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Shield tunnels will inevitably pass through viaduct piles at a close distance due to the extensive construction of subways and viaducts in the city. In order to understand the influence of shield tunneling on the deformation of existing pile foundation and grouting protection measures, based on an engineering case, Changsha Metro Line 5 (from South...
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... Zhang et al. 11 proved the feasibility of a pile foundation underpinning construction scheme when a shield tunnel passes through existing piles, studied the comprehensive influence of shield tunnelling and the old pile cutting process on underpinning piles 12 , and proposed a pile foundation underpinning technology for an oblique tunnel crossing a pile group foundation 13 . Wang and Zhao [14][15][16][17] proposed a series of strata reinforcement measures to significantly improve the deformation of existing structures and proposed a new grouting material for the pre-reinforcement of shield tunnels adjacent to existing pile foundations 18 . Wu 19 and Wang 14 www.nature.com/scientificreports/ ...
In the construction of tunnels under existing stations, it is necessary to control their settlement. When there is a pile foundation in the existing station, the pile cutting has a significant impact on the settlement of the existing station. To determine the influence of existing piles on the settlement of subway stations, a reasonable pile-cutting time is proposed. Based on the Chengdu Metro Line 9 underpassing the existing Line 1 hatchery station, the settlement law of the tunnel underpassing the existing Line 1 station is analysed via a numerical simulation. Furthermore, the deformation and stress characteristics of the existing piles, pipe roofs, and tunnel linings and the supporting effect on the existing station are discussed. It is concluded that the cutting of existing piles causes a change in the tunnel bearing system, thus resulting in a certain deformation of the station. The influence of different pile cutting times on the settlement of the existing station is then analysed, and it is clarified that the tunnel support stiffness is significantly enhanced after the construction of the secondary lining. At this time, the settlement of the existing pile station is significantly reduced. Finally, through a field investigation, the effect of surface grouting, pipe shed, and multilayer lining on the settlement control of the existing station while the existing pile foundation exists is determined. This research can provide a reference for the settlement control and foundation underpinning of existing stations at ultra-small distances in underground excavation tunnels.
... To enrich the research on protective measures for bridge pile foundations, Xu et al. [16] proposed comprehensive reinforcement measures combining grouting, isolation piles, and steel cross-bracing, significantly optimizing the displacement and internal forces of piles under the impact of shield construction. Many scholars have relied on specific engineering cases, employing three-dimensional numerical simulation combined with field monitoring, to study the impact and deformation control measures of shield tunnel crossing pile foundations, proposing and optimizing reinforcement technologies such as sleeve valve pipe grouting, isolation pile protection, and pile foundation replacement [17,18,19,20,21,22]. Furthermore, Shan et al. [23] established an analytical model and a three-dimensional finiteinfinite element model of the bridge-foundation-tunnel system, further optimizing the parameters of isolation piles from the perspective of vibration isolation, effectively controlling the deformation of the surface and existing pile foundations. ...
By relying on the foundation engineering of pile foundations for the Chengdu Metro Line 27 shield tunneling through interchange bridges, three-dimensional numerical simulation results are used to verify field measurements. This study investigates the horizontal displacement, vertical displacement, and stress characteristics of the pile foundation during shield tunneling considering the coupling effect of seepage stress. Additionally, protective measures and reinforcement effects for pile foundations near the tunnel are discussed. Results show that the deformation caused by shield tunneling in gravel strata mainly affects piles within 10 ring widths before and after the piles. During right-side excavation, the bending moment of the pile body exhibits an inverted “S” distribution, while during left-side excavation, it is symmetrically distributed, with the maximum bending moment and axial force occurring at the same buried depth as the tunnel crown. Vertical displacement of the pile body is divided by the horizontal position at the top of the tunnel, with upper pile settlement and lower pile uplift, reaching maximum at the pile top. Horizontal displacement of the pile body shows an “arch” distribution, with stress concentration near the tunnel, indicating an overall trend of the pile foundation moving away from the tunnel. Based on the mechanical response of the pile foundation, control measures such as ground pregrouting with sleeve valve pipes and semicircular grouting inside the tunnel are proposed. Optimized reinforcement parameters are obtained through three-dimensional numerical simulation, resulting in an 80% reduction in horizontal displacement, an 80.5% reduction in vertical displacement, a 70% reduction in pile axial force, and a 67% reduction in pile bending moment under the optimal reinforcement conditions. The research provides important theoretical basis for revealing the impact laws of shield tunneling through pile foundations in gravel strata and for controlling bridge pile deformation.
... As a road material, asphalt mixture presents a three-phase structure which consists of asphalt binder, mineral aggregate and air void, which has been widely used in transportation infrastructure, such as bridges and tunnels, and so on [1][2][3][4]. Among these components, the asphalt binder that contains many organic hydrocarbon compounds is easily susceptible to being aged when suffering thermal, oxygen and ultraviolet radiation influences [5,6]. ...
... The twin-tunnel is usually excavated in a sequential way. Tunnel spacing, rest period, and excavation sequence have a significant influence on the ground deformation (Addenbrooke and Potts 2001;Do et al. 2014;Huang et al. 2021b;Suwansawat and Einstein 2007;Zheng et al. 2020). For instance, the ground settlement trough caused by the second two closely spaced tunnels was markedly asymmetrical (Cooper et al. 2002). ...
During tunneling in urban areas, ground deformation may cause damage to surface and sub-surface structures and buildings, especially the shallow-buried twin-tunnel. In the present study, a 3D numerical simulation and field measurements are adopted to study the ground deformation and stress characteristics of the segment of Guangzhou Metro Line 18. Two measures are adopted to reduce the ground deformation, i.e., grouting from the middle shield and compressed air assistance. The results indicate that the ground surface does not have a settlement as the TBM passes, but an upheaval as the two measures are adopted properly. The maximum upheaval values of the advance tunnel and second tunnel are approximately 45 mm and 5 mm, respectively. As the buried depth of the tunnel increases, the ground upheaval decreases gradually. When the advance tunnel is excavated, soils adjacent to the tunnel have an outward horizontal displacements. The maximum horizontal displacement is approximately 40 mm at the turning of the tunnel. As the tunnel is excavated along straight line, the maximum horizontal displacement is approximately 20 mm. The second tunnel excavated has similar effect on the soils, rendering a slight squeezing effect on the advance tunnel. The maximum horizontal displacement of soils between the two tunnels is approximately 25 mm. While the squeezing effect has a slight effect on the deformation and force distribution of the segments of the advance tunnel. The grouting from middle shield and compressed air assistance can well control the ground deformation of the shallow-buried twin-tunnel with small spacing.
... Mountains and hills account for about half of the total land area. With the construction of a large number of infrastructures, landslide geologic hazards are becoming increasingly serious (Huang 2007;Huang et al. 2021;Li et al. 2022a, b, c;Tu et al. 2023;Zhang et al. 2015;Qin et al. 2022a, b;Wang et al. 2023;Sun et al. 2023). The reservoir bank landslide has both the commonness of general mountain landslide and the particularity of being affected by the reservoir. ...
Although there have been a lot of studies on landslides in geologic hazards in China, the study on tuff landslides in southeast coastal areas is relatively lack. In view of this, based on the landslide of Xiageliao Mountain in Jinshui Village, Zhenbu Township, Qingtian County, by using automatic monitoring technology and analyzing the monitoring data of landslide deformation and rainfall, the deformation law and influencing factors of tuff landslide are discussed, which provides a basis for landslide stability analysis and landslide geologic hazards warning. The results show that: (1) tuff belongs to volcanic ash composition, with physical properties such as unstable mineral composition, high porosity and permeability, and easy fracture of thin layers, resulting in its strength and stability varying with water content. (2) The sliding deformation is mainly concentrated in the parts below the “primary and secondary platforms” (Zone I); The deformation of parts above “Level 1 and Level 2 platforms” (Zone II) is relatively small; There is basically no deformation in the trailing edge crack area (Zone III). (3) The overall annual movement speed of Xiageliao landslide is 10–15 cm/a. Affected by continuous rainfall or heavy rainstorm, the deformation curves of division I and II show a stepped evolution feature, that is, obvious growth occurs first, then gradually returns to stability, and the overall deformation is slow. (4) The total deformation amount is positively correlated with the sum of rainfall 15 days before the initiation of accelerated deformation and during accelerated deformation; the duration of deformation is positively correlated with the rainfall 10 days before the accelerated deformation stops.
... In recent years, most studies mainly focus on the effects of shield tunneling on existing pile foundation [1,2,[9][10][11][12][13][14], and report related to cutting the RC piles by shield is few. Based on the construction of Suzhou metro in China, field test of shield cutting RC piles was carried out, wear and damage of the modified rippers were studied by Li et al. [7]. ...
Based on the TBM tunnel of Red Line of Tel Aviv in Israel, this paper carried out laboratory tests of shield cutting concrete and reinforced concrete piles and investigated cutting performance of cutter, failure model of rebars, length of damaged rebars, and cutter vibration. The results indicate that under the condition of low tunneling speed and rotating speed, vibration of the cutterhead is small, and vibration of the center cutterhead is more obvious in the radial direction of the cutterhead. Cross sections of broken rebars mainly consist of shear section, tensile-shear section, tensile-compressive section, and bending section. Considering the tunnel status, it is recommended to adopt excavation speed of 3∼5 mm/min, and rotating speed of 1.0∼1.3 r/min. While cutting RC piles, the principle of “low excavation speed, high rotating speed, and less disturbance” is recommended. Cutting with disc cutters is efficient and the torque of which is stable but the length of the rebars got from cutting varies a lot. It is recommended that majorities of the cutters shall be disc cutters and supplemented with drag bits and tear cutters.
... A large number of subways are being built in urban area to reduce traffic congestion and to promote urban development. Tunnel excavation can induce changes in stress and displacements of rocks and soil (Barzegari et al., 2014;Huang et al., 2021aHuang et al., , 2021b, which may result in large displacements of both the ground and nearby buildings, especially in shallow buried tunnels (Fig. 1). The full-face shield tunnel boring machine (TBM) has been extensively used to construct underground projects in urban areas. ...
The full-face shield tunnel boring machine (TBM) has been widely used to build tunnels in urban area. Ground deformations usually occur during tunnelling processes, which is closely related to engineering geological property. A large ground deformation may lead to large-scale surface settlement or ground collapse, especially for shallow buried tunnels. In general, synchronous grouting is adopted to reduce the ground deformation. The temporal and spatial distribution of the grout pressure and consolidation processes of grouting have a significant influence on the deformation. For a better understanding the relationship between the grout material type and the ground deformation, the present study models a complex numerical model in FLAC3D based on the Guangzhou Metro line 18. A numerical method is proposed to reproduce the tunnelling process and the consolidation process of grout material. The effect of grouting material on ground deformation is discussed, i.e., immediately solidified type, quick hardening type, and good mobility type. The ground deformation of the numerical simulation are compared to those monitored in the field. The results indicate that the immediately solidified type grout can reduce the ground settlement effectively and is mainly applicable to secondary grouting. The quick hardening type can make the ground upheaval, which is smaller than that induced by immediately solidified type. The good mobility type can reduce the ground settlement and well control the ground deformation. The good mobility type recommends using in the numerical study for simulating the synchronous grouting.
... Tunnelling-induced ground surface settlement, inclination, and discontinuous displacement could affect or even damage adjacent superstructures. The isolation pile between the existing pile and the tunnel is widely proven as an efficient protective measure for controlling the displacement of building's pile foundation induced by shield tunnelling [6][7][8][9]. ...
Isolation piles are widely used to control the influence of shield tunnelling on adjacent buildings as an effective protective measure. However, the restraint effect of isolation pile on surface settlement trough is rarely explored from the internal mechanism. Firstly, the restraint mechanism of isolation piles is investigated from the pile-soil-tunnel interaction mechanism. Secondly, based on the Melan solution and the Loganathan formula, the analytical solution of surface settlement trough under the influence of adjacent isolation piles is derived. Thirdly, in order to satisfy the engineering analysis scale and reflect the friction characteristics between isolation pile and soil particles simultaneously, the FDM-DEM coupling technique is introduced to establish a numerical model including discrete medium and continuum medium. Finally, the applicability and reliability of the analytical solution and the FDM-DEM coupling numerical solution are verified by comparing field measured data. The results indicate that the surface settlement trough under the influence of isolation piles will have an asymmetric distribution. Surface settlement tends to develop more to the opposite side of the tunnel when isolation piles are pre-installed on one side. The findings of the study have substantial theoretical significance and engineering reference value.
With the acceleration of tunnel construction, it is inevitable to cross the collapsible loess region. The engineering properties of loess are very poor in the water-rich environment. Additionally, if the buried depth is shallow, the load bearing capacity is further weakened, which can increase the difficulty of tunnel construction. Therefore, this paper provides a case study on the Pangwan Tunnel based on a geological survey, numerical simulation, and on-site monitoring. The failure characteristics of the studied area under the original support scheme are analyzed in detail, and the extreme deformation mechanism is discussed combining the geological conditions and surrounding rock properties. The results show that there are five main reasons resulting in the extreme deformation of the Pangwan Tunnel, which are: abundant groundwater, low strength of surrounding rock, disintegration of loess after water immersion, depth of tunnel is shallow, and unreasonable original support scheme with low bearing capacity. Then, the corresponding countermeasures are proposed, which are advance drainage, large arch foot and foot-lock bolt, sealing tunnel face and grouting timely, as well as advance pipe shed and small pipe grouting. Finally, from the feedbacks of numerical analysis and field application results, extreme deformation of the Pangwan Tunnel is effectively controlled. This work can provide some helpful guidance for similar projects.
