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The in-situ deep mixing technique has been established as an eŠective means to eŠect columnar inclusions into soft Bangkok clay to enhance bearing capacity and reduce settlement. In this paper, an attempt is made to identify the critical factors governing the strength development in cement admixed Bangkok clay in both the laboratory and theˆeld. It is found that clay-water/cement ratio, wc/C is the prime parameter controlling the laboratory strength development when the liquidity index varies between 1 and 2. Based on this parameter and Abrams' law, the strength prediction equation for various curing times and combinations of clay water content and cement content is proposed and veriˆed. This will help minimize the number of trials necessary to arrive at the quantity of cement to be admixed. Besides the wc/C, the strength of deep mixing column is controlled by the execution and curing conditions. For low strength improvement (laboratory 28-day strength less than 1,500 kPa), theˆeld strength of the deep mixing columns, quf, made up from both dry and wet mixing methods is higher than 0.6 times the laboratory strength, qul. The quf/qul ratios for the wet mixing columns are generally higher than those for the dry mixing columns. This higher strength ratio is due to the dissipation of the excess water in the column (consolidation) caused by theˆeld stress. The water to cement ratio, W/C, of 1.0 is recommended for the wet mixing method of the soft Bangkok clay. A fast installation rate was shown to provide high quality for low strength columns. Suggestions are made for improving the deep mixing of soft Bangkok clay, which are very useful both from economic and engineering viewpoints.

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Lightweight cemented clays have wide applications in the infrastructure rehabilitation and in the construction of new facilities. The strength and compression characteristics of lightweight cemented clays with non-to high swelling potential are investigated and presented in this article. The workable state, the optimum water content to produce the lightweight cemented clay, is about 1.9 times the liquid limit. The void/cement ratio, V/C, which is defined as the ratio of void volume of the clay to the cement volume, is proved to be the prime parameter governing the strength and compression characteristics of cemented clays. The fabric (arrangement of clay particles, clusters and pore spaces) reflected from both air foam content and water content is taken into consideration by the void volume while the inter-particle forces (levels of cementation bond) are governed by the input of cement (cement volume). A strength equation in terms of V/C at a particular curing time is introduced using Abram's law as a basis. From the critical analysis of test results, a mix design method to attain the target strength and unit weight is suggested. This method is useful from both engineering and economic viewpoints.

Cement stabilization is extensively used to improve engineering properties of soft 48 saline clay. The effect of salinity, which is altered with geological and climate changes, on the 49 strength development in cement admixed saline clay is investigated in this paper. For a 50 particular curing time and salt content, the strength development in cement admixed saline 51 clay is governed by the clay-water/cement ratio, w c /C. The strength increases with the 52 decrease in w c /C. The increase in salt content for a particular water content causes the increase 53 in generalized stress state, e/e L where e is the current void ratio and e L is the liquid limit void 54 ratio. The higher value of e/e L is associated with the lower effective stress and the inter-55 particle attraction. Hence, for the same clay-water/cement ratio, the strength of the cement 56 admixed clay with higher salt content is lower than that with lower salt content.