Slip Circle Research Articles

Monitoring Surface Deformations in a Fossil Landslide Zone and Identifying Potential Failure Mechanisms: A Case Study of Gümüşhane State Hospital.

The escalating occurrence of landslides has drawn increasing attention from the scientific community, primarily driven by a combination of natural phenomena such as unpredictable seismic events, intensified precipitation, and rapid snowmelt attributable to climate fluctuations, compounded by inadequacies in engineering practices during site selection. Within the scope of this investigation, contemporary geodetic techniques using the GNSS were employed to monitor structural and surface deformations in and around a hospital edifice situated within an ancient fossil landslide region. Additionally, inclinometer measurements facilitated the determination of slip circle parameters. A subsequent analysis integrated these datasets to scrutinize both the hospital structure and its surrounding slopes. In addition to the finite element method, four different limit equilibrium methods (Bishop, GLE-Morgenstern-Price, Spencer, and Janbu) were used in the evaluation of stability. Since the safety number determined in all analyses was <1, it was determined that the slope containing the hospital building was unstable. The movement has occurred again due to the additional load created by the hospital building built on the currently stable slope, the effect of surface and groundwater, and the improperly designed road route. As a result of geodetic monitoring, it was determined that the sliding speed on the surface was in the N-E direction and was approximately 3 cm, and this situation almost coincided with inclinometer measurements.

Geophysical and numerical approaches to solving the mechanisms of landslides triggered by earthquakes: A case study of Kahramanmaraş (6 February, 2023)

Many landslides occurred in the 11 Turkish provinces affected by the earthquakes centered in Kahramanmaraş in February 2023, and many people lost their lives due to those landslides. To reduce the risks and hazards brought on by landslides induced by earthquakes, it is essential to identify the mechanisms causing landslides to arise in such situations. In this study, the geological strength index and both seismic refraction tomography and electrical resistivity tomography (ERT) geophysical methods were used to determine the failure mechanism of layered sedimentary units defined as flysch (claystone-siltstone-sandstone-marl). The shear strength reduction finite element method (SSR-FEM) was used with the RS2 computer program for model solutions. One of the geophysical methods, ERT, facilitated an interpretation of the cyclic failure mechanism that occurs in flysch, and it was found to be congruent with numerical models. Landslide slip circle depth, water-saturated layers, and resistivity values were determined with the ERT method. Seismic methods were employed to determine the velocity values (Vp, Vs) of the landslip mass. These velocity data, along with the elasticity modulus and Poisson ratios derived from them, were utilized in our numerical model. In the maximum shear strength and horizontal displacement analyses performed on the section line determined before the landslide, the natural state and the situation under the influence of groundwater were examined and the strength reduction factor (SRF) was determined as 1.35 and 1.24, respectively. In an evaluation conducted under the influence of the maximum horizontal ground acceleration (0.22 g) determined by taking into account the seismicity of the study area, it was concluded that instability occurred in the flysches and the SRF value was 0.72. An important finding of this study is that the results of geophysical methods used to determine the lithological properties of sedimentary rock masses and understand the causes of landslides align closely with those of numerical analysis methods, providing high accuracy. These methods also support new approaches, particularly in identifying landslip boundaries and detecting areas with high water saturation. It has been discovered that earthquakes actively contribute to the instability of these kinds of soils.

Stability Analysis of Homogenous Embankment using Statistical Method

Homogeneous earth embankments are man-made or artificial structure whose construction is an important part of highway, railway and flood structure projects. Soil exhibits different properties in different places. Reinforcing the soil with Geogrid can be effectively used for improving the durability and stability of embankment, this ensures uniform settlement of embankment and result in cost effective solution. This paper aims to develop two-dimensional stability charts and correlation for slope failure (slip circle) in homogeneous soil embankment. Sensitivity analysis is also done to determine the contribution of different soil parameter. The chart and correlation developed for stability analysis can be a convenient tool for preliminary estimation of factor of safety (FOS) and possibility of failure.

Stability Analysis of Anchor-Reinforced Soil Slopes with Taylor’s Stability Chart

The stability of earth slopes can be enhanced by introducing an anchoring system. The factor of safety of an anchor-reinforced slope is one of the essential items required to evaluate stability. This parameter can be predicted using limit equilibrium and numerical approaches by relevant software. Taylor’s stability chart has been frequently used to estimate the factor of safety of an unreinforced homogeneous cohesive-frictional soil slope. An analytical expression was developed in this study based on the friction circle method by which the factor of safety of anchor-reinforced slopes can be predicted using Taylor’s chart. The anchor-reinforced slope considered in the analysis consisted of homogeneous cohesive-frictional soil. The analyses were carried out considering different slope inclinations, anchor loads, anchor orientations, and slip circles. An illustrative example explained the procedure for finding the factor of safety and showed how the developed method could be used by practicing engineers. A comparison between the factor of safety estimated by Taylor’s chart and the limit equilibrium method using SLIDE indicates a good agreement.

Understanding the Structural Stability of the Tehri Dam: A Comprehensive Analysis

The Tehri dam is the highest dam in India. The height of dam is 260 m. It is situated on the Himalayan region which is in earthquake prone region. A Sengupta in 2006 found that the predicted deformation due to an M=7.0 earthquake are not large enough to compromise the safety of the dam. However the deformation predicted by Seed and Makdisi’s method, and Bureau’s method for an M=8.5 earthquake are large enough to compromise the safety of dam. The Seed and Makdisi’s procedure predicted the maximum deformations, while the minimum deformations are computed by Jansen’s method. In the present work, the stability analysis four type of analysis such as structural stability analysis, Centre of slip circle by genetic algorithm, stability of dam under sudden draw down condition and dynamic analysis are considered Structural stability analysis have done by Fellenius method and radial slice method. In Fellenius method three number of slip circles are taken which cuts the slope at two third distances from top of slope. By finding the resisting moment and driving moment the factor of safety is found that for first slip circle, second slip circle and third slip circle are 1.997, 2.103 and 2.045 respectively. In the radial slice method the failure wages are divided into number of slice radially by joining the line from the center of slip circle to the arch. The factor of safety is found as 1.15. The coordinate of centre of slip circle has found by genetic algorithm. In order to validate the genetic algorithm method, the input data has been imported from the results of graphical method. The centre coordinate of slip circle is obtained as (210,485) which was found to be very close the value of centre of slip circle by graphical method. Numerical analysis has been made by using commercially available software PLAXIS under sudden draw down condition. The deformation in X-direction was 16.99 m. Dynamic analysis has been used by PLAXIS software and the total deformation is obtained as 0.4150 m.

Coupled Lateral and Longitudinal Controller for Over-Actuated Vehicle in Evasive Maneuvering With Sliding Mode Control Strategy

Coupled controllers are vital for safely handling vehicles, especially in critical driving situations that include changing lanes to avoid obstacles. Controllers specialized in emergencies must keep road users safe in critical situations. In this paper, we develop the coupled controller to handle evasive maneuvers for an over-actuated vehicle. The controller is based on the second-order sliding mode control theory. We use the bicycle model to establish the equivalent and robust steering equations as a control-oriented model. The lateral and longitudinal vehicle motions are coupled to each other by the lateral vehicle information on the longitudinal sliding surface, and the dependence of the lateral sliding surface on the longitudinal velocity. The torque vectoring method based on fuzzy logic adjusts the yaw moment. We address the tire slip circle on the slip controller to stabilize the vehicle while maneuvering. We simulate and evaluate our controller in a rear-end collision situation with a short time window to maneuver the vehicle. The ego vehicle detects the preceding vehicle and performs an evasive lane change while simultaneously applying brakes to bring the vehicle to a halt. Our research is the earliest in providing an ultimate emergency control to successfully avoid crashes up to 130 km/h in short time crash detection.

Geotechnical Stability Analysis of the Quay Wall of Military Port Ksar Sghir, Morocco

This article consists in establishing a geotechnical stability study of the -4m/zh quay belonging to the Ksar Sghir Port. First of all, using the TALREN software for verification against large slips. the study presents a verification of the stability for the rear slope slip circles and for the front slope slip circles in the static case. Secondly, stability was determined for the back slope slip circles and for the front slope slip circles in the seismic case. Moreover, PLAXIS software was used to model the displacements and constraints in the structure. Following the results of the safety coefficients, we notice that the stability of the structure gives acceptable values. In addition, the soil does not reach breaking stress. The total mean stress and total displacement mostly impacted the surface area that is related to external impact.

3D numerical simulation of slope-flexible system interaction using a mixed FEM-SPH model

Flexible membranes are light structures anchored to the ground that protect infrastructures or dwellings from rock or soil sliding. One alternative to design these structures is by using numerical simulations. However, very few models were found until date and most of them are in 2D and do not include all their components. This paper presents the development of a numerical model combining Finite Element Modelling (FEM) with Smooth Particle Hydrodynamics (SPH) formulation. Both cylindrical and spherical failure of the slope were simulated. One reference geometry of the slope was designed and a total of 21 slip circles were calculated considering different soil parameters, phreatic level position and drainage solutions. Four case studies were extracted from these scenarios and simulated using different dimensions of the components of the system. As a validation model, an experimental test that imitates the soil detachment and its retention by the steel membrane was successfully reproduced.

Geometric and Material Variability of the Probability of Landward Slope Failure for Homogeneous River Levees

Holistic flood risk management (FRM) aims at minimizing the flood risk (FR) for an entire river basin. To this end, the probability of flooding and its consequences must also be taken into account in the planning of flood risk management measures. If the FR is to be limited by the flooding probability value (e.g., by changing the structural reliability), knowledge of the variability of the limit state is required. As an example, this study quantifies for the first time the variability of the probability of a landside slope failure on homogeneous river levees, using the Monte Carlo simulation. In the slip circle method developed by Krey that is used for this purpose, four geometric and six material input parameters are included as being uncertain, of which four emerge in the result as being relevant influencing variables of the failure probability. These analyses extend our understanding of landward slope failure by the variability of the limit state; the results allow a targeted adjustment of the local failure probability to limit the flood risk. In the future, the methodology presented is to be supplemented by the integration of parameter dependencies and, once in use, expanded to include structured cross-sections or additional failure mechanisms.

Estimating the Basal Heave Stability of Narrow Braced Excavations

Engineering practices indicate that narrow braced excavation exhibits a clear size effect. However, the slip circle method in the design codes fails to consider the effect of excavation width on basal heave stability, causing waste for narrow excavation. In this paper, numerical simulation for basal heave failure of excavation with different widths was performed by FEM with SSRT (shear strength reduction technique). The results revealed that the failure mechanism of narrow excavation is different from the complete slip circle mode. In addition, the safety factor decreases increasingly slowly as the excavation widens and stabilizes when approaching the critical width. Subsequently, the corresponding computation model was presented, and an improved SCM (slip circle method) was further developed. Finally, the engineering case illustrated that it can effectively optimize the design, which exhibits clear superiority.

A spreadsheet based stability calculation for geosynthetic reinforced column-supported embankments

Design procedures for Geosynthetic Reinforced Column-Supported (GRCS) embankments should consider both internal stability arising from failure of single columns and external stability arising from failure of the embankment as a whole unit. A number of possible failure mechanisms for external stability due to slip circle failure and sliding failure of group of columns as a single unit are discussed in the literature. However, internal stability issues due to failure of individual columns have not been received much attention. Therefore, an in-depth understanding of individual column failure and subsequent progressive failure of embankments is an important topic, which needs attention when investigating the stability of GRCS embankments. In this paper, two-dimensional finite element modelling incorporating strain-softening behaviour of cement mixed soils has been used to identify the individual column failure of GRCS embankments at the Ultimate Limit State. Results show that the bending failure of individual columns progressively leads to develop a failure plane within the column improved ground causing internal stability issues. For the identified failure mode, an analytical equation is proposed to calculate the factor of safety against shear failure due to progressive bending failure of columns based on the Coulomb’s wedge theory. Since the proposed approach can be conveniently implemented in an EXCEL spreadsheet program, it is useful for practicing geotechnical engineers.

Reliability analysis of a cohesive slope in a spreadsheet using FOSM, FORM and Monte-Carlo Simulation

In geotechnical engineering uncertainties arises from loads, soil characteristics and their properties, calculation models etc. To minimize these uncertainties in geotechnical problem, various reliability based and (or probabilistic based) approaches have been developed. This abstract presents a MS-Excel spreadsheet environment based practical framework for estimating the reliability index and failure probability of a cohesive finite slope using First-order second moment method, First-order reliability method and Monte Carlo Simulation. The height and the angle of slope is considered to be 5 m and 45º respectively. The inclination of the slope is 2H:1V and the hard stratum is assumed to be present at 15 m below the soil. The values of saturated unit weight and undrained shear strength are assumed to be 18 kN/m3 and 20 kPa respectively. The stability analysis is carried out using Swedish slice method under undrained condition. The excel spreadsheet developed in the study is mainly divided into two forms i.e. deterministic model worksheet for calculating the factor of safety and uncertainty model for generating the random variables of uncertain parameters. The undrained shear strength is considered as an uncertain parameter. The nominal factor of safety value is found out to be 1.248 and the critical slip circle has coordinate (2.6, 8.8), having radius of 16 m. The reliability index is found out using FOSM, FORM and MCS.

Physics and Modeling of Various Hazardous Landslides

In 2014, the Varnes classification system for landslides was updated. Complex landslides can still be a problem to classify as the classification does not include the flow type in the hydrodynamical sense. Three examples of Icelandic landslides are presented and later used as case studies in order to demonstrate the methods suggested to analyze the flow. The methods are based on the different physical properties of the flow types of the slides. Three different flow types are presented, named type (i), (ii), and (iii). Types (i) and (ii) do not include turbulent flows and their flow paths are sometimes independent of the velocity. Type (iii) include high velocity flows; they are treated with the translator wave theory, where a new type of a slope factor is used. It allows the slide to stop when the slope has flattened out to the value that corresponds to the stable slope property of the flowing material. The type studies are for a fast slide of this type, also a large slip circle slide that turns into a fast-flowing slide farther down the path and finally a large slide running so fast that it can run for a kilometer on flat land where it stops with a steep front.

The Bearing Capacity Evaluations of a Spread Footing on Single Thick Stratum or Two-Layered Cohesive Soils

Nowadays many countries plan to increase the percentages of renewable energies by developing offshore wind power. Due to the large sizes of offshore foundations, such as spudcan footings of jack-up barges or pile anchors of wind turbines, the affected soil depth range caused by the foundation under loading can be relatively deep, so the affected range may include a single thick layer or stratified soils. This paper utilizes limit analysis and FLAC numerical simulation to investigate the bearing capacity of a footing on single thick stratum or two-layered cohesive soils. Under nature deposition condition, the undrained shear strength of most cohesive soil approximately increases linearly as the depth increases. The closed-form upper bound solutions of fully rough or fully smooth footings on thick cohesive soils are provided, for the purpose of fast evaluations in practical engineering, and the outcomes are within the results from the FLAC simulation and slip circle method. The problems of punch-through shear failure or soil squeezing could be critical for two-layered soils under some conditions, and the associated bearing factors and the failure mechanisms from different methods are demonstrated and discussed in the article.

Substructure reinforcement study of Cisomang bridge at Purwakarta-Bandung-Cileunyi toll road, West Java Province, Indonesia

At the end of 2016, significant displacement occurred at P2 pier of Cisomang Bridge at Purwakarta-Bandung-Cileunyi toll road KM 100+700, West Java. The shift of pier is caused by the movement of soil under the substructure that has been indicated since 2012. P2 pier is constructed over clay shale. Clay shale has characteristics when in dry condition, the soil has high shear strength, but when the soil absorbs water or expose in open air, the soil loses its strength. P2 pier displacement results in extreme structural damage, so immediate handling is needed to stop the shifting of the pier. Analysis and reinforcement study are carried out using finite element method. Based on analysis, it is discovered that the existing slope stability safety factor of P2 pier is 1.09, indicating that the soil movement can occur if the clay shale is disrupted. Reinforcement is designed to mitigate the shift of the P2 pier by adding 38 pile foundations to the existing foundation configuration. Each pile has diameter of 1.2 meter with a depth of ±30 meter across the existing slip circle. Reinforcement increases the slope stability safety factor to 1.25, indicating that the P2 pier after reinforcing is in safe condition.

永山 功著「円弧すべり法による法面の安定解析に対する理論的再考察」に対する討議

永山 功著「円弧すべり法による法面の安定解析に対する理論的再考察」に対する討議

Optimization of Embankment Widening with Different Soils

Due to increasing in the population and vehicular volume the existing roads are becoming inadequate. To overcome this problem, widening of existing roads or embankments are obtained, which required a huge amount of soils of suitable properties but due to industrialization and urbanization the availability of good soils are getting reduced because of which the construction should be carried out with unsuitable or weaker soils of inadequate properties and also the widening process involves accumulation of large land area which results in uneconomic of project. In this study three different soils are considered to analyze the influence of weaker soils on embankment widening which involves the stability analysis and reinforcement contribution analysis. Also study involves optimization of embankment widening using Different embankment sections with different slope angles ( via 1V:1H, 2V:1.5H, 2V:1H and 2.5V:1H ) and geo-synthetic reinforcement, which results in reductions of additional land required and backfill material but ensuring minimum factor of safety of 1.5. The analysis performed based on Limit equilibrium methods using SLOPE/W software. The results shows that the reinforcement mobilizes the stabilizing force in embankment which increases the stability and corresponding factor of safety of embankment and for the reinforced section the factor of safety value is a contribution of both reinforcement and shifted critical slip circle and percentage of contribution depends upon slope angle, soil properties &amp; reinforcement. The cost analysis of embankment widening with different soils and different slope angles shows that steep section is the most economical section in all the cases.

Prediction of the sliding type and critical factor of safety in homogeneous finite slopes

In this paper, the effect of soil material parameters including soil specific weight (γ), cohesion (C), angle of internal friction (emptyset), and geometric parameter of slope including angle with the horizontal (β) for a constant slope height (H) on factor of safety (Fs) was investigated. Fs was considered in two scenarios: (1) slope with dry condition, and (2) with steady-state saturated condition that comprises water level drawdown circumstances. In addition, the type of slip circle was also investigated. For this purpose, the SLOPE/W software as a subgroup of Geo-Studio software was implemented. Results showed that decreasing of water table level and omitting the hydrostatic pressure on the slope consequently would result in safety factor decrement. Comparison of the plane and circular failure surfaces showed that plane failure method produced good results for near-vertical slopes only. Determination of slip type showed that for state (30° < β < 45°), the three types of failure circles (toe, slope or midpoint circle) may occur. For state (45° < β < 60°), two modes of failure may occur: midpoint circle and toe circle. For state (β > 60°), the mode of failure circle is only toe circle. Linear and nonlinear regression equations were obtained for estimation of slope safety factor.

Wall Deflection and Ground Surface Settlement due to Excavation Width and Foundation Pit Classification

Foundation pits have obvious spatial effect, and the lateral wall deflection, ground movement and basal heave stability are closely related with the excavation width. A database of 92 case histories with extensive excavation widths in soft soil in China are collected and analyzed. The maximum lateral wall deflections and maximum ground surface settlements measured are smaller than the case histories there before. With the increase of excavation width, the maximum lateral wall deflections and the maximum ground surface settlements increase firstly and then tend to stable. The database indicates that the type of retaining structure has little relevance to the excavation width of the foundation pit. There are two types of basal heave according to the excavation width, single-peak and double-peak. Three types of foundation pit considering excavation width, named wide foundation pit, normal foundation pit and narrow foundation pit, are proposed based on the slip circle basal heave analysis approach. The classification method is consistent with the measured data and the simulated results.

Theoretical Consideration on Statically Indeterminate Force between Slices in Fellenius&apos; Slip Circle Method

Theoretical Consideration on Statically Indeterminate Force between Slices in Fellenius&apos; Slip Circle Method