Horizontal Slice Method Research Articles

Upper-Bound Limit Analysis of the Multi-Layer Slope Stability and Failure Mode Based on Generalized Horizontal Slice Method

Upper-Bound Limit Analysis of the Multi-Layer Slope Stability and Failure Mode Based on Generalized Horizontal Slice Method

Seismic stability of expansive soil slopes reinforced by anchor cables using a modified horizontal slice method

Seismic stability of expansive soil slopes reinforced by anchor cables using a modified horizontal slice method

The Use of the Horizontal Slice Method to Determine the Pseudostatic Coefficient in Two-Tiered Geogrid and Metal Strip–Reinforced Soil Walls

The Use of the Horizontal Slice Method to Determine the Pseudostatic Coefficient in Two-Tiered Geogrid and Metal Strip–Reinforced Soil Walls

A general kinematic approach to the seismic stability assessment of slopes

Most of the current studies concerning slope stability assume a toe failure mechanism, which fails to capture the full complexity of slope collapse. In this study, a more comprehensive approach is developed for analyzing seismic slope stability by defining an instability behavior coefficient that considers different failure patterns, including toe, face, and base failure. The proposed coefficient is integrated with a kinematic method of limit analysis to establish a three-dimensional (3D) collapse mechanism that can describe all possible instability behaviors. The impact of earthquake forces on instability behaviors and slope stability is assessed in a modified pseudodynamic manner, which is capable of accounting for the spatiotemporal feature of seismic acceleration. A horizontal slice method is executed for calculating earthquake-induced work rates, as well as a double integral technique to compute dissipation rates due to soil resistance along the sliding surface and work rates generated by soil weight. By applying the principle of energy conservation, the lower-bound solutions of stability numbers are derived, and a further critical solution can be obtained by the combination of the Marine Predators Algorithm and the Nelder-Mead Simplex Algorithm. The proposed method is confirmed to be accurate and effective through comparisons with previous solutions. In addition, a parametric study reveals the effect of the dynamic characteristics of seismic waves on slope stability and instability behaviors. The general approach developed in this study offers a more comprehensive and accurate way to assess seismic slope stability.

Influence of Soil Suction and Seismic Excitation on Active Earth Pressure

Earthquake-induced slope failures are common occurrences in engineering practice. The rigid gravity retaining wall remains an effective technique in maintaining the slope stability. Based on the pseudo-dynamic approach, the seismic response of unsaturated backfills is studied using the kinematic limit analysis method. To formulate the energy balance equation, a horizontal slice method is proposed. The work rates of unsaturated soil gravity, seismic inertia force and damping force that are all characterized with conspicuous nonlinear distribution characteristics are computed using this method. A series of parametric analysis is conducted regarding the influences of soil suction and seismic excitations on the earth pressure estimations. The results show that the suction effect relates not only to the soil types but also the seismic excitations. The earth pressure is overestimated by 15%–32% when soil suction is not considered in the analyses. For hard backfills, the peak active earth pressure increases slightly and moves towards the negative direction.

Kinematic horizontal slice method for uplift capacity analysis of plate anchors in nonhomogeneous soils with a nonlinear failure criterion

The reliable estimation of uplift capacity of plate anchors becomes necessary for the safe and cost-effective design of various structures against uplift loads. Uplift capacity studies have traditionally been conducted using semi-analytical methods based on plasticity theories, and the previous research has primarily focused on homogeneous soils and a linear failure criterion. Soils, in general, are nonhomogeneous and exhibit nonlinear shear strength behavior. The present study proposes a novel kinematic horizontal slice method within the context of plasticity theory to determine the vertical uplift capacity of various shapes of plate anchors in nonhomogeneous soils using the nonlinear power-law failure criterion. A linear variation of parameters such as initial cohesion, tensile strength, nonlinear coefficient, and unit weight with depth below the ground surface was considered. The effect of nonassociativity for a general nonlinear material has been examined. A detailed parametric study was conducted to explore the effects of various parameters on the uplift capacity of anchors. The results revealed that increasing initial cohesion while decreasing tensile strength, nonlinear coefficient, and unit weight with depth below the ground surface increases anchor uplift capacity, especially for three-dimensional cases. Anchor failure patterns were also investigated for a few parameter combinations. The results of this study were found to be more consistent with those developed in the literature for some specific cases.

The Modification and the Application of Ground Pressure Calculation Model for the Shallow Tunnels under Seismic Scenario

The traditional simplified model for ground pressure calculation is widely used in the anti-seismic design of shallow tunnels. However, it presents two obvious deficiencies, which are related to the block equilibrium and the additional seismic load respectively. A modified calculation model is proposed in this article by introducing the concept of slip angle, so that the deflection of potential slip planes and the distribution of ground pressure can be considered and further discussed. By combining the horizontal slice method and graphical method, a series of explicit formulas for calculating ground pressure are presented so that the vertical ground pressure, the rupture angle, and the lateral thrust can be calculated more accurately. The proposed modified model is compared with the existing model to validate the correctness of calculation results. The results show that the explicit formula of modified model could be reduced to Liu's formula when the potential slip planes are assumed to be vertical. Additionally, the sensitivity analyses on the vertical ground pressure, block volume, and distribution pattern of the lateral thrust are carefully investigated. The lateral thrusts acting on the left and right wedges distribute logarithmically and exponentially respectively, which implies that the distribution pattern is mainly affected by the direction of earthquake inertia force, while the cohesion and the friction angle merely influence the magnitude of lateral thrust to some extent.

Application of Seismic Bedding Slice in Short to Medium Term Sequence Stratigraphy Division: A Case Study of the Sartu-Putaohua Oil Reservoir in Songliao Basin, China

Previously, stratigraphic evolution and sequence overlapping were represented by “substituting point for surface or multi-point for surface, line for surface or multi-line for surface”, making it difficult to accurately reflect the stratigraphic evolution law across a larger area. We investigate the application of the seismic horizontal slice method for medium-short term stratigraphic sequence (four level), divided into reservoir group received, based on a 450 km2 study area of three-dimensional (3D) seismic fine of the Sa-Pu formations west of the Daqing placanticline using a 50-millisecond horizontal slice. Sa-Pu oil layers can be divided into seven four-level sequences. We believe that a four-level sequence is more accurate in this application than in logging and data logging.

Active earth pressure of 3D earth retaining structure subjected to rainfall infiltration

Rainfall infiltration is a key factor that determines the active earth pressure on an earth-retaining structure. Previous investigations on the stability of earth retaining structures were mainly conducted under the assumption that the backfills was dry, saturated, or subjected to a steady unsaturated flow, ignoring the time-varying characteristics of the rainfall infiltration process. Based on the upper bound theorem of limit analysis, this study conducted a stability analysis of a three-dimensional (3D) earth retaining structure (ERS) subjected to various rainfall infiltration patterns. An analytical model that was, capable of calculating the pore water pressure distribution due to rainfall infiltration, was employed to calculate the time-dependent pore water pressure change of unsaturated soil. A horizontal slice method was employed to take into account the change of effective unit weight of soil. Afterward, an analytical expression of the active earth pressure coefficient is derived from the energy balance equation. The effects of the 3D characteristics of ERSs and rainfall patterns on the active earth pressure coefficient and the failure pattern of ERSs were investigated. It was found that compared with plain strain conditions, the 3D characteristics of ERSs lead to a lower value for the active earth pressure and better stability. The rainfall patterns not only directly determined the stability and active earth pressure of an ERS, but also played a dominant role in critical failure pattern of the ERS.

Pseudo-static internal stability analysis of geosynthetic-reinforced earth slopes using horizontal slices method

ABSTRACT In this study, the well-established pseudo-static approach along with the horizontal slices method (HSM) is employed to investigate the seismic internal stability of geosynthetic-reinforced earth slopes. Previous simple HSM analyses were based on a primary assumption stating that the normal inter-slice forces are exerted on the mid-length of horizontal sections. However, this simplifying assumption could give rise to substantial errors in the calculation of design parameters, specifically in the case of high seismic excitations or low soil strength parameters. To address this deficiency, a balancing moment is considered as a new variable to account for the corresponding eccentricity. In the current HSM, two sets of unknown variables, including horizontal inter-slice forces and shear forces along failure surface, are determined using the well-known λ coefficient and the Mohr-Coulomb failure criterion. In this new technique, the traditional ‘5N-1ʹ type of HSM analysis is reduced to a robust and rigorous ‘3N’ one with the same predictive capability. The influence of various parameters, including soil characteristics, slope geometry and different earthquake coefficients are rigorously examined. Moreover, a number of useful graphs is provided to help engineers in the preliminary seismic design of geosynthetic-reinforced earth slopes.

Arching effect and displacement on theoretical estimation for lateral force acting on retaining wall

A new approach is proposed to evaluate the non-limit active earth pressure in c–φ soil based on the horizontal slices method and limit equilibrium method, which takes into account arching effect, displacement, mobilized friction angle, tension cracks, and shear stress of the horizontal layer. The accuracy of the proposed method was demonstrated by comparing the experimental results and other theoretical methods. The comparison results showed that the proposed approach was appropriate for calculating the non-limit active earth pressure in c–φ soil and cohesionless soil. A parametric study was undertaken to access the effects of cohesion, mobilized friction angle, and shear stress of the horizontal layer for the lateral earth pressure, as well as the effects of displacement for the rupture angle and tension cracks. Moreover, by comparing calculated results of the different theoretical methods and numerical model, it indicated that the empirical formulations of the mobilized internal friction angle and soil–wall interface friction angle used to cohesionless soil were still suitable for c–φ soil.

Seismic stability of reinforced soil slopes using the modified pseudo-dynamic method

The limit equilibrium analysis through the horizontal slice method is used to study the seismic stability of reinforced soil slopes by satisfying the equilibrium of the horizontal and vertical forces as well as moments. Unlike the pseudo-static (PS) method, the pseudo-dynamic method consideres the effects of time and phase difference of the P and S waves propagation inside the soil mass. In this paper, the PS, the conventional pseudo-dynamic (CPD), and the modified pseudo-dynamic (MPD) methods are used to study the seismic stability of reinforced soil slopes. In addition, the equivalent linear method is implemented to analyze the site response for the purpose of calculating the soil dynamics parameters required for the seismic stability analysis of soil slopes via the MPD method. A MATLAB code is developed to calculate via the abovementioned methods. Using the log-spiral slip surface, this code considers the distribution of reinforcements as uniform and variable spacing. In addition, the effect of surcharge pressure on the seismic stability of the slope is included in this study. The obtained results showed that, in general, the MPD method combined with the equivalent linear analysis would produce more critical results than other methods.

Analytical solutions for the earth pressure of narrow cohesive backfill with retaining walls rotating about the top

Currently, knowledge of the failure mechanisms of narrow backfills with retaining walls rotating about the top (RT mode) is still lacking which leads to inaccurate estimations of the earth pressure. Numerical simulations using finite element limit analysis find that under the effects of backfill geometries, interface strengths, and soil properties, the upper soil layer supported by soil arching retains its integrity and the lower soil layer is sheared by multiple curved sliding surfaces in the limit state. Based on the failure mechanisms of narrow backfills, a calculation model is established which considers the soil arching effect, curved sliding surface, and cohesive soils. Analytical solutions for the earth pressure of narrow cohesive backfills with retaining walls rotating about the top are derived by using the limit equilibrium horizontal slice method. Compared with previous studies, the present method predicts the earth pressure distribution with higher accuracy. Several extensive parametric studies have also been conducted. Thus, decreasing the aspect ratio of backfills, increasing the inclined angle of natural slopes, interface strengths, and soil cohesion are beneficial for maintaining backfill integrity and reducing earth pressure against retaining walls.

Stochastic stability analysis of geosynthetic reinforced slopes subjected to harmonic base shaking

Geosynthetic reinforcement is a lucrative solution for stabilizing the recurring failure of slopes. This paper presents an efficient probabilistic approach to analyze the internal stability of geosynthetic reinforced slopes (GRSs) resting on a soil deposit subjected to harmonic base shaking. Collocation based Stochastic Response Surface (SRS) method is used for the same. The deterministic analysis is performed employing a rigorous formulation of Horizontal Slice Method (HSM) in a modified pseudo-dynamic framework. The formulation satisfies the horizontal, vertical, and the moment equilibrium equations of each slice. The algorithm is made efficient using the non-linear constrained optimization. The effect of exciting frequency of soil on the stability of GRS is examined in detail. The accuracy of the proposed probabilistic formulation is also compared with the results of the FORM. Four input parameters are considered to be random in nature namely internal soil friction angle, unit weight, ultimate tensile strength of reinforcement, and shear wave velocity of reinforced soil (GRS). The Gaussian copula is used to correlate the input random variables. The results depict that the proposed formulation is effective and precise in predicting the probability of failure (Pf) of GRSs. The performance function is evaluated only 376 times in comparison to the direct Monte-Carlo Simulation where it is evaluated at least 105 times, reducing the computation time from approximately 2 days to 25 min. To the best of author’s knowledge, the proposed method is original.

Efficient computational system reliability analysis of reinforced soil-retaining structures under seismic conditions including the effect of simulated noise

This article presents a computational reliability analysis of reinforced soil-retaining structures (RSRS) under seismic conditions. The internal stability of RSRS is evaluated using the horizontal slice method (HSM) with modified pseudo-dynamic seismic forces. Two different failure modes of RSRS are identified and their reliability indices are computed using the first-order reliability method (FORM). The critical probabilistic failure surface is identified using a three-tier optimization scheme. Reliability index of the system is computed by considering the modes of failure to be connected in series. The tension mode is found to be the most critical mode of failure. The present study identifies that the wall height (H), shear wave velocity of the soil (Vs), and predominant frequency of the input motion (ω) govern the response of RSRS. Reliability indices depend on a parameter termed as the normalized frequency (ωH/Vs) and their values decrease with an increase in the value of ωH/Vs. Increase in the damping ratio of soil, increases the value of reliability indices, especially for ωH/Vs values, which are close to π/2. The FORM suffers from few critical shortcomings such as linear assumption of limit state surface at the most probable point of failure and its ability to consider only the statistical uncertainties excluding the effect of epistemic uncertainties. This calls for sampling-based numerical techniques such as Monte-Carlo simulation (MCS) which gives more comprehensive understanding of the problem under consideration in a probabilistic framework. Thus, a computationally efficient surrogate-assisted MCS is carried out to validate the present formulation and provide numerical insights by capturing the system dynamics over the entire design domain. Adoption of the efficient surrogate-assisted approach allowed us to quantify the epistemic uncertainty associated with the system using Gaussian white noise (GWN). Subsequently, its effects on the system reliability index and probabilistic behavior of the critical parameters are presented. The numerical results clearly indicate that it is imperative to take into account the probabilistic deviations of the critical performance parameters for RSRS to ensure adequate safety and serviceability under operational condition while quantifying the reliability of such systems.

Static stability analysis of geocell-reinforced slopes

This paper presents an analytical approach to investigate the stability of geocell-reinforced slopes using the limit equilibrium method (LEM). The so-called Horizontal Slice Method (HSM) is employed to simulate horizontal geocell layers. Each geocell layer acts as a beam providing bending and shear resistance in addition to axial strength. A formula is devised by picking relevant governing equilibrium equations, fitted to the new concept employed exclusively for analysis of geocell-reinforced slopes. Parametric studies are conducted to evaluate the effects of increasing the geocell height and replacing geogrids by geocells with various heights for slopes with different characteristics. The results showed that such actions would reasonably reduce the required tension and length of the reinforcement layers, meaning that the stability condition is improved and the less lengthy reinforcement system is formed. Output values also showed dependency on the slope angle and its material properties.

Searching for Critical Slip Surface of Slope Based on Flower Pollination Algorithm

In order to determine the critical sliding surface of the slope, the most dangerous sliding surface was searched by flower pollination algorithm. First, the method is applied to the traditional vertical slice method for slope stability analysis. The results are very close to those of the Autobank program, indicating that the method can search the critical sliding surface and find the optimal solution. Then, the method is applied to the new horizontal slice method, and the results of the calculation examples are better than those given in the references, indicating that the application of the flower pollination algorithm to the horizontal slice method is reasonable, reliable and superior. The successful application of this method provides a new method for determining the most dangerous sliding surface of slope.

Simulation of Dewatering System in A Mine Shaft Using A Prototype Model Driving by Arduino Microprocessor

Dewatering is a process which is related to water removing from the excavation worksite during mining. In this research, a prototype model of shaft mine has been fabricated and the system is simulated using ultra sonic sensors and ARDUINOUNO microprocessor and a control monitor has been built by LABVIEW software to drive the system. Horizontal slice Method has been applied in calculations of water level. An extensive tests are carried out by measuring the water level inside the mine shaft and is compared to predicted data from the system. The recorded error is 0.22 % of the whole tank capacity at full load condition. A desired water level is calculated based on the desired time and this one is compared to the speed of sound with an interesting result of average error 0.00036s in time. This mechanism is absolutely passed with no modification and it has a flexibility to apply in various industrial aspects efficiently with low cost.

Determination of Active Pressure Exerted on Retaining Walls with a Circular Failure Wedge Using the Horizontal Slices Method in Cohesive-Frictional Soil

Determination of Active Pressure Exerted on Retaining Walls with a Circular Failure Wedge Using the Horizontal Slices Method in Cohesive-Frictional Soil

Pseudo-static seismic analysis of reinforced soil slopes using the horizontal slice method

In this paper, the horizontal slice method (HSM) is employed to examine the stability of reinforced soil slopes. In this method, the soil mass is divided into a series of horizontal slices, and then the stability of each slice is examined. Unlike the previous studies, the formulation presented in this paper is able to analyse any type of the sliding surface. In addition to the log-spiral slip surface, the general slip surface is also examined. The genetic algorithm (GA) optimization method is employed to find the critical slip surface. Furthermore, the distribution of reinforcements along the depth is assumed to be uniform or non-uniform. Seismic effect is considered through the pseudo-static method. The HSM is implemented through a computer program written in MATLAB. After solving the problem, the critical slip surface, the amount of force and the length of reinforcements for the purpose of slope stabilization are obtained. Finally, the results are compared with other studies. These comparisons indicate that the method presented in this paper provides accurate results. The results also demonstrate that the general sliding surface is more critical than log-spiral sliding surface, thus leading to a larger amount of required reinforcement.