Lateral Deformation Characteristics and Control Methods of Foundation Pits Subjected to Asymmetric Loads

Using the foundation pit at the Jianye Road Station of Hangzhou Metro Line 6 as a case study, the deformation characteristics of a foundation pit subjected to asymmetric loads is investigated in this paper using PLAXIS 3D numerical simulation software. The influence of active pressure zone reinforcement, passive pressure zone reinforcement, and increased thickness of the diaphragm wall at the loaded side on the maximum lateral displacement of diaphragm wall retaining structure of foundation pit is also systematically analyzed. The results show that the deformation of the diaphragm walls on both sides of the foundation pit is strongly inconsistent when subjected to asymmetric loads and is affected by the asymmetric load value and its distance to the foundation pit. In order to reduce the lateral deformations of foundation pit subjected to asymmetric load, two displacement control methods are adopted in the numerical simulations. It is shown that reinforcing the active pressure zone can reduce the maximum lateral displacement of the diaphragm wall on the loaded side to a certain extent but the reinforcement should have a certain depth, resulting in poor efficiency. On the other hand, reinforcing the passive pressure zone can effectively reduce the difference in lateral deformation between the two sides of the foundation pit by increasing the depth and width of the reinforcement zones. It is also observed that the increase in the thickness of the diaphragm wall can reduce the adverse effect of asymmetric loads on the foundation pit. The research results can provide reference for using measures to reduce the influence of asymmetric loads.

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A Case Study on Field Monitoring Analysis of Deep Foundation Pit in Soft Soils

Advances in Civil Engineering ◽

10.1155/2019/9342341 ◽

2019 ◽

Vol 2019 ◽

pp. 1-10 ◽

Cited By ~ 2

Author(s):

Xiaoshuang Zhang ◽

Xiuchuan Zhang ◽

Yunshan Han

Keyword(s):

Lateral Displacement ◽

Ground Surface ◽

Field Monitoring ◽

Diaphragm Wall ◽

Deep Foundation ◽

Foundation Pit ◽

Deep Foundation Pit ◽

Ground Surface Settlement ◽

Maximum Lateral Displacement

Field monitoring in the process of excavation of foundation pit is an important measure to reduce the risk. This paper describes a case study of the filed monitoring data during the process of deep foundation pit excavation in soft soil areas. The displacements of the diaphragm wall top were analysed and found that the horizontal displacement showed the convex shape, while the vertical displacement showed the concave shape. Based on the field monitoring data, the deformation mode of lateral displacement of the diaphragm wall belonged to the composite mode. The relationship between maximum lateral displacement and excavation depth showed a strong linear correlation. The horizontal displacements of bracing pillar decreased with the increasing of bracing stiffness, while the effect of bracing stiffness on vertical displacements of bracing pillar could be ignored. The settlement profile computed using the method of Hsieh and Ou was in good agreement with the field observations and better described the development trend of the ground surface settlement. The ratio of the maximum ground surface settlement (δvm) to the maximum lateral displacement of the diaphragm wall (δhm) was in the range of 0.74∼0.88, belonging to the range of 0.5∼1.0 proposed by Hsieh and Ou. This paper provides a reference basis and related guidance for similar projects.

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Comparative Analysis of the Influence of Different Construction Technology for Excavation on Adjacent Tunnels

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.638-640.884 ◽

2014 ◽

Vol 638-640 ◽

pp. 884-887

Author(s):

Yong Gang Du ◽

Jing Cao ◽

Zu De Ding

Keyword(s):

Lateral Displacement ◽

Internal Force ◽

Calculation Model ◽

Construction Technology ◽

Tunnel Structure ◽

Lateral Deformation ◽

Foundation Pit ◽

Engineering Construction ◽

Excavation Process ◽

Calculation Results

Based on the project of a foundation pit engineering adjacent to existing tunnel of Kunming metro line 1, a 3D calculation model is established in consideration the interaction of foundation pit support structures, tunnel structure and soil. In this paper, the authors have simulated the foundation pit excavation process in three conditions, and analyzed the changing laws of the lateral displacement and internal force of the tunnel induced by adjacent excavation under different conditions. Calculation results show that the distributions and the values of the displacement and internal force of the tunnel are obviously different under three different construction technologies, and the “jump dig” is the optimum excavation scheme due to the restriction in the excavation of foundation pit, and the lateral deformation of tunnel structure is smallest in this condition. The conclusion can provide a theoretical basis for similar excavation engineering construction.

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Deformation Law of the Diaphragm Wall during Deep Foundation Pit Construction on Lake and Sea Soft Soil in the Yangtze River Delta

Advances in Civil Engineering ◽

10.1155/2021/6682921 ◽

2021 ◽

Vol 2021 ◽

pp. 1-11

Author(s):

Yuan Mei ◽

Dongbo Zhou ◽

Xueyan Wang ◽

Liangjie Zhao ◽

Jinxin Shen ◽

...

Keyword(s):

Soft Soil ◽

Yangtze River Delta ◽

Diaphragm Wall ◽

Lateral Deformation ◽

Deep Foundation ◽

Foundation Pit ◽

Deep Foundation Pit ◽

Deformation Law ◽

Wall Deformation ◽

Subway Stations

So far, there have been a large number of diaphragm walls in the Yangtze River Delta as engineering examples of deep foundation pit maintenance structures in subway stations, but there is a lack of systematic research and summary on the deformation characteristics of ground connecting walls. This study aimed to clarify the deformation law of the diaphragm wall during the excavation of a deep foundation pit in a soft soil region. Based on the monitoring data of the diaphragm wall of the deep foundation pit of the Hangzhou metro station, the monitoring data of the deep foundation pits of 15 subway stations in Shanghai and Ningbo cities around Hangzhou were considered. Grouping and classification methods were used to analyze the similarities and differences in the deformation characteristics of the diaphragm wall in the three regions. The results indicate the following: the maximum lateral deformation of the diaphragm wall in Hangzhou increases linearly with the relative depth of the maximum lateral deformation. The maximum lateral deformation of the foundation pit in Hangzhou is 0.072% H∼0.459% H, with a mean of 0.173% H. The wall deformation in Hangzhou varies significantly with the depth of the foundation pit, but the influence of the depth of the foundation pit on the wall deformation is considerably less than that in Shanghai and Ningbo. The corresponding position of the maximum lateral deformation in the excavation depth increases linearly with the excavation depth of the foundation pit, and the corresponding position of the lateral deformation of the diaphragm wall in Shanghai is more affected by the excavation depth of the foundation pit. The lateral deformation of the diaphragm wall increases rapidly in the range of 0 H–0.5 H, and the maximum lateral deformation occurs at 0.5 H–1.1 H.

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The Influence of Vertical Loads on Lateral Deformation of Steel Reinforced Concrete Column

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.639-640.782 ◽

2013 ◽

Vol 639-640 ◽

pp. 782-785

Author(s):

Jia Jia Tian ◽

Hong Li

Keyword(s):

Reinforced Concrete ◽

Influencing Factors ◽

Lateral Displacement ◽

Concrete Columns ◽

Concrete Column ◽

Lateral Deformation ◽

Reinforced Concrete Column ◽

Reinforced Concrete Columns ◽

Steel Reinforced Concrete ◽

Maximum Lateral Displacement

The influence of vertical loads on steel reinforced concrete column is analyzed, based on the maximum lateral displacement of 2 different steel reinforced concrete columns under different vertical loads. The vertical loads, the section properties of the steel reinforced concrete column and horizontal loads are the influencing factors.

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Three-Dimensional Numerical Simulation Analysis of Security of the Underground Diaphragm Wall Based on the Ring Beam Supporting System

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.790.133 ◽

2013 ◽

Vol 790 ◽

pp. 133-137

Author(s):

Gan Zhou ◽

Ke Sheng Ding ◽

Shun Jian Yi ◽

Zhi Guang Fan

Keyword(s):

Numerical Simulation ◽

Simulation Analysis ◽

Lateral Displacement ◽

Three Dimensional ◽

Diaphragm Wall ◽

Foundation Pit ◽

Supporting System ◽

Dangerous Zone ◽

Area Monitoring ◽

Concrete Ring

The ring beam supporting system is a new kind of reasonable support system, which gives full play to the advantages that the concrete ring beam can bear reinforced huge pressure. Based on the analysis of the horizontal lateral displacement of diaphragm wall with three-dimensional numerical simulation, conclusion is obtained that the most dangerous zone exists in range of middle 1/4 of diaphragm wall, which is 0 ~ 6 m above the excavation surface and should be a key area monitoring. And there is enough space for pitting of earth in the process of foundation excavation, it also makes construction convenient and saves the time and cost of foundation pit support.

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A Theoretical and Experimental Investigation of Lateral Deformations in a Unilateral External Fixator

Journal of Medical Devices ◽

10.1115/1.2735972 ◽

2006 ◽

Vol 1 (2) ◽

pp. 165-172 ◽

Cited By ~ 2

Author(s):

Kerem Ün ◽

İbrahim D. Akçalı ◽

Mahir Gülşen

Keyword(s):

External Fixator ◽

Lateral Displacement ◽

Clinical Effectiveness ◽

Experimental Models ◽

Fracture Site ◽

External Fixators ◽

Deformation Characteristics ◽

Lateral Deformation ◽

Clinical Implementation ◽

Lateral Deformations

The objective of this work is to set up, validate, and analyze a theoretical model of an external fixator for its deformation characteristics in order to draw reliable conclusions relevant to the design and effective clinical implementation of such medical devices. External fixators are mechanical devices widely used in the treatment of fractured bones and correction of limb deformities. Lateral deformation at the fracture site is known to delay bone healing, and investigation of lateral deformation characteristics of such devices experiencing forces acting perpendicular to the bone axis is important from the standpoint of their design as well as their clinical effectiveness. A mathematical model of a three-dimensional (3D) unilateral fixator with multipin fragment attachments has been developed using Castigliano’s method. The relative lateral deformations of the fragment ends at the fracture site induced by loads applied perpendicular to bone axes are calculated with the model. The model has been subjected to experimental verification for a uniplanar unilateral external fixator under comparable conditions with the theory. It has been found out that the effects of fixator size, shape, and geometry on the level of relative lateral displacement of the fracture site are similar in both the theoretical and experimental models. Stiffness is a maximum if the force is applied in the same plane as the proximal pin plane. Placing the distal pin group at a 90deg position relative to the proximal pin plane has been observed to increase the stiffness about 10%. In loading directions perpendicular to proximal the pin plane, stiffness is minimum. The angle difference between the load direction and the resulting displacement direction follows a sinusoidal pattern with an amplitude of 10deg for loading angles in the 0–180deg range. Selecting the distance of proximal pins to the fracture site smaller than the distance of distal pins to the fracture site has been found to decrease relative lateral deformation. The model and the experiment have simultaneously demonstrated that lower values of effective pin lengths and higher values of pin connector lengths lead to higher stiffness. Increasing the number of pins also contributes to the higher values of fixator stiffness.

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Performance of a Large-Scale Excavation by Bottom-Up Technique in Hangzhou Soft Clay

Advances in Civil Engineering ◽

10.1155/2021/6061849 ◽

2021 ◽

Vol 2021 ◽

pp. 1-14

Author(s):

Ri-qing Xu ◽

Yi-hong Zhu ◽

Pan Ding

Keyword(s):

Large Scale ◽

Lateral Displacement ◽

Soft Soil ◽

Soft Clay ◽

Ground Surface ◽

Diaphragm Wall ◽

Subway Tunnel ◽

Control Effect ◽

Foundation Pit ◽

Rapid Excavation

This paper studied the excavation of a foundation pit above a running subway tunnel in Hangzhou soft soil. The zoned excavation and top-down construction techniques were adopted to control the deformation caused by foundation pit excavation. The excavation was divided into four parts, named Zone A, B, C, and D. Zone A adopted temporary diagonal bracing, and the control effect of deformation was poor; it was cancelled and changed to rapid excavation and thicker cushion in Zones B, C, and D. During the whole construction process, the lateral displacement and settlement of the diaphragm wall, surrounding ground surface, and building settlement were monitored and analysed. The data showed that the lateral displacement of the diaphragm wall was effectively reduced by the zoned excavation technique, and the maximum lateral displacement value of the diaphragm wall in Zone A was the least; rapid excavation and reduced soil exposure time also could effectively control the deformation, and the lateral displacement of the diaphragm wall in Zone C is less than Zone B and Zone D. The ground settlement is strongly related to the lateral displacement of the diaphragm wall. In order to reduce the surrounding ground and building settlements, efforts should be made to reduce the wall lateral displacement.

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