Recent studies have highlighted the potential benefits of allowing inelastic foundation response during strong seismic shaking. This approach, known as rocking isolation, reduces the moment at the base of the column by transferring the plastic joint beneath the foundation and into the soil bed. This mechanism acts as a fuse, preventing damage to the superstructure. However, structures with a low static safety factor against vertical loads (FSv) may experience unacceptable settlements during earthquakes. To address this, shallow soil improvement is proposed to ensure sufficient safety and mitigate risks. In this study, a small-scale physical model of a foundation and structure (SDOF model, n = 40) was placed on dense sandy soil, and seismic loading was simulated using lateral displacement applied by an actuator. A group of short-yielding piles with varying bearing capacities (QU/NU = 0.1-0.8) was installed beneath the rocking foundation. The results of the small-scale tests demonstrate that the use of short-yielding piles during seismic loading reduces the settlement of the shallow foundation by up to 50% and increases rotational damping by 59%. This is achieved through the frictional yielding of the pile wall and the yielding of the pile tip, which dissipate energy and enhance the overall seismic performance of the foundation. The findings suggest that incorporating yielding pile groups in the design of rocking foundations can significantly improve their seismic performance by reducing settlement and increasing energy dissipation, making it a viable strategy for enhancing the resilience of structures in earthquake-prone areas. The optimal bearing capacity ratio (QU/NU = 0.25-0.5) provides a straightforward guideline for designing cost-effective seismic retrofits.

Soft wet grounds such as mud, sand, or forest soils, are difficult to navigate because it is hard to predict the response of the yielding ground and energy lost in deformation. In this article, we address the control of quadruped robots' static gait in deep mud. We present and compare six controller versions with increasing complexity that use a combination of a creeping gait, a foot-substrate interaction detection, a model-based center of mass positioning, and a leg speed monitoring, along with their experimental validation in a tank filled with mud, and demonstrations in natural environments. We implement and test the controllers on a Go1 quadruped robot and also compare the performance to the commercially available dynamic gait controller of Go1. While the commercially available controller was only sporadically able to traverse in 12 cm deep mud with a 0.35 water/solid matter ratio for a short time, all proposed controllers successfully traversed the test ground while using up to 4.42 times less energy. The results of this article can be used to deploy quadruped robots on soft wet grounds, so far inaccessible to legged robots.

The disordered nature of granular materials poses great difficulty to the accurate characterization of microscopic structures. Despite numerous handcrafted structural indicators, the relationship between particle-scale structure and dynamics, as well as the structural origins of complex constitutive behaviors, remain subjects of debate. In this paper, we utilize a Graph Convolutional Neural Network (GCNN) to establish the structure-property relationship within granular materials. The GCNN model effectively identifies active particles exhibiting intense nonaffine activities based solely on initial particle positions, without relying on handcrafted features. Additionally, we derive a structural indicator called susceptibility from the GCNN output, which quantifies the fragility of local structures to external stimuli and enables the characterization of structural evolution during the shearing process. We demonstrate that structural defects with high susceptibility tend to form spatial clusters, and the distinct failure modes in dense and loose granular assemblies are driven by the differing spatiotemporal evolution of these defect clusters. Our findings suggest that the structural origin of macroscopic yielding in dense granular materials lies in the formation of system-spanning defect clusters, which facilitates the percolation of highmobility zones and the development of shear bands. Finally, our study indicates that graphbased neural networks are well-suited for modeling and predicting the complex behaviors of granular materials, providing a powerful approach to uncovering underlying mechanisms and deepening our understanding of these materials.

The polyurethane foam (PU) compressible layer is a viable solution to the problem of damage to the secondary lining in squeezing tunnels. Nevertheless, the mechanical behaviour of the multi-layer yielding supports has not been thoroughly investigated. To fill this gap, large-scale model tests were conducted in this study. The synergistic load-bearing mechanics were analyzed using the convergenceconfinement method. Two types of multi-layer yielding supports with different thicknesses (2.5 cm, 3.75 cm and 5 cm) of PU compressible layers were investigated respectively. Digital image correlation (DIC) analysis and acoustic emission (AE) techniques were used for detecting the deformation fields and damage evolution of the multi-layer yielding supports in real-time. Results indicated that the loaddisplacement relationship of the multi-layer yielding supports could be divided into the crack initiation, crack propagation, strain-hardening, and failure stages. Compared with those of the stiff support, the toughness, deformability and ultimate load of the yielding supports were increased by an average of 225%, 61% and 32%, respectively. Additionally, the PU compressible layer is positioned between two primary linings to allow the yielding support to have greater mechanical properties. The analysis of the synergistic bearing effect suggested that the thickness of PU compressible layer and its location significantly affect the mechanical properties of the yielding supports. The use of yielding supports with a compressible layer positioned between the primary and secondary linings is recommended to mitigate the effects of high geo-stress in squeezing tunnels. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Many soft materials yield under mechanical loading, but how this transition solid -like behavior to liquid -like behavior occurs can vary significantly. Understanding the physics of yielding is of great interest for the behavior of biological, environmental, and industrial materials, including those used as inks in additive manufacturing muds and soils. For some materials, the yielding transition is gradual, while others abruptly. We refer to these behaviors as being ductile and brittle. The key rheological signatures of brittle yielding include a stress overshoot in steady -shear -startup tests a steep increase in the loss modulus during oscillatory amplitude sweeps. In this work, we show how this spectrum of yielding behaviors may be accounted for in a continuum model for yield stress materials by introducing a parameter we call the brittility factor. Physically, an increased brittility decreases the contribution of recoverable deformation to plastic deformation, which impacts the rate at which yielding occurs. The model predictions are successfully compared to results of different rheological protocols a number of real yield stress fluids with different microstructures, indicating the general applicability of the phenomenon of brittility. Our study shows that the brittility soft materials plays a critical role in determining the rate of the yielding transition provides a simple tool for understanding its effects under various loading conditions.

Assessing foundation response to cyclic loading is vital when designing transport infrastructure, such as road pavements and rail tracks, as well as offshore, port, and tall tower structures. While detailed guidance is available on characterizing many soil types' cyclic behavior, relatively few studies have been reported on stiff, geologically aged, plastic clays. This paper addresses this gap in knowledge by reporting cyclic loading experiments on three natural stiff UK clays that were deposited and buried between the Jurassic Age and Eocene Epoch before geological unloading to their currently heavily over-consolidated states. High-quality samples taken at relatively shallow depths were reconsolidated to nominally in situ K0 stresses in triaxial and hollow cylinder apparatus before imposing cyclic loading. The completely stable, metastable, or unstable outcomes invoked by different levels of undrained cyclic loading are interpreted within a kinematic yielding framework that is compatible with monotonic control experiments' outcomes. The cyclic limits marking the onset of significant changes in permanent strain accumulation, pore pressure development, and stress-strain hysteresis demonstrate that the weathered Gault clay offers the lowest cyclic resistance. The experiments show that energy considerations provide a promising way of evaluating undrained pore pressure generation and stiffness degradation. They also provide a basis for developing cyclic constitutive models and analysis procedures for cyclic foundation design in stiff, high-OCR, plastic clay strata.