Deformation characteristics of a 38 m deep excavation in soft clay

2011 ◽  
Vol 48 (12) ◽  
pp. 1817-1828 ◽  
Author(s):  
Guo B. Liu ◽  
Rebecca J. Jiang ◽  
Charles W.W. Ng ◽  
Y. Hong
Keyword(s):  
Soft Clay ◽  
Field Performance ◽  
Lateral Wall ◽  
Diaphragm Wall ◽  
Deep Excavation ◽  
Wall Panel ◽  
Soft Clays ◽  
Measured Ratio ◽  
Increasing Demand ◽  
Ground Settlements

To meet the increasing demand for underground space for economical development and infrastructural needs, more and more deep excavations have been constructed in Shanghai. In this paper, field performance of a 38 m deep multistrutted excavation in Shanghai soft clay is reported. The deep excavation was retained by a 65 m deep diaphragm wall. Inclinometers as well as settlement and heave markers were installed to monitor the performance of the deep excavation. This project provides an unusual opportunity to study the differential heaves of center columns and diaphragm walls during excavation. Because of the significant stress relief resulting from the 38 m deep excavation, maximum heaves of the center column and diaphragm wall panel were about 30 and 16 mm, respectively. The measured ratio δp/H (heave/final excavation depth) of column is less than 0.1% whereas the observed δp/H of the diaphragm wall panel is about 0.04%. The maximum distortion between the column and the diaphragm wall panel is smaller than 1/500, which is within the limit range proposed by Bjerrum in 1963. Owing to careful construction control, stiff strutting system, and compaction grouting, the measured lateral wall deflections and ground settlements at this site are generally smaller than other shallower excavations in soft clays in Shanghai, Singapore, and Taipei.

Field Performance of a Deep Multi-Strutted Excavation in Hangzhou Soft Clays

2011 ◽  
Vol 243-249 ◽  
pp. 2324-2327
Author(s):  
Hong Wei Ying ◽  
Yong Wen Yang ◽  
Xin Yu Xie
Keyword(s):  
Large Scale ◽  
Soft Soil ◽  
Soft Clay ◽  
Ground Surface ◽  
Field Performance ◽  
Soft Clays ◽  
Soil Clays ◽  
History Of ◽  
Creep Deformations ◽  
Surface Settlements

A case history of a deep multi-strutted soft clay excavation in Hangzhou is presented in this paper. What makes it particular interest is its three characteristics: large scale, deep excavation and very soft clays. The excavated area was about 99750 square meters. The depth of excavation was 12.85 m. 4 m below the ground surface located about 24 m very soft soil clays. Wall deflections and ground settlements were measured and compared with similar case histories worldwide. It was shown that the maximum horizontal deformations of the excavation was very large which this excavation reached to 220 mm. “Creep” deformations occurred apparently during the curing of the bottom slab of the basement. The distributions of the surface settlements seemed to be parabolic, and the settlement influence zone could reach to a distance of more than 2H, whereHis the final excavation depth. The ratio between the maximum ground settlement and the maximum horizontal deformation of the wall is about 0.6.

scholarly journals Investigation of Three-Dimensional Deformation Behavior due to Long and Large Excavation in Soft Clays

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Chunhui lou ◽  
Tangdai Xia ◽  
Nianwu Liu ◽  
Xiaonan Gong
Keyword(s):  
Deformation Behavior ◽  
Soft Clay ◽  
Three Dimensional ◽  
Significant Inhibition ◽  
Soft Clays ◽  
Extensive Field ◽  
Partition Walls ◽  
Reduction Coefficient ◽  
Cement Soil ◽  
Ground Settlements

By analyzing the extensive field data from a long and large excavation in soft clay, this study investigates the three-dimensional deformation behavior induced by excavation. Significant inhibition effects of corner on both wall deflections and ground settlements were observed and quantified. Thus, a modified function for estimating the distribution of deformation parallel to the excavation is proposed and evaluated. Further analyzing shows that the pipeline settlement can be well estimated by the modified function combining with settlements profile proposed by Hsieh and Ou, and the reduction coefficient is about 0.8; the calculated maximum distortion of the pipeline can provide reliable reference. In addition, it is found that the cement-soil partition walls can also considerably reduce the wall deflections and ground settlements even after the part that is above the excavation base were removed.

Evaluation of excavation-induced movements through case histories in Hangzhou

2020 ◽  
Vol 37 (6) ◽  
pp. 1993-2016
Author(s):  
Hong-Wei Ying ◽  
Kang Cheng ◽  
Li-Sha Zhang ◽  
Chang-Yu Ou ◽  
Yong-Wen Yang
Keyword(s):  
Field Observation ◽  
Relevant Literature ◽  
Soft Clay ◽  
Deep Excavation ◽  
Case Histories ◽  
Deep Excavations ◽  
Content Type ◽  
Wall Deflection ◽  
Semi Empirical ◽  
Ground Settlements

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.

scholarly journals Numerical analysis on zone-divided deep excavation in soft clays using a new small strain elasto–plastic constitutive model

2021 ◽  
Author(s):  
Afnan Younis Tanoli ◽  
Bin Yan ◽  
Yong-lin Xiong ◽  
Guan-lin Ye ◽  
Usama Khalid ◽  
...  
Keyword(s):  
Numerical Analysis ◽  
Constitutive Model ◽  
Small Strain ◽  
Deep Excavation ◽  
Soft Clays

scholarly journals Soil Creep Effect on Time-Dependent Deformation of Deep Braced Excavation

2022 ◽  
Vol 2022 ◽  
pp. 1-14
Author(s):  
Panpan Guo ◽  
Gang Lei ◽  
Lina Luo ◽  
Xiaonan Gong ◽  
Yixian Wang ◽  
...  
Keyword(s):  
Lateral Wall ◽  
Simulation Method ◽  
Observational Method ◽  
Braced Excavation ◽  
Soft Clays ◽  
Ground Movements ◽  
Creep Effect ◽  
Soil Creep ◽  
Braced Excavations ◽  
Plain Strain

This paper describes recent advances in the effect of soil creep on the time-dependent deformation of deep braced excavation. The effect of soil creep is generally investigated using the observational method and the plain-strain numerical simulation method. The observational method is more applicable for deep braced excavations in soft clays constructed using the top-down method. The plain-strain numerical simulation method can be conveniently used for parametric analysis, but it is unable to capture the spatial characteristics of soil creep effect on lateral wall deflections and ground movements. The additional lateral wall deflections and ground movements that are generated due to the soil creep effect can account for as large as 30% of the total displacements, which highlights the importance of considering the effect of soil creep in deep braced excavations through soft clays. The magnitude of the displacements due to soil creep depends on various factors, such as excavation depth, elapsed period, unsupported length, and strut stiffness. Parametric analyses have indicated several effective measures that can be taken in practice to mitigate the detrimental effect of soil creep on the deformation of deep braced excavation. Based on the literature review, potential directions of the related future research work are discussed. This paper should be beneficial for both researchers and engineers focusing on mitigating the adverse effect of soil creep on the stability of deep braced excavations.

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