Strengthening Of Soft Soil Using Caboxymethyl Cellelouse Biopolymer

The application of appropriate chemicals is a widely used strategy for soil stabilization. The drive of this study is to determine the possibility of using the biopolymer carboxymethyl cellulose as an environmentally acceptable soil stabilizer. In this work, Atterberge limits tests, specific gravity, compaction, and consolidation tests were used to determine the engineering parameters of soils treated with varying amounts of biopolymer. Additionally, changes in the morphological properties of the soft soils were evaluated using scanning electron microscopy (SEM). It was estimated that as the soil’s biopolymer content increases, the specific gravity drops down, though the optimum water content (OMC) is extended. The outcomes showed diverse effects on Atterberg’s limits by cumulative the liquid limit(LL) and plasticity index (PI) though decreasing the plastic limit as the bio-polymer content increases. By the addition in polymer gratified, the combination boundaries (Solidity index Cc and recompression index Cr) decline.

Effect of Nano-Silica on Consolidation and Permeability Properties of Lateritic Soil

A reddish-brown lateritic soil obtained from Zaria; Nigeria was treated with up to 2.5% nano-silica. Consolidation properties (i.e. Pre-consolidation pressure, compression index, coefficient of volume compressibility and coefficient of consolidation) of treated specimens were assessed using one dimensional consolidation test. The permeability property of treated soil was also evaluated. The results obtained showed that the pre-consolidation pressure generally increased with increasing percentage of nano-silica content and curing time. The compression index (Cc) increased steadily with higher percentage of nano-silica contents up to 2.5% treatment for 7 and 14 days of curing, but decreased after 28 days curing period. The recompression index (Cr) on the other hand generally increased with increase percentage of nano-silica content and curing period. The coefficient of volume compressibility (Mv) did not follow any definite trend, but at 2.5% nano-silica content, the Mv decreased for all curing periods considered. The coefficient of consolidation (Cv) also, did not give a definite trend with increase in nano-silica content, suggesting that increasing the amount of nano-silica content in the soil has little or no impact on the time rate of settlement. The coefficient of permeability (k) decreased as the soil was treated with nano-silica especially beyond loading pressure of 40kN/m2. This study showed that nano-silica (up to 2.5%) can be used to stabilize lateritic soil to improve its consolidation properties.

Effect of Curing Pressure on Compression and Consolidation Behaviors of Cement Admixed Clay

The cemented soils are typically produced and cured under confining pressure of soil. The cemented soil properties are, however, obtained from laboratory tests on the cement admixed clay samples cured under atmospheric pressure. Thus, the parameters of cemented soil obtained from laboratory tests are not representative of the actual values in the field. In this research, a series of consolidation tests using oedometer apparatus on cement admixed clay samples with different curing pressure conditions was carried out. The samples was cured under pressure values of 0 kPa (atmospheric pressure) and 50 kPa. The test samples with values of cement content of 0, 1 and 2 percent were cured for 28 days before testing. The compression curves of cement admixed kaolin showed the elasto-plastic deformation in all cases of the tests. It was found that the range of void ratio of the samples with curing pressure of 0 kPa (atmospheric pressure) was higher than that of the samples with curing pressure of 50 kPa. With increasing curing pressure and cement content, the value of recompression index decreased while the value of compression index was approximately constant. It was also observed that the preconsolidation pressure increased with increasing cement content for both cases of curing pressure. It should be noted that the values of preconsolidation pressure increased with increasing curing pressure. Moreover, the values of coefficient of consolidation decreased with increasing effective vertical stress in all cases. It was also found that the values of coefficient of consolidation increased with increasing curing pressure and cement content.

Drilled pile behaviour in granular deposits

The results of full-scale pile load tests, field monitoring, and laboratory tests on undisturbed soil samples have been used to compare soil parameters determined from in situ tests and in the laboratory for pile design in granular deposits. These results indicate a close agreement between the field- and laboratory-determined rebound or recompression index of oil sand. Also, a good agreement is indicated between field-measured and calculated pile head settlements. However, the measured average skin friction along the pile shaft in sandy till is about 20% more than the calculated values obtained from empirical and finite element analytical work using laboratory- and field-determined soil parameters. Theoretical t–z curves provided a good approximation of the field behaviour for the pile shaft resistance. Key words: drilled piles, belled piles, oil sand, skin friction, rebound, settlement, load test.