This paper presents the results of experimental testing of adobe masonry assemblages to study their flexure and bond behaviors. The properties of soil and water absorption of adobe units also were investigated. The plasticity index of the soil was 7.56, which was higher than that reported for the adobe soil in a few regions of the world. The silt and clay contents of the soil also were higher than those of the soil used by researchers elsewhere. High water absorption of the adobe units (27.37%) indicated their low cohesion characteristic, which was evidenced by low bond strength. The flexural strength of the wallettes tested in a direction parallel to the bed joints was less than that of those tested perpendicular to the bed joints. The tensile bond strength determined by the bond wrench method was considerably smaller than the flexural strength of the wallettes. The observed flexural and bond strengths of the adobe masonry also were smaller than those reported in the literature.

Mucilage offers several beneficial functions for soils, yet its impact on soil mechanical behavior remains underexplored. This study investigated the effects of chia seed mucilage on the plasticity index (under normal conditions) and penetration resistance (under compaction) of sandy clay loam soils with differing soil organic carbon (SOC) levels from Akhtar Abad (SOC = 1.6%) and Najm Abad (SOC = 0.6%) in northern Iran. Four mucilage concentrations (0, 1 g kg-1, 3 g kg-1, 5 g kg-1) and three compaction pressures (100 kPa, 300 kPa, 600 kPa) were used. We found that mucilage significantly increased the plasticity index, with a 5.8% increase at 1 g kg-1 in the Najm Abad soil and 2.6%-3% increases at higher concentrations in the Akhtar Abad soil. At a concentration of 3 g kg-1, soil penetration resistance in the Akhtar Abad soil increased by 0.9 MPa and 1.6 MPa at compaction pressures of 300 kPa and 600 kPa, respectively. In the Najm Abad soil, a concentration of 5 g kg-1 led to increases of 0.7 MPa and 1.7 MPa at compaction pressures of 300 kPa and 600 kPa, respectively. No significant relationship was found between soil penetration resistance and soil plasticity index. The mucilage-induced increase in soil plasticity may hinder soil workability, especially when tillage occurs immediately after crop harvest. Mucilage can also increase soil resistance to root penetration in areas compacted by heavy machinery. To mitigate these risks, we recommend performing tillage and machinery operations in both agricultural and forest ecosystems during dry periods, when mucilage is less active, to minimize its negative impact on soil workability and compaction.

The problem of subgrade mud pumping under the action of train loads is common and challenging to cure. In order to investigate the occurrence condition and the mechanism underlying the development of mud pumping, the characteristics of 23 groups of soils prone to mud pumping were analyzed. Moreover, findings indicate that most of the soils have the following characteristics: (1) clay content is greater than 2%, and silt content is greater than 20%; (2) the liquid limit ranges between 23 and 75%, and the plasticity index varies between 5 and 42.5; (3) the permeability coefficient is between 3.28 x 10-8 cm/s and 1.39 x 10-4 cm/s; (4) the main mineral components of the mud pumping soils are illite, montmorillonite, and kaolinite; and (5) the saturation of the mud pumping soil is generally greater than 80%. In addition, silty clay was selected to carry out the subgrade mud pumping test. The results show that under cyclic loading, there is an excess pore water pressure gradient in the subgrade soil, which mobilizes the fine particles in the subgrade soil, especially in the upper part of the subgrade soil, to migrate with the water flow, forming mud, and eventually resulting in subgrade mud pumping.

Inherent (fabric) anisotropy is one of the most important properties of earthen materials that significantly influences their strength and stiffness characteristics. In this study, a comprehensive series of unconfined and constrained compression tests is performed on normally consolidated (NC) clay samples with different plasticity indices to examine the effect of inherent anisotropy on their mechanical characteristics. Accordingly, several cylindrical clay samples with different proportions of kaolinite and bentonite are reconstituted at a wide range of deposition angles, and then subjected to both unconfined and constrained compressive loadings. The experimental results reveal that, for a clay sample with a particular plasticity index, the highest and lowest values of unconfined compressive strength (UCS), secant modulus (E50), and constrained Young's modulus (Eoed) are associated with deposition angles of 0 degrees and 90 degrees, respectively. The results also show that at a certain bedding plane angle, the sample containing 30 % bentonite (PI = 110 %) exhibits the highest UCS, E50, and Eoed values. Several practical empirical correlations are developed to estimate the strength and stiffness properties of NC clays based on their plasticity indices and bedding plane directions. Furthermore, Scanning Electron Microscopy (SEM) analysis is conducted to explore the microstructure of samples containing varying percentages of kaolinite and bentonite.

Salinity and sodicity greatly influences ongoing physical processes in soils. Organic matter may rehabilitate physical and mechanical properties of soils. Vermicompost as an amendment influences moisture-related parameters including consistency (plastic - PL and liquid limit - LL) and compaction. This study was conducted on soils (sandy-clay-loam) treated with different salinity levels (0.58 (control - irrigation water quality, tap water), 4 and 8 dS m(-1)) to investigate the effects of different vermicompost doses (0% (control), 2.5% and 5% w/w) on soil consistency limits and compaction. The pot experiment was carried out in a total of 27 pots, i.e. 3 (vermicompost doses) x 3 (salinity levels) x 3 (number of replicates). For Proctor compaction properties, maximum dry bulk density (MDD) reduced and optimum water contents (OWC) increased with increasing vermicompost doses under different salinity levels (p < .01). Increasing vermicompost doses under the lowest salinity level (0.58 dS m(-1)) yielded increasing optimum water contents for control (LL = 35.93% and PL = 25.85%). Optimum water contents were determined as 42.19% (LL) and 29.93% (PL) for 2.5% vermicompost dose and as 47.33% (LL) and 36.01% (PL) for 5% vermicompost dose under the lowest salinity level. LL, PL, OWC and MDD were significantly affected by vermicompost x salinity interactions. The highest maximum dry bulk density (1.92 g cm(3)) and the lowest optimum water contents (13.50%) were obtained from 0% vermicompost under the 8 dS m(-1) NaCl level. Mean weight diameter (MWD) values ranged from 0.690 mm for 0% VC treatment under high Na salt level (8 dS m(-1) NaCl) to 0.821 mm for 5% VC treatment under lowest Na salt level (0.58 dS m(-1) NaCl). The correlations between aggregate stability (particle size group 1-2 mm) and optimum water content were 0.647*, 0.587* and 0.598* as compared to correlations of -0.512*, -0.470*, and -0.617** between aggregate stability (particle size group 1-2 mm) and maximum dry bulk density for the 0, 4 and 8 dS m(-1) NaCl levels, respectively. MWD was positively correlated with OWC (0.386*) and negatively correlated with MDD (-0.385*). The greatest (2.39%) and the lowest (0.32%) soil organic matter values were respectively observed in 5% VC under the lowest salinity level (0.58 dS m(-1)) and 0% VC with at high Na salt level (8 dS m(-1) NaCl). It was concluded that vermicompost reduced compaction-induced damage in soils.

Expansive soils pose significant challenges in geotechnical engineering due to their high swelling and shrinkage potential, damaging structures and infrastructure. While various methods have been employed to address these issues, nano-conditioning using nanoparticles presents a promising avenue. Nanoparticles, due to their small size and large specific surface area, can interact profoundly with soil, impacting its physical, mechanical, and hydraulic properties. Due to the limited information available on the effects of nano-conditioning on expansive soils, our research adopts an extensive literature review approach. This approach involves gathering data and studies related to the use of nano-conditioning for general soil treatment, with a focus on factors pertinent to expansive soils' behavior. The results reveal the complex and context-dependent nature of nanoparticle-soil interactions. Nano-conditioning can enhance certain properties, like compressive strength and elastic modulus, while its impact on parameters such as plasticity index, cohesion, and friction angle varies depending on nanoparticle type and concentration.