Infilled joints or faults are often subjected to long-term stable shear forces, and nature surface processes of normal unloading can change the frictional balance. Therefore, it is essential to study the sliding behavior of such granular materials under such unloading conditions, since they are usually the filling matter. We conducted two groups of normal unloading direct shear tests considering two variables: unloading rate and the magnitude of constant shear force. Dry sands may slide discontinuously during normal unloading, and the slip velocity does not increase uniformly with unloading time. Due to horizontal particle interlacing and normal relaxation, there will be sliding velocity fluctuations and even temporary intermissions. At the stage of sliding acceleration, the normal force decreases with a higher unloading rate and increases with a larger shear force at the same sliding velocity. The normal forces obtained from the tests are less than those calculated by Coulomb's theory in the conventional constant-rate shear test. Under the same unloading rate, the range of apparent friction coefficient variation is narrower under larger shear forces. This study has revealed the movement patterns of natural granular layers and is of enlightening significance in the prevention of corresponding geohazards.

The seismic performance of a long-span triple-tower suspension bridge is a critical consideration in engineering communities. To promote a better seismic design, this paper presents a parametric study on the structural seismic control using hysteretic steel dampers. The finite element model is firstly established, and an introduction to the mechanical properties of the E-shaped hysteretic steel damper is made. Then, a seismic analysis is conducted under uniform earthquake excitations. Considering the effect of wave passage, the performance of hysteretic steel dampers in seismic control is further analyzed. The results indicate that the travelling wave effect greatly affects seismic responses. Increasing the damper elastic stiffness can effectively reduce the relative displacement between the main girder and either the left or the central tower. This treatment is effective for the right tower only when the wave velocity is among 400-1600 m/s, while it makes little contribution in other ranges. At an arbitrary wave velocity, increasing the damper elastic stiffness would cause minor changes to the shear forces of side towers, while its influence on the central tower is significant. A reasonable damper design for the long-span triple-tower suspension bridge depends on an essential prior evaluation of the wave velocity based on soil conditions.

Reynolds number (Re), pore water pressure (P), and water flow shear force (tau) are primary indicators reflecting the characteristics of subsurface flow. Exploring the calculation of these parameters will facilitate the understanding of the hydrodynamic characteristics in different subsurface flows and quantify their differences. Hence, we conducted a study to monitor soil water content, matrix potential, and pore water pressure in two typical soil profiles (with and without fissures). The distribution of Re, P, and tau in both matrix flow (MF) and preferential flow (PF) were calculated with an improved calculation method, focusing on their energy changes. Results showed that these hydrologic parameters are quite different between MF and PF. Re values in MF remained below 0.1, indicating lower water flow velocities, while the Re values ranged from 0.8 to 2 in PF, indicating higher flow velocities. The P values in PF was tens to hundreds of times higher than that in MF, which is mainly due to the rapid accumulation and leakage of water within soil fissures. Additionally, the larger hydraulic radius and gradient in PF also resulted in higher tau values in PF (2 similar to 6 N m(-2)) than in MF (0 similar to 1.5 N m(-2)). In PF, the pressure potential was the significant factor for tau, while tau in MF was dominated by the matrix potential and varies with the magnitude of the matrix potential gradient. This study suggests that Re, P, and tau could be considered as the major indexes to reflect dynamic characteristics of subsurface flow.

Precisely estimating the lateral capacity of the large-diameter monopile is essential for securing the stability of the fixed wind turbine of high power generation. Conventional standards relying on p-y curves often underestimate the monopile-soil interaction due to their failure to account for pile shaft rotations and base effects, leading to overly cautious lateral capacity designs. This paper introduces the three-spring soil reaction model that comprehensively considers lateral soil resistance, shaft frictional resistance, base shear force, and base moment. The analytical expressions for three springs are established considering the self-similarity between soil stress-strain relationships and load-displacement responses. The bearing capacity calculation method of monopiles with varying rigidity is developed based on the combinations of three springs. The results reveal that the modified p-y curve for lateral capacity predictions achieves over 80% accuracy. The contributions of base effects and shaft frictional resistance to bearing capacity gradually increase with the increases in pile rigidity, and the correction of monopile ultimate lateral displacement prediction is also enhanced.