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Recent mounting studies showed that neuroinflammation caused by surgery or anesthesia is closely related to postoperative cognitive dysfunction (POCD). This study investigated the effect of mineralocorticoid receptor (MR) on neuroinflammation and POCD. To detect the MR effect in an animal model, we randomly divided rats into control, anesthesia, and surgery groups. To determine whether the MR-specific blocker eplerenone (EPL) could improve cognitive dysfunction, we assigned other animals into the control, surgery and EPL treatment, and surgery groups. Cognitive function was detected using the Morris water maze. Serum cytokine levels were measured by ELISA, and the histopathological changes of hippocampal neurons were identified by hematoxylin/eosin and Nissl staining. Our research confirmed that anesthesia and surgical stimulation could lead to IL-1β, IL-6, and TNF-α activation and hippocampal neuronal degeneration and pathological damage. MR was upregulated in the hippocampus under cognitive impairment condition. Additionally, EPL could alleviate inflammatory activation and neuronal damage by exerting neuroprotective effects. The preclinical model of sevoflurane anesthesia/splenectomy implied that MR expression is upregulated by regulating the neuroinflammation in the brain under POCD condition. Manipulating the MR expression by EPL could improve the inflammation activation and neuronal damage.

Stability prediction of rock slope under seismic loads is important for landslide hazard assessment. For studying the dynamic response of anti-dip rock slope, one two-dimensional physical model of anti-dip slope containing two groups of rock joints was designed for shaking table test. The influences of different dynamic parameters including wave type, amplitude and frequency on the dynamic response of the slope model were considered. The results of this study reveal that the amplification coefficients of peak ground acceleration increase with increasing the relative elevation. With the increase of acceleration amplitude, the amplification coefficients rise on the whole, but they are influenced by rock structure and wave type. The amplification coefficients increase with the increase of frequency, and they become stronger near the slope top. The influence of frequency is closely related to the acceleration amplitude. The discontinuous deformation analysis method was used to compare the dynamic failure of slope model with shaking table test. Both the results of two methods indicate that the slope model under seismic loads mainly presented that shear cracks and tension cracks extended, connected and developed step-type fractures, the slope experienced toppling and sliding failure. The study has theoretical and practical significance, it can provide guidance for seismic slope engineering.

In this study, shear tests on artificial rock joints with different roughness were conducted under five normal stress levels. Test results showed that the shear strength of rock joints had a positive correlation with roughness and the applied normal stress. Observation of joint specimens after shear tests indicated that asperity damage was mainly located in the steep areas facing the shear direction. The damaged joint surfaces tend to be rough, which implies that tensile failure plays an important role in shear behavior. As a result of the anisotropic characteristic of joint roughness, two quantitative 2D roughness parameters, i.e., the revised root-mean-square of asperity angle tan−1(Z 2r) and the maximum contact coefficient C m, were proposed considering the shear direction. The proposed roughness parameters can capture the difference of roughness in forward and reverse directions along a single joint profile. The normalized tensile strength and the proposed roughness parameters were used to perform a rational derivation of peak dilatancy angle. A negative exponential-type function was found to be appropriate to model the peak dilatancy angle. Using the new model of peak dilatancy angle, we obtained a new criterion for peak shear strength of rock joints. The good agreement between test results and predicted results by the new criterion indicated that the proposed criterion is capable of estimating the peak shear strength of rock joints. Comparisons between the new criterion and published models from available literature revealed that the proposed criterion has a good accuracy for predicting the peak shear strength of joints investigated in this study.

The deformation and failure of rock mass is a process of energy dissipation; the damping of DDA is a very important and basic problem. The correctness and effectiveness of DDA rely on the appropriate values of the numeric controlling parameters like time interval, spring stiffness, and assumed maximum displacement ratio g2, and the contact using the penalty method is the core content of DDA. A mechanical model of two contact blocks loaded with the normal force acting along one side of block boundary is established to study the DDA damping problem, which involves the contact and eliminates the influence of some numeric control parameters (e.g., g2). Based on the Newmark method and the theory of DDA, the motion equations of two-block system can be established, and then the relationship of some numeric control parameters and the influence of damping can be obtained. The algorithmic damping increases with the increasing of time interval. Given a very small time interval, the spring stiffness may have no obvious effect on the algorithmic damping. The numerical results reveal that the essence of time interval influencing the open-close iteration is the fact that the algorithmic damping is mainly controlled by time interval.

This study aims to present a new model for evaluating the peak shear strength of rock joints and investigate the contribution from different shear components to the total shear resistance. Direct shear tests under constant normal load (CNL) conditions were performed on artificial rock joints with different morphology. Before the shear test, a 3D optical scanner was used to measure the joint morphology, and then two statistical parameters were suggested to characterize the joint roughness. For establishing an evaluation model of peak shear strength of rock joints, a model of peak dilatancy angle was first developed and then incorporated into the Maksimovic criterion. A new peak shear strength model for rock joints was thus established, and a good evaluating precision of the new criterion was found by comparing predictive results with experimental results. Three shear strength components, i.e., basic friction, dilation, and shear-off of asperities were investigated. Results show that the basic friction represents over 50 % of the total shear resistance, and this proportion grows steadily by increasing the normal stress. As the normal stress increases, the percentage of shear-off rises gradually before approaching a stable level, whereas dilation consistently decreases. At a certain normal stress level, the basic friction of joints with a lower roughness makes up more of the contribution to the total shear strength, whereas the shear-off component tends to be greater on rougher rock joints. However, the dilation of joints with different roughness does not show an obvious difference in terms of proportion. The apparent cohesion of sheared rock joints increases as the normal stress increases. The rock joint with a rougher surface has a larger apparent cohesion at a certain normal stress level.