Pervious concrete has been widely used in parking lots and other lightweight streets. Performances of pervious concrete are strongly dependent on its pore structure characteristics. This paper investigates the relationship among porosity, permeability, compressive strength, durability and the pore structure characteristics of pervious concrete. The influences of basalt fiber and fine aggregate on the pervious concrete are also discussed. Pervious concrete specimens with different pore structures were prepared by combining basalt aggregate with size of 5–10 mm and 10–15 mm at different proportion. The pore structure characteristics such as area porosity, pore sizes, and pore distribution of pervious concrete were obtained and analyzed using image analysis method. Experimental results showed that the pore structure characteristics of pervious concrete have effects on its mechanical and durability behaviors. Homogeneous pore distribution and large distances between pores increase the compressive strength and improve freeze–thaw durability of pervious concrete. Due to the difference in the internal pore structure of pervious concretes, specimens with similar volumetric porosities had different permeability coefficients. A series of numerical models were regenerated through a MATLAB code using pore structural parameters derived from the image analysis method, then the numerical models were fed to ANSYS for meshing and further simulation. The comparison of the simulation and experimental results showed close accuracy, which verified the applied simulation analysis method based on image analysis technology.

The shear response of rock joints under bolt reinforcement is important for supporting the design of a jointed rock mass. This paper aims to investigate the shear behavior of bolted rock joints with different roughness. Direct shear tests on both bolted and unbolted artificial joint specimens were conducted under various normal stresses. Before shear tests, three kinds of roughnesses for joints were created by split tests, and the roughnesses were quantitatively evaluated by a three-dimensional morphology scanner. After shear tests, the results showed that the bolt deformation decreased with increasing normal stress and increased with increasing roughness. Furthermore, the shear stiffness of the bolted joint specimens was, without exception, greater than that of unbolted specimens. Compared with those of unbolted specimens, the peak shear strength and the residual shear strength of bolted joint specimens with different roughnesses were improved to different degrees. Using the Coulomb failure criterion to linearly fit the shear strength and the applied normal stress, the equivalent cohesion and friction angle of the bolted joint specimens were found to have evident improvements compared with those of unbolted joint specimens. The increment rate of the equivalent cohesion of the bolted specimens increased with increasing roughness, whereas that of the equivalent friction angle decreased with increasing roughness.

The asperity morphology has profound influences on the failure characteristics and shear strength of rock joints. To investigate these influences, degradation characteristics and mechanical properties were studied based on direct shear tests conducted on six groups of artificial rock joints with regular profiles. For each group of joints, the joint profile consisted of several asperities with a particular amplitude and inclination angle. After completion of shear tests, the degradation of asperities was analyzed and interpreted by the following four types of failure modes: frictional sliding, incomplete shear-off, complete shear-off, and tensile cutoff. The results revealed that in addition to the applied normal stress, both the amplitude and inclination angle had an important influence on the occurrence of the failure modes. Experimental results showed that the peak shear displacements of all joints were far less than the base length of asperities, and the peak shear displacement rate had a mean of 2.04%, indicating that the peak shear strength was mobilized at a very small shear displacement. The peak shear strength and peak friction angle were found to increase with increasing inclination angle in a moderate range up to a certain angle due to sliding and shear failure mechanisms. With further increase of the inclination angle, the asperities tended to failure under tensile mode and resulted in a decreasing trend of both the shear strength and peak friction angle. Experimental results showed that the amplitude had a positive correlation with the strength of rock joints. An existing theoretical model was extended to explain the mechanism behind the aforementioned phenomena observed through laboratory experiments. The results of this study are beneficial for understanding the shear mechanism and the importance of considering both the inclination angle and amplitude in the mechanical behavior of rock joints.