This study tests the physical and mechanical properties of fresh bamboo to explore its suitability for reinforcing the embankment of a highway. A series of experiments is performed using a bamboo species (Sinocalamus affinis) and soil specimens with bamboo grids that are similar to geogrids. The testing indexes include the natural density, water content, wall thickness, and the outer perimeter of bamboo culm. The mechanical property tests include a uniaxial compression test on bamboo culm, tensile and flexural tests on bamboo strips, a friction test on the bamboo–soil interface, a pullout test on a single bamboo strip in a soil specimen, and a triaxial compression test on a soil specimen with a bamboo grid. The results show that the density and water content of fresh bamboo become relatively stable after growing for 2 years and the bamboo strips can satisfy the specification requirement for a traditional geogrid because of their excellent mechanical properties. Based on the physical and mechanical test results, appropriate cutting age of fresh bamboo is 2 years and more. In addition, the compressive strength for bamboo grid–reinforced soil is significantly greater than that of prime soil, and could effectively prevent filling embankments from settling. In addition, its increased shear resistance could suppress a slip shear failure in the filling embankment.

Vugs and fractures are the main channels within porous rock aquifers and play a dominant role in the water inrush of the karst tunnel. In this paper, a mathematical model of the coupled free-fluid seepage-fluid with second-order accuracy was established to analyze the flow field characteristics of vuggy and fractured porous rock aquifers. The Navier–Stokes equation was used to govern the free fluid flow in vugs and fractures, while the Darcy–Brinkman equation was employed to describe the seepage fluid motion in the porous rock matrix. The analytical solutions for the flow velocity and water discharge were derived under the requirement of continuous velocity and shear stress at the interface between free and seepage fluids. These solutions can be successfully reduced to those of the classical Poiseuille’s law, assuming that the rock matrix is impervious to water. The numerical, experimental, and analytical results were compared to validate the present analytical model, and the results of the analytical model showed greater accuracy compared with the classical Poiseuille’s law and cubic law. Furthermore, the water inrush of the Xiangpingshan karst tunnel was selected as a real engineering case. Perforated bricks were used to stack a vuggy and fractured porous physical tunnel model (1:100) with the same hydraulic conductivity as the Xiangpingshan tunnel. The relative errors between current theoretical and physical tests obtained for the water inflow discharges are within 18%. The current model can provide a reference for predicting the water inflow of karst tunnels in vuggy and fractured porous rock aquifers.