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Due to the compact space and high utilization demands, the construction of large underground subway transfer station in urban area, like Pengcheng Square station in Xuzhou, China, was confronted with various obstacles, such as nearby surface and subsurface structures, heavy road traffic, and clay-rock mixed ground conditions. Based on careful investigations to all surrounding limitations, an innovative composite station form and its corresponding construction method, open cutting with underground excavation (OCUE) method, were introduced. The construction performance of this method has been confirmed by field monitoring. The main findings from the research include: (1) Sophisticated design and construction is essential for satisfying the expected functions of the station, minimizing the influence on the heavy traffic and sensitive structures in adjacent, as well as tackling the adversities of the clay-rock mixed strata; (2) Supported by the OCUE method, composite form of subway station was delicately designed to maximize the utilization of limited space, it comprised of open cutting part, underground excavation part and half-covered excavation part; (3) The implementation of OCUE method was successful with little influence on the surrounding traffic and buildings. Experiences obtained from this project can provide effective reference for similar cases.

Deep sedimentary deposits of soft clays are widely distributed in coastal areas as well as many interior major cities in China. In order to study the stratum adaptability of earth pressure balance (EPB) shield machine tunneling in such types of soft ground, model tests of tunneling excavation, using the running tunnel of the Shanghai Metro Line M8 as a background, are carried out with different over burden ratios, opening rates of cutter head, driving speeds and rotation speeds of screw conveyor. Based on the test results, the interrelationships between chamber pressure and mucking efficiency, mucking rate and driving speed, thrust force and torque are obtained. The influences of tunnel depth, opening rate of cutter head and driving speed on thrust force and torque are revealed. Such findings can not only facilitate establishing relationships between shield working parameters and soil properties, but also serve as a guide for the design and construction of shield tunnel in soft ground.

This paper examines the response of metro stations adjacent to an excavation via a series of comprehensive finite element parametric studies. The effects of several key factors (e.g., the distance, D, between the existing metro station and the deep excavation, the depth of the excavation, He) governing the performance of the metro station were quantified. On the basis of the numerical analysis results, some major findings were obtained: (1) rotation of rail closer to the excavation transformed from the clockwise direction to the anticlockwise direction with the increasing of D / He; (2) as D / He increased, internal structural forces of juncture at roof slab and right wall decreased gradually and excessive internal structural force occurred when D / He was smaller than 0.7; and (3) conventional protection criteria of metro stations were not rational because they did not take into account the internal structural forces.

Close monitoring of ground settlement during TBM construction plays an important role in controlling construction quality and risk. But how to identify and allocate the tunneling defects implied in large volumes of monitoring data and develop their relations to specific TBM driving parameters, and in what way to convey this information rapidly to the site at first time during tunneling process remains a big problem to constructors, owners and project managers of tunnels. Ground surface settlement, used directly for evaluation of environmental impacts, can be analyzed in depth and imported into the evaluation of TBM driving parameters. Ground surface settlement patterns are established for explicit interpretation of field measured data. By matching them with corresponding mechanical procedures of TBM driving, the tunneling defects or bias can be found out and then the driving parameters can be optimized. Moreover, in reality, large volumes, discrepancy and discreteness of measured data demand sufficient experienced experts and qualified staff onsite to process the data in time. So a method and a procedure for settlement curve pattern-recognition based on fuzzy mathematics is established for automatic data processing on site, to achieve quick responses to risks indicated by the variation of field measured data.

The purpose of this paper is to research the different influence on the subway station pit in construction, caused by the adjacent pit excavated before and after the station pit. The construction environment is divided into three types: a) no pits around the station; b) the pit around the station is constructed before it; c) the pit around the station will be constructed after it. By 3-D finite element numerical simulation, the displacement of the soil between station and adjacent pit is researched, as well as the internal force of the support of station pit. They are the maximal for case a, the minimal for case c. The influence coverage of the adjacent pit construction is less than the excavation depth. The results can be served as a guide for the design and construction of adjacent pits.

Based on the expected subway tunnel project in Qingdao, bolt-grouting support parameters are optimized by the principle of orthogonal design and ANSYS numerical simulation calculation. The best support program is obtained: the length of bolt is 2.8m; the row & line space of bolt is 0.8×0.8m; the grout divergence radius is 1.5m. The effect extent of the different parameters to the support result is the length of bolt < the grout divergence radius< the row & line space of bolt. The research results serve as a guide for the design of bolt-grouting support for soft-rock subway tunnel.

The consolidation and pressure dissipation of the generally adopted cement based grout injected into the tail void during simultaneous backfill grouting in shield tunneling are influenced by many factors, such as grout characteristics, ground permeability, pore water pressure (PWP), dimension of the initial grout pressure, and various loads acted on the lining. Based on the typical simultaneous backfill grouting parameters in soft soils in Shanghai, and excluding the influence of grout hardening, using the theory of fluid mechanics and elastic mechanics, the principle of grout consolidation in tail void is firstly analyzed in this paper, and the changes of grout cake's thickness (GCT) and grout pressure (GP) with time are clarified. Then, as for grout pressure dissipation (GPD), the influences from ground osmotic resistance, PWP and dimension of the initial GP are discussed. The following conclusions are drawn: the ground osmotic resistance can obviously delay grout consolidation, but not the final consolidation state; the increment of soil shear modulus can accelerate the grout pressure dissipation speed (GPDS); consolidation process can be obviously restrained by the increment of PWP; and there is a positive relationship between the initial GPDS and the dimension of GP.

This paper investigated the effectiveness of open-trench wave barriers in reducing the movements of sheet pile walls during deep dynamic compaction (DDC), by isolating (screening) the energy waves generated in DDC impact. This investigation was achieved by a series of finite element analyses. The open trenches with different cross-section shapes were investigated. The dimensional effects of trenches were analyzed and discussed, and then the isolation efficiencies of the different trenches were compared. The numerical results indicated that excavating an open trench in front of the retaining walls is an effective measure to reduce wall movements during DDC. For the investigated open trenches, increasing trench depth or trench width can efficiently improve their isolation efficiencies, while the cross-section shapes of the trenches have no apparent influences.