Assessment of engineering properties of Bangkok clay

Abstract

Due to the effect of structure, Bangkok clay is stable in a metastable state. Its void ratio, e, is the summation of the void ratio sustained by the intrinsic fabric, eR, and the additional void ratio due to the structure, es. The intrinsic state line (eR versus log σ′v, where σ′v is the effective vertical stress) is developed in terms of the void ratio at the liquid limit, eL. At the post-yield state, es is inversely proportional to σ′v. The residual additional void ratio, esr, which cannot be eliminated by the increase in effective vertical stress, is constant at about 0.20 for soft Bangkok clay and 0.12 for medium stiff Bangkok clay. From these findings and the ideal condition of zero compression at the pre-yield state, the field yield stress and field compression curve can be assessed. The undrained shear strength is directly related to the field yield stress, since both reflect the structure. The soil structure does not significantly influence the permeability. The permeability of the clay in structured and destructured states is identical under the same void ratio and can be determined from the generalized state parameter, e/eL. These observations result in a simple and practical method for assessment of the engineering properties of natural Bangkok clay.Key words: Bangkok clay, destructured state, compression, intrinsic state line, permeability, structured state, vane shear strength.

Strength Development in Cement Admixed Bangkok Clay: Laboratory and Field Investigations

“…Since Bangkok clay is non-to low swelling, and the swelling potential increases with depth (Horpibulsuk et al, 2007), kaolin and Bangkok clays, with free swell ratios of 0.6 and 1.3, were used to represent non-and low swelling clays, respectively. The free swell ratio, FSR, is deˆned as the ratio of equilibrium sediment volume of 10-g oven-dried soil passing a 425 mm sieve in distilled water (Vd) to that in carbon tetra chloride or kerosene (Vk).…”

“…Underlying this soft clay, medium to stiŠ clay was found. The medium to stiŠ clay was deposited above theˆrst sand layer (1st sand) overlying hard clay (Horpibulsuk et al, 2007). The natural water content of the soft Bangkok clay is close to liquid limit (slightly higher than liquid limit) near the ground surface, and tends to decrease with depth.…”

“…It has large potential for settlement with low inherent shear strength. This clay is classiˆed as non-to low swelling (Horpibulsuk et al, 2007) as per free swelling test (Prakash and Sridharan, 2004). Its swelling potential increases with depth.…”

“…Other parameters, such as other clay minerals (kaolinite, and illite, etc), the non-clay fraction (À0.002 mm) and pore medium chemistry, can also play a great role, masking the role of montmorillonite. As such, it is possible that some clayey soils can be classiˆed as non-swelling or low swelling types, even if the primary clay mineral in clay fraction (º2 mm) is montmorillonite (Horpibulsuk et al, 2007).…”

Role of Fly Ash on Strength and Microstructure Development in Blended Cement Stabilized Silty Clay

“…The FSR is deˆned as the ratio of equilibrium sediment volume of 10 g of oven-dried soil passing a 425 mm sieve in distilled water (Vd) to that in kerosene (Vk). This method was employed since it is a simple methodology to obtain an approximate and fairly satisfactory prediction of the dominant clay mineralogy of soil (Horpibulsuk et al, 2007). Chemical composition and grain size distribution curve of the silty clay are shown in Table 1 and Fig.…”