. The results indicate that the shield tunnel without reinforcement longitudinallydeforms in a “bending and dislocation” mode, with the failure pattern dominated by bending deformation. In contrast, the failure pattern of the shield tunnel reinforced by channel steels is characterized by brittle shearing dislocation fracture of the circumferential joint. The load at which damage occurs in the reinforced tunnel model is 1.74 times and 2.04 times that of the non-reinforced staggered and straight jointed tunnels. The reinforcement reduces the horizontal convergence discrepancy of lining rings above the soft foundation spring and the adjacent lining rings, which improves the overall integrity of the tunnel structure.

터널식 공동구 최적단면 설계기술 개발: 해외 표준단면 사례 및 설계기준 분석

박광준,윤경렬 사단법인 한국터널지하공간학회 2018 한국터널지하공간학회논문집 Vol.20 No.6

Since the domestic utility tunnels were built mainly in the development project of the new city, they are all in the form of cut-and-cover box tunnel. But, in the case of overseas construction of utility tunnels for existing urban areas, the bored tunnel types are mainly adopted. It is reasonable to install bored tunnels in a downtown area because it is difficult to block the roads or install bypass roads due to heavy traffic and civil complaints. In order to activate the utility tunnels in bored type, it is necessary to secure optimized cross-sectional design technology considering the optimal supplying capacity and mutual influencing factors (Thermal Interference, electrolytic corrosion, efficiency of the maintenance, etc.) of utilities (power cables, telecommunication cables, water pipes, etc.). The optimal cross-section design method for bored utility tunnels is ultimately to derive the optimal arrangement technique for the utilities. In order to develop the design methods, firstly, the cases of tunnel cross-section (Shield TBM, Conventional Tunneling) in overseas shall be investigated to analyze the characteristics of the installation of utilities in the section and installation of auxiliary facilities, It is necessary to sort out and analyze the criteria related to the inner cross-section design (arrangement) presented in the standards and guidelines. 국내 공동구는 주로 신도시 개발사업에 포함되어 건설되었기 때문에 모두 개착 BOX 형태를 이루고 있으나 기존 시가지를 대상으로 독자적 공동구를 건설 중인 해외의 경우 터널식 공동구 형태를 주로 채택하고 있다. 공동구의 사회적 요구가큰 중심가 도심지는 교통량이 많아 장기적으로 차로를 차단하거나 우회 차로 설치가 곤란한 것이 일반적이므로 터널식공동구 설치가 합리적이라 하겠다. 이러한 터널식 공동구 활성화를 위해 공동구 최적 설계용량 및 수용시설(전력, 통신, 상수도 등)별 상호 영향인자(열간섭 및 전식, 유지관리 효율성 등)를 고려한 최적화된 단면설계 기술력을 확보할 필요가있다. 터널식 공동구의 최적단면 설계기술이란 결국 공동구내 수용시설의 최적 배치기법을 도출하는 것이라 할 수 있다. 이러한 설계기법 도출을 위해 우선적으로 해외의 터널식 공동구(Shield TBM, Conventional Tunneling) 내공단면 적용사례를 조사하여, 단면 내 수용시설의 배치현황, 부대시설 설치 등의 특징을 분석하고, 또한 국내 ․ 외의 공동구 설계기준및 지침서에서 제시하고 있는 내공단면 설계(배치)와 관련한 기준사항들을 정리 ․ 분석할 필요가 있다.