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This study surveyed the response of diaphragm walls with a length of 51 m during a large basement excavation (approximately 9310 m2, depth of 30.2 m) in soft soil in Hangzhou, China. The field data of wall deflections, maximum wall deflection rate, stress development of diaphragm walls, axial force of struts, and measured horizontal earth pressures were extensively investigated. The following conclusions were drawn: deep excavation can produce greater stress unloading compared with shallow excavation, which results in the diaphragm walls producing more significant deflection; the load transfer to the struts caused by the excavation is completed within two to three weeks after strut casting; the deeper basement excavation only has a minor effect on the distant axial forces of the struts; the horizontal earth pressure behind the diaphragm wall is linearly distributed along the depth. This paper proposes a general earth pressure AEP envelope based on the investigated case and similar cases. [ABSTRACT FROM AUTHOR]

Building damage induced by the excavation conducted for the three-storey basement of the Kerry Center – a modernised business centre comprising large-scale departmental stores, business offices, apartments and a hotel in Hangzhou, China – was investigated. A method for estimating the building damage level considering the spatial effects of soil deformation around the excavation was also developed. The excavation site is in the Hangzhou urban centre, near to which stands an ancient building known as the Red House. Settlement, horizontal displacement and cracks on the Red House were studied to estimate the actual damage level. Surface settlements around several excavations were analysed to obtain a surface profile along the excavation. The results showed that the profile could be simplified to a parabolic model. A damage criterion based on the average state of strain in the distorted portion of the structure was derived considering the spatial effects of soil deformation. Different damage criteria, including tensile stress, cracks, distortion and horizontal strain, were used to evaluate the damage level of the Red House. The result obtained from the damage criterion presented in this paper agrees well with the actual building damage level. This criterion formed the basis of the preliminary analysis conducted prior to finite-element modelling. [ABSTRACT FROM AUTHOR]

Purpose: Deep excavation in soft clay often causes additional deformations to surroundings. Then, if deformations cannot be predicted reasonably, the adjacent buildings may be threatened by the deep excavation. Based on the good field observations from ten deep excavations in Hangzhou, this paper aims to thoroughly investigate the characteristics of wall deflections and ground settlements induced by deep excavations. Design/methodology/approach: On the basis of good field observation of ten deep excavations, the performances of excavations, supported by contiguous pile in Hangzhou, were studied, and also compared with other case histories. Findings: The maximum wall deflections (dhm) rang mostly from 0.7 to 1.2 per cent He, where He is the final excavation depth, larger than those in Taipei and Shanghai. The observed maximum ground settlement in the Hangzhou cases generally ranges from 0.2 to 0.8 per cent He. Then, the settlement influence zone extends to a distance of 2.0-4.0 He from the excavation. The relatively large movements and influence zones in Hangzhou may be attributed to low stability numbers, large excavation widths and the creep effect. The excavation width is justified to have a significant influence on the wall deflection. Therefore, to establish a semi-empirical formula for predicting the maximum wall deflection, it is necessary to include the factor of excavation width. Originality/value: The relevant literature concentrated on the characteristics of deep excavations supported by the contiguous pile wall in Hangzhou soft clay can rarely be found. Based on the ten deep excavations with good field observation in Hangzhou, the characteristics of wall deflection and ground settlements were comprehensively studied for the first time, which can provide some theoretical support for similar projects. [ABSTRACT FROM AUTHOR]

• Developed a hydraulic loading system to carry out a full-scale loading test. • The asymmetric unloading load of the three-ring segment is realized. • The influence of initial confining pressure loading method is considered. • The influence of foundation pit excavation on tunnel structure is explored. To explore the internal force and deformation response law of the Hangzhou subway shield segment under the influence of the excavation and unloading of the side foundation pit, the self-developed "shield segment hydraulic loading system" was used to carry out full-scale loading tests on the three-ring staggered assembled segments. A preloading loading test were performed before the formal experiment to determine the loading method of the initial confining pressure. Analyzed the change mechanism of the internal force and deformation of the segment structure are influenced by factors such as the foundation pit and the tunnel clear distance. A numerical model is established based on the experimental results, and the influencing parameters that are difficult to complete in the experiment, such as the depth of the tunnel, are analyzed in detail. The research results show that the equal load maintains a balanced state of the segment to the greatest extent, and its internal force and deformation results are large, which is suitable for this experiment. After the excavation of the foundation pit, the maximum positive and negative bending moment increases, while the maximum axial force decreases. The average maximum recovery rate of tunnel section is 15.6%. Moreover, the additional internal force and deformation of the segment will increase with increasing deformation parameters of the envelope structure and decrease with increasing clear distance between the foundation pit and the tunnel. The bending moment of the segment is more sensitive to changes in the confining pressure, the convergence change can be controlled within a limited range, and the trend of the change in the internal force of the bolt shows differences. The numerical model established in this paper can better analyze the stress state of the tunnel. When the tunnel is buried deep in the slightly upper position of the excavation surface of the foundation pit, the unloading effect that is received is largest. [ABSTRACT FROM AUTHOR]

The project of Hangzhou Metro Line 1 is the first metro line of the urban rapid rail transit system in Hangzhou, China, which is one of the largest municipal projects of Hangzhou and is being constructed commencing from March 28, 2007 and expected to be completed by October 1, 2012. This metro line has a total length of 48 km and 34 stations, connecting Hangzhou downtown with the suburban area of the city. Owing to the complex geological condition, harsh construction situation, and immature computational methodology, construction of metro systems is often subjected to considerable sources of uncertainties. To ensure the safety of the adjacent building structures, it is a vital necessity to monitor deep excavations of metro tunnels at their inconstruction stage. This paper introduces the instrumentation system for settlement monitoring of a metro-tunnel airshaft of the project of Hangzhou Metro Line 1 during the construction of deep excavation. The long-term settlement data monitored by the measurement markers installed at the surface ground and in the depth direction of the airshaft excavation construction site are analyzed and presented in detail. The obtained results indicate that the settlements at the instrumented locations of the construction site during different construction steps vary steadily in an allowable variation range. [ABSTRACT FROM AUTHOR]

In recent years, China has been undergoing a metro railway construction boom in order to alleviate the urban traffic congestion problem resulting from the rapid urbanization and population growth in many metropolises. In the construction of metro systems, deep excavations and continuous dewatering for construction of the metro tunnels and stations remain a challenging and high risk task in densely populated urban areas. Intelligent computational methods and techniques have exhibited the exceptional talent in dealing with the complicated problems inherent in the deep excavation and dewatering practice. In this paper, an intelligent risk assessment system for deep excavation dewatering is developed and has been applied in the project of HangzhouMetro Line 1 which is the first metro line of the urban rapid rail transit system in Hangzhou, China. The specific characteristics and great challenges in deep excavation dewatering of the metro-tunnel airshaft of Hangzhou Metro Line 1 are addressed. A novel design method based on the coupled three-dimensional flow theory for dewatering of the deep excavation is introduced. The modularly designed system for excavation dewatering risk assessment is described, and the field observations in dewatering risk assessment of the airshaft excavation of Hangzhou Metro Line 1 are also presented. [ABSTRACT FROM AUTHOR]