Reliability Based Design For Slope Stabilization Using Drilled Shafts And Anchors

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Reliability Based Design For Slope Stabilization Using Drilled Shafts And Anchors

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Author : Lin Li
language : en
Publisher:
Release Date : 2014

Reliability Based Design For Slope Stabilization Using Drilled Shafts And Anchors written by Lin Li and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with Civil engineering categories.

Landslides and slope failures occur frequently every year to have major impact on the operational safety of roadways and to add financial burden to the highway agencies for slope repairs and maintenance. In this dissertation, a reliability-based computational algorithm is developed for design of a row of equally spaced drilled shafts and/or anchors to stabilize an unstable slope while achieving the required target reliability index with minimum volume of drilled shafts. The Monte Carlo simulation (MCS) technique is used in the previously developed deterministic computational program, in which the limiting equilibrium method of slices is modified to incorporate the arching effects of the drilled shafts in a slope. Uncertainties of soil parameters in the slope are considered by statistical descriptors, including mean, c.o.v., and distribution function. Model errors of the semi-empirical predictive equation for the load transfer factor for characterizing the soil arching effects are considered by statistics of bias. A PC-based program has been developed based on the above methodology. In order to dealing with small probability events in the drilled shaft/slope system and reduce the large number of MCS calculations, a more advanced methodology, importance sampling technique (IST), is proposed to determine the probability of failure and the reliability index of a drilled shaft/slope system. The performance function and the design point are determined by the ordinary method of slices (OMS) with the accompanying load transfer factor. To permit system reliability analysis for an anchor/slope system considering the effects of stochastic corrosion, the Monte Carlo simulation technique is used in conjunction with the modified limiting equilibrium method of slices. Meanwhile, the time-dependent deterioration of bond capacity of corroding soil anchors is developed in this methodology due to the attack of chlorides. The importance of using a system reliability-based computational method is illustrated by showing that the anchor/slope system may fail unpredictably during design life--even though the initial design results have a high degree of safety--if uncertainties of soil parameters, anchor force, and the time-dependent stochastic corrosion process are not accounted for systematically. In order to preventing a large earth thrust applied to the drilled shafts due to the dimensions of the failed slope, the use of multiple rows of drilled shafts could be a feasible solution to both ensure that the global factor of safety of the stabilized slope meets the target factor of safety and the amount of reinforcement used in the drilled shafts is constructible and economical. A limiting equilibrium based methodology, incorporating the method of slices and arching effects of the drilled shafts, is developed for optimizing the use of multiple rows of drilled shafts. It is shown that as compared to one row of drilled shafts, multiple rows of drilled shafts can effectively increase the global factor of safety and at the same time reduce the net force imparted on the shaft, thus making the reinforcement design more constructible and meeting the service limit.

Development Of Design And Analysis Method For Slope Stabilization Using Drilled Shafts

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Author : Wassel Al Bodour
language : en
Publisher:
Release Date : 2010

Development Of Design And Analysis Method For Slope Stabilization Using Drilled Shafts written by Wassel Al Bodour and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with Civil engineering categories.

"A practical methodology for stability analysis and design of drilled shafts reinforced slopes was developed utilizing limiting equilibrium method of slices. Complex soil stratifications and general failure slip surfaces can be handled in the developed method. The effect of soil arching due to the presence of the drilled shafts was accounted for by using a load transfer factor. The numerical values of the load transfer factor were developed based on 3-D FEM parametric study results. Many of the design variables controlling the slope/shaft systems, such: drilled shafts size, shafts locations, and the required spacing between the drilled shafts can be successfully determined from the developed method. The optimum location can be searched for and determined from the developed methodology. The global factor of safety for slope/shaft systems and the forces acting on the stabilizing drilled shafts due to the moving ground can be successfully estimated. For the purpose of verifying the validity of the proposed design methodology, the results of a field load testing program on the fully instrumented drilled shafts installed on an existing failed slope together with the companion 3-D FEM simulations are presented. This real case was analyzed using the proposed analysis and design methodology, the analysis results were compared with the FEM results, and it is found that they are in good agreement. In addition, Real-time instrumentation and monitoring were carried out for three landslide sites in the Southern part of Ohio. Various types of instruments were extensively installed inside the stabilizing shafts and the surrounding soils to monitor and better understand the behavior of slope/shaft systems. The field instrumentation and monitoring processes have provided excellent and unique information on the lateral responses of shafts undergoing slope movements. Also, the results of the instrumented cases have provided that the structural design (moments, shear, lateral deflection, and shaft tip fixity) of the shafts are overestimated (i.e., estimated forces acting on the shafts are high), and the geotechnical design (FS of slope/shaft system: movement and rate of movement) is achieved."--Abstract.

Landslide Stabilization Using Drilled Shafts In Static And Dynamic Conditions

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Author : Arash Erfani Joorabchi
language : en
Publisher:
Release Date : 2011

Landslide Stabilization Using Drilled Shafts In Static And Dynamic Conditions written by Arash Erfani Joorabchi and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with Boring categories.

One of the most common ways to stabilize the slope is to use the row of drilled shaft. The goal of this investigation is to introduce applicable methodology to calculate the factors of safety and force, on the shaft, in the static condition. By using the limit equilibrium approach accompanied with the concept of arching, due to incorporating the drilled shaft, the safety and force can be calculated. The 3-dimensional finite element parametric study is used to derive the regression based semi-empirical equations for quantifying the arching effect, through the load transfer factor. A computer program is written to incorporate the algorithms mentioned above for applications to real cases. The results of the proposed methodology are validated by the three dimension finite element analysis. Furthermore, seismic displacement of the slope, reinforced with a row of the drilled shafts, is calculated using modified displacement based method. This procedure is the extension work of seismic slope stability analysis presented by Bray and Rathje (1998) and Screen analysis presented by Stewart and Blake (2003). In this procedure, dynamic resistance of the drilled shaft/slope system is calculated in framework of limit equilibrium analysis accompanied with the arching due to incorporating the drilled shaft. To quantify the arching, the critical displacement is selected. First, the variation of arching as a function of displacement is studied. Then for critical displacement that causes the maximum force on the shaft and maximum displacement, the arching is quantified and applied to the limit equilibrium analysis. To address the geotechnical and structural issues, the performance based design is proposed to calculate the factor of safety of the drilled shaft slope system and the force on the drilled shafts based on an acceptable displacement. The results of seismic displacement, the factor of safety of slope shaft system, and the maximum induced force on the drilled shaft are validated by 3-dimensional Finite element analysis.

Drilled Shafts

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Author : Michael W. O'Neill
language : en
Publisher:
Release Date : 1999

Drilled Shafts written by Michael W. O'Neill and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1999 with Foundations categories.

Field Instrumentation Monitoring Of Drilled Shafts For Landslide Stabilization And Development Of Pertinent Design Method

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Author : Robert Y. Liang
language : en
Publisher:
Release Date : 2010

Field Instrumentation Monitoring Of Drilled Shafts For Landslide Stabilization And Development Of Pertinent Design Method written by Robert Y. Liang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with Landslides categories.

The design method for using a single row, spaced drilled shafts, socketed into a firm rock strata, to stabilize an unstable slope has been developed in this research. The soil arching due to the presence of spaced drilled shafts in a slope was observed in 3-dimensional finite element simulations and field monitoring data. A comprehensive 3-D finite element parametric study was used to derive an empirical equation to quantify the arching induced load transfer. A limiting equilibrium based slope stability analysis method, incorporating the arching effect, was developed and coded into a PC based program UA SLOPE 2.1, to allow for analysis of the factor of safety of the shaft/slope system and the earth thrust on the drilled shaft. The developed analysis and design method was validated based on more than 40 cases of 3-dimensional finite element simulations, covering a wide range of slope geometry, soil strength parameters, and the drilled shaft diameter, spacing, and location conditions. Three slope stabilization projects in Ohio involving the use of drilled shafts were monitored with instrumentations to obtain a 3-year performance data of the stabilized slope and to validate the design based on the developed method. In addition, a field testing program at the ATH-124 Project site was conducted to quantify arching during several stages of surcharge load induced slope movements. The developed UA SLOPE 2.1 program was verified by comparisons with the calibrated finite element simulation results of this field surcharge loading condition. The UA SLOPE 2.1 program is recommended for use in finding an optimized design (i.e., location, diameter, and spacing) of the drilled shafts to stabilize an unstable slope.

Landslide Stabilization Using A Single Row Of Rock Socketed Drilled Shafts And Analysis Of Laterally Loaded Drilled Shafts Using Shaft Deflection Data

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Author : Mohammad M. Yamin
language : en
Publisher:
Release Date : 2007

Landslide Stabilization Using A Single Row Of Rock Socketed Drilled Shafts And Analysis Of Laterally Loaded Drilled Shafts Using Shaft Deflection Data written by Mohammad M. Yamin and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with Landslides categories.

"An accurate and practical methodology for stability analysis and design of drilled shafts reinforced slopes was developed utilizing limiting equilibrium method of slices. Complex soil stratifications and general failure slip surfases can be handled in the developed method. The effect of soil arching due to the presence of the drilled shafts was accounted for by using a load transfer factor. The numerical values of the load transfer factor were developed based on 3-D FEM parametric study results. Many of the design variables controlling the slope/shaft systems, such: drilled shafts size, shafts location, shaft fixity (the necessary rock-socket length), and the required spacing between the drilled shafts to prevent soil from flowing around the shafts can be successfully determined from the developed method. The optimum location where the drilled shafts could be placed within the sliding soil mass so that the cost associated with the landslide repair using the drilled shafts is minimized can be searched for and determined from the developed methodology. From geotechnical point of view, the global factor of safety for slope/shaft systems can be determined. From structural point of view, the forces acting on the stabilizing drilled shafts due to the moving ground can be successfully estimated. In addition to the developed design methodology, Real-time instrumentation and monitoring were carried out for three landslide sites in the Southern part of Ohio. Various types of instruments were extensively installed inside the stabilizing shafts and the surrounding soils to monitor and better understand the behavior of slope/shaft systems. The UA Slope program developed by Dr. Robert Liang in cooperation with ODOT and FHWA has been used in designing these landslides. The field instrumentation and monitoring processes have provided excellent and unique information on the lateral responses of shafts undergoing slope movements. Also, the results of the instrumented cases have provided that the structural design (moments, shear, lateral deflection, and shaft tip fixity) of the shafts are overestimated (i.e., estimated forces acting on the shafts are high), and the geotechnical design (FS of slope/shaft system: movement and rate of movement) is achieved in two case studies but not fully achieved for the third case. On the other hand, in an effort to develop an efficient analytical method for analysis of laterally loaded drilled shafts using only lateral shaft deflection data, numerical procedures were proposed based on the principle of superposition. The lateral shaft deflections along the shaft length due to superposition of the lateral applied load to the drilled shaft were added together to establish the compatibility equations that govern the lateral behavior of the drilled shaft system. The compatibility equations allow for the determination of the net applied loads to the drilled shaft responsible for specific amount of shaft deflections. Once the loads were determined, basic equilibrium equations were applied to calculate shear forces and bending moments along the shaft length. A computer program was developed implementing the proposed numerical procedures to facilitate numerical computations. Many laterally loaded drilled shaft examples were described and used to verify the validity of the developed method. Included in the cases for validation were two actual full-scale drilled shafts at Jefferson County: (1) landslide repair using drilled shafts; and (2) lateral load test, were demonstrated."--Abstract.

Performance Based Design Of Laterally Loaded Drilled Shafts

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Author : Robert Y. Liang
language : en
Publisher:
Release Date : 2013

Performance Based Design Of Laterally Loaded Drilled Shafts written by Robert Y. Liang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with Shafts (Excavations) categories.

Reliability-based design of deep foundations such as drilled shafts has been increasingly important due to the heightened awareness of the importance of risk management. The load and resistance factor design has been implemented by FHWA since 2007. Nevertheless, there are still many unsolved issues regarding the implementation of load and resistance factor design. In an attempt to address these issues, a performance-based design approach has been developed in which Monte Carlo simulation is employed to conduct reliability analysis. A series of computer codes were developed and validated. It was found that the spatial variability of soils is an important consideration in reliability analysis.

Probabilistic Analysis Algorithm For Ua Slope Software Program

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Author : Robert Y. Liang
language : en
Publisher:
Release Date : 2013

Probabilistic Analysis Algorithm For Ua Slope Software Program written by Robert Y. Liang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with Shafts (Excavations) categories.

A reliability-based computational algorithm for using a single row and equally spaced drilled shafts to stabilize an unstable slope has been developed in this research. The Monte-Carlo simulation (MCS) technique was used in the previously developed deterministic computational program, in which the limiting equilibrium method of slices was modified to incorporate the arching effects of the drilled shafts in a slope. Uncertainties of soil parameters in the slope were considered by statistical descriptors, including mean, coefficient of variance (c.o.v.), and distribution function. Model errors of the semiempirical predictive equation for the load transfer factor for characterizing the soil arching effects were considered by statistics of bias. A PC-based research grade program, UA Slope 3.0, was coded to allow for analysis of probability of failure and reliability index of a shaft/slope system. The illustrative example demonstrated that a single value of factor of safety chosen in the deterministic approach may not yield the desired level of reliability as uncertainties of soil parameters and model errors cannot be accounted for systematically. As an extension of this research, importance sampling technique (IST) on drilled shaft/slope system has been proposed to demonstrate its high efficiency, in which the importance function and design point are determined for the ordinary method of slices (OMS) with the accompanying load transfer factor. In addition, the design method of using multiple rows of drilled shaft was developed to stabilize a large slope, in which the design and optimization criteria were proposed to reach the target safety and the constructability while meeting the service limit requirement.

Quantile Based Reliability Analysis And Design In Slope Stability

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Author : Sukhdeep Singh
language : en
Publisher:
Release Date : 2018

Quantile Based Reliability Analysis And Design In Slope Stability written by Sukhdeep Singh and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.

The study and analysis of slopes are essential for understanding their performance and, in particular, their stability, reliability, and deformations. Traditional slope stability analysis involves predicting the location of the critical slip surface for a given slope and computing a safety factor at that location, which belongs to the deterministic frame. It is found that multiple sources of uncertainties often exist in the evaluation of slope stability. When assessing the stability of slopes in the face of risks, it is desirable, and sometimes necessary, to adopt reliability-based approaches that consider these uncertainties explicitly. The thesis develops an efficient methodology of soil modeling using maximum entropy based quantile distribution constrained by probability weighted moments, conducts field vane shear soil testing in the Nipigon river area and establishes the soil strength models. The research proposes a new reliability-based method to study the stability of the Nipigon river slope and carries out a reliability-based design of slopes by combining quantile-based reliability and multi-objective optimization. In general, the probability distribution describes the randomness of soil parameters collected empirically or tested by the few numbers of collected soil samples. However, the substantial effect of sample size on the estimation of random properties of the soil strength requires an extensive data to explore uncertainties, which is uneconomical and sometimes impossible to obtain. This study aims to consolidate recent advancement in probabilistic characterization and develops an inverse cumulative distribution function (ICDF) or quantile distribution, for direct quantification of the actual variability of various soil samples. Based on the analysis, a framework is developed that streamlines the formulation of probability weighted moments (PWM), and maximum entropy (MaxEnt) based distribution function for various soil properties when estimated using different field or laboratory tests, leading to a reliable procedure for applications of the proposed framework to different site characterization problems. Examples are provided to illustrate the implementation and step-by-step procedures of the proposed framework. This research further extends the reliability approach for slope stability problems and utilizes the first-order reliability method (FORM) with quantiles for improving the efficiency of the FORM with relatively small samples. Reliability analysis is combined with deterministic slope stability analysis and implemented using an efficient algorithm. The analysis is validated through comparison with other reliability methods and used to explore the effect of variability of the soil properties on slope system. It is found that, when variability of soil properties is defined by assuming a conventional distribution, the variance of factor of safety is overestimated or underestimated. The approach not only provides sufficiently accurate reliability estimates of slope stability but also significantly improves the computational efficiency of soil slope design in comparison with conventional design methods.

Geotechnical Slope Analysis

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Author : Robin Chowdhury
language : en
Publisher: CRC Press
Release Date : 2009-11-18

Geotechnical Slope Analysis written by Robin Chowdhury and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009-11-18 with Medical categories.

Freshly updated and extended version of Slope Analysis (Chowdhury, Elsevier, 1978). This reference book gives a complete overview of the developments in slope engineering in the last 30 years. Its multi-disciplinary, critical approach and the chapters devoted to seismic effects and probabilistic approaches and reliability analyses, reflect the distinctive style of the original. Subjects discussed are: the understanding of slope performance, mechanisms of instability, requirements for modeling and analysis, and new techniques for observation and modeling. Special attention is paid to the relation with the increasing frequency and consequences of natural and man-made hazards. Strategies and methods for assessing landslide susceptibility, hazard and risk are also explored. Moreover, the relevance of geotechnical analysis of slopes in the context of climate change scenarios is discussed. All theory is supported by numerous examples. ''...A wonderful book on Slope Stability....recommended as a refernence book to those who are associated with the geotechnical engineering profession (undergraduates, post graduates and consulting engineers)...'' Prof. Devendra Narain Singh, Indian Inst. of Technology, Mumbai, India ''I have yet to see a book that excels the range and depth of Geotechnical Slope Analysis... I have failed to find a topic which is not covered and that makes the book almost a single window outlet for the whole range of readership from students to experts and from theoreticians to practicing engineers...'' Prof. R.K. Bhandari, New Delhi, India