The static and dynamic compression mechanical properties of the prefabricated artificial filled rock joints specimens with different fillings and different joint thicknesses are tested, respectively. Then, the strength, deformation, wave propagation and energy dissipation laws of the filled joints are analyzed. The experimental results show that the static and dynamic compression strength of filled joints increases with the strength of filling materials while decreases with the filling thickness. The deformation characteristics of filled joints under static and dynamic compression are positively correlated with the properties of filling materials and the thickness of filled joints. With the increasing of the filling thickness, the reflection coefficient increases while the transmission coefficient decreases. With the increase of the strength of the fillings, the reflection coefficient decreases while the transmission coefficient increases. The energy dissipation ratio decreases with the increase of the filliing thickness and increases with the increase of the strength of the filling material.

Geo-materials may present varying mechanical properties under different stress paths, especially for tunnel excavation, which is typically characterized by the decreased radial stress and increased axial stress during the complex loading and unloading process. This study carried out a comparative analysis between the loading and unloading model testing, which was then combined with PFC^2D simulation, aiming to reveal the fracture propagation pattern, microscopic stress and force chain distribution of the rock mass surrounding the tunnel. Comparisons of extents and development of tensile strain between loading and unloading testing results were made. The overall stability, the integrity of rock mass, and the failure pattern transition under loading and unloading processes were systematically examined. In addition, for the two unloading cases with different vertical stresses imposed, the failure patterns were both identified as the collapse of the V − shaped extruded sidewall, due to the coupling of the shear failure and the vertical tensile failure in the sidewall wedge.

Rock-socketed pile is widely used in coastal wharf, Marine bridge, and Marine power engineering, and the end bearing function is considered more in the design process. However, the lateral friction resistance of rock-socketed piles is an important bearing part, and the load transfer mechanism of the pile–soft rock interface is an important research focus. In this paper, a comparative analysis was adopted in the test, and ten groups of test specimens were made, including five groups of natural and saturated mudstone specimens, respectively. The characteristics of interfacial load transfer were analyzed through the shear test of a pile–mudstone interface. A calculation model for the vertical bearing capacity of rock-socketed piles based on the softening of lateral friction resistance was established, and the effects of interface relative displacement, lateral positive pressure, pile length, and pile stiffness on the vertical bearing capacity of rock-socketed piles were analyzed. The results show that the shear strength of the pile–rock interface is lower than that of the mudstone interface, and the interfacial shear strength shows the characteristics of “first increasing, then decreasing, and finally flattening with the increase of shear displacement”. The vertical ultimate bearing capacity and residual bearing capacity under saturation were 89.49% and 89.73% of the natural state, respectively. With the increase of pile side pressure, the proportion of pile side friction resistance increased by 39.96%, and the pile side friction resistance was fully exerted. With the increase of pile length, the vertical ultimate bearing capacity of pile foundation increased, and the residual bearing capacity change value increased from 6.80% to 16.97%. However, the increase in pile stiffness had little effect on the vertical bearing capacity. The calculation model can provide a certain reference for the design and calculation of rock-socketed piles in soft rock areas.

Rock-socketed concrete-filled steel tube piles (RSCFSTs), which have been widely used in harbors, bridges, and offshore wind turbines, were exposed to horizontal cyclic loading during service and suffered fatigue damage. For the RSCFSTs, longitudinal steel bars were welded to the inner wall of the steel tube to enhance the bonding strength of the steel tube and concrete core interface. It is essential to research the bearing performance of RSCFSTs like this, under horizontal cyclic loading. In this paper, cyclic loading tests of RSCFSTs under horizontal loading were carried out. The failure patterns of RSCFSTs during the destabilization process were generalized, and the lateral displacement development law of RSCFSTs was analyzed. The interfacial bonding characteristics between the steel tube and concrete core during the test were also discussed. Results showed that the horizontal bearing capacity of RSCFSTs decreases nonlinearly with the increase in the equal amplitude of load, and the development process of the lateral displacement-cycle number curve was divided into three phases: (I) rapid growth period, (II) fatigue growth period, and (III) sharp growth period. The larger the horizontal load was, the faster the lateral displacement entered the fatigue growth period. The duration of the rapid growth period and fatigue damage period accounts for about 90% of the total life of RSCFSTs. The stiffening form of the longitudinal steel bars welded to the inner wall of the steel tube can realize the synergistic force between the upper steel tube and the concrete core of RSCFSTs, which accounts for about 7/10 of the length of RSCFSTs. The depth of the steel tube, foundation stiffness, and bonding performance between the steel tube and the concrete core were the key factors that affected the horizontal bearing performance of RSCFSTs. Finally, some constructive suggestions are proposed for the design of RSCFSTs, including increasing steel tube embedded depth, adding a sniffer bar between the steel tube and concrete interface, etc.

Shaft stability plays an important role in mine safety. Most of the previous studies focused on the stress analysis of shafts using monitoring data. Since the shaft wall state in the deep topsoil stratum is still not clear, the ultimate analysis method is adopted to study the bearing capacity and the strain of a large-diameter shaft wall in Yanzhou coal mine. First, the bearing capacity of the shaft wall is discovered. The value of the auxiliary shaft, main shaft and ventilating shaft is 22.22 MPa, 22.07 MPa and 21.73 MPa, respectively. Then, the ultimate strain of the shaft wall is obtained; the designed ultimate strain corresponding to those shafts is 1.468‰, 1.458‰ and 1.435‰, while the working ultimate strain is 2.078‰, 1.800‰ and 2.638‰, respectively. Since the working values are greater than the design values, the shaft walls need to be reinforced, which is consistent with the field situation. Finally, numerical analysis based on the finite difference method (FDM) is performed to investigate the evolution process of ultimate strain on the shaft wall. The results show the ultimate strain could provide a theoretical basis for safe service and management of a large-diameter shaft in a deep topsoil area.