Due to the limitations in construction scope, blasting a medium-section tunnel is challenging as it often results in short circular footage and significant over and under excavation. To reduce costs and increase efficiency, it is essential to focus on long footage excavation and fine control of over and under excavation. In this study, a straight hole cutting blasting scheme was designed for a medium section tunnel project and 40 cycles of blasting excavation field tests were conducted. The results revealed that when designing the long footage blasting parameters for a medium section tunnel based on the blasting design manual, issues such as high block rate and uneven face frequently arise. However, by appropriately increasing the charge of the cut part(the proportion of charge of the cut part increased from 12.8% to 18.1% in our field test), better blasting effects were achieved. Additionally, by reducing the charge amount of peripheral holes and adjusting their distance from each other, smooth blasting effect was effectively ensured. During the field test, adjustments were made to the charge amount of peripheral holes based on preliminary design for blasting parameters. This resulted in good contour forming effects with a half-hole rate exceeding 90%. However, an average overcutting value of 18.6 cm was observed across all 40 excavation sections during the blasting cycle. The main cause for this overcutting was identified as platform irregularities along the contour line. To address this issue, it is necessary not only to reduce external drilling angles but also control platform width alongside reasonable parameter designs for surrounding holes. The straight hole cutting scheme proved compatible with three-arm rock drilling truck construction methods while enabling mechanized long-shot blasting excavations. Nevertheless, precise control over overcutting and undercutting remains challenging along with cost management during blast construction. It is necessary to optimize and improve the operation technology of drilling personnel and the management mode of site construction.

Reinforced concrete (RC) short beam is the key load-bearing component of buildings. In order to study its dynamic response and failure mechanism under impact load, drop hammer impact tests with different impact mass, impact velocity and impact energy were carried out by combining strain gauge sensor, high-speed photography and digital image technology (DIC). The results show that, the failure forms of the short RC beams under impact loads are arch collapse cracks and overall bending deformation, which are obviously different from those of shallow beams. The axial strain in the mid span of a short RC beam changes from tensile strain to compressive strain. With the increase of impact energy (18 061 J≤E≤49 831 J), the axial peak tensile strain and residual compressive strain in the mid span increase first and then decrease. The short RC beam is in the stage of elastic flexural deformation, elastic-plastic flexural deformation and punching shear failure mode in turn. The crack initiation and propagation process of the short RC beam under impact load is not unidirectional. And the fracture zone is formed by the multidirectional fracture propagation with multiple times, and then the plastic hinge is formed, resulting in the overall short beam failure. The deformation degree of the beam mainly depends on the impact speed rather than the impact energy. Specifically, the peak deflection and residual deflection in the middle span of the beam (26.81 mm≤w_p≤29.85 mm;17.12 mm≤w_r≤21.66 mm) increase with the increase of the impact speed (5.53 m/s≤v≤7.13 m/s) under the same impact energy (30 000 J).