Bio-inspired probes have emerged as a promising solution for in-situ site characterisation, particularly in challenging terrains and extraterrestrial exploration. This study presents a viable and computationally efficient Material Point Method (MPM) framework for studying Bio-Inspired Cone Pressuremeter (BICP) probe mechanism. With its inherent advantage of particle and continuum frameworks, MPM allows seamless simulation of multi-staged BICP probe propulsion that involves large deformation. A novel implementation strategy was developed for this study to simulate the complex movement of the BICP probe in three sequential stages, including penetration, pressuremeter module expansion, and tip advancement. Sensitivity analysis was conducted to achieve an objective solution and determine the optimum mesh size and mass scaling factor for the BICP probe within the realms of current state-of-the-art MPM formulation. Furthermore, investigations were performed on the established MPM framework to study the influence of probe geometry, material state, and layered soil strata. The findings reveal that in probes with longer pressuremeter modules, larger zone of stress relaxation was observed around the cone tip during module expansion stage than their shorter or double-module counterparts. Meanwhile, the BICP probe's response during all stages in different material states corroborates its sensitivity to the soil's mechanical properties. Although the layered strata significantly influenced the BICP probe's response during the penetration and module expansion stages, it had minimal impact during the tip advancement stage.

The directional frictional anisotropy of snake-skin-inspired interfaces has great potential to improve the load-bearing performance of offshore uplift pile foundations and other engineering applications. Such interfaces are designed to withstand cyclic loads, including those induced by waves and earthquakes. To investigate the characteristics of directional frictional anisotropy of soil-structure bio-inspired interfaces under cyclic loading, a series of cyclic direct shear tests were conducted using an advanced interface cyclic shear apparatus. The study examined the effects of initial cyclic position, normal stress, bio-inspired interface morphology, and sand density on cyclic shear anisotropy, along with an initial exploration of shear strength characteristics following cyclic loading. The findings revealed that increasing initial position of the cycle and normal stress enhanced shear anisotropy under the cranial-caudal cyclic loading path, while reducing shear anisotropy under the caudal-cranial cyclic loading path. For interfaces at moderate densities, variations in the ratio of interface scale length to height exhibited negligible effects on shear anisotropy. However, as sand density increased, the influence of this ratio on shear anisotropy became more pronounced under the cranial-caudal cyclic shear path, with a slightly increased effect observed under the caudal-cranial cyclic path. Under constant stress conditions, the findings provide valuable insights for the optimization and practical application of bio-inspired interfaces in engineering projects.

Numerical modelling of laterally loaded piles requires a robust pile-soil interface model. The conventional Coulomb friction model has limitations when predicting the soil-structure interaction at shallow depths for battered mini piles (BMPs) in cohesive (fine-grained) soils. This paper proposes an efficient pile-soil interface model to simulate laterally loaded BMPs in cohesive soils using three-dimensional finite element models (FEM). BMP systems have been commonly used to support lateral load-dominated lightweight superstructures. They are hybrid foundations with BMPs oriented at different inclinations and directions, mimicking tree root systems. FEM results indicate that the Coulomb model is unsuitable for simulating the pile-soil interface at shallow depth due to underprediction of shear resistance. The proposed interface model comprising a surface-to-surface cohesive damage interface with friction captures the lateral performance of BMPs accurately. The proposed model was implemented for a range of pile and soil properties to verify its suitability in understanding the behaviour of BMPs. The ultimate lateral capacity of BMPs increases with penetration length up to 1.5 m. While an increase in diameter and undrained shear strength increases the capacity, the lateral load eccentricity negatively impacts it. Interaction diagrams are developed to serve engineers estimate the ultimate lateral capacity of BMPs.

The current study assesses the effectiveness of supplementary bio-inspired devices (BIDs) in mitigating seismic impact on resilient base-isolated structures. Initially, rigid base-isolated structures with these devices are analyzed under stationary white-noise earthquake excitation using an equivalent linearization technique, accounting for non-linear force-deformation characteristics. Performance indicators such as added stiffness, damping, and overall response mitigation are evaluated. The investigation extends to flexible base-isolated buildings subjected to filtered white-noise excitation, observing the devices' effectiveness in controlling the displacement of the isolation system. Optimal values for the limiting force of the BIDs are identified, minimizing RMS topmost floor acceleration. The findings consistently illustrate the ability of BIDs to control isolator displacement even in the challenging conditions of near-fault motions. Importantly, the results align well with the trends observed under stochastic excitation, highlighting the robustness and potential applicability of BIDs in enhancing the seismic resilience of structures. These insights contribute significantly to advancing seismic engineering practices and offer valuable implications for the development of structural control.

Recently, bio-inspired technology utilizing the anisotropy of friction between structure-soil has garnered significant attention. In particular, new pile designs not only enhance shaft friction but also gain prominence by reducing the use of cement, which has traditionally been a key material in ground treatment and improvement. Previous studies have quantitatively verified the increase in interface shear resistance through direct shear tests and cone penetration experiments. However, conventional finite element analysis methods face limitations in analyzing the shaft friction behavior between piles with scale and the surrounding soil. In this study, the Coupled Eulerian-Lagrangian (CEL) technique, a large deformation analysis method built-in ABAQUS, is employed to simulate the penetration of cone with textured shaft. Numerical analyses are conducted to investigate changes in cone penetration resistance according to the geometric characteristics of the surface scale. To minimize numerical errors occurring in the cone and surrounding soil meshes, a three-dimensional generalized mesh is proposed for the cone and its surrounding elements. A total of 13 cases, comprising seven different cone designs and two penetration direction conditions, are analyzed. The results showed that under the same penetration load, penetration depth decreased as the scale height increased, the scale length narrowed, and the scale tapered in height.

Porous materials and structures, such as subterranean fire ant nests, are abundant in nature. It is hypothesized that these structures likely have evolved biological adaptations that enhance their collapse resistance. This research aims to elucidate the collapse-resistant mechanisms of pore geometries in fire ant nests. Finite Element Models of ant nests in soil were generated using X-ray CT imaging of aluminum castings of ant nests. Representative volume elements of the ant nests, representing porous structures at various depths, were analyzed under confined compression. This work on investigating fire ant (sp. Solenopsis Invicta) nests found them to be hierarchical and graded at various depths that affect how they resist loads and collapse. The top portion acts as a protective shield by distributing damage and absorbing energy. In contrast, the lower chambers localize stress, contributing to damage tolerance. This research provides evidence to suggest that ant nests have developed properties that allow them to resist collapse. These findings could inform the design of lightweight and durable cellular structures in various engineering fields.

Foundation elements with rough (textured) surfaces mobilize larger interface shear resistance than ones with conventional smooth or random rough surfaces when sheared against soils under monotonic loading. The overall performance of foundation elements such as piles supporting offshore wind turbines, suction caissons supporting tidal energy converters, soil nails, and soil anchors installed in cohesive soils could be enhanced through utilizing rough (textured) surfaces to resist applied static and/or cyclic loading. This paper describes the shear behavior of smooth and rough (textured) surfaces in kaolinite clay and kaolinite clay-sand mixture soils under static and cyclic axial loading. The experimental investigation presented herein consists of a series of interface shear tests performed on 3D printed rough (textured) surfaces and a 3D printed smooth reference surface utilizing the Cyclic Interface Shear Test system. The paper includes a description of the interface testing system components, cohesive soil specimens' preparation procedure, smooth and rough (textured) surfaces details, testing procedure, and results of static and cyclic tests. Test results indicate that kaolinite clay-sand mixture soil mobilized larger static and post-cyclic interface shear resistance and volume contraction relative to kaolinite clay soil when sheared against the smooth reference surface. When tested against rough (textured) surfaces with variable asperity height, larger shear resistance was mobilized and larger soil dilation greater than that mobilized by the reference untextured surface in both soils. The results also indicate rough (textured) surfaces exhibited a prevalent frictional anisotropy increases with asperity angle and height in cohesive soils, the surfaces mobilized larger shear resistance and volume change in one direction (i.e., against the asperity right-angled side) than the other direction (i.e., along the asperity inclined side).

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.

Traditional geotechnical engineering is challenged in terms of sustainability, resilience, reliability and resources availability in the context of climate change and urbanization expansion. Abstracting inspiration from nature and adopting to geotechnical engineering, bio-inspired geotechnics can provide innovative solutions to address these challenges. This paper reviews the underlying mechanics of bio-inspired geotechnical engineering from three perspectives, i.e., bio-inspired burrowing strategies and mechanisms, bio-inspired surfaces with textures and bio-inspired underground structures. The results highlight that the bio-inspired burrowing strategies (i.e., particle removal, chiseling/grabbing-pushing, peristalsis, dual-anchor, pivot burrowing, undulatory propulsion, reciprocating, rotation and root growth) differ in their application scopes and burrowing efficacy, and the auxiliary burrowing, the principle of least impendence, as well as the multi-functional root growth presents promising solutions to burrowing challenges. Bio-inspired textured surfaces exhibit performance enhancement with regard to anisotropic friction, wear resistance and actuator initiation. In bio-inspired underground structures, snakeskin- and root-inspired geotechnical elements provide superior performance due to the frictional anisotropy and branching effects, respectively, and the potential implementation techniques are challenging current geotechnical engineering. Finally, transferring issues, potential research trends and future prospects are presented, and the significance of collaborative engagement of both engineers and scientists for promotion in bio-inspired geotechnics is emphasized. (c) 2024 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

Deep foundation and anchorage systems are often comprised of simple linear elements, limited by design, materials and techniques employed to build them. Their stability is attained by transferring structural loads to deeper, more stable soil layers across a larger area, reducing potential for excessive settlement and providing resistance against lateral forces from external factors including wind and earthquakes. In comparison, root systems distribute loads to a large volume of soil through a branched morphology of semiflexible elements. Roots also penetrate soil media, reduce erosion, create habitats, and exchange, store and transport resources, while continuously sensing and adapting to environmental conditions. Insights from their integration of multifunctionality can be transferred to civil engineering through biomimicry. As a first step toward designing root-inspired foundations, the effects of various morphological traits (laterals' length, number of nodes, number of laterals, branching angle and laterals' cross section) on foundation performance are evaluated through vertical pullout tests. Out of the model properties, general trends were observed, including the positive correlation between models' surface area and maximum force reached. Yet, due to complex interactions between the model and granular media, no model property fully explained differences in pullout resistance of all models. The effects of each root trait on pullout resistance were analyzed separately, which can serve to adapt the design of root-inspired foundations and exploit granular physics principles. Potential reasons for surprising and counterintuitive results are also presented. Further studies could evaluate the assumptions given as potential explanations of these results by studying identified counterintuitive scenarios.