The Impact Responses of a Pervious Concrete Wall with a Sand Cushion against Rockfall: A Full-Scale Experimental Study

The Zhala hydropower station plant was under the threat of rockfalls induced from a high slope, especially in rainy seasons. This paper proposes an innovative protection structure consisting of a pervious concrete wall and a sand cushion to protect against rockfall impact as well as discharge surface runoff. Laboratory test results show that the peak impact force of the rockfall decreases with decreasing rockfall mass and impact velocity, together with increasing cushion thickness and rockfall sphericity. The most sensitive factor influencing the peak impact force is rockfall sphericity, followed by impact velocity, rockfall mass, and cushion thickness. Based on the sensitivity of influencing factors, a method of calculating the rockfall peak impact force was established by dimensional analysis. Furthermore, a full-scale test was conducted to investigate the feasibility of this structure; test results indicate that an increased rockfall mass results in increased peak impact force, impact stress, and displacement of the pervious concrete wall. By placing a sand cushion in front of the pervious concrete wall, the peak impact force of rockfall and the maximum displacement of the wall are decreased by 70% and 65%, respectively. Meanwhile, the proposed calculation method has good reliability for evaluating the practical rockfall impact force, compared with four classical calculation methods. After the buffering effect of the sand cushion, the impact stress distribution on the pervious concrete wall can be characterized as a bell shape, with high magnitude at the impact point and low magnitude on the sides.