Slope Stability Studies Research Articles

Role of admissibility criteria in limit equilibrium slope stability methods based on finite element stresses

A number of limit equilibrium slope stability methods have been developed where the factor of safety is calculated based on stresses computed using an independent finite element analysis. The internal stress distribution is usually generated using the ‘switch on’ gravity technique assuming linear elastic soil behavior. Young’s modulus and Poisson’s ratio are often assigned at random with little knowledge of how the values could impact the slope stability calculations. The results from a number of slope stability studies are provided to summarize the differing opinions regarding the sensitivity of the factor of safety to the selection of Poisson’s ratio and Young’s modulus. It would appear that the different views amongst researchers can be related to the method used to search for the critical slip surface. The factor of safety is reported to vary by less than 5% in studies where the grid and radius searching procedure is used and by more than 20% in studies where the dynamic programming searching procedure is used. The different levels of sensitivity can be related to the soil behavior model adopted in the stress – deformation analysis and the interaction of the searching procedure with the internal stress distribution in the slope.

New algorithm of mine slope reliability based on limiting state hyper-plane and its engineering application

Due to the influence of joint fissure, mining intensity, designed slope angle, underground water and rainfall, the failure process of mine slope project is extremely complicated. The current safety factor calculation method has certain limitations, and it would be difficult to obtain the reliability index when the performance function of reliability analysis is implicit or has high order terms. Therefore, with the help of the logistic equation of chaos theory, a new algorithm of mine slope reliability based on limiting state hyper-plane is proposed. It is shown that by using this new reliability algorithm the calculation of partial derivative of performance function is avoided, and it has the advantages of being simple and easy to program. The new algorithm is suitable for calculating the reliability index of complex performance function containing high order terms. Furthermore, the limiting state hyper-plane models of both simplified Bishop’s and Janbu’s method adaptive to slope project are obtained, and have achieved satisfactory effect in the study of mine slope stability in Dexing copper open pit.

Modeling the unsaturated soil zone in slope stability analysis

The linear form of the extended Mohr–Coulomb shear strength equation uses a [Formula: see text] parameter to quantify the rate of increase in shear strength relative to matric suction. When the [Formula: see text] value is unknown, a [Formula: see text] equal to 15° is sometimes used in the slope stability study to assess the influence of matric suction on the stability of a slope. In many cases, however, a [Formula: see text] value of zero is used, signifying that the effect of matric suction is ignored. Experiment results have shown that the relationship between the shear strength of an unsaturated soil and matric suction is nonlinear. Several semi-empirical estimation equations have been proposed relating the unsaturated shear strength to the soil-water characteristic curve. In this paper, the results of a study using two-dimensional slope stability analysis along with an estimated nonlinear shear strength equations is presented. The effects of using an estimated nonlinear shear strength equation for the unsaturated soils are illustrated using three example problems. Several recommendations are made for engineering practice based on the results of the example problems. If the air-entry value (AEV) of a soil is smaller than 1 kPa, the effect of matric suction on the calculated factor of safety is trivial and the [Formula: see text] value can be assumed to be zero. If the AEV of a soil is between 1 and 20 kPa, the nonlinear equations of unsaturated shear strength should be adopted. For soils with an AEV value between 20 and 200 kPa, an assumed [Formula: see text] value of 15° provides a reasonable estimation of the effects of unsaturated shear strength in most cases. For soils with an AEV greater than 200 kPa, [Formula: see text] can generally be assumed to be equal to the effective angle of internal friction, [Formula: see text], in applications where geotechnical structures have matric suctions around 100 kPa.

Slope Stability Study of Residential Area in Hay AL-Araby / Mosul with Suggested Remedial Application

Slope Stability Study of Residential Area in Hay AL-Araby / Mosul with Suggested Remedial Application

Dominant weathering profiles of granite in southern Peninsular Malaysia

One of the most important challenges in the study of slope stability, foundations, and excavation of rocks is to understand their weathering states. This issue is more important in tropical climates, where severe weathering produces thick weathering profiles with different sequences of weathering. Thick weathering profiles are normally classified or graded, based on field observation, geological studies, and the material properties of the rocks. This paper presents the results of an extensive study of changes in the geological and morphological characteristics of granite in a tropical region due to severe weathering. A total of 40 panels of rock exposure were studied in four active granite quarries located in Johor, southern Peninsular Malaysia. The proposed dominant weathering profiles of granite are mainly based on the sequences of weathering zone, topography and geological conditions, joint characterization, and the dominant color of rock material. In addition, two additional weathering subzones are introduced in the completely and the highly weathered zones based on the presence of corestones (boulders). It is believed that the proposed dominant weathering profiles can contribute to engineering design and the classification of weathered granitic rock in the tropical region.

Quantitative deterministic versus probability analyses based on a safety margin criterion

This paper proposes a new criterion called the ratio of safety margin (RSM) for use in the areas of the global factor of safety, reliability and limit states analyses with reference to their respective allowable criteria. An equation for calculating RSM based on the reliability index is formulated. Efforts for proving the applicability of this criterion include a theoretical demonstration in a simple one-variable case; an investigation on a test problem involving two random variables, followed by a slope stability study on a 156 m high embankment dam and an illustrative example presented in a EuroCode 7 guidebook. Calculation of the ratios of safety margin in the three areas provides a quantitative way to accommodate the analytical results within the same theoretical framework and makes the outcomes mutually comparable and supportive, which is much more enlightening than that would be the case by considering only one of them. Calculating RSMs for reliability and limit states methods has also helped solve the key issue concerning the uniqueness of the partial factors calibrated from a particular ‘target case’.

Assessment of stability problems at southern engineered slopes along Mersin-Tarsus Motorway in Turkey

This paper describes the cut slope stability problems of southern engineered slopes along 57 km long Mersin-Tarsus Motorway. While the northern slopes were slipping during and following construction, the stability problems occurred at southern slopes after heavy rains in December 2001. The most recent slope stability problem took place on chainage at the km 10+800 embankment on 9 April 2009. About 3.62 × 106 m3 soil materials have currently slipped at 60 different location. After the occurrence of slides, different remedial methods (reshaping slopes, soil improvements, etc.) have been applied to stabilize the slipped slopes. The slope stability studies were carried out using back analysis to determine the slope failure mechanisms and to estimate effective shear strength parameters. Pore water pressures increase following intense rainfall events and cause reduced resistance to shear strength at the engineered slopes. In addition, the affects of the static and dynamic parameters to analyse the state of the slope after excavation were investigated and possible remedies to improve the state (toe rockfill and retaining wall) were assessed for motorway slopes through determining the slope stability with water parameter and seismic loading, separately and together. The results of the stability analysis have exhibited that a good drainage system and retaining wall prevents the motorway slope slides.

Numerical Study of Unsaturated Infinite Slope Stability regarding Suction Stress under Rainfall-induced Infiltration Conditions

Numerical stability analysis of an unsaturated infinite slope under rainfall-induced infiltration conditions was performed using generalized effective stress to unify both saturated and unsaturated conditions The soil-water characteristic curve (SWCC) of sand with a relative density of 75% was initially measured for both drying and wetting processes. The hydraulic conductivity function (HCF) and suction stress characteristic curve (SSCC) were subsequently estimated. Under the rainfall-induced infiltration conditions, transient seepage analysis of an unsaturated infinite slope was performed using the finite element analysis program, SEEP/W. Based on these results, the stability of an unsaturated infinite slope under rainfall-induced infiltration conditions was examined in relation to suction stress. According to the results, the negative pore-water pressure and water content within the slope soil changed over time due to the infiltration. In addition, the variation of the negative pore-water pressure and water content led to a variation in suction stress and a subsequent change in the slope's factor of safety during the rainfall period.

A typical weathering profile of granitic rock in Johor, Malaysia based on joint characterization

One of the most important challenges in the study of slope stability, foundation, and excavation in rocks is understanding the weathering states. This issue is more important in tropical climates, where severe weathering produces thick weathering profiles. Thick weathering profiles are normally classified or graded differently based on some field observations, geological studies, and material properties of rock. This paper considers the relationship between joint characterization and the state of weathering of granitic rock as an important factor to describe the mass weathering. A total of 24 panels of rock exposures was studied in two active granite quarries located in Johor, Malaysia. This region has a tropical climate condition. A typical profile was proposed for granitic rock, mainly based on joint characterization, topography, and geological condition. This profile includes a common weathering ranging from fresh rock to residual soil. Based on the presence of corestones, two additional subgrades were introduced in completely and highly weathered zones. It is believed that the proposed weathering profile may contribute to engineering design and classification of weathered granitic rock in tropical region.

Study of Luming Molybdenum Mine West Zone EH4 Geophysical Prospecting and the Geological Structure Influence on Slope Stability

As the geological condition of western Luming molybdenum mine is broken and there are faults through, to find out the geological structures of west mine is quite significant for the study of Luming mine slope stability. With EH4 geophysical technology to detect west Luming molybdenum geological condition, the data of the detection point was collated and sorted out, through the inversion method, two faults F3 and F4 was inferred in the west zone of LuMing mine, which is likely to cause slope instability phenomena. What is more, at the northwest of the pit, lithology with water was composed of alluvial deposits and broken sediments, the depth of the strata with water is more than 80 miles. So the impact of water on slope stability should be fully considered during mining process.

Analysis of Rainfall Infiltration Law in Unsaturated Soil Slope

In the study of unsaturated soil slope stability under rainfall infiltration, it is worth continuing to explore how much rainfall infiltrates into the slope in a rain process, and the amount of rainfall infiltrating into slope is the important factor influencing the stability. Therefore, rainfall infiltration capacity is an important issue of unsaturated seepage analysis for slope. On the basis of previous studies, rainfall infiltration law of unsaturated soil slope is analyzed. Considering the characteristics of slope and rainfall, the key factors affecting rainfall infiltration of slope, including hydraulic properties, water storage capacity (θ s - θ r), soil types, rainfall intensities, and antecedent and subsequent infiltration rates on unsaturated soil slope, are discussed by using theory analysis and numerical simulation technology. Based on critical factors changing, this paper presents three calculation models of rainfall infiltrability for unsaturated slope, including (1) infiltration model considering rainfall intensity; (2) effective rainfall model considering antecedent rainfall; (3) infiltration model considering comprehensive factors. Based on the technology of system response, the relationship of rainfall and infiltration is described, and the prototype of regression model of rainfall infiltration is given, in order to determine the amount of rain penetration during a rain process.

Drilling cores on the sea floor with the remote-controlled sea floor drilling rig MeBo

Abstract. The sea floor drill rig MeBo (acronym for Meeresboden-Bohrgerät, German for sea floor drill rig) is a robotic drill rig that is deployed on the sea floor and operated remotely from the research vessel to drill up to 80 m into the sea floor. It was developed at the MARUM Research Center for Marine Environmental Sciences at Bremen University. The complete system – comprising the drill rig, winch, control station, and the launch and recovery system – is transported in six containers and can be deployed worldwide from German and international research ships. It was the first remote-controlled deep sea drill rig to use a wireline coring technique. Compared to drilling vessels this technology has the advantage of operating from a stable platform at the sea bed, which allows for optimal control over the drilling process. Especially for shallow drillings in the range of tens to hundreds of metres, sea bed drill rigs are time-efficient since no drill string has to be assembled from the ship to the sea floor before the first core can be taken. The MeBo has been successfully operated, retrieving high-quality cores at the sea bed for a variety of research fields, including slope stability studies and palaeoclimate reconstructions. Based on experience with the MeBo, a rig is now being built that will be able to drill to a depth of 200 m.

Numerical Simulation Method to Analysis of Strengthening Effect in the ZhongLong Park

Landslide is a kind of global geological disasters, causing casualties and huge economic losses to many countries and regions. Analysis on the study of slope stability is very important geotechnical engineering in the field of content. Taking Dalian Xinghai long garden landslide as an example, based on the detailed investigation of geological disasters in Dalian Xinghai area, using the Soilworks software to analyse evaluation of landslide treatment effect.

Study of the Influence Factors of Soft Rock Slope Stability based on the Statistical Analysis

The stability of the slope influenced by numerous factors, of which many are difficult to determine, and difficult to estimate, and they are not only random but also fuzzy. Based on the structure characteristics of soft rock slope breaking the instability, the paper makes the statistic analysis of the influence factors of soft rock slope stability, obtained the three influence factors of rebound strength, side slope grade, slope SMR value, and on the basis of the obtained impact factors, this paper also puts forward some reasonable suggestions on test and theoretical research of strengthening soft rock environment effect and time effect, constantly improve the soft rock slope stability analysis method, and strengthen the mixed study of soft rock slope stability with other disciplines.

The Records of Slope Reinforcement Engineering in a Loess City

This article selected a typical loess slope engineering as the research object, and through the characteristics of loess landslide, landslide environmental geological conditions, the formation mechanism of the landslide study of the loess area of urban slope instability factors, loess slope stability of the calculation method and reinforcement measures. This paper adopts the theory of Morgenstern-Price to analyzing the stability of the slope, referencing with Sweden finite slice method, Simplified Bishop method, Simplify Janbu method. The reinforcement adopts the technology of possessed anchor to disposing the loess slope, and has good Practice effect. The loess slope stability study area has a large reference.

The Records of Slope Reinforcement Engineering in a Loess City

This article selected a typical loess slope engineering as the research object, and through the characteristics of loess landslide, landslide environmental geological conditions, the formation mechanism of the landslide study of the loess area of urban slope instability factors, loess slope stability of the calculation method and reinforcement measures, the loess slope stability study area has a large reference.

A new slope mass rating in mountainous terrain, Jammu and Kashmir Himalayas: application of geophysical technique in slope stability studies

The slopes of western Lesser Himalaya (at Sangaldhan Block of Udhampur near Ramban, Jammu and Kashmir India) are being severely affected by tectonic and erosional activities. These activities result in deposit of a thick cover of rock fragments and overburden just above the hard rock. The thickness of overburden cover has directly affected the stability of slope in the study area, though the traditional stability estimation techniques, rock mass rating and slope mass rating, rate this area as moderately stable which does not represent the real stability condition. In this research work, the geotechnical and geophysical surveys have been carried out to reckon the slope stability conditions more accurately as compared to traditional slope stability estimation techniques. A new rating, new slope mass rating, is developed, which gives a better picture of the stability of slopes. It incorporates a new parameter of overburden thickness profile, along with slope angle and other associated factors on the slopes of the mountainous terrains. The vertical electrical sounding surveys were conducted for the demarcation of rock–overburden interface and for determining the overburden cover. This new classification depicts an increase of 12.84 % in unstable slope areas giving a better assessment and factual picture of slope stability in our study area. This study also enumerates the importance of geophysical applications in slope stability studies. The research work is applicable in mountainous terrains such as Himalaya, and the major component of the application is the orientation of overburden or the profile of thickness in relation with slope of surface.

A Study of High Slope Stability of Yangfanggou Dam Site

The engineering geological conditions of the slope of Yangfanggou dam site are firstly analyzed. From the perspective of valley evolvement, the distinct element model of Yangfanggou river valley is established based on the investigated geological data. On the basis of the model established, the results of stress in slope are calculated by introducing the software of UDEC. According to simulation results, the basic law of stress and plastic zone is concluded as follows: Stress field appears as four sub zones including the original zone of stress, the relaxation zone of stress, the concentration zone and the transition zone of stress; the horizontal depth of the plastic zone calculated is about 10 m∼30 m, and the developing depth in left bank slope is larger than depth in right bank slope. Simulation results are consistent with the actual geological conditions at the dam site. The coefficient of slope stability is calculated by adopting the method of strength reduction, and the value is 1.89. There is a sliding block at the right bank slope in the limit state.

Study on the Reliability of Loess Cutting Slope Considering the Variability of Soil-Water Characteristic Parameters

The complexity of the geological conditions and the non-uniformity of geotechnical material make the study of slope stability with big uncertainties, so it is necessary to analyze the reliability of slope. In this paper, firstly, the matrix suction of Malan loess in Gansu Province is measured by tension meter, and a fitted soil-water characteristic curve (SWCC) is obtained according to the empirical formula; then SWCC parameters of Malan loess such as a, n and θs (saturation volumetric water content) are thought as random variables, the method of simplified Bishop is used to calculate of slope stability, and the reliability of cutting slope of Malan loess is analyzed according to Rosenbleuth method. Through calculating, obtain mean factor of safety, failure probability and reliability index of the slope. After analyzing the relations between mean factor of safety, failure probability, reliability index and variability of parameters, the results show that, the factor of safety is 1.005 and it is stable when the variability of SWCC parameters are not considered. When variation coefficients of a, n and θs are all 0.3, the average factor of safety is 1.051, the reliability index is 10.94 and failure probability is 29.81%. It is obvious that variability of SWCC parameters has certain influence on stability of the slope. In parameters of SWCC, comparing with a and θs, the variability of n has the most important influence on the mean factor of safety and failure probability. But the corresponding reliability index is minimum (the change ratios of the mean factor of safety， failure probability and reliability index with variation coefficient of n are 0.37，3.247 and 282.0 respectively). So variation level of n should be specially taken into account in reliability analysis of the slope. This research provides an important basis for the determination of the SWCC parameters of Malan loess, the stability calculation, stability estimation and prevention sliding of loess cutting slope caused by rainfall.

Study on the Reliability of Loess Cutting Slope Considering the Variability of Soil-Water Characteristic Parameters

The complexity of the geological conditions and the non-uniformity of geotechnical material make the study of slope stability with big uncertainties, so it is necessary to analyze the reliability of slope. In this paper, firstly, the matrix suction of Malan loess in Gansu Province is measured by tension meter, and a fitted soil-water characteristic curve (SWCC) is obtained according to the empirical formula; then SWCC parameters of Malan loess such as a, n and θs (saturation volumetric water content) are thought as random variables, the method of simplified Bishop is used to calculate of slope stability, and the reliability of cutting slope of Malan loess is analyzed according to Rosenbleuth method. Through calculating, obtain mean factor of safety, failure probability and reliability index of the slope. After analyzing the relations between mean factor of safety, failure probability, reliability index and variability of parameters, the results show that, the factor of safety is 1.005 and it is stable when the variability of SWCC parameters are not considered. When variation coefficients of a, n and θs are all 0.3, the average factor of safety is 1.051, the reliability index is 10.94 and failure probability is 29.81%. It is obvious that variability of SWCC parameters has certain influence on stability of the slope. In parameters of SWCC, comparing with a and θs, the variability of n has the most important influence on the mean factor of safety and failure probability. But the corresponding reliability index is minimum (the change ratios of the mean factor of safety， failure probability and reliability index with variation coefficient of n are 0.37，3.247 and 282.0 respectively). So variation level of n should be specially taken into account in reliability analysis of the slope. This research provides an important basis for the determination of the SWCC parameters of Malan loess, the stability calculation, stability estimation and prevention sliding of loess cutting slope caused by rainfall.