Springer Science and Business Media LLC

Bottom ash is a by-product generated during the coal combustion of thermal power plant. Bottom ash-based geopolymer has been reported as a promising substitute of cement in concrete. In this study, bottom ash collected from Honam Coal Power Plant was ground to be used as a soil stabilizer. Sodium hydroxide solution (NaOH) with different molarity concentration and sodium silicate solution (Na2SiO3) were added to enhance the polymerization reaction of ground bottom ash. The effects of water/ground bottom ash, Na2SiO3/NaOH ratio and concentration of NaOH solution on the unconfined compressive strength of sand mixture at the ambient curing conditions were investigated. The results indicated that ground bottom ash can be utilized to stabilize sand as a main binder at the ambient curing conditions. In particular, with the 4 M concentration of sodium hydroxide solution, the Na2SiO3/NaOH ratio of 1.5 and the water/binder ratio of 0.35, the highest compressive strength obtained at 28 days was around 9 MPa. The compressive strength of sand mixture increased with an increase of NaOH solution concentration and the ratio of Na2SiO3/NaOH, however, it dramatically decreased with the addition of water to the mixture.

The common availability of recycled textile from clothing represents an untapped resource which can be used as soil reinforcement. Recent efforts to use fibers as soil reinforcement have mostly concentrated on adding thin long fibers to natural soils. The techniques when applied to production often encounter mass production issues such as the difficulty in preventing localization, entanglement of the fibers and adhesion between the fiber and soil matrix interface. This experimental study uses small amounts (0.5%, 0.75% and 1.0%) of repurposed textile from polyester clothing cut into small pieces to reinforce a poorly graded sand. The California Bearing Ratio (CBR) test was used to quantitatively assess the strength characteristics of sand reinforced by adding whole textiles. The results of the laboratory program indicate a significant increase in CBR numbers and offers insight into the possible increase in other strength parameters such as ultimate bearing capacity. The increase in CBR values changes the suitability of the reinforced sand from subbase soils only, to also include base soils within pavements. During laboratory procedures localization and entanglement of textile reinforcement during mixing was not observed which suggests minimal difficulties when implementing the technology during construction applications. The results indicate that the use of the technique can lead to cost savings associated with the use of low-cost aggregates within a pavement base and subbase, thinner base and subbase layers, smaller footprints related to steeper slopes, and decreased periodic maintenance requirements of pavements.

The soil parameters identification procedure is usually a trade-off between sophisticated soil model behaviour and the large number of parameters to identify. Such procedure that can accomplish both of these objectives is highly desirable, but also difficult. This paper presents a methodology for identifying soil parameters that takes into account different constitutive equations. For identifying the generalized Prager model parameters, associated to the Drucker and Prager failure criterion, using an in-situ pressuremeter curve, we have proposed a procedure that is based on an approach of inverse analysis. This approach involves the minimizing the function representing the area between the experimental curve and the simulated curve, obtained by fit in the model along the in-situ loading path. A comparative study between two optimization processes is proposed. The first is based on the technique of the simplex by Nelder and Mead, while the second is based on the decomposition of the pressuremeter curve in three distinct areas. After a brief description of an existing computer program called Press-Sim, which has been written in Fortran for analyzing a cavity expansion using the finite element method, a short explanation is given about the two optimization procedures considered in this article. Then, for a chosen site where soil strength parameters are measured, the comparative study has been performed for both methods at four different depths. For the determination of the angle of friction, the two procedures yield very close values and are in a good agreement with that given by the triaxial test, while for the cohesion, they both diverge from each other on both sides of the value measured by the trial test.

The understanding of unsaturated soil mechanics principles is of interest to a wide spectrum of geotechnical problems associated with soils above water table and compacted soils. This paper describes the stress state variables and constitutive equations based on the unsaturated soil mechanics principles. In addition, the basic concepts for characterization of unsaturated soils and measurements of matric suction (or negative pore-water pressures) are also explained. The application of unsaturated soil mechanics theories is illustrated through the use of capillary barrier system for minimizing rain infiltration into residual soil slopes.

Construction of earth structures involves the use of compacted soils. In roads construction quality controls like the bearing capacity of the subgrade, base and subbase layers, CBR values and compaction characteristics are primarily important. In Sweden, it has become interesting to correlate new testing parameters collected by simple tests to the conventional compaction parameters collected from modified Proctor tests. This action will help in assessing the bearing capacity of the selected material simply and quickly using the recent developed techniques instead of the conventional techniques which have been considered as time consuming methods. The aim of this study is to demonstrate that the laboratory dynamic California bearing ratio (CBRLD) test can be used as a method of compaction assessment of selected subgrade soil. Moreover, it has been demonstrated in this study that the CBRLD can strongly be correlated to the compaction densities and molding water contents using polynomial correlation and a best-fit multiple regression model for a wide range of molding water contents. In addition, the repeatability of the dynamic laboratory CBR test was examined as discussed in the current article.

Deep excavation is a common part of development to utilize underground space in densely populated areas. Protection of contiguous building and properties is a primary design concern space. Soil nailing is one such technique to exchange conventional retaining system for deep excavation. It will also donate to significant saving in cost and time of construction compared to conventional retaining systems. In this study an attempt has been made to have a deep vertical excavation on ground of 10 m height using soil nail wall. Also studied the enactment of soil nail wall under different nail inclination to horizontal i.e., Ѳ = 0° and Ѳ = 15° with water table. The finite element analysis of soil nail wall was carried to study the behavior of maximum horizontal wall displacement, maximum horizontal nail displacement, base heave, maximum axial force in nail, maximum shear force in nail, maximum bending moment in nail under both static and seismic conditions using PLAXIS 2D. The process of construction is carried out in stages and a value of Global factor of safety (FSG) is maintained above 1.5 to make sure its stability. The length of nail has a major impact on the behavior of soil nail wall system; increase in nail length will increase the FSG. Results of the numerical analysis direct that the use of soil nail wall is desirable to impart stability to retaining systems.

The purpose of this study is to analyze the changes in the vertical load of the pile when the additional vibration load due to mechanical vibration acted to the single pile supporting a vibration machine, and to review the validity of the typical calculation method for the axial bearing capacity of a single pile supporting the vibration machine by numerical analysis. Firstly, the 3D numerical model for the load–displacement behavior of a single pile was constituted. After the model was statically loaded to the allowable load in static analysis, the axial vibration due to machine vibration was added to the pile top in dynamic analysis. In these procedures, the static analysis was verified with the centrifuge test results for a single pile. Based on the analysis results, it was found that the additional dynamic load caused by machine vibration is about 6% of the allowable static load. It was thought that the design concepts of the machine foundation, assuming that the additional dynamic load due to machine vibration equals to 50% of the static load in current code, is excessively conservative.

Ground penetrating radar (GPR) based land mine detection has a main challenge of having an accurate image analysis method that is capable of reducing false alarms. However this image analysis depends on having sufficient spatial resolution in the backscattered signal. This paper aims at getting better resolution by applying two migration algorithms. One is by Kirchhoff’s migration using geometrical approach and other one is F-K migration algorithms with Fourier transform. The algorithms are developed using MATLAB simulations over different scenarios for stepped frequency continuous wave (SFCW) GPR.