Ubiquitous Joint Model Research Articles

Back-Analysis of Parameters of Jointed Surrounding Rock of Metro Station Based on Random Forest Algorithm Optimized by Cuckoo Search Algorithm

The efficiency and accuracy in determining mechanical parameters of joint of rock mass have significant influences on the safety of construction. In this paper, a new back-analysis method of joint parameters of the ubiquitous-joint model is proposed. This study combines the ubiquitous-joint model, random forest algorithm (RF), and cuckoo search algorithm (CS) to construct the parameters identification method of a jointed rock mass. The parameter determination is transformed into a global optimization problem. In this method, the mean square error between the measured displacement (stress) and the calculated displacement (stress) is taken as the objective function, and the joint parameters are taken as the decision variables. The method is applied to the project of Qingniwaqiao Metro Station of Dalian Metro Line 5. This method can be used for the back-analysis of parameters of a jointed rock mass in underground engineering construction.

Deformation Analysis of the Rock Surrounding a Tunnel Excavated through a Gently Dipping Bed

To investigate the deformation and stability of the rock surrounding a tunnel excavated through layered rock, a three-dimensional numerical simulation was conducted to compare and analyze the right line of the YD2K100+560–630 two-stage docking cross-section of the Yuelongmen Tunnel using a ubiquitous joint model. Based on 3-D numerical simulations, the following conclusions were drawn: (1) The excavation on the construction entrance side significantly disturbed the construction exit side, and the exit side was more disturbed in the steeply dipping layer than in the gently dipping layer. (2) The influence of the dip angle of the laminae on the uplift of the tunnel invert was greater than the influence on the tunnel vault settlement when the laminae were oriented perpendicular to the trend of the tunnel and two-stage docking excavation was used. (3) When two-stage excavation was applied to gently inclined laminated rock, there was an obvious disturbance to both the top of the tunnel (less than one time the diameter of the through face; and to the bottom of the tunnel within 0.5 time the diameter of the through face on the side with the stopping construction exit side during the tunnelling process. When tunnel excavation was conducted against the trend of the layer, there was obvious disturbance to the top of the tunnel within 0.5 time the diameter of the through face and to the bottom of the tunnel within one time the diameter of the entrance face) on the construction exit side during the tunnelling process due to the presence of laminae. The excavation on the construction entrance side significantly disturbed the construction exit side. When docking and penetrating layered rock tunnels, priority should be given to docking and penetrating in the direction corresponding to the layers, and temporary support on the exit side should be strengthened to ensure the deformation stability of the surrounding rock mass.

Application of the Slope Coefficient of the Equivalent M–C Criterion in Layered Rock Mass Engineering

The slope coefficient ω is defined based on the insufficiency of the area equivalent method, the slope of the equivalent M–C criterion obtained from the instantaneous equivalent, and the optimal first‐order approximation to reduce the error between the simulated value and the measured value of the surrounding rock and ensure the safety of the project. Different ω conditions are set to obtain multiple equivalent M–C strength parameter combinations. The above combinations are input to the ubiquitous joint model of FLAC3D, and the surrounding rock strength of layered tunnels with different inclination angles (0°, 30°, 45°, 60°, and 90°) is corrected. The results show that (1) after the tunnel excavation is completed, the displacement of key points (e.g., the vault and waist) increases when the slope coefficient is increased and the deviator stress decreases when the slope coefficient is increased. (2) After the area equivalent method is revised, the displacement and the deviator stress are more significantly affected by the inclination of the rock strata than the uncorrected ones, suggesting that the equivalent area can more effectively highlight the anisotropy characteristics of the layered surrounding rock. (3) After the simulation results of the displacement and the deviator stress at the respective key point are comprehensively modified, the optimal slope coefficient corresponding to each rock layer inclination is obtained, and the area is optimized by ensuring reasonableness to reduce the error between the simulated value and the measured value. (4) The layered surrounding rock at a dip angle of 30° is studied. The development of the plastic zone is promoted when the slope coefficient is increased, and the rock shear failure and the joint shear failure occur simultaneously on both sides of its axis.

Deformation Development Mechanism in a Loess Slope With Seepage Fissures Subjected to Rainfall and Traffic Load

Loess landslides induced by rainfall and traffic load are significant hazards during the construction and operation of highways in many loess-covered areas. Studies of the deformation and stability of loess slopes with seepage fissures are limited. In the study, a case study of the Yangpoyao loess slope with seepage fissures in China’s Loess Plateau was conducted to reveal the deformation development mechanism and assess the landslide hazards of such fissured loess slopes. First, the hydraulic-mechanical properties of the Q2 loess were investigated through experiments, and the mathematical expressions of the relationships between various mechanical parameters and water content were fitted, indicating that the mechanical parameters, such as cohesion, angle of internal friction, and deformation modulus, vary in a quasi-linear manner with the water content. Then, a new numerical method was proposed to simulate the mechanical behaviours of the loess considering its water sensitivity and transverse isotropy, where the water sensitivity was considered through the implementation of the mathematical expressions of the hydraulic-mechanical relationships, and the transverse isotropy was considered by the modified constitutive model that combined the logics of transversely elastic model and a ubiquitous-joint model. Finally, the deformation development mechanism of the fissured loess slope under rainfall and traffic load was revealed by using the proposed method. The roles of the rainfall and traffic load in the fissure propagation and deformation development process of the slope were explored, and some stabilisation measures are recommended for the prevention of its failure. The proposed method and findings arising therefrom may provide references for future studies of the stability and landslide hazard assessment of fissured loess slopes.

An Enhanced Ubiquitous-Joint Model for a Rock Mass With Conjugate Joints and Its Application on Excavation Simulation of Large Underground Caverns

A conjugate jointed rock mass (CJRM) is a rock mass with two sets of intersecting joints formed from intact rock under shear. Its mechanical properties and excavation-induced hazards of large underground caverns are different from those of common rock masses because of the unique geological origin thereof. To demonstrate numerically the excavation responses of CJRM, the ubiquitous-joint model is enhanced by consideration of the specific mechanical behaviors of the rock mass. In the enhanced model, CJRM is considered as the composite of columns of rock and two sets of weak planes of joints. The local coordinates, failure modes, and failure sequences of the rock columns and joints are redefined based on the composite characteristics of CJRM, and the failure criteria and plastic potential functions are accordingly modified. The enhanced model is verified numerically by triaxial compression tests and then employed to simulate the excavation of large underground caverns of a pumped storage power station in China. Results show that the modification of the local coordinate system, failure modes, and failure sequences made in the enhanced model is suited to the simulation of the mechanical behaviors of CJRM. Compared with the original ubiquitous-joint model, the enhanced model allows better predictions of the distribution of plastic zones and magnitudes of deformations in simulating underground excavations in CJRM and helps to assess the excavation-triggered hazards more accurately.

Investigation of Failure Mechanism of Inclined Coal Pillars: Numerical Modelling and Tensorial Statistical Analysis with Field Validations

Analysis of the failure mechanism of inclined coal pillars is one of the complicated issues. The wide variability of dip angles of inclined coal pillars makes it more complex. The asymmetric stress distribution and the tendency of shearing along the bedding planes make the inclined coal pillars to behave differently from the flat coal pillars. There is a need for in-depth investigation of the failure mechanism for addressing the instability problems of the inclined coal pillars. Most of the literature quantifies only the magnitudes of the mean principal stresses by classical statistics. As the stress is a second-order tensor having six independent components, the classical statistics is not appropriate to calculate the mean and variability of the principal stresses at the onset of failure of the pillars. In this paper, a comprehensive analysis is done to understand the complex failure mechanism of the inclined coal pillar using numerical modelling as well as tensorial statistics and validated the results with field measurement data of failure cases. The failure mechanism is analysed by quantification of the characteristics of the inclined coal pillars by the principal-stress magnitude and its orientation, induced at the time of failure. Since the spatial variability of the magnitudes and orientations of the induced principal stresses exist within the inclined coal pillars, the mean induced principal stresses $$\left( {\overline{{\sigma_{1} }} {, }\;\overline{{\sigma_{2} }} {\text{ and }}\overline{{\sigma_{3} }} } \right)$$ are used to quantify the stress states within it. The failure stress states within the coal pillars having different dip angles are generated by the calibrated elasto-plastic numerical modelling with the ubiquitous joint model. Several statistical parameters are calculated to quantify the stress-tensor variability and the correlation among the stress-tensor components. It is found that the correlation coefficients among the shear components increase significantly with the increase of the coal pillar dip angle. Therefore, the inclined coal pillars are highly susceptible to shear failure. The magnitudes, as well as orientations of the mean induced principal stresses within the coal pillars obtained through numerical modelling, are quantified by the tensorial as well as classical statistics. It is found that the magnitude of the mean major induced principal stress $$\left( {\overline{{\sigma_{1} }} } \right)$$ at the time of failure, i.e. the strength of the pillar decreases with the increase of the dip angles. The validation of the results with the actual stress measurement data shows that all the failed pillar cases are correctly predicted by the tensorial statistical approach whereas the classical statistical approach does not effectively predict the actual failed condition of the pillars. The study would help to characterise the behaviour of the inclined pillars and address the instability issues for safe and efficient mining of inclined coal seams.

Understanding the failure mechanism of a large underground cavern in steeply dipping layered rock mass using an enhanced ubiquitous-joint model

To understand the mechanical behavior and failure mechanism of the surrounding layered rock masses during the excavation of underground caverns for a hydropower station, an enhanced equivalent continuum model based on the ubiquitous-joint concept is developed and compiled as a plugin DLL file in FLAC3D. This model is then applied to analyze two engineering geological issues arisen during the excavations of a large underground powerhouse. Both cases are the typical responses controlled primarily by the internal structure of layered rock mass. The first case is mainly concerned with the continuous increase in the displacement of the upstream sidewall after removal of an auxiliary tunnel crown. Numerical simulation reveals the mixed shear-tensile fractures developed along bedding planes. The preserved crown thickness can affect the maximum displacement of sidewall. Failure region will progressively deepen into the interior if no effective reinforcements are adopted. The second case exhibits as the gradual cracking or slabbing of the shotcrete at downstream roof. Stress concentration is the main cause of shotcrete cracking as shown by numerical simulation. The degree of stress concentration can be influenced largely by the angle between rock strata and cavern axis. This degree also varies with the initial stress level and with excavation process, which is confirmed by field monitoring data. The validity and capability of the newly developed model are thus verified by the actual engineering issues.

Numerical analysis of influence of joint inclination on the stability of high rock slope with weak interlayer

In the mountainous area of southwest China, the horizontal layered steep slopes with weak intercalations are widely distributed. The stability of these slopes is often controlled by the weak intercalations and the dominant joint sets. Based on the strength reduction method, a representative numerical simulation model is established in this study, and the ubiquitous-joint model is adopted in which the properties of rock blocks and joints can both be considered, in order to analyze the influence of joint angle on slope stability and potential sliding surface of such slopes. The research results indicate that the joint inclination angle is closely related to both the safety coefficient and the potential sliding range of the slope. With the increase of joint inclination angle, the safety coefficient of the slope decreases, but the downward trend gradually becomes slower. The joint inclination angle also has an obvious influence on the sliding surface range of the horizontal layer slope with weak interlayer. The research results have certain guiding significance in the analysis of failure mechanism, hazard assessment and engineering prevention of this kind of slope.

Parameters Identification of Tunnel Jointed Surrounding Rock Based on Gaussian Process Regression Optimized by Difference Evolution Algorithm

Due to the geological body uncertainty, the identification of the surrounding rock parameters in the tunnel construction process is of great significance to the calculation of tunnel stability. The ubiquitous-joint model and three-dimensional numerical simulation have advantages in the parameter identification of surrounding rock with weak planes, but conventional methods have certain problems, such as a large number of parameters and large time consumption. To solve the problems, this study combines the orthogonal design, Gaussian process (GP) regression, and difference evolution (DE) optimization, and it constructs the parameters identification method of the jointed surrounding rock. The calculation process of parameters identification of a tunnel jointed surrounding rock based on the GP optimized by the DE includes the following steps. First, a three-dimensional numerical simulation based on the ubiquitous-joint model is conducted according to the orthogonal and uniform design parameters combing schemes, where the model input consists of jointed rock parameters and model output is the information on the surrounding rock displacement and stress. Then, the GP regress model optimized by DE is trained by the data samples. Finally, the GP model is integrated into the DE algorithm, and the absolute differences in the displacement and stress between calculated and monitored values are used as the objective function, while the parameters of the jointed surrounding rock are used as variables and identified. The proposed method is verified by the experiments with a joint rock surface in the Dadongshan tunnel, which is located in Dalian, China. The obtained calculation and analysis results are as follows: CR = 0.9, F = 0.6, NP = 100, and the difference strategy DE/Best/1 is recommended. The results of the back analysis are compared with the field monitored values, and the relative error is 4.58%, which is satisfactory. The algorithm influencing factors are also discussed, and it is found that the local correlation coefficient σf and noise standard deviation σn affected the prediction accuracy of the GP model. The results show that the proposed method is feasible and can achieve high identification precision. The study provides an effective reference for parameter identification of jointed surrounding rock in a tunnel.

A numerical study on mechanical behavior of jointed rock masses after tunnel excavation

The tunnel in jointed rock masses is prone to be overbroken and then gives rise to collapse, yet the failure modes of jointed rock masses are still poorly understood. This paper investigates anisotropic deformations and failure modes of tunnels in jointed rock masses. For this purpose, five series of numerical models are modeled for a severe tunnel overbreak occurring on the Panlongshan tunnel. The ubiquitous joint model is used to consider the shearing and tensioning effects of the bedding and joint structures. The factors affecting anisotropic deformation and failure of rock masses, such as bedding spacing (s), joint dip angles (θ), and joint spacing (d), are discussed. The results demonstrate that for the stratified rock masses (without joint), the maximum settlement around the tunnel is located at the roof, and the separation of “virtual blocks” along the bedding planes is a basic failure mode; for stratified rock masses containing joints, the maximum deformation surrounding the tunnel appears in the joint position, and failure happens through a combined rotation, sliding, and falling mechanism. Our study can also reveal that with the increase of the number of joints, the plastic zone at the joint positions has a developing tendency towards the deep part. The more complex the joint structures in jointed rock masses are, the more unstable rock masses are formed.

Stability Analysis of Jointed Rock Slope by Strength Reduction Technique considering Ubiquitous Joint Model

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.

Ground support performance in deep underground mine with large anisotropic deformation using calibrated numerical simulation (case of mine-H)

High-stress and complex geological conditions impose great challenges to maintain excavation stability during deep underground mining. In this research, large anisotropic deformation and its management by support system at a deep underground mine in Western Australia were simulated through three-dimensional finite-difference model. The ubiquitous-joint model was used and calibrated in FLAC3D to reproduce the deformation and failure characteristics of the excavation based on the field monitoring results. After modeling verification, the roles of mining depth also the intercept angle between excavation axis and foliation orientation on the deformation and damage were studied. Based on the results, quantitative relationships between key factors and damage classifications were presented, which can be used as an engineering tool. Subsequently, the performance of support system installation sequences was simulated and compared at four different scenarios. The results show that, first surface support and then reinforcement installation can obtain a better controlling effect. Finally, the influence of bolt spacing and ring spacing were also discussed. The outcomes obtained in this research may play a meaningful reference for facing the challenges in thin-bedded or foliated ground conditions.

Assessment of the Strength of Inclined Coal Pillars through Numerical Modelling based on the Ubiquitous Joint Model

The inclined coal pillars, formed during the underground extraction of the inclined coal seam, are different from the flat coal pillars due to the high strength anisotropy of the inclined bedded rock, and the asymmetrical stress distribution. To ease the manoeuvring of the men and machinery in the inclined coal mine, the pillars are developed along the apparent dip. Thus, the pillars become rhombus-shaped with acute-angled corners which crush rapidly due to the high stress concentration. No suitable formula is found to estimate the strength of the inclined coal pillar that incorporates all these factors. Thus, the use of the available coal pillar strength formulae may endanger the extraction of the inclined coal seams. This study elucidates the procedures to estimate the strength of the inclined coal pillars by the numerical modelling technique. The ubiquitous joint model is used to simulate the shearing characteristics of the inclined strata. The parametric study shows that the strength of the inclined coal pillars decreases with the increase of the dip of the coal seams. It is also obtained that the strength of the pillars decreases with the decrease of the value of the acute angle of the corners. The peak stress distribution and the strain accumulation over the inclined pillars at the time of failure are plotted in three-dimensional graphs which show the asymmetrical characteristics of the inclined coal pillars. The analysis of variance shows that the dip of the coal seams and the acute angles of the corners have a statistically significant effect on the strength of the inclined coal pillars. Based on the results of the simulation, the best fit relation is established by the multivariate non-linear regression technique to estimate the strength of the inclined coal pillars. The coefficient of determination (R2) and the root mean square error of the model are obtained as 0.92 and 0.065, respectively. The validation of the developed model has been carried out by the stable and failed inclined pillar cases of different underground inclined coal mines in India. Comparisons of the safety factors, obtained from the developed model and the flat pillar strength formula, indicate that the flat pillar strength formula overestimates the strength of the inclined coal pillars. The developed model can be used to design the inclined coal pillars for safe extraction of inclined coal seams.

Probabilistic assessment of rock slopes stability using the response surface approach – A case study

This paper examines the stability condition of a jointed rock slope in the south western region of Saudi Arabia using deterministic and probabilistic approaches, under both dry and wet conditions. The study area is characterized by complex geology in rugged terrains. The stability analysis is carried out using the code FLAC3D to generate a 3-dimensional, ubiquitous joint model, to determine the influence of the dominant, unfavourable discontinuity orientation with respect to the slope face. The deterministic analysis is first implemented using the mean values of the selected random variables, namely the dip, dip direction and friction angle of the dominant discontinuity set, and the stability condition is assessed with a factor of safety based on the classical frictional joint constitutive model. A Box-Behnken design (BBD) approach is then adopted to create the surface response function as a second order polynomial for the factor of safety. To do so, fifteen FLAC3D models are generated in accordance with the BBD. Based on this, 10,000 simulations of different slope realizations are carried out using Monte-Carlo simulation technique, and the probability of unsatisfactory of performance of the rock slope is assessed. It is shown that the probabilistic approach provides more insight and confidence in the stability condition of the rock slope, both under dry and steady state heavy rainfall conditions. A discussion is presented on the significance of accepting lower safety factors when heavy rainfall conditions are encountered.

Numerical Investigation of Squeezing in Underground Hard Rock Mines

Squeezing ground is one of the major challenges associated with deep, high-stress mining. In underground hard rock mines, these conditions are often a result of the presence of prominent structural features such as foliation inside the rock mass, which imposes mechanical anisotropy and leads to a nonlinear and anisotropic response of the rock mass to mining. Understanding this response of foliated rocks to various mining conditions is essential for managing the squeezing ground conditions. The complex behavior of a foliated rock mass requires the use of numerical methods to investigate the response of the rock mass to mining. Discontinuum numerical methods are frequently used to simulate anisotropic behavior, as they can explicitly represent the fractures. However, these methods present time and computational restrictions for large-scale models and complex mining geometries. These limitations can be overcome by employing anisotropic constitutive models in continuum numerical methods. This paper presents a methodology to investigate the failure mechanism of an intact foliated rock sample and foliated rock mass around an underground excavation utilizing the ubiquitous-joint model in continuum numerical methods. The paper also presents an approach that can be used to investigate the influence of varying interception angles between the foliation and excavation walls on the severity of squeezing ground conditions. The ubiquitous-joint model employed in FLAC3D accounts for the presence of weakness planes such as foliations in continuum material and can successfully reproduce the observed displacements and failure mechanism. The numerical modeling results were in good agreement with the closure strains recorded underground.

Constitutive model for inherent anisotropic rocks: Ubiquitous joint model based on the Hoek-Brown failure criterion

This paper proposes an elasto-perfect plastic constitutive model (called Jhoek) linking two failure criteria to model the sliding and non-sliding failure modes of anisotropic rocks. For non-sliding failure mode, modified Hoek-Brown criterion with an explicit function of the rock parameter mi with orientation β is applied, while the single plane of weakness is simulating the sliding failure mode. Published experimental datasets of anisotropic rocks are used to validate this model. Jhoek could predict failure envelopes of rock samples under triaxial loading conditions at different orientation angles. Besides that, Jhoek model shows sensitivity to the intermediate principal stress in 3-dimensional cases.

Prediction of Mud Pressures for the Stability of Wellbores Drilled in Transversely Isotropic Rocks

Serious borehole instability problems are often related to the presence of weakness planes in rock formations. In this study, we investigated the stability of wellbores drilled along a principal direction and parallel to the weakness planes. We used three different strength criteria (weakness plane model, Hoek and Brown and Nova and Zaninetti) to calculate the mud pressures to avoid slip and tensile failure along the weakness planes. We identified the orientation of the weakness planes that generate the most critical slip condition as a function of the friction angle of the planes. We also identified the range of orientations of the weakness planes that corresponds with the lower mud pressure window. We confirmed the validity of the proposed relationships with comparative stability analyses by using analytical solutions and numerical simulations (Ubiquitous Joint Model, FLAC). We found that the mud pressures calculated with the Hoek and Brown criterion show a particular trend, which cannot be predicted by the weakness plane model. We provided two normalized stability charts to predict mud pressures to prevent slip along the weakness planes in the critical slip condition. Finally, we corroborated our findings by simulating the stability of wellbores drilled in the Pedernales Field (Venezuela) and in oil fields located in Bohai Bay (China).

Application of the Mohr-Coulomb Yield Criterion for Rocks with Multiple Joint Sets Using Fast Lagrangian Analysis of Continua 2D (FLAC2D) Software

The anisotropic behavior of a rock mass with persistent and planar joint sets is mainly governed by the geometrical and mechanical characteristics of the joints. The aim of the study is to develop a continuum-based approach for simulation of multi jointed geomaterials. Within the continuum methods, the discontinuities are regarded as smeared cracks in an implicit manner and all the joint parameters are incorporated into the equivalent constitutive equations. A new equivalent continuum model, called multi-joint model, is developed for jointed rock masses which may contain up to three arbitrary persistent joint sets. The Mohr-Coulomb yield criterion is used to check failure of the intact rock and the joints. The proposed model has solved the issue of multiple plasticity surfaces involved in this approach combined with multiple failure mechanisms. The multi-joint model was implemented into Fast Lagrangian Analysis of Continua software (FLAC) and is verified against the strength anisotropy behavior of jointed rock. A case study considering a circular excavation under uniform and non-uniform in-situ stresses is used to illustrate the practical application. The multi-joint model is compared with the ubiquitous joint model.

Simulation of Sidewall Failure in Coal Mine Roadways Using an Extended Continuous Joint Model

Coal is well developed with beddings, and the beddings play an important role in the stability of tunnel stability of coal mine. This study focused on jointed rock mass with two sets of joint and proposed an extended ubiquitous model and associated numerical implementation accounting for joint spacing to represent geometric features of coal. The failure criteria of two sets of joint proposed in this paper not only accounted for joint spacing, but also contained the ubiquitous joint model. This extended theory was validated against the discontinuous deformation analysis method, the plane of weakness theory and experimental results for jointed coal with different joint fabric. The model is also used to analyze tunnel stability of roadways in coal mine with different joint spacing. The ubiquitous joint model could simulate jointed coal with small joint spacing, but for that with larger joint spacing, the ubiquitous joint model is not applicable and the joint model containing joint spacing proposed by this paper should be used. A series of comparisons demonstrated that the proposed model was capable of considering the influence of joint spacing on jointed coal tunnel with two sets of joint.

An enhanced equivalent continuum model for layered rock mass incorporating bedding structure and stress dependence

Layered rock masses exhibit significant anisotropy in both the deformability and strength. Properties of this rock mass are largely affected by its bedding structure and also by the stress state change. For the purpose of characterizing these salient features using the equivalent continuum concept, an enhanced model is proposed in this paper based on the ubiquitous-joint model. In the enhanced model, the intact bedded rock is assumed to behave as a transversely isotropic elastic body. A modified anisotropic strength criterion is adopted to describe the direction dependence of the strength of intact bedded rock. In addition, stress-sensitive parameters are utilized for both the intact rock and bedding plane, among which the dilation angle and strength parameters of intact rock are influenced by confining pressure and loading history, whereas the stiffnesses of bedding planes are closely related to the current normal stress. The effect of layer thickness on the mechanical behavior of rock mass is reflected by continuously updating the global stiffness matrix after failure of bedding plane, and by conditions for conducting bedding plane related calculations determined by the relative scales between element size and layer thickness. Preliminary validation of this model is conducted by comparing with the closed-form solutions and with laboratory tests. Generally good agreements can be achieved between numerical simulations and theoretical/experimental results, which indicate that applicability of the enhanced model on underground engineering issues related to layered rock mass is promising.