This paper presents the role of superabsorbent polymer (SAP) on strength and microstructure development in cemented clays with notably high water content. A series of unconfined compressive strength (UCS), scanning electron microscope (SEM) and X-ray diffraction (XRD) tests were performed to identify strength behavior and microstructure. Results showed that SAP significantly influenced the mechanical behavior of cemented clays with notably high water content, characterized by an increase in the unconfined compressive strength and a decrease in the after-curing water content with SAP content. This revealed that the strength increase due to SAP was directly related to the water absorption by SAP. Meanwhile, XRD results showed that the hydration products were controlled by cement and lime content, regardless of SAP content. That meant there was no chemical reaction between SAP particles used in this study and cement or lime. The microstructure analysis by SEM revealed that SAP played an important role in the microstructure of cemented clays. With an increase in SAP content, the water absorbed by SAP increased significantly, leading to a decrease in the pore volume and a denser soil fabric. This behavior indicated that the primary role of SAP on strength increase was to absorb and fix water in cemented clays. Consequently, the clay–cement cluster distance decreased with an increase in solid mass (soil particles and swollen SAP particles) and a decrease in pore water. The corresponding tighter flocculated fabric due to SAP eventually led to the strength increase.

Dredging activities in China produce a great deal of clay suspensions which are generally pumped into yards as filling materials to form reclaimed lands. Understanding the settlement behavior of clay suspensions during settling process is essential in engineering practice for meeting the design requirement on the storage capacity of reclaimed yards. To this end, this study performed 25 types of sedimentation tests on the clay suspensions with different liquid limits, initial water contents, and initial heights using different sizes of sediment columns. The experimental results indicate that the settlement–time curves of clay suspensions can be classified into three stages. It is found that the first stage can be ignored, and the sedimentation can be attributed to the second stage termed as settling stage in practice. Hyperbolic model is proposed for describing the settlement–time relationship during the settling stage, and a quantitative method of determining the settlement at the end of the settling stage is suggested. The changing trends of the settlement and the time at the completion of sedimentation are investigated with considering the effects of liquid limit, initial water content, and initial height.

The virgin compression of reconstituted clays is essential for assessing soil structure developed during geological processes as a reference to compare with that of natural clays. It is well observed experimentally that compression behavior of reconstituted clays is greatly affected by initial water contents. However, the quantitative description of virgin compression seldom includes initial water content effects. In this study, a new quantitative description is proposed for describing initial water content effects on virgin compression of reconstituted clays. The proposed general compression model is then used to predict the compression behavior of 24 types of clays over 90 tests covering a wide range of stress levels. An overall good agreement between the predicted and measured compression curves suggests that the proposed model provides a useful means to estimate the virgin compression of clays reconstituted at various initial water contents. This work can then be taken as a useful reference with enabling the initial water content of reconstituted clays equal to the natural water content of natural clays for evaluating soil structure.

This paper proposes a practical method of determining embankment loads-induced vertical superimposed stress in subsoil by incorporating the effects of contact stress and soil elastoplastic behavior. The particulate–probabilistic theory is introduced to establish a new way of determining contact stress for overcoming the assumptions in the traditional trapezoidal stress distribution approach with instantaneous loading and perfectly flexible loaded area along the base. Then, the Flamant solution is introduced to propose a practical method of determining the vertical superimposed stress in subsoil. A reduction coefficient of 0.85 is suggested for considering the effect of elastoplastic of subsoil. The measured values of contact stress and field settlements are compiled from literature available to validate the proposed equations. It is found that the suggested methods in this study can improve significantly the degree of accuracy of the Osterberg method (Osterberg 1957) in calculating embankment loads induced settlement.