This paper studies the changes in the loss on ignition (LOI), total nitrogen content (TN), and strain in a one-dimensional consolidation test on peat soil. The effects of small-range fluctuations in the ambient temperature and changes in the sample height on the consolidation process of peat soil are proposed and verify the inhibitory effect of thymol on the decomposition of organic matter. The results show that when the ambient temperature fluctuates in a small range, the consolidation rate is significantly affected. Under a low load, the ambient temperature increases by 1–2 °C, and the consolidation rate can be increased by up to 10 times. This study presents the changes in loss on ignition (LOI) and total nitrogen content (TN) during consolidation, which proves that soaking the samples with a thymol solution can effectively control the decomposition of organic matter in peat soil. The strain of peat soil at a height of 30 mm is greater than or equal to that of other height samples, while that of mucky soil is 20 mm. Therefore, 30mm is the recommended sample height for peat soil for the one-dimensional consolidation test.

Most areas of Caofeidian (Tangshan Caofeidian New District in Hebei Province, China) were formed by land reclamation, where the dredger fill has a high water content and a high salt content. The solidification of Caofeidian’s dredger fill is difficult because of salinisation, as well as environmental and economic factors. This article proposes a composite slag solidifying agent. The optimal proportion of various additives was determined by an unconfined compression test and orthogonal design. Next, a microanalysis was carried out by SEM and XRD tests to characterise the solidification mechanism of the composite slag solidifying agent. The results reveal that the composite slag solidifying agent can substantially improve the unconfined compressive strength of Caofeidian’s saline dredger fill by imparting a good microstructure: a compact overall structure was obtained and few voids were observed in the solidified soil. The optimal proportion was determined as 10% slag + 1.0% quicklime + 0.8% sodium silicate + 1.5% gypsum powder. In addition, the composite slag solidifying agent can effectively reduce the content of soluble salts in saline dredger fill and substantially improve the engineering characteristics of solidified soil.

Peat soil exhibits significant creep deformation, and its consolidation law differs from that of soft soil. This study examines the strain characteristics of peat soils during three stages of consolidation using indoor one-dimensional creep consolidation tests. The results showed that the rebound deformation after the primary consolidation stage and the secondary consolidation stage is equivalent to the deformation seen during the primary consolidation stage, about 1.003 times. However, once the deformation stabilizes, the rebound deformation decreases to 0.32–0.85 times that of the deformation observed during the primary consolidation stage. The elastic and time-independent plastic strains of the peat soil showed two-stage linear changes with ${\ln \mathsf{\sigma }}_{\mathrm{z}}^{\prime }$. When the load was greater than the pre-consolidation pressure, the deformation modulus increases by approximately 2.10 and 1.56 times, respectively. On this basis, this study, for the first time, defines the creep rate according to the strain rate in the tertiary consolidation stage in the strain versus the time curve (${\epsilon }_z~t$). Based on the timeline, a one-dimensional creep consolidation model is established that can accurately predict the strain during the consolidation of the peat soil foundation. The results reveal distinct strain behaviors during each stage and improve the theoretical basis for the study of creep.

Directed against the practice actuality of deep jet cement in different soft areas, the paper selects two typical soils --mud soil and saturated loess in northwest China, through FEM analysis and in-situ test, compares the stress property of the composite ground formed by deep jet cement pile in different areas. The calculated and in-situ test results as follow: first, the stress ratio of end-bearing pile composite ground is bigger than that of floating pile composite ground; second, the stress ratio in the saturated loess composite ground is bigger than that in the mud soil composite ground when they have same replacement ratio and load; third, the failure mode of the composite ground under the flexible foundation is resulted by the failure of the soil in the ground and this is different from the composite ground under the rigid foundation.

Previous studies have shown that over-wet soil is challenging to compact and exhibits large creep deformation. The consolidation test of small specimens cannot accurately reflect the compression law, and creep is underestimated owing to size effects, which affects the engineering quality. In order to accurately analyze the compression process of over-wet soil and establish its settlement calculation method, this study focuses on over-wet soil in Anhui Province, China, and uses a large-sized tester to load and analyze its compression law. The thermogravimetric analysis method was employed to investigate the changes in water with different binding forces during the compression process, and the settlement calculation method for over-wet soil was explored. The results show that the creep of over-wet soil is large and long-lasting, and the three-stage consolidation division method based on the $d-t$ curve is more effective in analyzing its regularity. The creep of over-wet soil is directly proportional to its water content. When the load exceeds the pre-consolidation pressure, the creep deformation becomes more significant, accounting for about 60% of the deformation under a single level load. It is recommended to use the creep coefficient ($\lambda$) for calculation. The results of the thermogravimetric analysis indicate that during the primary consolidation stage, free water is discharged, and weakly bound water is mainly discharged during the third consolidation stage, which is the main cause of creep. Finally, based on the relationship between the creep strain and water content of large samples, a calculation method for the settlement of over-wet soil foundations based on the layered summation method was established, which had a higher prediction accuracy than the conventional layered summation method. The results of this study will help clarify the deformation process and principle of over-wet soil and improve the quality of engineering.