Stability Of High Rock Slopes Research Articles

Stability Analysis of Blasting Excavation for High Rock Slope of Highway Reconstruction and Expansion

To analyze the stability of high rock slopes under millisecond blasting in the paper, time-history curves of millisecond blasting dynamic loads are established based on field data from the reconstruction and extension project of the Beijing-Shanghai Highway. Numerical simulations and field monitoring data are used to study the dynamic response characteristics of the slope stress, displacement, velocity, and safety factor at different times. The results show that the local shear stress near the blasting area is greater than the shear strength of the rock mass, which has a good effect on precracking. Additionally, the peak vibration law of the particles near the blasting area is found to change synchronously with the application of the dynamic blast load; as the distance increases, the law gradually weakens and peak vibration occurs only near the maximum value. Moreover, the safety factor of the slope exhibits a decreasing periodic variation. When the dynamic blast load F reaches the maximum load Fmax and 0.6 Fmax, the corresponding safety factor reaches the minimum load.

Assessing the rainfall infiltration on FOS via a new NSRM for a case study at high rock slope stability

Assessing the stability characteristics of high rock slope under rainfall via theoretical research, numerical simulation, and field monitoring is of great implications for safety construction in open-pit mine engineering. Thus, based on the Hoke-Brown criterion, instantaneous internal friction angle and cohesion of high-slope rock mass under high stress conditions were deduced, and a nonlinear strength reduction method for high rock slope was established. The safety factors of the open-pit mine were calculated by COMSOL Multiphysics, which considering the high rock southwest slope and detected rainfall in Dagushan Open-pit Mine, China. The results showed that high rock slope stability could be more accurately analyzed by the proposed method due to its full consideration of slope stress state effect compared with the equivalent Mohr- Coulomb method. When the slope is low, the difference between the calculation results of the equivalent Mohr- Coulomb method and the proposed method is small, but with the increase of the slope height, the difference between the two calculation results gradually increases. When the transient saturated is formed in the slope surface layer and gradually increases, the reduction rate of the factor of safety (FOS) gradually increases. When the total rainfall is the same, the effect of short-term heavy rainfall on slope stability is less than that of long-term ordinary rainfall. The results obtained form this work provided important insights into the stability of high rock slope and rainfall infiltration in open-pit mine, and the safety factor is crucial for guiding the mining process design.

Computational tools for the analysis of circular failure of rock slopes

Among other types of failure in slopes created by excavation or filling, circular (also referred to as rotational) type of failure plays an important role in the design and stability analysis of high rock slopes, such as those encountered in deep open pit mines. When a rock slope of significant height involves predominantly one type of jointed rock mass, the scale of the problem is frequently such that the rock mass (intact rock and rock discontinuities) can be regarded as a homogeneous isotropic material. In such case, if the rock slope is unstable and collapse occurs, circular (or rotational) failure as in failed slopes in soils is also observed for the rock slope. One main goal in practical design of deep open pit mines is to determine safe inclination angles for the pit faces to be excavated to avoid failure. Computational tools for quick assessment of the stability conditions, in particular determination of factor of safety and location of the critical circular failure surface, are useful during the preliminary stages of open pit design. Among others, such tools allow the engineer to gain insight in the role that the different variables controlling the problem have in defining the stability conditions for the rock slope. This paper provides first an overview of typical numerical techniques used to assess the stability of high rock slopes. For the case of slopes in rock masses that are assumed to obey the Mohr-Coulomb or the Hoek-Brown failure criteria, the paper discusses how application of transformation rules leads the criteria to be re-casted in dimensionless form, so when these are applied to the solution of slope problems, the results (factor of safety and coordinates that define the location of the critical circular failure surface) can be summarized in dimensionless compact forms. The paper presents then computational tools in the form of dimensionless charts and computer spreadsheets for stability analysis. These are developed from numerical limit equilibrium models that use the mentioned transformation rules. Among others, the computational tools allow the concept of mechanical similarity of rock slopes to be naturally introduced. Finally, the paper presents various rock slope examples that illustrate the use of the computational tools. In these examples, results from limit equilibrium models are also compared with results obtained with full numerical analysis, in particular with finite difference models implementing the shear strength reduction technique.

Stability Assessment of High and Steep Cutting Rock Slopes with the SSPC Method

The stability of high rock slopes has become a key engineering geological problem in the construction of important projects in mountainous areas. The original slope stability probability classification (SSPC) system, presented by Hack, has made obvious progress and been widely used in rock slope stability analysis. However, the selection and determination of some evaluation indexes in the original SSPC method are usually subjective, such as intact rock strength and weathering degree. In this study, the SSPC method based on geological data obtained in the prospecting tunnels was presented and applied. According to the field survey and exploration of the prospecting tunnels, the weathering degree of the slope rock mass was evaluated. The empirical equation for the maximum stable height of the slope was applied to the slope stability evaluation in the presented SSPC method. Then, the slope stability probability of numerous cutting slopes in the sandstone unit was evaluated using the presented system. Results of the Geostudio software based on the limited equilibrium analysis of the investigated slopes were compared with the results obtained by the SSPC method. The results indicate that the SSPC method is a useful tool for the stability prediction of high and steep rock slopes.

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.

Modification of slope stability probability classification and its application to rock slopes in hydropower engineering regions

Stability assessment of rock slopes in hydropower engineering regions is an important and complex issue. Rock mass classification systems are a good approach because they can thoroughly consider many factors influencing rock slope stability. The slope stability probability classification (SSPC) system is a novel method. However, it has two limitations when applied to rock slopes: 1) it is only suitable for slopes less than 45 m in height, and 2) there is great subjectivity and randomness in the estimation of intact rock strength. Therefore, this study presents two modifications of the SSPC system by adopting the Hoek-Brown strength criterion and an empirical formula for maximum slope height. Evaluation of results from of 34 typical rock slopes of the major hydropower engineering regions in China indicated that the accuracy rate of the modified SSPC for stability evaluation of these slopes was 61.8%, and the accuracy for stability evaluation of 10 slopes with non-structural control failure was 80%. The stability values of stable and unstable slopes obtained using the modified SSPC were different to those obtained using the Chinese Slope Mass Rating (CSMR) and modified CSMR systems. In addition, the identification accuracy rate of the modified SSPC was significantly higher than that of the CSMR and modified CSMR. Therefore, the modified SSPC can be applied to hydropower engineering regions, providing a new means of rapidly evaluating the slope stability of high rock slopes (slopes > 45 m in height) in these regions.

Application of Remote Sensing to the Investigation of Rock Slopes: Experience Gained and Lessons Learned

The stability and deformation behavior of high rock slopes depends on many factors, including geological structures, lithology, geomorphic processes, stress distribution, and groundwater regime. A comprehensive mapping program is, therefore, required to investigate and assess the stability of high rock slopes. However, slope steepness, rockfalls and ongoing instability, difficult terrain, and other safety concerns may prevent the collection of data by means of traditional field techniques. Therefore, remote sensing methods are often critical to perform an effective investigation. In this paper, we describe the application of field and remote sensing approaches for the characterization of rock slopes at various scale and distances. Based on over 15 years of the experience gained by the Engineering Geology and Resource Geotechnics Research Group at Simon Fraser University (Vancouver, Canada), we provide a summary of the potential applications, advantages, and limitations of varied remote sensing techniques for comprehensive characterization of rock slopes. We illustrate how remote sensing methods have been critical in performing rock slope investigations. However, we observe that traditional field methods still remain indispensable to collect important intact rock and discontinuity condition data.

A Preliminary Investigation on the Role of Brittle Fracture in the Kinematics of the 2014 San Leo Landslide

The stability of high rock slopes is largely controlled by the location and orientation of geological features, such as faults, folds, joints, and bedding planes, which can induce structurally controlled slope instability. Under certain conditions, slope kinematics may vary with time, as propagation of existing fractures due to brittle failure may allow development of fully persistent release surfaces. In this paper, the progressive accumulation of brittle damage that occurred prior to and during the 2014 San Leo landslide (northern Italy) is investigated using a synthetic rock mass (SRM) approach. Mapping of brittle fractures, rock bridge failures, and major structures is undertaken using terrestrial laser scanning, photogrammetry, and high-resolution photography. Numerical analyses are conducted to investigate the role of intact rock fracturing on the evolution of kinematic freedom using the two-dimensional Finite-discrete element method (FDEM) code Elfen, and the three-dimensional lattice-spring scheme code Slope Model. Numerical analyses show that the gradual erosion of clay-rich material below the base of the plateau drives the brittle propagation of fractures within the rock mass, until a fully persistent, subvertical rupture surface form, causing toppling of fault-bounded rock columns. This study clearly highlights the potential role of intact rock fracturing on the slope kinematics, and the interaction between intact rock strength, structural geology, and slope morphology.

Study on Stability of the High Rock Slope under the Flood Discharge Atomization and Rainfall

The stability of high rock slopes under the flood discharge atomization and rainfall is an in-negligible problem especially for the hydropower station with high head during the flood discharge. According to the complicated geological conditions of a high rock slope with the flood discharge problem in China, the method of the saturated-unsaturated unsteady seepage if used, thus the finite element model for the high rock slope in the downstream of the power station is set up. Based on the model, the distribution regularities of the unsteady seepage field of the rock slope is studied under the different discharge atomization and rainfall intensity. Moreover, based on the theory of continuous-discontinuous deformation, the finite element model is set up to analyze the stability of the slope, thus the deformation law of slopes under the flood discharge atomization and rainfall is studied and the safety of the slope is evaluated, and what's more, the engineering measures for improve the stability of the stability of the slope is put forward.

Macro-comprehensive evaluation method of high rock slope stability in hydropower projects

Combining with the characteristics of the rock slope in hydropower engineering, the evaluation index system of rock slope stability in hydropower projects is determined based on multiple factors, and based on this, research, collect and establish the typical rock slope database of hydropower projects. Based on the fuzzy optimal recognition theory and Case-Based Reasoning, two different methods of slope stability evaluation are established respectively. Analyzing the rock slope stability of one hydropower project by the two methods, a comparison is made between the two methods and the effectiveness of the methods is verified.

On the seismic stability analysis of reinforced rock slope and optimization of prestressed cables

The evaluation of the seismic stability of high rock slopes is of vital importance to ensure the safe operation of the hydropower stations. In this paper, an equivalent pseudo-static force analysis based on the finite element method is developed to evaluate the seismic stability of reinforced rock slopes where the prestressed cables are modeled by the bar elements applied with nodal forces and bounded only at the anchored parts. The method is applied to analyze a high rock slope in south-west China and the optimization of cables. The stabilization effects of prestressed cables on the seismic stability of the slope are studied, the simulations of the concrete heading are discussed and the potential failure modes of the shear concrete plug are compared. Based on this, the optimization of cables is studied including the anchor spacing and inclined angles.

Laws of Influence upon Dynamic Response of High Rock Slope by Seismic Wave Frequency

On the basis of seismic wave recorded by Wolong Measuring Station in Wenchuan Earthquake occurred on May 12, 2008, and taking a high rock slope (about 1397m in height) at the bank of Zipingpu Reservoir as the specific example, analyses have been made, with Plaxis dynamical simulation analysis program, on characteristics of influence upon acceleration time history, shear strain distribution, principal stresses distribution and stability of high rock slope by original seismic wave, and seismic wave with frequency expanded by 1.5, 2 and 3 times, respectively. Results of the analyses demonstrate that dynamic response characteristics of the slope top are notably influenced by multiplication factor of seismic wave frequency. As far as the real slope in this article is concerned, it generally presents a gradual decrease of PGA of the top of high rock slope, reduction of slope body shear strain and a corresponding drop of dynamic response of slope body as a whole, with the increase of seismic wave frequency.

3D Analysis on the High Rock Slope Stability of Ningde Nuclear Power Plant, Fujian Province

Ningde nuclear power plant in Fujian province is one of the national key construction projects of nuclear power, in order to insure the smooth progress of construction project, it needs to assess the rock slope stability which lies in the southeast of the living area. On the base of the rock architectural feature, the qualitative analysis, the three-dimensional limit equilibrium and the three-dimensional finite element are adopted to analyze the stability of the slope. The result of the qualitative analysis shows that most of the slope is stable, and part of it may fail after excavation. The result of the three-dimensional limit equilibrium and the three-dimensional finite element both illustrate that the slope is stable after excavation with slope ratio 1:0.25,1:0.50 and 1:0.75, and the stability factor rises with the decreasing of the slope ratio. At last, according to the above computing result, the 1:0.50 or the minor value is suggested to be adopted as the design slope ratio to excavate the slope.

Effect of rock mass characteristics of high rock slope on seismic stability

Rock mass characteristics are the key internal factors for the stability of high rock slope. The lithological association of rock mass and its structural planes, such as dominant orientations, length, fracture aperture and stiffness attenuation, is investigated by exploration methods. Quantitative description is performed in terms of fracture geological and dynamic parameters to provide necessary basic data for the stability of rock slope. Based on rock mass with different geological characteristics on one site in the Songjiang area, Shanghai city, the fracture mechanism is studied using strength reduction finite element method. The different associations of the stiffness of rock mass and the dip of its structural planes are processed in dynamic state and its effects on the safety factor of rock slope are discussed.