scholarly journals Laboratory Model Test Research on Mechanical Characteristics of Anchor in Loess Tunnel under the Action of Pull-Out Load

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Zhongming Su ◽  
Jianxun Chen ◽  
Yanbin Luo ◽  
Xin He
Keyword(s):  
Shear Stress ◽  
Model Test ◽  
Maximum Shear Stress ◽  
Test Chamber ◽  
Deformation Mode ◽  
Surrounding Rock ◽  
Laboratory Model ◽  
Engineering Practice ◽  
Distribution Law ◽  
Pull Out

The deformation mode of loess surrounding rock of anchor under the action of pull-out load and the shear stress distribution law of loess anchor and loess interface under the condition of different lengths anchor are studied by using the laboratory self-made model test chamber and micro anchor pullout instrument. A total of three tests are carried out for the selected test anchor. Three deformation modes of loess surrounding rock under the action of pull-out load are obtained according to the test results. It is proposed that the maximum shear stress of loess anchor under the action of pull-out load appears in the section 25 times the anchor diameter from the anchor head, and the shear stress in the middle and rear part of the anchor body can only be brought into full play when the length-to-diameter ratio of the anchor body is 110 or more. Based on the displacement solution of Mindlin problem, the drawn conclusion is compared with the theoretical solution of shear stress and axial force of loess anchor under the action of pull-out load. The results compared are basically consistent, indicating that the conclusion has strong engineering practice, which can provide technical basis for the design and optimization of the system anchor in the sidewall of loess tunnel.

Laboratory Model Test Study of Tunnel Anchor

2014 ◽  
Vol 1065-1069 ◽  
pp. 333-336
Author(s):  
Bing Shen ◽  
Sai Qiong Long ◽  
Jun Chen ◽  
Yong Bing Li
Keyword(s):  
Model Test ◽  
Shear Failure ◽  
Failure Surface ◽  
Tensile Failure ◽  
Laboratory Model ◽  
Pull Out ◽  
Test Study ◽  
Cable Force ◽  
Anchor Design ◽  
Laboratory Model Test

A laboratory model test of tunnel anchor was conducted to investigate its pullout mechanism and bearing capacity. Surface and rock deformation, strain and stress were measured during the entire model test process. The results show that: under pull out load, tensile failure first occurs in top surface rock near the anchor, then shear failure occurs in anchor-rock interface and rock around the anchor. The failure surface is inverted cone from the anchor bottom. Under 50 times design cable force tunnel rock is in elastic stage, suggesting that current tunnel anchor design is quite conservative and can be further optimized.

scholarly journals Analysis of Stress Asymmetric Distribution Law of Surrounding Rock of Roadway in Inclined Coal Seam: A Case Study of Shitanjing No. 2 Coal Seam

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Xianyu Xiong ◽  
Jun Dai ◽  
Xinnian Chen
Keyword(s):  
Coal Seam ◽  
Stability Control ◽  
Surrounding Rock ◽  
Laboratory Model ◽  
Asymmetric Distribution ◽  
Stress Concentrations ◽  
Distribution Law ◽  
Left Wall ◽  
Failure Characteristics ◽  
Sharp Corners

Asymmetrical deformation and failure characteristics of the surrounding rock at the right-angled trapezoidal roadway in the Shitanjing No. 2 mining area has created great difficulties in the stability control and support of the roadway. First, numerical simulations were applied to systematically analyze the distribution rules for vertical stress, horizontal stress, and failure characteristics of the roadway. Furthermore, verifications were conducted via laboratory model tests and practical engineering application. The results show that the two walls of the roadway, the roof, and the sharp corners demonstrate obvious asymmetric stress concentrations. The peak value of stress concentration in the low side (right wall) is significantly greater than that in the high side (left wall), and the distances from high and low sides of roadway to both walls of the roadway are obviously different. The two sharp corners, which are symmetrical along the same direction of the coal seam inclination, show obvious compressive stresses, while the opposite directions show obvious tensile stress regions at both sharp corners; further, maximum values of the compressive and tensile stresses appear at the two corners of the roadway roof, and their magnitudes vary with the change in inclination and ground stress.

Study on Stability of Layered Roof Surrounding Rock Reinforced by Anchor in Rectangular Roadway

2014 ◽  
Vol 638-640 ◽  
pp. 864-869
Author(s):  
Zhong Ming Zhao ◽  
Zhi Yuan Xi
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Maximum Shear Stress ◽  
Maximum Tensile Stress ◽  
Surrounding Rock ◽  
Point Location ◽  
Anchor Cable ◽  
Mechanics Of Materials ◽  
Before And After ◽  
Dangerous Point

Under the assumptions of plane strain, vertical normal stress and shear stress distribution in surrounding rock of rectangular tunnels before and after installing anchor cable are studied. And according to the mechanics of materials, the formula of stress distribution in the roof is corrected. According to the corrected formula of the stress distribution, the dangerous points are found. And the dangerous point location does not change before and after installing anchor cable. It still locates in the middle and ends of roadway roof. Just the dangerous stress value decreases after installing anchor cable. There are the maximum tensile stress in the midpoint roof and the maximum shear stress on both ends of the roof.

scholarly journals Research on the Deformation Mechanism of Mining Roadway Stratiform Surrounding Rock with Nonuniform Stress Field

2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Yongxin Sun
Keyword(s):  
Shear Stress ◽  
Plastic Zone ◽  
Maximum Shear Stress ◽  
Pressure Coefficient ◽  
High Stress ◽  
Surrounding Rock ◽  
Rock Joints ◽  
Instability Criterion ◽  
Structural Plane ◽  
Structure Plane

Aiming at the failure problems of mining roadway stratiform surrounding rock influenced by asymmetrical high stress, firstly, the rock instability conditions of different structural plane angles were summarized based on the mechanical model of rock joints and instability criterion. Secondly, stresses, plastic zone, and displacement of surrounding rock with different structural plane angles were calculated and analyzed with the theoretical calculation method or numerical simulation method, respectively. The distribution characteristics of plastic zone of surrounding rock under different influence factors are further studied, and the results show that the lateral pressure coefficient can change the size and shape of plastic zone at the same time. The damage mechanism was analyzed through the above study. Research studies show that the shear and tension failure area of plastic zone were directly determined by the maximum shear stress and the minimum principal stress. The effect of structure planes on stress has two sides, one to destroy the continuity and the other to strengthen discreteness and laddering nature. When the angle between maximum shear stress and structure plane increases, the extended mode and distribution pattern of plastic zone change substantially as well. The #15 haulage roadway is taken as engineering background, and the above research’s results are verified by the comprehensive analysis. The research results can enrich the butterfly plastic zone theory and provide the basis for roadway supporting design.

scholarly journals Development and Application of Model Test System for Reconstruction and Expansion of Existing Shallow Single-Hole Tunnel into Twin-Arch Tunnel

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Yanling Jia ◽  
Aohui Ouyang ◽  
Siyu Wang ◽  
Xing Liang ◽  
Bin Wang ◽  
...  
Keyword(s):  
Model Test ◽  
Ground Surface ◽  
Test System ◽  
Surrounding Rock ◽  
Surface Settlement ◽  
Laboratory Model ◽  
Internal Stresses ◽  
Tunnel Excavation ◽  
Single Hole ◽  
Ground Surface Settlement

In this study, we developed a tunnel excavation model test system to investigate the deformation and mechanical response of the surrounding rocks and tunnel structure during the reconstruction and expansion of an existing shallow single-hole tunnel into a twin-arch tunnel. A model test was conducted to study the variation in the ground surface settlement characteristics, surrounding rock pressure, and internal stresses of the supporting structure and midwall during the construction process. The influence of the excavation distance on displacements and structural stress between the faces of the left and right tunnels was analysed using numerical software. A comparison between the model test results and the monitoring and measurement construction results revealed a fairly consistent ground surface settlement, indicating that the system is stable and reliable and can be widely applied to laboratory model test research on tunnel excavation. Results show that the excavation of the first tunnel had a significant effect on the stability of the surrounding rock within the distance of a single-tunnel span behind the tunnel face. When the excavation distance between the two tunnels exceeded twice the length of the single-tunnel span, its effect on the stresses and deformation of the reconstructed twin-arch tunnel was negligible.

scholarly journals Floor Heave Mechanism and Anti-Slide Piles Control Technology in Deep and Large-Span Chamber

2021 ◽  
Vol 11 (10) ◽  
pp. 4576
Author(s):  
Jian Shi ◽  
Desen Kong
Keyword(s):  
Model Test ◽  
Shear Failure ◽  
Deformation Mode ◽  
Control Technology ◽  
Plastic Limit ◽  
Large Span ◽  
Similarity Model ◽  
Floor Heave ◽  
Plastic Limit Analysis ◽  
Local Shear

Based on plastic limit analysis, the deformation and fracture mechanism of the floor in the large-span chambers of deep mines are discussed and a similarity model test is carried out to verify the reliability of the theoretical analysis. The results show that the local shear failure first appears below the loading area and develops to the middle part of the test model with the increase in load; when the local shear failure develops to form a continuous sliding surface, continuous plastic flow deformation occurs; the distribution of the plastic zone and the deformation mode obtained from the similarity model test are basically consistent with the Hill-like deformation mode derived from plastic limit analysis. A control technology with anti-slide piles is proposed in order to deal with floor heave in large-span chambers on the basis of previous work. An approach for determining the supporting parameters of anti-slide piles is deduced. To deal with the floor heave in the −1100 level gangue winch room of the Huafeng Coal Mine, a comprehensive reinforcement scheme with anti-slide piles composed of discarded rails and anti-floating anchors is introduced for the floor heave control of the chambers. Site monitoring results show that the scheme not only effectively restrains the development of floor heave, but also ensures the long-term stability of the chamber floor.

scholarly journals Studying the performance of fully encapsulated rock bolts with modified structural elements

2021 ◽  
Author(s):  
Jianhang Chen ◽  
Hongbao Zhao ◽  
Fulian He ◽  
Junwen Zhang ◽  
Kangming Tao
Keyword(s):  
Shear Stress ◽  
Load Transfer ◽  
Maximum Shear Stress ◽  
Coupling Model ◽  
Numerical Approach ◽  
Rock Bolt ◽  
Structural Elements ◽  
Rock Bolts ◽  
Two Stage ◽  
Bolt Diameter

AbstractNumerical simulation is a useful tool in investigating the loading performance of rock bolts. The cable structural elements (cableSELs) in FLAC3D are commonly adopted to simulate rock bolts to solve geotechnical issues. In this study, the bonding performance of the interface between the rock bolt and the grout material was simulated with a two-stage shearing coupling model. Furthermore, the FISH language was used to incorporate this two-stage shear coupling model into FLAC3D to modify the current cableSELs. Comparison was performed between numerical and experimental results to confirm that the numerical approach can properly simulate the loading performance of rock bolts. Based on the modified cableSELs, the influence of the bolt diameter on the performance of rock bolts and the shear stress propagation along the interface between the bolt and the grout were studied. The simulation results indicated that the load transfer capacity of rock bolts rose with the rock bolt diameter apparently. With the bolt diameter increasing, the performance of the rock bolting system was likely to change from the ductile behaviour to the brittle behaviour. Moreover, after the rock bolt was loaded, the position where the maximum shear stress occurred was variable. Specifically, with the continuous loading, it shifted from the rock bolt loaded end to the other end.

Flow and Thermal Fields in a Pendant Droplet Moving on Lyophobic Surface

2010 ◽  
Author(s):  
Basant Singh Sikarwar ◽  
K. Muralidhar ◽  
Sameer Khandekar
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Reynolds Number ◽  
Shear Stress ◽  
Heat Transfer Coefficient ◽  
Wall Shear Stress ◽  
Transfer Coefficient ◽  
Maximum Shear Stress ◽  
Computational Domain ◽  
Wall Shear

Clusters of liquid drops growing and moving on physically or chemically textured lyophobic surfaces are encountered in drop-wise mode of vapor condensation. As opposed to film-wise condensation, drops permit a large heat transfer coefficient and are hence attractive. However, the temporal sustainability of drop formation on a surface is a challenging task, primarily because the sliding drops eventually leach away the lyophobicity promoter layer. Assuming that there is no chemical reaction between the promoter and the condensing liquid, the wall shear stress (viscous resistance) is the prime parameter for controlling physical leaching. The dynamic shape of individual droplets, as they form and roll/slide on such surfaces, determines the effective shear interaction at the wall. Given a shear stress distribution of an individual droplet, the net effect of droplet ensemble can be determined using the time averaged population density during condensation. In this paper, we solve the Navier-Stokes and the energy equation in three-dimensions on an unstructured tetrahedral grid representing the computational domain corresponding to an isolated pendant droplet sliding on a lyophobic substrate. We correlate the droplet Reynolds number (Re = 10–500, based on droplet hydraulic diameter), contact angle and shape of droplet with wall shear stress and heat transfer coefficient. The simulations presented here are for Prandtl Number (Pr) = 5.8. We see that, both Poiseuille number (Po) and Nusselt number (Nu), increase with increasing the droplet Reynolds number. The maximum shear stress as well as heat transfer occurs at the droplet corners. For a given droplet volume, increasing contact angle decreases the transport coefficients.

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