Rock microstructure changes after hydrochemical reactions, which, in turn, leads to deterioration of mechanical properties. Thus, a quantification study on rock microstructural damage after chemical corrosion is necessary. Quantification of the microstructural damage of rocks after chemical corrosion was carried out in this study. We presented a proposal that included formulae for calculating the damage variable by analyzing the porosity changes of sandstone. The plastic deformation of sandstone specimens after soaking in chemical solution was observed. Plastic deformation can be divided into distinct stages over time. Results showed that the prepeak incremental deformation after chemical corrosion was partially due to the increase in plastic deformation before reaching the peak and to the deformation caused by pore compression. Plastic deformation is an indirect indicator of the degree of chemical corrosion of sandstone specimens. After chemical corrosion, the porosity of sandstone specimens changed consistently with the velocity of longitudinal wave. Therefore, the calculation formula of the damage variable can be used to calculate the porosity of sandstone specimens at different time periods. The chemical damage of sandstone specimens was highly consistent with the peak strain. Therefore, the damage variable based on porosity can be used to quantitatively describe the damage caused by chemical corrosion.

Concrete will deteriorate and damage under sulfate attack.In order to study the degradation characteristics of HDC under sulfate attack, the mechanical properties of high-ductility concrete (HDC) were investigated using the uniaxial compressive strength test of HDC specimens soaked in different concentrations of sulfate solution and subjected to different times of dry–wet cycles. The variations in the compressive strength, loss rate of compressive strength, and the max compressive strength under the action of sulfate attack and dry–wet cycles were analyzed. The analytical expressions of damage variables were given. SEM was used to observe the microstructure of the sample, and the microdamage mechanism of the HDC was explored. The deterioration of the HDC was found to be the result of the combined action of sulfate attack and dry–wet cycles and was caused by physical attack and chemical attack. PVA prevented the rapid development of deterioration. On the basis of the change of compressive strength, the damage variable was established to quantitatively describe the degree of damage to HDC. The experimental results showed that with the increase in the number of dry–wet cycles, the compressive strength of HDC generally increased first and then decreased. As the concentration of the sulfate solution increased, the loss rate of the compressive strength of HDC generally increased and the max compressive strength gradually decreased. With the increase inthe number of dry–wet cycles, HDC first showed self-compacting characteristics and then gradually became destroyed. Compared with ordinary concrete (OC), HDC is superior to OC in sulfate resistance and dry–wet cycles. This study provided a test basis for the engineering application of HDC in sulfate attack and dry–wet cycles environment.

Long-term immersion was adopted to explore the damage deterioration and mechanical properties of granite under different chemical solutions. Here, granite was selected as the candidate of parent rocks for nuclear waste storage. The physical and mechanical properties of variation regularity immersed in various chemical solutions were analyzed. Meanwhile, the damage variable based on the variation in porosity was used in the quantitative analysis of chemical damage deterioration degree. Experimental results show that granite has a significant weakening tendency after chemical corrosion. The fracture toughnessKIC, splitting tensile strength, and compressive strength all demonstrate the same deteriorating trend with chemical corrosion time. However, a difference exists in the deterioration degree of the mechanical parameters; that is, the deterioration degree of fracture toughnessKICis the greatest followed by those of splitting tensile strength and compressive strength, which are relatively smaller. Strong acid solutions may aggravate chemical damage deterioration in granite. By contrast, strong alkaline solutions have a certain inhibiting effect on chemical damage deterioration. The chemical solutions that feature various compositions may have different effects on chemical damage degree; that is,SO42-ions have a greater effect on the chemical damage in granite thanHCO3-ions.

The tangential contact stiffness of cylindrical asperities is investigated using macro- and micro-mechanisms in this study. A microanalysis model is developed and the tangential contact stiffness of elliptically parabolic asperities on the contact surface is determined. The shape influence coefficient of the cylindrical contact is defined, and its rationality is evaluated. The influence of asperity distribution on the rough surface is determined, and the tangential contact stiffness macroanalysis model is constructed based on fractal theory. The mathematical expression to determine the tangential contact stiffness of the macroscopically cylindrical contact is generated, and the effects of influential factors on tangential contact stiffness are explicitly evaluated. Numerical results show that the tangential contact stiffness of asperities is determined by several factors, such as material properties, applied loads, fractal dimension, and surface shape.

Uniaxial tensile tests of basalt fiber/epoxy (BF/EP) composite material with four different fiber orientations were conducted under four different fiber volume fractions, and the variations of BF/EP composite material failure modes and tensile mechanical properties were analyzed. The results show that when the fiber volume fraction is constant, the tensile strength, elastic modulus, and limiting strain of BF/EP composite material all decrease with increasing fiber orientation angle. When the fiber orientation angle is constant, the tensile strength, elastic modulus, and limiting strain of BF/EP composite material all increase with increasing fiber volume fraction. A certain degree of fiber clustering appears in the epoxy resin when the basalt fiber volume fraction is >1.2%. The fiber equidistribution coefficient and clustering fiber content were used to characterize the basalt fiber clustering effect. With the increase of fiber volume fraction, the clustering fiber content gradually increased, but the fiber equidistribution coefficient decreased. Meanwhile, based on Tsai theory, a geometric model and a tensile mechanical model of the clustering fiber are established. By considering the fiber clustering effect, the BF/EP composite material tensile strength is calculated, and the calculated values are close to the experimental results.