scholarly journals Analysis on Deformation and Stress Characteristics of a Multibraced Pit-in-Pit Excavation in a Subway Transfer Station

2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Xin Shi ◽  
Chuanxin Rong ◽  
Hua Cheng ◽  
Linzhao Cui ◽  
Bin Wang ◽  
...  
Keyword(s):  
Ground Surface ◽  
Lateral Wall ◽  
Surface Settlement ◽  
Lateral Deformation ◽  
Monitoring And Control ◽  
Foundation Pit ◽  
Wall Displacement ◽  
Transfer Station ◽  
Ground Surface Settlement ◽  
Total Settlement

As an important part of subway transfer station construction, pit-in-pit (PIP) excavation has always been a key object of monitoring and control. In this study, taking the PIP excavation project of Hefei metro line 4 and line 7 transfer station as the background, combined with on-site monitoring and numerical simulation, the variation law of lateral wall displacement, ground surface settlement, and strut force during the PIP excavation were analyzed. The results showed that the maximum lateral deformation of the pile caused by the excavation of the external pit accounted for 80%–90% of the total deformation and the surface settlement accounted for 70% of the total settlement. The excavation of the inner pit only made the maximum lateral wall displacement of the outer pit and the surface settlement behind the wall increase slightly, the growth rate tended to zero, and the maximum lateral deformation depth was all above the excavation surface, which indicated that, for this project, the inner excavation had little effect on the outer pit retaining structure. In addition, the increased exposure time of the soil at the bottom of the pit and the presence of the corner effect will cause the further development of the structure displacement and the surface settlement. Based on strut force measurements, using the tributary area load distribution procedure, it was obtained that 0.3γHe was used as the upper limit index of strut force in the region, where γ is the weight of the soil and He is the excavation depth of the foundation pit. The research conclusions were helpful for the construction and sustainable development of the PIP project.

scholarly journals Deformation Characteristics of Raising, Widening of Old Roadway on Soft Soil Foundation

Symmetry ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 2117
Author(s):  
Keke Li ◽  
Wenyuan Xu ◽  
Liang Yang
Keyword(s):  
Lateral Displacement ◽  
Soft Soil ◽  
Ground Surface ◽  
Surface Settlement ◽  
Deformation Characteristics ◽  
Construction Methods ◽  
Ground Surface Settlement ◽  
Total Settlement ◽  
Soil Foundation ◽  
Soft Soil Foundation

The deformation characteristics of a raised and widened old Chinese roadway on a soft soil foundation are investigated in this study via finite element numerical simulation. The rules of ground surface settlement, slope foot lateral displacement, and ground surface settlement evolution of the roadbed under three modes (one-time construction of an eight-lane expressway, widened four-lane expressway, and raised/widened four-lane expressway) are compared. The ground surface settlement process of the eight-lane road foundation, which is formed by first widening and then raising the road, is highly complex. The ground surface settlement curve under the old road foundation increases and then decreases. The lateral displacement of the slope foot also interacts with the widening and raising of the eight-lane roadbed foundation. The range of lateral displacement is 70.05, 42.58, 124.81, 104.54 mm. Fifteen years after construction, the total settlement of the raised and widened roadbed is much larger than that of the one built directly. The total settlement values at the center of the two roadbeds are 297.05 and 234.85 mm, respectively. This manuscript provides data support for the reconstruction and expansion of roads on soft soil foundations, for choosing appropriate construction methods to build roads, and for avoiding major road damage, which is of great significance to the construction of road infrastructure in the future.

scholarly journals Numerical Analysis on the Performance of the Underwater Excavation

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Bo Li ◽  
Cangqin Jia ◽  
Guihe Wang ◽  
Jun Ren ◽  
Gaofeng Lu ◽  
...  
Keyword(s):  
Numerical Analysis ◽  
Retaining Wall ◽  
Lateral Wall ◽  
Surface Settlement ◽  
Design Parameters ◽  
Analysis Model ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Wall Deflection ◽  
Total Settlement

Based on the Yongdingmen Station of Beijing Metro, the underwater excavation method for deep foundation pit was introduced. This study constructed a numerical analysis model to analyze the performance of surface settlement and lateral wall deflection in the process of underwater excavation. Results showed that this method was better to control the surface settlement and lateral wall deflection compared with other dewatering excavations. In detail, most of the surface settlement was caused during the dry excavation stage and dewatering excavation stage while the deflection caused by underwater excavation only accounted for about 10% of the total settlement. Besides, the maximum settlement occurred 0.25∼0.5 H e behind the retaining wall and the value was 0.04% H e . Similar to the result of the surface settlement, most of the lateral wall deflection had been completed before the underwater excavation, which only caused about 7% of the total deflection. The maximum wall deflection and its location were approximately 0.06% H e and 0.5 H e , respectively. Moreover, a series of 3D numerical analyses were studied on the design parameters of the underwater excavation method. This study can be used as a reference for general performance and structural design of foundation pits with underwater excavation.

scholarly journals Sequential Measurement and Analysis of Large Underground Retaining Structures by Diaphragm Wall Anchor for the Spring Area

2019 ◽  
Vol 2019 ◽  
pp. 1-21
Author(s):  
Jicheng Shu ◽  
Jianping Sun ◽  
Dingwen Zhang ◽  
Huanwei Wei
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Ground Surface ◽  
Lateral Wall ◽  
Horizontal Displacement ◽  
Surface Settlement ◽  
Diaphragm Wall ◽  
Earth Pressures ◽  
Spring Area ◽  
Ground Surface Settlement

The performance of a diaphragm wall-anchor structure in spring area in Jinan city, China, is studied. Based on field measured data, lateral wall deflections, lateral soil movements, horizontal displacement of the capping beam, the maximum lateral wall deflection, ground surface settlement, lateral earth pressures on diaphragm wall, internal force of diaphragm wall, axial anchoring forces, settlements of adjacent building, and pore-water pressure are investigated. The results indicate that the maximum deflections of the lateral wall are 0.07%∼0.18% of the excavation depth (He). The ground surface settlement influence zone extends beyond 2.5He from the pit for this project. The δv,max ranges from 0.67 δh,max to 1.0 δh,max. The maximum lateral active earth pressures on diaphragm walls above the excavation bases range between 0.4He and 0.6He. The axial anchoring forces of the top three layers of anchors change significantly during the excavation while the axial anchoring force of the fourth layer of anchor is constant. The deformation of surrounding building has three stages, including a uniform subsidence stage, an accelerated subsidence stage, and a stable subsidence stage.

Characteristics of ground surface settlement during excavation

1993 ◽  
Vol 30 (5) ◽  
pp. 758-767 ◽  
Author(s):  
Chang-Yu Ou ◽  
Pio-Go Hsieh ◽  
Dar-Chang Chiou
Keyword(s):  
Plane Strain ◽  
Empirical Formula ◽  
Ground Surface ◽  
Lateral Wall ◽  
Surface Settlement ◽  
Observation Data ◽  
Wall Deflection ◽  
Ground Surface Settlement ◽  
Field Observation Data ◽  
Center Section

The objective of this paper is to study the characteristics of ground surface settlement during excavation. Ten excavation cases in Taipei with good-quality construction and field observation data are selected to study the characteristics of excavation behavior. The location of maximum lateral wall deflection, magnitude of maximum lateral wall deflection, relationship of maximum lateral wall deflection and maximum ground surface settlement, location of maximum ground surface settlement, and apparent influence range are thus established based on the actual excavation cases. Finally, an empirical formula is proposed to predict the ground surface settlement profile at the center section of an excavation, where the behavior may be characterized by plane-strain conditions. Key words : excavation, surfac settlement, wall deflection, plane strain, empirical formula.

Numerical Simulation of Ground Surface Settlement Induced by Open-Cut Subway Station

2014 ◽  
Vol 522-524 ◽  
pp. 1689-1692
Author(s):  
Yan Hui Guo ◽  
Ke Peng Hou
Keyword(s):  
Optimization Design ◽  
Three Dimensional ◽  
Ground Surface ◽  
Surface Settlement ◽  
Subway Station ◽  
Structure Stability ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Ground Surface Settlement ◽  
Survey Results

Ground surface settlement induced by open-cut subway station has important implications for construction safety. Based on a subway station background of the line 3 west extension engineering of kunming metro line co.LTD. On the basis of geological survey results and indoor geotechnical mechanics experiment, the 3D geological model was established by three-dimensional finite difference method FLAC3D. Ground surface settlement Law and Retaining structure stability induced by subway station construction was analyzed. The analysis results provides a reference for structure optimization design and scientific construction of similar deep foundation pit engineering.

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