Study on creep properties and a viscoelastic–plastic constitutive model of slate considering freeze–thaw damage and joint effect

In order to study the failure mechanism and assess the stability of the inlet slope of the outlet structure of Lianghekou Hydropower station, the strength reduction method considering the ubiquitous joint model is proposed. Firstly, two‐dimension numerical models are built to investigate the influence of the dilation angle of ubiquitous joints, mesh discretization, and solution domain size on the slope stability. It is found that the factor of safety is insensitive to the dilation angle of ubiquitous joints and the solution domain size but sensitive to the mesh discretization when the number of elements less than a certain threshold. Then, a complex three‐dimension numerical model is built to assess the stability of the inlet slope of the outlet structure of Lianghekou Hydropower station. During the strength reduction procedure, the progressive failure process and the final failure surface of the slope are obtained. Furthermore, the comparison of factors of safety obtained from strength reduction method and analytical solutions indicates that the effect of vertical side boundaries plays an important role in the stability of jointed rock slope, and the cohesive force is the main contribution to the resistant force of vertical side boundaries.

Groundwater level plays an important role in triggering landslides. In this paper, Distinct Element Method is used to investigate the impact of groundwater table fluctuation on the stability of jointed rock slopes. For this purpose, 110 cases including different number of joint sets, joint friction angles, joint spacings, and joint angles are considered and the influence of changing groundwater level on the stability of a jointed rock slope is investigated through a series of parametric studies. This study shows that the factor of safety for slopes can decrease significantly with increasing the groundwater level, and the impact is more significant on slopes with steeper joints. Furthermore, as the spacing of the joints decreases, the impact decreases. However, as the joint spacing increases, the groundwater table should rise to a higher elevation to be able to have an impact. Moreover, the impact on the factor of safety is similar for different joint friction angles when the groundwater level elevation is high. This study provides a better understanding of the impact of groundwater table fluctuation on the stability of jointed rock slopes.

A statistics-based discrete element modeling method coupled with the strength reduction method for the stability analysis of jointed rock slopes

Seismic stability of slopes has been traditionally analyzed with vertically propagated earthquake waves. However, for rock slopes, the earthquake waves might approach the outcrop still with a evidently oblique direction. To investigate the impact of obliquely incident earthquake excitations, the input method for SV and P waves with arbitrary incident angles is conducted, respectively, by adopting the equivalent nodal force method together with a viscous-spring boundary. Then, the input method is introduced within the framework of ABAQUS software and verified by a numerical example. Both SV and P waves input are considered herein for a 2D jointed rock slope. For the jointed rock mass, the jointed material model in ABAQUS software is employed to simulate its behavior as a continuum. Results of the study show that the earthquake incident angles have significance on the seismic stability of jointed rock slopes. The larger the incident angle, the greater the risk of slope instability. Furthermore, the stability of the jointed rock slopes also is affected by wave types of earthquakes heavily. P waves induce weaker responses and SV waves are shown to be more critical.

A method for seismic stability analysis of jointed rock slopes using Barton-Bandis failure criterion

The random distribution characteristic of discontinuities is always rarely considered when analysing the stability of jointed rock slope. Joint network simulation can simulate the random distribution of discontinuities. So this method is applied to analysing the stability of jointed rock slopes. Firstly, the joint network simulation method is used to establish the joint network model of the slope. Then the result is combined with shear strength reduction method to calculate the safety factor of the slope. Subsequently, many joint network simulations and their relative safety factors are used to analyse the reliability of the slope. The result of a real project shows the following. (1)The stability of the rock slope is mainly controlled by the quantity and combination relationship of discontinuities. The more is the discontinuities' quantity and persistence, the lower is the slope's safety factor. (2)The average safety factor of the slope is 3.06 and its probability of failure is 5%,which indicate the good reliability of the slope. This result is in accordance with the real condition of the slope. The analysis method in this paper mainly considers the random distribution of discontinuities, and it presents a new way to analyse the stability of jointed rock slope.

The stability of rock slope is often controlled by the existing discontinuous surfaces, such as discrete fractures, which are ubiquitously distributing in a geological medium. In contrast with the traditional approaches used in soil slope with a continuous assumption, the simulation methods of jointed rock slope are different from that of in soil slope. This paper presents a study on jointed rock slope stability using the proposed discontinuous approach, which considers the effects of discrete fractures. Comparing with traditional methods to model fractures in an implicit way, the presented approach provides a method to simulate fractures in an explicit way, where grids between rock matrix and fractures are independent. To complete geometric components generation and mesh partition for the model, the corresponding algorithms were devised. To evaluate the stability state of rock slope quantitatively, the strength reduction method was integrated into our analysis framework. A benchmark example was used to verify the validation of the approach. A jointed rock slope, which contains natural fractures, was selected as a case study and was simulated regarding the workflow of our framework. It was set up in the light of the geological condition of the site. Slope stability was evaluated under different loading conditions with various fracture patterns. Numerical results show that fractures have significant contributions to slope stability, and different fracture patterns would lead to different shapes of the slip surface. The devised method has the ability to calculate a non-circular slip surface, which is different from a circular slip surface obtained by classical methods.

Shear creep characteristics and creep constitutive model of bolted rock joints

Partial coefficient finite element method is a new method of analyzing the stability of jointed rock slope. Partial coefficient Finite element analysis of joints rock slope stability, the calculation accuracy will be influenced by many factors, Such as the yield criterion, the mechanical parameters of rock mass, the computing grid, etc. In this paper, combined with example analyzed the impact of these factors on the partial coefficient method calculation accuracy. Considering material partial coefficients of slope’s weak layer, then, the weak layer is reduced by the strength reduction method. Analysis results show that: Using partial coefficient method analysis of stability of rock slope, under the associated flow rule, should choose Mohr-Coulomb inscribed circle criterion. In addition, when using Mohr - Coulomb inscribed circle criterion, the modulus of elasticity and poison’s ratio on the calculation results can be ignored. And with a few elements ideal result can be deduced.

Discontinuities influenced the stability of jointed rock slopes are taken as the main subject of investigation, network simulation of discontinuities in the rock mass was produced by using Monte-Carlo method. The establishment of jointed element model to carry out that the network model of discontinuities was applied to the numerical one, which made it feasible to consider the influence of discontinuities in course of analyses of the finite element method when evaluating the stability of jointed rock slopes. Finally, the method was preliminarily applied with real project of artificial slope for BaiLong nuclear power plant, it is proved that it is feasible to expand for engineering applications.

Reliability analysis of rock slopes considering the uncertainty of joint spatial distributions

The existence of fissures can reduce the stability of open pit slope. Meanwhile, the disturbing force that is generated by large equipment and blasting also has significant influence on the stability of the slope. In view of this, to study the deformation law of open pit slope under the action of disturbing force of fractured rock mass, this paper focus on the influence of various fracture angle, trace and joint spacing on the deformation law and safety factor of the open pit slope by means of physical mechanical experiment and discrete element calculation analysis. The research results reveal that different fracture distribution form can result to different deformation and failure character, moreover, the variation of safety coefficient is also greater difference. Furthermore, it can be obtained that the further development tendency and transfixion law of the slope rock mass under the action of external force, which can provide evidence for the further research on the slope stability parameter selection of fractured rock mass in open pit.

Study on mechanical properties and failure behavior of jointed gypsum rock under uniaxial compression using AE and DIC techniques

Finite element method is used to compute the factor of safety of jointed rock slope. The stability of jointed rock slope is simulated by using shear strength reduction approach. Mohr-Coulomb fracture criterion is used to evaluate the sticking or sliding state of jointed rock mass. The distribution of plastic zone at collapse state is determined. Numerical computational results show that the proposed procedure is effective to evaluate stability of jointed rock slope.

Effect of shrinkage-induced initial damage on the frost resistance of concrete in cold regions