scholarly journals Robust Geotechnical Design for Soil Slopes considering Uncertain Parameters

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Xuejun Zhou ◽  
Wenxiong Huang ◽  
Jie Li ◽  
Ding Chen
Keyword(s):  
Slope Failure ◽  
Signal To Noise Ratio ◽  
System Response ◽  
Soil Parameters ◽  
Main Concern ◽  
Computationally Efficient ◽  
Knee Point ◽  
Soil Slopes ◽  
Geotechnical Design ◽  
Slope Design

Designing the geometry of soil slope is an effective treatment for preventing slope failure. How to deal with the uncertainties involved in soil parameters in geotechnical design is a main concern of geotechnical engineers. In this study, a robust geotechnical design for soil slopes (RGDS) approach was proposed, in which the Uncertainty Theory was introduced to describe explicitly the uncertainties involved in soil parameters. The uncertain reliability is often used to describe the risk of slope failure. The design robustness describing the insensitivity between the variation in the system response and the variation of input uncertain soil parameters was evaluated by the signal-to-noise ratio. The objectives of this design are to maximize the design robustness, minimize the excavation cost, and guarantee the safety (maximize the uncertain reliability). Therefore, the RGDS was formulated as a multiobjective optimization, and the optimal design can be determined based on the concepts of Pareto front and knee point. The proposed RGDS approach was illustrated through a numerical case of a two-layer slope design. The numerical results indicate that the RGDS approach is not only more intuitive and easier to follow but also more computationally efficient.

Characterization of Nonlinear Rattling Behavior of a Gear Pair Through a Validated Torsional Model

2021 ◽  
Author(s):  
Ata Donmez ◽  
Ahmet Kahraman
Keyword(s):  
Piecewise Linear ◽  
Nonlinear Behavior ◽  
Severity Index ◽  
System Response ◽  
Gear Pair ◽  
Computationally Efficient ◽  
Linear Solution ◽  
Set Up ◽  
The Impact ◽  
Gear Rattle

Abstract Dynamic response of a gear pair subjected to input and output torque or velocity fluctuations is examined analytically. Such motions are commonly observed in various powertrain systems and identified as gear rattle or hammering motions with severe noise and durability consequences. A reduced-order torsional model is proposed along with a computationally efficient piecewise-linear solution methodology to characterize the system response including its sensitivity to excitation parameters. Validity of the proposed model is established through comparisons of its predictions to measurements from a gear rattle experimental set-up. A wide array of nonlinear behavior is demonstrated through presentation of periodic and chaotic responses in the forms of phase plots, Poincaré maps, and bifurcation diagrams. The severity of the resultant impacts on the noise outcome is also assessed through a rattle severity index defined by using the impact velocities.

A Novel Technique for Steam Turbine Exhaust Pressure Limitation Using Dynamic Pressure Sensors

2005 ◽  
Vol 219 (9) ◽  
pp. 925-932 ◽  
Author(s):  
M. S. Riaz ◽  
K. J. Barb ◽  
A Engeda
Keyword(s):  
Steam Turbine ◽  
Dynamic Pressure ◽  
Pressure Sensors ◽  
Operating Conditions ◽  
Strain Gauges ◽  
System Response ◽  
Main Concern ◽  
Finite Elements Analysis ◽  
Pressure Transducers ◽  
Last Stage

In this paper, a novel approach is presented to increase the operational flexibility of steam turbines. Exhaust pressure at the exit of the last-stage blades is one of the most important parameters that limit the operation of a steam turbine, especially on days with hot ambient conditions. The main concern in these off-design high-exhaust pressure operating conditions is that it can result in flow separation, which can lead to aeromechanics instabilities and thus to blade failure because of high-cycle fatigue. In the method proposed in this paper, dynamic pressure transducers are placed around the perimeter of the last-stage blade to measure the pressure variations caused by vibrating last-stage blades. This approach, which is applicable to condensing turbines only, will provide increased exhaust pressure limits through realtime monitoring of the pressure signal and thereby enable the power plant to produce more power during times of peak demand. Finite elements analysis was performed to predict the natural frequencies of the row of blades to distinguish between the synchronous and nonsynchronous modes of vibration. Strain gauges were placed on the blades to obtain the experimental frequency information of the system. Response from the dynamic pressure transducers was compared with responses from the strain gauges. An excellent agreement between the two sets of results proved the validity of the proposed method.

A Robust and Efficient Method of Designing Piles for Landslide Stabilization

2020 ◽  
Vol 26 (4) ◽  
pp. 481-492
Author(s):  
Yang Yu ◽  
Xingmin Li ◽  
Xiaohua Pan ◽  
Qing Lü
Keyword(s):  
Efficient Method ◽  
Large Scale ◽  
Polynomial Function ◽  
Design Method ◽  
Quadratic Polynomial ◽  
Soil Parameters ◽  
Stabilizing Piles ◽  
Geotechnical Design ◽  
The Mean ◽  
Landslide Stabilization

ABSTRACT Stabilizing pile is a widely used method to reduce the development of large-scale landslides. Optimizing the pile geometry is a great challenge in the design of stabilizing piles with the purpose of cost-effectiveness, especially for soil strength parameters with large uncertainty. The objective of this study is to propose a robust and efficient method of designing piles for landslide stabilization with the consideration of the safety of slope, uncertainty of soil parameters, and cost of stabilizing piles. A new response surface, which incorporates soil parameters and stabilizing force into a quadratic polynomial function, is first proposed. Unknown coefficients of the quadratic polynomial function are solved with a numerical method at typical sampling points. Based on the solved quadratic polynomial function, the mean and standard deviation of factor of safety (FOS) of the pile-stabilized slope as well as the signal-to-noise factor are then calculated in order to evaluate the design robustness. A framework based on the concept of robust geotechnical design is presented, and its feasibility is illustrated by two cases of soil slopes. The results indicate that the proposed robust geotechnical design method could be used to optimize the design of landslide-stabilizing piles.

scholarly journals Quantification of landslide velocity from active waveguide–generated acoustic emission

2015 ◽  
Vol 52 (4) ◽  
pp. 413-425 ◽  
Author(s):  
Alister Smith ◽  
Neil Dixon
Keyword(s):  
Acoustic Emission ◽  
Slope Failure ◽  
Deformation Behaviour ◽  
Slope Instability ◽  
Metal Waveguide ◽  
Soil Slopes ◽  
Order Of Magnitude ◽  
Active Waveguide ◽  
The Relationship ◽  
Better Than

Acoustic emission (AE) has become an established approach to monitor stability of soil slopes. However, the challenge has been to develop strategies to interpret and quantify deformation behaviour from the measured AE. AE monitoring of soil slopes commonly utilizes an active waveguide that is installed in a borehole through the slope and comprises a metal waveguide rod or tube with a granular backfill surround. When the host slope deforms, the column of granular backfill also deforms and this generates AE that can propagate along the waveguide. Results from the commissioning of dynamic shear apparatus used to subject full-scale active waveguide models to simulated slope movements are presented. The results confirm that AE rates generated are proportional to the rate of deformation, and the coefficient of proportionality that defines the relationship has been quantified (e.g., 4.4 × 105 for the angular gravel examined). It is demonstrated that slope velocities can be quantified continuously in real time through monitoring active waveguide–generated AE during a slope failure simulation. The results show that the technique can quantify landslide velocity to better than an order of magnitude (i.e., consistent with standard landslide movement classification) and can therefore be used to provide an early warning of slope instability through detecting and quantifying accelerations of slope movement.

scholarly journals TO CONTROL OR NOT TO CONTROL: HOW DO WE LEARN MORE ABOUT HOW AGRONOMIC INNOVATIONS PERFORM ON FARMS?

2017 ◽  
Vol 55 (S1) ◽  
pp. 303-309 ◽  
Author(s):  
RIC COE ◽  
JOYCE NJOLOMA ◽  
FERGUS SINCLAIR
Keyword(s):  
Crop Yield ◽  
Real World ◽  
Crop Management ◽  
Maize Yield ◽  
Scaling Up ◽  
System Response ◽  
Main Concern ◽  
The Real ◽  
Important Variation ◽  
The Impact

SUMMARYOur paper ‘Loading the dice in favour of the farmer: reducing the risk of adopting agronomic innovations’ revealed mean increases but also large variation in the impact of four agroforestry practises on maize yield, as experienced by farmers in Malawi. This prompted a response from Sileshi and Akinnifesi that was critical of the data and methods used. Their main concern was that farmers did not necessarily manage crops identically in plots with and those without trees, so the yield differences that we measured may be partly caused by these differences in crop management. We argue here that it is valid and useful to look at the actual effect on crop yield of farmers having trees intercropped with maize, rather than controlling for how the crop is managed, because this is what happens in the real world. Farmers respond to having trees in their field by treating their crop differently, so this is part of the system response to having trees in fields. Attempts to eliminate this will result in measuring an artefact rather than the real impact of trees on crop yield. By doing this, we revealed important variation in the impact of trees on crop yield amongst farmers, and we argue that it is important to explore, assess and communicate to farmers and development actors the extent and implications of this variation. Understanding the contextual factors that determine who is likely to benefit most from an innovation and for whom it is less suitable can then be incorporated in scaling up, so that targeting of innovations and the appropriateness of messages given to farmers are continuously refined.

Influence of cross correlation between soil parameters on probability of failure of simple cohesive and c-ϕ slopes

2016 ◽  
Vol 53 (5) ◽  
pp. 839-853 ◽  
Author(s):  
Sina Javankhoshdel ◽  
Richard J. Bathurst
Keyword(s):  
Slope Stability ◽  
Soil Properties ◽  
Cross Correlation ◽  
Friction Angle ◽  
Probability Of Failure ◽  
Unit Weight ◽  
Soil Parameters ◽  
Design Charts ◽  
Soil Slopes ◽  
Cross Correlations

This paper focuses on the calculation of probability of failure of simple unreinforced slopes and the influence of the magnitude of cross correlation between soil parameters on numerical outcomes. A general closed-form solution for cohesive slopes with cross correlation between cohesion and unit weight was investigated and results compared with cases without cross correlation. Negative cross correlations between cohesion and friction angle and positive cross correlations between cohesion and unit weight, and friction angle and unit weight were considered in the current study. The factors of safety and probabilities of failure for the slopes with uncorrelated soil properties were obtained using probabilistic slope stability design charts previously reported by the writers. Results for cohesive soil slopes and positive cross correlation between cohesion and unit weight are shown to decrease probability of failure. Probability of failure also decreased for increasing negative cross correlation between cohesion and friction angle, and increasing positive correlation between cohesion and unit weight, and friction angle and unit weight. Probabilistic slope stability design charts presented by the writers in an earlier publication are extended to include cohesive-frictional (c-[Formula: see text]) soil slopes with and without cross correlation between soil input parameters. An important outcome of the work presented here is that cross correlation between random values of soil properties can reduce the probability of failure for simple slope cases. Hence, previous probabilistic design charts by the writers for simple soil slopes with uncorrelated soil properties are conservative (safe) for design. This study also provides one explanation why slope stability analyses using uncorrelated soil properties can predict unreasonably high probabilities of failure when conventional estimates of factor of safety suggest a stable slope.

Probabilistic Framework for Uncertainty Propagation With Both Probabilistic and Interval Variables

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Kais Zaman ◽  
Mark McDonald ◽  
Sankaran Mahadevan
Keyword(s):  
System Analysis ◽  
Epistemic Uncertainty ◽  
Probability Distributions ◽  
Uncertainty Propagation ◽  
Probabilistic Approach ◽  
Interval Data ◽  
Cumulative Distribution ◽  
System Response ◽  
Computationally Efficient ◽  
Probabilistic Uncertainty

This paper develops and illustrates a probabilistic approach for uncertainty representation and propagation in system analysis, when the information on the uncertain input variables and/or their distribution parameters may be available as either probability distributions or simply intervals (single or multiple). A unique aggregation technique is used to combine multiple interval data and to compute rigorous bounds on the system response cumulative distribution function. The uncertainty described by interval data is represented through a flexible family of probability distributions. Conversion of interval data to a probabilistic format enables the use of computationally efficient methods for probabilistic uncertainty propagation. Two methods are explored for the implementation of the proposed approach, based on (1) sampling and (2) optimization. The sampling-based strategy is more expensive and tends to underestimate the output bounds. The optimization-based methodology improves both aspects. The proposed methods are used to develop new solutions to challenge problems posed by the Sandia epistemic uncertainty workshop (Oberkampf et al., 2004, “Challenge Problems: Uncertainty in System Response Given Uncertain Parameters,” Reliab. Eng. Syst. Saf., 85, pp. 11–19). Results for the challenge problems are compared with earlier solutions.

Subspace-based estimation of time of arrival and Doppler shift for a signal of known waveform

2009 ◽  
Vol 1 (3) ◽  
pp. 209-214
Author(s):  
V.V. Latyshev
Keyword(s):  
Doppler Shift ◽  
Signal To Noise Ratio ◽  
Time Of Arrival ◽  
Computationally Efficient ◽  
Signal To Noise ◽  
Sufficient Statistics ◽  
Ml Estimation ◽  
Generalized Eigenvectors ◽  
Low Dimensional ◽  
Estimation Of Time

The subspace-based technique is used for the estimation of the time of arrival and Doppler shift of a signal of known waveform. The tool to find required subspaces is a special orthogonal decomposition of received data. It allows one to concentrate Fisher information on the desired parameter in just a few of the first terms of the decomposition. This approach offers a low-dimensional vector of sufficient statistics. It leads to computationally efficient Bayesian estimation. Besides, it results in expansion of the signal-to-noise ratio (SNR) range for effective maximum likelihood (ML) estimation. Finally, we can obtain independent time arrival and Doppler shift estimations based on generalized eigenvectors.

scholarly journals Sparse Sonomyography-based Estimation of Isometric Force: A Comparison of Methods and Features

2021 ◽  
Author(s):  
Anne Tryphosa Kamatham ◽  
Meena Alzamani ◽  
Allison Dockum ◽  
Siddhartha Sikdar ◽  
Biswarup Mukherjee
Keyword(s):  
Isometric Force ◽  
Signal To Noise Ratio ◽  
Gaussian Process Regression ◽  
Feature Space ◽  
Speckle Noise ◽  
Neural Activation ◽  
Computationally Efficient ◽  
Noninvasive Methods ◽  
Efficient Operation ◽  
Force Prediction

Noninvasive methods for estimation of joint and muscle forces have widespread clinical and research applications. Surface electromyography or sEMG provides a measure of the neural activation of muscles which can be used to estimate the force produced by the muscle. However, sEMG based measures of force suffer from poor signal-to-noise ratio and limited spatiotemporal specificity. In this paper, we propose an ultrasound imaging or sonomyography-based approach for estimating continuous isometric force from a sparse set of ultrasound scanlines. Our approach isolates anatomically relevant features from A-mode ultrasound signals, greatly reducing the dimensionality of the feature space and the computational complexity involved in traditional ultrasound-based methods. We evaluate the performance of four regression methodologies for force prediction using the reduced feature set. We also evaluate the feasibility of a practical wearable sonomyography-based system by simulating the effect of transducer placement and varying the number of transducers used in force prediction. Our results demonstrate that Gaussian process regression models outperform other regression methods in predicting continuous force levels from just four equispaced transducers and are tolerant to speckle noise. These findings will aid in the design of wearable sonomyography-based force prediction systems with robust, computationally efficient operation.

scholarly journals Coupled Hydro-Mechanical Analysis of Rainfall-Induced Instability of Non-Uniform Soil Slopes

2021 ◽  
Author(s):  
Manyu Wang ◽  
Yong Liu ◽  
Lu Yang ◽  
Jing Wu ◽  
Guilin Niu
Keyword(s):  
Hydraulic Conductivity ◽  
Flow Rate ◽  
Large Scale ◽  
Slope Failure ◽  
Water Pressure ◽  
Mechanical Analysis ◽  
Soil Slope ◽  
Arithmetic Average ◽  
Average Value ◽  
Soil Slopes

In recent years, more considerable attentions are paying on the hazards of large-scale landslides induced by heavy rainfall. However, the heterogeneity in hydraulic properties of soils may affect the seepage pattern of water infiltrated into soil slopes. Inspired by this fact, this paper aimed to evaluate the effect of the spatial variability in hydraulic conductivity on failure mechanism of an unsaturated soil slope subjected to rainfall infiltration, being implemented in the framework of a transient coupled hydro-mechanical analysis. The concept of random field was adopted to model the spatial randomness of saturated hydraulic conductivity ks following a uniform distribution. The finite element method was then incorporated to conduct Monte Carlo simulations. The resultant findings show that the mode of shallow slope failure is more likely to occur than the deep one due mainly to the highly variable distribution of ks near slope surface. Note that the decrease in the effective stress of soils resulting from the increase of pore water pressure is the most critical reason for the occurrence of slope failure. In addition, from the random element analyses results, it indicates that the value of Qari calculated by performing a deterministic analysis based on arithmetic average value kari gives a prediction of flow rate on average, but the calculated Qmax based on maximum value kmax provides a more conservative assessment on total flow rate across soil slope, which can offer useful suggestions for practitioners to take available measures to drain in advance.

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