This paper presents the results of a numerical investigation on applicability of light-weight air foamed soils (LWFS) for soft ground improvement, which are made by mixing dredged soils, cement, and air foam to reduce unit-weight and to increase compressive strength. The engineering properties of LWFS were comprehensively investigated based on the previous experimental tests. And three dimensional numerical models which reflect soft ground conditions were adopted to evaluate the applicability of LWFS compared to soft ground improvement methods such as SCP(Sand Compaction Piles) and DCM(Deep Cement Mixing Piles). A number of cases were analyzed using a stress-pore pressure coupled model. The results indicated that LWFS method enables to reduce settlement and lateral ground flow than SCP method and enable to reduce residual settlement than DCM method in the scope of this paper. Also it was revealed that such effects are affected by the properties of LWFS such as lightness, appropriate strength and stiffness and Poisson's ratio.

抄録全体を表示

In general, reclamation with dredged soils requires a lot of time and cost. Few methods have been proposed to save these two factors. Using coal ash which is a co-product of thermal power generation has brought a great attention to researchers and engineers. Field tests were conducted and the results were analyzed to figure out the applicability of an artificial soil mixture with coal ash as a reclamation material. The ground composed of dredged soils and coal ash has a similar particle distribution to sand, and more cohesive and internal frictional angle than that with dredged soil only. In addition, the coefficients of horizontal consolidation and permeability were improved as well, which means the consolidation of the mixed ground could be accelerated.

抄録全体を表示

In recent years, there was a great offer of patented additives (enzymes) to the road market as solution to soil stabilization. This study aims to present a methodology to solve the problems that affects the use of additives in laboratory, because his use in conventional tests do not shown efficient for these purposes. For this, it was used a portable traffic simulator, easy handling and common in pavement laboratories. The soils used for the production of the tested tablets were lateritic soils from Rio de Janeiro–RJ, and the enzymatic products were imported. The study concludes, in principle, that the equipment used and the developed accessories are appropriate for this purpose and that the use of enzymes showed effective for some applications, but lacks more studies, including with the use of other types of soil to prove such effectiveness.

抄録全体を表示

In order to investigate the fundamental properties of pure tire chips and their mixture with sand, a series of monotonic shear and cyclic triaxial tests was performed. From the results of the monotonic drained shear tests on pure tire chips, linear development of axial and volumetric strains were observed during loading up to 20% axial strain in both types of tire chips. It was further observed that the volumetric strain induced by shear loading recovered to zero during unloading. It is considered that the volumetric strain induced by shear was not dilatancy by rearrangement of particles but due to the stretching of tire chips. In the monotonic undrained shear tests using the mixed sand and tire chips, the mixtures show completely different behavior to pure sand, this due to the particles of the tire chips being smaller than that of the sand. The matrix of the material was governed by tire chips when the tire chip fraction was greater than 0.3. From the results of the undrained cyclic triaxial tests of pure tire chips, there was hardly any development of pore water pressure, resulting in non-liquefaction.

抄録全体を表示

Due to formation of shrinkage cracks in landfill clay liners in dry zone of Sri Lanka leads to infiltration of leachate into ground during the rainy season. Therefore, in this research study, shrinkage behaviour of expansive soil available in dry zone of Sri Lanka, which is used to develop compacted clay liners, were evaluated using laboratory desiccation plate tests. Circular desiccation plates with different thicknesses were used for the experiments. A series of tests have been carried out with unamended soil and soil amended with different percentages of bentonite. Further, shrinkage behaviour was studied by amending oleic acid and coconut coir fibers into the soil. Digital image processing technique has been used to determine the Crack Intensity Factor (CIF). Crack initiation time under different configuration was recorded. Based on visual observations, it can be seen that all samples produce predominantly orthogonal crack patterns leading to sub division of crack area in to smaller cells. Higher desiccation rate was observed for smaller thickness of soil specimen. In addition, higher CIF was recorded for the bentonite amended soil. It was noted that shrinkage cracks can be controlled by amending soil with coconut coir fibers.

抄録全体を表示

This study develops a method of controlling backfill settlement of abutment by using a ground improvement technique employing a successive rows of soil-cement columns along the track. In order to confirm the effect of the proposed method, a shaking table test in the gravity field using a model of 1/15 scale was conducted. As a result of the shaking table test, the backfill, which was located between the abutment and the soil-cement columns, behaved together with the abutment. The failure plane was formed in backside of the soil-cement columns. It was confirmed by experiment that seismic earth pressure to the abutment was reduced by the proposed method since the soil-cement columns resisted the earth pressure from the backside by the subgrade reaction at the bottom of soil-cement columns during shaking. Thus, it was concluded that the proposed method shows a beneficial effect in preventing the settlement of backfill as it reduced seismic earth pressure to the abutment and kept the abutment backfill system safe.

抄録全体を表示