The prediction of wave transformation and associated hydrodynamics is essential in the design and construction of reef top structures on fringing reefs. To simulate the transformation process with better accuracy and time efficiency, a shock-capturing numerical model based on the extended Boussinesq equations suitable for rapidly varying topography with respect to wave transformation, breaking and runup, is established. A hybrid finite volume–finite difference scheme is used to discretize conservation form of the extended Boussinesq equations. The finite-volume method with a HLL Riemann solver is applied to the flux terms, while finite-difference discretization is applied to the remaining terms. The fourth-order MUSCL (Monotone Upstream-centered Schemes for Conservation Laws) scheme is employed to create interface variables, with in which the van-Leer limiter is adopted to improve computational accuracy on complex topography. Taking advantage of van-Leer limiter, a nested model is used to take account of both computational run time and accuracy. A modified eddy viscosity model is applied to better accommodate wave breaking on steep reef slopes. The established model is validated with laboratory measurements of regular and irregular wave transformation and breaking on steep fringing reefs. Results show the model can provide satisfactory predictions of wave height, mean water level and the generation of higher harmonics.

The process of exchange and transport between salt and fresh water is affected by not only convection due to the density gradient but also turbulence. In this study, a high resolution mathematical model of the intrusion movement of saltwater in an estuary area was established and compared with a physical flume experiment. The model, whose minimum horizontal grid cell of the model is 0.05 m, and minimum vertical grid cell is 0.0005 m, simulated well the salt transport mechanism at the interface between salt and fresh water. The salt transport processes of estuarine saltwater intrusion were obtained under the conditions of no runoff and no tide, no runoff and tide, and runoff and tide. The results suggest that under the joint action of runoff and tide, the mixing process in the interface of salt and fresh water is relatively gentle, the change in the velocity gradient is small, and the advance distance of saltwater intrusion will reach a dynamic equilibrium state after a period of time.

Slip‐lining is a preferred rehabilitation approach in the departments of transportation in China. Although the method is the most common rehabilitation technique, few research studies have been conducted on the mechanical behavior of a rehabilitated reinforced concrete pipe (RCP). A series of experiments were conducted on RCPs rehabilitated with a corrugated steel pipe (CSP), a steel pipe, a high‐density polyethylene (HDPE) pipe, and a shape steel bracket. The RCP rehabilitated with the CSP showed an increase in both the load‐carrying capacity (3.46 times greater than the RCP) and the stiffness (5.35 times greater than the RCP). The RCP rehabilitated with the steel pipe, HDPE pipe, and steel bracket exhibited an increase in the load‐carrying capacity (1.23, 1.50, and 1.31 times greater than the RCP, respectively), and the stiffness of these three pipes was not markedly changed. The slip‐lined pipe acts as a “pipe within a pipe” system. A “load‐sharing” theory was proposed in this study and provides estimates of the load‐carrying capacity of the slip‐lined pipes.