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.

Application of Prestressed Anchor Composite Soil Nail Wall in Deep Foundation Pit Engineering at Lanzhou Region

2014 ◽  
Vol 1030-1032 ◽  
pp. 714-718
Author(s):  
Hui Tao
Keyword(s):  
Soil Layer ◽  
Horizontal Displacement ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Soil Nails ◽  
Change Rate ◽  
Deep Foundation Pit ◽  
Soil Nail ◽  
Support Engineering ◽  
Prestressed Anchor

The paper introduces the application of prestressed anchors and soil nails support system in complex soil layer deep foundation pit engineering at Lanzhou region based on the deep foundation pit engineering in Gansu Provincial Hospital of TCM as the background and discusses its key technology. The effect shows that scheme of the design of foundation pit support engineering is reasonable and effective.The engineering meets requirements of design and environment.The monitoring results show that prestressed anchors can control the horizontal displacement and the change rate of slope′s vertical settlement effectively. The experience of engineering is significance for similar engineerings at Lanzhou region.

scholarly journals Full-Scale Field Test on Construction Mechanical Behaviors of Retaining Structure Enhanced with Soil Nails and Prestressed Anchors

2021 ◽  
Vol 11 (17) ◽  
pp. 7928
Author(s):  
Hui Wang ◽  
Jianhua Cheng ◽  
Hujun Li ◽  
Zhilin Dun ◽  
Baoquan Cheng
Keyword(s):  
Field Test ◽  
Working Conditions ◽  
Horizontal Displacement ◽  
Displacement Current ◽  
In Situ Tests ◽  
External Disturbances ◽  
Time Curve ◽  
Soil Nails ◽  
Prestressing Force ◽  
Main Factor

Soil nailing combined with prestressed anchors has a good workability and is relatively cheap in constraining the horizontal displacement. Current research on the technique, whether theoretical analyses, numerical simulations, or model tests, was conducted under ideal working conditions. However, in fact, external disturbances, such as tensioning-lagging of the anchor, are very common and play an important role on stress and displacement. Therefore, it is of great significance to carry out a field test considering the effects of external disturbances, which can obtain real and reliable data through real-time monitoring. In this paper, the impacts of the construction conditions on practical engineering are discussed based on in situ tests, and some reasonable suggestions for the upgrading of misbehaviors in the current construction situation are put forward. In particular, the influence features of soil predisturbance, excessive excavation, unloading on the surface of edges, tensioning-lagging of the anchor, and continuous rainfall on the stress–time curve of soil nails under practical working conditions are analyzed. Behaviors of three different retaining structures enhanced with (i) soil nails; (ii) soil nails and prestressed anchors without unbonded parts; and (iii) soil nails and prestressed anchors with a 2.5 m unbonded part were monitored during staged excavation to investigate the influences of (i) the prestressing force and (ii) the unbonded part of the prestressed anchors on the performance of the entire retaining system. Results show that (i) the prestressing force is the main factor affecting the stress and deformation of the composite retaining system, which is consistent with the existing literature; (ii) the variation of the magnitude and distribution of the soil nail force responding to the anchor prestressing force, however, showed no systematic trend; and (iii) the unbonded part of anchors, which was validated to be the main factor affecting the structural stability in dense materials in the existing literature, is found to have a minor influence in loose fill materials used in this study.

On Numerical Simulation of the Stepped Soil-Nail Wall

2013 ◽  
Vol 353-356 ◽  
pp. 692-695
Author(s):  
Chang Zhi Zhu ◽  
Quan Chen Gao
Keyword(s):  
Numerical Simulation ◽  
Numerical Analysis ◽  
Internal Force ◽  
Numerical Results ◽  
Analysis Model ◽  
Foundation Pit ◽  
Soil Nails ◽  
Soil Nail ◽  
Soil Nail Wall ◽  
Design And Construction

Based on an Engineering Example which was supported by the stepped soil-nail wall, a numerical analysis model was established by FLAC3D,and the process of the excavation and supporting was simulated, and the numerical results of the soil nails internal force and foundation pit deformation were obtained. The simulated result was consistent with the measured results. It shows that the method of FLAC3D numerical analysis can be used to the numerical analysis of foundation pit excavation and supporting, and it will provide the basis for the design and construction of practice project.

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.

Effect of Staged Excavation on Retaining Structure in Soft Soil Area

2012 ◽  
Vol 170-173 ◽  
pp. 633-636 ◽  
Author(s):  
Jie Liu ◽  
Xin Guang Xu
Keyword(s):  
Soft Soil ◽  
Horizontal Displacement ◽  
Structure Type ◽  
Operating Conditions ◽  
Deep Soil ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit ◽  
Retaining Structure ◽  
Geological Conditions

Based on a deep foundation pit in Tianjin, the authors introduced the retaining structure type, surrounding conditions, and the geological conditions of proposed field. According to the engineering characteristics, the excavation was divided into three typical operating conditions. Based on the monitoring of staged excavation of deep foundation pit, analysis on horizontal displacement, deep soil displacement, column settlement and bracing axial force was carried out. The general rules of the deformation and internal force of retaining structures induced by staged excavation were given, which will provide the references for similar engineering.

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.

Optimization Simulations of Support System by Composite Soil-Nail Retaining Structure

2012 ◽  
Vol 166-169 ◽  
pp. 863-868 ◽  
Author(s):  
Jian Hua Huang ◽  
Guang Song ◽  
Er Xaing Song
Keyword(s):  
Mechanical Characteristics ◽  
Soil Layer ◽  
Simulation Software ◽  
Three Dimension ◽  
Foundation Pit ◽  
Soil Nail ◽  
Retaining Structure ◽  
Tension Distribution ◽  
Deformation Features ◽  
Nonlinear Numerical Simulation

Mechanism of composite pre-reinforced micro pile soil-nail and pure soil-nail retaining structure in foundation-pit engineering are analyzed in this paper through general three dimension nonlinear numerical simulation software. Research contents include whole construction process simulation of construction such as excavation by steps, piles and soil-nail installation and panel manufacture etc. By the comparison of mechanical characteristics between the pure soil-nail and composite soil-nail retaining structures in the same slope engineering example, differences of tension distribution range of soil layer, deformation features, mechanical characteristics of support and axial force distribution along nails etc. are analyzed. Research results are verified by in-site projects and measured data. The action mechanism and working performance of composite soil-nail retaining support are also systematically studied and theoretical basis can be provided in the similar application.

Application of Mc Composite Retaining Structure in the Silt Soil Foundation

2013 ◽  
Vol 353-356 ◽  
pp. 341-346
Author(s):  
Ying Cheng ◽  
Ai Zhao Zhou
Keyword(s):  
Retaining Wall ◽  
Ground Surface ◽  
Bending Moment ◽  
Horizontal Displacement ◽  
Foundation Pit ◽  
Wall Width ◽  
Obvious Effect ◽  
Retaining Structure ◽  
Supporting Structure ◽  
Soil Foundation

This pape combined with the engineering example of a supporting muddy soil foundation pit,used the finite element numerical analysis method, discussed on mechanical deformation characteristics of the cement-soil pile and concrete pile composite retaining structure (MC pile for short ) , Including the effect of section parameters of MC pile on the horizontal displacement of supporting structure, settlement of ground surface and bottom heave. The results show that, MC pile composite retaining structure are beneficial to control the deformation of foundation pit, and increase the stability of foundation pit; M pile retaining wall width to reduce the deformation of the retaining structure has obvious effect, which increase the width of wall can decrease the bending moment ,inclination deformation of supporting structure and lowe bottom heave and surface settlement. Moreover, in the same wall width, there is no C pile to control the deformation of the retaining structure and deformation of the foundation also has a great role.

The Cause of Instability and Reinforcement of the Complicated High Slope Drawing near a Deep-Founding Pit

2011 ◽  
Vol 368-373 ◽  
pp. 2022-2026
Author(s):  
Qi Yun Wang ◽  
Jia Sheng Zhang ◽  
Jin Xu
Keyword(s):  
Retaining Wall ◽  
Horizontal Displacement ◽  
Deformation Monitoring ◽  
Deep Soil ◽  
Support Structure ◽  
Foundation Pit ◽  
Technical Data ◽  
Factors Affecting ◽  
Retaining Structure ◽  
Bracing System

The combination of a single row of artificially-dug-up piles and pre-stressed anchor rope was adopted to the foundation pit as the retaining structure,and anchor-plate retaining structure and rubble retaining wall were used as the bracing system for the complicated building slope. In the process of excavation, monitoring has been done to see if any horizontal displacement, deformation of deep soil and crack width take place or any technical data and code dispatch from the demand. Monitoring results show that deformation in some parts of the tops of support structure is larger than the designed warning value some times and the deformation continue to increase in the process of the excavation, and this result in twice dangerous situations in the support structure of the slope. In this paper, the geologic construction of the slope and the situations of the designed support structure and monitoring condition were depicted. The mechanism of the instability of the slope was explained on the basis of comprehensive analysis of deformation monitoring datas. It is concluded that the over-excavation, explosive excavation, rainfall and so on were the factors affecting the stability of the slope. Corresponding emergency measures and reinforcement measures,such as unloading and pre-stress rope, were proposed, which were proved to be highly effective.

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