To decrease the environmental impact and increase the high-quality resource utilization of construction spoil (CS), the alkali-activated slag (AAS) was selected to solidify CS and prepare solidified construction spoil (SCS). SCS with certain working and mechanical properties can be used as building materials, such as unsintered bricks. However, the preparation of SCS is inefficient, mainly because the properties of SCS are affected by various factors, and the formula is difficult to determine. This study intensively investigated the effects of the liquid-solid ratio (W/ (B + S)), clay content of CS, and binder-soil ratio (B/S) on the flowability and compressive strength of SCS. It was found that W/(B + S) was the main factor controlling compressive strength, and both W/(B + S) and clay content significantly affected the flowability of SCS. Based on an assumption for the flowability prediction method and the relationship between flowability and liquid-solid ratio of CS, AAS, and SCS, a method to predict the flowability of SCS was proposed and validated. Additionally, the extended Abrams' law was applied to fit the compressive strength variation of SCS. Combining the flowability prediction method and the extended Abrams' law, a novel formula design method for SCS was proposed and proven effective in validation experiments.

The process of permeation damage of the filling medium in the fracture is critical to the stability of the fractured rock mass. This study focused on the seepage failure process of filling materials in fractures and faults. To investigate the effects of axial stress and clay content, a series of experimental tests were conducted on internally unstable granular soil specimens with different clay contents under different axial stresses. The variations of flow rate and hydraulic conductivity were recorded and analyzed during the tests, and the typical process of seepage failure was summarized. The flow rate, hydraulic conductivity, and their growth rates were found to be smaller under high axial stress compared to low axial stress, and the flow rate of samples with higher clay content was smaller than those with lower clay content. Initially, the hydraulic conductivity decreased slightly due to clay and fine particle rearrangement, and remained nearly constant when the hydraulic gradient was small. However, as the hydraulic gradient increased, the hydraulic conductivity began to increase in response to the loss of clay and fine particles.

In the marine environment, the seabed contains a certain amount of clay. Experimental studies show that the liquefaction susceptibility of the sandy seabed increases as clay content (CC) rises to a certain threshold, beyond which further increases in CC reduce liquefaction susceptibility. However, numerical models that describe the effect of CC on seabed liquefaction are very limited. This study proposed a dynamic poro-elasto-plastic finite element method model for analyzing liquefaction in the sandy seabed with CC below the threshold. Based on a series of undrained triaxial compression tests on sand-clay mixtures from existing literature, a unified constitutive framework was demonstrated to be effective for describing the liquefaction behavior of sand with low CC using one set of model parameters. Existing wave flume model tests validated the effectiveness of the proposed seabed model in describing the effect of low CC on excess pore water pressure (EPWP). Numerical results confirmed that adding a small amount of clay to the seabed increased the soil contraction and thus its liquefaction susceptibility. Wave-induced liquefaction was limited to a certain depth of the seabed, and the liquefaction depth was significantly affected by the CC . Adding a low content of clay the sandy seabed significantly increased both horizontal and vertical displacements under wave action, potentially leading to the instability of the seabed. This study provides a new method for accurately assessing the wave-induced stability of marine structures built on the sandy seabed containing certain amounts of clay.

Rice is threatened by ineffective inputs of water and fertilizers. Therefore, we detected the effect of soil clay content on plant physiological traits and their relationships to phosphorus (P) utilization -efficiency of rice under different irrigation options. Thus, our experiment was conducted in a two -factor randomized complete block design. The first factor was irrigation method, including three choices: alternate wetting/critical drying (AWCD) (50% drying), alternate wetting/sharp drying (AWSD) (30% drying), and alternative wetting/minor drying (AWMD), (10% drying). The second factor was soil clay amount, with three levels at 65, 50, and 30%, corresponding to SHC, SMC, and SLC. The root 's growth and activity were lower in AWCD x SLC than in AWMD x SHC. While the former treatment decreased the P content in soil, the latter increased their availability. The glutamine synthetase (492.5 mu mol g -1 h -1 ) was lower in AWCD x SLC than in AWMD x SHC at 1006.1 mu mol g -1 h -1 , leading to the increase of oxidative cell damage. The optimal P nutrition improved plant growth under AWMD x SHC. The AWCD x SLC led to the minimum agronomic efficiency of P (PAE, 13.67 g/g) and the apparent recovery efficiency of P (PARE, 1.55%). However, the maximum values of PAE (44.05 g/g) and PARE (21.45%) were detected in AWMD x SHC. This study suggests that increasing soil clay content encourages the growth, yield, and P uptake of rice under alternate wetting/minor drying irrigation. The study has excellent application potential, providing technical support for precision water and P fertilizer management of rice.

Geological hazards such as gully erosion, collapse and slope failure occur frequently in loess areas, which are closely related to the soil disintegration characteristics. Understanding the impact of freeze-thaw and wet-dry action on soil disintegration in the context of climate change is essential to establish effective soil and water conservation strategies and prevent engineering geological hazards in loess areas. In this study, sodic-saline loessial soils with different clay content were subjected to freeze-thaw and wet-dry cycles, followed by aggregate durability tests, direct shear tests and disintegration tests to investigate the effects of the two natural processes on soil disintegration characteristics. The results showed that the samples subjected to freeze-thaw cycles primarily exhibited rapid and stable disintegration, followed by slow disintegration, whereas the samples subjected to wet-dry cycles revealed weight gain, continuous slow disintegration and eventual sudden disintegration. Freeze-thaw action continuously deteriorated the disintegration resistance of soil, while wet-dry action improved the disintegration resistance of soil after the first cycle, and gradually weakened it in subsequent cycles. Statistical analysis showed that, for samples undergoing freeze-thaw cycles, the number of cycles and clay content were positively correlated with the disintegration rate, while the aggregate durability was negatively correlated with the disintegration rate. For samples undergoing wet-dry cycles, the number of cycles had a positive effect on the disintegration rate, while the clay content, shear strength and cohesion had a negative correlation with the disintegration rate. At a certain clay content, there was a positive correlation observed between the surface crack ratio, crack length and width with the disintegration rate of the wet-dry samples, while shear strength and cohesion had a negative correlation with the disintegration rate of both freeze-thaw and wet-dry samples. Furthermore, the study outlined the disintegration mechanism of loessial soils based on internal factors, driving factors, resistance factors and evolutionary factors. This study contributes to the in-depth understanding of the catastrophic mechanism of geological hazards in cold and arid areas and provides experimental evidence for its control and management. The study outlined the disintegration mechanism of loessial soils based on internal factors, driving factors, resistance factors and evolutionary factors. image

Shear strengths of silty soil were determined for shallow destruction of the soil sites frequently occurring in the Central Plains area. Specimens were prepared with five different clay contents (5, 10, 15, 20, and 25%) prior to compaction at dry densities of 1.60, 1.70, and 1.80 g/cm3. Soil specimens were saturated and then the consolidated undrained shear test was conducted with eight confined pressures ranging from 1 to 400 kPa. Results indicate that the shear strength increases significantly as the clay content increases from 5 to 25%, and the cohesion c shows bilinear function with the inflection point at the clay content of 10%. The difference of cohesion in the high and low stress sections decreases gradually to almost the same value until 25% of the clay content, while the internal friction angle phi decreases with the increase in clay content. Within the range of dry density and clay content tested, the shear strength of silty soil in the low stress range obtained is higher than the measured value. Therefore, for the shallow damage of soil site, the shear strength parameters should consider the low stress test conditions. The bilinear growth of cohesion c with clay content can be attributed to the changes from sand-like soil to clay-like soil with the skeleton of soil specimen transitioning from sand particles to clay grid when the clay content exceeds approximately 10% combined with the results of scanning electron microscopy.

Climate change brought about significant freeze-thaw (FT) deformation of clayey soils distributed in cold regions, which resulted from soil structure evolution including pore size distribution change and crack development. However, the formation of clay aggregate that dominates the soil deformation behavior during FT remains unclear. This study investigated the effects of clay contents (5 %, 10 %, 15 %, and 20 %) and subfreezing temperatures (-5 degrees C, -10 degrees C, and -15 degrees C) on the soil FT deformation properties by isotropic isothermal FT tests. Meanwhile, the soil structure evolution was characterized via Nuclear Magnetic Resonance and X-ray Computed Tomography. The results indicated that the frost heave ratio (eta) and thaw settlement coefficient (delta) non-linearly varied with clay content and subfreezing temperature. Specifically, the minimum eta and delta were observed in the specimen with 10 % clay content, and the maximum eta and delta were identified at -10 degrees C. This phenomenon can be attributed to the clay aggregate forming bimodal or unimodal pore size distribution (PSD) with different initial clay contents. The freezing characteristics of inter- and intra-aggregate pore water were determined by the solidwater interaction. Moreover, the FT action altered the structure of clayey soil by the change in PSD and the generation of cracks. The contribution of pore size change and crack development to the total volume change before and after FT was quantitatively analyzed. It demonstrated that pore size change was more important for the total volume change in specimens with lower clay content and higher subfreezing temperature, whereas crack development mainly contributed to the total volume change in the rest of the specimens. This study provides a deep insight into the deformation characteristics of clayey soils under different climate conditions in cold regions.

Clay is widely encountered in nature and directly influences seepage behaviors, exerting a crucial impact on engineering applications. Under low hydraulic gradients, seepage behaviors have been observed to deviate from Darcy's law, displaying a non-linear trend. However, the impacts of clay content on non-linear seepage behavior and its pore-scale mechanisms to date remain unclear. In this study, constant-head seepage experiments were conducted in sand-clay porous media under various hydraulic gradients. Low-field nuclear magnetic resonance (LF-NMR) technology was utilized to monitor the bound-water and free-water contents of sand-clay porous media under different seepage states. The results show a threshold hydraulic gradient (i(0)) below which there is no flow, and a critical hydraulic gradient (i(cr)) below which the relationship between the hydraulic gradient (i) and seepage velocity (v) is non-linear. Both hydraulic gradients increased with clay content. Moreover, the transformation between bound water and free water was observed during the seepage-state evolution (no flow to pre-Darcy or pre-Darcy to Darcy). As the hydraulic gradient reached the i0, the pore water pressure gradually overcame the adsorption force of the bound-water film, reducing the thickness of the bound-water film, and causing non-linear seepage behavior. When i(0) < i < i(cr), the enlarging hydraulic gradient triggers the thinning of bound water and enhances the fluidity of pore water. Moreover, the increasing clay content augments the bound-water content required for the seepage state's change.

The content of clay particles has a key influence on the physical and mechanical properties of microbial solidified granite residual soil. Microbial-induced calcite precipitation (MICP) treatment method of mixing + grouting was used to prepare microbial solidified granite residual soil samples with different clay contents and to explore the influence of clay content on the reinforcement effect of microbial solidified granite residual soil. A series of direct shear tests, disintegration tests, and microscopic observation tests was conducted to quantitatively analyze the influence of clay content on the shear strength and disintegration resistance of microbial solidified granite residual soil. The conclusions are summarized as follows: the shear strength and disintegration resistance of granite residual soils solidified by MICP treatment were remarkably improved, with the shear strength increasing by 9%similar to 16% when the clay content varied from 10%similar to 40%. The internal friction angle of the granite residual soil with different clay contents increased and then decreased with the increase in clay content. The cohesion of the microbial solidified granite residual soil increased with the increase in clay content, and the internal friction angle reached a minimum of 20% clay content (17.27 degrees), which is 31.85% lower than that of 0% clay content (25.34 degrees). The cohesion of the microbial solidified granite residual soil reached a maximum of 40% clay content (39.54 kPa), which is 8.69 times higher than that of 0% clay content (4.55 kPa). The MICP treatment technology is capable of effectively improving the shear strength and disintegration resistance of granite residual soils. The MICP treated process produces calcium carbonate precipitates that link the sand particles and fill the pores between the soil particles, increasing the number of larger agglomerates in the granite residual soil, which is the essential reason for the improvement in the softening and disintegration of the granite residual soil when exposed to water.