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Effect of density on consolidation and creep parameters of a clay soil was investigated using a soil classified according to Unified  Soil  Classification  System  (USCS)  as  Clay  of  High plasticity (CH) and composing majorly of secondary minerals, including montmorillonite. The air-dried soil was compacted at five different compaction energy levels (Reduced Standard Proctor compaction energy, Standard Proctor compaction energy, West African compaction energy, Reduced Modified Proctor  compaction  energy,  and  Modified  Proctor compaction energy). Specimens for consolidation tests were molded  at  the  five  different  compaction  energy  levels (densities). The consolidation parameters (initial void ratio, compression  index,  and  preconsolidation  pressure)  were observed to be empirically related to the compaction energy. The  creep  parameters  (i.e.  primary  compression  index, secondary compression index, and magnitude of creep) were observed to increase with increases in loading to 387kN/m2, after  which  the  values  decreased.  Curves  resulting  from these relationships were observed to increase with increases in compaction energy level and tent towards straight line at Modified Proctor compaction energy. Maximum magnitude of creep estimated for three years was observed to reduce from 455.5 mm at Reduced Standard Proctor compaction energy through 268 mm at West African compaction energy to 247.4 mm at Modified Proctor compaction energy levels.

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A clay soil, classified as Clay of High plasticity (CH) according to Unified Soil Classification System (USCS) was stabilized with cement, Rice Husk Ash (RHA) and promoter. The mineralogy of the clay soil and the morphology of the clay and clay specimens admixed with varied composition of cement, RHA and promoter were evaluated in order to determine effect of the RHA on promoter stabilization of cement based clay soil. The promoter used in this study consists of calcium chloride and sodium hydroxide in the ratio of 1:1. The clay was remolded at standard Proctor compaction energy and the specimens were mixed with 0, 1.0, 2.0 and 3.0% cement, admixed with 1.0, 2.0, 3.0% RHA each, and 0.3, 0.6, 1.0% promoter each. The molded specimens were cured for 1, 7, 14, 28, 60 and 90days before testing for Unconfined Compressive Strength (UCS) and consequently the modulus of elasticity. The UCS of specimens without cement increased from 20 kN/m2 for the natural clay soil to 95 kN/m2 on addition of 3% RHA and 1.0% promoter after 28 days of curing, representing 475% increase in the UCS. This increase was confirmed by morphology of the clay soil mixed with RHA and promoter only, which showed presence of calcium silicate hydrate. Addition of 3.0% cement with 3 and 1.0% RHA and promoter respectively, increased the UCS from 220 to 375kN/m2 after 28 days of curing, which was also confirmed by the morphology of the specimens. The highest elastic modulus of 48.3 MPa was observed at specimens containing 3% cement, 3% RHA and 1.0% promoter.

-This research paper presents the results of comprehensive investigations on stress distribution in soils under pile cap of tapered piles in compressible clay. Compressible clay from Urucha and Shabani, area of Minsk province, Belarus was investigated in this work. The former was used for laboratory investigation, while field tests were conducted on the latter respectively. The results show the influence of axial compressive load on the magnitude, pattern and orientation of stresses in soils under the pile cap of loaded modeled instrumental piles bored into compressive clay soil. Stresses in the soils at different depths under the pile cap with reference to pile center lines were measured and compared with those obtained using Boussinesq's theory. Measured stresses are slightly higher than those calculated using the theory. The investigations also showed that, for tapered piles bored in compressive clay, the stress increases towards the center line of pile-pile cap joint irrespective of tapering angle only up to 0.5m below the cap, (model), beyond this point, the magnitude and pattern of stress changes. The vertical normal stress under the pile cap increases from zero at the surface to 42% in depth lower than 3.5R, and 55% beyond this point. The maximum principal stress is directed along the radius vector R and reduces radially outward from the pile centerline. The normal and shear stress vectors are less in pile with higher center to center spacing. In addition, stress distribution under pile cap is also a function of pile spacing and tapering angle. Clearly striated stressed zones of deformation under loaded pile cap, having depth in multiples of pile diameter were observed.