A CuO/bentonite composite photocatalyst was prepared to fully utilize the adsorption capacity of bentonite and the photocatalytic activity of CuO. CuO and bentonite were chosen as a photocatalyst due to the excellent optical property of CuO and large specific surface area of bentonite, together with their high stability and low production cost. The sample was characterized by XRD, SEM, and BET. The effects of several factors on degradation process were investigated such as dosage of H₂O₂, irradiation time, pH of the solution, and dosage of catalyst. The optimum conditions for decolorization of methylene blue solution by CuO/bentonite were determined. Under optimal conditions, the decolorization efficiency of methylene blue by a 1.4% CuO/bentonite (400 °C) composite photocatalyst under visible irradiation at 240 min reached 96.98%. The degradation process follow edpseudo-second-order kinetics. The photocatalytic mechanism is discussed in detail. This composite structure provides a new solution to the cycle and aggregation of the photocatalyst in water.

To estimate postgrouting rock mass strength growth is important for engineering design. In this paper, using self‐developed indoor pressure‐grouting devices, 19 groups of test cubic blocks were made of the different water cement ratio grouting into the broken rock of three kinds of particle sizes. The shear strength parameters of each group under different conditions were tested. Then this paper presents a quantitative calculation method for predicting the strength growth of grouted broken rock. Relational equations were developed to investigate the relationship between the growth rates of uniaxial compressive strength (UCS), absolute value of uniaxial tensile strength (AUTS), internal friction angle, and cohesion for post‐ to pregrouting broken rock based on Mohr‐Coulomb strength criterion. From previous test data, the empirical equation between the growth rate of UCS and the ratio of the initial rock mass UCS to the grout concretion UCS has been determined. The equations of the growth rates of the internal friction coefficient and UCS for grouting broken rock with rock mass rating (RMR) and its increment have been established. The calculated results are consistent with the experimental results. These observations are important for engineered design of grouting reinforcement for broken rock mass.

The rock contains many inclusions which produce high locked-in stress under the ground stress. In order to study the influence of locked-in stress on the mechanical properties of rocks, the rock-like materials and nitrile rubber particles are used to make a test block of the rock-like model which contains inclusions. The rubber particles will expand as the test block is heated, which creates locked-in stress in the inclusions. Uniaxial compression tests of similar model blocks with different locked-in stresses and different inclusion contents were performed by using a water bath and MTS-5T uniaxial compression testing machine. The results show that the peak strength and elastic modulus decreased with the increasement of locked-in stress and inclusion content. In the meantime, the relationship among the peak strength, the elastic modulus of the test piece, the locked-in stress and the inclusion content were obtained with the help of a mathematical fitting analysis of the quantitative formula. Furthermore, the expression and value curve of the joint impact factor are calculated. This paper evaluates the importance of the locked-in stress in the mechanical properties of the rock-like material and provide a guide for other researchers to further investigate the locked-in stress in rocks.

Locked-in stress is a special stress objectively existing in the rock which has an important influence on the mechanical properties. However, there were few studies on the locked-in stress in rocks. The locked-in stress was simplified into spherical inclusions of stress. Based on the Eshelby inclusion theory, the influence equation of the locked-in stress on the elastic modulus of the rock is derived. Through experiment, the expression of elastic modulus of rock-like material with locked-in stress based on M-T method is determined. Based on Mohr-Coulomb criterion and effective stress principle, the equations for the influence of locked-in stress on strength of rock-like material under uniaxial and conventional triaxial conditions were deduced. Through experimental verification, an empirical formula for the strength of rock-like material containing locked-in stress is obtained. This article provided a method for further studying of the locked-in stress in rock-like material and has certain reference value.

Incorporating single or mixed types of fibers into concrete is an effective method for enhancing its performance. This study aimed to investigate the optimal fiber mix for hybrid fiber reinforced concrete (HFRC) that includes end-hooked steel fibers (ESF), corrugated steel fibers (CSF), and polypropylene fibers (PF), and to predict its compressive strength. To this end, three combinations of HFRC were designed: ESF and CSF (EC-HFRC), ESF and PF (EP-HFRC), and CSF and PF (CP-HFRC), respectively. Plain concrete and single-fiber reinforced concrete with the same mix proportions were also designed for comparison. The compressive strength test results demonstrate slight to moderate enhancement in the concrete’s compressive strength when hybrid fibers are employed. The hybrid effects observed in both EP-HFRC and CP-HFRC are superior to those of EC-HFRC. The optimal fiber mixing combinations are identified as 0.2% PF combined with 1.5% ESF for EP-HFRC and 0.2% PF along with 1.5% CSF for CP-HFRC. Compared with single steel fiber admixture and no fiber admixture, the mixing of hybrid fibers can significantly impact the failure mode of concrete. A novel mathematical model, based on the theory of composite mechanics, has been proposed to accurately predict the compressive strength of single steel fiber reinforced concrete and EC-HFRC, as evidenced by its close alignment with experimental data. The results of this paper provide substantial theoretical support for the design and optimization of HFRC.