The anisotropy of shear resistance depending on friction direction can be selectively utilized in geotechnical structures. For instance, deep foundations and soil nailing, which are subject to axial loads, benefit from increased load transfer due to greater shear resistance. In contrast, minimal shear resistance is desirable in applications such as pile driving and soil sampling. Previous studies explored the shear resistance by interface between soil and surface asperities of a plate inspired by the geometry of snake scales. In this study, the interface friction anisotropy based on the load direction of cones with surface asperities is evaluated. First, a laboratory model chamber and a small-scale cone system are developed to quantitatively assess shear resistance under two load directions (penetration -> pull-out). A preliminary test is conducted to analyze the boundary effects for the size of the model chamber and the distance between cones by confirming similar penetration resistance values at four cone penetration points. The interface shear behavior between the cone surface and the surrounding sand is quantitatively analyzed using cones with various asperity geometries under constant vertical stress. The results show that penetration resistance and pull-out resistance are increased with a higher height, shorter length of asperity and shearing direction with a decreasing height of surface asperity.

Constructing infrastructures such as traffic and railway gantries, transmission towers, and near-shore sea walls on soft soils, demands specially designed foundation systems capable of withstanding pull-out forces. Plate anchors are crafted for such environments. It consists of a steel plate embedded in the soil and connected to the external structure through a tie-rod. These anchors have become increasingly prevalent in engineering projects designed to withstand the pull-out forces from the superstructure. The present study investigates the vertical pull-out response of embedded anchors, subjected to cyclic disturbances, using three-dimensional finite element analysis. Advanced constitutive models, including the Soft Soil (SS) model and Hardening Soil model with small-strain stiffness (HSsmall), are employed to study the non-linear and time-dependent response of soils under monotonic and cyclic pull-out loads. The numerical analysis indicates that, in addition to soil type and anchor size, the placement and nature of loading, influence the anchor capacity. It was noted that under cyclic loads, anchors buried in saturated soft soils display a non-linear hysteresis response and a degradation in pull-out resistance with loading cycles. This reduction in anchor resistance with an increment in the loading cycle is noted when the anchor is subjected to higher cyclic stresses. A series of numerical investigations were carried out to analyse the impact of reinforcing the soil above the anchor with geotextile. This approach aimed to address the challenges associated with soft soils and enhance the performance of anchor-soil foundation systems under different loading scenarios. The results highlight the substantial role of geotextile reinforcement in enhancing anchor stability and resistance against vertical pull-out and cyclic disturbances. Reinforcing the soil above the anchor plate amplifies the pull-out resistance up to 45%, in contrast to anchors placed in unreinforced soil. In addition, the anchors exhibit improved performance under cyclic loads, with an enhancement in cyclic pull-out resistance up to 29%, without causing additional degradation of the soil's shear strength under repeated cyclic loading. This improvement in cyclic pull-out resistance is attributed to the resilient cyclic characteristics of geotextile reinforcement.

The interface between plants' roots and soil is strongly affected by rhizodeposits, especially mucilage, that change mechanical and hydrological behaviour. In addition to impacts to aggregation, water capture and root penetration, rhizodeposits may also affect the pull-out resistance of plant roots. Due to the complex architecture of plant roots and an inability to restrict rhizodeposit production, this study used a simplified system of wooden skewers to simulate roots and chia seed mucilage as a model to simulate rhizodeposit compounds. Pull-out tests were then carried out to measure the impacts of mucilage, and one (WD1) or two (WD2) cycles of wetting and drying of soils. Using a mechanical test frame, the maximum pull-out resistance (Fmax) and pull-out displacement (dL) were recorded, allowing for pull-out energy (E), average pull-out force (F over bar $$ \overline{F} $$) and bond strength (tau max) to be calculated. The results showed that all pull-out parameters of the samples with added rhizodeposit compounds tended to decrease between WD1 and WD2, but they were still significantly greater than without the added mucilage. The model rhizodeposit increased all pull-out parameters by a minimum of 30%. With an additional wet-dry cycle, the mucilage tended to cause a decline in pull-out parameters relative to a single wet-dry cycle. This suggests mucilages could enhance the mechanical resistance of roots to pull-out, but resistance decreases over time with cycles of wetting and drying. To conclude, an important role of mucilage is pull-out resistance, which has relevance to plant anchorage and root reinforcement of soils.

Strong winds, particularly in the absence of disaster-resistant designs, significantly impact the stability of greenhouse foundations and eventually lead to structural damage and potential harm to crops. As a countermeasure, rebar stakes are commonly used to reinforce the foundations of non-disaster-resistant greenhouses. This study evaluates the pull-out resistance (Rpull-out) of rebar stakes considering various factors like soil compaction, embedded length, installation duration and angle, and changes in soil water content against uplift pressure by strong winds. A combination of field (i.e., the cone penetration test and rebar stake pull-out test) and laboratory (i.e., the compaction test, soil compaction meter test, and soil box test) tests are performed for the assessment of Rpull-out. The results indicate that Rpull-out increases with higher soil compaction, greater embedded length, longer installation duration, and an inclined installation angle. The soil compaction exerts the most significant impact; 90% to 100% of the soil compaction rate has approximately 10 folds higher Rpull-out than the 60-70% compaction rate. If the embedded length is increased from 20 cm to 40 cm, there is a two-fold increase in the average of Rpull-out. Inclined installation of rebar stakes increases Rpull-out by 250% to 350% compared to vertical installation, and rebar stakes installed prior to the uplift event have 1.5 to 6.4 fold increases in Rpull-out than those with instant installation. Additionally, we observed variations in the surface soil moisture due to climatic changes introducing variability in Rpull-out. These findings lead to the proposition of efficient rebar stake installation methods, contributing to the enhanced stability of a greenhouse.