scholarly journals Numerical analysis of the precursory information of slope instability process with constant resistance bolt

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Feng Chen ◽  
Xue-bin Wang ◽  
Yan-hong Du ◽  
Chun-an Tang
Keyword(s):  
Principal Stress ◽  
Shear Failure ◽  
Lateral Displacement ◽  
Numerical Test ◽  
Significant Rise ◽  
Slope Instability ◽  
Practical Significance ◽  
Landslide Monitoring ◽  
Monitoring Method ◽  
Constant Resistance

AbstractThe instability of slope has already threatened life and property safety of the people, and improving the monitoring method of slope stability has important theoretical and practical significance for disaster prevention and reduction. According to the idea of “Newton force sudden drop and catastrophic occurrence” proposed by M.C. He in the landslide monitoring, a numerical model with constant resistance bolt has been established. Through numerical simulation research, it is found that the maximum principal stress, minimum principal stress and shear stress of the intersection point P of landslide surface and constant resistance bolt are sudden growth and sudden decrease, the vertical displacement and lateral displacement of this point P appear rise and fall before three kinds of stress. When loading to the next step of the step where three stress have reduced to a minimum value the slope is unstable and destroyed. At this time, the constant resistance bolt has undergone larger plastic deformation and damaged. Finally, comparing the stress curves and the acoustic emission (AE) curves, it can be seen that stress decreases from the maximum value and the AE curves begin to show a significant rise, the two curves display opposite law. It can be seen from the AE diagram that the failure mode of the slope is a combined tension and shear failure. The numerical test results provide a new idea for real-time monitoring and forecasting of slope.

Numerical modelling of the crack-pore interaction and damage evolution behaviour of rocklike materials with pre-existing cracks and pores

2020 ◽  
pp. 105678952098387
Author(s):  
PLP Wasantha ◽  
D Bing ◽  
SQ Yang ◽  
T Xu
Keyword(s):  
Principal Stress ◽  
Damage Evolution ◽  
Shear Failure ◽  
Mechanical Response ◽  
Distribution Patterns ◽  
Stress Distributions ◽  
Compressive Stresses ◽  
Major Principal Stress ◽  
The Right ◽  
Macroscopic Failure

The combined effect of pre-existing cracks and pores on the damage evolution behaviour and mechanical properties of rocklike materials under uniaxial compression was numerically studied. Simulations of cracks and pores alone showed that increasing crack length and pore diameter decrease uniaxial compressive strength (UCS) and elastic modulus. Subsequent simulations considered two types of combinations of pre-existing cracks and pores – two cracks either side of a centric pore, and two pores either side of a centric crack – and the distance between cracks and pores was changed. In the case of two cracks at either side of the pore, UCS increased only slightly when the distance between the cracks and pore was increased. This was attributed to the more profound effect of the presence of the pore on UCS, and was confirmed by the progressive crack development characteristics and the major principal stress distribution patterns, which showed that the cracks initiated from the tips of the two pre-existing cracks made little or no contribution to the ultimate macroscopic failure. In contrast, models with two pores at either side of a centric crack showed a marked dependency of UCS on the distance between the pores and the crack. Cracks propagating from pre-existing pores made a greater contribution to the ultimate macroscopic failure when the pores were close to the centric crack and the effect gradually diminished with increasing space between pre-existing pores and the centric crack. Major principal stress distributions showed an asymmetric mobilisation of compressive stresses at the right and left sides of the two pores, favouring macroscopic shear failure when they were close to the centric crack which had led to a lower UCS. Overall, this study presents some critical insights into crack-pore interaction behaviour and the resulting mechanical response of rocklike materials to assist with the design of rock structures.

Simulation of Numerical Test of Concrete Microscopic Structure by Second-Order Manifold Method

2013 ◽  
Vol 477-478 ◽  
pp. 968-971 ◽  
Author(s):  
Yan Zhao ◽  
Guo Xin Zhang ◽  
Hai Feng Li
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Fracture Process ◽  
Shear Failure ◽  
Numerical Test ◽  
Aggregate Model ◽  
The Monte Carlo Method ◽  
Random Aggregate ◽  
Random Aggregate Model ◽  
Numerical Manifold

To simulate the numerical test of concrete, the random aggregate model according to the Monte Carlo method and Fuller Graded Formula is carried out based on the assumption that the concrete is a multi-phases composite material composed of matrix. By adding the function of tracing the propagation of cracks,the Numerical Manifold Method proposed by Shi Genhua is developed which can simulate both the discontinuity of block system and the tensile or shear failure of intact block. The random aggregate model according to the Monte Carlo method and Fuller Graded Formula is carried out, and the concrete fracture process is simulated by the NMM. The strength and failure pattern are in good agreement with the experimental data, which shows that the method put forward and the program developed in this paper can effectively simulate the fracture process of concrete composed of multi-cracks.

Study on Mechanism of Slope Instability with Weak Interlayer

2011 ◽  
Vol 71-78 ◽  
pp. 3615-3618 ◽  
Author(s):  
Yun Fei Wang ◽  
Fu Ping Zhong ◽  
Huai Bao Chu ◽  
Li Ping Wang
Keyword(s):  
Stress Field ◽  
Failure Mechanism ◽  
Shear Failure ◽  
Slope Instability ◽  
Tensile Failure ◽  
Cyclic Process ◽  
Research Subject ◽  
Geological Conditions ◽  
Weak Interlayer ◽  
Mass Rock

In the process of the highway building, especially in mountain region the some complex geological conditions often appears. In this paper, using the slope of highway with weak interlayer as the research subject, systematically analyzing the stress field and plastic field during the excavation of the slope, obtained the failure mechanism of the slope with weak interlayer, which is a cyclic process that weak interlayer shear failure led to the tensile failure of its upper mass rock. It has extraordinarily important guiding significance for the protection and reinforcement of similar slope.

scholarly journals LANDSLIDE MONITORING IN A BUILT-UP AREA

2021 ◽  
Vol 29 ◽  
pp. 6-10
Author(s):  
Petr Černoch ◽  
Jiří Koštál ◽  
Adam Podojil
Keyword(s):  
Measured Data ◽  
Significant Rise ◽  
Landslide Monitoring ◽  
Stability Calculation ◽  
Groundwater Levels ◽  
Geotechnical Monitoring

The article deals with the evaluation and comparison of measured data from geotechnical monitoring of a gabion wall and an adjacent slope. In 2015, new anomalous phenomena related to deformations and a shift in the area of previously activated landslide were recorded on some monitoring elements in the area of the gabion wall. Measurements carried out in previous stages had revealed the re activation of landslides, probably due to a significant rise in groundwater levels, whose fluctuation has been up to 3 m. A proper evaluation of the obtained results cannot be quantified without the determination of warning status or without a stability calculation. Only the trend and magnitude of the measured values can be evaluated.

scholarly journals The suction,yield and strength characteristics of unsaturated intact loess based on true tri-axial tests

2019 ◽  
Vol 7 (3) ◽  
Author(s):  
Jinjin Fang
Keyword(s):  
Principal Stress ◽  
Stress Ratio ◽  
Shear Failure ◽  
Confining Pressure ◽  
Intermediate Principal Stress ◽  
True Triaxial ◽  
Yield Stress Increase ◽  
Isotropic Consolidation ◽  
The Relationship ◽  
Intact Loess

To simulate the failure of loess under undrained condition in the actual engineering,a series of isotropic consolidation and shear tests with different intermediate principal stress ratio b under constant water content were performed on intact loess with various initial suctions using the true tri-axial apparatus for unsaturated soil. The relationship between the saturations and initial suctions,the characteristics of yield,suction and strength of unsaturated intact loess were studied. The results show that the initial suctions and the suctions after the isotropic consolidation decrease with the increase of saturations. The suctions increase with the increase of the intermediate principal stress ratio b at the true triaxial shear failure. The net mean yield stress increase with the increase of the initial suction. The yield suction is a constant,but not always equal to the maximum suction that the soil specimen experienced in the history. The strength of soil increase with the increase of the net confining pressure,initial suction and the intermediate principal stress ratio b.

scholarly journals A Simulation Study of Loess Slope Instability and Damage Under Intensive Seismic Vibration

2021 ◽  
Author(s):  
chaoyu chang ◽  
Jingshan Bo ◽  
WenHao Qi ◽  
feng qiao ◽  
da peng
Keyword(s):  
Principal Stress ◽  
Model Building ◽  
Horizontal Displacement ◽  
Field Investigation ◽  
Slope Instability ◽  
Particle Flow Code ◽  
Seismic Vibration ◽  
Loess Slope ◽  
Damage Process ◽  
The Difference

Abstract The instability and damage of the loess slope under intensive seismic vibration can be a complicated process, involving in sliding, horizontal displacement and rotation, which makes the particle flow code a suitable theory to simulate the instability and damage of the loess slope. In this study, based on both field investigation and indoor experiments, PFC2D program was adopted to simulate the instability and damage process of the loess slope landslide under intensive seismic vibration through the detailed identification of relevant parameters, model building and dynamic input. The analysis has revealed three main findings. Firstly, the volley surface structure dominated in the slope tends to magnify the vibration, resulting in intensive vibration of the soil body on the slide surface and an increased high frequency components of Fourier spectrum. Secondly, under the dynamic forces, the slope first accumulates and damages in the lower part, forming a shear outlet. Under the pulling of the lower particles, the difference between the first principal stress and the third principal stress gradually increases, destroying the inherent cohesive contact between the particles, leading to the instability damage. Thirdly, the upper soil body experiences tensile damage, forming a through slide face which causes the instability damage of the whole slope. The sliding face demonstrates in a oval shape, with a deeper arch as the vibration lasts longer.

The Effect of Ground Displacement and Stress Relief on Pipeline Behaviour: A Case Study

2018 ◽  
Author(s):  
Hamid Karimian ◽  
Chris Campbell ◽  
Chris Blackwell ◽  
Colin Dooley ◽  
Pete Barlow
Keyword(s):  
Lateral Displacement ◽  
Stress Relief ◽  
Slope Instability ◽  
Ground Movement ◽  
Ground Displacement ◽  
Ground Movements ◽  
Before And After ◽  
Translational Slide ◽  
Lower Slope ◽  
Upper Slope

The Wapiti River South Slope is located 25 km southwest of Grande Prairie, AB. The slope is 500 m long and consists of a steep lower slope and a shallower upper slope, both of which are located within a landslide complex with ground movements of varying magnitudes and depths. The Alliance Pipelines Ltd. (Alliance) NPS 42 Mainline (the pipeline) was installed in the winter of 2000 using conventional trenching techniques at an angle of approximately 8° to the slope fall line. Evidence of slope instability was observed in the slope since the first ground inspection in 2007. Review of the available geotechnical data indicates two different slide mechanisms. In the lower slope, there is a shallow translational slide within a colluvium layer that is draped over a stable bedrock formation. In the upper slope, there is a deep-seated translational slide within glaciolacustrine and glacial till deposits that are underlain by pre-glacial fluvial deposits. Both the upper and lower slope landslide mechanisms have been confirmed to be active in the past decade. Large ground displacements in the order of several meters between 2012 and 2014 in the lower slope led to a partial stress relief and subsequent slope mitigation measures in the spring and summer of 2014, which significantly reduced the rate of ground movement in the lower slope. Surveying of the pipeline before and after stress relief indicated an increase in lateral pipeline deformation (in the direction of ground movement) following the stress relief. This observation was counter-intuitive and raised questions regarding the effectiveness of partial stress relief to reduce stresses and strains associated with ground movements. Finite element analysis (FEA) was conducted in 2017 to aid in assessing the condition of the pipeline after being subject to the aforementioned activities, and subsequent ground displacement from July 2014 to December 2016. This paper presents the assumptions and results of the FEA model and discusses the effect of large ground displacement, subsequent stress relief and continued ground displacement on pipeline behaviour. The results and findings of the FEA reasonably match the observed pipeline behaviour before and after stress relief. The FEA results showed that while the lateral displacement of the pipeline that was caused by ground movement actually increased following the removal of the soil loading, the maximum pipeline strain was reduced in the excavated portion. The results also indicated that ground displacement in the upper slope following the stress relief had minimal effect on pipe stresses and strains in the lower slope.

scholarly journals Study on stability of filling wall under lateral large-span composite hinge fracture of hard critical block

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042110216
Author(s):  
Chenghai Li ◽  
Yajie Liu ◽  
Jianbiao Bai ◽  
Qing Ge
Keyword(s):  
Field Test ◽  
Shear Failure ◽  
Lateral Displacement ◽  
Axial Stress ◽  
Tensile Failure ◽  
Shear Cracks ◽  
Large Span ◽  
The Stability ◽  
Number Of Segments ◽  
Hinge Fracture

There is still a lack of mature researches on the stability mechanism, influencing factors and control technology of the gob-side filling wall, and systematic researches on the cracking forms and characteristics of the stope roof and the stability of the filling wall are rather insufficient. This paper is aimed at investigating the deformation law of the filling wall under the large-span composite hinge fracture of the hard critical block and solving the difficulty that the large-span critical block lateral fracture poses to gob-side entry retaining. Research methods such as theoretical calculation, mechanical analysis, numerical simulation and field test were adopted comprehensively in this study. When the large-span critical block B is divided into two or three parts, its force on the immediate roof decreases with the increase in the number of segments. Meanwhile, as the number of segments grows, the displacement and axial stress of the filling wall both decrease gradually; the tensile failure weakens relatively, while the shear failure changes slightly. Moreover, both the number of shear cracks and the number of tensile cracks in the filling wall are positively correlated with the strain. When the critical block divided into four parts, the amount of lateral displacement is about 190 mm, and the axial displacement reaches the minimum (about 235 mm). The stability of the filling wall along the gob-side entry is closely related to the lateral fracture span of the stope roof. Under the lateral fracture of the hard critical block, a smaller span of the lateral fracture of the critical block corresponds to a smaller force on the filling wall and a weaker damage to the filling wall. The field test result verifies that cleaving the large-span critical block into smaller segments is conducive to reducing surrounding rock and filling wall deformation.

scholarly journals Experimental Study of the Shear Performance of Scrap Tire-Granular Material Composite Columns

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Fengchi Wang ◽  
Xiaomei Nie ◽  
Hanyu Zhao ◽  
Haiming Hu
Keyword(s):  
Shear Strength ◽  
Shear Failure ◽  
Lateral Displacement ◽  
Vertical Force ◽  
Scrap Tire ◽  
Stress Strain ◽  
Composite Columns ◽  
Failure Patterns ◽  
Loading Mode ◽  
Shear Performance

Scrap tires filled with granular materials can be used for geotechnical engineering. However, when subjected to earthquakes and other conditions, shear failure occurs between the tires. In this paper, eight groups of tire-sand composite columns are prepared and tested under shear strength tests. Different vertical forces, sand densities, and loading modes are considered to investigate the shear performance. The failure patterns, load-displacement curves, and stress-strain curves are observed. The results show that the shear failure of composite undergoes three typical stages: overall flexural lateral displacement, transverse compression, and relative interfacial slip. Under monotonic loading, the restriction of the transverse deformation of the composite column is enhanced with increasing vertical force. The overall antidisturbance ability of the composite is enhanced with increasing sand density. The cyclic loading mode can improve the lateral stiffness of the tire-sand composite. The relative motion between the tire-sand interfaces has two forms: elastic creep and interface sliding. Under the hoop effect of the tire, the pores between the particles produce a pseudocohesive force, which causes the shear strength of the tire-sand composite to be higher than that of common sand. A formula is obtained to describe the stress-strain variations in the composite under different vertical forces.

Slope Stability Analysis with Finite Element Method

2012 ◽  
Vol 538-541 ◽  
pp. 819-822 ◽  
Author(s):  
Jie Qun Liu ◽  
Jin Long Liu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stability Analysis ◽  
Plastic Strain ◽  
Slope Stability ◽  
Plastic Zone ◽  
Principal Stress ◽  
Lateral Displacement ◽  
Slope Reinforcement ◽  
Element Method

A slope is studied with limiting equilibrium method and finite element method comparatively. It is found that the results of the two methods are almost the same. The distribution of principal stress, maximal plastic strain, plastic zone, lateral displacement, vertical settlement and incremental of displacement can be investigated by FEM effectively, which make it easy to expediently choose the method of slope reinforcement and the position of strengthening.

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