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Surcharging or preloading is one of the oldest and most widely used in situ ground improvement techniques to strengthen weak compressible clays and to remove undesirable settlements prior to erection of permanent infrastructure. Recently, the ground improvement technique has been adopted in combination with many other techniques. The current design methodology for surcharging based on the concept of average degree of consolidation is inadequate, as all the primary consolidation settlement to be induced by the permanent load is not eliminated by the surcharging process. The problem is quantitatively analysed using Terzaghi's one-dimensional consolidation theory. The proportion of residual primary consolidation settlement is quantified, and the starting time of the re-occurrence of primary consolidation on exertion of the permanent load is determined. The effect of a change in surcharging duration on the proportion of residual settlement is quantified. The results are presented in design charts to facilitate application of the results by practicing geotechnical engineers. [ABSTRACT FROM AUTHOR]

For steep slopes with difficult access or slopes in a corrosive environment, there are various problems associated with the use of conventional steel reinforcement bars as soil nails. For loose-fill slopes or clay slopes, the development of adequate nail bond strength is another practical issue that should be considered. Carbon fiber-reinforced polymer (CFRP) and glass fiber-reinforced polymer (GFRP) in several forms and installation methods have been studied as the alternatives to the classical steel bar. Extensive laboratory tests on the materials and field tests on different types of soil nails with various methods of installation have been carried out in Hong Kong, Korea, and Australia. Test results support the use of these materials with an innovative installation method as soil nails under different geological conditions, and the suitability and performance of these materials under different conditions are assessed in the present study. Key words: soil nail, glass fiber, stress transfer, pullout test, numerical modeling. Dans le cas des pentes raides ou des pentes situees dans un environnement corrosif, on est confronte a divers types de problemes associes a l'utilisation de barres de renfort conventionnelles en acier, telles que les clous d'ancrage dans le sol. Dans le cas de pentes constituees de remblai lache ou d'argile, la necessite de creer une adherence d'ancrage suffisante est un autre probleme pratique dont il faut tenir compte. Des polymeres renforces de fibres de carbone (PRFC) et des polymeres renforces de fibres de verre (PRFV) sous differentes formes ainsi que diverses methodes d'installation ont ete etudies comme solutions de remplacement aux barres de renfort classiques. On a realise des essais pousses en laboratoire sur les materiaux et effectue des essais sur le terrain sur differents types de clous d'ancrage dans le sol, enutilisant diverses methodes d'installation, a Hong Kong, en Coree etenAustralie. Les resultats de ces essais ont montre que ces materiaux, associes a une methode d'installation innovante, constituaient de tres bons dispositifs d'ancrage dans differentes conditions geologiques. En outre, l'adaptabilite et les performances de ces memes materiaux dans differentes conditions sont evaluees dans la presente etude. [Traduit par la Redaction] Mots-cles: clou d'ancrage, fibres de verre, transfert de contraintes, essai d'arrachement, modelisation numerique., Introduction Soil nailing was first used in Hong Kong in the 1980s to provide support for highly weathered zones (GEO 2008). Currently, high-yield steel bars are commonly used as soil [...]

The current method of steel bar soil nail construction is both labor intensive as well as expensive and many engineers are considering the use of new soil nail materials. In the present pilot test, an innovative soil nail is constructed by light weight high strength glass fiber-reinforced plastic (GFRP) pipe with the Tube a' Manchette grouting technique. It is found that this new soil nail system can be handled easily on sites with difficult access. Extensive laboratory as well as field tests were carried out on the GFRP pipe nails and the grouted soil mass and numerical modeling of a field test was performed. The installation of the GFRP pipe, laboratory, and field test results that were carried out in Hong Kong and Korea are discussed in this paper. DOI: 10.1061/(ASCE)0899-1561(2009)21:3(93) CE Database subject headings: Soil nailing; Fiber reinforced polymers; Hong Kong; Korea; Material properties.

A soil reinforcement system using the combination of glass-fiber-reinforced polymer (GFRP) pipe and pressure grouting has been developed by a Korean company. The system is being adopted as slope stabilization measures in Hong Kong. Individual GFRP pipes were designed and installed as soil nails with the exception that two-stage pressure grouting was applied instead of gravity grouting. A full-scale field evaluation on constructability and in situ performance of the system was performed in Hong Kong. The performance of the constructed nails was evaluated by pullout tests. The construction procedure, site adaptations of the Korean product made in Hong Kong, field test procedure, and performance of the constructed soil nails are reported in this paper. DOI: 10.1061/(ASCE)0887-3828(2007)21:1(26) CE Database subject headings: Glass fiber; Fiber reinforced polymers; Soil nailing; Soil stabilization; Pull-out resistance; Hong Kong; Field investigations.

Abstract: Experimental studies and numerical simulation of experiments were conducted on pressure-controlled cavity expansion in clay. The modified Cam-clay model was used to describe the clay behaviour. The experimental data [...]

Electrokinetic extraction has been demonstrated to be very effective in removing heavy metals from Georgia kaolinite. The relatively high removal efficiency depends on the extremely acidic soil environment generated by the electrokinetic process. However, the efficiency observed in Georgia kaolinite cannot be achieved in soils of high acid/base buffer capacity without enhancement. In this study, the effect of ethylenediaminetetraacetic acid (EDTA) to enhance electrokinetic extraction of cadmium from Milwhite kaolinite was examined. The influence of electro-osmotic flow direction on the migration of cadmium, EDTA, and their complexes were also investigated. It was observed that injection of EDTA from the cathode reservoir by a reverse electro-osmotic flow could mobilize the cadmium in the specimen effectively. A less significant mobilization of cadmium was observed when the electro-osmotic flow was directed toward the cathode. However, accumulation of cadmium near the anode was observed regardless of the electro-osmotic flow direction. DOI: 10.1061/(ASCE)0733-9372(2005)131:2(298) CE Database subject headings: Fine-grained soils; Electrokinetics; Laboratory investigation; Sorption; Cadmium; Soil treatment.

Electrophoresis of clay particles from dilute suspensions is an innovative technology to seal leaks in operating surface impoundments that does not require removal of impoundment contents, exposure of workers to contaminants, or prior knowledge of the leak locations. A suspension of clay particles is added to the impoundment liquid. A cathode (negative electrode) is placed inside and an anode (positive electrode) is placed outside the leaking impoundment. A direct current (DC) electric field is imposed externally across the geomembrane liner through the leaks. The clay particles migrate to the leaks under the influence of the imposed electric field to form a clay cake seal. The results of laboratory experiments to evaluate the use of a DC electric field to direct migration of clay particles into a leak and the hydraulic integrity of the resulting seal are presented in this paper. The effects of clay type, clay particle concentration in suspension, size of leak, and electric field strength on the migration of clay particles and process of cake formation are evaluated. The sealing effectiveness and internal structure of the resulting clay cakes are examined by hydraulic conductivity measurements and nuclear magnetic resonance imaging. Electrophoretic mobilities of bentonite particles in different chemical environments were also measured to evaluate the feasibility of the technology in practical situations.

Vertical drains and preloading are very effective and economical ground modification techniques for accelerating primary consolidation and compensating some secondary compression of soft compressible soils. If vertical sand drains are used, they can be installed at different diameters. The drain diameter required thus becomes a dependent variable in the design process and the drain spacing is determined a priori. The required parameters can be obtained after a few iterations. However, the number of iterations may increase significantly when prefabricated vertical drains or strip drains are used as the drain size is predetermined by manufacturers and available only in a very limited range. Design curves are developed for prefabricated vertical drains in this paper. The equivalent drain diameter is used as the independent variable and drain spacing becomes the dependent variable. Soil smear around the drain is considered but well resistance of the drain is neglected. The curves can be used to design a vertical drain system without unnecessary iterations and/or interpolations when the equivalent drain diameter, degree of consolidation required, time available, and pertinent geotechnical engineering properties of the soil to be consolidated are given.

Coating piles with bitumen down to their neutral points to debond them from embedding soil is a feasible method to minimize the adverse effects of negative skin friction. Bitumen is a petroleum product composed of numerous extremely complex organic compounds including polycyclic aromatic hydrocarbons (PAHs) that have been identified by the U.S. Environmental Protection Agency (EPA) as toxic and carcinogenic materials. To investigate the engineering behavior of bitumen-coated piles under extreme weather conditions, full-scale field tests were performed in New Orleans, Louisiana, and Edmonton, Alberta, Canada. Instrumented piles were installed at these sites from 1989 to 1990. This paper presents the results of geoenvironmental field investigations performed at these sites to determine the spatial distribution of target PAHs in the subsurface after the piles had been installed for 2-3 1/2 yr. The findings of the investigation indicate that subsurface contamination, if there is any, caused by the installation of bitumen-coated piles is well within acceptable limits.

Electrokinetic extraction has been demonstrated to be effective in removing lead from pure Georgia kaolinite characterized by a low acid/base buffer capacity and cation exchange capacity. The relatively high removal efficiency is dependent on the low soil pH generated by the electrokinetic process. However, when impurities such as iron oxides are present, electrokinetics alone may not be effective in the extraction of lead due to the higher acid/base buffer capacity and cation exchange capacity of the soil. In this study, the effects of ethylenediaminetetraacetate (EDTA) on enhancing electrokinetic extraction of lead from a natural kaolinite containing approximately 4.3% iron oxides as [Fe.sub.2][O.sub.3] were examined. Interactions between lead and soil at different pH values were evaluated by batch tests. Results of the study show that approximately 90% of the lead spiked uniformly into the soil can be migrated toward the anode and accumulated within about 15% of soil for easier removal.

An innovative method was demonstrated to seal leaks in geomembrane liners by attracting clay particles to the leaks using electrophoresis. Electrophoresis is the movement of electrically charged particles suspended in a liquid by the action of an electric field. A direct-current voltage impressed across the liner causes electrical current to flow through the leaks. The current produces a strong electric field at leaks. When a clay slurry is dispersed into the liquid in the impoundment, electrophoresis attracts the clay particles to the leaks, thereby sealing them. The method can seal leaks in liquid impoundments without removing the liquid or locating or accessing the leaks. The laboratory and full-scale test results were remarkable in that electrophoresis sealed the leaks completely when a layer of geofabric was under the liner, and electrophoresis reduced the leakage rate through holes as large as 10 mm in diameter by a factor of 1,600 in the field test with gravel under the liner, and by a factor of 1,667 in the laboratory basin with geonet under the liner.

The stresses and displacements in the vicinity of a Griffith crack in a semiinfinite two-dimensional elastic medium subjected to a variable internal pressure are analyzed by polynomial approximation and Fourier transform, and semianalytical solutions to the governing differential equations are formulated. The variable internal pressure is approximated by a polynomial and solutions are then obtained by Fourier transform. The expressions for the components of stress and displacement due to the opening of a crack under an uniform internal pressure are derived as a special case example to illustrate the use of the derived solutions. They are in agreement with solutions derived by other methods published in the literature. However, it is very difficult, if not impossible, to obtain exact analytical solutions when the distribution of the variable internal pressure becomes more complex. The derived semianalytical solutions establish the basis for a more efficient algorithm to obtain numerical solutions in such cases.

Yalcin B. Acar claims that it is too difficult to consider the changes in electroosmotic coefficient of permeability because of changes in the zeta potential in the analysis of the elimination of contaminants from soil by electric fields. Douglas I. Stewart contends that the relationship between zeta potential and pH for uncontaminated kaolinite is not suitable for modeling electroosmosis in copper contaminated kaolinite. Albert T. Yeung claims that Gerald R. Eykholt's proposed model still has limitations among other things.

The advection-dispersion equation is often used to describe subsurface contaminant solute transport in a homogeneous, isotropic, and saturated geologic porous medium. An analytical solution to the equation has been developed by Ogata assuming the domain of space is extended from zero to infinity. However, the length of the column of geologic porous medium used in laboratory experimental studies is always finite. Criteria for applicability of the solution in analyzing experimental data obtained from column experiments are established in this paper. The velocity of the 50% concentration point of the concentration profile is often erroneously taken as the retarded advective velocity of the contaminant solute to determine the retardation factor and distribution coefficient of the contaminant between the solid and liquid phases. The error is carefully investigated for different boundary conditions of the experiments and necessary corrections are recommended. Detailed procedures for different applications of the developed correction charts are also presented in this paper.

The accuracy and usefulness of back-analysis in designing a vertical drain system is debated, and compared and contrasted with design curves. Topics include whether the models impose too many parameters for them to be applicable and reliable.

A pilot-scale experimental study and a theoretical and numerical modeling study were conducted on the different simultaneous processes involved during the electrokinetic extraction of lead from fine-grained soils. The principle of conservation of mass was employed. However, the control volume chosen for the formulation is questionable. Furthermore, the surface conductance of clay particles was not considered in the formulation and the electrical conduction contributed by the background electrolytes in the pore fluid was also neglected.

Electrokinetic extraction is an emerging technology that can be used to remove contaminants from heterogeneous fine-grained soils in situ. Contaminants in the subsurface are removed by the application of a direct-current electric field across the contaminated soil. The primary contaminant transport and removal mechanisms are electroosmotic advection and ionic migration. However, there are many complex physicochemical reactions occurring simultaneously during the process that may enhance or retard the cleanup process. Nonetheless, the viability of the technology has been established by results obtained from many bench-scale and large-scale laboratory and pilot-scale field experiments performed on various soils. This paper will review the fundamental concepts of the technology and discuss some important practical aspects and design criteria of the technology for field implementations. An example on cost analysis of the technology is also presented to demonstrate the use of various equations presented in the paper and to illustrate the cost-effectiveness of the technology.