scholarly journals Study on Deformation Law of Deep Foundation Pit with the Top-Down Method and Its Influence on Adjacent Subway Tunnel

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Yue Gui ◽  
Zhenxing Zhao ◽  
Xiaqiang Qin ◽  
Jianfei Wang
Keyword(s):  
Axial Force ◽  
Ground Deformation ◽  
Diaphragm Wall ◽  
Subway Tunnel ◽  
Top Down ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Maximum Settlement ◽  
The Impact ◽  
The Relationship

Based on a long-term comprehensive instrumentation program, the performance of an excavation pit constructed by the top-down method in downtown Kunming was extensively examined. The measured excavation responses included the deflections of diaphragm wall, vertical column movement, slab axial force, building settlement caused by ground deformation, and the influence of pit excavation on the adjacent subway tunnel. This paper analyses the monitoring data of the existing construction stage. Based on the analyses on the data of field and numerical simulation, the following major findings were obtained: (1) the relationship between the measured maximum wall deflection, δ h m , and excavation depth, H , in this study is δ h m = 0.06 % H ∼ 0.27 % H , which is quite different compared with the relationship of soft-soil pit δ h m = 0.02 % H ∼ 1.2 % H , but closer to the normalized curve of rock-socketed pile δ h m = 0.01 % H ∼ 0.45 % H and rock-socketed diaphragm wall δ h m = 0.031 % H ∼ 0.129 % H . (2) The relationship between the maximum settlement of column ( δ p ) and excavation depth ( H ) is δ p = − 0.09 % ∼ 0.04 % H . The maximum distortion between the diaphragm wall and the column is less than 1/500 of the limit range proposed by Bjerrum. (3) The impact range caused by excavation is about 3.8 times the maximum excavation depth. The ground settlement around the foundation pit is groove type, and the maximum settlement point is located at 2.7 times the maximum excavation depth. (4) The excavation of the foundation pit leads to the maximum vertical settlement of 2 mm and maximum horizontal displacement of 5.2 mm in the subway tunnel; the maximum change of axial force and bending moment are 8.8 kN (the vertical direction) and 6.4 kN·m/m (the horizontal direction), respectively.

scholarly journals Evaluation of Deformation of Adjacent Buildings With Different Foundation Types Caused by Foundation Pit Excavation Under Combined Support of Isolation Pile and Diaphragm Wall

2021 ◽  
Author(s):  
Shaokun Ma ◽  
Fapai Tian ◽  
Zhen Huang ◽  
Hu Lu ◽  
Xiaoxi Fu ◽  
...  
Keyword(s):  
Pile Foundation ◽  
Horizontal Displacement ◽  
Diaphragm Wall ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Maximum Settlement ◽  
Deceleration Rate ◽  
Different Types ◽  
Diaphragm Walls

Abstract The process of excavation and unloading of a deep subway foundation pit will cause deformation of the surrounding buildings. There are significant differences in building deformation due to different methods of supporting the foundation pit and building foundation forms. This study takes the deep foundation pit project of the station as an example to investigate this difference. A three-dimensional numerical finite element model of a deep foundation pit has been established that considers different types of building foundations (independent foundation, box foundation, and pile foundation). The sensitivity of the two supporting methods of the diaphragm wall and the combined support of isolation pile and diaphragm wall regarding the maximum settlement value of the building, the horizontal inclination value, the slope angle, and the foundation angular distortions were analyzed. Finally, the sensitivity of the length of the isolated pile to the maximum settlement value and the horizontal displacement value of different types of building foundations are discussed. The results show that the combined support method of isolation piles and diaphragm walls has the highest supporting efficiency (93.5% of independent foundations and 42.3% of box foundations) for angular distortions of shallow foundation buildings. The efficiency of pile foundation support is the lowest (31.4%). For the combined support method of isolation piles and diaphragm walls, the maximum settlement value, and the value of horizontal displacement of the building will decrease with increasing the length of isolation pile. When the depth of isolation pile is greater than 24 m, the settlement deceleration rate of the independent foundation and the pile foundation slows down; when the depth of isolation pile is greater than 27 m, the settlement deceleration rate of the box foundation will slow down, and the deceleration rate of the horizontal displacement of the independent foundation and box foundation will slow down.

Prestressed Anchor Bolt Impact on the Deformation of Composite Soil Nailing

2013 ◽  
Vol 353-356 ◽  
pp. 11-15
Author(s):  
Deng Qun Wang ◽  
Yan Peng Zhu
Keyword(s):  
Axial Force ◽  
Horizontal Displacement ◽  
Vertical Displacement ◽  
Soil Nailing ◽  
Foundation Pit ◽  
Obvious Effect ◽  
Anchor Bolt ◽  
Soil Nail ◽  
Finite Element Software ◽  
The Impact

Finite element software was employed to establish a model to simulate the compound soil nailing. The model simulates the process of constructing prestressed compound soil nailing. Compared the condition prestressed with no prestress, analyzed the Impact of prestress anchor on the deformation in the process of construction and the effect on axial force of soil nail. Applying prestress is able to control the horizontal displacement obviously, but has not obvious effect on vertical displacement, especially place the anchor bolt at the lower part of the slope. In the process of construction, prestress has an advance effect on the deformation of foundation pit and the axial force of soil nails near the anchor bolt.

scholarly journals Analytical Study on Dynamic Response of Deep Foundation Pit Support Structure under the Action of Subway Train Vibration Load: A Case Study of Deep Foundation Pit of the New Museum Near Metro Line 2 in Chengdu, China

2015 ◽  
Vol 2015 ◽  
pp. 1-10
Author(s):  
Zhu Dapeng ◽  
Qin Liangkai ◽  
Lin Yundian
Keyword(s):  
Dynamic Response ◽  
Support Structures ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Vibration Load ◽  
Vibration Loads ◽  
Subway Train ◽  
The Impact ◽  
Train Vibration

Presently, foundation pit support structures are generally regarded as the temporary structures and the impact of vibration loads is often overlooked. As opposed to static and seismic loads, the vibration loads of subway trains are a type of cyclic load with a relatively long duration of action and a definite cycle; it is of great importance for the design of foundation pit support structures to correctly evaluate the impact of subway train vibrations on deep foundation pit and support works. In this paper, a dynamic three-dimensional numerical model is built that considers the vibration load of subway trains on the basis of the static numerical model for deep foundation pit support structures and simplified train loads to study the impact of train vibrations on deep foundation pit and permanent support structures. Studies have shown that the dynamic response of surface displacement mainly occurs in the early period of dynamic load, the vibration load of subway trains has little impact on ground subsidence, the support pile structure is in an elastic state during dynamic response under the action of subway train vibrations, and the action of train vibration loads is inimical to the safety of foundation pit support structures and should be closely studied.

scholarly journals Impact of High-Rise Buildings Construction Process on Adjacent Tunnels

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Haifeng Guo ◽  
Aijun Yao ◽  
Jiantao Zhang ◽  
Yijun Zhou ◽  
Yanfei Guo
Keyword(s):  
Earth Pressure ◽  
Scale Model ◽  
Construction Process ◽  
Deep Foundation ◽  
Deep Side ◽  
Foundation Pit ◽  
High Rise ◽  
Shallow Side ◽  
Deep Foundation Excavation ◽  
The Impact

The demand for buildings constructed along subway lines is increasing, and analysis of the impact of foundation excavation and building construction on adjacent tunnels is critical. This study investigated the variation law of tunnel deformation and surrounding earth pressure on an existing tunnel resulting from deep foundation excavation and the load of buildings. Four groups of scale model tests and corresponding numerical simulation calculations were conducted in four different modes: over unloading-loading, shallow-side unloading-loading, middle-side unloading-loading, and deep-side unloading-loading, which are according to the different relative position of the foundation pit and the tunnel. The results show that when the tunnel stretches across different areas, corresponding deformation occurs owing to the different mechanical mechanisms during excavation and loading. The results can provide evidence for the further study on the impact of adjacent construction process on the tunnels.

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

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.

scholarly journals Displacement Monitoring during the Excavation and Support of Deep Foundation Pit in Complex Environment

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Zhouqiang Li
Keyword(s):  
Axial Force ◽  
Time History ◽  
Horizontal Displacement ◽  
Underground Water ◽  
Surface Settlement ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Anchor Cable ◽  
The North

Taking a super large deep foundation pit project as an example, the horizontal displacement of crown beam and driveway, surface settlement, axial force of anchor cable, and underground water level in the construction process of the foundation pit are dynamically monitored and analyzed. The excavation deformation rule of the deep foundation pit and the influence of excavation on surrounding buildings are analyzed. The results show that, with the excavation of the foundation pit, the crown beam and driveway of the foundation pit incline towards the direction of the pit and eventually tend to be stable. The variation of axial force of the prestressed anchor cable in the first layer of the foundation pit is basically consistent with the variation of horizontal displacement time history. The variation trend of the groundwater level at each side of the foundation pit is different but tends to be stable in a short time. In the whole monitoring period, the cumulative settlement value of each area of the foundation pit is within the controllable range, but the surface settlement of the north side of the foundation pit and a surrounding building has not reached stability, so it is suggested to extend the monitoring time of settlement in the relevant area.

scholarly journals Finite-Difference Numerical Simulation of Dewatering System in a Large Deep Foundation Pit at Taunsa Barrage, Pakistan

2019 ◽  
Vol 11 (3) ◽  
pp. 694 ◽  
Author(s):  
Ijaz Ahmad ◽  
Muhammad Tayyab ◽  
Muhammad Zaman ◽  
Muhammad Anjum ◽  
Xiaohua Dong
Keyword(s):  
Hydraulic Conductivity ◽  
Finite Difference ◽  
Three Dimensional ◽  
Rehabilitation Program ◽  
Diaphragm Wall ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Constant Head ◽  
Design Depth

This study investigates a large deep foundation pit of a hydraulic structure rehabilitation program across the Indus river, in the Punjab province of Pakistan. The total area of the construction site was 195,040 m2. Two methods, constant head permeability test and Kozeny–Carman equation, were used to determine the hydraulic conductivity of riverbed strata, and numerical simulations using the three-dimensional finite-difference method were carried out. The simulations first used hydraulic conductivity parameters obtained by laboratory tests, which were revised during model calibration. Subsequently, the calibrated model was simulated by different aquifer hydraulic conductivity values to analyze its impact on the dewatering system. The hydraulic barrier function of an underground diaphragm wall was evaluated at five different depths: 0, 3, 6, 9, and 18 m below the riverbed level. The model results indicated that the aquifer drawdown decreases with the increase in depth of the underground diaphragm wall. An optimal design depth for the design of the dewatering system may be attained when it increases to 9 m below the riverbed level.

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