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The combined effect of stress and seepage is an important reason of engineering geological problems such as landslides, dam failures, and tunnel collapse. However, due to the limitations of the test apparatus, the existing studies rarely consider the stress effect in the seepage process. In this study, a soil column apparatus based on the wetting front advancing method was developed to explore the permeability properties of intensely weathered sandstone in a wide range of suction (10~106 kPa). The results suggest that the wetting front advancing velocity decreased as the vertical stress increased during infiltration, which indicates that the stress changes the infiltration channel and affects the infiltration rate. On the other hand, due to the water sensitivity of intensely weathered sandstone, the soil column deformation before and after wetting is significantly different, indicating that water infiltration further exacerbates the deformation. When vertical stress is applied to the soil column, the permeability coefficient-suction curves at different sections are paralleled in general, which is affected by the variation in dry density and the non-uniform distribution of stresses inside the soil column. Moreover, as the initial dry density increases, the influence of the vertical stress on the permeability coefficient gradually decreases. Key words: unsaturated soils, stress, permeability, hydro-mechanical coupling, wetting front, Introduction In mountainous areas with complex geological conditions, tunnel construction inevitably passes through extremely soft rocks, which are composed of soil formed by the weathering and decomposition of clastic rocks, [...]

Pore water chemistry can exert significant controls over the chemo-mechanical behavior of chemically active soils, which has not been characterized by using the traditional Terzaghi's effective stress to a satisfactory extent. In this paper, based on the concept of intergranular stress, a generalized effective stress for saturated active soils is reconceptualized and incorporated into the framework of the modified Cam–Clay (MCC) model to describe the mechanical response of soils upon complex chemical and mechanical loadings. The proposed model is capable of capturing very well the diverse features of the chemo-behavior of saturated active soils, while inheriting all the advantages of the MCC model, by introducing only one additional parameter. Within this context, a simple equation is derived to predict the development of swelling pressure with the variation of pore water chemistry. It is shown that the proposed swelling-pressure equation predicts very well the development of swelling pressure for expansive soils with a dilute pore solution, though discrepancy appears at high concentration. Because the double layer of clay particles is severely suppressed at high salt concentration, the microfabric of soil can be significantly changed, pointing to the importance of taking into account the effect of soil fabric in the constitutive modeling of active soils with high pore water concentration. [ABSTRACT FROM AUTHOR]

The hydro-mechanical behaviour of unsaturated soils is often highly influenced by the microstructure; therefore, it can be beneficial to consider the effect of microstructure in a hydro-mechanical constitutive model. This paper considers the use of a microstructure-related model that adopts the effective degree of saturation as a microstructural index. The model can be used to reproduce the hydro-mechanical behaviour while the effect of the microstructure is considered. For comparison, a non-microstructuredependent model is also employed. The models are applied to simulate the behaviour of two different soilsand a comparison of the models’ performance in simulating triaxial test behaviour is made. Based on the comparison with experimental results and the non-microstructure-dependent model, it can be concluded thatthe adoption of the effective degree of saturation is beneficial to studying the hydro-mechanical behaviour of unsaturated soils affected by the microstructure.

In actual work, the system parameters of the robot joints will change in real time or cannot be measured, and the coupling relationship between the various subsystems and the existence of modeling errors make the system model difficult to determine. Based on such problems, a neural network observation is proposed Decentralized control method for robot joints of the robot. In the actual control of the manipulator, firstly, the model of each joint subsystem is established by the decentralized control theory, and the nonlinear function approximation ability of the neural network is used to approach the uncertain part of the manipulator subsystem online through input and output data. The design observer can estimate the state of the system, and use the estimated state to design a sliding mode controller to dynamically estimate and compensate the unknown model dynamics of each independent joint, and realize the self-control of the system when the speed information and model information are unknown. Adaptive control greatly enhances the robustness and adaptability of the robotic arm system. Finally, the stability criterion of the neural network observer and the sliding mode controller is given by the Lyapunov function method, and the simulation results prove the effectiveness of the design method.

Cell migration is a pivotal step in metastatic process, which requires cancer cells to navigate a complex spatially‐confined environment, including tracks within blood vessels and in the vasculature of target organs. Here it is shown that during spatially‐confined migration, the expression of insulin‐like growth factor‐binding protein 1 (IGFBP1) is upregulated in tumor cells. Secreted IGFBP1 inhibits AKT1‐mediated phosphorylation of mitochondrial superoxide dismutase (SOD2) serine (S) 27 and enhances SOD2 activity. Enhanced SOD2 attenuates mitochondrial reactive oxygen species (ROS) accumulation in confined cells, which supports tumor cell survival in blood vessels of lung tissues, thereby accelerating tumor metastasis in mice. The levels of blood IGFBP1 correlate with metastatic recurrence of lung cancer patients. This finding reveals a unique mechanism by which IGFBP1 sustains cell survival during confined migration by enhancing mitochondrial ROS detoxification, thereby promoting tumor metastasis. [ABSTRACT FROM AUTHOR]

This article presents a bounding surface model for unsaturated soils by using skeleton stress and bonding variable based on microcosmic pore structure as constitutive variables. A Hydraulic hysteresis soil-water characteristic curve model considering deformation and hydraulic hysteresis is combined to achieve hydraulic coupling. The proposed model can capture the change of the inter-particles bonding effect in the deformation process of unsaturated soils and accurately predict the hydraulic mechanical behavior of unsaturated soils under complicated loading paths and wetting-drying cycles. The validity of the proposed model is confirmed by the results of unsaturated isotropic compression tests, wetting-drying cycles tests and unsaturated triaxial shear tests reported in the literature.

This study proposes an approach to simulate the effects of initial density on the relative coefficient of permeability for unsaturated soils. The density-dependent permeability function is derived based on (i) an incremental relationship between the degree of saturation and the initial void ratio with various suctions and (ii) the relationship between the permeability function and the soil-water retention curve (SWRC). Only one additional parameter is required in the proposed function, which can be calibrated using a conventional SWRC test. A number of test results in the literature are employed to validate the proposed density-dependent permeability function, and the model predictions indicate good agreement with the experimental data in the literature. Key words: unsaturated soil, soil-water retention curve, permeability function, initial density. Cette etude propose une approche pour simuler les effets de la densite initiale sur le coefficient relatif de permeabilite pour les sols non satures. La fonction de permeabilite dependante de la densite est derivee a partir de (i) une relation incrementale entre le degre de saturation et l'indice des vides initial a diverses succions, et (ii) la relation entre la fonction de permeabilite et la courbe de retention d'eau (CRE). Un seul parametre additionnel est necessaire dans la fonction proposee, qui peut etre calibre avec un essai de CRE conventionnel. Plusieurs resultats d'essais provenant de la litterature ont ete utilises pour valider la fonction de permeabilite dependante de la densite proposee, et les predictions du modele indiquent une bonne correspondance avec les donnees experimentales de la litterature. [Traduit par la Redaction] Mots-cles: sol non sature, courbe de retention d'eau du sol, fonction de permeabilite, densite initiale., Introduction The coefficient of permeability (or hydraulic conductivity) is one of the inevitable parameters to determine the hydraulic property of soils. For a soil, the coefficient of permeability (k) is [...]