scholarly journals Study on Microscopic Roadbed Grouting Mechanism Based on CFD-DEM Coupling Algorithm

2020 ◽  
Vol 2020 ◽  
pp. 1-9 ◽  
Author(s):  
Changwei Yang ◽  
Jinhao Guo ◽  
Jing Lian ◽  
Zhimeng Wang
Keyword(s):  
Diffusion Mechanism ◽  
New Method ◽  
Discrete Elements ◽  
Finite Element Software ◽  
Grouting Pressure ◽  
Site Survey ◽  
Intercity Railway ◽  
Coupling Principle ◽  
Grouting Reinforcement ◽  
Coupling Algorithm

Grouting reinforcement technology gradually has been widely used to repair the subgrade settlement diseases, but the current single application of discrete element software or finite element software cannot effectively simulate the grouting process. Therefore, one new method is put forward in the research of grouting based on the CFD-DEM coupling principle. And then, one typical subgrade section in the Shanghai–Nanjing intercity railway is used to simulate the grouting process and diffusion mechanism of slurry from microlevel. Based on the results of site survey, some findings are shown as follows: First, the new method is feasible which integrates the favorable aspects of discrete elements, finite elements, and boundary elements. Second, the greater the grouting pressure, the greater the influence range of grouting, and it shows six petals shape. When the grouting pressure is small, the grouting generally shows penetration or extrusion grouting, and its influence range is small. When the grouting pressure is large enough, it is characterized by splitting grouting, and the influence range of grouting is getting larger and larger. Third, the growth rates of influence range gradually increase with the increasement of grouting pressures, and the reasonable selection of grouting pressures is very important.

Three-dimensional analysis of anchored wall with concrete bearing pads

2020 ◽  
Vol 18 (6) ◽  
pp. 1469-1486
Author(s):  
Hamed Arefizadeh ◽  
Hadi Shahir
Keyword(s):  
Design Methodology ◽  
Three Dimensional ◽  
Bending Moments ◽  
Dimensional Model ◽  
Discrete Elements ◽  
Three Dimensional Model ◽  
Content Type ◽  
Finite Element Software ◽  
Internal Forces ◽  
Soldier Pile

Purpose Anchorage with concrete bearing pad is commonly used in Iran for stabilization of excavations because of the ease of construction, less costs and less time consumption than the soldier pile method. In this method, a wall facing which includes the concrete bearing pads at the location of the anchors and a shotcrete layer between the bearing pads is constructed parallel to the excavation operation similar to the nailing method. Design/methodology/approach In this paper, using the finite element software Abaqus, a three-dimensional model of the above-mentioned type of wall is constructed, and the effect of spacing and size of bearing pads on the wall behavior is discussed. Findings According to the obtained results, the size of the concrete bearing pads has little effect on wall deformations, but the internal forces and bending moments developed in the shotcrete layer between the bearing pads are greatly influenced by the bearing pads dimensions and spacing. Originality/value Owing to the discrete elements of the wall facing, the behavior of this system is completely three-dimensional.

scholarly journals Comparative Study of Soil Grouting with Cement Slurry and Cement-Sodium Silicate Slurry

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Mingting Zhu ◽  
Qingsong Zhang ◽  
Xiao Zhang ◽  
Bing Hui
Keyword(s):  
Sodium Silicate ◽  
Large Scale ◽  
Setting Time ◽  
Initial Pressure ◽  
Cement Slurry ◽  
Viscosity Change ◽  
Grouting Pressure ◽  
Curtain Grouting ◽  
Grouting Reinforcement

Cement slurry and cement-sodium silicate slurry are most widely applied for soil grouting reinforcement project. The viscosity change of cement slurry is negligible during grouting period and presumed to be time independent, while the viscosity of cement-sodium silicate slurry increases with time quickly and is presumed to be time dependent. Due to the significant rheological differences between them, the grouting quality and the increasing characteristics of grouting parameters may be different. Those are main factors for grouting design. In this paper, a large-scale 3D grouting simulation device was developed to simulate the surrounding curtain grouting for a tunnel. Two series of surrounding curtain grouting experiments under different initial pressures of 100 kPa, 150 kPa, and 200 kPa were performed. The overload test on the tunnel was performed to evaluate the grouting quality of all surrounding curtain grouting experiments. The results show that the increasing trend of grouting pressure for cement-sodium silicate is similar to its viscosity; the setting time of cement-sodium silicate slurry obtained from the laboratory test is less than that in the practical grouting environment where grout slurry solidifies in soil; the grouting quality of cement-sodium silicate slurry is better than cement slurry, and the grouting quality decreases with initial pressure.

scholarly journals A New Method for Reducing Collapsibility of Loess Foundation with Thicker Deposit: The Borehole Preimmersion Method

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Bin Zhi ◽  
Xiaochan Wang ◽  
Pingping Wei ◽  
Zengyue Li ◽  
Pan Wang ◽  
...  
Keyword(s):  
Water Consumption ◽  
Diffusion Mechanism ◽  
Water Injection ◽  
Immersion Test ◽  
Calculation Model ◽  
New Method ◽  
Total Water ◽  
Injection Hole ◽  
Total Water Consumption ◽  
New Perspective

At present, there are some key issues in the traditional preimmersion method for reducing the collapsibility of the loess ground, such as the difficulty in determining the total water consumption and the long immersion time. In response to these issues, a new method, the borehole preimmersion method, is presented, and a specific theoretical design model is proposed for application in projects. The method is specifically discussed from a new perspective, and the diffusion mechanism and evolution law of water in the ground are presented in detail through theoretical analysis and numerical calculation, respectively. The water diffusion is a mushroom-type form for a single water injection hole immersed in water. A calculation model derived for a single water injection hole or a group of water injection holes based on the research results is used to calculate the volumes of soaked loess and the total water consumption. Through an in situ immersion test, the treatment effect of this method is evaluated to verify the rationality of the method and the theoretical calculation model proposed in this study, which provides a new method and theoretical framework for effectively reducing the collapsibility of the loess ground.

scholarly journals Study on the Instability Mechanism and Grouting Reinforcement Repair of Large-Scale Underground Stopes

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Chengyu Xie ◽  
Nan Jia ◽  
Liwen He
Keyword(s):  
Large Scale ◽  
Slip Surface ◽  
Underground Mining ◽  
Diffusion Mechanism ◽  
Combination Method ◽  
Chain Process ◽  
Maximum Shear Strain ◽  
Analysis Theory ◽  
Multiphysics Coupling ◽  
Grouting Reinforcement

The environmental conditions due to unreasonable mining in underground stopes, the slurry diffusion mechanism in the grouting reinforcement of a stope within its influence, the causes of large-scale instability collapse, and the catastrophic stope process are analyzed, and limit upper line analysis theory and numerical analysis methods are comprehensively adopted, revealing the continuous catastrophic collapse mode of large-scale underground stopes. The method of determining the stope instability collapse boundary and the slip surface within the range based on the theory of the maximum shear strain increment is proposed, and the diffusion radius and range of the grouting slurry during the reinforcement process, which considers the multifield coupling factors, are obtained. The results show that the U-shaped hidden danger area formed after the collapse of the large-scale underground stope. The influence range reaches six adjacent stopes, which are symmetrically distributed around the collapse; the mining instability is manifested as a catastrophic chain process of stress change, energy accumulation, state change, and instability collapse. The damage mode of instability collapse is a combination method of wedge collapse, circular arc rotation, triangular translation, and strip slip. According to the multiphysics coupling numerical calculation, the diffusion radius of the grouting slurry is 12 m, exhibiting an elliptical distribution. The research results can be used to comprehensively control the underground mining environment, thus effectively solving the safety problems faced by tunnel or roadway excavations above the goaf.

Local stability of concrete arch bridge based on Ritz method

2021 ◽  
pp. 1-16
Author(s):  
Jiansheng Tong ◽  
Zhengyuan Lin ◽  
Qian Zhou
Keyword(s):  
Ritz Method ◽  
Local Buckling ◽  
New Method ◽  
Radius Of Gyration ◽  
Limit Values ◽  
Arch Bridge ◽  
Finite Element Software ◽  
Equivalent Strut ◽  
Thin Walled ◽  
Arch Bridges

In order to minimize the self-weight and prevent local buckling failure of thin-walled box concrete arch bridges at the same time, the limit values of width-thickness ratios are deduced based on Ritz method and equivalent strut theory of arch bridge. A new method of determining sectional forms based on the limit values of width-thickness ratios is put forward. Based on Mupeng bridge, the theoretical results are verified by finite element software ANSYS. Results show that the limits of width-thickness ratios are related to concrete grade, equivalent calculation length and radius of gyration, the allowable minimum thickness of Mupeng bridge is 15 cm to avoid local buckling. The limit values of width-thickness ratios deduced in this paper are reasonable and this new method of determining sectional forms is simple and rational to apply in engineering. A scientific engineering calculation method on arch ring design is put forward and it can provide a theoretical basis for the design of thin-walled box concrete arch bridges constructed by cantilever pouring.

Study on the Grouting Reinforcement and Stability of a Tailings Initial Dam

2012 ◽  
Vol 602-604 ◽  
pp. 1570-1573
Author(s):  
Guang Jin Wang ◽  
Xiang Yun Kong ◽  
Qiang Liang ◽  
Yue Tong Si
Keyword(s):  
Poor Quality ◽  
Disaster Prevention ◽  
Prevention Measures ◽  
Reservoir Water ◽  
Reservoir Water Level ◽  
Research Results ◽  
Grouting Pressure ◽  
The Poor ◽  
Grouting Reinforcement ◽  
Dam Stability

The safety operation of tailings initial dam is the necessary conditions to ensure that the tailings dam is steady. In view of the poor construction quality and the appearing of jet shape seepage with the tailings leak in a tailings initial dam, the thesis analyzed the dam composite of tailings initial dam, the study of dam stability was carried out in the different working conditions and the disaster prevention measures was discussed. The research results indicated that the cementation was better and the strength of rock-soil body was higher in the upper dam body of tailings initial dam. However, the gravel cementation was weaker and strength of rock mass was relatively lower in the bottom dam body of that. Based on the poor quality of construction and penetrating seepage with the tailings initial dam, it should be feasible to adopt the grouting reinforcement way so as to reinforce the tailings initial dam. But the grouting pressure should be not more than 0.2 MPa. It will rely on increasing the dam self-respect and decreasing reservoir water level in the grouting process to reduce the risk of landslide. The research results can provide the theory basis on the disaster prevention and control of the tailings initial dam.

scholarly journals Research on Disaster-Control Method of Metro Station in Soft Fluid-Plastic Stratum

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Wang Hongbo ◽  
Qingsong Zhang ◽  
Liu Rentai ◽  
Peng Jiang ◽  
Yankai Liu
Keyword(s):  
Control Method ◽  
Water Inrush ◽  
Field Tests ◽  
Geological Condition ◽  
Foundation Pit ◽  
Metro Station ◽  
Grouting Pressure ◽  
Behavioral Mechanism ◽  
Grouting Reinforcement ◽  
Inrush Water

Soft and broken ground is a common geological condition for subway pit water damage. The complex hydrogeological environment is the main cause of frequent disasters. It relied on the inrush water project of the soft fluid-plastic stratum in the pit of the Shang Yuanmen station in Nanjing. And based on the geological data and the actual site of the project, the station was evaluated for hazards and analysis of major and difficult points. Combined with a variety of geophysical exploration methods, the source of water in the foundation pit and the key areas for pulp reinforcement was obtained. Based on field tests and indoor tests of grouting reinforcement, the parameters before and after grouting reinforcement were analyzed. The effect of material proportioning and grouting pressure on the parameters of stratum reinforcement was studied. It revealed the effect of the behavioral mechanism of material properties and grouting pressure on different mechanical indexes. It creatively proposes a localized controlled grouting process and uses COMSOL modeling to explain its reinforcement mechanism. In addition, foundation pits applied a full set of monitoring system. Finally, a complete set of comprehensive control methods were formed for water inrush in soft fluid-plastic stratum of complex urban strata. Then, the methods are implemented at the project site. Practice has proved that this method successfully seals the inrush water and reinforces foundation pits while ensuring the safety of foundation pits and surrounding construction pipelines. It is hoped that this method can be used as a reference for similar projects.

Development of an Accurate Analysis Method for Predicting Axle Hypoid Gear System Deflection

2015 ◽  
Author(s):  
Qinglong Ma ◽  
Hai Xu
Keyword(s):  
Test Procedure ◽  
New Method ◽  
Analysis Tool ◽  
Contact Pattern ◽  
Hypoid Gear ◽  
Accurate Analysis ◽  
Gear Design ◽  
Finite Element Software ◽  
Testing Method ◽  
Trade Offs

Axle hypoid gear design needs axle system deformation data at mesh point under load to evaluate the contact pattern, contact pressure and bending stress of the gear pair. The system deformation data or gear deflection (GD), can be obtained through a standard test procedure defined several decades ago. The testing method has not been improved for data acquisition efficiency and reliability since then. Fundamentally it contains trade-offs that make contact pattern correlation difficult. It also cannot meet urgent axle development timing pressures and cost reduction requirements. Analysis methods have been developed in recent years to replace the testing method of GD calculation. However, published modeling methods have their own limitations, and still do not correlate well loaded contact pattern between testing and analysis. In this paper, existing approaches of GD calculation are first reviewed and compared. Then the development of a new method is outlined, which combines a general finite element software and a special gear bearing contact analysis tool in one process. The validation of the method is illustrated by comparing axle loaded contact pattern. Finally, two case studies are demonstrated. The first one shows the capability of the new method to investigate the compliance contribution of main axle components. The second one shows that during one gear rotation, GD experiences a significant variation which needs to be considered during gear design.

scholarly journals Model Test on Segmental Grouting Diffusion Process in Muddy Fault of Tunnel Engineering

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Jun Liu ◽  
Qingsong Zhang ◽  
Lianzhen Zhang ◽  
Fang Peng ◽  
Zhipeng Li ◽  
...  
Keyword(s):  
Effective Stress ◽  
Pressure Field ◽  
Three Dimensional ◽  
Injection Rate ◽  
Tunnel Engineering ◽  
Reinforcement Effect ◽  
Soil Pressure ◽  
Injection Hole ◽  
Grouting Pressure ◽  
Grouting Reinforcement

In order to realize the diffusion law of segmental grouting in muddy fault of tunnel engineering, a three-dimensional grouting diffusion simulation test has been done. Three times of grouting operation have been done for three adjacent sections in grouting pipe. Grouting pressure, injection rate, soil pressure field, and seepage pressure field have been real-time monitored in three grouting stages. The effect of segmental grouting operation on soil pressure field and effective stress field has been analyzed. Results show that previous grouting operation can affect later grouting operation. Due to previous grouting operation, the grouted stratum can be compacted and grouting diffusion will conquer greater resistance in later grouting stages. Correspondingly, grouting pressure increases and injection rate decreases in the later grouting stage. There exists a limited influence range for a single grouting operation. For every grouting stage, soil pressure and effective stress in the section which the injection hole locates in are affected effectively by grouting operation. By contrast, soil pressure and effective stress in section away from injection hole are affected relatively weakly by grouting operation. With distance to injection hole increasing, compaction degree and reinforcement effect of grouted muddy fault decay in space. Multisegmental grouting method has significant advantages over single grouting method. Ineffectively compacted area by previous grouting operation can be effectively compacted by later grouting operation from adjacent injection hole. As a result, uniformity of grouting reinforcement effect can be improved, and weakly reinforcement area can be reduced.

scholarly journals Development of Modified Grouting Material and Its Application in Roadway Repair Engineering

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Yang Yu ◽  
Zhengyuan Qin ◽  
Xiangyu Wang ◽  
Lianying Zhang ◽  
Dingchao Chen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Surrounding Rock ◽  
Engineering Practice ◽  
Mass Ratio ◽  
Control Effect ◽  
Grouting Pressure ◽  
Grouting Material ◽  
Wide Range ◽  
Grouting Reinforcement ◽  
Grouting Materials

It is very extraordinary for the success of coal mine roadway grouting with the following factors of high early strength, good fluidity, and convenient pumping, but the existing grouting materials make it difficult to achieve the above characteristics at the same time. Therefore, a modified grouting material is developed, which is composed of two kinds of dry materials A and B, which are mixed with water and in equal amounts. The physical and mechanical properties of modified grouting materials under different ratios were tested by laboratory orthogonal test, and the optimal ratio of grouting materials and additives was obtained: (1) the water-cement ratio is 0.8 : 1; (2) base material: the mass ratio of cement, fly ash, bentonite, and water is 1 : 0.3 : 0.1 : 1.44; (3) admixture: the mass ratio of water reducer C, accelerator D, and retarder E is 1.5% : 0.05% : 0.3%. The basic properties of the modified grouting materials were studied from the aspects of slurry flow state, diffusion range, and grouting parameters by using the numerical simulation method, and the reinforcement mechanism of slurry to the broken surrounding rock properties of the roadway was revealed: (1) the grouting pressure is the main factor affecting the slurry diffusion radius; (2) the mechanical properties of the roadway surrounding rock are improved, the plastic zone and deformation of surrounding rock are reduced, and the active support function of the anchor and cable is enhanced through grouting reinforcement; (3) the control effect of the roadway is improved, and the balanced bearing with anchorage structure of the roadway surrounding rock is realized through grouting reinforcement. On this basis, the modified grouting material is applied to roadway repair and reinforcement engineering practice. The field monitoring data show that the production practices were guided by roadway repair and reinforcement technology with the modified grouting material, as the core of the roadway surrounding rock control effect is good, and the modified grouting material has a wide range of application prospects.

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