A series of isotropically consolidated undrained triaxial tests were performed on cemented clay with super-absorbent polymer (SAP) at high water content to investigate the effect of SAP content on the undrained shear behavior of cemented clay. The test results reveal that the compressibility and undrained shear strength of cemented clay with SAP in a preyield state are independent of the confining pressure. When the confining pressure is higher than the yield stress, the compressibility of the cemented clay with SAP increases dramatically. Meanwhile, the undrained shear strength of the cemented clay with SAP depends on the confining stress in the postyield state. The yield stress measured from the isotropic compression test is consistent with the transitional stress from the bilinear relation between the peak deviator stress and the confining pressure. For certain lime content, the role of SAP is to increase the cementation bond. Hence, the peak deviator stress increases with the increasing SAP content, lime content, and curing time. However, the cementation is shown to have no effect on pore pressure generation within the degree of cementation considered in this study. The linear failure envelope of the cemented clay with SAP is observed for the range of applied stress level in this study and is bounded by the tension cut-off and the critical state line of untreated clay. The difference between the failure line of cemented clay and the critical state line of untreated clay increase with the degree of the cementation bond (i.e., higher SAP content, higher lime content, and longer curing time).

Clogging will inevitably occur while using vacuum preloading method to process super-soft soils with high water content. How to quantitatively evaluate the effect of clogging on the consolidation behavior is a key issue to be solved. Based on NALSC (negative axisymmetric large-strain consolidation) model, considering the “internal clogging” and the “external clogging”, a calculation method by using parameter “clogging rate” to reflect clogging problem is proposed for single-well consolidation theory. Effects of clogging rate and clogging occurred time on U_s (degree of consolidation defined by strain) and U_p (degree of consolidation defined by stress) are investigated. Differences of the effect of clogging on consolidation degree are determined between large-strain and small-strain consolidation theory. The results show that, the larger the clogging rate, the smaller the degree of consolidation of the soil at the same consolidation time. Effect of clogging on U_p is greater than U_s. The earlier the clogging occurs, the smaller the degree of consolidation at the same clogging rate. Influences on the degree of consolidation for large-strain and small-strain theory are the same. Consolidation rate of soil is determined to a certain extent by the “generalized clogging parameter μ”. The “external clogging” has a greater influence on the degree of consolidation than the “internal clogging” at the same clogging rate.

The treatment and resource utilization of municipal sludge and dredged silt have been rendered urgent by the acceleration of urbanization and stricter environmental protection demands. An effective solution was developed to address the challenges of poor mechanical properties and the difficulty in directly using cement-based materials for municipal sludge treatment. The utilization of dredged silt with high water content served as the foundational skeleton material. Appropriate proportion (0.5:1.0) of sodium silicate, which accelerates cement hardening, and polyurethane, which facilitates chemical bond cooperation, was combined to form SP material, partially replacing cement. Unconfined compressive strength (UCS) tests were subsequently conducted on the solidified municipal sludge. These tests aimed to investigate the influence of the dredged silt mixing ratio, initial water content of dredged silt, and the SP mixing ratio on the strength of the solidified municipal sludge. Furthermore, a strength prediction model was established for solidified municipal sludge, taking into consideration the mixing ratios of dredged silt and SP. The research findings indicate that dredged silt can serve as a skeleton structure for solidified municipal sludge. The UCS of the solidified municipal sludge increases with the increase in the dredged silt mixing ratio, and reaches a maximum value at mixing ratio of 1.0. SP materials can partially replace cement, the appropriate proportion of SP and cement can synergistically improve the strength of solidified municipal sludge, and the optimal SP mixing ratio is 50%. Furthermore, the strength prediction model constructed with independent variables such as dredged silt mixing ratio, curing age, water-to-cement ratio, and SP mixing ratio demonstrates better predictability for the strength development of solidified municipal sludge.

In this study, unconfined compressive strength (q_u) tests were conducted to explore the coupling effect of organic matter content (3.7%, 7.7%, 10.7%, and 13.7%) and curing temperature (18 °C, 36 °C, 46 °C) on the development of early and mid-late strength of cement-solidified dredged sludge (cement-stabilized clay, or CSC). The microstructure of the CSC containing organic matter at different curing temperatures was also analyzed. The results show that q_u of CSC decreases with the increase in organic matter content (C_o). The strength growth rate of CSC in the mid-late stage (≥14 days) is small when C_o ≥ 7.7%, and it is difficult to increase this strength growth rate even if the curing temperature is increased up to 46 °C. There is a cement incorporation ratio threshold of 15% for q_u of CSC containing organic matter (C_o = 7.7%), which is not affected by curing temperature; increasing the cement incorporation ratio (to 20%) cannot increase q_u significantly. The CSC with high curing temperature has more hydration products and higher structural compactness, and it can obtain higher q_u in the early and mid-late stages. A high curing temperature can increase the early strength growth rate and shorten the curing age for CSC containing organic matter.