Advances in Transportation Geotechnics IV

Table of Contents

1. Frontmatter

2. Tunnels

   1. Frontmatter

   2. Investigation on the Dynamic Response of a High-Speed Railway Tunnel Located Beneath an Airport Runway and Uneven Settlement of the Runway

      Feizhi Xiao, Jizhong Yang, Yao Shan

      Abstract

      The rapid development of the high-speed railways and air transportation networks is leading to an increasing demand of the combination of these two modes of transport. Some modern integrated transport hubs have been operated, and at least 32 airports in China are planning to combine air transportation with high-speed railway transportation. To realize the “seamless transfer” between the airport and the high-speed railway station, some high-speed railways were constructed beneath airport runways. It is necessary to study the dynamic interaction between these two kinds of infrastructures. Based on a project with a high-speed railway tunnel beneath an airport pavement in south China, an aircraft–runway interaction model and a vehicle-tunnel-foundation coupling model are proposed to investigate the dynamic response of the complete system. In this paper, the cumulative plastic deformation of the airport runway caused by the dynamic load of high-speed trains is comprehensively predicated. The influence of the aircraft dynamic load on the deformation of the tunnel and the operation safety of high-speed trains is investigated. The results show that the settlement of airport runway rises to 9.80 mm after ten years of operation of the high-speed railway. The amplitudes of the vertical and horizontal displacement of the tunnel affected by the aircraft dynamic load are 0.192 mm and 0.099 mm, respectively. The rate of wheel load reduction of the high-speed train is not evidently excited by the aircraft dynamic load.

   3. Influence of Shield Slurry Property on Filter Cake Quality in Sand Stratum

      Weitao Ye, Longlong Fu, Shunhua Zhou

      Abstract

      Slurry preparation and pressure maintenance of slurry balance shield should be carefully treated during tunneling in complex sand stratum. On basis of the slurry shield tunnel project in Fuzhou, slurry pressure was determined by two different theoretical methods. Then, an indoor test was conducted to explore the influence of constituents on slurry property. The influence of slurry properties on filter cake forming process under different slurry pressure was also analyzed through slurry penetration test. The test results indicate that the bentonite and silt soil had dominated influence on relative density, while the bentonite and CMC had dominated influence on viscosity. It is found that the water discharge, which is the index to evaluate the effect of filter cake, decreases firstly and then increases as slurry relative density increases. The water discharge also decreases as slurry viscosity increases. Meanwhile, the influence of viscosity on the water discharge was found less than that of relative density. Finally, a segmented slurry control scheme suitable for sand stratum in Fuzhou was presented.

   4. Dynamic Response and Long-Term Settlement of Four Overlapping Tunnels Subject to Train Load

      Xiangliang Zhou, Quanmei Gong, Zhiyao Tian, Yao Shan

      Abstract

      With continued development of urban rail transit networks, the quantity of overlapping metro tunnels is increasing. Long-term service performance of the tunnel structure can be threatened a lot by complicated dynamic response of tunnel–ground system under train load, especially in the overlapping cases. Based on a case of four overlapping tunnels in soft clay region, dynamic response of the tunnel–ground system and long-term settlement of the tunnels are investigated with finite element method (FEM) and empirical method. It is shown that, maximum acceleration and dynamic principal stress of the lining in overlapping zone are 48.2% and 19.8%, respectively, larger than that in non-overlapping zone. The ten-year accumulation settlement of the tunnel in overlapping zone is 173.7% larger than that in non-overlapping zone. Uneven settlement occurs in the overlapping zone, and the radius of curvature of the tunnel (12,461 m) exceeds the requirements of the specification (15,000 m). Grouted reinforcement can control the uneven settlement well. Radius of curvature of the tunnel can be refined to 33,967 m, which meets the requirements of the specification.

   5. Dynamic Stability of Soft Soil Between Closely and Obliquely Overlapped Metro Tunnels Subjected to Moving Train Loads

      Hui Li, Quanmei Gong, Honggui Di, Weitao Ye, Zhi Liu

      Abstract

      The problem in dynamic stability of soft soil between closely and obliquely overlapped metro tunnels during operation will aggravate cumulative settlements which affects the safety of metro systems. Based on Shenzhen Metro Line 5 and Line 11 overlapped tunnels, a three-dimensional vehicle-track-tunnel-soil model has been established. Meanwhile, the dynamic shear strain and its transfer characteristics of the soft soil layers between overlapped tunnels under moving train loads has been studied. In longitudinal direction, the most unfavorable position for the soft soil is located in the place where the maximum overlapped degree exists between two tunnels. In transverse direction, the dynamic shear strain in soft soil between tunnels diffuses obliquely at a certain angle from the arch waist of tunnel and gradually decreases with the increase of distance. It also increases nonlinearly with the number of operating lines. Besides, the dynamic stability of soft soil was evaluated by the cyclic threshold shear strain parameters of Vucetic and the value exceeds the linear cyclic threshold shear strain. The plastic deformation of soft soil under moving train loads will accumulate obviously and the dynamic stability problem cannot be ignored. Therefore, high-pressure jet grouting pile is adopted to reinforce the soft soil between two tunnels. And the result shows that the dynamic shear strain of soft soil after reinforcement is much smaller than that before.

   6. Research on Calculating Quantity of Utility Tunnel with Revit Secondary Development

      Qi Zhang, Qian Su, Yan Yan

      Abstract

      A practical cost estimation about the design model of the utility tunnel is essential for the management of the utility tunnel in the design stage. However, the process for quantity calculation based on the design model from the utility tunnel is inefficient because of the inaccurate recognition. Issues in quantity calculation will be resolved with the method related to Revit secondary development (RSD) proposed in the paper. On the basis of Application Programming Interface (API), programming language C#, and programming platform Visual Studio, we established a tight correspondence between the design model of utility tunnel and the external database for quantity calculation. Consequently, results of the quantity calculation based on utility tunnel depended on the clarified model of utility tunnel were available. A case of utility tunnel in the new southern district of Nanjing was studied. It has shown that the results of RSD are better than that of the existing third-party calculation software, in terms of recognition accuracy and data integrity. The results of the study verified the reliability of method proposed in the paper.

   7. The Influence of Variation in Groundwater Table on Ground Vibrations from Underground Tunnels

      Chao He, Shunhua Zhou, Honggui Di, Xiaohui Zhang

      Abstract

      This paper investigates the influence of the variation in the groundwater table on ground vibrations from underground tunnels by an analytical model. The saturated porous medium is used to model the soil layer under the groundwater table, and the dry single-phase medium is applied to simulate the soil above the groundwater table. The transfer matrix method and wave transformation are applied to derive the solution for a tunnel in a dry/saturated layered half-space. Ground vibrations from a tunnel in a three-layered half-space are computed by using the proposed model. The numerical results demonstrate that the vibration levels increase as the groundwater table drops. The displacement field is similar to that of a saturated half-space when the groundwater table is above the tunnel, while it is similar to that of a dry single-phase half-space as the groundwater table is under the tunnel.

   8. Experimental Studies on Three Types of Vibration Isolators for Buildings Near Subways

      Tao Sheng, Xue-cheng Bian, Wei-xing Shi, Jia-zeng Shan, Gan-bin Liu

      Abstract

      This paper presents three types of vibration isolators to enhance the comfort for residents inside buildings near subways. Stacked sandbags formed the first type of isolator. An elastic and closed capsule filled with sand and rubber particles is the second type of isolator. The third type of isolator is laminated thick rubber bearing with a sliding bottom. The materials and components of the three isolators are described first. Then, the vertical stiffness values, the damping ratios, and the ultimate bearing capacities of the above isolators are tested in a laboratory, and the suppression effectiveness for subway-induced vertical vibrations are investigated by two full-scale buildings near subway transportation. The results indicated that the bearing capacity of the first isolator is the lowest, but the damping ratio is the highest. For the second isolator, the vertical stiffness and damping ratio can be adjusted by changing the mixture ratio of sand particles, and the bearing capacity is improved significantly. For the third isolator, the damping ratio is the smallest, but the sliding bottom is capable of isolating earthquake ground motions. After installation of the three isolators, the human comfort inside the buildings satisfied the limit values, proving that they are effective as base isolation methods for buildings near subways.

   9. Dynamic Response of Floating Slab Track with Variation on Failure Position of Steel Spring

      Xiaolin Song, Linfeng Xue, Fangzheng Xu, Jianping Wei

      Abstract

      The steel spring floating slab track is widely adopted for its remarkable performance on vibration isolation. With the increase of the operation time of floating slab track, the damage or failure of the steel spring is inevitable, which will have a bad effect on the track dynamics and vibration-mitigating effects. The steel spring’s forces were calculated by the vertical coupled dynamics model for the metro and the floating slab track. The dynamic response of tunnel and soil subjected to the steel spring’s forces was analyzed. The influence of steel spring failure position of floating slab track on the dynamic response of infrastructure was investigated. The results showed that the failure position had a significant effect on the dynamic characteristics. Although the infrastructure displacement varies little with the failure position, the reaction forces of the steel springs and acceleration of the track, the tunnel, and the soil notably increased when the steel spring failed at the end of the track. The tunnel acceleration with one pair of damaged springs at the end of track is 40% greater than that with the same failure springs in the middle of track.

   10. The Effect of Boundary Permeability on the Dynamic Response of the Layered Saturated Ground Subjected to an Underground Moving Load

       Yijun Li, Anfeng Hu, Kanghe Xie, Rong-tang Zhang

       Abstract

       In this paper, the effect of boundary permeability on the dynamic response of a layered poroelastic half-space under moving loads in a tunnel is studied analytically. The tunnel is modeled by an Euler–Bernoulli beam located between two horizontal layers. The Biot’s dynamic equations for the poroelastic soil medium are solved by utilizing the Helmholtz decomposition and Fourier transformation. Combining the boundary conditions and the continuity conditions between each layer, the explicit analytical solutions for the dynamic response of each layer in the transformed domain are obtained by the transmission and reflection matrices (TRM) method. The solutions in time–space domain are expressed in terms of infinite Fourier-type integrals, which are evaluated by an adaptive version of extended integral trapezoidal formula. The validity and accuracy of the proposed methodology and numerical integration scheme are confirmed by comparison with some existing results. Two different boundary permeabilities are considered, and the numerical results show that the influence of the boundary permeability on the dynamic response is related to the permeability of the soil and the moving load speed.

   11. The Effect of Excavation Unloading on the Deformation of Existing Underlying Shield Tunnel

       Min-yun Hu, Jing-tian Yang, Li-dong Pan, Kong-shu Peng, Yu-ke Lu

       Abstract

       Deformation measurements from 17 real cases of excavation spanning subway tunnels in soft soil were collected for examining the deformation reaction of the tunnels due to the above unloading. The investigation showed that (1) tunnel may be uplifted owing to the above excavation; (2) the deformation of the tunnel section due to above unloading exhibits vertical elongation and horizontal shortening, and the transversal shape of the tunnel changes from approximate circle to vertical ellipse; (3) the main influential factors include the excavation unloading ratio (N), the excavation area (A), and the excavation shape coefficient (α). It indicates that, with the increase of excavation depth and the increase of unloading ratio (N) of foundation pit, the rebound of tunnels may increase, and the higher the width of the excavation, the larger the range of vertical uplift that will be induced around the tunnel. For 12 out of the 17 examined cases, the vertical uplift measurements of the tunnels are smaller than the alarmed value of 10 mm, indicating that the maximum displacement of the tunnel can be controlled by purposed engineering measures, such as pre-reinforcement of the soil around the tunnel, installation of the anti-pulling piles around tunnel, and stacking around the bottom of the excavation. 2-D FEM modelling was also carried out to study the effect of excavation characters and the effectiveness of the control procedures. The combination procedure of soil improvement by cement mixing and anti-pulling pile installation is verified to be effective to reduce the adverse impact from above excavation on tunnels.