In many underground rock projects, rock masses are subjected to coupled static–cyclic dynamic loading. In this paper, dynamic tests were carried out on granite specimens using a modified split Hopkinson pressure bar to study the dynamic characteristics and energy evolution of the rock under coupled static–cyclic impact loading. The results show that both the dynamic characteristics and the energy evolution of granite are sensitive to the number of repeated impacts and the confining pressure. Under the same confining pressure, the dynamic increase factor (DIF), dynamic elastic modulus, and transmitted energy ratio decreases, while the cumulative dissipated energy, cumulative specific energy dissipation and dissipated energy density tend to increase as more impact cycles are applied. The effect of confining pressure on enhancing the mechanical property of the rock is pronounced: the peak stress of rocks under confining pressure during cyclic impact is higher than their quasi-static compressive strength, and the DIF increase as the confining pressure increases. However, its effect on the dynamic elastic modulus is fairly insignificant. The confining pressure could change the crack propagation path of the specimens, and the failure mode is mainly a tensile failure, with no obvious axial splitting. By increasing the confining pressure, the energy dissipation capacity of the rock is significantly improved, and its increased rate of internal damage could be slowed down. Graphical

Based on the TBM tunnel of Red Line of Tel Aviv in Israel, this paper carried out laboratory tests of shield cutting concrete and reinforced concrete piles and investigated cutting performance of cutter, failure model of rebars, length of damaged rebars, and cutter vibration. The results indicate that under the condition of low tunneling speed and rotating speed, vibration of the cutterhead is small, and vibration of the center cutterhead is more obvious in the radial direction of the cutterhead. Cross sections of broken rebars mainly consist of shear section, tensile‐shear section, tensile‐compressive section, and bending section. Considering the tunnel status, it is recommended to adopt excavation speed of 3∼5 mm/min, and rotating speed of 1.0∼1.3 r/min. While cutting RC piles, the principle of “low excavation speed, high rotating speed, and less disturbance” is recommended. Cutting with disc cutters is efficient and the torque of which is stable but the length of the rebars got from cutting varies a lot. It is recommended that majorities of the cutters shall be disc cutters and supplemented with drag bits and tear cutters.

Y-shaped piles are a new type of pile whose cross-section is like the letter Y: they are often used in ground improvement for road or train subgrades in the eastern coastal region of China. To investigate the bearing behaviour of Y-shaped piles in saturated sand, a series of model tests under compressive and horizontal load for Y-shaped piles, circular pile (the same cross-sectional area of Y-shaped pile), and circular pile (the same perimeter of Y-shaped pile) were carried out. Comparative analysis was conducted on bearing capacity, axial force and side resistance distribution, load sharing ratio, bending moment, and lateral soil pressure distribution along the embedded length. The results show that the bearing capacity of a Y-shaped pile does not increase in proportion, and the shaft resistance is weakened to some extent in saturated sand; Y-shaped pile can effectively improve the compressive bearing capacity for the same amount of concrete. The lateral bearing capacity of a Y-shaped pile has directionality, and hanging a circular section into a Y-shaped section may improve the horizontal bearing capacity for the same amount concrete, but cannot give full play to the advantage of the larger side area for horizontal bearing capacity in saturated sand.

Understanding the internal force distribution and prejudging the weak part of tunnel supporting structure under complicated construction surroundings have become one of the important measures to ensure the safety of tunnel construction. Based on the initial parameter method and field‐monitoring results of surrounding rock pressure, the theory of beam on elastic foundation is employed to derive the analytical solution of primary support internal forces. By combining the monitored data of rock pressure in one tunnel, solution of primary support internal force of a section is back analyzed and weak parts of the primary support are analyzed and evaluated. The results show that, after the tunnel excavation is completed, the internal forces of the primary support of the tunnel arch grow larger over time. When θ > 1.0, the internal forces change greatly. The internal force of the primary support decreased to different extents within 2 days after the primary support was applied and then gradually increased over time. Considering the situationality and changeability of the tunnel construction process, the analytical solution for the primary support internal forces of a multicenter arch tunnel proposed in this paper has a strong feasibility in tunnel construction. The conclusions obtained here could provide theoretical support for the design of supporting structure and the optimization of tunnel construction technology.

To study the cracking process of the wall caused by differential settlement under a uniformly distributed load on the top of the wall, a laboratory model experiment was carried out on large‐scale masonry specimens, and the acoustic emission (AE) technique and digital close‐range industrial photogrammetry were adopted to monitor the AE signals and displacement characteristics of the masonry specimens during loading in real time. The results show that, in the case of differential settlement with small settlement on both sides and large settlement in the middle, two main cracks appear on the left and right sides of the wall, extending obliquely from bottom to top. During the loading process, damage of the wall is aggravated due to the differential settlement, and both cumulative ringing count and energy count have different periods of steep rise. With the increase in the load and activation of the AE event, the AE event becomes active, and the cumulative ringing count and cumulative energy curve have an obvious turning point, where the slope of the curve is substantially higher than that before the turning point. By using digital close‐range industrial photogrammetry, it is observed that the main oblique crack on the left is mainly caused by the difference in the vertical deformation, while the main oblique crack on the right is caused by different displacements and deformation directions of the wall on both sides of the crack.