High Slope Stability Research Articles

Deformation response and anchorage control of excavation unloading of high and steep rock slope

The stability and anchorage control of high and steep slopes in Southwest China are challenging problems in engineering construction. Considering the unloading stability of high and steep rock slopes, field monitoring and numerical analysis methods are used for feedback analysis to study the deformation, stress response, anchorage support scheme, and anchorage stress characteristics during the unloading process of slope excavation. The research shows that the displacement of rock mass of the high slope gradually increases and the local deformation exceeds 200 mm. The unloading relaxation area resulting from slope excavation is 25 m deep. The safety of the slope can be guaranteed after the joint reinforcement of deep anchor cable.

Study on High and Steep Slope Stability and Slope Angle Optimization of Open-Pit Based on Limit Equilibrium and Numerical Simulation

The stability of open-pit slope is related to mine safety, especially for high and steep slope. In order to obtain the design slope stability and slope angle optimization of K mine open-pit in Myanmar, limit equilibrium analysis method and three-dimensional numerical simulation are used to carry out the study on the slope stability. The results show that: (1) The safety factor of the designed slope is larger than the allowable safety factor by using the limit equilibrium analysis, which belongs to the stable slope. Some areas can be optimized for design. (2) Through three-dimensional numerical analysis, the design slope and the optimized slope are both stable. The area with large deformation of the optimized slope is mainly concentrated in the area of 562 m level moderately weathered pyroclastic rock in area A and 560 m level moderately weathered rock in area B. The calculation results of three-dimensional numerical simulation are basically consistent with the results of the limit equilibrium analysis. (3) Compared with the designed slope, the potential sliding surface position of the optimized slope is lower. The safety factor is smaller, but larger than the allowable safety factor. The shape of the sliding surface of the whole slope is nearly circular arc. The sliding mode of the slope is circular arc sliding. (4) The reasonable slope angle of different engineering geological divisions of the open-pit slope of K mine is determined. The overall slope angle of area A is ≤ 46°. The overall slope angle of area B is ≤ 44°. The overall slope angle of area C is ≤ 45°. The overall slope angle of area D is ≤ 50°. The research results can provide reference for mine safety production.

Comprehensive Method to Test the Stability of High Bedding Rock Slop Subjected to Atomized Rain

In the construction of high dams, many high rock slope failures occur due to flood discharge atomized rain. Based on the steel frame lifting technique and strength reduction materials, a comprehensive method is proposed in this paper to study the stability of high bedding rock slope subjected to atomized rain. The safety factor expression of the comprehensive method and the evaluation method for deformation instability were established according to the similarity theory of geomechanical model, failure criterion, and mutation theory. Strength reduction materials were developed to simulate the strength reduction of structural planes caused by rainfall infiltration. A typical test was carried out on the high bedding rock slope in the Baihetan Hydropower Station. The results showed that the failure modes of the bedding rock slope were of two types: sliding–fracturing and fracturing–sliding. The first slip block at the exposed place of the structural plane was sliding–fracturing. Other succeeding slip blocks were mainly of the fracturing–sliding type due to the blocking effect of the first slip block. The failure sequence of the slip blocks along the structural planes was graded into multiple levels. The slip blocks along the upper structural planes were formed first. Concrete plugs had effective reinforcement to improve the shear resistance of the structural planes and inhibit rock dislocation. Finite element method (FEM) simulation was also performed to simulate the whole process of slope failure. The FEM simulation results agreed well with the test results. This research provides an improved understanding of the physical behavior and the failure modes of high bedding rock slopes subjected to atomized rain.

鄂西山区高速公路深挖路堑高边坡稳定性研究

鄂西山区高速公路深挖路堑高边坡稳定性研究

A novel acoustic emission parameter for predicting rock failure during Brazilian test based on cepstrum analysis

Acoustic emission (AE) is widely used in the monitoring of coal and rock stability and early warning of dynamic disasters in mines. In this work, the Brazilian split test was carried out on limestone samples along with collecting full waveform AE signal during the entire loading process. The linear cepstrum coefficient (LCC) was used as the characteristic parameter of AE to analyze the correlation between the LCC of AE and the load of the samples. The results show that the LCC is an effective AE characteristic parameter. The first to fourth parameters of the LCC calculated using 1 s AE waveform meet the linear change relationship with the load of the samples. The correlation coefficients are 0.969, 0.943, 0.925, 0.833, respectively. The LCC of AE proposed in this work can be used as a characteristic parameter for predicting the tensile failure of rocks, which is helpful to improve the application effect of AE in the monitoring of coal and rock dynamic disasters and the stability of high and steep slopes.

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.

Deformation and Reinforcement Monitoring Analysis of Tail Water Outlet Slope in a Hydropower Station

The slope stability situation surrounding the dam site area is very important to each correlative department during constructing hydroelectric power station. So it is important to enforce the high slope rock deformation monitoring, and to process and analyze the measuring data timely. Surface displacement of different height of slope were tracked and monitored based on the field investigation of a hydroelectric power station in Jinsha river. Deformation and the static stability of high slope were analyzed by utilizing rock deformation monitoring data. Taking the left-bank tailrace outlet slope of underground power station for example, we analyzed the slope stability by numerical simulation to obtain the characteristics of deformation and failure of slope. The time and space deformation distribution regularity of rock mass were summarized, the deformation, stress and failure of the studied slope were simulated. The results intuitively show the displacement distribution characteristics and slope plastic failure.

Valley Deformation and Slope Seismic Analysis near Tail Water Outlet of a Hydropower Station

The safety and stability problems of high rock slope, such as weaken massif, fully developed geological conformations, widely unloaded or flabby rock layer, and squirming or sliding rock, are often encountered in engineering practice. So it is important to enforce the high slope rock deformation monitoring, and to process and analyze the measuring data timely. The high slope of the left-bank tailrace outlet of Wudongde hydropower station in Jinsha river is given as an example to analyze valley deformation, and to evaluate the seismic stability of high slope by utilizing rock deformation monitoring data. The field data of rock deformation of the left-bank tailrace outlet slope were collected by monitoring system, along with the field data of valley deformation. Based on monitoring data of the left-bank tailrace outlet slope deformation and valley width reduction of Wudongde hydropower station, the time and space deformation distribution regularity of rock mass were summarized. Analysis results and monitoring records reveal the general law of valley deformation, and demonstrate that excavating and other perturbations can quicken the creep deformation of rock mass, and the damage will not happen under action of earthquake.

Failure of a Rock Slope Ten Years after Excavation

In the present study, a rock cut slope in Chongqing of China, which failed suddenly about ten years after excavation, was reported. The survey results after failure indicated that the rock masses of the rock slope were highly fractured and heavily weathered, the critical slip surface was composed of three connected discontinuities from the toe to top of slope. The factors resulting in the failure of rock slope were mainly initial excavation and weathering process. The initial excavation removed original supporting role of the excavated rock masses at the toe of the slope to the upper unexcavated rock masses, and broken the original ground stress balance. The physical and chemical weathering after the initial excavation cracked progressively the rock masses, deteriorated the mechanic properties of the rock masses, and changed the stresses and strains in the rock slope. The stability of high artificial rock slope during operation should be paid attention to. The characteristics of geological structure, unloading induced by excavation, and weathering have important effects on the evolution for deformation of artificial rock high slope.

Centrifuge Model Test for Deformation and Stability of High Fill Slope of Loess in the Gully Area

Based on the high fill engineering in loess gully of Yan'an, the centrifuge model test and finite element stress analysis were carried out to study the deformation characteristics and stability of high fill slope in loess with the change of water level. According to the preliminary results, the consolidation deformation during construction is dominant in the whole process. Ensure the construction quality and extend the construction time appropriately will be beneficial to avoid large settlement deformation after construction. With the rise of groundwater level, the slope is still stable. However, ground settlement deformation of slope has greatly increased. This probably leads to the harm. Meanwhile, the safety of slope is also obviously reduced. So the measures that constructing the underground drainage and monitoring systems play an important role in the high fill engineering in the gully area.

Centrifuge Model Test for Deformation and Stability of High Fill Slope of Loess in the Gully Area

Centrifuge Model Test for Deformation and Stability of High Fill Slope of Loess in the Gully Area

Soil characterization for shallow landslides modeling: a case study in the Northern Apennines (Central Italy)

In this paper, we present preliminary results of the IPL project No. 198 “Multi-scale rainfall triggering models for Early Warning of Landslides (MUSE).” In particular, we perform an assessment of the geotechnical and hydrological parameters affecting the occurrence of landslides. The aim of this study is to improve the reliability of a physically based model high resolution slope stability simulator (HIRESSS) for the forecasting of shallow landslides. The model and the soil characterization have been tested in Northern Tuscany (Italy), along the Apennine chain, an area that is historically affected by shallow landslides. In this area, the main geotechnical and hydrological parameters controlling the shear strength and permeability of soils have been determined by in situ measurements integrated by laboratory analyses. Soil properties have been statistically characterized to provide more refined input data for the slope stability model. Finally, we have tested the ability of the model to predict the occurrence of shallow landslides in response to an intense meteoric precipitation.

Study on High Cut Slope Stability and Soil Nail Structure in Loess Area

Based on contract of Lin County to Lishi K70 + 465 in Shanxi Province, finite element software is used to analyze the stability of high cut slope in loess area. The analysis result shows in the report that the overall slope stability under natural state meets the specification requirement, but under rainfall condition, the possibility of local collapse still exists. Therefore, it is necessary to reinforce the local area by adopting soil nails in conjunction with concrete panels. According to strength reduction FEM, local slope factor of safety is improved and remains stable after soil nail support. This study can provide a reference for design and construction for highway loess slope in Shanxi west regions.

基于极限平衡理论和有限元强度折减法的预应力锚索加固边坡稳定性分析研究

本文以贵阳会文变至渔安变220千伏线路铁塔边坡为依托工程，采用极限平衡法和有限元强度折减法对高边坡在预应力锚索加固前后的稳定性进行计算分析，探讨了施加预应力锚索后对边坡位移及稳定性的影响，通过模型计算结果与监测资料的对比得出结论：极限平衡理论与有限元强度折减法得到的安全系数和滑动面基本一致。监测资料与计算结果相吻合，预应力锚索加固后该边坡处于稳定状态，本文研究成果可为类似工程设计提供参考。 The paper uses the Slope of 220 kv Variable Pressure Transmission Iron Tower from Huiwen to Yu’an in Guiyang as an engineering example. It calculates and analyses the high slope stability after reinforcement by prestressed anchor cable based on the theory of limit equilibrium method and finite element strength reduction method. It discusses the influence of prestressed anchor cable on stability and displacement. The calculation results are compared with the collected monitoring data and the conclusions are drawn. The safety factors and sliding surfaces by limit equilibrium method and finite element strength reduction method are almost the same. The monitoring data are consistent with the calculation results, and the slope is stable after reinforcement by prestressed anchor cable. Thus, the result can be used as a reference for engineering design.

Assessment of rock slope stability by probabilistic-based Slope Stability Probability Classification method along highway cut slopes in Adilcevaz-Bitlis (Turkey)

Rock slope stability is of great concern along highway routes as stability problems on cut slopes may cause fatal events as well as loss of property. In rock slope engineering, stability evaluations are commonly performed by means of analytical or numerical analyses, principally considering the factor of safety concept. As a matter of fact, the probabilistic assessment of slope stability is progressively getting popularity due to difficulties in assigning the most appropriate values to design parameters in analytical or numerical methods. Additionally, the effect of heterogeneities in rock masses and discontinuities on the analysis results is minimized through the probabilistic concept. In this study, slope stability of high and steep sedimentary rock cut slopes along a state highway in Adilcevaz-Bitlis (Turkey) was evaluated on the basis of probabilistic approach using the Slope Stability Probability Classification (SSPC) system. The probabilistic assessment indicates major slope stability problems because of discontinuity controlled and discontinuity orientation independent mass movements. Almost all studied cut slopes suffer from orientation-independent stability problems with very low stability probabilities. Additionally, the probability of planar and toppling failures is significantly high with respect to the SSPC system. The stability problems along the investigated rock slopes were also verified by field reconnaissance. Remedial measures such as slope re-design and reinforcement at the studied locations should be taken to prevent hazardous events along the highway. On the other hand, the probabilistic approach may be a useful tool during rock slope engineering to overcome numerous uncertainties when probabilistic and analytic results are compared.

Deformation-based safety monitoring model for high slope in hydropower project

Because of the outstanding issue of high slope stability in hydropower project, the statistical slope stability analysis is studied by applying deformation monitoring data based on the probability and catastrophe theory. According to the analysis of geological conditions and measured information of high slope, the mechanical slope stability analysis is established. The EMD (empirical mode decomposition) method is introduced, which is used to fitting parameters and solving the aging component of slope deformation by breaking through the traditional regression model, and a method to abstract stationary and nonlinear aging component is proposed eventually. Combining with the theory of catastrophe, a cusp catastrophe model of slope stability is established. The early warning indexes of slope stability are put forward in terms of the deformation acceleration. Applying these above methods, the stability of the spillway high slope of a certain concrete face rockfill dam during operation period is analyzed and evaluated.

Study on stability of high embankment slope based on black hole algorithm

The fill is one important engineering measure to construct civil engineering, such as highway, airport, etc. However, the slope instability of embankment is very complex, which may develop locally, near the facing, within the embankment, or through the foundation soil as local, surficial, general, or deep-seated failure. To analyze the stability of one high embankment slope for one airport in the plateau loess area, whose height is about 73 m, one new method based on Spencer method and new black hole algorithm has been proposed. Using this new method, the stability of the high embankment slope has been analyzed. And the computing effect and computing efficiency of the new method have been compared with some other methods proposed in previous studies. The results show that, for its small slope angle, which is about 20°, the stability of this slope can be guaranteed, and the computing effect and computing efficiency of the new method are all very good. Moreover, the effect of main engineering measures on the stability of high embankment slope has been investigated comprehensively. The results show that, to improve the slope stability, it is a very effective method to compact the filling soil, and enlargement of the slope angle can reduce the slope stability very seriously.

Geostress tests and analysis of the Tibet Bangpu mining area

In this paper, importance of geostress in mining engineering and the development of geostress tests are stated. The basic principle of geostress measurement through stress relief method using bore strain gauge 36–2 is expounded. Through improvement on traditional test technology and technical equipment of bore strain gauge 36–2, the geostress of the Tibet Bangpu mining area, at an altitude of 4670 m, was successfully tested. This provides technical reference for the stress measurement in similar areas and provides an analysis basis for the nearly 1000 m high slope stability. Combined with field test results and a sequence of elastic modulus experiment results, the geostress was obtained and analysed. The thickness of the overlying strata is one of the main factors to influence stress in the mining area the value of the minimum principal stress. The maximum principal stress is 2.1 times the vertical stress when the thickness of the overlying strata is greater than 100 m. The regional tectonic stress of the Bangpu mining area is in a NE direction due to the Indian Ocean plate subducting beneath the Eurasian plate. The stereographic projection of the three-dimensional geostress test azimuth and the Tibet Bangpu mining area final design pit slope analysis the superiority and inferiority with the final pit slope’s stress state from the aspects of the geostress, indicate that 1# and 6# final pit slope trends almost perpendicular to the maximum principal stress. This is an undesirable force state and implies that monitoring and support while open-pit mining must be strengthened.