One-dimensional electrokinetic stabilization of dredged mud

Reuse of dredged marine sediments for land reclamation is a sustainable method for disposing the large quantities of dredged spoil, accumulating every year worldwide. However, due to their high water content and low permeability, dewatering and self-sedimentation of the material takes a long time to be completed. Therefore, different methods, such as prefabricated vertical drains and vacuum preloading, are used to improve the consolidation properties of the dredged mud at the port of Brisbane. Among these stabilization methods, vacuum preloading is determined as the most effective method to increase the consolidation of the dredged mud. However, clogging during vacuum consolidation is undesirable. Therefore, electrokinetic stabilization draws attention since it is an environmentally friendly and time efficient method to dewater and consolidate dredged mud significantly. The effectiveness of the electrokinetic stabilization depends on the properties of the soil and the electrode configurations. One-dimensional and two-dimensional electrode configurations are the most popular configurations. In this study, the effect of one-dimensional electrode configuration, which is installation of electrodes in arrays of anodes and cathodes on consolidation parameters of dredged mud, is investigated. Based on this study, the dredged mud sediments can be stabilized using one-dimensional electrokinetic stabilization which resulted in improving compression index and coefficient of volume compressibility and reduction of soil plasticity index

Laboratory testing of soils, rocks and aggregates

Testing rocks and aggregates are rarely covered in soil testing books and there are no separate books on rock or aggregate testing. Laboratory Testing of Soils, Rocks and Aggregates includes laboratory testing methods for most tests for soils as well as rocks and aggregates, which are becoming increasingly common in professional practice and university teaching. Part A gives a general overview of laboratory measurements, equipment, units, safety and standards. Part B covers soil tests from grain size distribution to consolidation, triaxial and direct shear tests. Part C covers rock tests, which includes the indirect tensile strength test and point load test. Part D covers the common tests carried out routinely on aggregates, which includes the aggregate impact value test and Los Angeles abrasion test. Each test consists of the following descriptive parts: Objective, Standards, Introduction, Procedure, and Cost. References are made to ASTM International (ASTM), Australian (AS), British (BS) and International Society of Rock Mechanics (ISRM) standards and any differences are noted

Soil Mechanics and Foundation Engineering

Learn the basics of soil mechanics and foundation engineering. This hands-on guide shows, step by step, how soil mechanics principles can be applied to solve geotechnical and foundation engineering problems. Presented in a straightforward, engaging style by an experienced PE, Soil Mechanics and Foundation Engineering: Fundamentals and Applications starts with the basics, assuming no prior knowledge, and gradually proceeds to more advanced topics. You will get rich illustrations, worked-out examples, and real-world case studies that help you absorb the critical points in a short time

Simplified method of fragments based two dimensional seepage solution for the double-wall cofferdam

Most seepage problems discussed in the literature are simplified as two-dimensional problems. They are solved using flow nets or numerical methods, where it is possible to compute the flow rate, exit hydraulic gradient and pore water pressures within the flow region. Method of fragment is an approximate technique which enables quick estimates of the flow rate, exit hydraulic gradient and pore water pressures based on some simple solutions. The flow is computed in terms dimensionless form factors that reflect the geometry of the flow domain. Design charts have been proposed in the literature for estimating the form factors and the exit hydraulic gradient in the case of a double-walled cofferdam. In this paper, an attempt is made to further simplify the application of the method of fragments to the double wall cofferdam by developing expressions for the necessary form factors and the exit hydraulic gradient in terms of geometry

Settlements of shallow foundations on granular soils - an overview

The main objective of this paper is to review the current state-of-the-art for predicting settlements of shallow foundations in granular soils. The traditional settlement prediction methods are critically reviewed. The Settlement '94 prediction session held in Texas clearly showed the deficiencies in the present settlement prediction methods, which generally overestimate the settlements and underestimate the allowable pressures, making the foundation designs very conservative. Some recent developments, including two deterministic methods and a probabilistic approach, are discussed as they have significant potential to improve the current state-of-the-art. Several empirical correlations relating the modulus of elasticity of soil and penetration resistances and standard penetration and cone penetration tests are summarized

Settlements of shallow foundations on granular soils - an overview

The main objective of this paper is to review the current state-of-the-art for predicting settlements of shallow foundations in granular soils. The traditional settlement prediction methods are critically reviewed. The Settlement '94 prediction session held in Texas clearly showed the deficiencies in the present settlement prediction methods, which generally overestimate the settlements and underestimate the allowable pressures, making the foundation designs very conservative. Some recent developments, including two deterministic methods and a probabilistic approach, are discussed as they have significant potential to improve the current state-of-the-art. Several empirical correlations relating the modulus of elasticity of soil and penetration resistances and standard penetration and cone penetration tests are summarized

An in-depth comparison of cv values determined using common curve-fitting techniques

The coefficient of consolidation (cv) is traditionally determined by fitting observed settlement–time data to the theoretical average degree of consolidation versus time factor relationship developed by Terzaghi. Although it is widely accepted that different curve-fitting methods can produce different values of cv, very few comparisons have been conducted to assess the validity of these methods. In this study, the settlement–time data gathered from conventional oedometer tests conducted on three different clays were analysed using three common curve-fitting techniques: the Casagrande log-time method, Taylor's root-time method, and the Cour inflection point method. A new method proposed by the authors for calculating cv, which abandons the traditional curve-fitting approach in favour of a computational-based approach, was also used to compare these results. To assess the validity of each cv value, the experimental results were compared with the theoretical average degree of consolidation curve and quantified using the root-mean-square (rms) error. The efficacy of the designated curve-fitting method was found to significantly depend upon the "shape" of the settlement–time curve generated during testing. For example, in this study, clay containing a significant fraction of fine sand often resulted in settlement–time curves that exhibited no clear inflection point, which made analysis using the Cour method very difficult. In general, the Taylor method predicted larger values of cv than the Casagrande method, and correspondingly smaller rms errors. The variance method proposed by the authors resulted in values of cv that more closely matched those generated using the Casagrande method. However, smaller rms errors were achieved using the variance method, which suggests that this technique may produce a more realistic estimate of cv than the Casagrande method

Simplified method of fragments based two dimensional seepage solution for the double-wall cofferdam

Most seepage problems discussed in the literature are simplified as two-dimensional problems. They are solved using flow nets or numerical methods, where it is possible to compute the flow rate, exit hydraulic gradient and pore water pressures within the flow region. Method of fragment is an approximate technique which enables quick estimates of the flow rate, exit hydraulic gradient and pore water pressures based on some simple solutions. The flow is computed in terms dimensionless form factors that reflect the geometry of the flow domain. Design charts have been proposed in the literature for estimating the form factors and the exit hydraulic gradient in the case of a double-walled cofferdam. In this paper, an attempt is made to further simplify the application of the method of fragments to the double wall cofferdam by developing expressions for the necessary form factors and the exit hydraulic gradient in terms of geometry

Approximate equations for the method of fragment

The method of fragment is a simple and approximate technique for solving confined seepage flow problems. In this method, the flow domain is divided into few fragments along the equipotential lines that are assumed to be vertical and a dimensionless form factor is defined for each fragment. The flow rate and the exit hydraulic gradient can be computed using the form factors. Griffiths proposed three types of fragments that are adequate to solve most configurations, incorporating anisotropy in permeability, and presented design charts for determining the form factors. In this paper, through extensive numerical modeling simulations, equations are developed for the form factors and they are validated. These equations enable quicker computations and the method of fragment be implemented in spreadsheets

Time-invariant and time-variant reliability analyses of reinforced concrete systems with appraisal data missingness

This paper deals with reliability analyses of in-service reinforced concrete (RC) systems with the missingness of some structural appraisal data. After succinctly illustrating the appraisal data missingness, both the time-invariant and time-variant reliability analyses are performed based on the expectation-maximization (EM) algorithm with access to only incomplete structural appraisal data. Specifically, the time-invariant analyses allow for the combination of dead and live load effects, as well as their magnitudes; while in the time-variant analyses, hazardous loading with different values of the occurrence rate and the degradation of the resistance of an RC system with time are considered. The performance function of an RC system is configured such that it may appositely take into account the existent safety redundancy in the system. With a nonparametric statistical inference technique, simulated and field-collected structural appraisal data are then used to demonstrate the effectiveness of the formulated framework for the reliability analyses