scholarly journals Numerical Investigation of a Foundation Pit Supported by a Composite Soil Nailing Structure

Symmetry ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 252 ◽  
Author(s):  
Wei Han ◽  
Genxiao Li ◽  
Zhaohui Sun ◽  
Hengjie Luan ◽  
Chuanzheng Liu ◽  
...  
Keyword(s):  
Side Wall ◽  
Horizontal Displacement ◽  
Middle Part ◽  
Soil Nailing ◽  
Foundation Pit ◽  
Soil Nails ◽  
Factors Affecting ◽  
Composite Soil Nailing ◽  
Soil Foundation ◽  
The Stability

In special geology conditions such as silt-soil, foundation pits are prone to instability and severe deformation. In this paper, a composite soil nailing structure was studied and its effect on a silt-soil symmetrical foundation pit investigated. The factors affecting the stability of the pit as well as its deformation characteristics were also explored. The results show that excavation depth of the foundation pit has a significant impact on its stability. The soil outside the foundation pit is in the form of a parabola, and the uplift of the soil mainly occurs at the bottom. The horizontal displacement of soil on the side wall of the foundation pit presents a “bulk belly” form. In addition, the axial force of soil nails is larger in the middle part, and smaller at both ends in the shape of a spindle. Moreover, the horizontal displacement is positively correlated with the inclination and spacing of the soil nails, but negatively correlated with the diameter and depth of the mixing pile inlay. Furthermore, the inclination and spacing of the soil nails, the diameter, and embedded depth of the mixing pile have their own critical values for stability of the foundation pit. Specifically, in this paper, with respect to soil nails, inclination should be below 30° and prestress value should not exceed 20 kN. With respect to the mixing pile, the diameter should be less than 1.5 m; when the embedded depth of the mixing pile exceeds the critical depth, the limiting effect of the mixing pile on horizontal displacement is not significant. This research provides important takeaways for the design of a composite soil nailing structure for symmetrical foundation pits.

scholarly journals Bearing Characteristics of Moso Bamboo Micropile-Composite Soil Nailing System in Soft Soil Areas

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Zhihe Cheng ◽  
Yousheng Deng
Keyword(s):  
Axial Force ◽  
Slip Surface ◽  
Soft Soil ◽  
Side Wall ◽  
Moso Bamboo ◽  
Shallow Foundation ◽  
Soil Nailing ◽  
Foundation Pit ◽  
Soil Nails ◽  
Composite Soil Nailing

Based on the characteristics of moso bamboo including high short-term strength, stable performance, and ability to provide temporary support for shallow foundation pits in soft soil, the stress characteristics and supporting effects of the ecological composite supporting system have been explored through model tests and numerical calculation analysis of the moso bamboo micropile-composite soil nailing structure. The results showed that the bamboo pile can effectively control the horizontal deformation of the side wall of the foundation pit and the ground surface settlement, achieving a relatively satisfactory supporting effect. Furthermore, the bamboo pile has visibly bent in middle and lower parts, where the regional shear point is most likely to appear, the axial force of the soil nail is distributed in an oval pattern with a smaller force on both sides and a larger force in the middle part, the maximum axial strain is 447.3 με, and the axial force of the soil nails in each row follows a similar trend. The synergy of piles and soil nails can delay the formation of the slip surface, therefore enhancing the overall bearing capacity of the foundation pit. These results can shed light on the support mechanism and engineering design of bamboo piles in shallow soft soil foundation pits.

Numerical Analysis of Composite Soil Nailing Wall

2014 ◽  
Vol 1065-1069 ◽  
pp. 48-52
Author(s):  
Shu Long Zhang ◽  
Fen Ting Lu
Keyword(s):  
Three Dimensional ◽  
Ground Surface ◽  
Horizontal Displacement ◽  
Soil Nailing ◽  
Construction Process ◽  
Three Dimensional Model ◽  
Foundation Pit ◽  
Finite Element Software ◽  
Ground Surface Settlement ◽  
Composite Soil Nailing

Abstract. The horizontal displacement of soil in slope and the change law of ground surface settlement are dynamically analyzed by building three dimensional-model of foundation pit with the finite element software, ABAQUS, to simulate the construction process of excavation and support, to figure out the influence of micro pile and waterproof curtain on composite soil nailing wall. The study indicates that mechanical model of soil nailing, waterproof curtain, micro pile, pre-stressed anchor interacting with soil can better simulate the construction process of composite soil nailing wall support and have higher calculation accuracy. The calculation can provide a reference for the design and construction of composite soil nailing wall.

Simulation Analysis on Tension and Deformation of Composite Soil Nailing

2013 ◽  
Vol 405-408 ◽  
pp. 182-186 ◽  
Author(s):  
Yan Lin Zhao ◽  
Hao Bin Zhang ◽  
Qing Pan Zhu ◽  
Dong Chen
Keyword(s):  
Simulation Analysis ◽  
Slip Surface ◽  
Soil Nailing ◽  
Foundation Pit ◽  
Initial Stress Field ◽  
Composite Soil Nailing ◽  
The Stability ◽  
The One ◽  
Backward Shifts ◽  
Prestressed Anchor

For studying the mechanism of the composite soil nailing, this paper applies FLAC-3D to simulate pure soil nailing, soil nailing-soil anchor, soil nailing-micro pile-soil anchor. The analytical results as follows: (1)Because of the anchoring of the anchor, the axial tension of soil nailing in each row is much smaller than the one in the pure soil nailing supporting, and the tension of soil nailing which are closed to soil anchor decreases obviously. (2)The extrusion action of prestressed anchor makes the potential slip surface backward shifts and the sliding radius increases, which is better for the stability of foundation pit side (3)Micro-pile increases the strength of the soil in a certain range and improves the initial stress field before the excavation. (4)The inner force of the whole soil nailing and the prestress anchor declines but the drop is not large after the establishment of the micro-pile support in advance. (5)Prestressed anchor and micropile play a very important role in controlling the deformation of foundation pit.

Design and Application of Special Slop Retaining

2010 ◽  
Vol 168-170 ◽  
pp. 652-657
Author(s):  
Li Ping Wen ◽  
Su Li Wang ◽  
Xu Ping Zhu
Keyword(s):  
Numerical Analysis ◽  
General Analysis ◽  
Soil Nailing ◽  
Analysis Program ◽  
Deep Foundation ◽  
Traditional Methods ◽  
Foundation Pit ◽  
Soil Nails ◽  
Deep Foundation Pit ◽  
Composite Soil Nailing

Taking the design of composite soil-nailing in deep foundation pit in complex surroundings for example, the paper discusses numerical analysis of soil-nailing using FLAC, a general analysis program of geotechnical engineering, used to predict the displacement and interior force in soil-nailing. Furthermore, a comparison about the interior force in soil nails between the numerical analysis and the traditional methods is made. The measurements show that the numerical analysis is more accurate than traditional methods. The conclusion is drawn that by contrast with the deficiency of traditional methods, more satisfactory results can be got from numerical analysis on composite soil-nailing using the program of FLAC.

Reinforcement Scheme and Numerical Simulation for Sequential Excavation of the Deep Foundation Pit

2012 ◽  
Vol 204-208 ◽  
pp. 359-365
Author(s):  
Rui Li Lu ◽  
Qing Hui Jiang
Keyword(s):  
Numerical Simulation ◽  
Middle Part ◽  
Deformation Monitoring ◽  
Soil Nailing ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Reinforcement Scheme ◽  
Deep Foundation Pit ◽  
Simulation Results ◽  
The Stability

The deep foundation pit engineering of Wanda Plaza in Yinchuan city is taken as a case study and the corresponding numerical model has been built. The deformation and stability of the foundation pit during sequential excavation has been analyzed by using of the FLAC3D software. The weak positions which may lose the stability are predicted by the results from the numerical simulation. A soil-nailing reinforcing scheme has been proposed to maintain the stability of the foundation pit. To analyze the support effects of the soil-nailing, the Cable structure elements have been adopted to simulate the interaction between soil and soil-nailing. The calculation results show that the maximum horizontal displacement occurs in the middle part of the pit wall and the minimum occurs in corner part of the pit wall. The soil nailing support significantly decreases the deformation of foundation pit by dispersing internal stress of soil. The reliability of the simulation results has been verified by the comparative analysis between the numerical simulation results and the deformation monitoring data of foundation pit. The proposed reinforcement scheme is not only helpful to ensure the safety of Wanda Plaza foundation pit，but also provides valuable experiences for the reinforcement of similar foundation pit engineering.

Study on Composite Soil Nailing Wall in Soft Soil Area of Complex Condition with Emphasis on Analysis by Finite Element Analysis

2012 ◽  
Vol 174-177 ◽  
pp. 2020-2023 ◽  
Author(s):  
Bing Wang
Keyword(s):  
Finite Element ◽  
Soft Soil ◽  
Horizontal Displacement ◽  
Deep Foundation ◽  
Circular Area ◽  
Foundation Pit ◽  
Soil Nails ◽  
Deep Foundation Pit ◽  
Soft Soil Area ◽  
Soil Area

Based on a typical projects, the horizontal displacement in depth, horizontal displacement and vertical subsidence of pile top, and settlements of surrounding buildings are monitored with the process on digging of deep foundation pit. The study on digging process of foundation pit is analyzed by using finite element software. Using mapped meshing method, from mixing the pile near the semi-circular area (radius = 50m), the meshing appropriate encryption in order to improve the accuracy of the external semi-circular area (radius = 65m) mesh is less appropriate sparse.Layer by layer to kill the layers of the soil unit and activate the soil nails (spring element), the simulated excavation and synchronization of soil nails construction.Verify the arc form of failure surface in side of deep foundation pit in soft soil area. Which is valuable for reference to similar structure engineering of foundation pit.

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.

The Stability of Unsaturated Soil Foundation Pit Reinforced with the Cement-Mixed Sheet Pile Wall

2011 ◽  
Vol 142 ◽  
pp. 243-246
Author(s):  
Rong Jian Li ◽  
Hao Duan ◽  
Wen Zheng ◽  
Hai Tao Li
Keyword(s):  
Safety Factor ◽  
Unsaturated Soil ◽  
Matric Suction ◽  
Sheet Pile ◽  
Foundation Pit ◽  
Constant Height ◽  
Overall Stability ◽  
Soil Foundation ◽  
The Stability ◽  
Sheet Pile Wall

The non-uniform distribution of matric suction in the unsaturated soil has a great impact on the stability of the unsaturated soil foundation pit. By means of the strength reduction finite element method, the stability of the unsaturated soil foundation pit reinforced with the cement-mixed sheet pile wall was analyzed. The overall safety factor of the unsaturated soil foundation pit reinforced with the cement-mixed sheet pile wall is greatly reduced and the position of potential sliding surface goes upward with the gradually decreasing of matric suction. With the constant height of the cement-mixed sheet pile wall, the shallower the embedding depth of the cement-mixed sheet pile wall is, the smaller the safety factor of the foundation pit slope is. The results show that the safety factor of the overall stability of the unsaturated soil foundation pit decreases with the deep excavation and the gradually decreasing of the matric suction.

scholarly journals Full-Scale Field Test On Retaining Structure Enhanced With Soil Nails And Prestressed Anchors

2021 ◽  
Author(s):  
Hui Wang ◽  
Jian-hua Cheng ◽  
Yuan-cheng Guo
Keyword(s):  
Rational Design ◽  
Horizontal Displacement ◽  
In Situ Tests ◽  
Foundation Pit ◽  
Soil Nails ◽  
Soil Nail ◽  
Retaining Structure ◽  
Prestressing Force ◽  
Materials Used ◽  
Unbonded Length

Abstract Retaining structure enhanced with soil nails and prestressed anchors is found good at constraining the horizontal displacement and therefore ensuring the stability of the foundation pit during excavation. Based on these advantages, such retaining structure is widely used in foundation excavation practice. This paper presents results of a series of in-situ tests conducted to investigate the mechanical behaviors of retaining structure enhanced with soil nails and prestressed anchors. Behaviors of three different retaining structures enhanced with i) soil-nails; ii) soil-nails and prestressed anchors without unbonded part; iii) soil-nails and prestressed anchors with a 2.5m unbonded length, were monitored during staged excavation to investigate the influences of i) the prestressing force and ii) unbonded length of the prestressed anchors on the performance of the entire retaining system. It was found that the affecting the stress and deformation of composite retaining system, which is in agreement with the other published results in the literature. The variation of the magnitude and distribution of soil nail force responding to the anchor prestressing force however showed no systematic trend. The unbonded length of anchors, which is suggested to be the main factor affecting the structural stability in dense materials in the literature, is found to have little influence in loose fill materials used in this study. Studies presented in this paper are useful for the rational design and serviceability analysis of the composite soil-nailed retaining structure enhanced with prestressed anchors.

scholarly journals Parameter optimization of double side wall method for soft surrounding rock tunnel

2019 ◽  
Vol 136 ◽  
pp. 04021
Author(s):  
Zhihua Yang ◽  
Rumiao He ◽  
Ke Li ◽  
Hongyan Guo
Keyword(s):  
Side Wall ◽  
Horizontal Displacement ◽  
Vertical Displacement ◽  
Surrounding Rock ◽  
Radius Of Curvature ◽  
Tunnel Excavation ◽  
The Stability ◽  
Rock Tunnel ◽  
Double Wall ◽  
Wall Method

When the Xiaojiazhai tunnel is constructed by the double-wall method, different curvature radii have different effects on controlling the stability of the surrounding rock and speeding up the construction progress. By numerically simulating the tunnel excavation under different radius of curvature, it is concluded that R is adopted respectively. The deformation displacement of surrounding rock is =11.6m∠520 and R=5.76m∠1060. The maximum horizontal displacement and vertical displacement are smaller when R=5.76m∠1060 is selected. According to the analysis results, when R=5.76m∠1060 is selected, the deformation of surrounding rock can be controlled to ensure the safety of construction and provide reference for future construction.

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