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.

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.

Soil behaviour through field instrumentation

2005 ◽  
Vol 42 (2) ◽  
pp. 475-490 ◽  
Author(s):  
Sadik Oztoprak ◽  
S Feyza Cinicioglu
Keyword(s):  
Field Measurements ◽  
State Theory ◽  
Stress Axis ◽  
Design Parameters ◽  
Observational Method ◽  
Rate Dependency ◽  
Soft Clays ◽  
Field Instrumentation ◽  
Axis Rotation ◽  
Soil Behaviour

An improved version of the observational method is developed and proposed. The method uses field measurements as the direct inputs to the framework of the constitutive behaviour and analyses the behaviour synchronously as measurements are recorded. The method is developed for the specific case of embankments on soft clays, and its effectiveness is tested on a well-documented case history. The framework provided for the application of the method is basically the idealized stress space of the critical state theory, but the constitutive anisotropic elastoplastic soil model is added to this framework to analyse the behaviour and provide direct links between measurements and design parameters. Strain-rate dependency of the soft soils is also incorporated in the interpretation of the behaviour. To consider the variation in the behaviour of foundation soils, a zonation system is applied. Stress axis rotation is considered for active and passive regions effectively. Substantial savings can be achieved using the method in terms of time and cost, and the method is reliable. In addition, such an application improves the understanding of the real behaviour of soils.Key words: soft clays, embankment, observational method, rate effect, anisotropy, soil structure.

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